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SpaceX Vehicles and Missions => SpaceX Starship Program => Topic started by: Chris Bergin on 03/30/2021 04:28 pm

Title: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Chris Bergin on 03/30/2021 04:28 pm
New thread (20) for discussion of the Starship prototype being built in Boca Chica, Texas.  Previous posts on these prototypes can be found in these threads:

Discussion 1 (https://forum.nasaspaceflight.com/index.php?topic=47184.0)

Discussion 2 (https://forum.nasaspaceflight.com/index.php?topic=48894.0)

Discussion 3 (https://forum.nasaspaceflight.com/index.php?topic=49114.0)

Discussion 4 (https://forum.nasaspaceflight.com/index.php?topic=49602.0)

Discussion 5 (https://forum.nasaspaceflight.com/index.php?topic=49998.0)

Discussion 6 (https://forum.nasaspaceflight.com/index.php?topic=50240.0)

Discussion 7 (https://forum.nasaspaceflight.com/index.php?topic=50453.0)

Discussion 8 (https://forum.nasaspaceflight.com/index.php?topic=50620.0)

Discussion 9 (https://forum.nasaspaceflight.com/index.php?topic=50773.0)

Discussion 10 (https://forum.nasaspaceflight.com/index.php?topic=51290.0)

Discussion 11 (https://forum.nasaspaceflight.com/index.php?topic=51474.0)

Discussion 12 (https://forum.nasaspaceflight.com/index.php?topic=51736.0)

Discussion 13  (https://forum.nasaspaceflight.com/index.php?topic=52205.0)

Discussion 14  (https://forum.nasaspaceflight.com/index.php?topic=52396.0)

Discussion 15  (https://forum.nasaspaceflight.com/index.php?topic=52606.0)

Discussion 16  (https://forum.nasaspaceflight.com/index.php?topic=52701.0)

Discussion 17  (https://forum.nasaspaceflight.com/index.php?topic=52940.0)

Discussion 18  (https://forum.nasaspaceflight.com/index.php?topic=53212.0)

Discussion 19  (https://forum.nasaspaceflight.com/index.php?topic=53361.0)

Thread 20 - you're in it!

UPDATES:

SpaceX BFS : Phase 2 - Starship Orbital Prototype(s) - Photos and Updates -3 (https://forum.nasaspaceflight.com/index.php?topic=51332.0) (Previous)

SpaceX Boca Chica - Production Updates - MASTER Thread (4) (https://forum.nasaspaceflight.com/index.php?topic=52398.0)

Starship SN9 Test Launch - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=52514.0)

Starship SN10 Test Launch - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=52924.0)

Starship SN11 Test Launch - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=53270.0) (New/Current).

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Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 03/30/2021 04:34 pm
I think people are reading too much into Elon's tweet about the crater being in the right place.

Footage from LabPadre and EDA shows an orange glow in the sky, followed by debris falling. No evidence of a fireball on the ground.

Combine that with the sheer size of the debris field (nothing from SN9 travelled nearly as far as SN11 debris went), bits of burned thermal blanket being cared by the wind for miles... it seems unlikely that it hit the ground intact.

The tanks may have been blown to bits in the air but I imagine the engine section with all of its reinforcement continued on a ballistic trajectory (although straight down).  That chunk probably left a nice divot wherever it hit.  Looking forward to some photos when the road reopens (or we get a fly-by).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 03/30/2021 04:35 pm
I think people are reading too much into Elon's tweet about the crater being in the right place.

Footage from LabPadre and EDA shows an orange glow in the sky, followed by debris falling. No evidence of a fireball on the ground.

Combine that with the sheer size of the debris field (nothing from SN9 travelled nearly as far as SN11 debris went), bits of burned thermal blanket being cared by the wind for miles... it seems unlikely that it hit the ground intact.

But eh, some, some of it is on the landing pad, does that count?  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/30/2021 04:36 pm
I think people are reading too much into Elon's tweet about the crater being in the right place.

Footage from LabPadre and EDA shows an orange glow in the sky, followed by debris falling. No evidence of a fireball on the ground.

Combine that with the sheer size of the debris field (nothing from SN9 travelled nearly as far as SN11 debris went), bits of burned thermal blanket being cared by the wind for miles... it seems unlikely that it hit the ground intact.

There’s info in the Updates thread that the FTS was triggered when a second engine failed to ignite for the flip. That makes sense, as the horizontal vehicle, suddenly under thrust, has a rapidly widening IIP radius that will exceed the landing area if it fails to rotate to vertical. That will send debris - including pressurized COPVs, potentially, flying several thousand feet up and around, probably shedding their wrappers, which then drifted on the wind. I will be curious how are metallic or other dense debris fell from the point of breakup.

On another note, watching LabPadre’s feed, there have been several vehicles parked near the pad area for a good while, and a few people mostly standing around the open tailgates and occasionally looking around but not walking very far from them. Anyone want to venture a guess what they’re doing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 04:36 pm
A couple of thoughts.

1. There's now contradicting information coming from an anonymous source at KSC and Elon's tweets.
    a. The KSC source claims FTS was activated because the vehicle went off course but Elon claims "At least the crater is in the right place!" so this is a contradiction.
    b. The KSC source claims that two engines failed to light, but Elon only mentions a single engine with issues "Looks like engine 2 had issues on ascent & didn’t reach operating chamber pressure during landing burn, but, in theory, it wasn’t needed." The note of "in theory, it wasn't needed" implies that the other two engines would have landed successfully.
    c. How do KSC sources already know details of what went wrong when they're nowhere nearby and in NASA, not SpaceX. This seems like very fast communication for government communication.

2. A few people have been making very absolutist statements like "highly evident the vehicle did NOT hit the ground in one piece, it for sure broke up in the air." Not only does this not really contribute to the discussion (no information stating why the person thinks so) but it's also making conclusions that even SpaceX may not obviously know for sure yet. (I was probably guilty of this myself a few times today.) Let's keep discussion high quality.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 03/30/2021 04:36 pm
I interpret Musk's tweet as the FTS enforced "the right place" as intended, so no problems with a crater(s) in "the wrong place".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 04:38 pm
I think people are reading too much into Elon's tweet about the crater being in the right place.

Footage from LabPadre and EDA shows an orange glow in the sky, followed by debris falling. No evidence of a fireball on the ground.

Combine that with the sheer size of the debris field (nothing from SN9 travelled nearly as far as SN11 debris went), bits of burned thermal blanket being cared by the wind for miles... it seems unlikely that it hit the ground intact.

The debris being carried on the wind for miles wouldn't have come from the explosion. Those would have come off at high altitude unless there's a hurricane blowing at the landing site. Those locations are over 5 miles away, for a light but still much heavier than air piece of material. So we shouldn't use those pieces of fabric as evidence of debris field until presented with other evidence (for example if we found debris on the far shore the canal which are slightly heavier than the insulation pieces.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/30/2021 04:38 pm
From my contacts at KSC.
Two engines failed to relight for flip, vehicle was out of proper position for landing, Flight Termination System self activated.

That does make sense.  Clearly, the explosion happened about T+ 5:50.  This is a second or so after the first engine relight.  We know that SpaceX's current profile is to light all 3 for the flip...and shut one down quickly depending on successful relights.  If neither of the remaining 2 engines lit after the first one...a lack of flip is going to put SS in the right place.  Especially with all the new construction around the orbital launch site...best to set of the FTS as high up as possible if there is any chance it would not rud on the pad if just left to fall.

Please don’t post discussion and commentary in the Updates thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 03/30/2021 04:38 pm
Yes, from updates thread:

From my contacts at KSC.
Two engines failed to relight for flip, vehicle was out of proper position for landing, Flight Termination System self activated.

That's great info! With 2 Raptors not starting, that actually moves suspicion from "Raptor qua Raptor" to "Raptor feed system" again.

It also makes sense that with 1/3 thrust the SS was not in the right position to not get FTS'd... beating a dead horse again, but maybe it is time to flip w/ one Raptor at a much higher altitude, shutdown for 2 seconds to let props settle a bit, then light 2 or 3 for a hover slam? Yes, it will take more propellant, roger, but it makes for a much more likely good feed & successful landing start.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben the Space Brit on 03/30/2021 04:39 pm
@mlinder,

In answer to your question about the early propulsion system tests (the 'flying tanks'), I was neither negative nor positive. I had an up-spike in positivity with SN8 and then, with every successive failure, I've become more and more haunted by a fear that SpaceX are going too fast and to ambitiously, driven by Elon's self-belief and vision.

"We'll fix it in a later version" is a common software company mindset but it doesn't work with expensive hardware that may carry expensive payloads. The margin to absorb 'learning experiences' is rapidly contracting as the orbital flight goal quickly approaches without one single unequivocally-successful landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: M.E.T. on 03/30/2021 04:41 pm
@mlinder,

In answer to your question about the early propulsion system tests (the 'flying tanks'), I was neither negative nor positive. I had an up-spike in positivity with SN8 and then, with every successive failure, I've become more and more haunted by a fear that SpaceX are going too fast and to ambitiously, driven by Elon's self-belief and vision.

"We'll fix it in a later version" is a common software company mindset but it doesn't work with expensive hardware that may carry expensive payloads. The margin to absorb 'learning experiences' is rapidly contracting as the orbital flight goal quickly approaches without one single unequivocally-successful landing.

For the umpteenth time, they don’t need a successful landing to make orbit.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 04:45 pm
@mlinder,

In answer to your question about the early propulsion system tests (the 'flying tanks'), I was neither negative nor positive. I had an up-spike in positivity with SN8 and then, with every successive failure, I've become more and more haunted by a fear that SpaceX are going too fast and to ambitiously, driven by Elon's self-belief and vision.

"We'll fix it in a later version" is a common software company mindset but it doesn't work with expensive hardware that may carry expensive payloads. The margin to absorb 'learning experiences' is rapidly contracting as the orbital flight goal quickly approaches without one single unequivocally-successful landing.

IMO We're nowhere close to carrying expensive payloads, either of the hard kind or the squishy kind. So I guess I don't get how that factors into your worries. Perfecting the quality of construction can come after they actually figure out what the design is, which is obviously still in flux. More so I expect they'll do initial launches with Starlink satellites once they feel confident enough to risk their own money before any customers even. NASA doesn't need SpaceX for landing humans on the moon until 2025 at the earliest.

SN8-SN11 illustrated they had a lot of big problems with the existing design and so caused the scrapping of SN12-SN14. SN15 has large changes with new engine designs. BN1 has so many issues they're scrapping it outright apparently without even testing it maybe.

Reaching orbit in July doesn't mean it's ready for payloads either and that doesn't mean it returns successfully either. The first few will probably end up as hypersonic plasma.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Proesterchen on 03/30/2021 04:46 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 03/30/2021 04:49 pm
On another note, watching LabPadre’s feed, there have been several vehicles parked near the pad area for a good while, and a few people mostly standing around the open tailgates and occasionally looking around but not walking very far from them. Anyone want to venture a guess what they’re doing?
They're playing with a drone. Now that the fog has cleared, I assume they're mapping the debris field before clearing the road.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: M.E.T. on 03/30/2021 04:49 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 04:50 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

Given they just switched to a completely new engine design that looks like it shares little with the previous design, I'm not sure we can extrapolate forward on what their production will be based on past history.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Yvung_Schmeat on 03/30/2021 04:50 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.
Second stage? As in starship?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 03/30/2021 04:50 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?
How do you get to "several Raptors a week"? At one a week (a rate they demonstrated last summer) they could have 40 or more stockpiled already.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 03/30/2021 04:52 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.

That raises a question.  Will BN2 have a modified bottom to go on the test stands (which are designed for a Starship aft end not a Superheavy) or will they need to get the table installed on top of the columns at the orbital launch site first?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 03/30/2021 04:54 pm
@mlinder,

In answer to your question about the early propulsion system tests (the 'flying tanks'), I was neither negative nor positive. I had an up-spike in positivity with SN8 and then, with every successive failure, I've become more and more haunted by a fear that SpaceX are going too fast and to ambitiously, driven by Elon's self-belief and vision.

"We'll fix it in a later version" is a common software company mindset but it doesn't work with expensive hardware that may carry expensive payloads. The margin to absorb 'learning experiences' is rapidly contracting as the orbital flight goal quickly approaches without one single unequivocally-successful landing.

This is completely the wrong way to look at these tests. SN8 was a surprise in how well it performed, and besides, there does not seem to be much difference between SN8 - SN11. Why are people surprised at these test articles not landing? As others have said, these are, in a way, flying engine test stands and proof of concept. Obviously the concept works, and the design has not been finalized yet. Claiming success or failure as this point is way too premature. (Not necessarily in terms of time, but in number of tests and objectives met.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 03/30/2021 04:54 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

I'm not worried about how many they can make.

I'm more concerned that they are making ones that light, have the desired amount of thrust when it's wanted and that they don't eat themselves during landing.

It's the first FFSC engine, and its suppose to be reuseable and it's suppose to light horizontal and flip to the vertical.  That's a lot of things going on.

They will get this working in some form, but maybe they need to dial back the expectations with Raptor first.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 03/30/2021 04:57 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.
Second stage? As in starship?

That doesn't makes sense. A booster doesn't go to orbit. Orbit will require a Starship.

As far as Raptor manufacturing? I don't think it will ramp up until they come to a stable version. They are still modifying it. If the new major version that SN15 uses tests out, I can see them starting to ramp up. But I doubt even they know if they are ready to ramp up production until the new version is qualified during flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: eriblo on 03/30/2021 05:00 pm
Once again, the wind at altitude was westerly as seen in the attached 12:00 UTC Brownsville radiosonde (from meteocentre.com (http://meteocentre.com/radiosonde/get_sounding.php?stn=72250&type=rs&yyyy=2021&mm=03&dd=30&run=12&hist=0&show=0&lang=en&area=us)). The radar only shows a low level plume (check the estimated "Echo Tops" of ~10000 ft) that is blown out to sea once it rises.

[EDIT] Corrected wind direction.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben the Space Brit on 03/30/2021 05:00 pm
@mlinder,

In answer to your question about the early propulsion system tests (the 'flying tanks'), I was neither negative nor positive. I had an up-spike in positivity with SN8 and then, with every successive failure, I've become more and more haunted by a fear that SpaceX are going too fast and to ambitiously, driven by Elon's self-belief and vision.

"We'll fix it in a later version" is a common software company mindset but it doesn't work with expensive hardware that may carry expensive payloads. The margin to absorb 'learning experiences' is rapidly contracting as the orbital flight goal quickly approaches without one single unequivocally-successful landing.

For the umpteenth time, they don’t need a successful landing to make orbit.

Yes, they don't. However, it would be nice if they got the vehicle back. You know 'reusable spacecraft' does sort of carry with it the implied precondition that something is got back other than scrap for recycling.

Additionally, if you don't get it right during the relatively low-stress atmospheric flights, the geometrically-greater stresses of a return from orbit make it even less likely to succeed.

All I'm saying (and I'm praying that Elon has said the same thing) is that they need a milestone approach here.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 03/30/2021 05:01 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

I personally saw Raptor SNs under construction at SpaceX Hawthorne in NOVEMBER that were higher than one of the ones that just went up with SN-11 (and that was at Boca in early Feb). Yes, unless they hit some major manufacturing hiccup early this year, they are probably at ~ RN-late 80s or early 90s complete by now. Would not be surprised if there are RN-80s through McGregor already.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 03/30/2021 05:01 pm
I'm not overly concerned that they have crashed four in a row, but I'm very curious as to what caused two engines to fail to relight.  Maybe it is an extension of the problem from SN10 (gas in the line) and hopefully not an extension of the problem from SN9 (engine failure on relight).  One engine failing I can understand but two seems to be unlikely.  Of course, with the changes coming in SN15, maybe the condition that causes this type of failure are not possible in the new design.  I'm sure the engineers are already going over the data to figure it out.  Looking forward to Elon sharing the conclusions with us as he has done after the other flights.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 03/30/2021 05:01 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

I'm not worried about how many they can make.

I'm more concerned that they are making ones that light, have the desired amount of thrust when it's wanted and that they don't eat themselves during landing.

It's the first FFSC engine, and its suppose to be reuseable and it's suppose to light horizontal and flip to the vertical.  That's a lot of things going on.

They will get this working in some form, but maybe they need to dial back the expectations with Raptor first.


Lets wait and see what the improvements are for the next Raptor block when it flies with SN15.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Danderman on 03/30/2021 05:02 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

I'm not worried about how many they can make.

I'm more concerned that they are making ones that light, have the desired amount of thrust when it's wanted and that they don't eat themselves during landing.

It's the first FFSC engine, and its suppose to be reuseable and it's suppose to light horizontal and flip to the vertical.  That's a lot of things going on.

They will get this working in some form, but maybe they need to dial back the expectations with Raptor first.

It’s pretty clear that the length of time before people fly on Starship is going to be much longer than the initial expectations.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 03/30/2021 05:04 pm
Yes, from updates thread:

From my contacts at KSC.
Two engines failed to relight for flip, vehicle was out of proper position for landing, Flight Termination System self activated.

That's great info! With 2 Raptors not starting, that actually moves suspicion from "Raptor qua Raptor" to "Raptor feed system" again.

It also makes sense that with 1/3 thrust the SS was not in the right position to not get FTS'd... beating a dead horse again, but maybe it is time to flip w/ one Raptor at a much higher altitude, shutdown for 2 seconds to let props settle a bit, then light 2 or 3 for a hover slam? Yes, it will take more propellant, roger, but it makes for a much more likely good feed & successful landing start.

Slight nit to pick: if you shut down for 2 sec. You're not settling any propellants. In fact, the vehicle and it's propellants will be in free fall again and essentially weightless (deceleration from air resistance may be negligible when falling feet first) so you're just asking for bubbles at this point.

Not to mention the often quoted Uncontrollable instability in vertical orientation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/30/2021 05:06 pm
So RUD was far above ground ?

Please do not post questions in the Updates thread.’

The vehicle was between several hundred to 2,000m when the RUD occurred, per the call outs in the landing video. The first Raptor ignited and then signal was lost a second or two later.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 05:11 pm
I think people are reading too much into Elon's tweet about the crater being in the right place.

Footage from LabPadre and EDA shows an orange glow in the sky, followed by debris falling. No evidence of a fireball on the ground.

Combine that with the sheer size of the debris field (nothing from SN9 travelled nearly as far as SN11 debris went), bits of burned thermal blanket being cared by the wind for miles... it seems unlikely that it hit the ground intact.

The debris being carried on the wind for miles wouldn't have come from the explosion. Those would have come off at high altitude unless there's a hurricane blowing at the landing site. Those locations are over 5 miles away, for a light but still much heavier than air piece of material. So we shouldn't use those pieces of fabric as evidence of debris field until presented with other evidence (for example if we found debris on the far shore the canal which are slightly heavier than the insulation pieces.)
Once again, the wind at altitude was westerly as seen in the attached 12:00 UTC Brownsville radiosonde (from meteocentre.com (http://meteocentre.com/radiosonde/get_sounding.php?stn=72250&type=rs&yyyy=2021&mm=03&dd=30&run=12&hist=0&show=0&lang=en&area=us)). The radar only shows a low level plume (check the estimated "Echo Tops" of ~10000 ft) that is blown out to sea once it rises.

[EDIT] Corrected wind direction.

Ok, but to what extent are there microclimates in the area? Is Brownsville representative of the weather at Boca Chica? If it was westerly why did you say that the debris would have ended up over the ocean? In either case, in an explosion on/near the ground they simply wouldn't have reached South Padre because they would have immediately slowed and would have fallen to the ground because they have a high surface area to weight ratio. The only thing that makes sense is if they came off at high altitude. Unless you can provide an alternate explanation of how they got there the above chart doesn't really make sense.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: TauriDaedalus on 03/30/2021 05:12 pm
Hi guys,

Have been reading for a while and getting all information from here, so thank you for existing. Great updates on all fronts.

I am no rocket science, but in my opinion I think it is good that we have seen the four failures so far.
Great data that can be used as base since this has not been done before. But also great boxes to check for the prototype.
How far is the safety zone when it crashes and can't land? How far will the debris flow when it explodes in the air?
I hope noone got hurt and not too much damage was done to properties, but since SN11 was an outdated version, this was a good way to say goodbye by testing the FTS.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/30/2021 05:14 pm
Hi guys,

Have been reading for a while and getting all information from here, so thank you for existing. Great updates on all fronts.

I am no rocket science, but in my opinion I think it is good that we have seen the four failures so far.
Great data that can be used as base since this has not been done before. But also great boxes to check for the prototype.
How far is the safety zone when it crashes and can't land? How far will the debris flow when it explodes in the air?
I hope noone got hurt and not too much damage was done to properties, but since SN11 was an outdated version, this was a good way to say goodbye by testing the FTS.
Welcome to the forum! :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 03/30/2021 05:17 pm
As a follow-on to my post in the previous thread on FTS parameters (whether height goes into determining when to destruct), one of my concerns with regards to such a large debris field is they are perilously close to destroying their own propellant farm.

At some point I have to wonder if they need to look at moving the landing pad (if they even can). I doubt enclosing the farm is even a consideration, but perhaps some 'blast shields' should be considered. If the farm goes down, it could delay launches significantly.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 03/30/2021 05:20 pm
Maybe the FTS triggered, maybe not.  We don't know why it went boom when it did, only that it seemed to be about a second after Raptor ignition.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 03/30/2021 05:25 pm
Hi guys,

Have been reading for a while and getting all information from here, so thank you for existing. Great updates on all fronts.

I am no rocket science, but in my opinion I think it is good that we have seen the four failures so far.
Great data that can be used as base since this has not been done before. But also great boxes to check for the prototype.
How far is the safety zone when it crashes and can't land? How far will the debris flow when it explodes in the air?
I hope noone got hurt and not too much damage was done to properties, but since SN11 was an outdated version, this was a good way to say goodbye by testing the FTS.

Welcome!  ;D

This is the exclusion zone below. The debris flow really can range on a vehicle depending on failure, in this case, the field is wide.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 05:29 pm
Hi guys,

Have been reading for a while and getting all information from here, so thank you for existing. Great updates on all fronts.

I am no rocket science, but in my opinion I think it is good that we have seen the four failures so far.
Great data that can be used as base since this has not been done before. But also great boxes to check for the prototype.
How far is the safety zone when it crashes and can't land? How far will the debris flow when it explodes in the air?
I hope noone got hurt and not too much damage was done to properties, but since SN11 was an outdated version, this was a good way to say goodbye by testing the FTS.

Welcome to the forum. I agree on your points on the failures.

And yes no one got hurt. The areas are completely evacuated of people and no debris that came from the explosion got anywhere close to people or non-SpaceX property (well other than the cameras specifically put in harms way).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Low87 on 03/30/2021 05:32 pm
Think positive: With all the fog, there are no explosion pictures, which will prevent several media from reporting another "failure" of SpaceX.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Aaron_Space on 03/30/2021 05:37 pm
Think positive: With all the fog, there are no explosion pictures, which will prevent several media from reporting another "failure" of SpaceX.

WaPo: "For Elon Musk's SpaceX Starship program, more smoke, fire and shrapnel"
Fox Business: "SpaceX Starship debris rains down during botched test flight..."
Detroit Free Press: "Another failure for SpaceX Starship test"

And so on. But yes, they are denied pictures of a fireball this time around.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 03/30/2021 05:39 pm
Will the FAA have a problem with the size of the debris field?

If the FTS was activated, based on previous experience, it caused a greater problem than just allowing a RUD on ground contact.

U P D A T E T H R E A D

to answer, even if a RUD occurred midair, the same result of debris spread likely would’ve occurred.

It’s better to terminate in the air, then let it smash into anything valuable
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ulmo on 03/30/2021 05:41 pm
I was at the edge of the exclusion zone between Hwy 4 and Rio Grand river, and there was no visibility.  The final relight was a Raptor rocket engine relit sound for a fraction of a second, then a crack and immediate BOOM with no following sound whatsoever.  I didn't hear any kind of protracted explosion, nor did I see anything at all.

For reference, two families from Rocket Ranch were on their way to South Padre Island to watch, but the bike rack on the back of the bus of one family broke, so they pulled over to strap it up temporarily.  After they were done, they said there wasn't enough time to go to South Padre Island, so they turned around and went to Massie's Gun Range, got on top of their bus, and their kids and families got to visually see the rocket near and at apogee, as it went up and down from there, with partial cloud obscurement there; they could not see it as it came up from and dropped down to below the cloud layer though.  Apparently, sun views were available further away than where we were close by.  We think there is more sun to the South in Mexico, so likely dozens of thousands or hundreds of thousands of Matamoros or other Mexican people saw it, but we are just guessing.

I was at the launch pad at 4:51AM taking pictures, and at 5AM I saw a blue light in a pickup truck come by me.  I watched to see where they would go, and they turned around at my car, so I ran down and he said to clear out.  I saw people setting up cameras near to LAB's container, so pulled over to say hi, but the truck kept following me as I parked, so I left; there was another blue-lit pickup out there with the camera setup crew.  I saw the hard closure on Hwy 4 at the East edge of Boca Chica Village when I passed it a few minutes later.  Every time I pulled over to take images, the pickup followed me, so I kept going, until I got to my exit.

I am wondering if Mexico is one place to get good images from in the future with foggy takeoffs.

I am very happy that SpaceX achieved the takeoff in fog achievement.  I was very concerned that sun visibility was a requirement for takeoff, and that has been removed as a restriction!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: eriblo on 03/30/2021 05:42 pm
I think people are reading too much into Elon's tweet about the crater being in the right place.

Footage from LabPadre and EDA shows an orange glow in the sky, followed by debris falling. No evidence of a fireball on the ground.

Combine that with the sheer size of the debris field (nothing from SN9 travelled nearly as far as SN11 debris went), bits of burned thermal blanket being cared by the wind for miles... it seems unlikely that it hit the ground intact.

The debris being carried on the wind for miles wouldn't have come from the explosion. Those would have come off at high altitude unless there's a hurricane blowing at the landing site. Those locations are over 5 miles away, for a light but still much heavier than air piece of material. So we shouldn't use those pieces of fabric as evidence of debris field until presented with other evidence (for example if we found debris on the far shore the canal which are slightly heavier than the insulation pieces.)
Once again, the wind at altitude was westerly as seen in the attached 12:00 UTC Brownsville radiosonde (from meteocentre.com (http://meteocentre.com/radiosonde/get_sounding.php?stn=72250&type=rs&yyyy=2021&mm=03&dd=30&run=12&hist=0&show=0&lang=en&area=us)). The radar only shows a low level plume (check the estimated "Echo Tops" of ~10000 ft) that is blown out to sea once it rises.

[EDIT] Corrected wind direction.

Ok, but to what extent are there microclimates in the area? Is Brownsville representative of the weather at Boca Chica? If it was westerly why did you say that the debris would have ended up over the ocean? In either case, in an explosion on/near the ground they simply wouldn't have reached South Padre because they would have immediately slowed and would have fallen to the ground because they have a high surface area to weight ratio. The only thing that makes sense is if they came off at high altitude. Unless you can provide an alternate explanation of how they got there the above chart doesn't really make sense.
Westerly wind: Wind blowing from west (towards east, made the same mistake at first). It is not a perfect measurement (~30 km away and 1 h earlier) but high altitude winds do generally not change that rapidly in space or time so I expect any debris ending up to the north to have stayed below ~3 km.

Previously posted mechanism: Some light debris get caught in the updraft from the explosion and carried up to say 1-2 km altitude and blown north by the low altitude wind. The distance is ~8 km so something with a terminal velocity of 1 m/s (~sheet of paper) could make it there from 800 m above ground in a wind averaging 10 m/s.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 03/30/2021 05:49 pm
It’s pretty clear that the length of time before people fly on Starship is going to be much longer than the initial expectations.

Yep.  Given that SN12-SN14 were scrapped, the original timeline seems to have been even longer than it is now.
It seems Raptor was iterating quickly some time ago, that it takes ~5 months to see that reach the field, and that given reports of focusing on throttle depth is even now being iterated on.  The crew At SpaceX must feel a lot like software engineers do when someone from the field comes to them with a bug that was fixed two quarters ago.  One item to fine-tune might be how much effort is put into optimizing older releases, and that will depend on whether they're still getting new data, or just seeing old failures in new and interesting ways.  I wouldn't expect to receive much clarity on that, except to note Elon's statement that they'll adjust SN15 on the stand if they need to, so SN15 scheduling may be useful in determining what kind of failure this was.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 03/30/2021 06:05 pm
Is that the tank section falling?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocketdog2116 on 03/30/2021 06:07 pm
I haven't seen anyone suggest this but what if the 1st raptor lit ok but then some failure of the 2nd took out one or more of the remaining engines and that's why it triggered the FTS. That way an issue with one engine could describe the actual loss of multiple engines.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/30/2021 06:11 pm
Is that the tank section falling?

It’s just a healthy chunk of debris, I think. The lack of focus makes it look bigger than it probably is.  I mean, it’s not “small” but it doesn’t look anywhere near the size of an entire entire tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 03/30/2021 06:12 pm
Is that the tank section falling?

Skirt section with leg deployed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 03/30/2021 06:13 pm
Is that the tank section falling?

Skirt section with leg deployed.
At least they deployed this time?  ::)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 03/30/2021 06:27 pm
Is that the tank section falling?

Skirt section with leg deployed.
At least they deployed this time?  ::)
In the SpaceX feed it looked to me like the legs were "pre-deployed" in flight. Anyone else think that?

Edit: I mean, down and locked - on purpose, apparently.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Aaron_Space on 03/30/2021 06:29 pm
I think John Insprucker had the best summary of today's events: "Looks like we've had another exciting test of Starship!"
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Aaron_Space on 03/30/2021 06:31 pm
Is that the tank section falling?

Skirt section with leg deployed.
At least they deployed this time?  ::)
In the SpaceX feed it looked to me like the legs were "pre-deployed" in flight. Anyone else think that?

Edit: I mean, down and locked - on purpose, apparently.

I just looked at the frozen picture from T+ 05:49 again and they are still folded up inside the skirt.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FinalFrontier on 03/30/2021 06:39 pm
My thoughts on today.
1. Raptor continues to be an uphill struggle. Lots of variation in performance from one engine to the next to the next and in QC/QA in terms of parts differences in the manufacturing process. Not unexpected the engine was always going to be the hardest part of any launch architecture like this one.
2. As far as the failure. Probably automatic FTS activation as a result of vehicle off course due to the bad engine (2) not igniting.
The other possibility is that that engine failed destructively and energetically enough to rupture the aft dome during its relight attempt, but given the large size of the debris cloud and many small pieces I think this is not as likely. Probably FTS working as designed here.

Proximate cause is most likely engine malfunctions/failure with engine 2 since it was not making it during ascent anyway.
Raptor is a hard engine. But then again BO had many struggles (and still does) with the BE4 so it's fair to say any large methane burning staged combustion engine is going to be a struggle.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 03/30/2021 06:40 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

I'm not worried about how many they can make.

I'm more concerned that they are making ones that light, have the desired amount of thrust when it's wanted and that they don't eat themselves during landing.

It's the first FFSC engine, and its suppose to be reuseable and it's suppose to light horizontal and flip to the vertical.  That's a lot of things going on.

They will get this working in some form, but maybe they need to dial back the expectations with Raptor first.

It’s pretty clear that the length of time before people fly on Starship is going to be much longer than the initial expectations.
Disagree. It’s going to be in line with EXPECTATIONS, but not in line with HOPES.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 06:48 pm
Once again, the wind at altitude was westerly as seen in the attached 12:00 UTC Brownsville radiosonde (from meteocentre.com (http://meteocentre.com/radiosonde/get_sounding.php?stn=72250&type=rs&yyyy=2021&mm=03&dd=30&run=12&hist=0&show=0&lang=en&area=us)). The radar only shows a low level plume (check the estimated "Echo Tops" of ~10000 ft) that is blown out to sea once it rises.

[EDIT] Corrected wind direction.

Ok, but to what extent are there microclimates in the area? Is Brownsville representative of the weather at Boca Chica? If it was westerly why did you say that the debris would have ended up over the ocean? In either case, in an explosion on/near the ground they simply wouldn't have reached South Padre because they would have immediately slowed and would have fallen to the ground because they have a high surface area to weight ratio. The only thing that makes sense is if they came off at high altitude. Unless you can provide an alternate explanation of how they got there the above chart doesn't really make sense.
Westerly wind: Wind blowing from west (towards east, made the same mistake at first). It is not a perfect measurement (~30 km away and 1 h earlier) but high altitude winds do generally not change that rapidly in space or time so I expect any debris ending up to the north to have stayed below ~3 km.

Previously posted mechanism: Some light debris get caught in the updraft from the explosion and carried up to say 1-2 km altitude and blown north by the low altitude wind. The distance is ~8 km so something with a terminal velocity of 1 m/s (~sheet of paper) could make it there from 800 m above ground in a wind averaging 10 m/s.

That's possible, but I still have issues with that mechanism. Those found objects are light but they don't look featherweight. I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

Edit: Chris (and other mods), please don't edit my post and delete the entire context of the conversation. If you're going to clean it up, at least leave some of the context as otherwise it's not at all clear what the heck I'm talking about. I've added back part of it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 03/30/2021 06:52 pm
On the SpaceX stream I noticed something falling off at a relatively high altitude.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/30/2021 06:58 pm
I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

The NWS radar image posted elsewhere shows the hot water vapor produced by combustion traveled much further than a a few hundred meters. Light fragments of COPV overwrap, Mylar film, etc. could easy be tossed much, much higher than a couple hundred meters by the detonation itself, then carried aloft further by updrafts and prevailing winds. If one or more of the COPVs liberated under pressure (which we have seen before many times with SpaceX RUDs), it could shed part or all of its overwrap along the way even further.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Star One on 03/30/2021 07:04 pm
Not sure why anyone is so bothered by the destruction of these early Starships, do people think that developing something as ground breaking as Starship wasn’t going to involve a lot of things going bang.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Falcon H on 03/30/2021 07:12 pm
I suspect that SpaceX is having discussions about alternate landing methods right now. They are not ones to fall for the cost sunk fallacy. There are three main options that I can think of.

1.) Keep the current design and work out engine restart issues:

Perhaps the current restart issues are simply teething problems that will be worked out with a little more testing. Header tank tweaks and small Raptor refinements may be all that is needed to fix the problem. If I was in their shoes, I would look into constructing a test stand that allows a Raptor and header tank to be started horizontally and then swung into a vertical position.

The more worrying possibility is that FFSC is so complex that Raptor will always be difficult to start quickly.


2.) Switch from Raptors to dedicated landing engines:

I have had a hard time confirming this, but my understanding is that the sea level Raptors are only used during landing. If this is the case, perhaps they could switch to dedicated landing engines that are simpler and easier to start. They could feed exclusively from the header tanks, so they wouldn't need to use the same fuel as the Raptors. Perhaps they could even be hypergolic.


3.) Switching to wings:

It is possible that propulsive landing will never be reliable enough for crew. Lighting engines a second before landing does not leave much room for error! Switching to wings would likely increase reliability a great deal. Starship already has large aero surfaces, so the weight gain would probably not be too dramatic. Another advantage is that they could eliminate the sea level engines and use vacuum optimized engines exclusively.

An obvious downside is that this would not work on Mars, but they could retain propulsive landing for the Mars variant. Most Starship flights will be to LEO, so increasing  the reliability of the LEO variant seems like a good choice.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 03/30/2021 07:14 pm
I suspect that SpaceX is having discussions about alternate landing methods right now. They are not ones to fall for the cost sunk fallacy. There are three main options that I can think of.

1.) Keep the current design and work out engine restart issues:

Perhaps the current restart issues are simply teething problems that will be worked out with a little more testing. Header tank tweaks and small Raptor refinements may be all that is needed to fix the problem. If I was in their shoes, I would look into constructing a test stand that allows a Raptor and header tank to be started horizontally and then swung into a vertical position.

The more worrying possibility is that FFSC is so complex that Raptor will always be difficult to start quickly.


2.) Switch from Raptors to dedicated landing engines:

I have had a hard time confirming this, but my understanding is that the sea level Raptors are only used during landing. If this is the case, perhaps they could switch to dedicated landing engines that are simpler and easier to start. They could feed exclusively from the header tanks, so they wouldn't need to use the same fuel as the Raptors. Perhaps they could even be hypergolic.


3.) Switching to wings:

It is possible that propulsive landing will never be reliable enough for crew. Lighting engines a second before landing does not leave much room for error! Switching to wings would likely increase reliability a great deal. Starship already has large aero surfaces, so the weight gain would probably not be too dramatic. Another advantage is that they could eliminate the sea level engines and use vacuum optimized engines exclusively.

An obvious downside is that this would not work on Mars, but they could retain propulsive landing for the Mars variant. Most Starship flights will be to LEO, so increasing  the reliability of the LEO variant seems like a good choice.

The bellyflop is a here to stay maneuver I think, the key is getting everything to work.

Bear in mind, raptor is just as much in a developmental stage right now as Starship is, and a raptor failure isn’t something to be unexpected.

SN15, as mentioned, will be more robust, and will have more robust raptors, so I think there are good odds there with it.

Just takes some patience  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CruddyCuber on 03/30/2021 07:15 pm
Not sure why anyone is so bothered by the destruction of these early Starships, do people think that developing something as ground breaking as Starship wasn’t going to involve a lot of things going bang.

It certainly has been groundbreaking  ;)

Image credit:  Rgvaerialphotography

Edit: This is an SN8 era photo.  Sorry if I caused any confusion.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Norm38 on 03/30/2021 07:17 pm

3.) Switching to wings:

An obvious downside is that this would not work on Mars, but they could retain propulsive landing for the Mars variant.

The ONLY way to make propulsive landing work on Mars is to make it work on Earth first, and make it work 100 times in a row.  Using propulsive landing from LEO is the ONLY way to get the necessary flight rate.  There is no turning back.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 03/30/2021 07:18 pm
What do you think?

From LabPadre's launchpad cam.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BunkerTheHusky on 03/30/2021 07:24 pm
At first I was thinking that the FTS was triggered due to the tendency of SN8 through SN10 seemingly coming down over the orbital launch mount before being pushed by the flip'n'burn maneuver to be over the landing zone. However, seeing the debris on LabPadre's launch pad cam, it makes me wonder if it was off-course closer to either hopper, or the sub-orbital pads. Could be entirely wrong and not fully appreciate the physics at work of having a methane tank detonated by C4, but some of those parts in the road and surrounding wetlands don't add up to me.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/30/2021 07:25 pm
Not sure why anyone is so bothered by the destruction of these early Starships, do people think that developing something as ground breaking as Starship wasn’t going to involve a lot of things going bang.

It certainly has been groundbreaking  ;)

Image credit:  Rgvaerialphotography

I didn't understand if tank farm is fine. Fromo photos looks like yes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: kttopdad on 03/30/2021 07:29 pm
Not sure why anyone is so bothered by the destruction of these early Starships, do people think that developing something as ground breaking as Starship wasn’t going to involve a lot of things going bang.

I'd like to add that as an aerospace test engineer (15 years software test with NASA, 5 years product development/testing outside of NASA) I have a lot of respect SpaceX's product development approach.  Folks seem to be missing the point that the test program is going so well that they're able to skip/scrap *entire sequences* of pre-built hardware.  The data they're generating is being incorporated into advanced designs at a rate that "old space" (my alma mater and first love) can't hope to match.  Don't confuse dramatic events with failure - look at the progress they've made since the first hop a bit over a year ago.  They've crossed off a ton of test objectives, retired a host of unknowns, and are iterating their design at an amazing pace.  I would observe that an objective look at SpaceX development progress to date is a better measure of their potential for success than obsessing over "failures" that are just expected test results.  My $0.02.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 03/30/2021 07:32 pm
I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

The NWS radar image posted elsewhere shows the hot water vapor produced by combustion traveled much further than a a few hundred meters. Light fragments of COPV overwrap, Mylar film, etc. could easy be tossed much, much higher than a couple hundred meters by the detonation itself, then carried aloft further by updrafts and prevailing winds. If one or more of the COPVs liberated under pressure (which we have seen before many times with SpaceX RUDs), it could shed part or all of its overwrap along the way even further.

Totally agree there is some slight possibility for small pieces to make such a journey. Improbable but not impossible.

Where this report falls is the supporting details. Again NOT impossible but not quite right either.

The image shows a large piece apparently several times the size of a hand. Not a small piece.

"Still warm" from the fire simply can't be true both from the time exposed to the fire and from travelling 8Km through cold air a couple Km up.
 
It looks evenly black. It does NOT look like blown COPV overwrap (no afro fuzz of carbon fibre, the edges look clean cut), it looks like insulation batting. I haven't seen any insulation type materials that are black, mostly we see white. So what is it?

What on Starship is made of all black, low density, floppy materials that don't burn in the fire?

On the Gripping hand we have previously seen obvious FUD about pieces ending up in Mexico. Is this another FUD?

This report does reach the level of "should be checked out" but it is far from totally believable.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/30/2021 07:35 pm
Think positive: With all the fog, there are no explosion pictures, which will prevent several media from reporting another "failure" of SpaceX.

Great point. SpaceX (unluckly) is not immune of PR, even if they generally don't care. Is their interst to raise public interest. A lot of booms  can also worry future investors,(I don't think they are all engineersor aided by engineers).

Speaking about prototipes, do we now wath is the power of fts explosives? It surprised me how destroyed sn11 . With only two charges in the middeli thought it would destroy only the tanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 03/30/2021 07:37 pm
I've read through this and the entire previous thread. A number of random thoughts and comments:

1 - I still wonder how much of the "Raptor problems" are really fuel feed problems

2 - Why shouldn't SpaceX be willing to take real payload (Starlinks) on even say the second orbital flight, assuming you had a deployment mechanism. It's inconsequential whether you can successfully land the SH and/or SS. You're going to expend them anyway, so if you are confident of reaching orbit (and ascent seems to be the easier part of the problem than descent/landing), why not take advantage of that orbital flight to deploy a pile of satellites?

3 - The lamenting of "failures" here is kind of surprising. The SpaceX process is akin to Agile Development in computer science. While it's understandable that the mainstream media calls these "SpaceX failures", we know this is the SpaceX methodology. The same methodology that gave reusable orbital class first stages on F9 and is disrupting the entire launch industry. IMHO its a proven successful process.

4. NSF has stood out for the positive and troll-free environment for many years. But in particular this and the previous thread IMHO have trended toward more toxicity. Some posters who are not moderators are being condescending and some are commanding others to post certain ways, behave certain ways. For me, it detracts from the long-term positive and constructive content that we've become accustomed to here. I find it much better when we can talk about the prototypes more than how others should think or behave. I hope that going forward this forum doesn't end up like so many other forums on the internet.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oberonian on 03/30/2021 07:39 pm
Now we know why the road has to be closed.  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 03/30/2021 07:57 pm
I've read through this and the entire previous thread. A number of random thoughts and comments:

1 - I still wonder how much of the "Raptor problems" are really fuel feed problems

2 - Why shouldn't SpaceX be willing to take real payload (Starlinks) on even say the second orbital flight, assuming you had a deployment mechanism. It's inconsequential whether you can successfully land the SH and/or SS. You're going to expend them anyway, so if you are confident of reaching orbit (and ascent seems to be the easier part of the problem than descent/landing), why not take advantage of that orbital flight to deploy a pile of satellites?

3 - The lamenting of "failures" here is kind of surprising. The SpaceX process is akin to Agile Development in computer science. While it's understandable that the mainstream media calls these "SpaceX failures", we know this is the SpaceX methodology. The same methodology that gave reusable orbital class first stages on F9 and is disrupting the entire launch industry. IMHO its a proven successful process.

4. NSF has stood out for the positive and troll-free environment for many years. But in particular this and the previous thread IMHO have trended toward more toxicity. Some posters who are not moderators are being condescending and some are commanding others to post certain ways, behave certain ways. For me, it detracts from the long-term positive and constructive content that we've become accustomed to here. I find it much better when we can talk about the prototypes more than how others should think or behave. I hope that going forward this forum doesn't end up like so many other forums on the internet.


Agree with all your points. On point 2, who says they won't launch Starlinks on early orbital flights? I expect that once SpaceX has reasonable confidence of success to orbit (but not necessarily return and land), they'll likely launch Starlink satellites. There is one caveat though. They have not been working on a deployment bay yet that I know of. Something they may want to test with a small number of satellites first.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: abaddon on 03/30/2021 08:11 pm
4. NSF has stood out for the positive and troll-free environment for many years. But in particular this and the previous thread IMHO have trended toward more toxicity. Some posters who are not moderators are being condescending and some are commanding others to post certain ways, behave certain ways.
I liked your post overall, and I somewhat agree with the above specifically, but the fact of the matter is the deluge of comments overwhelms the moderators and some level of self-moderation requests from community members are not only appropriate but required.  (I do agree that, while I sympathize with the frustration, editing for tone on these posts would be helpful).

In particular, the failure of many posters to recognize that only UPDATES should be posted in the UPDATES thread is a continual source of frustration that does not appear to be improving, to the point where there is a poll asking if only certain members should be given update privileges (not something I personally would want to see happen).  Worth keeping that in mind when considering "not moderators" desperately attempting to help herd the cats.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 03/30/2021 08:11 pm
Disagree. It’s going to be in line with EXPECTATIONS, but not in line with HOPES.

Disagree.  The line is not so clear as your language seems to imply.  There are published expectations from quite some time ago regarding pre-SN1 hardware, and while you and I might not expect current July expectations to be met, and might consider those as "hopes" they are expectations of some, and published ones at that.

It would seem wise to define what our expectations are.  The July date is a NET.  Plans have already changed since they were "announced."  Given that SN15 is an all new tank and an all new Raptor design, I expect teething problems, ground losses, continued battles involving governance and safety, failed attempts to achieve proper supersonic transitions, continued adhesion problems with tiles, at least one destructive event involving the prop farm, possibly the loss of the orbital mount currently in construction, but certainly repairs involving the embracerons, at least two major changes in direction involving craft return, and two or three major raptor design iterations.  I don't expect in-orbit refueling tests before 2023.

My problem is that my hopes are indeed quite a bit higher than that.  Other people seem to have set their expectations high.  At Google, if you met all your quarterly objectives you were dinged for not having been aggressive enough.  It is my believe that the high expectation setting, especially by company management, should be viewed in that way here.  YMMV.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Spindog on 03/30/2021 08:11 pm
Really the fuel flow problems for the horizontal re-start and flip seem to be possibly a bridge too far. Perhaps going to an aerodynamic fin flip and then restarting the raptors makes sense.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/30/2021 08:19 pm
During the last frames from engine bay I saw a cloud coming off a raptor. Seemed like black smoke to me, but I'm not an expert. Was it really smoke? IS it normal? I think not,because was  darker than vent vapour (but I repeat I'm not an expert ).

But seems like there was some serius issue with that Starship. An engine not going well during ascent (maybe for its own problems), debris falling during the apogee-skydiving, problems during relight, and constant downlink issues.  I think these aren't related to fog (fog is thin and if it would cause issue they would have known (RF comunications problems due to clouds are known) they would have scrubbed).

But at least we know that a Raptor, if chamber pressure is wrong, doesn't explode. I don't know how other engines would have performed, but since is a complex engine it is a good thing.

I see two possibilities:
1)sn11 was "cursed", I mean there were many unrelated issues
2)a single thing caused every issue. But what?Maybe a problem with avionics? An electric power related issue? I don't know.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 03/30/2021 08:23 pm
Here's a perspective unique to humans from a somewhat similar problem:  Toddlers learning to walk fall down 17 times per hour.

My guess is Elon wishes he could iterate Starships that quickly, regardless of how many times they fall down.  Elon has 6 kids, I'm sure he's seen this.

https://www.veipd.org/earlyintervention/2014/01/09/toddlers-weeble-wobble-and-fall-down-when-is-it-cause-for-concern
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 03/30/2021 08:24 pm
Really the fuel flow problems for the horizontal re-start and flip seem to be possibly a bridge too far. Perhaps going to an aerodynamic fin flip and then restarting the raptors makes sense.

Remember this is a maneuver to be used on the Moon and Mars as well, so an aero flip won't work everywhere. The goal is not just to land on earth. Thrusters might be a possibility, but I suspect the power needed is the reason they use the Raptors.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: abaddon on 03/30/2021 08:24 pm
Disagree. It’s going to be in line with EXPECTATIONS, but not in line with HOPES.
My problem is that my hopes are indeed quite a bit higher than that.
I mean, you are right.  It is your problem.  You should adjust your hopes and/or expectations accordingly.  There's a lot of irrational optimism hanging about these parts, so I understand it can be hard to calibrate.

Use past experience with SpaceX to inform future hopes.  Take everything with a pinch of salt.  Sit back, have a drink, and enjoy the view.  Or not, as you prefer.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: _MECO on 03/30/2021 08:25 pm
Think positive: With all the fog, there are no explosion pictures, which will prevent several media from reporting another "failure" of SpaceX.

Great point. SpaceX (unluckly) is not immune of PR, even if they generally don't care. Is their interst to raise public interest. A lot of booms  can also worry future investors,(I don't think they are all engineersor aided by engineers).

Speaking about prototipes, do we now wath is the power of fts explosives? It surprised me how destroyed sn11 . With only two charges in the middeli thought it would destroy only the tanks.
But think long-term. Now historically we don't have any good footage of one of the first Starship prototypes exploding. That's one less for the "how not to land an interplanetary spacecraft" montage!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/30/2021 08:30 pm
As as been reported on the update thread two raptor failed relight, and then FTS was triggered. THis doesn't explain all issue.

Same question of sn9: was a raptor problem or a plumbing one?
As Scott Manley's video (of a few week ago) sn9 relight issue was related to a raptor preburner.

So i think these two failure were due to engine problems, because all other starship raptor ignited correctly (expecially sn9 one, but wasn't plumbing fault), and sn10 issues were related to bubble, caused by not using autogenus presurrization.

Conclusion: seems like that the problems don't come from slosh due to violent rotation, but rather from engines or not using autogenus presurrization.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: yg1968 on 03/30/2021 08:37 pm
I had a bad feeling about SN11. Hopefully the upgrades to SN15 will do the trick.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Spindog on 03/30/2021 08:40 pm
Really the fuel flow problems for the horizontal re-start and flip seem to be possibly a bridge too far. Perhaps going to an aerodynamic fin flip and then restarting the raptors makes sense.

Remember this is a maneuver to be used on the Moon and Mars as well, so an aero flip won't work everywhere. The goal is not just to land on earth. Thrusters might be a possibility, but I suspect the power needed is the reason they use the Raptors.

Yea, for Mars it will be used but for the moon there would be no reason to ever go horizontal. But, of course, some thrust will be needed to settle fuel. I dont know if Mars would have the atmospheric density to support an aerodynamic flip but it would likely be too slow and have to be started too high. But, in any case, the overwhelming majority of SS landings will be on earth and simplifying the plumbing for success seems like it may be a good approach.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/30/2021 08:40 pm
I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

The NWS radar image posted elsewhere shows the hot water vapor produced by combustion traveled much further than a a few hundred meters. Light fragments of COPV overwrap, Mylar film, etc. could easy be tossed much, much higher than a couple hundred meters by the detonation itself, then carried aloft further by updrafts and prevailing winds. If one or more of the COPVs liberated under pressure (which we have seen before many times with SpaceX RUDs), it could shed part or all of its overwrap along the way even further.

Oh for sure, but we're not talking about "light fragments of COPV overwrap or Mylar film". We're talking about somewhat hefty macroscopic pieces of insulation. They're light but they're not feather light, as I previously stated.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/30/2021 08:45 pm
I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

The NWS radar image posted elsewhere shows the hot water vapor produced by combustion traveled much further than a a few hundred meters. Light fragments of COPV overwrap, Mylar film, etc. could easy be tossed much, much higher than a couple hundred meters by the detonation itself, then carried aloft further by updrafts and prevailing winds. If one or more of the COPVs liberated under pressure (which we have seen before many times with SpaceX RUDs), it could shed part or all of its overwrap along the way even further.

Oh for sure, but we're not talking about "light fragments of COPV overwrap or Mylar film". We're talking about somewhat hefty macroscopic pieces of insulation. They're light but they're not feather light, as I previously stated.

Just how heavy do you think a hand-sized fragment of COPY overwrap is? Or a similarly-sized fragment of Nomex cable wrap? That stuff is a few ounces at most and will literally float for miles in a stiff breeze. And it seems like SpaceX understands this, as they have created a Debris Hotline to call for people who find stuff.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Stan-1967 on 03/30/2021 08:51 pm
I agree with the sentiment that the flip turn is problematic, however I don't see that it is unsolvable.  Quick iteration obviously helps with this, but I think it hard to argue there is a trajectory of improvement since the first 10km flight.

As I understand it, there is not enough control authority from the aero surfaces to execute the pitch up maneuver, it requires the trust of the Raptors to fully rotate.  When I watch the pitch up sequence, I see the following:
1.  vehicle descending in level configuration at around T+6'28"
2.  2X Raptor ignition ( milliseconds apart) T+6'31"
3.  Aft "Elonerons" ( or whatever they are called) tuck in to minimum deflection at T+6'33"
4.  rapid pitch up & subsequent 4 straight failures.

What I wonder is why not initiate the minimum deflection of the aft "Elonerons" several seconds prior to engine ignition?  If the pitch up angle can be changed even 5 or 10 degrees, those few seconds can allow for a lot of liquid to calmly settle towards the baffles, & any bubbles also have opportunity to rise to the surface.
 
I think the forward control surfaces should be able to keep any roll moments under control when the aft move to minimum drag configuration.   The Raptor ignition is the most violent part of the sequence, but if done when the solution has already some opportunity to settle, it seems this favors a smoother start sequence.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VoodooForce on 03/30/2021 09:08 pm
Did Hoppy survive ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rekt1971 on 03/30/2021 09:08 pm
Did Hoppy survive ?

Yep, Hoppy will outlive us all.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 03/30/2021 09:22 pm
I found it interesting that the one engine on ascent appeared to be burning fuel rich giving the flame an orange colour. Right when the first engine shut down it briefly was burning blue but quickly turned orange again.

Coincidentally? it appeared to be in the same position as the engine on SN10 that also appeared to burn fuel rich, IIRC it was the same engine that had off nominal thrust during the static fire.

Do we know whether this was the engine 2 that Elon said had problems?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 03/30/2021 09:29 pm
I found it interesting that the one engine on ascent appeared to be burning fuel rich giving the flame an orange colour. Right when the first engine shut down it briefly was burning blue but quickly turned orange again.

Coincidentally? it appeared to be in the same position as the engine on SN10 that also appeared to burn fuel rich, IIRC it was the same engine that had off nominal thrust during the static fire.

Do we know whether this was the engine 2 that Elon said had problems?

This was seen on SN10 as well. It is could be related to how Raptor throttles. (at least these early versions) The engines have to be throttled very low for these flights to not exceed ~10km. They might think it is safer to only run one engine at the really low throttle setting, and that would explain the sudden throttle up as another engine was turned off only to throttle down again shortly afterwards.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 03/30/2021 09:37 pm
I mean, you are right.  It is your problem.  You should adjust your hopes and/or expectations accordingly.  There's a lot of irrational optimism hanging about these parts, so I understand it can be hard to calibrate.

SpaceX has "aggressive objectives" -- these are a solution to mediocrity and under-achievement.  They should not be confused for "expectation" guidance.  There's nothing inherently wrong with high hopes and dreaming big, but I don't think it's constructive to hold SpaceX's objectives as expectations.  These are manufacturing prototypes of an unfinished design....
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: geekesq on 03/30/2021 09:38 pm
The flip is fraught with frightening features, but SpaceX's Russian "admirers" have already suggested the solution when it comes to Earth landings.

That's right, a trampoline
Okay, maybe not a trampoline: you'd bounce right off, (unless you have a capture system to grab the Starship right as it hits 0 velocity)?
So instead, an inflatable stunt cushion like movies use for stunt work. A really big one. Even on the airless moon, that could work, just fill it with hydrogen electrolyzed from the ice there. 

A big stunt cushion, to be sure, and hella strong if it is going to catch a Starship falling at 40 meters per second (which I guesstimate to be terminal velocity of a horizontal Starship on Earth).  But at least SpaceX has proven that Starship can accurately land in the middle  of the cushion: "The crater was in the right place."

Now, for the Moon and Mars: obviously you have to land a robotic stunt cushion deploying system there before you can use this method there.  And your Starship lunar landings will have to use a way other than aerodynamic drag to slow down, but gravity is less, so less of a challenge. And you'll want an erector crane as well, I would think, to lift the Starship off the cuchion and into a vertical launch position.  All doable.

And really, is it much crazier than the flip and burn maneuver?


Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: eriblo on 03/30/2021 09:56 pm
I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

The NWS radar image posted elsewhere shows the hot water vapor produced by combustion traveled much further than a a few hundred meters. Light fragments of COPV overwrap, Mylar film, etc. could easy be tossed much, much higher than a couple hundred meters by the detonation itself, then carried aloft further by updrafts and prevailing winds. If one or more of the COPVs liberated under pressure (which we have seen before many times with SpaceX RUDs), it could shed part or all of its overwrap along the way even further.
Oh for sure, but we're not talking about "light fragments of COPV overwrap or Mylar film". We're talking about somewhat hefty macroscopic pieces of insulation. They're light but they're not feather light, as I previously stated.
Just how heavy do you think a hand-sized fragment of COPY overwrap is? Or a similarly-sized fragment of Nomex cable wrap? That stuff is a few ounces at most and will literally float for miles in a stiff breeze. And it seems like SpaceX understands this, as they have created a Debris Hotline to call for people who find stuff.
Yeah, I must admit to being slightly heavier than a feather but I have still had climb rates of >2000 ft/min while dangling from a glorified plastic bag just from the Sun heating the air over a specific patch of ground by a few degrees :)

The Brownsville sounding I posted earlier suggest that the conditions were very stable but that a volume of air heated to 40 C at ground level could have risen to the inversion layer at 2 km. Assuming that the conditions were not to far off at the coast an hour later that gives a theoretical limit of closer to 3 tonnes of air rising to 2 km for every 1 kg of methane burnt...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jake-ZA on 03/30/2021 10:02 pm
Not sure why anyone is so bothered by the destruction of these early Starships, do people think that developing something as ground breaking as Starship wasn’t going to involve a lot of things going bang.

Many years ago I attended a public lecture on the rapid evolution of Cichlid fish species in Lake Malawi, and was amused at the consternation when it was mentioned that there seemed to be equally rapid extinction taking place - many species common earlier had disappeared. Some members of the audience didn't seem to get that extinction is part and parcel of evolution, and had a sort of "Save the lemmings" mindset.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 03/30/2021 10:05 pm
From my perspective, maybe they should flip upright at 2km instead of 1km.  Give the fuel time to settle and start the engines.  Yes it may use more fuel slowing down, but it doesn't seem like much.  It also gives you engine out if one doesn't start for landing if you can land with 2 engines. 

So if Musk can't get 150 tons to LEO.  So he has to lower this by 10-20 tons to be able to have the fuel for landing with no engine problems. 

Also better legs for Mars landings and lift offs.  So you loose another 10-20 tons of payload.  If you can keep it above 100 tons that would be great. 

To me, getting this thing working first, then worry about mass. 

Maybe add the waist thrusters on all Starships, to help with landings.  They can be on the sides and not on the windward side. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 03/30/2021 10:07 pm
The flip is fraught with frightening features, but SpaceX's Russian "admirers" have already suggested the solution when it comes to Earth landings.

That's right, a trampoline
Okay, maybe not a trampoline: you'd bounce right off, (unless you have a capture system to grab the Starship right as it hits 0 velocity)?
So instead, an inflatable stunt cushion like movies use for stunt work. A really big one. Even on the airless moon, that could work, just fill it with hydrogen electrolyzed from the ice there. 

A big stunt cushion, to be sure, and hella strong if it is going to catch a Starship falling at 40 meters per second (which I guesstimate to be terminal velocity of a horizontal Starship on Earth).  But at least SpaceX has proven that Starship can accurately land in the middle  of the cushion: "The crater was in the right place."

Now, for the Moon and Mars: obviously you have to land a robotic stunt cushion deploying system there before you can use this method there.  And your Starship lunar landings will have to use a way other than aerodynamic drag to slow down, but gravity is less, so less of a challenge. And you'll want an erector crane as well, I would think, to lift the Starship off the cuchion and into a vertical launch position.  All doable.

And really, is it much crazier than the flip and burn maneuver?

I believe this was iteratively Kerbaled in an earlier thread a few months ago

1) Deployment problems are solved by making the "bouncy castle" into "floaties" under each flap.
2) Splashdown into water is easiest.
3) "Motorboat" back to the launch tower using the Raptors.

Works in Kerbal
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FinalFrontier on 03/30/2021 10:15 pm
With all this discussion about the flip and landing modes going to add a couple things here.
There isn't (really) a giant technical difficulty or unknown with this landing method. The only thing maybe that might need to change is how rapidly the vehicle pivots to vertical, possibly use a slower rate. And/or doing this flip at a higher altitude and burning the engines longer for better stability and slower deceleration rates and forces.

This of course would burn much more fuel which has design consequences but it may be necessary to just dial the intensity of that maneuver back some. But ditching it entirely? Not necessary. The issues with this vehicle we are seeing are related entirely to:
1. Manufacturing techniques and vehicle structures.
2. Engine maturity issues.

Alot of these have to do with the fact that these still test prototype vehicles, something we all need to remind ourselves of today. You don't spend a massive amount of money and time to put all the bells and whistles and complex manufacturing techniques onto a vehicle which is likely to blow up. Instead, if you are pursuing a rapid test methodology as SpaceX is, you spend the absolute bare minimum of money and time and keep things as simple as possible so that your "best stuff" is not wasted when the vehicles crash. Then you add the "best stuff" later.
Best stuff here can be defined as:
Automated "single piece" manufactured tank and propulsion sections.
Large 3d printed vehicle sections.
Large additive manufactured vehicle sections
More complex (and expensive) stringer+isogrid enforced paneling for tanks
Structurally beefed up "mission" section (nose fairing as it's called right now)
Full vehicle heatshield
Full vehicle RCS
Full vehicle AGP system
Better avionics suite

And so on it goes.

The sideaffect or draw back of the "rapid testing" methodology is that in many cases the prototypes will have flaws that the "operational" version of starship would not have. That leads to things like today.

So final thoughts here. This failure was not unexpected in fact I am surprised it didn't happen sooner on the first or second flights, but it was going to happen eventually. Second, this doesn't impact their program negatively for the most part nor do I think it requires any big changes. The issue here is almost certainly either engine maturity related or manufacturing defect in the engine that failed or both. Not something you are likely to see down the road on the operational version.

Third, what it DOES impact is the Elon time goal of trying to go full orbital this summer. I don't see that happening now. But then again that was a very I'm to low chance event anyway, and I don't think that most of us believed that timeline was going to happen. ALL of the remaining starship tests would have had to go perfectly AND all of the prototype ground testing for BN1 and BN2 would have had to go perfectly as well for this to happen. And that was almost impossible statistically speaking.

Orbit is probably still achievable before the end of the year, but I also don't think the first orbital starship will make it back. Fully expecting it to burn up on re entry.

With that said this really isn't a huge problem or a big deal. Remember it's a test program and these are low cost construction prototypes. Not finished vehicles. And SpaceX hasn't been at this very long relatively speaking, they have beaten every time scale even compared to large aircraft development programs. So they are doing just fine.
Like I said after SN10 we all want to see Mars and the Moon sooner not later but this is a complex vehicle and it will take time. It will more than likely take more time than folks want it to take and far more than Elon Time but that's what the deal is when it comes to complex engineering systems.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: philw1776 on 03/30/2021 10:28 pm
In this poll most people here forecast orbital by Fall 2020

https://forum.nasaspaceflight.com/index.php?topic=52134.0

My take from end 2020 post was May 2022 or later for reasons I stated in the thread

https://forum.nasaspaceflight.com/index.php?topic=52134.msg2174213#msg2174213

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jimmy Murdok on 03/30/2021 10:31 pm
From my perspective, maybe they should flip upright at 2km instead of 1km.  Give the fuel time to settle and start the engines.  Yes it may use more fuel slowing down, but it doesn't seem like much.  It also gives you engine out if one doesn't start for landing if you can land with 2 engines. 

So if Musk can't get 150 tons to LEO.  So he has to lower this by 10-20 tons to be able to have the fuel for landing with no engine problems. 

Also better legs for Mars landings and lift offs.  So you loose another 10-20 tons of payload.  If you can keep it above 100 tons that would be great. 

To me, getting this thing working first, then worry about mass. 

Maybe add the waist thrusters on all Starships, to help with landings.  They can be on the sides and not on the windward side.

From a pure engineering and success perspective I ageee, except that you have safety responsabilities and FAA analyzing hazards. If you relight, do the maneuver high up and things go bad like today, your crash location has massive uncertainty. If there is a high up explosión, you will drop debris in a massive radius.
This is defined by a cone, usually one based on the gliding ratio: failure of FTS and loss of control of aero surfaces and one by the debris of an explosion. The lower you are, the smaller the cone will be. Redundancies and mitigations like low altitude of risk maneuvers count.
I understand that today they found stuff at least 8km away, imagine if you explode high up.

I build and fly autonomous VTOL drones, flying low is a regulatory advantage to minimize ground risk. Same about doing the transitions (multicopter to plane and reverse) at low altitude and in controlled areas.

Edit: clarified VTOL transition concept
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alastairmayer on 03/30/2021 10:35 pm
A couple of thoughts.

1. There's now contradicting information coming from an anonymous source at KSC and Elon's tweets.
    a. The KSC source claims FTS was activated because the vehicle went off course but Elon claims "At least the crater is in the right place!" so this is a contradiction.
This is NOT a contradiction.  The FTS doing its job properly would put the crater in the right place.

Quote
    b. The KSC source claims that two engines failed to light, but Elon only mentions a single engine with issues "Looks like engine 2 had issues on ascent & didn’t reach operating chamber pressure during landing burn, but, in theory, it wasn’t needed." The note of "in theory, it wasn't needed" implies that the other two engines would have landed successfully.
Would have ... if they had lit. Again, not contradictory.

Quote
    c. How do KSC sources already know details of what went wrong when they're nowhere nearby and in NASA, not SpaceX. This seems like very fast communication for government communication.
Good question, but note that SpaceX has people (and facilities) at KSC.

Quote
Let's keep discussion high quality.

Indeed! :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 03/30/2021 10:45 pm
RGVAerial photos of debris coming in:

https://twitter.com/RGVaerialphotos/status/1377001018102276097

oh no
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 03/30/2021 10:52 pm
I don't really get why everyone is concentrating on the landing flip maneuver at all.  The problem here wasn't anything at all to do with the flip.  Engines that were already not operating correctly (Elon said chamber pressure didn't reach expected levels during ascent) failed to re-light.  They where in a phase of the flip which was absolutely optimal for engine relight - the first engine was supplying some "gravity", and they hadn't started to rotate quickly yet.  Fuel supply should have been a non-issue at that point.

To me, the thing I'm worried about (slightly) is raptor development, not the flip.  No matter how you land, raptor needs to be able to reliably relight.  At the moment, that seems to be proving much harder than expected.  We don't know if that's a fundamental issue with raptor's design, or if it's just a matter of tweaking until it works right.  The only "worrying" thing I see is that Elon was hoping that by raptor 50 they would be into mass production, and that's clearly not the case as of now, due to continuing issues with getting them to work reliably.  Hopefully that's just a small delay to full production.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 03/30/2021 10:59 pm
They're disassembling the Sarens framework. I assume BN1 will be reverse built in the highbay so they won't need Ludicrous Transporter for a while.
More evidence for the theory that the Sarens transporter is intended for post flight retrieval of Starships rather than solely booster transportation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alastairmayer on 03/30/2021 11:00 pm

oh no

And now we know why they built a doghouse for a robot dog.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/30/2021 11:06 pm
I suppose a "possibility" could be to re-engine a future vehicle with Merlins to continue with the "Proof of Concept" test flights while ironing out the Raptors... The X-15 was flight tested with "twin pack" XLR 11 until the more complex XLR 99 was reliable enough...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 03/30/2021 11:10 pm
I suppose a "possibility" could be to re-engine a future vehicle with Merlins to continue with the "Proof of Concept" test flights while ironing out the Raptors... The X-15 was flight tested with "twin pack" XLR 11 until the more complex XLR 99 was reliable enough...

Merlins run RP1, so they'd have to change a lot of things on the vehicle.  May not happen.

This would make the case for a scaled down version to figure out some aspects first.  But Elon don't do like that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/30/2021 11:16 pm
I suppose a "possibility" could be to re-engine a future vehicle with Merlins to continue with the "Proof of Concept" test flights while ironing out the Raptors... The X-15 was flight tested with "twin pack" XLR 11 until the more complex XLR 99 was reliable enough...

Merlins run RP1, so they'd have to change a lot of things on the vehicle.  May not happen.

This would make the case for a scaled down version to figure out some aspects first.  But Elon don't do like that.
But he would continue to accumulate aero data, TPS and refine control laws for landing... Just musing...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 03/30/2021 11:16 pm
Changing to Merlins would tell them nothing about doing these maneuvers with raptors, and they're building raptors quickly for the same reason they're building Starships quickly.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 03/30/2021 11:18 pm
I suppose a "possibility" could be to re-engine a future vehicle with Merlins ...

New Raptors are inbound, so this is likely premature.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/30/2021 11:18 pm
Changing to Merlins would tell them nothing about doing these maneuvers with raptors, and they're building raptors quickly for the same reason they're building Starships quickly.
Nobody said they would have to stop testing with Raptors...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FinalFrontier on 03/30/2021 11:27 pm
With all this discussion about the flip and landing modes going to add a couple things here.
There isn't (really) a giant technical difficulty or unknown with this landing method. The only thing maybe that might need to change is how rapidly the vehicle pivots to vertical, possibly use a slower rate. And/or doing this flip at a higher altitude and burning the engines longer for better stability and slower deceleration rates and forces.

This of course would burn much more fuel which has design consequences but it may be necessary to just dial the intensity of that maneuver back some. But ditching it entirely? Not necessary. The issues with this vehicle we are seeing are related entirely to:
1. Manufacturing techniques and vehicle structures.
2. Engine maturity issues.

Alot of these have to do with the fact that these are still test prototype vehicles, something we all need to remind ourselves of today. You don't spend a massive amount of money and time to put all the bells and whistles and complex manufacturing techniques onto a vehicle which is likely to blow up. Instead, if you are pursuing a rapid test methodology as SpaceX is, you spend the absolute bare minimum of money and time and keep things as simple as possible so that your "best stuff" is not wasted when the vehicles crash. Then you add the "best stuff" later.
Best stuff here can be defined as:
Automated "single piece" manufactured tank and propulsion sections.
Large 3d printed vehicle sections.
Large additive manufactured vehicle sections
More complex (and expensive) stringer+isogrid enforced paneling for tanks
Structurally beefed up "mission" section (nose fairing as it's called right now)
Full vehicle heatshield
Full vehicle RCS
Full vehicle AGP system
Better avionics suite

And so on it goes.

The sideaffect or draw back of the "rapid testing" methodology is that in many cases the prototypes will have flaws that the "operational" version of starship would not have. That leads to things like today.

So final thoughts here. This failure was not unexpected in fact I am surprised it didn't happen sooner on the first or second flights, but it was going to happen eventually. Second, this doesn't impact their program negatively for the most part nor do I think it requires any big changes. The issue here is almost certainly either engine maturity related or manufacturing defect in the engine that failed or both. Not something you are likely to see down the road on the operational version.

Third, what it DOES impact is the Elon time goal of trying to go full orbital this summer. I don't see that happening now. But then again that was a very slim to low chance event anyway, and I don't think that most of us believed that timeline was going to happen. ALL of the remaining starship tests would have had to go perfectly AND all of the prototype ground testing for BN1 and BN2 would have had to go perfectly as well for this to happen. And that was almost impossible statistically speaking.

Orbit is probably still achievable before the end of the year, but I also don't think the first orbital starship will make it back. Fully expecting it to burn up on re entry.

With that said this really isn't a huge problem or a big deal. Remember it's a test program and these are low cost construction prototypes. Not finished vehicles. And SpaceX hasn't been at this very long relatively speaking, they have beaten every time scale even compared to large aircraft development programs. So they are doing just fine.
Like I said after SN10 we all want to see Mars and the Moon sooner not later but this is a complex vehicle and it will take time. It will more than likely take more time than folks want it to take and far more than Elon Time but that's what the deal is when it comes to complex engineering systems.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThereIWas3 on 03/31/2021 12:33 am
Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/31/2021 12:43 am
Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Once again nobody said anything about stop testing with Raptors... There is still much to be learned from EDL on the vehicle besides the engines...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edkyle99 on 03/31/2021 12:47 am
Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Merlin has not been tested under the flip conditions, with all the associated likely wild propellant slosh.  No guarantee it would work.

 - Ed Kyle
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 03/31/2021 01:07 am
One possible solution to the propellant sloshing/lack of propellant for re-start issue is to fabricate smaller tanks inside the larger ones at the bottom of each, with a check valve at bottom to allow the propellant in, but prevent it from coming out. That way when the main tanks are filled, the small tanks fill, but not drain out when turned about.

At the high points you connect your vents to purge to prevent over-pressurization.

Of course this all adds mass, which hurts performance, so it was probably discounted long ago. But a containment method inside the tanks seems to be the 'least complex' path (IMO) - similar to baffles but more restrictive (but they need to be able to be drained out or fed to the engines).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 03/31/2021 01:09 am
People need to get over the idea that these test articles are as valuable as they think they are, and that somehow there is a big problem with the design because they haven't aced a landing yet. A large part of the process is getting the production side right, and turning these things out - figuring out how to build them. SpaceX can perform the tests they want with these vehicles to get the data they see as the most valuable, and that data isn't necessarily what the public thinks is the most important. We tend to be overly concerned with optics, and crashing seems like a big deal, but in reality SN11 was sort of obsolete anyway. Whatever issues that SN8 - SN11 had were still persistent throughout the lineup, and I'm sure whatever happened with the flight today can be useful in further testing. The SNs aren't that valuable, and folks should stop thinking about not landing as "another failure", and "SpaceX should re-think the Starship design and add wings (or any other drastic departure)". Look, it's a test program, and they're testing out in the open for us to see. It's also a different kind of test program than has been done before, and a number of folks need to shift their perspective.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 03/31/2021 01:14 am
Bingo - the time to be actually worried about landing is when they're trying to build a fleet of 1000 of them to go to mars that need to land on mars reliably, and they're still not nailing them all.

As of today - this is a non issue.  SN15 will go up higher and faster, test something else, and if it makes it back down, it'll have *another* go at landing.  That's fine.  Eventually they'll figure out how to get it right.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aero on 03/31/2021 01:23 am
So when is the next scheduled fireworks at Starbase?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/31/2021 01:23 am
In engineering we call a rugged reusable vehicle not exactly representative of a final iteration including engine a "test mule"... It is not something unusual to those in the field...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 03/31/2021 01:26 am
Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Once again nobody said anything about stop testing with Raptors... There is still much to be learned from EDL on the vehicle besides the engines...
My software engineering experience (which may not be applicable to rocket science) makes me think that a lot of effort would be exerted on dealing with specific implementation problems with the Merlins and RP-1, which would all have to be thrown out when integrating the Raptors and CH4. Nothing is ever truly modular.

Trying to re-use tried and tested components in a new system, while an excellent idea on paper, in practice can often take more time than if you'd just started from scratch (see SLS, or even Falcon Heavy). And in the end, a Merlin Starship might end up being so different than a Raptor Starship, that any data collected from it would be useless for the final product.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 03/31/2021 01:29 am
They're disassembling the Sarens framework. I assume BN1 will be reverse built in the highbay so they won't need Ludicrous Transporter for a while.
Nomadd,

I hope you are kidding.  BN1 was never meant to be transported.  Why would they assemble this and disassemble it for BN1?  It was obviously for SN11, and that's why it won't be needed before SN15 flies.  It's to support an unstable Starship after landing until they can hook the crane to it.

Edit:  Can this thread get an FTS?  Thanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Markstark on 03/31/2021 01:35 am
SpaceX site has updated.
So does this clarify whether FTS was activated or not?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/31/2021 01:37 am
Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Once again nobody said anything about stop testing with Raptors... There is still much to be learned from EDL on the vehicle besides the engines...
My software engineering experience (which may not be applicable to rocket science) makes me think that a lot of effort would be exerted on dealing with specific implementation problems with the Merlins and RP-1, which would all have to be thrown out when integrating the Raptors and CH4. Nothing is ever truly modular.

Trying to re-use tried and tested components in a new system, while an excellent idea on paper, in practice can often take more time than if you'd just started from scratch (see SLS, or even Falcon Heavy). And in the end, a Merlin Starship might end up being so different than a Raptor Starship, that any data collected from it would be useless for the final product.
Like I mentioned earlier it was done on the X-15 program the most successful manned rocket program ever with 199 flights... Of course SpaceX can continue merrily on their current direction as long as the FAA allows them... I only suggested an option just like I did with the grid fins, eliminating landing legs and a cable catching landing... I'm perfectly fine watching carrying on as is...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 03/31/2021 01:46 am
They're disassembling the Sarens framework. I assume BN1 will be reverse built in the highbay so they won't need Ludicrous Transporter for a while.
Nomadd,

I hope you are kidding.  BN1 was never meant to be transported.  Why would they assemble this and disassemble it for BN1?  It was obviously for SN11, and that's why it won't be needed before SN15 flies.  It's to support an unstable Starship after landing until they can hook the crane to it.

Edit:  Can this thread get an FTS?  Thanks.

BN1 absolutely was meant to be transported.  A portion of its purpose is to learn the ins and outs of moving a 70 meter booster about.  This in and of itself isn't easy, and it would be a pity to loose BN2 because it fell over while in transit to the launch pad when they could have discovered the problem in their rigging had it been the less valuable BN1 that fell over instead.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sdsds on 03/31/2021 01:48 am
Clearly intended as a reference to, "Tis but a scratch." Elon might do better with this whole Twitter thing if he just got his Monty Python quotes correct. ;-)

https://twitter.com/elonmusk/status/1377020678453485573

Quote
Barely a scratch. :)
Back on the stand soon!
Will report conclusions as soon as we know them.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 03/31/2021 01:57 am
More tidbits
https://www.reddit.com/r/spacex/comments/mg914a/rspacex_starship_sn11_highaltitude_hop_discussion/gsv6qp9?utm_medium=android_app&utm_source=share&context=3
Quote
SN46's gimbal failed. (You can see in the video that it doesn't gimbal with the other two engines, and starts flailing around when it lights). I'm also told the other 2 engines did not light, not clear why. N̶o̶t̶ ̶s̶u̶r̶e̶ ̶i̶f̶ ̶t̶h̶e̶ ̶e̶x̶p̶l̶o̶s̶i̶o̶n̶ ̶c̶a̶m̶e̶ ̶f̶r̶o̶m̶ ̶F̶T̶S̶ ̶o̶r̶ ̶s̶o̶m̶e̶t̶h̶i̶n̶g̶ ̶e̶l̶s̶e̶,̶ ̶b̶u̶t̶ ̶F̶T̶S̶ ̶m̶a̶k̶e̶s̶ ̶m̶o̶s̶t̶ ̶s̶e̶n̶s̶e̶ ̶c̶o̶n̶s̶i̶d̶e̶r̶i̶n̶g̶ ̶t̶h̶e̶ ̶c̶i̶r̶c̶u̶m̶s̶t̶a̶n̶c̶e̶s̶.̶

On the bright side, the last 3 flightworthy old design Raptors are pancakes now. SN15+ will feature the new and more reliable Raptors.

Edit: FTS not used. Not sure why it exploded, header tank or common dome might have popped after E3 ignition.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 03/31/2021 02:17 am
That “flailing around” has been seen on every flight, as part of the shutdown sequence to create more room for the still-firing engines to vector. It was made more pronounced starting on SN9 after two nozzles appeared to contact one another on SN8.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 03/31/2021 02:41 am
Herb, isn't that from Michael Baylor? I believe he has sources.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Faerwald on 03/31/2021 02:52 am
There was no flailing about of the lit raptor. It was just gimballing hard over to start the turn. I suspect they probably start the Raptors somewhere central in their gimbal range.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OxCartMark on 03/31/2021 03:07 am
...

The "Mystery Structure" has a nosecone lifted inside its cage, potentially to be used as a test rig.

I stared hard at this structure with the intent of mind forcing it to be a chomper articulation development fixture but I can't come close to making it fit into that box.

Some potentially interesting observations and thoughts that someone might be able to build on-

- Framwork has 6 sides (60 degree spacing)
- The white floor is heavily built and has 36 Radial ribs (10 degree spacing)
- I'm thinking the floor rotates (its round, not hexagonal like everything else on the fixture and at Starbase)
- The black ring surrounding the white floor appears as if it may have degree wheel markings -may-
- With that hexagonal opening in the floor and hole in the nose it seems access to the interior is important to them. 
- Perhaps going to use this to hold nose while they build mock up interior?
- Perhaps a safe stable way to hold a nose with interior mock up in all wind conditions without blowing over while they have some people live in it for a while.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 03/31/2021 03:08 am
One thing the failures have kind of made me reconsider is whether they'd have reuse going smooth before doing orbit.

It seems like they may end up doing like Falcon 9 and just going for orbit before reuse is working acceptably.

Remarkable that they have the manufacturing capacity to even contemplate that approach for a rocket the size of Saturn V and with "upper stages" comparable to stripped down Space Shuttle orbiters.

Ascent worked acceptably (although not perfectly) for all 4 triple-Raptor launches.

They're still going to need to get first stage recovery and reuse working soon or they'll likely be throwing away WAY too many Raptors per flight for it to be an acceptable cost method to achieve orbit for Starlink, though. But that doesn't require the super dynamic ignite-the-engines-while-still-sideways thing which seems to be where a lot of the problems happen (or at least show themselves).

If they can recover the first stage and achieve orbit most of the time, they'll be able to transition Starlink launches to Starship. That will give them a big advantage by no longer being purely a development cost.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: johnraid on 03/31/2021 03:21 am

Some potentially interesting observations and thoughts that someone might be able to build on-

- Framwork has 6 sides (60 degree spacing)
- The white floor is heavily built and has 36 Radial ribs (10 degree spacing)
- I'm thinking the floor rotates (its round, not hexagonal like everything else on the fixture and at Starbase)
- The black ring surrounding the white floor appears as if it may have degree wheel markings -may-


That sparked an idea.  I believe it's a fixture for installing studs for heat shield tiles on the nose.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Raptor42 on 03/31/2021 03:29 am
Prior to relight the three engines undertake a gimballing sequence with engine 3 stopping movement before 1 and 2. We then see engine 3 relight and begin to gimbal, in the opposite direction that you would expect for the flip, before the video freezes.

Its unclear whether this initial movement is intentional and is meant to occur before the engine gimbals in concert with the remaining engines (once they have started) in the required vector to actuate the flip. The same sequence does appear to occur in the video of SN10's flip (3-1-2 starting sequence with 3 intially gimballed away from the other 2 before joining them for the flip).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CJ on 03/31/2021 03:37 am
Per a post in the update thread, SpaceX has posted an update.

SpaceX site has updated.

Click through to get to the actual post, and the attached update.

What caught my eye was they say SN11 experienced a Rapid Unscheduled Dissasembly (RUD). That seems to weigh against the theory that the FTS triggered, IMHO.

So, other than the FTS, what failure modes could cause the sudden wide dispersion of parts that we saw? It would have to be quite an energetic event IMHO. Common bulkhead failure?




Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: _MECO on 03/31/2021 03:50 am
Per a post in the update thread, SpaceX has posted an update.

SpaceX site has updated.

Click through to get to the actual post, and the attached update.

What caught my eye was they say SN11 experienced a Rapid Unscheduled Dissasembly (RUD). That seems to weigh against the theory that the FTS triggered, IMHO.

So, other than the FTS, what failure modes could cause the sudden wide dispersion of parts that we saw? It would have to be quite an energetic event IMHO. Common bulkhead failure?
I mean, I suppose no one ever schedules in a time or date for using the FTS to blow up a big rocket...
One thing the failures have kind of made me reconsider is whether they'd have reuse going smooth before doing orbit.

It seems like they may end up doing like Falcon 9 and just going for orbit before reuse is working acceptably.

Remarkable that they have the manufacturing capacity to even contemplate that approach for a rocket the size of Saturn V and with "upper stages" comparable to stripped down Space Shuttle orbiters.

Ascent worked acceptably (although not perfectly) for all 4 triple-Raptor launches.

They're still going to need to get first stage recovery and reuse working soon or they'll likely be throwing away WAY too many Raptors per flight for it to be an acceptable cost method to achieve orbit for Starlink, though. But that doesn't require the super dynamic ignite-the-engines-while-still-sideways thing which seems to be where a lot of the problems happen (or at least show themselves).

If they can recover the first stage and achieve orbit most of the time, they'll be able to transition Starlink launches to Starship. That will give them a big advantage by no longer being purely a development cost.
If Elon says that SN15-SN2X are just for testing this maneuver, I would imagine they'd start nailing it. It seems a stretch that they would continue to screw this up five or seven more times in a row. And even if they do, why not start trying to do it after testing out orbit and atmospheric entry capability? It's more utility that way. Not like you get to use a Starship to test anything else after it's pancaked into the concrete or exploded.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oberonian on 03/31/2021 04:14 am
I found it interesting that the one engine on ascent appeared to be burning fuel rich giving the flame an orange colour. Right when the first engine shut down it briefly was burning blue but quickly turned orange again.

Coincidentally? it appeared to be in the same position as the engine on SN10 that also appeared to burn fuel rich, IIRC it was the same engine that had off nominal thrust during the static fire.

Do we know whether this was the engine 2 that Elon said had problems?

Was it norminal or nominal ?

 8)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FinalFrontier on 03/31/2021 05:29 am
Per a post in the update thread, SpaceX has posted an update.

SpaceX site has updated.

Click through to get to the actual post, and the attached update.

What caught my eye was they say SN11 experienced a Rapid Unscheduled Dissasembly (RUD). That seems to weigh against the theory that the FTS triggered, IMHO.

So, other than the FTS, what failure modes could cause the sudden wide dispersion of parts that we saw? It would have to be quite an energetic event IMHO. Common bulkhead failure?
Ignition of the CH4 inside the main tank or header tank.
Source would be either a fire in the repress AP line or a raptor exploding energetically enough to pop the aft bulkhead with heated shrapnel.

Still don't think this was it. Imho right now I still think it was FTS activation for vehicle off course due to failed engines/relight fail.But I rank the above scenerio as the "second most likely" candidate.



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 03/31/2021 05:30 am
One possible solution to the propellant sloshing/lack of propellant for re-start issue is to fabricate smaller tanks inside the larger ones at the bottom of each, with a check valve at bottom to allow the propellant in, but prevent it from coming out. That way when the main tanks are filled, the small tanks fill, but not drain out when turned about.

At the high points you connect your vents to purge to prevent over-pressurization.

Of course this all adds mass, which hurts performance, so it was probably discounted long ago. But a containment method inside the tanks seems to be the 'least complex' path (IMO) - similar to baffles but more restrictive (but they need to be able to be drained out or fed to the engines).

I'm a little surprised someone on this forum isn't aware,  but what you are describing is essentially the header tanks that have been part of the design of Starship since some of the earliest prototypes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 03/31/2021 06:16 am
They're disassembling the Sarens framework. I assume BN1 will be reverse built in the highbay so they won't need Ludicrous Transporter for a while.
Nomadd,

I hope you are kidding.  BN1 was never meant to be transported.  Why would they assemble this and disassemble it for BN1?  It was obviously for SN11, and that's why it won't be needed before SN15 flies.  It's to support an unstable Starship after landing until they can hook the crane to it.

Edit:  Can this thread get an FTS?  Thanks.
You might want to consider the possibility that you're not as smart as you think you are.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dante2121 on 03/31/2021 06:23 am
Did SpaceX launch in the dense fog to make a statement to the FAA - re About the silliness of being on site to “ watch” the launch?  :D :-X
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 03/31/2021 06:34 am
Did SpaceX launch in the dense fog to make a statement to the FAA - re About the silliness of being on site to “ watch” the launch?  :D :-X
Nothing to do with it. Vast majority of FAA's work will be pre-launch. You may think your comment is a bit humorous.  It is not.  Go back under your bridge please.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 03/31/2021 06:45 am
... BN1 was never meant to be transported.
False.  They need to transport BN1 for testing.
Quote
Why would they assemble this and disassemble it for BN1?
Because they need to transport BN1.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 03/31/2021 06:50 am
twitter.com/djsnm/status/1377124311119486977

Quote
So I looked at @RGVaerialphotos images of SN11 and there's just nothing left of the main tanks, like they've been shredded. In SN10 and other failures the top or bottom blew out and the tank remained. But this looks like it completely blew apart in flight. Only the nose remains.

https://twitter.com/djsnm/status/1377124311937343489

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I'm not an expert, I don't have inside info, but it seems to me that tearing apart the tanks like that would require either FTS activation or a rapid pressure rise inside the tanks. I keep hearing that FTS isn't to blame so that says to me that there was combustion inside tanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacexplorer on 03/31/2021 07:59 am

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.
;D ;D ;D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CJ on 03/31/2021 08:01 am
Per a post in the update thread, SpaceX has posted an update.

SpaceX site has updated.

Click through to get to the actual post, and the attached update.

What caught my eye was they say SN11 experienced a Rapid Unscheduled Dissasembly (RUD). That seems to weigh against the theory that the FTS triggered, IMHO.

So, other than the FTS, what failure modes could cause the sudden wide dispersion of parts that we saw? It would have to be quite an energetic event IMHO. Common bulkhead failure?
Ignition of the CH4 inside the main tank or header tank.
Source would be either a fire in the repress AP line or a raptor exploding energetically enough to pop the aft bulkhead with heated shrapnel.

Still don't think this was it. Imho right now I still think it was FTS activation for vehicle off course due to failed engines/relight fail.But I rank the above scenerio as the "second most likely" candidate.

According to those who've seen the debris pics (I'm not one of 'em, so I'm just going on the opinions of others here) the main tanks were pretty shredded. So, I think you're right that there was ignition of the CH4 inside the tank. The problem IMHO is, that'd also require O2. Maybe the LOX downcomer for the LOX header let go inside the CH4 tank? Or. the CH4 downcomer (or manifold) did so inside the LOX tank? I think you may be right regarding energetic failure of a Raptor.

My guess on the FTS issue is that if it was the FTS, SpaceX would know, and if they knew, they wouldn't be saying a RUD. Just tea-leaf reading on my part though.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 08:05 am
I doubt an explosion updraft will carry things up to 1-2km in altitude. I'd assume the highest they would get would be a few hundred meters. Don't forget to count the downward momentum of the vehicle as well added to the piece of insulation's velocity. The fire plume would have to counteract that as well.

The NWS radar image posted elsewhere shows the hot water vapor produced by combustion traveled much further than a a few hundred meters. Light fragments of COPV overwrap, Mylar film, etc. could easy be tossed much, much higher than a couple hundred meters by the detonation itself, then carried aloft further by updrafts and prevailing winds. If one or more of the COPVs liberated under pressure (which we have seen before many times with SpaceX RUDs), it could shed part or all of its overwrap along the way even further.

Oh for sure, but we're not talking about "light fragments of COPV overwrap or Mylar film". We're talking about somewhat hefty macroscopic pieces of insulation. They're light but they're not feather light, as I previously stated.

Just how heavy do you think a hand-sized fragment of COPY overwrap is? Or a similarly-sized fragment of Nomex cable wrap? That stuff is a few ounces at most and will literally float for miles in a stiff breeze. And it seems like SpaceX understands this, as they have created a Debris Hotline to call for people who find stuff.

We're not talking about COPV overwraps or nomex cable wrap.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 08:09 am
I agree with the sentiment that the flip turn is problematic, however I don't see that it is unsolvable.  Quick iteration obviously helps with this, but I think it hard to argue there is a trajectory of improvement since the first 10km flight.

As I understand it, there is not enough control authority from the aero surfaces to execute the pitch up maneuver, it requires the trust of the Raptors to fully rotate.  When I watch the pitch up sequence, I see the following:
1.  vehicle descending in level configuration at around T+6'28"
2.  2X Raptor ignition ( milliseconds apart) T+6'31"
3.  Aft "Elonerons" ( or whatever they are called) tuck in to minimum deflection at T+6'33"
4.  rapid pitch up & subsequent 4 straight failures.

What I wonder is why not initiate the minimum deflection of the aft "Elonerons" several seconds prior to engine ignition?  If the pitch up angle can be changed even 5 or 10 degrees, those few seconds can allow for a lot of liquid to calmly settle towards the baffles, & any bubbles also have opportunity to rise to the surface.
 
I think the forward control surfaces should be able to keep any roll moments under control when the aft move to minimum drag configuration.   The Raptor ignition is the most violent part of the sequence, but if done when the solution has already some opportunity to settle, it seems this favors a smoother start sequence.

The Starship doesn't have full control of all 6 degrees of freedom with only 4 control surfaces, notably horizontal motion is linked to pitch angles. If the vehicle pitches up it will also incur a horizontal translation and a horizontal increase in velocity, that would then also need to be countered by the engines. That increases the complexity of the control design. I'm sure as time goes on they'll further optimize the flight path for minimum fuel use (for example aim off pad so that engine startup will aim them back on to pad). Right now they have a lot of bigger problems on their plate than minor inefficiencies in the landing process.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Yggdrasill on 03/31/2021 08:15 am
My guess on the FTS issue is that if it was the FTS, SpaceX would know, and if they knew, they wouldn't be saying a RUD. Just tea-leaf reading on my part though.
I think it's possible they don't have the full telemetry data, and need to recover disks from the wreckage before being able to say more definitively what happened. And before they have the full picture, I can easily see they might just call it a RUD.

If it weren't for the fog they might be able to make a visual determination whether FTS activated.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/31/2021 08:31 am
During the spacex stream they showed a view from a tank. If something serius was happening before the flip they may know. If the tanks explosion cause presented during the flip, what could be that cause? A structural shock caused by a failed raptor ignition?Didthe tanks explode immediatly after the last frame or more after? In this case therecould be an explosion in raptor preburners, that propagated, like has been pointed out, in Main LOx tank, because the downcomer full of LCH4 was destroyed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 08:32 am
I don't really get why everyone is concentrating on the landing flip maneuver at all.  The problem here wasn't anything at all to do with the flip.  Engines that were already not operating correctly (Elon said chamber pressure didn't reach expected levels during ascent) failed to re-light.  They where in a phase of the flip which was absolutely optimal for engine relight - the first engine was supplying some "gravity", and they hadn't started to rotate quickly yet.  Fuel supply should have been a non-issue at that point.

To me, the thing I'm worried about (slightly) is raptor development, not the flip.  No matter how you land, raptor needs to be able to reliably relight.  At the moment, that seems to be proving much harder than expected.  We don't know if that's a fundamental issue with raptor's design, or if it's just a matter of tweaking until it works right.  The only "worrying" thing I see is that Elon was hoping that by raptor 50 they would be into mass production, and that's clearly not the case as of now, due to continuing issues with getting them to work reliably.  Hopefully that's just a small delay to full production.

Compeletely agree on the first part. Everyone seems to be concerned about the flip maneuver for some reason even though it was basically irrelevant to SN11's landing. The solution to buggy parts isn't to increase your margins until things work, it's to understand what exactly is happening with the different parts and fix them so that they perform to expectations, then the landing maneuver is fine. Right now the biggest issue is the Raptor engines, which we already know (and have seen in some photos) are vastly improved for SN15.


Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Once again nobody said anything about stop testing with Raptors... There is still much to be learned from EDL on the vehicle besides the engines...

So they would be using two completely different engine designs for the same rocket? Rockets aren't LEGOs. You're been here a long time and I don't understand why you would suggest such a thing. The entire point of a rocket testing program is to test the stuff that doesn't work, not try to test things that avoid the hard problems. Test the hardest things first (if you can). The hardest things that are available right now are Raptor engine reliability in flight so we need more testing of that, not less. (Arguably in-space refueling and the heat shield may be harder, but can't be tested yet.) Don't get too attached to the landing of the vehicle, that's trivial compared to the rest of the things they've already succeeded at and the major issues they still need to fix.


They're disassembling the Sarens framework. I assume BN1 will be reverse built in the highbay so they won't need Ludicrous Transporter for a while.
Nomadd,

I hope you are kidding.  BN1 was never meant to be transported.  Why would they assemble this and disassemble it for BN1?  It was obviously for SN11, and that's why it won't be needed before SN15 flies.  It's to support an unstable Starship after landing until they can hook the crane to it.

Edit:  Can this thread get an FTS?  Thanks.

Why did Elon say they were going to transport BN1 then? It was definitely planned to be transported previously and may still be transported before being scrapped, but that's unknown. Calm your hyperbole.

https://twitter.com/elonmusk/status/1372695421487824903



More tidbits
https://www.reddit.com/r/spacex/comments/mg914a/rspacex_starship_sn11_highaltitude_hop_discussion/gsv6qp9?utm_medium=android_app&utm_source=share&context=3
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SN46's gimbal failed. (You can see in the video that it doesn't gimbal with the other two engines, and starts flailing around when it lights). I'm also told the other 2 engines did not light, not clear why. N̶o̶t̶ ̶s̶u̶r̶e̶ ̶i̶f̶ ̶t̶h̶e̶ ̶e̶x̶p̶l̶o̶s̶i̶o̶n̶ ̶c̶a̶m̶e̶ ̶f̶r̶o̶m̶ ̶F̶T̶S̶ ̶o̶r̶ ̶s̶o̶m̶e̶t̶h̶i̶n̶g̶ ̶e̶l̶s̶e̶,̶ ̶b̶u̶t̶ ̶F̶T̶S̶ ̶m̶a̶k̶e̶s̶ ̶m̶o̶s̶t̶ ̶s̶e̶n̶s̶e̶ ̶c̶o̶n̶s̶i̶d̶e̶r̶i̶n̶g̶ ̶t̶h̶e̶ ̶c̶i̶r̶c̶u̶m̶s̶t̶a̶n̶c̶e̶s̶.̶

On the bright side, the last 3 flightworthy old design Raptors are pancakes now. SN15+ will feature the new and more reliable Raptors.

Edit: FTS not used. Not sure why it exploded, header tank or common dome might have popped after E3 ignition.

Seems completely wrong to me. To use their words "flailing" has happened every single engine relight and shut down this far. That person appears to be just guessing on things based on the videos same as anyone else. They don't appear to be an inside source.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edzieba on 03/31/2021 09:33 am
On the Sarens framework: Why do people expect it to be an either/or tool? Starship and Super Heavy have the same diameter, why would they build a rig that could not lift both if required? Install the Starship Mating Ring Shim for lifting Starship, Install the Super Heavy Mating Ring Shim when lifting Super Heavy.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 03/31/2021 09:40 am
BN1 was transported in the highbay. O.k. only a short distance.
And plans change, especially with EM and SX.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edzieba on 03/31/2021 10:01 am
From the RGV photos: the debris field is odd. Using the orientation of the resting nose as a guide, the field extends a significant distance linearly from the pad - along the axis of Boca Chica Bay - without all that much spread. The debris field stretches about 1km NNE from the landing pad, and about 300m from either side of that line, being widest either side of the pad and tapering as you go North. There is very little debris to the south of the pad. Raptors as pictured are next to Starhopper, the nose as pictured is right on the entry ramp, and everything else appears to have been thrown past them North of site.
I can't think of many ways for that to happen without having Starship be 'backsliding' towards the pad from the North-east while falling, the high energy event shatter the tank section into fragments but not impart much velocity to the nose or thrust structure, allowing those to continue on their trajectory towards the pad to rest there, while the fragments rapidly lose their lateral velocity and descend 'straight down' over the debris field.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MTom on 03/31/2021 10:26 am
Let's lighten up a bit.

How many explosions does it take that a norminal Everyday Astronaut turns into an Angry Astronaut ?

 ???

Why should he do?
For him - and for many others like me - seeing this developmentprogram is very interesting.

Every month an explosion or every month only waiting and nothing happens - what would you choose?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Bogeyman on 03/31/2021 11:00 am
I rather have 5 Starships exploding than nothing happening at all at BO...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 03/31/2021 11:06 am
Would the current prototypes have flight data recorders(Black Boxes)? Do F9/Dragon?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: laserguy on 03/31/2021 11:09 am
snip...
I think it's possible they don't have the full telemetry data...

That's what I'm thinking. Extended loss of video feed from all the cameras points to a communications problem, rather than a hardware issue with a specific camera.

More importantly, SpaceX embeds their video feed as specific data packets inside of their telemetry data downlink (at least for Falcon 9), see -

https://www.r00t.cz/Sats/Falcon9 (https://www.r00t.cz/Sats/Falcon9)

Here is a recent video by Scott Manley about the wonderful work by some amateur radio operators figuring this out -

https://www.youtube.com/watch?v=74_N163HyhA (https://www.youtube.com/watch?v=74_N163HyhA)

In this arrangement, an extended, complete loss of video feed would likely be accompanied by an extensive loss of data telemetry.

This could also explain Elon's odd tweet, saying that "something significant happened", but they wouldn't know what until after they physically examined the debris -

https://twitter.com/elonmusk/status/1376891464333017090 (https://twitter.com/elonmusk/status/1376891464333017090)

----------

Also worth noting that early last week, an amateur radio enthusiast in the Boca Chica area was able to successfully receive the radio signal from the then-grounded SN11, analysis of which revealed it had a similar format to Falcon 9. However, a similar attempt on Friday revealed that everything is now encrypted!

Apparently, someone at SpaceX (same guy who didn't like LabPadre's cam?) got miffed that ham radio operators were able to receive video from their spacecraft, so they locked-down SN11 a few days ago.

Ironically - depending on how they did it - this sudden rush to encrypt the entire downlink from the spacecraft just a few days before flight could have caused or contributed to the loss of video and/or data telemetry during SN11's fateful foggy flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 03/31/2021 11:19 am
Seems completely wrong to me. To use their words "flailing" has happened every single engine relight and shut down this far. That person appears to be just guessing on things based on the videos same as anyone else. They don't appear to be an inside source.
You didn't know much about nextspaceflight it seems like
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edzieba on 03/31/2021 11:43 am
On telemetry: dropout of video has little bearing on telemetry availability. Different communications channels, different bandwidth requirements, different frequencies, etc.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: pachavaillaz on 03/31/2021 11:52 am
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: eriblo on 03/31/2021 12:01 pm
On telemetry: dropout of video has little bearing on telemetry availability. Different communications channels, different bandwidth requirements, different frequencies, etc.
They also stated during the stream that they still had telemetry when the video was out. It might be that the mission timer shown is derived from telemetry as John said "...as you can see from the frozen view, we lost the clock at 5:49...".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KSC Sage on 03/31/2021 12:08 pm
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
That won't work on Mars or the moon.  They need to make the flip and landing a powered landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 03/31/2021 12:10 pm
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
That won't work on Mars or the moon.  They need to make the flip and landing a powered landing.


Also little to no control even on Earth.  You're basically pulling the rip cord and praying. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 03/31/2021 12:18 pm
With all this discussion about the flip and landing modes going to add a couple things here.
There isn't (really) a giant technical difficulty or unknown with this landing method. The only thing maybe that might need to change is how rapidly the vehicle pivots to vertical, possibly use a slower rate. And/or doing this flip at a higher altitude and burning the engines longer for better stability and slower deceleration rates and forces.
...
I suspect there are a number of unknowns about the landing and a few technical difficulties as well. Slowing the rate of flip will require more propellant and must be weighed against adding additional hardware in the tanks when it comes to stabilizing the liquids. What happens inside the starship tanks is far more complex than a quick review of the process might reveal.

One big problem is that Starships operate far from equilibrium. There are two cryogenic liquids with different boiling points stored with a common bulkhead, both of which have been subcooled, both slowly warming and being pressurised with gases whose pressure and temperature varies during the flight due to autogenous pressurization.

The autogenous pressurisation gases themselves are also not at equilibrium. The temperatures and pressures at the tap off points in the Raptor engine will be a lot higher than those of the gases close to the cryogenic liquid surfaces with a pressure/temperature gradient across the pipes and headspaces.  The headspace volume and surface area will be expanding and sloshing cryogenic liquids may well condense gases in the headspace causing further pressure variation and pressure pulses.

Just to complicate matters further this structure is the size of a block of flats (scaling issues) and is subject to variable accelerations in 3 dimensions which may well affect the liquid surface area (slosh, waves, splash and droplets etc).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 03/31/2021 12:30 pm
...

The "Mystery Structure" has a nosecone lifted inside its cage, potentially to be used as a test rig.

I stared hard at this structure with the intent of mind forcing it to be a chomper articulation development fixture but I can't come close to making it fit into that box.

Some potentially interesting observations and thoughts that someone might be able to build on-

- Framwork has 6 sides (60 degree spacing)
- The white floor is heavily built and has 36 Radial ribs (10 degree spacing)
- I'm thinking the floor rotates (its round, not hexagonal like everything else on the fixture and at Starbase)
- The black ring surrounding the white floor appears as if it may have degree wheel markings -may-
- With that hexagonal opening in the floor and hole in the nose it seems access to the interior is important to them. 
- Perhaps going to use this to hold nose while they build mock up interior?
- Perhaps a safe stable way to hold a nose with interior mock up in all wind conditions without blowing over while they have some people live in it for a while.
Is it a turntable for Superheavy so that it can be rotated in the high bay for welding , access or whatever?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jim on 03/31/2021 12:31 pm
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
That won't work on Mars or the moon.  They need to make the flip and landing a powered landing.

They won't be doing this on the moon.  It enters sideways for aerodynamic reasons, which doesn't apply on the moon.

it would work on Mars, but SpaceX is not going to want to use a parachute.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jim on 03/31/2021 12:33 pm
Would the current prototypes have flight data recorders(Black Boxes)? Do F9/Dragon?

No, telemetry
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dynamic-lizard on 03/31/2021 01:05 pm
Maybe it's a mystery flight conditions simulator, but then, why would they put there a header tank-less version :(

Wysłane z mojego G8141 przy użyciu Tapatalka

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 03/31/2021 01:19 pm
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
The release and flip process would simply take too long with a ballute or parachute and while the Starship is being slowly pulled upright it will also be accelerating downwards and would then take longer to slow down with the Raptors costing more propellant.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 03/31/2021 01:24 pm
SN15's tank section just headed out of the Mid-bay and its nose was stacked recently.  Looks like all the parts are heading over to the High-bay.  Maybe we will get to see the new bridge crane in action!  Hopefully all the tankerazi are in place when that lift happens.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 03/31/2021 01:25 pm
I had some thoughts on the mystery structure that the nose cone is in:

At the moment the BN1 rocket is too high for the nose cone to be stacked in the high bay, and possibly with any crane available in the area. Perhaps they need to put it in position on a platform to raise it higher? Or perhaps they risk damage due to winds in the area with the existing attachment points at the top of the nose cone being so close together, so they are spreading the load further out with the steel structure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mandrewa on 03/31/2021 01:50 pm
Once again, the wind at altitude was westerly as seen in the attached 12:00 UTC Brownsville radiosonde (from meteocentre.com (http://meteocentre.com/radiosonde/get_sounding.php?stn=72250&type=rs&yyyy=2021&mm=03&dd=30&run=12&hist=0&show=0&lang=en&area=us)). The radar only shows a low level plume (check the estimated "Echo Tops" of ~10000 ft) that is blown out to sea once it rises.

[EDIT] Corrected wind direction.

Thanks for this.  I don't know how to read the chart, although part of it seem obvious.  The vertical line second to the right with the little flagpoles on it shows the direction and strength of the wind at different altitudes. 

One of the questions I had was how that piece of insulation ended up on San Pedro Island.  I had thought that maybe it had fallen from the skirt much earlier in the flight.  But this wind map implies that's unlikely.  For 3 km and above the wind was not blowing in the direction of San Pedro Island.  It's only from 2 km and below that the wind is blowing in the direction of San Pedro Island.

It seems hard to believe that a piece of insulation that started at 1 km or thereabouts could have blown 8 km.

The point I take from your comment about the plume seen on the radar is that this is not a debris field.  This is the hot gases rising into the air (from the conflagration) and being blown out almost to the east and from the wind map the hot gases would have been at roughly 2.7 km when the radar image was taken.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 03/31/2021 01:53 pm
Okay here is a header tank mod that might help the problems of mixing of hot autogen with subcooled liquid prop.

As an aside you can see the ullage "bubble" has to move from dorsal to top of rocket when the flip occurs. It would probably be good to remove the slosh baffles in the path of this "bubble" move.

EDIT: also my pic is missing the caption on the top diagram. It should say "sky dive".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dgkimpton on 03/31/2021 01:59 pm
I had some thoughts on the mystery structure that the nose cone is in:

At the moment the BN1 rocket is too high for the nose cone to be stacked in the high bay, and possibly with any crane available in the area. Perhaps they need to put it in position on a platform to raise it higher? Or perhaps they risk damage due to winds in the area with the existing attachment points at the top of the nose cone being so close together, so they are spreading the load further out with the steel structure.
Not sure about the nose cone, but is it conceivable they are using a nose cone as a simulator for a full starship and we are looking at a prototype of the stacking jig that will be used to attach second-stages to first-stages? Mating the two on the pad 80+m off the ground is going to be a challenge without some sort of craneable jig.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mihai78 on 03/31/2021 02:14 pm
A question about the 10km test flight envelope. My impression is that the attempts so far basically tweaked the moments before and during the landing while not significantly changing the whole ascending phase. Would it make sense (maybe after a successful landing) to gain more data by varying that one as well? As an extreme example, what about a (shorter) 3-raptor burn to reach supersonic speed and test aerodynamic deceleration back to subsonic while still going upwards? Could be useful as a booster abort simulation. The trajectory could join the current one at the end to still test the landing. More data per prototype.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 03/31/2021 02:18 pm
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chevvie on 03/31/2021 02:31 pm
Because there is no flip, they dont need header tanks.
They settle the fuel by short RCS bursts before lighting the engines.

Not sure about your 2nd question.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pete on 03/31/2021 02:37 pm
Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

Storing hot gas under pressure is *silly*.
You just greatly increase the pressure and material requirements for the storage system, and as soon as it exits it **will** be cold again. Gas Laws, y'all.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pete on 03/31/2021 02:45 pm
OK, now this is just sad:

To see such magnificent examples of precision engineering as the Raptors turned into..... ROADKILL

https://twitter.com/RGVaerialphotos/status/1377044636951314436

Quote
RIP Raptors, they almost landed on Starhopper!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 03/31/2021 02:45 pm
Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

Storing hot gas under pressure is *silly*.
You just greatly increase the pressure and material requirements for the storage system, and as soon as it exits it **will** be cold again. Gas Laws, y'all.

I am thinking about the ~1 second before the autogen gas gets going. Also when in space they will need to pressurize to 6bar before mars edl or moon edl. I would assume during transit it makes sense to reduce pressure some since this would cool the liquid to vapor/liquid equilibrium.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/31/2021 02:57 pm
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
That won't work on Mars or the moon.  They need to make the flip and landing a powered landing.



They won't be doing this on the moon.  It enters sideways for aerodynamic reasons, which doesn't apply on the moon.

it would work on Mars, but SpaceX is not going to want to use a parachute.
edit: fixed quote

Parachutes are heavy, and to return to Earth from mars
a big parashute capable of turning SS is very heavy, and you would need to re store it to return to Earth (if it works on mars, and I'm not sure, because Mars atmosphere is 1% Earths's). I am working with parachutes for a water rocket project. Folding them is a nightmare even  at small scales (mine has diameter = 1.5 m)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: watermod on 03/31/2021 03:05 pm
If they took the BN-1, after all the planned fitting and pressure checks, then added the older discontinued raptor motors and shot it high over the gulf they could gather data to see how well it could do a boost-back burn and then vertically dump it in the ocean.    That should give correlation data to F9 boosters.
 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThereIWas3 on 03/31/2021 03:14 pm
Another problem with a parachute is that you can only use it once.  A mission to Mars and return has to do a flip-landing twice.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 03/31/2021 03:15 pm
Why not initiate the flip by ejecting a ballute and/or parachute from the nose (lop nose anyone?)?
That won't work on Mars or the moon.  They need to make the flip and landing a powered landing.

The flaps won't work on the moon and it's questionable if they were work on Mars.  A parachute would work better for the flip than the flaps.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 03/31/2021 03:22 pm
If they took the BN-1, after all the planned fitting and pressure checks, then added the older discontinued raptor motors and shot it high over the gulf they could gather data to see how well it could do a boost-back burn and then vertically dump it in the ocean.    That should give correlation data to F9 boosters.
 

They can probably model that to a very high accuracy anyway.  May as well put the hours of time, effort and launch pads into other vehicles or just have the site free for orbital launch mount construction.

I want to see BN fly too, we'll be there soon, very soon.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsnellenberger on 03/31/2021 03:41 pm
Blunt nose has been moved into the mystery structure.
I’m beginning to think that the mystery structure might be an assembly jig/fixture to make it easier and safer to precisely align the two halves of a BNx during assembly.

As well as those little “welding fingers” have worked when aligning ring sections for the shorter (& lighter)  Starship sections, getting those two long tanks aligned and welded would be simpler with a large “third hand” available to hold the upper tank in position. Assuming that the platform is removable, alignment guides between the structure and tank would allow them to lift the aligned tank (to remove the platform) and drop it back down to be welded without losing alignment.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: deadman1204 on 03/31/2021 03:42 pm
Another problem with a parachute is that you can only use it once.  A mission to Mars and return has to do a flip-landing twice.

I don't think a parachute being involved with a Mars landing is a terrible idea. Think of it like a consumable - similar to fuel.
There also won't be the situation where starship takes off from mars and then lands there again. By the time something like that happens, we won't be on v1 of starship so the design with a parachute will be old anyways.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 03/31/2021 03:46 pm
Do you guys realize how big the parachute would have to be on Mars to have any effect on SS at all? Look at how big Perseverance’s was, and that rover is tiny and light compared to Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 03/31/2021 03:47 pm
Do you guys realize how big the parachute would have to be on Mars to have any effect on SS at all? Look at how big Perseverance’s was, and that rover is tiny and light compared to Starship.

We're not asking it to slow the vehicle down significantly, just turn it vertical.  So not that big at all.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BigDustyman on 03/31/2021 03:49 pm
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?


probably only need maybe 8 captors to push empty starship to orbit
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 03/31/2021 03:53 pm
Do you guys realize how big the parachute would have to be on Mars to have any effect on SS at all? Look at how big Perseverance’s was, and that rover is tiny and light compared to Starship.

We're not asking it to slow the vehicle down significantly, just turn it vertical.  So not that big at all.


How big would it have to be?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 03/31/2021 04:00 pm
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 03/31/2021 04:00 pm
Do you guys realize how big the parachute would have to be on Mars to have any effect on SS at all? Look at how big Perseverance’s was, and that rover is tiny and light compared to Starship.

We're not asking it to slow the vehicle down significantly, just turn it vertical.  So not that big at all.


How big would it have to be?

I don't know, but probably not even the diameter of the ship.  In fact, it wouldn't surprise me if Perseverance's chute would be plenty.  It just has to apply torque and it's got a long moment arm.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 03/31/2021 04:17 pm
Do you guys realize how big the parachute would have to be on Mars to have any effect on SS at all? Look at how big Perseverance’s was, and that rover is tiny and light compared to Starship.

We're not asking it to slow the vehicle down significantly, just turn it vertical.  So not that big at all.


How big would it have to be?

I don't know, but probably not even the diameter of the ship.  In fact, it wouldn't surprise me if Perseverance's chute would be plenty.  It just has to apply torque and it's got a long moment arm.
"The parachute, which is 70.5 feet (21.5 meters) in diameter, deploys about 240 seconds after entry, at an altitude of about 7 miles (11 kilometers) and a velocity of about 940 mph (1,512 kph)."


It took a parachute more than twice Starship's diameter to slow Perseverance  enough for the skycrane. Starship is a LOT larger than Perseverance. I somehow doubt "not even the diameter of the ship" would work.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 03/31/2021 04:24 pm
Do you guys realize how big the parachute would have to be on Mars to have any effect on SS at all? Look at how big Perseverance’s was, and that rover is tiny and light compared to Starship.

We're not asking it to slow the vehicle down significantly, just turn it vertical.  So not that big at all.


How big would it have to be?

I don't know, but probably not even the diameter of the ship.  In fact, it wouldn't surprise me if Perseverance's chute would be plenty.  It just has to apply torque and it's got a long moment arm.
"The parachute, which is 70.5 feet (21.5 meters) in diameter, deploys about 240 seconds after entry, at an altitude of about 7 miles (11 kilometers) and a velocity of about 940 mph (1,512 kph)."


It took a parachute more than twice Starship's diameter to slow Perseverance  enough for the skycrane. Starship is a LOT larger than Perseverance. I somehow doubt "not even the diameter of the ship" would work.


"We're not asking it to slow the vehicle down significantly, just turn it vertical. "
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: laserguy on 03/31/2021 04:41 pm
On telemetry: dropout of video has little bearing on telemetry availability. Different communications channels, different bandwidth requirements, different frequencies, etc.
Take a closer look at my post (including the first link) - they were digitizing their video into data telemetry packets, & then transmitting it with the rest of the data telemetry. Same frequency, same channel, downlink bandwidth was shared with all the other data telemetry.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: abaddon on 03/31/2021 04:56 pm
How about folks who want to talk about their own alternate spaceship that isn't Starship create a new thread rather than using "Texas Prototype(s) Discussion" which is talking about actual SpaceX prototypes that don't have, e.g., parachutes.  Please?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 03/31/2021 05:19 pm
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John

So for the SH there will not be a need for COPV's with propellant gas(fuel and oxidizer)?
How about the slight delay of maybe a second before autogen gas starts flowing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 05:20 pm
"The parachute, which is 70.5 feet (21.5 meters) in diameter, deploys about 240 seconds after entry, at an altitude of about 7 miles (11 kilometers) and a velocity of about 940 mph (1,512 kph)."


It took a parachute more than twice Starship's diameter to slow Perseverance  enough for the skycrane. Starship is a LOT larger than Perseverance. I somehow doubt "not even the diameter of the ship" would work.


"We're not asking it to slow the vehicle down significantly, just turn it vertical. "

Parachutes isn't relevant to this thread. Create a new thread if you want to talk about parachutes on Starship please.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 05:25 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Haur on 03/31/2021 05:38 pm
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John

So for the SH there will not be a need for COPV's with propellant gas(fuel and oxidizer)?
How about the slight delay of maybe a second before autogen gas starts flowing?

Given that the SH tanks have significant head pressure when full and even when at flight levels still have a fair degree of ullage volume, that should not be an issue.

The Starship methane header tank pressure issues are a combination of both a small initial ullage volume and the high degree of mixing caused by the slosh, as well as a limited head pressure requiring gaseous pressurisation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 03/31/2021 05:53 pm
The flip is fraught with frightening features, but SpaceX's Russian "admirers" have already suggested the solution when it comes to Earth landings.

That's right, a trampoline
Okay, maybe not a trampoline: you'd bounce right off, (unless you have a capture system to grab the Starship right as it hits 0 velocity)?
So instead, an inflatable stunt cushion like movies use for stunt work. A really big one. Even on the airless moon, that could work, just fill it with hydrogen electrolyzed from the ice there. 

A big stunt cushion, to be sure, and hella strong if it is going to catch a Starship falling at 40 meters per second (which I guesstimate to be terminal velocity of a horizontal Starship on Earth).  But at least SpaceX has proven that Starship can accurately land in the middle  of the cushion: "The crater was in the right place."

Now, for the Moon and Mars: obviously you have to land a robotic stunt cushion deploying system there before you can use this method there.  And your Starship lunar landings will have to use a way other than aerodynamic drag to slow down, but gravity is less, so less of a challenge. And you'll want an erector crane as well, I would think, to lift the Starship off the cuchion and into a vertical launch position.  All doable.

And really, is it much crazier than the flip and burn maneuver?
I think your almost onto something. Close but no cigar. The cushion would need a small pop off valve exiting into a tube open to ambient. This is to control rebound. The proper acoustic effects would be lost on the moon. On earth and mars a good landing would sound off with a resounding fwupppp p p p, and a great WHOOPIE! from the crew.  :o


I'll see myself out.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 03/31/2021 05:58 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Haur on 03/31/2021 06:02 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

Fairly sure the header tanks cannot be pressurised with the engine autogenous supplies currently. The lines from the engines running up the side of the rocket only go to the main tanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 03/31/2021 06:08 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

In LEO they will need to vary the pressure to transfer fuel between ships. So one tank will be low on pressure.

Also when doing the transit to other places there will be varying pressure needs. The James Webb telescope at L2 with a shade reaches a temp of 50K. At that temp there is no need for gas reliquification. I think they will reduce the temp for the transit to keep the propellants cool then repressurize before mars or moon EDL. In this ways the raptors are consuming propellant at a known temp and pressure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 03/31/2021 06:26 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

Fairly sure the header tanks cannot be pressurised with the engine autogenous supplies currently. The lines from the engines running up the side of the rocket only go to the main tanks.

There is photos of SN8-10 junk and you can see a thin line going to the top of the methane header.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 03/31/2021 06:33 pm
Bingo - the time to be actually worried about landing is when they're trying to build a fleet of 1000 of them to go to mars that need to land on mars reliably, and they're still not nailing them all.

As of today - this is a non issue.  SN15 will go up higher and faster, test something else, and if it makes it back down, it'll have *another* go at landing.  That's fine.  Eventually they'll figure out how to get it right.
Parallel development with higher & faster on one track, and fixing the flip on the other, makes sense.


We know they can lift 200m, translate 200m and kinda land. What if they were to lift 2km, switch to headers, then tip over ~30deg, bring it back upright, then land. Swap out the legs and do it again but higher and 60deg. Again with 90deg. Hit the problem from the bottom up instead of from the top down, so to speak.


Yes, I know, test like you fly, and they won't fly this way. But, they do need to get over this hump and top down is all or nothing plus cleanup. With bottom up they can edge into the problem using one ship - until they find the bottom edge. Then, well maybe they'll need another ship.


In the meantime they've got two pads and it's also time to crank up higher & faster.


Just an idea.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Haur on 03/31/2021 06:36 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

Fairly sure the header tanks cannot be pressurised with the engine autogenous supplies currently. The lines from the engines running up the side of the rocket only go to the main tanks.

There is photos of SN8-10 junk and you can see a thin line going to the top of the methane header.
Which goes up into the nose barrel where the COPVs are.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 03/31/2021 06:41 pm
I know they can go straight up and straight down and not seem to have a problem.  The belly flop flip seems to slosh around the fuel and lox and then getting the engines to restart. 

I also noticed they don't flip until 1km altitude.  Maybe starting at 2km altitude and give the fuel and lox and engines enough time to adjust. 

Don't know, but maybe fly a full up Starship as high as it can go, then do the belly flop slower, then move upright slower, to eliminate some sloshing, then land. 

I know Musk is also pushing the limits on what pressures the engines can operate at.  I know he wants 225-250 tons thrust.  Maybe 200 is safer all the time for now. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 03/31/2021 06:52 pm
Using Merlins at this point avoids the main weak point in Starship that needs the MOST development, which is reliable air restarts of the Raptor in "exotic" attitudes.  The flip itself and guidance algorithms seem fine.
Merlin has not been tested under the flip conditions, with all the associated likely wild propellant slosh.  No guarantee it would work.

 - Ed Kyle
I agree Ed no guarantee which is reasonable and I gave you a like. What the Merlins do offer are reliability and a operational flight history. From your own excellent site and historian of LVs I'm reminded of that wonderful "kludge workhorse" the Saturn S-1B. Even though it had nothing to do with the required S-IVB for the Moon landing it allowed for the program to continue development and testing of the spacecraft in orbit. Oddly enough it's usefulness allowed it outlive the Saturn V for the ASTP...
I actually was going to mention a re-engine before this failure but held off... Maybe start a dedicated thread for anyone interested...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 03/31/2021 06:56 pm
https://youtu.be/MoEv0dkWlvA
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 03/31/2021 07:16 pm


I have just watched his video. There isn't nothing new beside what we saw yesterday, but Scott explains very well that.IMO a  possible explanation for a energetic failure of tank is an explosion in raptor preburner(s), but there isn't nothing to support that (as far as I know ).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sevenperforce on 03/31/2021 07:31 pm

I have just watched his video. There isn't nothing new beside what we saw yesterday, but Scott explains very well that.IMO a  possible explanation for a energetic failure of tank is an explosion in raptor preburner(s), but there isn't nothing to support that (as far as I know ).
Complete speculation: ground debris damage or some other unanticipated external factor caused a leak in Engine 2's cold fuel manifold coming from the methane turbopump outlet, causing a fire. It burned for quite a while (since Engine 2 was the second to be cut off) which weakened the associated piping considerably.

https://twitter.com/thesejustwords/status/1376904137317699587

At relight, Engine 2's weakened cold fuel manifold suffered a catastrophic failure and fragged the other two engines, leading to a thrust shortfall and a commanded FTS trigger.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vonbraun on 03/31/2021 07:39 pm
If the pressure within tank got somehow under 1 atm (or almost to it), then the flame front could advance backwards trough the pipes.

Valve malfunction between header and main tanks?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: testguy on 03/31/2021 07:49 pm
Not that I have any say in the matter, but I generally give SX the benefit of doubt when it comes to scheduling.  That is because I so want them to achieve those goals.  However, I’m somewhat surprised that no one has posted comments about the tweet from Elon that established a goal of having BN 2 on the orbital stand with engines by the end of April. For all practical purposes this is April.  I’m afraid that is a bridge way too far even for SX.  We have seen very little of BN 2 components and we know there will be design changes.  The support infrastructure has a long way to go before any checkouts.  The launch pad itself is a ways off even for fit checks.  The launch tower/crane is just coming out of the ground. 

Setting schedule goals that are difficult, not impossible, to achieve is a wonderful management tool to drive the schedule.  I often used it myself.  Without it schedules will just flounder.  Setting goals that are just impossible will have a negative effect on employees since they believe no matter how hard they try they are not achievable, so why even try.

Perhaps SX just wants to get BN 2 on the pad for preliminary fit checks while all the construction will continue around it.  I would like nothing more than to see BN 2 on the orbital pad with infrastructure completed or nearly completed by the end of April.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: testguy on 03/31/2021 07:51 pm
If the pressure within tank got somehow under 1 atm (or almost to it), then the flame front could advance backwards trough the pipes.

Valve malfunction between header and main tanks?
Check valves anyone?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 03/31/2021 07:53 pm
Per a post in the update thread, SpaceX has posted an update.

SpaceX site has updated.

Click through to get to the actual post, and the attached update.

What caught my eye was they say SN11 experienced a Rapid Unscheduled Dissasembly (RUD). That seems to weigh against the theory that the FTS triggered, IMHO.

So, other than the FTS, what failure modes could cause the sudden wide dispersion of parts that we saw? It would have to be quite an energetic event IMHO. Common bulkhead failure?
I mean, I suppose no one ever schedules in a time or date for using the FTS to blow up a big rocket...
One thing the failures have kind of made me reconsider is whether they'd have reuse going smooth before doing orbit.

It seems like they may end up doing like Falcon 9 and just going for orbit before reuse is working acceptably.

Remarkable that they have the manufacturing capacity to even contemplate that approach for a rocket the size of Saturn V and with "upper stages" comparable to stripped down Space Shuttle orbiters.

Ascent worked acceptably (although not perfectly) for all 4 triple-Raptor launches.

They're still going to need to get first stage recovery and reuse working soon or they'll likely be throwing away WAY too many Raptors per flight for it to be an acceptable cost method to achieve orbit for Starlink, though. But that doesn't require the super dynamic ignite-the-engines-while-still-sideways thing which seems to be where a lot of the problems happen (or at least show themselves).

If they can recover the first stage and achieve orbit most of the time, they'll be able to transition Starlink launches to Starship. That will give them a big advantage by no longer being purely a development cost.
If Elon says that SN15-SN2X are just for testing this maneuver, I would imagine they'd start nailing it. It seems a stretch that they would continue to screw this up five or seven more times in a row. And even if they do, why not start trying to do it after testing out orbit and atmospheric entry capability? It's more utility that way. Not like you get to use a Starship to test anything else after it's pancaked into the concrete or exploded.
I think because they don't expect to nail reentry for awhile. See earlier post about parallel testing.


They need to nail the flip to stick the landing. They need stick the landing to verify/develop the legs. They need the legs to figure out final(?) engine bay layout.


Sequential testing would take too long.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 03/31/2021 08:34 pm
If the pressure within tank got somehow under 1 atm (or almost to it), then the flame front could advance backwards trough the pipes.

Valve malfunction between header and main tanks?
Check valves anyone?

If it’s the regenerative pressure system, pressure would be higher than tank pressure by definition. The issue is that there shouldn’t be enough oxygen left in the regen feed to cause combustion or explosion in the main methane tank. But...what if there was excess oxygen in the regen feed going to the methane tank? Cue The Martian “making water I almost blew myself up” sequence.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: I14R10 on 03/31/2021 08:34 pm
Does anybody know why launch tower and launch pad (orbital) are not in line?

https://twitter.com/RGVaerialphotos/status/1377279458621714437/photo/1
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 03/31/2021 08:46 pm
Why would they be in line?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: I14R10 on 03/31/2021 08:49 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 03/31/2021 08:54 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?
I've got a sneaking suspicion that while the base is square, the launch tower that's going to rise up from it might be cylindrical.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Frogstar_Robot on 03/31/2021 08:59 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?

Because it doesn't matter in the slightest. Not everyone is OCD.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Crispy on 03/31/2021 09:13 pm
Does anybody know why launch tower and launch pad (orbital) are not in line?

https://twitter.com/RGVaerialphotos/status/1377279458621714437/photo/1
Two points are, by definiton, on a line :D
The walls might not be parallel, but that doesn't matter.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lawlessl on 03/31/2021 09:14 pm
Does anybody know why launch tower and launch pad (orbital) are not in line?

They could be in line. One is the exact location of the stack. The other is to the side of the stack. It needs to be offset. The fly over on the 14th March #967 at 7:55 shows the alignment.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 03/31/2021 09:15 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?

Because you want exhaust deflected by the ground to hit a corner not a flat?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: geza on 03/31/2021 09:20 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?

May I suggest a reason. Above I asked, why a steal tower would need such a huge above ground concrete base. A part of the answer was that the lowest section of the tower will be hit by exhaust gases and cooling water. Assume now, that the rectangular base is "in line". Then the exhaust hits the wall of the base perpendicularly. In contrast, if the edge of the rectangular base points to the launch pad, as it seems to be the case, the exhaust hits in 45 degree, which is much better.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 10:04 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

Elon didn't say anything about replacing helium pressurant with COPVs. Tanks pressurize naturally just sitting there, what's what all the venting is about on the pad, venting pressure building up too high. You only need autogenous pressurization when you're actively draining the tanks, namely when the engines are running. The tanks are pressurized multiple times atmospheric pressure. I'm not sure why this discussion is happening. Perhaps some people are missing some key details about how Starship works.

Let's please not act like known facts are somehow suddenly unknown. It only confuses the discussion.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 10:08 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

In LEO they will need to vary the pressure to transfer fuel between ships. So one tank will be low on pressure.

Also when doing the transit to other places there will be varying pressure needs. The James Webb telescope at L2 with a shade reaches a temp of 50K. At that temp there is no need for gas reliquification. I think they will reduce the temp for the transit to keep the propellants cool then repressurize before mars or moon EDL. In this ways the raptors are consuming propellant at a known temp and pressure.

In LEO they don't need to lower the pressure at all to pump fuel between ships. In fact you want relatively high pressures in both tanks to feed the pumps. As you pump fuel over the pressure will go down in the tank you're pumping from anyway as you draw a vacuum on the tank. They may even choose to have a gas return line to let the gas from one tank return to the tank being pumped from to maintain the pressure difference between the tanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacevalley27 on 03/31/2021 10:10 pm
Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic) on SN15?

Photo by Jack Beyer for NSF, from twitter (sorry, don't know how to put the link without the preview being shown  :-\ )
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 03/31/2021 10:12 pm
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John

So for the SH there will not be a need for COPV's with propellant gas(fuel and oxidizer)?
How about the slight delay of maybe a second before autogen gas starts flowing?

Could have them for purges and spin starts, but it would make more sense to have high pressure gases as part of ground support equipment, since the SH only launches for its launch pad.

John
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 10:14 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?

Maybe because it fits on the property line better and gives them more space for other things? The crane will rotate. Doesn't really matter what angle it's at.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 03/31/2021 10:18 pm
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.

- RCS system needs high pressure COPVs for GOx and GCH4.  Purging and spin start also need high pressure gases. Why not use the same COPVs you already have on board? My only question is whether they will also need GN2 for purging. I'm sure they don't want Helium.

John
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 03/31/2021 10:24 pm
Why would they be in line?

It seems logical. Why would they be at some arbitrary angle?

Because you want exhaust deflected by the ground to hit a corner not a flat?

Also, because if you're going to hang 200 tons off the side of the tower, you want it to be hanging in the direction where the tower is strongest, which is likely across the diagonal.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GetCrispy on 03/31/2021 10:33 pm

Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic)

Hmm, I wonder if it’s an access portal of some kind to the “fairing” section of the vehicle? Somewhat analogous to the weld-on access cover to the CH4 tank (below and left in the image).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 03/31/2021 10:36 pm
Guys, the Launch Tower discussion belongs in the Launch Site thread: https://forum.nasaspaceflight.com/index.php?topic=49086.3460
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mlindner on 03/31/2021 10:47 pm
https://twitter.com/SpacePadreIsle/status/1377388053220704257

That's the SN11 engine skirt isn't it? That looks crazy far from the pad where the engine debris are.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: illectro on 03/31/2021 11:05 pm
So, I am now pretty sure, based on RGV's photos that the Methane header tank is in two halves, top half landed next to the pad, lower half landed across the road in the bay. We've never seen the tank fail like that on previous flights, in SN10 it was still spherical after being expelled out the bottom of the tank at high speed.
So, I'm thinking the explosion started inside there?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thechungster on 03/31/2021 11:15 pm
Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic) on SN15?

Photo by Jack Beyer for NSF, from twitter (sorry, don't know how to put the link without the preview being shown  :-\ )

Some wild speculation here but the centre white circle has a diameter of ~60cm.
Coincidentally, a Starlink user terminal is around the same diameter...  ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zeekakboos on 03/31/2021 11:54 pm
https://www.liebherr.com/en/int/products/mobile-and-crawler-cranes/crawler-cranes/lr-crawler-cranes/lr-13000.html

The most powerful crane in the world with a maximum lifting capacity of 3300 USt / 3000 t.
With the maximum boom system of 394 ft / 120 m main boom and 413 ft / 126 m luffing jib
I believe the recently delivered crane is an LR-1300
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: vaporcobra on 03/31/2021 11:56 pm
https://www.liebherr.com/en/int/products/mobile-and-crawler-cranes/crawler-cranes/lr-crawler-cranes/lr-13000.html

The most powerful crane in the world with a maximum lifting capacity of 3300 USt / 3000 t.
With the maximum boom system of 394 ft / 120 m main boom and 413 ft / 126 m luffing jib

One number off... ;) It's an LR1300. But this conversation should be in the discussion thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nicom26 on 04/01/2021 12:13 am

Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic)

Hmm, I wonder if it’s an access portal of some kind to the “fairing” section of the vehicle? Somewhat analogous to the weld-on access cover to the CH4 tank (below and left in the image).

It looks like the mystery thing is just welded on to the outside of SN15, while the access hatches are actual cutouts in the tank walls, so that seems unlikely--but who knows!

Or maybe it's a light to help us see it if it launches in the fog? /s
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bfabry on 04/01/2021 12:17 am
Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic) on SN15?

Photo by Jack Beyer for NSF, from twitter (sorry, don't know how to put the link without the preview being shown  :-\ )

Some wild speculation here but the centre white circle has a diameter of ~60cm.
Coincidentally, a Starlink user terminal is around the same diameter...  ???

Huh. It looks like at least part of it is a white plastic cover which does a little bit yell "radio!".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aero on 04/01/2021 12:53 am
SN 11 was the one that fell over in the high bay, wasn't it? You don't suppose it suffered undetected internal damage leading to the explosion do you?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hartspace on 04/01/2021 12:58 am
SN 11 was the one that fell over in the high bay, wasn't it? You don't suppose it suffered undetected internal damage leading to the explosion do you?
SN9 was the one that tipped over in the high bay
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Steve G on 04/01/2021 01:00 am
Wouldn't I like to be the owner of the local scrap metal company.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/01/2021 01:20 am
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.
Where to store ullage makeup gas? Both places IMO. When the launch burn starts ullage pressure can be on the low side as the pressure head is high. Ullage pressure need be only high enough to meet structural needs. As the fuel level drops along with the pressure head feeding the engines, the ullage pressure needs to rise to compensate.


Unfortunately, the autogen makeup gasses are warm and will shrink when contacting the densified propellants. Storing in a high pressure COPV gives at least a few moments to let it cool if the COPV's aren't in the engine bay. The gasses will further cool as they drop to ullage pressures but my unsupported WAG is they'll still be warm in comparison to the props. They will condense and the solution is to pile on more makeup gas.


As an ideal, makeup gasses would enter the COPV at a low temp so that full pressure is available later in the flight for other systems needing methane pressure. This would keep the COPV volume low. It would also minimize shrinkage as the gas contacts the chilled propellant in its ullage role. So much for ideals.


Temperature and pressure will be doing their codependent dance everywhere throughout every system. It's so complicated it makes my blood Boyle.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/01/2021 01:41 am
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John

So for the SH there will not be a need for COPV's with propellant gas(fuel and oxidizer)?
How about the slight delay of maybe a second before autogen gas starts flowing?

Given that the SH tanks have significant head pressure when full and even when at flight levels still have a fair degree of ullage volume, that should not be an issue.

The Starship methane header tank pressure issues are a combination of both a small initial ullage volume and the high degree of mixing caused by the slosh, as well as a limited head pressure requiring gaseous pressurisation.
Where did this come from? If anything, initial SH ullage pressure will be low. IMO. The engines are picky about inlet pressure. That big tall SH will have a high head pressure at launch. Only enough ullage pressure to keep it from buckling.


Actually we're both working in a knowledge vacuum. The one and only SH in the whole world is not a flight article. Even Elon only knows what his plans are, not what he will actually end up doing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FinalFrontier on 04/01/2021 01:47 am
Per a post in the update thread, SpaceX has posted an update.

SpaceX site has updated.

Click through to get to the actual post, and the attached update.

What caught my eye was they say SN11 experienced a Rapid Unscheduled Dissasembly (RUD). That seems to weigh against the theory that the FTS triggered, IMHO.

So, other than the FTS, what failure modes could cause the sudden wide dispersion of parts that we saw? It would have to be quite an energetic event IMHO. Common bulkhead failure?
Ignition of the CH4 inside the main tank or header tank.
Source would be either a fire in the repress AP line or a raptor exploding energetically enough to pop the aft bulkhead with heated shrapnel.

Still don't think this was it. Imho right now I still think it was FTS activation for vehicle off course due to failed engines/relight fail.But I rank the above scenerio as the "second most likely" candidate.

According to those who've seen the debris pics (I'm not one of 'em, so I'm just going on the opinions of others here) the main tanks were pretty shredded. So, I think you're right that there was ignition of the CH4 inside the tank. The problem IMHO is, that'd also require O2. Maybe the LOX downcomer for the LOX header let go inside the CH4 tank? Or. the CH4 downcomer (or manifold) did so inside the LOX tank? I think you may be right regarding energetic failure of a Raptor.

My guess on the FTS issue is that if it was the FTS, SpaceX would know, and if they knew, they wouldn't be saying a RUD. Just tea-leaf reading on my part though.
Took awhile for the folks on a certain infamous Titan IV failure to finally come to terms with the fact that their AFTS malfunctioned and to verify the telemetry and failure mode. Similar things on other rockets in the not so distant past as well. Sometimes it's very hard to tell if an FTS activated or not especially if it was a malfunction triggered activation and it can sometimes be even harder to accept that fact if so.

So I am still skeptical about this not being some form of FTS activation.

But with that said it's becoming more likely it was ignition in the methane tank. As far as O2 content you just need to get to LEL% LFL to have combustion. Not much O2 is needed. A very small leak in the LOX downcomer or O2 getting in through one of the cold gas thruster or tank vent through hulls would be enough.
So the question becomes what was the ignition source.
IMHO was either raptor engine 2 exploding or perhaps even worse, engine two exploding and sending a flash front up the AP pressurizer line into the tank. This could also have happened without any raptor issue and instead a simple fire occurring inside that line.
We had a fire in the vacinity of this line as well as the main fuel return valve from the chamber coolant visible in the video footage on the bad engine, which suggests a crack or failure of some kind.
Having looked at the video a few more times I think this was a contributing factor in some way but I don't know exactly how yet, that is something hopefully SpaceX figures out and tells us.

Regarding the LOX downcomer. Yes it is also possible that the pipe itself failed explosively during landing burn startup. This would have caused a rapid over pressurization of the CH4 tank as all of the LOX pressure in the LOX header tank was instantly dumped into the CH4 tank. This would likely also cause ignition and you'd get a big explosion and many small bits.
So this is also a possibility. Causes of this could include again, a fire in one of the AP pressurizer lines coming off the engines or a failure of raptor engine 2 that caused a a significant back pressure event and a pressure "kick" back up the LOX manifold into the line. Either of these would cause the downcomer pipe to rupture and the rest is as we saw.

All of these are possibilities and what is challenging is they all would happen extremely extremely fast. Perhaps not quite as fast as the COPV explosion and carbon fiber ignition on AMOS-6 but still very fast.
In tank over pressure and combustion events are very difficult to dissect afterwards because they happen extremely fast and the exact behavior inside when it's happening is difficult to model and often unique case by case.

We will see what they come up with. If it was a pressurizer line fire a check valve or flame arrestor is probably an easy fix here. If it was a pressure kick back up the line some kind of emergency relief valve or burst disk might be an easy fix for that.




Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: vaporcobra on 04/01/2021 02:06 am
Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic) on SN15?

Photo by Jack Beyer for NSF, from twitter (sorry, don't know how to put the link without the preview being shown  :-\ )

My post fell through the cracks (https://forum.nasaspaceflight.com/index.php?topic=53361.msg2212710#msg2212710) during the late FAA inspector furor 😅 I'm still very curious, too. Much better photos from Mary during SN15's high bay move today, thankfully!

Have to admit that my first thought was a Starlink dish, as the location makes no sense for a window test. If not Starlink, some other kind of flat-panel antenna, or possibly an EMR-transparent 'window' for some other kind of communications equipment.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/01/2021 02:15 am
The white plastic thing is a new telemetry antenna. The older little ones are missing anyway. But it is not Starlink, probably the same s-band encoded up/downlink for telemetry and video feed that they have been using and was picked up by hijackers not long ago. The similarity with a starlink dish may not be coincidence tho, it could be very well based on the phased array antenna technology they already have been mass producing.

I do hope that this new antenna will give a better video downlink.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: vaporcobra on 04/01/2021 03:02 am
The white plastic thing is a new telemetry antenna. The older little ones are missing anyway. But it is not Starlink, probably the same s-band encoded up/downlink for telemetry and video feed that they have been using and was picked up by hijackers not long ago. The similarity with a starlink dish may not be coincidence tho, it could be very well based on the phased array antenna technology they already have been mass producing.

Hmmm, good call, as it turns out! Looks to be roughly the same size as what I believe is Falcon 9 S1's main antenna, minus the enclosure/box around Starship's. Booster pictured is B1061.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CardBoardBoxProcessor on 04/01/2021 03:05 am
The brief look inside of SS was the methane tank. Isn't liquid methane clear and colorless but we see it looking cloudy? What would it look like when mixed O2
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/01/2021 03:07 am
The brief look inside of SS was the methane tank. Isn't liquid methane clear and colorless but we see it looking cloudy? What would it look like when mixed O2
It's a great sign of autogenous pressurization, because helium wouldn't make such a visual effects because of much less saturation. Also a gaseous methane in this tank is still very close to liquid temperature, thus creating a fog when in contact with liquid methane
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/01/2021 03:37 am
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KilroySmith on 04/01/2021 03:53 am
If I were building a FTS system, I’d make sure that the explosive elements had a transmitter built into them, to make finding them after an accident a bit easier.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CJ on 04/01/2021 03:59 am
The brief look inside of SS was the methane tank. Isn't liquid methane clear and colorless but we see it looking cloudy? What would it look like when mixed O2
It's a great sign of autogenous pressurization, because helium wouldn't make such a visual effects because of much less saturation. Also a gaseous methane in this tank is still very close to liquid temperature, thus creating a fog when in contact with liquid methane

Hrmmm. If the vapor inside the CH4 tank is indeed close to liquid temp, then could it be possible that, during the start of the flip, there was liquid slosh, causing a recondensation of some of the vapor, resulting in a pressure drop and a common dome failure?



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: laserguy on 04/01/2021 04:17 am
So, I am now pretty sure, based on RGV's photos that the Methane header tank is in two halves, top half landed next to the pad, lower half landed across the road in the bay. We've never seen the tank fail like that on previous flights, in SN10 it was still spherical after being expelled out the bottom of the tank at high speed.
So, I'm thinking the explosion started inside there?

Where is that split, in relation to the location of the FTS?

I know some sources are swearing that the FTS was not triggered - but what if some fault caused the FTS to fire accidentally? Maybe even a defect in the FTS itself?

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/01/2021 04:26 am
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...

They do have a lot of personnel out recovering wreckage. They also warned that though the road was open, not to leave it. It is possible they have recovered, or are looking for UXBs.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sanman on 04/01/2021 05:04 am
What are the key improvements in SN15 over SN11 and other previous prototypes?

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Star One on 04/01/2021 07:16 am
What are the key improvements in SN15 over SN11 and other previous prototypes?
I don’t think anything has been said about the specifics so far other than there is hundreds of them.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Haur on 04/01/2021 08:06 am
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John

So for the SH there will not be a need for COPV's with propellant gas(fuel and oxidizer)?
How about the slight delay of maybe a second before autogen gas starts flowing?

Given that the SH tanks have significant head pressure when full and even when at flight levels still have a fair degree of ullage volume, that should not be an issue.

The Starship methane header tank pressure issues are a combination of both a small initial ullage volume and the high degree of mixing caused by the slosh, as well as a limited head pressure requiring gaseous pressurisation.
Where did this come from? If anything, initial SH ullage pressure will be low. IMO. The engines are picky about inlet pressure. That big tall SH will have a high head pressure at launch. Only enough ullage pressure to keep it from buckling.


Actually we're both working in a knowledge vacuum. The one and only SH in the whole world is not a flight article. Even Elon only knows what his plans are, not what he will actually end up doing.

I believe that's what I said. SH has relatively high head pressure from 30/60m of propellants, so a lack of gas pressure when lighting at launch isn't as much of an issue - but even then there's a non-trivial quantity of ullage volume which will not significantly lose pressure due to expansion before the autogenous supply kicks in. And when they want to relight for the landing burn, you've now got a 90+% empty tank at a reasonable pressure so probably doesn't even need any make-up pressurant supply - although since it's there anyway, might as well use it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pete on 04/01/2021 09:22 am
Hrmmm. If the vapor inside the CH4 tank is indeed close to liquid temp, then could it be possible that, during the start of the flip, there was liquid slosh, causing a recondensation of some of the vapor, resulting in a pressure drop and a common dome failure?
Yes, yes, no.

What you are describing is known as "Ullage Collapse".
It is a very well known phenomena. It is especially likely if the cryogenic liquid is supercooled.(or the ullage gas is superheated)
It was also the most likely cause of Sn8's fuel pressure problem.

It *does* reduce tank pressure.
It is highly unlikely that this reduction of pressure will be enough to cause a bulkhead collapse. The Starship would be designed to accommodate this, and indeed it is likely one of the significant hurdles they are working on in the test program.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Interro on 04/01/2021 09:50 am
I'm trying to work out what this means. I'm thinking either they:
  -  Increased the fuel/oxidiser mass for SN10/11
  -  Throttled the Raptors lower for SN10/11

I would have also expected some more variance between SN8 and SN9, given the 2.5km difference in maximum altitude.

https://twitter.com/BocaCharts/status/1377384970910531584/photo/1 (https://twitter.com/BocaCharts/status/1377384970910531584/photo/1)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/01/2021 09:59 am
What are the key improvements in SN15 over SN11 and other previous prototypes?
According to Elon there's hundreds of improvements but the biggest one that we know of is the new thrust puck design. Also it's supposed to use a new generation of Raptor engines. I'm not really sure if there's any changes in steel thickness...

(IIRC there was a discussion that they started building SN15 with 3mm steel before a 3mm test tank(SN7.2) went trough pressure testing... I might be wrong about that tho, I have a bad memory so maybe someone else knows better.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: denisjc on 04/01/2021 10:26 am
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...

There will be nothing left of the FTS, even if this was a Raptor or Tank detonation once that has happend the FTS will also detonate.  This is the nature of expolsives.  So in effect once the explosion started the FTS would follow.

It is called Sympathetic detonation.  As the explosive in the FTS is basicaly just Primacord it would detonate once the pressure wave hits it.  Not that it would do much at that point, as the pressure wave is already way into the RUD.  :o
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Paul_G on 04/01/2021 10:38 am
In the most recent update video, we can see the flat nose cone in the mystery structure having the previously seen white metal structures attached. Is it likely these are low fidelity flap substitutes that they can then apply test loads to. The main mystery structure would stabilise the nose cone, whilst being able to apply loads to the flaps - perhaps simulating re-entry loads?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Haur on 04/01/2021 10:48 am
What are the key improvements in SN15 over SN11 and other previous prototypes?
According to Elon there's hundreds of improvements but the biggest one that we know of is the new thrust puck design. Also it's supposed to use a new generation of Raptor engines. I'm not really sure if there's any changes in steel thickness...

(IIRC there was a discussion that they started building SN15 with 3mm steel before a 3mm test tank(SN7.2) went trough pressure testing... I might be wrong about that tho, I have a bad memory so maybe someone else knows better.)
Pretty much all of the SN15 tank sections were spotted between November and mid December, whereas the 3mm stuff for 7.2 didn't show up until the end of December.

If there is any 3mm on SN15, the most likely place is the nosecone/barrel, but even these don't exibit the flimsiness seen with the 7.2 rings.

It also appears that the 3mm rings are a new serial range. 7.2 used rings 003, 005 and 008. The parts of SN15 with visible ring labels used rings in the ~600-700's.

But anyway, there's the new lifting points in the nosecone as well, an additional pipe running down the raceway, the mystery new antenna, and probably dozens of others that won't be visible. The new Raptor generation looks so much nicer combined with the new thrust puck - just optimising the external ancillary plumbing will likely have a big impact there too, and I'm sure they've made internal adjustments as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/01/2021 11:07 am
In the most recent update video, we can see the flat nose cone in the mystery structure having the previously seen white metal structures attached. Is it likely these are low fidelity flap substitutes that they can then apply test loads to. The main mystery structure would stabilise the nose cone, whilst being able to apply loads to the flaps - perhaps simulating re-entry loads?

We also know Elon has mentioned they may try and "catch" starship for landing instead of landing legs...maybe the rig will be used to aid in testing loads on the flaps if used as the "catch point" ?   
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sebk on 04/01/2021 11:33 am
- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

What's the source on SS needing COPVs for GOx and GCH4? I highly doubt that's going to be required. More likely IMO, as it's going to be needed for refueling on Mars and long stationary stays on orbit or on Lunar surface anyway, is a liquefaction system on board to reliquify the Oxygen and Methane.


It's needed for initial pressurization of tanks before autogenous pressure take over. Elon admitted that using helium was a mistake and caused helium to enter the engine. Best solution is to pressurize with the same fuel you are using, especially in a dynamic environment where there is the opportunity to slosh and bubble. Also, you don't want to have to come up with uncommon elements on Mars. Use the same stuff to pressurize on Mars as you use for fuel.

In LEO they will need to vary the pressure to transfer fuel between ships. So one tank will be low on pressure.

Also when doing the transit to other places there will be varying pressure needs. The James Webb telescope at L2 with a shade reaches a temp of 50K. At that temp there is no need for gas reliquification. I think they will reduce the temp for the transit to keep the propellants cool then repressurize before mars or moon EDL. In this ways the raptors are consuming propellant at a known temp and pressure.

In LEO they don't need to lower the pressure at all to pump fuel between ships. In fact you want relatively high pressures in both tanks to feed the pumps. As you pump fuel over the pressure will go down in the tank you're pumping from anyway as you draw a vacuum on the tank. They may even choose to have a gas return line to let the gas from one tank return to the tank being pumped from to maintain the pressure difference between the tanks.

You actually want to lower the receiving tank pressure significantly.

You then don't need pumps. You use pressure difference to pumping for you. And you are also achieving thermal conditioning of the propellants at the same time: by lowering the pressure you also lower boiling point.

Yes, this would cause some propellant losses by venting stuff to space. But this lines so well with SpaceX philosophy: the best part is no part (no pumps, propellant conditioning achieved at the same time).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/01/2021 11:43 am
What are the key improvements in SN15 over SN11 and other previous prototypes?
According to Elon there's hundreds of improvements but the biggest one that we know of is the new thrust puck design. Also it's supposed to use a new generation of Raptor engines. I'm not really sure if there's any changes in steel thickness...

(IIRC there was a discussion that they started building SN15 with 3mm steel before a 3mm test tank(SN7.2) went trough pressure testing... I might be wrong about that tho, I have a bad memory so maybe someone else knows better.)
Pretty much all of the SN15 tank sections were spotted between November and mid December, whereas the 3mm stuff for 7.2 didn't show up until the end of December.

If there is any 3mm on SN15, the most likely place is the nosecone/barrel, but even these don't exibit the flimsiness seen with the 7.2 rings.



A while ago there was a discussion about this, maybe 3mm is used from sn16/17
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BZHSpace on 04/01/2021 11:54 am
What are the key improvements in SN15 over SN11 and other previous prototypes?
According to Elon there's hundreds of improvements but the biggest one that we know of is the new thrust puck design. Also it's supposed to use a new generation of Raptor engines. I'm not really sure if there's any changes in steel thickness...

(IIRC there was a discussion that they started building SN15 with 3mm steel before a 3mm test tank(SN7.2) went trough pressure testing... I might be wrong about that tho, I have a bad memory so maybe someone else knows better.)

I think most of the changes we have on the SN15 compared to the previous version (SN08 to SN11) are about avionic parts, engine, software and communication those change are about making the Starship more maneuvrable and to have a more optimized engine runing especially during the landing phase. We haven't any confirmation from Elon Musk about the steel thickness change (from 4mm to 3mm) but maybe this change is integrated yes on the SN15. I really look foward how this changes will impact the SN15's performance.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/01/2021 12:10 pm
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...

There will be nothing left of the FTS, even if this was a Raptor or Tank detonation once that has happend the FTS will also detonate.  This is the nature of expolsives.  So in effect once the explosion started the FTS would follow.

It is called Sympathetic detonation.  As the explosive in the FTS is basicaly just Primacord it would detonate once the pressure wave hits it.  Not that it would do much at that point, as the pressure wave is already way into the RUD.  :o
Not true..  it is far from their nature...  Even when military planes crash, which can be easily as violent, the bombs survive.

So unless the FTS was designed to self-trigger (but not accidentally!) It's hard to guarantee.

A sustained fire will melt the explosives, possibly causing them to burn without detonating.

But if the charge box got knocked away, with or without a piece of tank skin, then it is a (small) piece of unexploded ordnance, in an unknown state.

How much risk it poses is unknown, but this being a public beach, it is super important to locate it. It is highly unlikely to be "really" dangerous, but it's still formally a bomb.

So yeah, some ruggedized beacon embedded in it, as well as a ruggedized case, would make it highly likely that it will be found.



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: fuzzout on 04/01/2021 12:27 pm
I think it's quite important to look at where the pieces landed... I personally in my own very uneducated opinion think that FTS did trigger, but telemetry didn't get sent out quick enough.

To extrapolate on the above:
I'm going to use Starhopper and Landing pad as reference points; the nosecone landed on the corner of the landing pad entrance, facing the Starhopper (potentially backflipped after the blast). The raptors landed closer to starhopper; giving me the notion that SN11 was pointing away from Hoppy.
Looking at where the engines and legs landed + where the nosecone landed - I suspect it was off course, considering that the flight corridor shrinks towards the landing pad (obviously I'm just guessing this part) it is likely that FTS kicked in to prevent a prototype slamming into the side of a road + near some SpaceX hardware/shelters/containers.

Also worthy of note - using the direction of engine+nosecone locations - the blast came out of the left side of the vehicle (which could further offset where the engine/nose sections would land) - I guess the blast side based on where the majority of SN11 pieces flew out to.

So to summarize my own opinion and thoughts to a few words:
SN11 approached the landing pad and was off-course towards the road; the FTS kicked in - seemingly detonating on the right inside of the starship, causing the propellant to blow everything towards the (at the time) starships left side.

Also an interesting observation: The first engine that relit was pointing towards the ground (wouldn't that make the vehicle nosedive?), which to me seems very fishy.

Note: I'm not very mathematical and majority of what I wrote seems logical to me personally (even if somewhat uninformed at parts).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 04/01/2021 12:31 pm
The more I’ve reviewed what we do know, (speculation follows) the more convinced I am that SN-11 was a Raptor fuel pre-burner / autogenous pressurization system failure that led to measurable (non-trace) levels of oxygen in the methane tank,  perhaps even during the ascent as well as the relight, but during the relight either a heat event /spark happened through the autogenous line, or more likely the hot O2/methane gas mix of the malfunctioning Raptor went from 1/3 to all of the gas coming in ( because the malfunctioning Raptor started first) and because it was high in oxygen was burning even as it entered the already mixed O2-methane gas in the header / methane main tank.
Since it would be a detonation (not conflagration) initially contained by the header tank at the bottom of the methane tank, but then propagating supersonically through the top of the methane tank as well, it explains the strange linear distribution of top of the SS debris to the north where the top of SN-11 was pointing while debris originating from below the header mostly stayed relatively put or went south.

If this scenario is born out in data SpaceX has, it would be indication that some major safeties are needed relating to methalox autogenous pressurization— high oxygen condition /autogenous pressure sensors on methane autogenous system and high methane condition on the GOX autogenous system. Not just for Starship either, Blue Origin should take note for New Glenn since it uses autogenous as well. This happening on a fully fueled booster only a few feet in the air would be a major kaboom.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/01/2021 12:43 pm
I have a question:
How do they manage ullage in f9, main tanks of SS, SH?
Is it because there is no violent flip and slosh?
Do they calculate how much ullage they should "waste" to keep propellant pressures in correct range?
After all they are subcooling to fit more propellant in and then they have to waste some of that for ullage.

Second question:
Is it better to store hot ullage gas in your tanks at 6 bar or in copv's at much more bar?
I guess the answer is no part is the best part.

- The Falcon 9 uses helium to fill the ullage space in the tanks. The helium is stored at high pressure in COPVs immersed in the LOx tank to increase helium density.  I believe the helium is warmed (~250 F) through a heat exchanger before entering the tanks through a regulator and distribution system situated around the top of the tanks. Note the conflicting requirements for the ullage gas. It wants to be cold for high density storage, but needs to be warm for low density ullage filling.

- The SH uses warm gases, GOx and GCH4 (~500 F) tapped off of the Raptor engines to fill the ullage space in the tanks. The gases enter the tanks through a regulator and distribution system situated around the top the tanks. Note, this is similar to the Space Shuttle autogenous system.

- The SS is more complicated. It requires feeding engines from main and header tanks and after extensive time (minutes to months) between starts. To do this SS requires COPVs for both GOx and GCH4. Also, these COPVs probably have to be recharged from on board liquid propellants during extended missions. Ullage pressure of both sets of tanks need to be managed throughout the mission. COPVs will be part of the system which manages tank pressures whenever the Raptors are not firing. We again have a conflict between ullage gas COPV storage temperature and ullage filling temperature. Since there is no ready heat source with the Raptors off, a compromise temperature will probably be used (~100 F ?).

- Ullage pressure changes with changes in temperature. It has to be actively managed.

John

So for the SH there will not be a need for COPV's with propellant gas(fuel and oxidizer)?
How about the slight delay of maybe a second before autogen gas starts flowing?

Given that the SH tanks have significant head pressure when full and even when at flight levels still have a fair degree of ullage volume, that should not be an issue.

The Starship methane header tank pressure issues are a combination of both a small initial ullage volume and the high degree of mixing caused by the slosh, as well as a limited head pressure requiring gaseous pressurisation.
Where did this come from? If anything, initial SH ullage pressure will be low. IMO. The engines are picky about inlet pressure. That big tall SH will have a high head pressure at launch. Only enough ullage pressure to keep it from buckling.


Actually we're both working in a knowledge vacuum. The one and only SH in the whole world is not a flight article. Even Elon only knows what his plans are, not what he will actually end up doing.

I believe that's what I said. SH has relatively high head pressure from 30/60m of propellants, so a lack of gas pressure when lighting at launch isn't as much of an issue - but even then there's a non-trivial quantity of ullage volume which will not significantly lose pressure due to expansion before the autogenous supply kicks in. And when they want to relight for the landing burn, you've now got a 90+% empty tank at a reasonable pressure so probably doesn't even need any make-up pressurant supply - although since it's there anyway, might as well use it.
You said what you meant
You meant what you said
And it all got changed
Up in my head


My bad bro
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 04/01/2021 12:45 pm
In the most recent update video, we can see the flat nose cone in the mystery structure having the previously seen white metal structures attached. Is it likely these are low fidelity flap substitutes that they can then apply test loads to. The main mystery structure would stabilise the nose cone, whilst being able to apply loads to the flaps - perhaps simulating re-entry loads?
Probably ascent because the beefy stand will simulate the thrust of the tank section.  Force will also be applied to the flattened nose tip to see what the payload section can take before failure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/01/2021 02:57 pm
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...

There will be nothing left of the FTS, even if this was a Raptor or Tank detonation once that has happend the FTS will also detonate.  This is the nature of expolsives.  So in effect once the explosion started the FTS would follow.

It is called Sympathetic detonation.  As the explosive in the FTS is basicaly just Primacord it would detonate once the pressure wave hits it.  Not that it would do much at that point, as the pressure wave is already way into the RUD.  :o
Not true..  it is far from their nature...  Even when military planes crash, which can be easily as violent, the bombs survive.

So unless the FTS was designed to self-trigger (but not accidentally!) It's hard to guarantee.

A sustained fire will melt the explosives, possibly causing them to burn without detonating.

But if the charge box got knocked away, with or without a piece of tank skin, then it is a (small) piece of unexploded ordnance, in an unknown state.

How much risk it poses is unknown, but this being a public beach, it is super important to locate it. It is highly unlikely to be "really" dangerous, but it's still formally a bomb.

So yeah, some ruggedized beacon embedded in it, as well as a ruggedized case, would make it highly likely that it will be found.

Looking at those little charges, and the need to stay stable through some pretty rough conditions, I would have guessed something like Comp B, which is extremely hard to set off accidentally. They have to use 1/4 pound sticks of TNT for fuses in artillery rounds. (not in this case obviously, since the explosive would be no more stable than the fuse) I'm just guessing, but it seems like a lower velocity explosive like that would be more suited to disassemble a spaceship tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/01/2021 03:08 pm
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...

There will be nothing left of the FTS, even if this was a Raptor or Tank detonation once that has happend the FTS will also detonate.  This is the nature of expolsives.  So in effect once the explosion started the FTS would follow.

It is called Sympathetic detonation.  As the explosive in the FTS is basicaly just Primacord it would detonate once the pressure wave hits it.  Not that it would do much at that point, as the pressure wave is already way into the RUD.  :o
Not true..  it is far from their nature...  Even when military planes crash, which can be easily as violent, the bombs survive.

So unless the FTS was designed to self-trigger (but not accidentally!) It's hard to guarantee.

A sustained fire will melt the explosives, possibly causing them to burn without detonating.

But if the charge box got knocked away, with or without a piece of tank skin, then it is a (small) piece of unexploded ordnance, in an unknown state.

How much risk it poses is unknown, but this being a public beach, it is super important to locate it. It is highly unlikely to be "really" dangerous, but it's still formally a bomb.

So yeah, some ruggedized beacon embedded in it, as well as a ruggedized case, would make it highly likely that it will be found.

Looking at those little charges, and the need to stay stable through some pretty rough conditions, I would have guessed something like Comp B, which is extremely hard to set off accidentally.  I would have guessed. They have to use 1/4 pound sticks of TNT for fuses in artillery rounds. (not in this case obviously, since the explosive would be no more stable than the fuse) I'm just guessing, but it seems like a lower velocity explosive like that would be more suited to disassemble a spaceship tank.
Heh you know your stuff better than I do...  I just used them...

So yeah, just by virtue of being engineered to not go off on a launch environment, they're damn resilient.

But being bombs, they also have a triggerable detonation chain.

It'd be much easier if it fell in the ocean 50 miles off shore...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/01/2021 03:16 pm


Elon didn't say anything about replacing helium pressurant with COPVs. Tanks pressurize naturally just sitting there, what's what all the venting is about on the pad, venting pressure building up too high. You only need autogenous pressurization when you're actively draining the tanks, namely when the engines are running. The tanks are pressurized multiple times atmospheric pressure. I'm not sure why this discussion is happening. Perhaps some people are missing some key details about how Starship works.

Let's please not act like known facts are somehow suddenly unknown. It only confuses the discussion.

Depends on the temperature of the liquid.
https://en.wikipedia.org/wiki/Methane_(data_page)#Vapor_pressure_of_liquid
Basically the definition of subcooling is that at the given pressure the liquids vapor pressure is lower than that pressure. Therefore there will be no venting.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: kuldan on 04/01/2021 03:17 pm
The more I’ve reviewed what we do know, (speculation follows) the more convinced I am that SN-11 was a Raptor fuel pre-burner / autogenous pressurization system failure that led to measurable (non-trace) levels of oxygen in the methane tank

snipped to the relevant parts: Question that came to me is, if an accidental mixing of LOX/CH4 is bad (well duh)..would it be possible/make sense to pipe the header tank pipe that is on the inside of the tank wall on the outside? That pipe looks a bit flimsy compared to the usual downcomers, is that a potential failing point under aero loads?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/01/2021 03:55 pm
Elon didn't say anything about replacing helium pressurant with COPVs. Tanks pressurize naturally just sitting there, what's what all the venting is about on the pad, venting pressure building up too high. You only need autogenous pressurization when you're actively draining the tanks, namely when the engines are running. The tanks are pressurized multiple times atmospheric pressure. I'm not sure why this discussion is happening. Perhaps some people are missing some key details about how Starship works.
Let's please not act like known facts are somehow suddenly unknown. It only confuses the discussion.
Depends on the temperature of the liquid.
https://en.wikipedia.org/wiki/Methane_(data_page)#Vapor_pressure_of_liquid
Basically the definition of subcooling is that at the given pressure the liquids vapor pressure is lower than that pressure. Therefore there will be no venting.
Thank you for your polite and informative response. Mine was going to be a lot more deletable. Like this one.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/01/2021 04:04 pm
The more I’ve reviewed what we do know, (speculation follows) the more convinced I am that SN-11 was a Raptor fuel pre-burner / autogenous pressurization system failure that led to measurable (non-trace) levels of oxygen in the methane tank,  perhaps even during the ascent as well as the relight, but during the relight either a heat event /spark happened through the autogenous line, or more likely the hot O2/methane gas mix of the malfunctioning Raptor went from 1/3 to all of the gas coming in ( because the malfunctioning Raptor started first) and because it was high in oxygen was burning even as it entered the already mixed O2-methane gas in the header / methane main tank.
Since it would be a detonation (not conflagration) initially contained by the header tank at the bottom of the methane tank, but then propagating supersonically through the top of the methane tank as well, it explains the strange linear distribution of top of the SS debris to the north where the top of SN-11 was pointing while debris originating from below the header mostly stayed relatively put or went south.

If this scenario is born out in data SpaceX has, it would be indication that some major safeties are needed relating to methalox autogenous pressurization— high oxygen condition /autogenous pressure sensors on methane autogenous system and high methane condition on the GOX autogenous system. Not just for Starship either, Blue Origin should take note for New Glenn since it uses autogenous as well. This happening on a fully fueled booster only a few feet in the air would be a major kaboom.

So from speculative diagrams of raptor we have.
The methane is heated enough for autogen by the pass through the engine bell.

The oxygen on the other hand needs to be passed through a heat exchanger in the turbine section of the preburner. So if the heat exchanger got a hole in it then possibly partially burned oxygen could get in the regen line for the oxygen.

Conversely for the methane side a hole some place in the bell or CC could allow partially burned gas into the methane coolant circuit.

Not sure about all the pressure differentials that would need to be just right for this to work.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/01/2021 04:13 pm
Speaking of FTS, if it wasn't activated, wouldn't we be seeing the bomb squad and dogs searching the wetlands?

How DO they handle a missing explosive device?  This is obviously something that's been addressed before.

hmmm...

There will be nothing left of the FTS, even if this was a Raptor or Tank detonation once that has happend the FTS will also detonate.  This is the nature of expolsives.  So in effect once the explosion started the FTS would follow.

It is called Sympathetic detonation.  As the explosive in the FTS is basicaly just Primacord it would detonate once the pressure wave hits it.  Not that it would do much at that point, as the pressure wave is already way into the RUD.  :o
That's not true at all.  Plastic explosives like C4 absolutely do not detonate when a pressure wave hits them.  That's actually pretty much the main reason they're used all over the place.  They're super safe to handle, because very little will cause them to explode. You can hit them with a hammer, you can try to light them on fire, you can vibrate them like crazy.  Nothing will happen.  Pretty much the only thing that will set off C4 is an electrical spark.

The most common method for bomb disposal squads to make bombs safe is to blow them up with a "disruptor" charge.  The disruptor charge doesn't cause the main explosive to go off, instead, it scatters it all over the place, and separates the fuse from the main bomb.

That all said, I'm quite sure that even if the FTS didn't go off causing the explosion, it would have gone off instantaneously after the explosion, not because a pressure wave hit it, but because the AFTS would have detected something going very very wrong, and set it off.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tymo77 on 04/01/2021 04:18 pm

Pretty much the only thing that will set off C4 is an electrical spark.


I believe this is inaccurate, or is perhaps a misstatement of what you meant. From a manufacturers page on C4:

"Detonation can only be initiated by a combination of extreme heat and a shockwave, as results from the insertion and firing of a detonator." http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/ (http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/)

There is a recent relevant video from Tom Scott: https://www.youtube.com/watch?v=OOWcTV2nEkU (https://www.youtube.com/watch?v=OOWcTV2nEkU)

Whether tank detonation heat and pressure would be sufficient for sympathetic detonation is another question.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: fast on 04/01/2021 04:20 pm
snip...
I think it's possible they don't have the full telemetry data...

That's what I'm thinking. Extended loss of video feed from all the cameras points to a communications problem, rather than a hardware issue with a specific camera.

More importantly, SpaceX embeds their video feed as specific data packets inside of their telemetry data downlink (at least for Falcon 9), see -

https://www.r00t.cz/Sats/Falcon9 (https://www.r00t.cz/Sats/Falcon9)

Here is a recent video by Scott Manley about the wonderful work by some amateur radio operators figuring this out -

https://www.youtube.com/watch?v=74_N163HyhA (https://www.youtube.com/watch?v=74_N163HyhA)

In this arrangement, an extended, complete loss of video feed would likely be accompanied by an extensive loss of data telemetry.

This could also explain Elon's odd tweet, saying that "something significant happened", but they wouldn't know what until after they physically examined the debris -

https://twitter.com/elonmusk/status/1376891464333017090 (https://twitter.com/elonmusk/status/1376891464333017090)

----------

Also worth noting that early last week, an amateur radio enthusiast in the Boca Chica area was able to successfully receive the radio signal from the then-grounded SN11, analysis of which revealed it had a similar format to Falcon 9. However, a similar attempt on Friday revealed that everything is now encrypted!

Apparently, someone at SpaceX (same guy who didn't like LabPadre's cam?) got miffed that ham radio operators were able to receive video from their spacecraft, so they locked-down SN11 a few days ago.

Ironically - depending on how they did it - this sudden rush to encrypt the entire downlink from the spacecraft just a few days before flight could have caused or contributed to the loss of video and/or data telemetry during SN11's fateful foggy flight.


Someone need to buy IR camera...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/01/2021 04:42 pm


Someone need to buy IR camera...
Isn't the Labpadre FLIR cam (predator cam) infrared already? Couldn't see aaanything on there through the fog.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/01/2021 04:48 pm

Pretty much the only thing that will set off C4 is an electrical spark.


I believe this is inaccurate, or is perhaps a misstatement of what you meant. From a manufacturers page on C4:

"Detonation can only be initiated by a combination of extreme heat and a shockwave, as results from the insertion and firing of a detonator." http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/ (http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/)

(snip)

Whether tank detonation heat and pressure would be sufficient for sympathetic detonation is another question.

I recall someone with military background telling me that with C4 you can burn it (works good in a camp fire) or stomp on it (shape it like clay), just don't do both at the same time or you will have a very bad day.  Basically, don't throw a chunk in the fire and then stomp on it to put the fire out.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/01/2021 05:03 pm

Pretty much the only thing that will set off C4 is an electrical spark.


I believe this is inaccurate, or is perhaps a misstatement of what you meant. From a manufacturers page on C4:

"Detonation can only be initiated by a combination of extreme heat and a shockwave, as results from the insertion and firing of a detonator." http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/ (http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/)

(snip)

Whether tank detonation heat and pressure would be sufficient for sympathetic detonation is another question.

I recall someone with military background telling me that with C4 you can burn it (works good in a camp fire) or stomp on it (shape it like clay), just don't do both at the same time or you will have a very bad day.  Basically, don't throw a chunk in the fire and then stomp on it to put the fire out.

I thought it had something to do with the quickness of the igniter. Basically gunpowder doesn't work too good as an igniter for high explosives.
I once tried to detonate a 80lbs bag of 33-0-0 fertilizer(soaked with gasoline) with a pipe bomb filled with black powder. It didn't work. Basically I explosively fertilized the field I did it in.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 04/01/2021 05:46 pm
Okay, we're getting a bit crazy here with the FTS
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/01/2021 06:22 pm

Ironically - depending on how they did it - this sudden rush to encrypt the entire downlink from the spacecraft just a few days before flight could have caused or contributed to the loss of video and/or data telemetry during SN11's fateful foggy flight.

Several things can go wrong adding encryption at the last second especially with a lossy radio medium:

1.  Encryption is normally protected with strong hashes,  So any data errors are found and the frame thrown away by your encryption stack.  Whereas with plaintext data errors can leak through and esp. with video normally just cause frame drop later in the process, but your telemetry (plus/minus some bit errors) is just fine in plaintext but dropped by an encryption stack.

2.  I doubt they did this, but if they did stream level encryption instead of block level entire streams of data can be lost due to a lost chunk of data.

3.  If they did block level encryption and the blocks don't match the physical frame size you can get all sorts of double or more drops of physical frames when there's any sort of bit error or dropped physical frames.  Maybe the radio changes the block sizes on the fly and the encryption block sizes don't always match.

4.  I'm sure I'm missing another possibility


I would be very leery of adding encryption to time critical data streams on a lossy medium like radio on a vibrating rocket without extensive testing using a loss simulator that matches what the radio does under real conditions.

I've seen simulations of "cell phone enter a tunnel" scenarios destroy the functionality of alleged network/video optimization proxies.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dondar on 04/01/2021 06:41 pm
Let review landing burns.
SN8: coming into vertical position (6.41) after flip oscillation, one engine is flamed out, other methane is starved.

Fuel supply instability???
SN9: coming into vertical position (6.22) one engine ignites correctly, second is oxygen starved, vehicle failed to recover properly from the flip oscillation, the engine stays throttled and apparently dies moments before touchdown.
Fuel supply instability???
And or  yeaah. Probably I miss something but it looks like the flip maneuver starts a bit late.

SN10: coming into vertical position, three engines ignited correctly (heavily throttled), two get oxygen starved, third stays heavily throttled, at least one of the methane feed lines of starved engines stays open (you see clouds of fire on a right side of the vehicle). Vehicle slams ground being in almost vertical position. Accumulation of methane,  (oxygen leaks?)=> explosion.
Fuel supply instability?

SN11: clearly unzipped along vertical axis. (FTS?)

My take: gravity is a bitch. Auto-pressuring system is a bitch.  Vertical symmetry is not always norminal. (it is a bitch here). Probably they have to redesign downcomers and pr. reposition head-tanks to position them into appropriate physical system. ... And to reintroduce negative times in their auto pressurizing/burn algos ( instead of trying to catch right starting sequence.???)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/01/2021 07:16 pm

Pretty much the only thing that will set off C4 is an electrical spark.


I believe this is inaccurate, or is perhaps a misstatement of what you meant. From a manufacturers page on C4:

"Detonation can only be initiated by a combination of extreme heat and a shockwave, as results from the insertion and firing of a detonator." http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/ (http://www.eurenco.com/content/explosives/demolition-breaching/conventional/explosive-blocks/c4/)

(snip)

Whether tank detonation heat and pressure would be sufficient for sympathetic detonation is another question.

I recall someone with military background telling me that with C4 you can burn it (works good in a camp fire) or stomp on it (shape it like clay), just don't do both at the same time or you will have a very bad day.  Basically, don't throw a chunk in the fire and then stomp on it to put the fire out.
That's an old wives tale you hear in basic training. We conducted extensive semi-authorized experiments (meaning nobody said we couldn't do it) trying to detonate C4 in that manner without success. 
 And you don't set it off with a spark. You can set the detonator off with a spark. Might have been mercury fulminate back then, but I don't think they use that any more.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sevenperforce on 04/01/2021 08:20 pm
So from speculative diagrams of raptor we have.
The methane is heated enough for autogen by the pass through the engine bell.

The oxygen on the other hand needs to be passed through a heat exchanger in the turbine section of the preburner. So if the heat exchanger got a hole in it then possibly partially burned oxygen could get in the regen line for the oxygen.
From the diagrams I've seen, the methane isn't vaporized by the regenerative cooling pass -- it enters the fuel preburner while still a liquid (just much warmer). A tiny amount of that methane is tapped and sent through a heat exchanger in the fuel preburner exhaust stream to vaporize it and send it to autogen. Likewise, a small amount of LOX is sent through a heat exchanger in the oxygen preburner exhaust to vaporize it and send to autogen.

My speculation...

We saw Engine 2 on fire during ascent, with the primary burn area around the turbopump outlet to the cold fuel manifold. That is the single highest-pressure point in the entire engine. Setting aside the cause of that fire -- if the burn weakened the main fuel valve, then it could have failed during engine spin-up. Because helium is used to spin up the turbine, the upper impeller would have already had quite a bit of inertia and a sudden failure at the valve would have caused it to rip itself apart, sending a shockwave and shrapnel straight up the liquid methane feed line and into the methane downcomer.

Fragging the methane downcomer would have introduced GOX into the methane line, and with shrapnel flying, the immediate detonation wave would have traveled straight up the downcomer and popped the methane header around its circumferential seam like a balloon.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/01/2021 08:31 pm
So from speculative diagrams of raptor we have.
The methane is heated enough for autogen by the pass through the engine bell.

The oxygen on the other hand needs to be passed through a heat exchanger in the turbine section of the preburner. So if the heat exchanger got a hole in it then possibly partially burned oxygen could get in the regen line for the oxygen.
From the diagrams I've seen, the methane isn't vaporized by the regenerative cooling pass -- it enters the fuel preburner while still a liquid (just much warmer). A tiny amount of that methane is tapped and sent through a heat exchanger in the fuel preburner exhaust stream to vaporize it and send it to autogen. Likewise, a small amount of LOX is sent through a heat exchanger in the oxygen preburner exhaust to vaporize it and send to autogen.

My speculation...

We saw Engine 2 on fire during ascent, with the primary burn area around the turbopump outlet to the cold fuel manifold. That is the single highest-pressure point in the entire engine. Setting aside the cause of that fire -- if the burn weakened the main fuel valve, then it could have failed during engine spin-up. Because helium is used to spin up the turbine, the upper impeller would have already had quite a bit of inertia and a sudden failure at the valve would have caused it to rip itself apart, sending a shockwave and shrapnel straight up the liquid methane feed line and into the methane downcomer.

Fragging the methane downcomer would have introduced GOX into the methane line, and with shrapnel flying, the immediate detonation wave would have traveled straight up the downcomer and popped the methane header around its circumferential seam like a balloon.
Here are the 2 diagrams I have. I guess I looked at the less detailed one and saw no heat exchanger.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Gliderflyer on 04/01/2021 10:43 pm
I doubt the methane will be a liquid coming out of the channels. It's going to start going supercritical once it gets in the ballpark of 190K, and I very much doubt they can regen the whole thing and keep it that cold.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mn on 04/02/2021 01:33 am
....

This could also explain Elon's odd tweet, saying that "something significant happened", but they wouldn't know what until after they physically examined the debris -

https://twitter.com/elonmusk/status/1376891464333017090 (https://twitter.com/elonmusk/status/1376891464333017090)
...


Elon said "once we can examine the bits later today."

I suspect that Elon meant bits of data not bits of steel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/02/2021 04:30 am
....

This could also explain Elon's odd tweet, saying that "something significant happened", but they wouldn't know what until after they physically examined the debris -

https://twitter.com/elonmusk/status/1376891464333017090 (https://twitter.com/elonmusk/status/1376891464333017090)
...


Elon said "once we can examine the bits later today."

I suspect that Elon meant bits of data not bits of steel.

He may mean both.  Even in the twisted wreckage, there's forensic engineering to be done.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wolfi44 on 04/02/2021 10:41 am
Do they fit a flight data recorder, like on airplanes ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 04/02/2021 10:54 am
Great SN11 debris map, not sure about the theory though.

https://twitter.com/Bojay_stellar/status/1377373804784013322

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/02/2021 10:59 am
Do they fit a flight data recorder, like on airplanes ?
All the flight data were being sent back to the command center while the flight is ongoing in real time
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mn on 04/02/2021 02:18 pm
....

This could also explain Elon's odd tweet, saying that "something significant happened", but they wouldn't know what until after they physically examined the debris -

https://twitter.com/elonmusk/status/1376891464333017090 (https://twitter.com/elonmusk/status/1376891464333017090)
...


Elon said "once we can examine the bits later today."

I suspect that Elon meant bits of data not bits of steel.

He may mean both.  Even in the twisted wreckage, there's forensic engineering to be done.

I wasn't doubting that they can learn from the debris, I am only questioning the assertion that this tweet implies that they lost telemetry (before the RUD)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 03:32 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/02/2021 03:36 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
Falcon Heavy has never been static fired in full duration with all three cores together before its maiden flight
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 03:36 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
And dynamic test stands as well... But it's his "Hobby Rocket Ranch" so he can do as he pleases...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rcoppola on 04/02/2021 03:42 pm
Let's see what SN15 with the next block of Raptors acts like.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 03:43 pm
Let's see what SN15 with the next block of Raptors acts like.
Mean little critters that eat each other? ;D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 03:46 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
Falcon Heavy has never been static fired in full duration with all three cores together before its maiden flight

No but they did static fire each core separately for full duration. 
Has SpaceX even attempted to fire multiple Raptors together at McGregor using some type of test article? 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 03:49 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
Falcon Heavy has never been static fired in full duration with all three cores together before its maiden flight

No but they did static fire each core separately for full duration. 
Has SpaceX even attempted to fire multiple Raptors together at McGregor using some type of test article?
Not as far as I know anyone? His "All Up" test of SS is his approach...

Edit to add:
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/02/2021 03:54 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
Falcon Heavy has never been static fired in full duration with all three cores together before its maiden flight

No but they did static fire each core separately for full duration. 
Has SpaceX even attempted to fire multiple Raptors together at McGregor using some type of test article? 

I've been wondering if SpaceX couldn't have benefited from a SS 3 engine test rig that simulates the flip maneuver.    It would be a heck of test device, but may help figure out how to avoid splashing these SS on the landing slab.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 04:02 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
Falcon Heavy has never been static fired in full duration with all three cores together before its maiden flight

No but they did static fire each core separately for full duration. 
Has SpaceX even attempted to fire multiple Raptors together at McGregor using some type of test article? 

I've been wondering if SpaceX couldn't have benefited from a SS 3 engine test rig that simulates the flip maneuver.    It would be a heck of test device, but may help figure out how to avoid splashing these SS on the landing slab.
It's been mentioned before...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/02/2021 04:08 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.

Isn't boca chica the test stand? They can't get full sized tanks and engines in Macgregor since they are made in boca chica.
The problems really seem to be related to the whole vehicle tanks and engines in the real dynamic environment.
Plus at the same time keeps boca chica factory churning out new ones which perfects the factory.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/02/2021 04:12 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.

Isn't boca chica the test stand? They can't get full sized tanks and engines in Macgregor since they are made in boca chica.
The problems really seem to be related to the whole vehicle tanks and engines in the real dynamic environment.
Plus at the same time keeps boca chica factory churning out new ones and perfects the factory.
Yeah. I'd be interested in seeing people's analysis of the relative cost of a Starship prototype versus these hypothetical test stands.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/02/2021 04:15 pm
 If they can build, launch and clean up the landing with these prototypes for less time and money than a simulator that would be missing a hundred unforeseen, real world factors, why bother?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: electricdawn on 04/02/2021 04:19 pm
I dare say that even if it costs more than a simulator, the real life experience is worth it. The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

Edit to add: So, in a way, SN11's failure is worth more than any simulator flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 04:21 pm
I presume he could ask NASA to use their Dynamic Test Stand if he feels the need...

Edit:typo
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/02/2021 04:22 pm
Exactly! The prototypes ARE the test stand.

Sent from my Redmi Note 7 using Tapatalk

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Burningdan87 on 04/02/2021 04:26 pm
I dare say that even if it costs more than a simulator, the real life experience is worth it. The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

Edit to add: So, in a way, SN11's failure is worth more than any simulator flight.


This is my exact thinking on this. SpaceX's method for a while has been to very purposely break things until they stop breaking. They don't do the "test to prepare for the tests test" route almost ever. It is far more in line with their thinking, especially re:the Starship program, to just keep pumping out Starships and Raptors to figure out mass production, flight, and vehicle hardware all worked out in parallel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 04:29 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.

Isn't boca chica the test stand? They can't get full sized tanks and engines in Macgregor since they are made in boca chica.
The problems really seem to be related to the whole vehicle tanks and engines in the real dynamic environment.
Plus at the same time keeps boca chica factory churning out new ones and perfects the factory.

SpaceX doesn't have anything at Boca Chica similar to the NASA B-1/B-2 test stands at Stennis.  Something that can support full duration static fires of Starship stages. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oberonian on 04/02/2021 04:34 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.

Yes RD-170 was tested for 2200 seconds and 20 burns etc.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 04:36 pm
Elon is trying to emulate the Soviet Union “turning out missiles like sausages" in the 50's.... ;D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 04:37 pm
I dare say that even if it costs more than a simulator, the real life experience is worth it. The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

Edit to add: So, in a way, SN11's failure is worth more than any simulator flight.


This is my exact thinking on this. SpaceX's method for a while has been to very purposely break things until they stop breaking. They don't do the "test to prepare for the tests test" route almost ever. It is far more in line with their thinking, especially re:the Starship program, to just keep pumping out Starships and Raptors to figure out mass production, flight, and vehicle hardware all worked out in parallel.

SpaceX went the "test to prepare for the tests test" with the F9 development.  SpaceX did complete full duration static fires of the 1st and 2nd stages at McGregor before any hardware went to Florida.  Brand new Falcon-9's go from Hawthorne to McGregor for testing including full duration static fires before they are shipped to a launch site. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/02/2021 04:41 pm
Exactly! The prototypes ARE the test stand.

Sent from my Redmi Note 7 using Tapatalk
Right.
These first prototypes had the job of testing the ascent/ descent part, as I understood the succesful landing was a "bonus", wanted, but not tha main objective. Remember they had sn12/13/14, scapped bacause sn8 did more than they thought.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 04/02/2021 04:41 pm
Why build a custom stand that tests 1 thing when you can have a stand that tests n + 1 things, and lets you test them as you fly?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/02/2021 04:41 pm
Is the development of Starship being hampered

Cutting the quote here and answering: No.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CrazyHorse80 on 04/02/2021 04:50 pm
Why build a custom stand that tests 1 thing when you can have a stand that tests n + 1 things, and lets you test them as you fly?

This and also I think a RUD at 0 feet altitude is much worse than a midair RUD...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 04/02/2021 04:51 pm
The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

I think this statement sums up the SpaceX hardware rich development program nicely. Something similar was a central point I still recall from my Freshman Intro To Engineering class back at the dawn of time,
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/02/2021 04:53 pm
I dare say that even if it costs more than a simulator, the real life experience is worth it. The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

Edit to add: So, in a way, SN11's failure is worth more than any simulator flight.


This is my exact thinking on this. SpaceX's method for a while has been to very purposely break things until they stop breaking. They don't do the "test to prepare for the tests test" route almost ever. It is far more in line with their thinking, especially re:the Starship program, to just keep pumping out Starships and Raptors to figure out mass production, flight, and vehicle hardware all worked out in parallel.
SpaceX are very good at ‘preparing to fail’ rather than ‘failing to prepare’ in their very fast test programme. The idea is to test a bunch of static assets with small opportunity to fine tune to figure out all the bugs as best possible. What other organisations get wrong is that they change things too often and don’t test enough.

The success to F9 is down to finding out most of their issues early in the failures. Doing this whilst building in redundancy has ensured there’s the wiggle room to progress with real customers.

I’m not too worried about the Raptor instability. We’ve only had 4 launches to a decent apogee and seen pretty good success on ascent (their bread and butter really), even with underperforming Raptors. Like the Falcon landing, they’re trying to hit their ‘X mark’ where the hardware is capable and software can achieve it within an acceptable tolerance. I think we’ll get there at the end of the next test batch (SN15-19).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Legios on 04/02/2021 04:55 pm
I can't believe people are this concerned that SN-11, a vehicle that was already obsolete and had obsolete engines, blew up.

Even if there was only a 1% chance of it working, why would SpaceX not take the chance if flying it and finding out something new?  It was already built and very few parts could be re-purposed. The cost was already spent.

It's been about 16 months since Mk1 was completed. The progress has been staggering.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/02/2021 04:59 pm
I can't believe people are this concerned that SN-11, a vehicle that was already obsolete and had obsolete engines, blew up.
My only concern is that we didn't get to see it blow up!  That would have been an amazing sight.  If only they had waited for the fog to lift before flying.

Based on assembly work, I expect we'll see SN15 out on the pad in another week or two.  Handwaving will move on to that vehicle soon enough.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 05:00 pm
I dare say that even if it costs more than a simulator, the real life experience is worth it. The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

Edit to add: So, in a way, SN11's failure is worth more than any simulator flight.


This is my exact thinking on this. SpaceX's method for a while has been to very purposely break things until they stop breaking. They don't do the "test to prepare for the tests test" route almost ever. It is far more in line with their thinking, especially re:the Starship program, to just keep pumping out Starships and Raptors to figure out mass production, flight, and vehicle hardware all worked out in parallel.
SpaceX are very good at ‘preparing to fail’ rather than ‘failing to prepare’ in their very fast test programme. The idea is to test a bunch of static assets with small opportunity to fine tune to figure out all the bugs as best possible. What other organisations get wrong is that they change things too often and don’t test enough.

The success to F9 is down to finding out most of their issues early in the failures. Doing this whilst building in redundancy has ensured there’s the wiggle room to progress with real customers.

I’m not too worried about the Raptor instability. We’ve only had 4 launches to a decent apogee and seen pretty good success on ascent (their bread and butter really), even with underperforming Raptors. Like the Falcon landing, they’re trying to hit their ‘X mark’ where the hardware is capable and software can achieve it within an acceptable tolerance. I think we’ll get there at the end of the next test batch (SN15-19).
Welcome to the forum! :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sevenperforce on 04/02/2021 05:01 pm
I doubt the methane will be a liquid coming out of the channels. It's going to start going supercritical once it gets in the ballpark of 190K, and I very much doubt they can regen the whole thing and keep it that cold.
Ah, good point, thanks. I forgot about supercriticality.

Actually, let me think -- what IS the heat rejection capability here? This is solvable, right? At least roughly? Exhaust temperature is around 3600 K. If we model Raptor's combustion chamber as an open cylinder approximately 0.39 m high and approximately 0.30 m in diameter, and we model the engine bell as a right truncated cone with a lower diameter of 1.3 m, an upper diameter of 0.3 m, and a height of 1.57 m, that gives us a total cooled surface area of 4.5 square meters.

It's hard to get good numbers for the convective heat transfer coefficient of inconel (which should have similar properties to the Raptor chamber and engine bell), but I'm estimating it's on the order of 1500 W/m2*K. The engine bell needs to be kept below around 1250 K (that's the max service temperature of inconel). So the heat flux that needs to be dumped into the liquid methane is going to be....

(1.5 kW/(m2*K))*(3600 K - 1250 K)*(4.5 m2) = 15.86 MW

At full thrust, Raptor is pushing 140 kg of CH4 through its engine bell every second, which we assume is subcooled to around 95 K (the melting/freezing point is 91 K). The specific heat of liquid methane at 99 K is 34.1 J/mol*K, and since the molar mass of methane is 16.04 g/mol, that gives us a specific heat capacity of 2.13 J/g*K.

But we're not pumping 1 gram per second; we're pumping 140 kilograms per second. So the heat rejection capacity of our liquid methane flow is going to be 298 kW per degree Kelvin. Absorbing 15.9 MW would heat our flow by 53.4 K, to 148.4 K. Methane's critical point is 190.56 K at 46 bar, so it would still be very much a liquid when it hits the fuel preburner. Of course, if convective heat transfer coefficient of the engine bell is much higher (e.g., on the order of 3 kW/(m2*K)), then the temperature will be over the critical point and it will enter the preburner in the supercritical phase.

Worth noting, I suppose, that since the tanks are only pressed to about 3 bar, you can exhaust liquid methane into them at anything over around ~133 K and it will go gaseous. But of course it makes sense to run it through a heat exchanger because hotter gas does a better job for autogenous pressurization with less mass consumption.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Proesterchen on 04/02/2021 05:03 pm
I can't believe people are this concerned that SN-11
It's only fair, as it would have been heralded as a huge success if SN11 had landed and stayed in one piece.

Anyway. Do we expect SpaceX to do high altitude flip & burn testing in preparation for Mars landings?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/02/2021 05:08 pm
If they can build, launch and clean up the landing with these prototypes for less time and money than a simulator that would be missing a hundred unforeseen, real world factors would take, why bother?

Except you could test it multiple times a day, tinker with it and solve the problem, if there is one, in days not months.

Blowing up office building sized prototypes gets expensive, even for SpaceX.

There is clearly something going on with the Raptors relighting and getting enough fuel.  Part could be the engine, getting enough fuel to the pumps is a rocket plumbing issue. 

I can appreciate the testing while flying, but some problems can be solved in cheaper faster ways. 

Maybe the Raptor is less mature than it seems.

We have SN15 to SN19 to see if they can sort that before the orbit capable vehicles start showing up.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/02/2021 05:13 pm
Anyway. Do we expect SpaceX to do high altitude flip & burn testing in preparation for Mars landings?

I expect that SN15-19 will be similar test flight profiles as SN8-11.  However, the "goal" of this prototype version will be to have successful flip and burn with controlled descent down to the pad.

I don't think we'll necessarily see a "high altitude" launch until we get to SN20+ (orbital class).  My gut is telling me that SN20 will be the first vehicle designed specifically to deal with higher hull stresses related to re-entry and supersonic flight through earth atmosphere.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/02/2021 05:19 pm
Anyway. Do we expect SpaceX to do high altitude flip & burn testing in preparation for Mars landings?

I expect that SN15-19 will be similar test flight profiles as SN8-11.  However, the "goal" of this prototype version will be to have successful flip and burn with controlled descent down to the pad.

I don't think we'll necessarily see a "high altitude" launch until we get to SN20+ (orbital class).  My gut is telling me that SN20 will be the first vehicle designed specifically to deal with higher hull stresses related to re-entry and supersonic flight through earth atmosphere.
I'm not sure about that.  Although 15-19 can't test reentry, they can test higher speed and higher altitude than what 8-11 were capable of.  How bad would the ground effect be for a sonic boom generated 10 km up?  Another option might be to fly further off shore, turn, and start flying back before engine shutoff to test an approach profile other than from straight up.  Either way, there is a lot of envelope expanding that can be done beyond the previous series of flights.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Gliderflyer on 04/02/2021 05:20 pm
I doubt the methane will be a liquid coming out of the channels. It's going to start going supercritical once it gets in the ballpark of 190K, and I very much doubt they can regen the whole thing and keep it that cold.
Ah, good point, thanks. I forgot about supercriticality.

Actually, let me think -- what IS the heat rejection capability here? This is solvable, right? At least roughly? Exhaust temperature is around 3600 K. If we model Raptor's combustion chamber as an open cylinder approximately 0.39 m high and approximately 0.30 m in diameter, and we model the engine bell as a right truncated cone with a lower diameter of 1.3 m, an upper diameter of 0.3 m, and a height of 1.57 m, that gives us a total cooled surface area of 4.5 square meters.

It's hard to get good numbers for the convective heat transfer coefficient of inconel (which should have similar properties to the Raptor chamber and engine bell), but I'm estimating it's on the order of 1500 W/m2*K. The engine bell needs to be kept below around 1250 K (that's the max service temperature of inconel). So the heat flux that needs to be dumped into the liquid methane is going to be....

(1.5 kW/(m2*K))*(3600 K - 1250 K)*(4.5 m2) = 15.86 MW

At full thrust, Raptor is pushing 140 kg of CH4 through its engine bell every second, which we assume is subcooled to around 95 K (the melting/freezing point is 91 K). The specific heat of liquid methane at 99 K is 34.1 J/mol*K, and since the molar mass of methane is 16.04 g/mol, that gives us a specific heat capacity of 2.13 J/g*K.

But we're not pumping 1 gram per second; we're pumping 140 kilograms per second. So the heat rejection capacity of our liquid methane flow is going to be 298 kW per degree Kelvin. Absorbing 15.9 MW would heat our flow by 53.4 K, to 148.4 K. Methane's critical point is 190.56 K at 46 bar, so it would still be very much a liquid when it hits the fuel preburner. Of course, if convective heat transfer coefficient of the engine bell is much higher (e.g., on the order of 3 kW/(m2*K)), then the temperature will be over the critical point and it will enter the preburner in the supercritical phase.

Worth noting, I suppose, that since the tanks are only pressed to about 3 bar, you can exhaust liquid methane into them at anything over around ~133 K and it will go gaseous. But of course it makes sense to run it through a heat exchanger because hotter gas does a better job for autogenous pressurization with less mass consumption.
The chamber should be copper (thermal conductivity of ~300 W/(m*K) vs 12 for inconel), with maybe the last part of the nozzle something else (it could be copper too, I'm not sure). If someone has the full version of RPA, they could ballpark the cooling channels (I might try to get my Bartz spreadsheet working and take a look at it too). I don't have a good feel for the heat transfer coefficients at these chamber pressures, but I feel like they should be higher.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 04/02/2021 05:22 pm
TBH if SpaceX thought it was cheaper to build a carnival-style 50m long lever arm to test the Raptors during the flip vs. expending prototypes, they would have probably built one already.

Besides, any time and money spent on the test stand would be time and money not spent on other aspects of the system. Then you have the fact that the test stand is still not the actual ship, so there's no guarantee the results will apply 1:1. The more you make the test stand resemble the actual ship, the more reason there is to just use the actual ship in the first place.

We also have to remember that landing the prototypes is not the immediate goal of the program - getting to orbit to deploy Starlink and make money is. They can test landings a la Falcon 9 landings while generating revenue. When they're ready for Mars, they'll be ready for Mars.

Personally I think the great genius of SpaceX isn't just in landing and reusing rockets, but making them cheaper than the competition in the first place, even without reuse. Even if they never landed a single Starship, it would still be a Saturn V-class launcher that costs as much or less than a Falcon 9.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/02/2021 05:31 pm
I'm not sure about that.  Although 15-19 can't test reentry, they can test higher speed and higher altitude than what 8-11 were capable of.  How bad would the ground effect be for a sonic boom generated 10 km up?  Another option might be to fly further off shore, turn, and start flying back before engine shutoff to test an approach profile other than from straight up.  Either way, there is a lot of envelope expanding that can be done beyond the previous series of flights.

They don't need to test higher descent speed (it already reaches it's terminal velocity on decent in the bellyflop profile.)  Just MHO, but if they start pushing higher ascent speed through low atmosphere they are running a risk of RUD on ascent and would miss the opportunity to test the main objective: the flip and burn/landing.

I'll meet you half-way though.  :)  If SN 15 and 16 are successful enough on the flip/burn/land...and they already have 17/18 in the wings mostly constructed...then sure.  Push the envelope on those vehicles since they would already have the significant data / validation on the flip and burn from 15/16 success.

I still think that at this point the primary test objective is to be able to successfully flip/burn/control descent...and any significant envelope pushing in other areas that might jeopardize the chance at testing for the primary objective will be shied away from.  Again...just my opinion.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 04/02/2021 05:47 pm
Why build a custom stand that tests 1 thing when you can have a stand that tests n + 1 things, and lets you test them as you fly?

You could reverse the question, and ask "Why doesn't NASA do actual flight tests of new hardware in the dynamic environment rather than using less than accurate test stands?". One answer is because their hardware is an order of magnitude or more more expensive, and they don't focus on manufacturability of greater volumes of hardware. So the test stand is the crutch so they can test and then fly the tested article, since they don't have hardly any copies. (See SLS).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 05:51 pm
Is the development of Starship being hampered

Cutting the quote here and answering: No.

Why do you say No?  SpaceX tested the F9 hardware using full duration static fires and continues to test every F9 that comes off the production line with full duration static fires. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 04/02/2021 06:19 pm
If they can build, launch and clean up the landing with these prototypes for less time and money than a simulator that would be missing a hundred unforeseen, real world factors, why bother?

[Wherein I play someone too dumb to notice a rhetorical question....]
You bother if safety concerns are high or if the mitigation for those concerns insert enough latency into the project that you cannot make meaningful progress.  You might also bother if the combinatorics of real world factors impedes understanding issues.  I do not think we are suffering from the latter, I'm not sure about the former.  There's some crankiness there at least.

But otherwise, considering that these prototypes are being built for the purposes of improving the manufacturing process anyway, it doesn't make sense to not try to leverage them as assets for other purposes (as so many have said here, so many times, and in so many ways...).

Note also, for those wanting to see a multi-Raptor test stand built at McGregor, BN1 could act as such a mule, if that's where they are in the process.  Make of its fate what you will.  I bet the engine folks would prefer a dedicated test stand when it comes down to it, but I also am willing to guess that they have their hands full already.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sevenperforce on 04/02/2021 06:48 pm
The chamber should be copper (thermal conductivity of ~300 W/(m*K) vs 12 for inconel), with maybe the last part of the nozzle something else (it could be copper too, I'm not sure). If someone has the full version of RPA, they could ballpark the cooling channels (I might try to get my Bartz spreadsheet working and take a look at it too). I don't have a good feel for the heat transfer coefficients at these chamber pressures, but I feel like they should be higher.
Elon said Raptor's chamber and bell use milled copper channels with an inconel jacket all the way down:

https://twitter.com/elonmusk/status/1177387141116002304

It's an approach that makes a lot of sense. You want the highest convective thermal conductivity closest to your coolant, but you want something with a higher melting point and lower convective thermal conductivity closest to your exhaust.

This table (https://www.engineeringtoolbox.com/overall-heat-transfer-coefficients-d_284.html) gives heat transmission coefficients between two fluids separated by a variety of materials. Using steam-to-water as a very rough comparison to the exhaust-to-LCH4 happening across Raptor, we get the following material heat coefficients (all in units of W/m2K):

Stainless steel: 680
Cast iron: 910
Mild steel: 1050
Copper: 1160

Note that thermal conductivity of these four materials (in W/m*K) are 14, 52, 65, and 385, respectively. That doesn't fit any pretty curve, of course, but it is at least monotonic, so if the thermal conductivity of inconel is close to that of stainless, I'm going to assume that the heat transfer coefficient is also similar. Of course, this is probably for a steady-state heat transfer rather than a convective flow heat transfer, so I'm not sure what difference there will be at high pressures. The Dittus-Bölter equation doesn't have a term for pressure and probably only applies to liquids, not gaseous exhaust.

Copper is such a good heat conductor that the limiting factor will obviously be the inconel here. But if the heat transfer coefficient of inconel is as low as that of stainless, we'd potentially only be looking at a heat transfer rate of 7.2 MW which would only heat our liquid methane to about 120 K which might not even be warm enough to boil when it hits the 3 bar tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/02/2021 07:02 pm
These conversations all seem to miss the inherent observational bias: we only see the big tests, the ones you can observe from 3 miles away or 5,500' up. Not only are we missing every test performed indoors, the brave new world of computational fluid dynamics surely means the both the "largest" and most frequent tests are all virtual. Each real life test provides a mountain of data to further refine the models that can then power another hundred virtual tests which are completely invisible to us.  In this way they've undoubtedly been testing re-entry, for example, for years now.  I'm sure they know exactly how much surface unevenness they can tolerate and still meet their insulation and adhesion goals.  They just need to practice *actually making the thing* until they can hit those marks, and if they can't manufacture to that tolerance they've got the models to know exactly how much thicker/heavier/stronger the tiles need to be in response.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: docmordrid on 04/02/2021 07:08 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.

Isn't boca chica the test stand? They can't get full sized tanks and engines in Macgregor since they are made in boca chica.
The problems really seem to be related to the whole vehicle tanks and engines in the real dynamic environment.
Plus at the same time keeps boca chica factory churning out new ones and perfects the factory.

SpaceX doesn't have anything at Boca Chica similar to the NASA B-1/B-2 test stands at Stennis.  Something that can support full duration static fires of Starship stages.

Beyond that, SpaceX signed an agreement with McGregor's city father's in 2019 which further limited sound levels, test times, etc.

Waco Tribune... (https://wacotrib.com/business/mcgregor-sets-new-limits-on-spacex-rocket-noise/article_174a13fd-652b-5139-a4fa-2d328cc89f0e.html)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/02/2021 07:15 pm
Is the development of Starship being hampered

Cutting the quote here and answering: No.

Why do you say No?  SpaceX tested the F9 hardware using full duration static fires and continues to test every F9 that comes off the production line with full duration static fires.

Because the development of starship is not hampered by anything so far. Not by explosions, not by hurricanes, not by pandemics, not by the lack of a full duration test stand. It just isn't. They are doing well and are continuously improving, figuring out what not to do and so on. I believe they are still well within their targeted timeframe and expectations of "things that will probably go wrong".

And as was said before, when gey get to a point when they need full duration firings, they will do them in mid air on a full vehicle. The reason why others don't do it is because their rockets are not coming back intact from flights.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 04/02/2021 07:32 pm
Is the development of Starship being hampered

Cutting the quote here and answering: No.

Why do you say No?  SpaceX tested the F9 hardware using full duration static fires and continues to test every F9 that comes off the production line with full duration static fires.

Because the development of starship is not hampered by anything so far. Not by explosions, not by hurricanes, not by pandemics, not by the lack of a full duration test stand. It just isn't. They are doing well and are continuously improving, figuring out what not to do and so on. I believe they are still well within their targeted timeframe and expectations of "things that will probably go wrong".

And as was said before, when gey get to a point when they need full duration firings, they will do them in mid air on a full vehicle. The reason why others don't do it is because their rockets are not coming back intact from flights.
Shuttle did...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 04/02/2021 07:46 pm
Premiere in 20 mins

https://youtu.be/l4eawtvznbc

Heh, you can see and hear a big piece of debris landing on Starhopper at 4:18... although I have the feeling a whole Starship could fall on it before we'd see a scratch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/02/2021 08:00 pm
These conversations all seem to miss the inherent observational bias: we only see the big tests, the ones you can observe from 3 miles away or 5,500' up. Not only are we missing every test performed indoors, the brave new world of computational fluid dynamics surely means the both the "largest" and most frequent tests are all virtual. Each real life test provides a mountain of data to further refine the models that can then power another hundred virtual tests which are completely invisible to us.  In this way they've undoubtedly been testing re-entry, for example, for years now.  I'm sure they know exactly how much surface unevenness they can tolerate and still meet their insulation and adhesion goals.  They just need to practice *actually making the thing* until they can hit those marks, and if they can't manufacture to that tolerance they've got the models to know exactly how much thicker/heavier/stronger the tiles need to be in response.
The big SNx tests are the result of what we don’t see. To be honest, the live streams + indie producers recording this stuff in real-time gives an extra sense of failure. But I think some already claiming a big struggle for the Starship team are forgetting what we saw with SN10. Yes, it landed hard but it covered everything (maybe apart from a landing on the legs for recovery + assessment). These phases are design with certain outcomes to allow to move the project on quickly. No aim for perfection and even Elon’s predictions (on Twitter) of success are nowhere near 100% at this stage.

SN11 will be a negative sticking point for the media and some of the public, but a golden nugget for SpaceX if they figure out the issue. Something that gets me excited for SN15. Knowing the improvements to Raptor and the hardware/software in advance is a figure of progress in itself.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 08:08 pm
Is the development of Starship being hampered

Cutting the quote here and answering: No.

Why do you say No?  SpaceX tested the F9 hardware using full duration static fires and continues to test every F9 that comes off the production line with full duration static fires.

Because the development of starship is not hampered by anything so far. Not by explosions, not by hurricanes, not by pandemics, not by the lack of a full duration test stand. It just isn't. They are doing well and are continuously improving, figuring out what not to do and so on. I believe they are still well within their targeted timeframe and expectations of "things that will probably go wrong".

And as was said before, when gey get to a point when they need full duration firings, they will do them in mid air on a full vehicle. The reason why others don't do it is because their rockets are not coming back intact from flights.

I hope you are right.  This is just the testing of the 2nd stage.  Hopefully they can apply the lessons learned to Super Heavy and have less RUD's.  A Super Heavy RUD would create a bigger debris field. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: electricdawn on 04/02/2021 08:25 pm
Airliner reliability combined with very cheap launch costs and full reusability isn't going to happen over night. What is happening down there in Boca Chica is revolutionary (and no, I'm not saying this as a slobbering amazing people, but rather as a fan of space exploration in general).

We need to give SpaceX some time. They're already moving at a neck breaking pace. I can appreciate that even better now while still reading Eric Berger's book "Liftoff". Elon Musk is certainly not the man I want to work for, but, man, does he know how to not only drive his people but also give them the freedom they need to accomplish something.

And, boy, do they accomplish "something"!

And, yes, he can be an a** sometime.  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/02/2021 08:45 pm
I doubt the methane will be a liquid coming out of the channels. It's going to start going supercritical once it gets in the ballpark of 190K, and I very much doubt they can regen the whole thing and keep it that cold.
Ah, good point, thanks. I forgot about supercriticality.

Actually, let me think -- what IS the heat rejection capability here? This is solvable, right? At least roughly? Exhaust temperature is around 3600 K. If we model Raptor's combustion chamber as an open cylinder approximately 0.39 m high and approximately 0.30 m in diameter, and we model the engine bell as a right truncated cone with a lower diameter of 1.3 m, an upper diameter of 0.3 m, and a height of 1.57 m, that gives us a total cooled surface area of 4.5 square meters.

It's hard to get good numbers for the convective heat transfer coefficient of inconel (which should have similar properties to the Raptor chamber and engine bell), but I'm estimating it's on the order of 1500 W/m2*K. The engine bell needs to be kept below around 1250 K (that's the max service temperature of inconel). So the heat flux that needs to be dumped into the liquid methane is going to be....

(1.5 kW/(m2*K))*(3600 K - 1250 K)*(4.5 m2) = 15.86 MW

At full thrust, Raptor is pushing 140 kg of CH4 through its engine bell every second, which we assume is subcooled to around 95 K (the melting/freezing point is 91 K). The specific heat of liquid methane at 99 K is 34.1 J/mol*K, and since the molar mass of methane is 16.04 g/mol, that gives us a specific heat capacity of 2.13 J/g*K.

But we're not pumping 1 gram per second; we're pumping 140 kilograms per second. So the heat rejection capacity of our liquid methane flow is going to be 298 kW per degree Kelvin. Absorbing 15.9 MW would heat our flow by 53.4 K, to 148.4 K. Methane's critical point is 190.56 K at 46 bar, so it would still be very much a liquid when it hits the fuel preburner. Of course, if convective heat transfer coefficient of the engine bell is much higher (e.g., on the order of 3 kW/(m2*K)), then the temperature will be over the critical point and it will enter the preburner in the supercritical phase.

Worth noting, I suppose, that since the tanks are only pressed to about 3 bar, you can exhaust liquid methane into them at anything over around ~133 K and it will go gaseous. But of course it makes sense to run it through a heat exchanger because hotter gas does a better job for autogenous pressurization with less mass consumption.

Well...  AFAIK, inconel is not used for the linings of rocket combustion chambers, but rather copper based alloys are preferred.  Looking at a random NASA paper about GRCop-84 and its proposed use as a combustion chamber lining material, we see that the thermal conductivity is 10-20 times greater than inconel.

I think you nicely illustrated why highly conductive alloys are desirable.  Even ignoring our desire to vaporize fuel before it reaches the combustion chamber, cooling becomes much less effective when the inside of the chamber does not conduct heat very well.

Supporting evidence of SpaceX using a copper alloy for their combustion chamber linings, rather than something like inconel, which does not contain a significant amount of copper, is the green flame we've seen when Raptors have problems and undergo engine rich combustion.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/02/2021 08:47 pm
I dare say that even if it costs more than a simulator, the real life experience is worth it. The real thing is, after all,... well... the real deal. No simulation can cover everything that can happen.

Edit to add: So, in a way, SN11's failure is worth more than any simulator flight.


This is my exact thinking on this. SpaceX's method for a while has been to very purposely break things until they stop breaking. They don't do the "test to prepare for the tests test" route almost ever. It is far more in line with their thinking, especially re:the Starship program, to just keep pumping out Starships and Raptors to figure out mass production, flight, and vehicle hardware all worked out in parallel.

SpaceX went the "test to prepare for the tests test" with the F9 development.  SpaceX did complete full duration static fires of the 1st and 2nd stages at McGregor before any hardware went to Florida.  Brand new Falcon-9's go from Hawthorne to McGregor for testing including full duration static fires before they are shipped to a launch site.
Maybe that's when they learned that they don't want to do it that way with Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/02/2021 08:54 pm
Is the development of Starship being hampered

Cutting the quote here and answering: No.

Why do you say No?  SpaceX tested the F9 hardware using full duration static fires and continues to test every F9 that comes off the production line with full duration static fires.

There is a difference in testing for development and testing for customer assurance.
f9 test to make sure the customer gets a success
ss test to further the R+D.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Gliderflyer on 04/02/2021 10:08 pm
The chamber should be copper (thermal conductivity of ~300 W/(m*K) vs 12 for inconel), with maybe the last part of the nozzle something else (it could be copper too, I'm not sure). If someone has the full version of RPA, they could ballpark the cooling channels (I might try to get my Bartz spreadsheet working and take a look at it too). I don't have a good feel for the heat transfer coefficients at these chamber pressures, but I feel like they should be higher.
Elon said Raptor's chamber and bell use milled copper channels with an inconel jacket all the way down:

https://twitter.com/elonmusk/status/1177387141116002304

It's an approach that makes a lot of sense. You want the highest convective thermal conductivity closest to your coolant, but you want something with a higher melting point and lower convective thermal conductivity closest to your exhaust.

This table (https://www.engineeringtoolbox.com/overall-heat-transfer-coefficients-d_284.html) gives heat transmission coefficients between two fluids separated by a variety of materials. Using steam-to-water as a very rough comparison to the exhaust-to-LCH4 happening across Raptor, we get the following material heat coefficients (all in units of W/m2K):

Stainless steel: 680
Cast iron: 910
Mild steel: 1050
Copper: 1160

Note that thermal conductivity of these four materials (in W/m*K) are 14, 52, 65, and 385, respectively. That doesn't fit any pretty curve, of course, but it is at least monotonic, so if the thermal conductivity of inconel is close to that of stainless, I'm going to assume that the heat transfer coefficient is also similar. Of course, this is probably for a steady-state heat transfer rather than a convective flow heat transfer, so I'm not sure what difference there will be at high pressures. The Dittus-Bölter equation doesn't have a term for pressure and probably only applies to liquids, not gaseous exhaust.

Copper is such a good heat conductor that the limiting factor will obviously be the inconel here. But if the heat transfer coefficient of inconel is as low as that of stainless, we'd potentially only be looking at a heat transfer rate of 7.2 MW which would only heat our liquid methane to about 120 K which might not even be warm enough to boil when it hits the 3 bar tank.

You actually want the flame side to have high conductivity (like copper), otherwise it is very hard to cool.

On the heat transfer coefficient, I made a quick-and-dirty Bartz spreadsheet based on H&H. Bartz usually predicts high, and raptor has some film cooling, but I was getting heat transfer coefficients in the 20s of kW/m^2-K. RPA was predicting lower than that, ~15 for the barrel section of the chamber. The trial version does regen, and some very non-optimized channels were getting about 300K out without too crazy a pressure drop.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/02/2021 10:12 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
As long as it clears the pad, isn't it better that it explode in the air than on a test stand?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/02/2021 10:47 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
As long as it clears the pad, isn't it better that it explode in the air than on a test stand?

If you have the stage in a test stand and something starts to go wrong you at least have a chance to shut everything down and save the stage and the hardware to investigate the cause.  Not so much when it is midair. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Proesterchen on 04/02/2021 10:48 pm
the brave new world of computational fluid dynamics [...] They just need to practice *actually making the thing* until they can hit those marks, and if they can't manufacture to that tolerance they've got the models to know exactly how much thicker/heavier/stronger the tiles need to be in response.
All models are inherently wrong, that is their nature. You can only hope to improve them to the point where they are usually wrong inside your design margins.

I don't know how far off that target SpaceX are for Starship, but the autogenous vs. Helium and number of Raptors active during the landing sequence changes would suggest a high probability of significant correlation issues.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/02/2021 11:03 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire.
As long as it clears the pad, isn't it better that it explode in the air than on a test stand?

If you have the stage in a test stand and something starts to go wrong you at least have a chance to shut everything down and save the stage and the hardware to investigate the cause.  Not so much when it is midair.
Well of course, that's why it's a test stand, but in order to get to that ability, you have to make the test stand very different from a Starship..

So they do have a test stand for engine development...  But for cluster firing, which is getting into the "the devil is in integration" territory, they chose to build a low cost and much more realistic flying test stand.

In retrospect, that was obviously a good choice.  Show me a test stand that can replicate the problems with the swoop maneuver...

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/03/2021 12:41 am
Show me a test stand that can replicate the problems with the swoop maneuver...
Well, you'd first have to know what those problems are, and as no-one had done the swoop before, that means you have to build and test your flight article before you can build your test stand.

And then one flight gives you one data set, which is probably not sufficient to characterise the problem well enough to make your test stand representative.

So you'll need a few test flights to gather the data necessary to build the test stand that will let you reduce the risk of those first few test flights......

Oh.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/03/2021 12:52 am
https://twitter.com/_brendan_lewis/status/1378137236214980609

Quote
Starship SN11 crash reconstruction! Matched debris locations and time of impact. Seems like the explosion initiated in the CH4 header tank....

@elonmusk @DJSnM @RGVaerialphotos @considercosmos @NASASpaceflight
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aero on 04/03/2021 01:07 am
Where did it get its oxygen from? And was it a detonation or a conflagration?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 04/03/2021 01:19 am
Where did it get its oxygen from? And was it a detonation or a conflagration?

There is a LOX downcomer running through the side of the methane tank and SN11's was flowing fuel to the engines for the landing burn, as well as residuals in the main LOX tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Gliderflyer on 04/03/2021 01:42 am
Where did it get its oxygen from? And was it a detonation or a conflagration?
From the methane tank cam in the live stream, there was what appeared to be large quantities of water vapor in the methane tank. It's possible they didn't purge the air out before fill.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wes_wilson on 04/03/2021 01:52 am
A few more angles on the newest Starship, the either short Starship or long nose in it's custom stand and a selection of homemade gse tanks.

Can someone point me towards a thread if I've missed it?  Has anyone worked the math yet on "short Starship" to see if it's the right size for a tanker starship?  Assuming they shorten to leave no extra empty space. 

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/03/2021 02:19 am
Well of course, that's why it's a test stand, but in order to get to that ability, you have to make the test stand very different from a Starship..

So they do have a test stand for engine development...  But for cluster firing, which is getting into the "the devil is in integration" territory, they chose to build a low cost and much more realistic flying test stand.

In retrospect, that was obviously a good choice.  Show me a test stand that can replicate the problems with the swoop maneuver...

How many explosions and scattering of debris across Boca Chica do you think the FAA is going to tolerate with these flying stands? 

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/03/2021 02:24 am
Well of course, that's why it's a test stand, but in order to get to that ability, you have to make the test stand very different from a Starship..

So they do have a test stand for engine development...  But for cluster firing, which is getting into the "the devil is in integration" territory, they chose to build a low cost and much more realistic flying test stand.

In retrospect, that was obviously a good choice.  Show me a test stand that can replicate the problems with the swoop maneuver...

How many explosions and scattering of debris across Boca Chica do you think the FAA is going to tolerate with these flying stands?
As long as it doesn't endangered public safety (because of damn exclusion zone), why not?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/03/2021 02:39 am
Where did it get its oxygen from? And was it a detonation or a conflagration?
From the methane tank cam in the live stream, there was what appeared to be large quantities of water vapor in the methane tank. It's possible they didn't purge the air out before fill.

You are sure these vapors were not methane vapors?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 04/03/2021 02:46 am
As I understand it, any time something goes boom the FAA verifies that it occurred within the bounds of the preflight risk assessment before green lighting the next flight. Not pro forma by any means as they are serious about it, but also not big problem as long as there are no surprises in the investigation. These are experimental vehicles after all. Booms and debris are part and parcel of the risk.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Gliderflyer on 04/03/2021 02:47 am
Where did it get its oxygen from? And was it a detonation or a conflagration?
From the methane tank cam in the live stream, there was what appeared to be large quantities of water vapor in the methane tank. It's possible they didn't purge the air out before fill.

You are sure these vapors were not methane vapors?
I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/03/2021 03:02 am
A few more angles on the newest Starship, the either short Starship or long nose in it's custom stand and a selection of homemade gse tanks.

Can someone point me towards a thread if I've missed it?  Has anyone worked the math yet on "short Starship" to see if it's the right size for a tanker starship?  Assuming they shorten to leave no extra empty space.
The "short Starship" is just a nose attached to a forward dome.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 04/03/2021 03:14 am

I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.

Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/03/2021 04:18 am
  Enjoying some of the new photos out of Boca China and was interested in folks opinion on SN15 nosecone. Is the joint between nosecone and barrel section of SN15 looking a little rough? I know that SpaceX isn't building show room models yet, and previous builds have had some dimples and dents. The overall build quality has been improving a lot, but this joint looks like it required a lot of "persuasion".

Photo credit is bocachicagal from her post in the 'Boca Chica production updates' thread, post #1160
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dakobed82 on 04/03/2021 05:18 am
Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.

Not following you here.  The preburner is downstream of the regenerative cooling loops; the methane-rich preburner exhaust passes through the turbine and then goes to the main combustion chamber.  Methane for autogenous pressurization is tapped off upstream of the preburner, precisely because you don't want combustion products in your ullage gas.  Since the methane preburner runs fuel-rich, any "extra" oxygen would be consumed immediately, and in quantity would probably overspeed or melt the turbopump.  Oxygen certainly wouldn't have time to wander through plumbing to cause mischief elsewhere.

Assuming SN11 switched back to autogenous pressurization, which seems likely but IIRC hasn't been confirmed, the vapor in the methane tank is not surprising.  It's just like fog produced by warm air moving over cold water; there is a boundary layer between very cold liquid below and warm gas above, and in that transition zone you get condensation resulting in visible vapor.  No ullage gas contamination required.  Subcooled LOX is below CH4's freezing point, so methane frost on the LOX header downcomer is also to be expected.

You wouldn't see fog in normal LN2 or LOX tanks because there the situation is reversed: liquid is very slowly boiling as heat seeps into the tank, and gas is produced at the same temperature (the boiling point) and vented off to prevent overpressure.  In Starship the subcooled liquid methane "wants" to condense the much warmer gas being introduced into the tank.  You also don't see fog in the LOX tank views on Falcon 9 because it uses helium pressurant.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 04/03/2021 07:42 am
  Enjoying some of the new photos out of Boca China and was interested in folks opinion on SN15 nosecone. Is the joint between nosecone and barrel section of SN15 looking a little rough? I know that SpaceX isn't building show room models yet, and previous builds have had some dimples and dents. The overall build quality has been improving a lot, but this joint looks like it required a lot of "persuasion".

Photo credit is bocachicagal from her post in the 'Boca Chica production updates' thread, post #1160

I was going to post something on the same notes the moment I saw Mary's Twitter post.
Something similar came to my mind when I saw the SN11's nosecone as well which was either the diameter of the base of the nose is larger than the barrel diameter or that joint is tough to weld [which I believe can not be the issue]

SN11's nosecone: https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2010717;image
Customized nose: https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2023647;image

EDIT: added a link to the customized nose as well, same thing there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vonbraun on 04/03/2021 09:37 am
  Enjoying some of the new photos out of Boca China and was interested in folks opinion on SN15 nosecone. Is the joint between nosecone and barrel section of SN15 looking a little rough? I know that SpaceX isn't building show room models yet, and previous builds have had some dimples and dents. The overall build quality has been improving a lot, but this joint looks like it required a lot of "persuasion".

Photo credit is bocachicagal from her post in the 'Boca Chica production updates' thread, post #1160

This might be intentional at the moment, it is easier to persuade the metal inwards after mating than outwards prior. I suspect that after the header tanks have been proven out, we will start to see nosecones made from larger pieces, possibly prefab stir-welded like some of the bulkhead panels are.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/03/2021 10:18 am
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2023443;sess=59390

I wonder if they might bolt the base of this contraption down securely and then pull strongly upwards on those flap-substitutes to get an idea of whether the front-flaps/nosecone could support the weight of a complete Starship.

Musk did mention at one point that they are thinking of catching Starship as well as the booster for landing.

[Edit: how should I add a picture from another post into this post?]
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/03/2021 10:22 am
...we will start to see nosecones made from larger pieces, possibly prefab stir-welded like some of the bulkhead panels are.
Can you expand on that? Thought SpaceX was avoiding stir-welding (as in friction-stir welding) for SS?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/03/2021 10:40 am
...
I wonder if they might bolt the base of this contraption down securely and then pull strongly upwards on those flap-substitutes to get an idea of whether the front-flaps/nosecone could support the weight of a complete Starship.
...
Or maybe after reviewing SN9-11 data, they want to do additional ground testing to gain confidence for orbital reentry?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/03/2021 12:10 pm
...
I wonder if they might bolt the base of this contraption down securely and then pull strongly upwards on those flap-substitutes to get an idea of whether the front-flaps/nosecone could support the weight of a complete Starship.
...
Or maybe after reviewing SN9-11 data, they want to do additional ground testing to gain confidence for orbital reentry?
For reentry the vehicle will be belly-first so they' be stressing the flaps in a different direction wouldn't the? That rig doesn't look set up for that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 04/03/2021 01:07 pm
I am concerned for SpaceX.  Maybe Elon needs more computer planning to nail the landings for Starship.

This is my opinion from what I am seeing and reading here.  Maybe I am wrong, but here goes.

Maybe he should get the booster up and running, nail the booster landing with or without legs.  It is huge and can deliver huge payloads to orbit or beyond.

Along with the booster, maybe he should just make a second stage out of Starship, leave off the heat shield, legs, 3 sea level engines, and use this expendable upper stage to get more Starlink satellites in orbit quickly to get more customers for some income to continue Starship development. 

Maybe he should allow for a lower thrust or pressure on Raptor to not have Raptors burn themselves up.  Test some for higher pressures on test stands to get the thrust up instead of RUD's on a lot of Starships.  Seems like a lot of expense to destroy them. 

Develop the moon lander because it doesn't have to do the flip.

Maybe they need to flip earlier and make sure the fuel/lox feeds or unobstructed. 

Anyway, I want to see SpaceX succeed.  I want to see us get to Mars in my lifetime and I am 67 and will be 68 this summer and have many medical conditions.  I know it took him a while to nail the F9 landings.  Seems like going ahead and developing the booster and expendable upper stage while working on the landing would Starlink finished even before nailing the landings. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vonbraun on 04/03/2021 01:10 pm
...we will start to see nosecones made from larger pieces, possibly prefab stir-welded like some of the bulkhead panels are.
Can you expand on that? Thought SpaceX was avoiding stir-welding (as in friction-stir welding) for SS?

I might be wrong about the particular method, but the bulkhead panels (curve shaped joint) is done differently than all the rest. It does not show any grinding or heating marks and based on the images, weldment is on level with the sheet material. Not saying stir welding would be superior or preferred, but prefabricated flat sheet joining has these kinds of advantages.

I think you could combine 2 of those panels similarly at the shop and have the outline geometry match the curved shape. It will require jigs to be built on the fabrication shop, so you would try to avoid it until the final shape is known.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: schuttle89 on 04/03/2021 01:33 pm
I am concerned for SpaceX.  Maybe Elon needs more computer planning to nail the landings for Starship.

This is my opinion from what I am seeing and reading here.  Maybe I am wrong, but here goes.

Maybe he should get the booster up and running, nail the booster landing with or without legs.  It is huge and can deliver huge payloads to orbit or beyond.

Along with the booster, maybe he should just make a second stage out of Starship, leave off the heat shield, legs, 3 sea level engines, and use this expendable upper stage to get more Starlink satellites in orbit quickly to get more customers for some income to continue Starship development. 

Maybe he should allow for a lower thrust or pressure on Raptor to not have Raptors burn themselves up.  Test some for higher pressures on test stands to get the thrust up instead of RUD's on a lot of Starships.  Seems like a lot of expense to destroy them. 

Develop the moon lander because it doesn't have to do the flip.

Maybe they need to flip earlier and make sure the fuel/lox feeds or unobstructed. 

Anyway, I want to see SpaceX succeed.  I want to see us get to Mars in my lifetime and I am 67 and will be 68 this summer and have many medical conditions.  I know it took him a while to nail the F9 landings.  Seems like going ahead and developing the booster and expendable upper stage while working on the landing would Starlink finished even before nailing the landings.

The thing to remember is all of these starships we've seen are pre-production prototypes. SpaceX is learning how to build starships and using the early results to test things out and improve design. The booster is coming and once they solve that there is nothing stopping them from putting up 300-400 starlink sats every time they test reentry for starship. The thing to remember is that sending humans to Mars on starship requires starships being able to land safely, both on Mars and earth, so it's not a step that can be skipped.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/03/2021 01:51 pm
I am concerned for SpaceX.  Maybe Elon needs more computer planning to nail the landings for Starship.

This is my opinion from what I am seeing and reading here.  Maybe I am wrong, but here goes.

Maybe he should get the booster up and running, nail the booster landing with or without legs.  It is huge and can deliver huge payloads to orbit or beyond.

Along with the booster, maybe he should just make a second stage out of Starship, leave off the heat shield, legs, 3 sea level engines, and use this expendable upper stage to get more Starlink satellites in orbit quickly to get more customers for some income to continue Starship development. 

Maybe he should allow for a lower thrust or pressure on Raptor to not have Raptors burn themselves up.  Test some for higher pressures on test stands to get the thrust up instead of RUD's on a lot of Starships.  Seems like a lot of expense to destroy them. 

Develop the moon lander because it doesn't have to do the flip.

Maybe they need to flip earlier and make sure the fuel/lox feeds or unobstructed. 

Anyway, I want to see SpaceX succeed.  I want to see us get to Mars in my lifetime and I am 67 and will be 68 this summer and have many medical conditions.  I know it took him a while to nail the F9 landings.  Seems like going ahead and developing the booster and expendable upper stage while working on the landing would Starlink finished even before nailing the landings.
Out of interest, do you have any reason to believe that SpaceX haven't done as much computer simulation that they can?

Also, do you think that their Starship landing attempts are slowing down their progress towards orbital launch? It seems entirely possible that they are just parallel paths.

I guess both of these boil down to "what do you think you know that SpaceX don't?"
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Niklas Holsti on 04/03/2021 02:28 pm
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2023443;sess=59390

I wonder if they might bolt the base of this contraption down securely and then pull strongly upwards on those flap-substitutes to get an idea of whether the front-flaps/nosecone could support the weight of a complete Starship.

Musk did mention at one point that they are thinking of catching Starship as well as the booster for landing.

[Edit: how should I add a picture from another post into this post?]

I'm wondering if that is an HLS prototype and they intend to mount the lunar-landing engines on the "flaps". The flap movement could be part of the thrust vectoring and give some control, depending on the canting angle of the engines. However, the upper and lower attachment points ("hinges") don't look robust enough for a Starship with cargo and propellants, even in lunar gravity. Also, feeding the engines through flexible hoses/pipes could be difficult. It would, however, save space inside the Starship, and could make the HLS Starship more similar in construction to an ordinary Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/03/2021 03:36 pm
Where did it get its oxygen from? And was it a detonation or a conflagration?
There was a sharp 'crack'. This was a detonation. We don't know if that was the ship or the FTS. My gut sez it sounded like FTS, not the tanks. I'd expect a deeper sound from a tank detonation. Or, it could have been an engine. I've no idea how deep or sharp this would be.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/03/2021 03:49 pm
Seeing sn15 stacking I thought about a thing.

How do they solder the LOx downcomer in the nose part to the part of the downcomer in the tank section, if they have to solder the outer steel wall ? Maybe entering in the small "hatch" in the side of the nosecone. Do we have any information about final work after stacking before rollout?


(BTW, this is my 100th post, thanks to everyone of this beautiful community. I learned so much.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/03/2021 03:54 pm
A few more angles on the newest Starship, the either short Starship or long nose in it's custom stand and a selection of homemade gse tanks.

Can someone point me towards a thread if I've missed it?  Has anyone worked the math yet on "short Starship" to see if it's the right size for a tanker starship?  Assuming they shorten to leave no extra empty space.
The "short Starship" is just a nose attached to a forward dome.
They can add 2 more rings worth of tankage and stay within GTW. Does this count as a shorty or a midsized?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 04/03/2021 03:57 pm
I am concerned for SpaceX.  Maybe Elon needs more computer planning to nail the landings for Starship.

Without going to the specific, I don't think there's cause for concern, they got this. They'll solve this problem, just like they solved all the other problems they have faced previously. Actually exactly one year ago today, SN3 crumbled during pressure test, remember the string of failures back then? SN1/3/4 all failed one way or another, there were great debates on this very forum that whether Elon and SpaceX is losing it and Starship program is doomed. But it all passed, they got better at it and look at the progress they made so far. So my recommendation is don't worry and enjoy the ride.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/03/2021 03:58 pm

I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.

Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.
The autogen tapoff is after the engine cooling loop but before the preburner. If there was O2 in this line there were other problems.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alastairmayer on 04/03/2021 04:01 pm
Seeing sn15 stacking I thought about a thing.

How do they solder the LOx downcomer in the nose part to the part of the downcomer in the tank section, if they have to solder the outer steel wall ? Maybe entering in the small "hatch" in the side of the nosecone. Do we have any information about final work after stacking before rollout?


(BTW, this is my 100th post, thanks to everyone of this beautiful community. I learned so much.)

Not solder, weld.  Two different things. Soldering implies a low-melting point metal used to "glue" two parts together; welding at least partially melts the pieces being joined (and is much stronger).

As for how they weld the downcomer, I imagine that yes, they have someone do that from the inside via a hatch, but I don't know for sure. I'll defer to someone else.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/03/2021 04:08 pm
I am concerned for SpaceX.  Maybe Elon needs more computer planning to nail the landings for Starship.

This is my opinion from what I am seeing and reading here.  Maybe I am wrong, but here goes.

Maybe he should get the booster up and running, nail the booster landing with or without legs.  It is huge and can deliver huge payloads to orbit or beyond.

Along with the booster, maybe he should just make a second stage out of Starship, leave off the heat shield, legs, 3 sea level engines, and use this expendable upper stage to get more Starlink satellites in orbit quickly to get more customers for some income to continue Starship development. 

Maybe he should allow for a lower thrust or pressure on Raptor to not have Raptors burn themselves up.  Test some for higher pressures on test stands to get the thrust up instead of RUD's on a lot of Starships.  Seems like a lot of expense to destroy them. 

Develop the moon lander because it doesn't have to do the flip.

Maybe they need to flip earlier and make sure the fuel/lox feeds or unobstructed. 

Anyway, I want to see SpaceX succeed.  I want to see us get to Mars in my lifetime and I am 67 and will be 68 this summer and have many medical conditions.  I know it took him a while to nail the F9 landings.  Seems like going ahead and developing the booster and expendable upper stage while working on the landing would Starlink finished even before nailing the landings.
That would move them ahead on StarLink but not on SS. Starlink success is woven into SS success but it's a supporting role. Mars is the goal.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/03/2021 04:10 pm

I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.

Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.
The autogen tapoff is after the engine cooling loop but before the preburner. If there was O2 in this line there were other problems.
Emphasis mine.

Yep - that.  If this thing had been so screwed up that O2 was being pumped in through the autogenous pressurization system, I'd frankly be surprised if it got very far off the ground, and we'd be watching them rebuild the suborbital pad (again).  No sane person would design this thing in such a way that that was even a possibility.  As for the presence of fog in the CH4 tank, if its evidence of anything, it shows that had returned to autogenous pressurization.  Its a methane mist, not water.  Note that the nice clear views we've seen in things like, e.g., the F9S2 lox tank, are a result of He pressurization ... the partial pressure of the commodity in question is buffered by the helium pressurant, and so never rises to the dew point.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alex Delderfield on 04/03/2021 04:15 pm
I am concerned for SpaceX.  Maybe Elon needs more computer planning to nail the landings for Starship.

This is my opinion from what I am seeing and reading here.  Maybe I am wrong, but here goes.

Maybe he should get the booster up and running, nail the booster landing with or without legs.  It is huge and can deliver huge payloads to orbit or beyond.

Along with the booster, maybe he should just make a second stage out of Starship, leave off the heat shield, legs, 3 sea level engines, and use this expendable upper stage to get more Starlink satellites in orbit quickly to get more customers for some income to continue Starship development. 

Maybe he should allow for a lower thrust or pressure on Raptor to not have Raptors burn themselves up.  Test some for higher pressures on test stands to get the thrust up instead of RUD's on a lot of Starships.  Seems like a lot of expense to destroy them. 

Develop the moon lander because it doesn't have to do the flip.

Maybe they need to flip earlier and make sure the fuel/lox feeds or unobstructed. 

Anyway, I want to see SpaceX succeed.  I want to see us get to Mars in my lifetime and I am 67 and will be 68 this summer and have many medical conditions.  I know it took him a while to nail the F9 landings.  Seems like going ahead and developing the booster and expendable upper stage while working on the landing would Starlink finished even before nailing the landings.

Ahhh it really is a matter of spending more now to save a LOT later on.

Starship will be a revolution if it performs where SpaceX/Elon need it to perform. They need to be absolutely pushing the limits on every launch with every prototype right now - which is clearly what theyre doing - to develop this the way they need.

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight. The main thing is progress.

If they ease up on goals like youre suggesting then suddenly Starship becomes 'just another rocket' and it really wont change much of anything. It wont revolutionize the aerospace industry. It wont make Starlink as profitable as it could be. It wont take over from Falcon 9 and get the launch rate it needs to peform like an airliner, it wont fly Earth-to-Earth and we'll end up with a small experiemental and likely temporary colony on Mars - rather than having 100s if not 1000s of Starships flying to the red planet to make it our 2nd home.

Just look at how far SpaceX have come, we had Starhopper making its first flight barely 18 months ago, and now we have full size Starships flying around doing flip and burns, with orbit potentially a few months away. Starship wont be fully developed and functioning in just one or two years.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oberonian on 04/03/2021 04:16 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 04/03/2021 04:22 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?

Did you read it on April 1st?

F
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 04/03/2021 04:26 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?
Lol. Where is this “elsewhere”?

There is some state funding ($135 million HLS contract from NASA for lunar Starship), but the VAST majority (several billion $) is from SpaceX self-funding and big commercial investors. (Like Google) And Elon owns a majority voting share of SpaceX.

But this “elsewhere” source would probably call it state funded if SpaceX only got one cent from NASA.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lotick on 04/03/2021 04:31 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?

False. US government (nasa/dod) paid for some tech development/demonstration involved in starship, for example orbital refueling demonstration etc. It seems someone spreading lies to descreditate Elon.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lotick on 04/03/2021 04:37 pm
Orbital refuelling:
https://arstechnica.com/science/2019/07/nasa-agrees-to-work-with-spacex-on-orbital-refueling-technology/
Heat shield:
https://www.teslarati.com/spacex-usaf-starship-heat-shield-research-contract/
Lunar lender:
https://spacenews.com/spacex-wins-contracts-for-lunar-lander-environmental-satellite-launches/
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/03/2021 04:39 pm
Orbital refuelling:
https://arstechnica.com/science/2019/07/nasa-agrees-to-work-with-spacex-on-orbital-refueling-technology/
Heat shield:
https://www.teslarati.com/spacex-usaf-starship-heat-shield-research-contract/
Lunar lender:
https://spacenews.com/spacex-wins-contracts-for-lunar-lander-environmental-satellite-launches/

That's a FRACTION to what SpaceX puts on this project themselves. BTW, getting off topic.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oberonian on 04/03/2021 05:27 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?

False. US government (nasa/dod) paid for some tech development/demonstration involved in starship, for example orbital refueling demonstration etc. It seems someone spreading lies to descreditate Elon.

Right I tought so too.....he claimed to be a man who knows these things worked in White Sands etc.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/03/2021 05:59 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?
Elon put a lot more than a nickel in it. A large part of the funding comes from him personally, via loans backed by Tesla shares.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 04/03/2021 06:01 pm

I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.

Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.
The autogen tapoff is after the engine cooling loop but before the preburner. If there was O2 in this line there were other problems.

Was not aware the autogenous pressurization tapoff was there (I thought it was high pressure methane liquid there, not gas) but makes sense if you can do it that way.

In that case, the oxygen in the methane tank (if indeed that was the source of the detonation) has to have come from the downcomer leaking.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edkyle99 on 04/03/2021 06:03 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lockne on 04/03/2021 08:42 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle

Why wouldn't they survive?

They surely have done single engine full duration fires at McGregor plenty of times. Raptors have performed great during ascent of the 4 high altitude test flights. Even when one engine had issues during SN11's flight, it still completed the entire ascent fine. The issues have been during startup, or due to propellant supply issues.

One thing to keep in mind with all the engine swaps after static fires, we usually don't know exactly why they were swapped. Since Raptor is still under development, limits might be set very conservatively. If any value seems off, why risk it? It's more useful to look into it and potentially catch a failure mode early on. There is a decent chance some of the swapped Raptors could have completed a full duration fire with more aggressive limits - but it would have also been more likely to have a RUD along the way, or to miss and carry on a flaw until it causes a bigger issue. Either way, not every engine swap should be seen as another broken Raptor.

I'm very sure Starship could currently survive a full duration static fire on the right test stand. Firing for longer times doesn't seem to be an issue at all. Nearly all the issues were during startup or the landing flip.

That said, Raptor is definitely still in development. I'm not entirely sure why some people seem surprised by that. I've seen quite a few people thinking they started 'using' Raptor for active testing too early. But they can literally start testing multiple years earlier by developing the engine in parallel to the rocket itself. If they would have waited until Raptor is 'mature', we probably wouldn't even have seen Starhopper yet.

Not to mention, testing in parallel has other benefits, as it makes it a lot easier to make changes to the engine design based on the rocket's requirements, some of which might only be realized during testing. With a mature engine, the design would be a lot more fixed and changes would be a lot more difficult, so the rocket would have to be build around the engine a lot more. Having both under development in parallel allows for a much more optimized end product with a better integrated engine - after all the entire system is the end product, they are not just an engine supplier.

I don't think Raptor is truly a problem child. All in all, it's been performing pretty well. It's still under development, and among the most complex puzzle pieces in the entire system. To me, Raptor has been performing at least as - if not better than - expected in early integrated testing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/03/2021 08:54 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle

So...  should SpaceX just wait until "Raptor is ready" (IYO)?
and meanwhile... what?

The standing army cost of most "comparable" aerospace organizations is higher than what SpaceX is "wasting" on test flights.

What SpaceX is doing is already doing real-life tests with Starship.  They are aware of which problems are caused by Raptor growing pains, which problems are vehicle problems, and they are finding out interactions problems that you can't find out without flying.

And here's the best part!  Since Raptor is "not done" yet, they can feed some lessons back to engine development.

I honestly don't understand what all the griping is about.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/03/2021 09:03 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle
There were 4 Starship test flights with 3 engines each and each completed the ascent profile (which had super long burns) as planned.

I think Raptor is sufficient at this stage (with improvements they've already made for SN15) to reach orbit as reliably as any other clean sheet rocket's first 3 flights are likely to be. There may be an engine-out, and they'll have to make sure to engineer Super Heavy to handle that. But I actually DO think Raptor is good enough now.

Raptor is not, however, proven enough for highly reliable landing. Clearly. But orbit is actually easier. (This is a weird statement to make as orbit is usually the hardest step for most space companies, but in this case I think it's true...)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: philw1776 on 04/03/2021 09:08 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle
There were 4 Starship test flights with 3 engines each and each completed the ascent profile (which had super long burns) as planned.

I think Raptor is sufficient at this stage (with improvements they've already made for SN15) to reach orbit as reliably as any other clean sheet rocket's first 3 flights are likely to be. There may be an engine-out, and they'll have to make sure to engineer Super Heavy to handle that. But I actually DO think Raptor is good enough now.

Raptor is not, however, proven enough for highly reliable landing. Clearly. But orbit is actually easier. (This is a weird statement to make as orbit is usually the hardest step for most space companies, but in this case I think it's true...)

There is only one other company who has demonstrated reliable landings. And their little rocket sprays water out of its nozzle.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Exastro on 04/03/2021 09:30 pm
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle
There were 4 Starship test flights with 3 engines each and each completed the ascent profile (which had super long burns) as planned.

I think Raptor is sufficient at this stage (with improvements they've already made for SN15) to reach orbit as reliably as any other clean sheet rocket's first 3 flights are likely to be. There may be an engine-out, and they'll have to make sure to engineer Super Heavy to handle that. But I actually DO think Raptor is good enough now.

Raptor is not, however, proven enough for highly reliable landing. Clearly. But orbit is actually easier. (This is a weird statement to make as orbit is usually the hardest step for most space companies, but in this case I think it's true...)

Do we have a strong reason to believe Raptor issues have been the cause of any of the Starship failures?  The only clear explanations for them that I'm aware of have to do with propellant feed issues: low fuel pressure, helium contamination, etc.  We did hear about one engine not making full power on ascent, but we don't know that was because of the engine itself, or that it was directly related to the landing failure, unless I missed something.

Ancient, vaguely remembered history: In the 1980s there was a lot of talk about how conical SSTOs that reenter nose-first would have to perform a flip maneuver to land, and that was one of the big risk items that discouraged their development.  Looks like folks back then had good reason to be concerned.  I don't recall anybody suggesting that the way to work through it was to build a shipyard that could rapidly crank out cheap prototypes.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/03/2021 10:57 pm
They retrofitted the thrust simulator for the new thrust puck and SN15 is gonna pass through some retro testing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Malatrope on 04/03/2021 11:07 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)


Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/03/2021 11:11 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)



Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...

Actually they have two places ready to park them.

Edit to fix typo.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/03/2021 11:20 pm
They retrofitted the thrust simulator for the new thrust puck and SN15 is gonna pass through some retro testing.

I thought this thrust simulator was for the booster, no?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/03/2021 11:23 pm
... I don't recall anybody suggesting that the way to work through it was to build a shipyard that could rapidly crank out cheap prototypes.

Then vs. now not really comparable.  One dimension is cheap-rapid manufacturing to provide the expected volume and cost needed for Musk's Mars ambitions.  Refinement of that dimension leads to the capability for a "hardware rich" test campaign.  That is relevant because the SS/SH effort has parallel development across multiple dimensions: manufacturing; engines; airframe; and of course performance of the integrated solution.

In any case, would bet that many back-then would have jumped at the chance for type of capabilities SpaceX is providing to accelerate DT&E.  But attitudes-approaches-$ were different back then.  About the only area you would have heard discussion of "volume" and "cost" in the same sentence would also have included "ICBM".  For an example of this type of rapid-iterative development, you probably need to go back to the late 50's and early 60's--when we blew up quite a bit of stuff, but team's still moved forward (with $ courtesy of USG).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Malatrope on 04/03/2021 11:28 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)



Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...

Actually they have to places ready to park them.

I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bronconut on 04/03/2021 11:40 pm
Raptor is still in development and doing good in my opinion. What other engine of this size has been asked to go up, swan dive back fire and land at the last second?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lotick on 04/03/2021 11:45 pm
Ancient, vaguely remembered history: In the 1980s there was a lot of talk about how conical SSTOs that reenter nose-first would have to perform a flip maneuver to land, and that was one of the big risk items that discouraged their development.  Looks like folks back then had good reason to be concerned.  I don't recall anybody suggesting that the way to work through it was to build a shipyard that could rapidly crank out cheap prototypes.

80th's attempt was almost half-century ago, SpaceX now have hudge advantages, not only because they think out of the box but also because computer technologies had huge progress wich means another level of avionics, computer simulations, etc.
I mean it's incorrect comparison back then they just weren't ready for this.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CruddyCuber on 04/04/2021 12:18 am
Thrust simulator at Pad A

Credit LabPadre

If I'm understanding this correctly, then this means the thrust simulator will be used to test SN15's new thrust puck design, right?  Or will BN2's thrust puck be tested at suborbital pad A, rather than the orbital pad?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/04/2021 12:30 am
Thrust simulator at Pad A

Credit LabPadre

If I'm understanding this correctly, then this means the thrust simulator will be used to test SN15's new thrust puck design, right?  Or will BN2's thrust puck be tested at suborbital pad A, rather than the orbital pad?
Pad A is the next to be used for SN15. Also the ram has three hydraulics
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/04/2021 12:33 am
Thrust simulator at Pad A

Credit LabPadre

If I'm understanding this correctly, then this means the thrust simulator will be used to test SN15's new thrust puck design, right?  Or will BN2's thrust puck be tested at suborbital pad A, rather than the orbital pad?

Same thing I'm wondering. I'm confused because it looks like there are 8 attachment things (I don't know what to call them) and the booster has 8 engines on the inside ring. However, this thing is going to pad A which implies it will be used for SN15, + the timing makes sense for SN15 as well. Can someone explain how this thrust simulator works if it's for SN15?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/04/2021 01:00 am
They retrofitted the thrust simulator for the new thrust puck and SN15 is gonna pass through some retro testing.

I thought this thrust simulator was for the booster, no?

No, sorry. They are rolling out SN15, BN1 may not even make out of the high bay sadly. Thrust simulator for the booster needs at least 8 mounting points, this one is the old one with only 3.

But it did get a GIANT new hydraulic cylinder.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/04/2021 01:02 am
Thrust simulator at Pad A

Credit LabPadre

If I'm understanding this correctly, then this means the thrust simulator will be used to test SN15's new thrust puck design, right?  Or will BN2's thrust puck be tested at suborbital pad A, rather than the orbital pad?

Same thing I'm wondering. I'm confused because it looks like there are 8 attachment things (I don't know what to call them) and the booster has 8 engines on the inside ring. However, this thing is going to pad A which implies it will be used for SN15, + the timing makes sense for SN15 as well. Can someone explain how this thrust simulator works if it's for SN15?

It has 8 hooks, but only 3 engine mounts.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/04/2021 01:19 am
Thrust simulator at Pad A

Credit LabPadre

If I'm understanding this correctly, then this means the thrust simulator will be used to test SN15's new thrust puck design, right?  Or will BN2's thrust puck be tested at suborbital pad A, rather than the orbital pad?

Same thing I'm wondering. I'm confused because it looks like there are 8 attachment things (I don't know what to call them) and the booster has 8 engines on the inside ring. However, this thing is going to pad A which implies it will be used for SN15, + the timing makes sense for SN15 as well. Can someone explain how this thrust simulator works if it's for SN15?

It has 8 hooks, but only 3 engine mounts.
Just took a good look at BCGs latest picture of this thing.  The structural framework has six main vertical support post with lifting points.  Three old yellow hydraulic rams are positioned for engine trust simulation, while a fourth central ram (the one with the blue load cell) attaches to the TVC interface plate.   Other than the minutiae of the structural framework, it's not all that different from the previous version.  I'm really not sure where anyone is seeing 8-fold anything on this one.  Its' clearly for SN15.  They may make another unit for testing BNx, but this isn't it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Exastro on 04/04/2021 01:26 am
... I don't recall anybody suggesting that the way to work through it was to build a shipyard that could rapidly crank out cheap prototypes.

Then vs. now not really comparable.  One dimension is cheap-rapid manufacturing to provide the expected volume and cost needed for Musk's Mars ambitions.  Refinement of that dimension leads to the capability for a "hardware rich" test campaign.  That is relevant because the SS/SH effort has parallel development across multiple dimensions: manufacturing; engines; airframe; and of course performance of the integrated solution.

In any case, would bet that many back-then would have jumped at the chance for type of capabilities SpaceX is providing to accelerate DT&E.  But attitudes-approaches-$ were different back then.  About the only area you would have heard discussion of "volume" and "cost" in the same sentence would also have included "ICBM".  For an example of this type of rapid-iterative development, you probably need to go back to the late 50's and early 60's--when we blew up quite a bit of stuff, but team's still moved forward (with $ courtesy of USG).


Very true!  The idea that a private business would be willing and able to throw $billions at developing a manned spaceship probably wouldn't have made plausible science fiction in the '80s (but see Heinlein's The Man who Sold the Moon for for a 1950 counterexample).  I sometimes wonder whether Musk has read that and is emulating D.D. Harriman deliberately.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 04/04/2021 01:30 am
The problem with restarts now may be with engines, turbo machinery, etc, are already hot from ascent, then trying to restart them, after a flip could cause some problems.  Coming in from the moon, LEO, or Mars they are not starting until after the flip.  There would be a time delay from a de-orbit burn to a transition to vertical and landing burn.  How much does gravity play in this role?  No one has ever tried this before. 

Shuttle just glided in.  F9 boosters have to make several burns to land, but they do have 9 engines to choose from if one fails. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/04/2021 01:35 am
F9 boosters have to make several burns to land, but they do have 9 engines to choose from if one fails.
They only have 3. The rest can only be ignited from the launch pad GSE
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/04/2021 01:48 am

Just took a good look at BCGs latest picture of this thing.  The structural framework has six main vertical support post with lifting points.  Three old yellow hydraulic rams are positioned for engine trust simulation, while a fourth central ram (the one with the blue load cell) attaches to the TVC interface plate.   Other than the minutiae of the structural framework, it's not all that different from the previous version.  I'm really not sure where anyone is seeing 8-fold anything on this one.  Its' clearly for SN15.  They may make another unit for testing BNx, but this isn't it.

Where you read me saying 8, please read 6, I miscounted.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Zed_Noir on 04/04/2021 01:59 am
F9 boosters have to make several burns to land, but they do have 9 engines to choose from if one fails.
They only have 3

AFAIK, all the Falcon 9 core have always landed on the center engine just before touch down. Unless SpaceX can canted fire one of the other 2 engines with the TEA-TEB plumbing, they need the center engine for the final terminal landing burn.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: docmordrid on 04/04/2021 02:05 am

...F9 boosters have to make several burns to land, but they do have 9 engines to choose from if one fails.

Only 3 Falcon 9 engines are plumbed for the TEA-TEB starting fluid.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/04/2021 02:25 am
  The thrust simulators are impressive devices. Dug up some old pics that may offer some clarity on future booster testing rig.
 
  -First pic: Early in March Dayton Costlow took some pics that were uploaded by 'sciencefan' that show an impressively large unit being delivered. This unit has a similar layout to the one that has been currently moved to the launch stand, but in my judgement looks much bigger. 
 
  -Second pic: A smaller (my opinion) version of this unit is buried deep within the hardware of the test rig that is shown being delivered in the LabPadre stream today (thanks to 'pyrometer' for posting those). This unit can be seen in recent pics by 'bocachicagal'.  'cdebuhr' references this device as attaching to the TVC plate, and can be seen hooked up to the newer large cylinder with the blue load cell.

Pic 1 credit: Dayton Costlow (Reference Boca Chica Production Updates: reply#879)
Pic 2 credit: bocachicagal (Reference Boca Chica Production Updates: reply#1164)

Edit: Check out the pic in BC Production Updates reply #1172 that has workers for scale
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ericgu on 04/04/2021 02:38 am

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.

This is a hugely late reply, but I thought it might be useful...

If the estimated numbers on SH are correct (I'm using the wikipedia numbers), SH with 12 engines and a 60% propellant load  gets 9000 m/s of delta v, so it would be barely SSTO.

If you bump up to 80% propellant, you can get 9800 m/s, but then you're up to 16 engines.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 04/04/2021 02:43 am

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.

This is a hugely late reply, but I thought it might be useful...

If the estimated numbers on SH are correct (I'm using the wikipedia numbers), SH with 12 engines and a 60% propellant load  gets 9000 m/s of delta v, so it would be barely SSTO.

If you bump up to 80% propellant, you can get 9800 m/s, but then you're up to 16 engines.
A few other folks have interpreted it the same way you just did, but I'd like to forward the possibility he meant that it would be used in service of an orbital mission (as in it will yeet an upper stage onwards to orbit) as opposed to self-ejecting from Earth.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/04/2021 03:05 am
  The thrust simulators are impressive devices. Dug up some old pics that may offer some clarity on future booster testing rig.
 
  -First pic: Early in March Dayton Costlow took some pics that were uploaded by 'sciencefan' that show an impressively large unit being delivered. This unit has a similar layout to the one that has been currently moved to the launch stand, but in my judgement looks much bigger. 
 
  -Second pic: A smaller (my opinion) version of this unit is buried deep within the hardware of the test rig that is shown being delivered in the LabPadre stream today (thanks to 'pyrometer' for posting those). This unit can be seen in recent pics by 'bocachicagal'.  'cdebuhr' references this device as attaching to the TVC plate, and can be seen hooked up to the newer large cylinder with the blue load cell.

Pic 1 credit: Dayton Costlow (Reference Boca Chica Production Updates: reply#879)
Pic 2 credit: bocachicagal (Reference Boca Chica Production Updates: reply#1164)

Edit: Check out the pic in BC Production Updates reply #1172 that has workers for scale

It's not a smaller version, it's the exact same piece.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/04/2021 04:00 am
Reply to CamiloPasin: Not the same piece. Study the pictures.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/04/2021 04:37 am
Reply to CamiloPasin: Not the same piece. Study the pictures.

You're right.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/04/2021 04:45 am
  The thrust simulators are impressive devices. Dug up some old pics that may offer some clarity on future booster testing rig.
 
  -First pic: Early in March Dayton Costlow took some pics that were uploaded by 'sciencefan' that show an impressively large unit being delivered. This unit has a similar layout to the one that has been currently moved to the launch stand, but in my judgement looks much bigger. 
 
  -Second pic: A smaller (my opinion) version of this unit is buried deep within the hardware of the test rig that is shown being delivered in the LabPadre stream today (thanks to 'pyrometer' for posting those). This unit can be seen in recent pics by 'bocachicagal'.  'cdebuhr' references this device as attaching to the TVC plate, and can be seen hooked up to the newer large cylinder with the blue load cell.

Pic 1 credit: Dayton Costlow (Reference Boca Chica Production Updates: reply#879)
Pic 2 credit: bocachicagal (Reference Boca Chica Production Updates: reply#1164)

Edit: Check out the pic in BC Production Updates reply #1172 that has workers for scale

It is in fact a 4 pair of TVC mounts version of the one on the TVC thrust simulator used for starship, they are indeed building a booster thrust simulator. It only cover 4 of the 8 engines, but BN2s thrust puck has 8 engine plumbing (at least 6), that would mean, BN2 will have 4 engines only with 4 other engine plumbing shut, or, that 4 pairs of TVC mounts are enough to simulate 8 engines.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oberonian on 04/04/2021 06:41 am
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?
Elon put a lot more than a nickel in it. A large part of the funding comes from him personally, via loans backed by Tesla shares.

Any link to back this up ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 04/04/2021 06:45 am
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?

Where on Earth did you hear this?  ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jak Kennedy on 04/04/2021 07:28 am
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?
Elon put a lot more than a nickel in it. A large part of the funding comes from him personally, via loans backed by Tesla shares.

Any link to back this up ?

Do you have a link to back up your initial post?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MTom on 04/04/2021 07:49 am
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?

Where on Earth did you hear this?  ???

Maybe confused with Tesla batteries? Using nickel instead of cobalt?

"The EV maker intends to use more US-sourced nickel in its cathode battery production and less cobalt."
https://stockhead.com.au/tech/battery-day-tesla-confirms-nickel-as-metal-of-choice/
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/04/2021 09:17 am
Is the development of Starship being hampered by the fact that SpaceX has no test stand in Boca-Chica to do full duration static fires of complete stages?  It seems like usually in the development of other rockets that at some-point in the development cycle you put all the engines on a complete stage and do a full duration static fire. 
Agree.  But one problem may be that Raptor simply isn't yet up to the task.  Could all of the Raptors on a vehicle even survive a full duration test firing?  Raptor a problem child so far, and still seems to be in development itself.

 - Ed Kyle
There were 4 Starship test flights with 3 engines each and each completed the ascent profile (which had super long burns) as planned.

I think Raptor is sufficient at this stage (with improvements they've already made for SN15) to reach orbit as reliably as any other clean sheet rocket's first 3 flights are likely to be. There may be an engine-out, and they'll have to make sure to engineer Super Heavy to handle that. But I actually DO think Raptor is good enough now.

Raptor is not, however, proven enough for highly reliable landing. Clearly. But orbit is actually easier. (This is a weird statement to make as orbit is usually the hardest step for most space companies, but in this case I think it's true...)

Do we have a strong reason to believe Raptor issues have been the cause of any of the Starship failures?  The only clear explanations for them that I'm aware of have to do with propellant feed issues: low fuel pressure, helium contamination, etc.  We did hear about one engine not making full power on ascent, but we don't know that was because of the engine itself, or that it was directly related to the landing failure, unless I missed something.

Ancient, vaguely remembered history: In the 1980s there was a lot of talk about how conical SSTOs that reenter nose-first would have to perform a flip maneuver to land, and that was one of the big risk items that discouraged their development.  Looks like folks back then had good reason to be concerned.  I don't recall anybody suggesting that the way to work through it was to build a shipyard that could rapidly crank out cheap prototypes.

Yes, because sn9 second engine failed to relight because of a problem in LOx preburner. Since sn11 exploded before the flip  if its failure was caused by a raptor the cause of this raptor problem can't be a propellant feed problem (before the flip we never saw propellant feed issues).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ioncloud9 on 04/04/2021 11:53 am
SN11 was likely destroyed by a failure of a tank to hold pressure and burst. Had it been a raptor exploding the lox and methane tanks would be mostly intact but crumpled like SN10, not broken into tiny pieces of debris with the nose cone completely sheared off. I would guess the explosion originated at the header tank. Header tank failure would cause the common bulkhead to break apart and the vapors to ignite.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BT52 on 04/04/2021 12:45 pm
Still im for 12m diameter rocket. That booster height scares hell out of me. :d Still i thnk 9m is much more controllable in air with flaps due momentum arms. Even inertia is bigger . Hell i give up. Its hard physics juggling act. I hope SpaceX is sure into decision and overall assessment of concept. But still could be nice if they would jut Yeet 9m in bin. Just because the forum would lose it heads and cure by 30% mine Acrophobia. :D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/04/2021 01:10 pm
SN11 was likely destroyed by a failure of a tank to hold pressure and burst. Had it been a raptor exploding the lox and methane tanks would be mostly intact but crumpled like SN10, not broken into tiny pieces of debris with the nose cone completely sheared off. I would guess the explosion originated at the header tank. Header tank failure would cause the common bulkhead to break apart and the vapors to ignite.

Yes, surely sn11 exploded due to an explosion and resulting overpressure in the tanks,  I suggested that a raptor problem could cause the explosion in the tanks (maybe a raptor powerhead explosion that breaks the downcomer and ignites the methane in the header).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/04/2021 01:22 pm
I read elsewhere that this Starship project is state funded so Elon Musk is not putting a nickle on it ?

True or false ?
Elon put a lot more than a nickel in it. A large part of the funding comes from him personally, via loans backed by Tesla shares.

Any link to back this up ?

Please post your questions in appropriate Forum Threads.  The Texas Prototypes thread is not the appropriate thread to discuss Starship funding.

Go read:
https://forum.nasaspaceflight.com/index.php?topic=46656.0
https://forum.nasaspaceflight.com/index.php?topic=49963.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Brovane on 04/04/2021 02:22 pm
Well of course, that's why it's a test stand, but in order to get to that ability, you have to make the test stand very different from a Starship..

So they do have a test stand for engine development...  But for cluster firing, which is getting into the "the devil is in integration" territory, they chose to build a low cost and much more realistic flying test stand.

In retrospect, that was obviously a good choice.  Show me a test stand that can replicate the problems with the swoop maneuver...

How many explosions and scattering of debris across Boca Chica do you think the FAA is going to tolerate with these flying stands?
As long as it doesn't endangered public safety (because of damn exclusion zone), why not?

Didn't some of the debris from the recent test land in Boca Chica State park and other sensitive wildlife areas? 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/04/2021 02:36 pm
Well of course, that's why it's a test stand, but in order to get to that ability, you have to make the test stand very different from a Starship..

So they do have a test stand for engine development...  But for cluster firing, which is getting into the "the devil is in integration" territory, they chose to build a low cost and much more realistic flying test stand.

In retrospect, that was obviously a good choice.  Show me a test stand that can replicate the problems with the swoop maneuver...

How many explosions and scattering of debris across Boca Chica do you think the FAA is going to tolerate with these flying stands?
As long as it doesn't endangered public safety (because of damn exclusion zone), why not?

Didn't some of the debris from the recent test land in Boca Chica State park and other sensitive wildlife areas?
Didn't literally two major orbital launch site in US were also within the state park/wildlife refuge?

https://www.fws.gov/refuge/Merritt_Island/

https://en.wikipedia.org/wiki/Vandenberg_State_Marine_Reserve?wprov=sfla1
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barnalby on 04/04/2021 03:27 pm
Don't forget Wallops Island!  It's next to Assateague/Chincoteague national seashores and is right on top of the Wallops Island National Wildlife Refuge and they're still flying Antares there even after it had it's little RUD in 2015.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/04/2021 04:50 pm

I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.

Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.
The autogen tapoff is after the engine cooling loop but before the preburner. If there was O2 in this line there were other problems.

Was not aware the autogenous pressurization tapoff was there (I thought it was high pressure methane liquid there, not gas) but makes sense if you can do it that way.

In that case, the oxygen in the methane tank (if indeed that was the source of the detonation) has to have come from the downcomer leaking.
I'm far from being an expert in explosions and the audio was far from being studio quality. The sharp crack tells me that it was relatively small, and probably high explosives. Admittedly while being in ignorance of what might come of different engine RUD scenarios. There was no double tap that would indicate an engine blowing and taking out a tank.


If you go back to SN4, the leaking methane blew under the ship followed by a larger detonation from the tank. A double tap on the order of 10's of milliseconds. My surmise is the bottom dome/puck we're driven up disrupting the downcomer and creating a lethal fuel oxygen munition and second contained detonation. I would expect a repeat if the engine blew.


IMO, if O2 were leaking into the methane tank there would be an explosion similar to the second tap. The O2 would build up until there was an ignition source. If it were to leak into the header the same would happen but with a deeper and less concussive sound of an explosion into a large not particularly resonant cavity.


If the FTS were to blow it would be a sharp crack followed by a conflagration of the remaining propellant. While this is not what Elon said about a RUD, it's not inconsistent.


Again, I'm not an explosives expert but I've been around a few explosions (or more accurately, they've been around me) and I know a bit about sound.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/04/2021 04:58 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)



Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...

Actually they have to places ready to park them.

I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
They're available now. Some assembly required.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 04/04/2021 05:02 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)



Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...

Actually they have to places ready to park them.

I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
They're available now. Some assembly required.

"Barely used. Only 10km on the odometer"
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/04/2021 06:07 pm
I'm curious as to the testing that SN15 will be subjected to before flight.

With the 100's of changes that EM mentioned I would expect they go back to pressure and cryotests and maybe multiple static fires before trying to fly SN15.

Very soon they are going to want to get Starships back in 1 piece so they can make more flights and widen the envelope.

Orbital attempt clock is ticking, 25% of 2021 is over now.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wagner on 04/04/2021 07:51 pm
SN11 was likely destroyed by a failure of a tank to hold pressure and burst. Had it been a raptor exploding the lox and methane tanks would be mostly intact but crumpled like SN10, not broken into tiny pieces of debris with the nose cone completely sheared off. I would guess the explosion originated at the header tank. Header tank failure would cause the common bulkhead to break apart and the vapors to ignite.
Are you suggesting they got a bit overzealous with the header tank pressurization system?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: especedespace on 04/04/2021 08:07 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)



Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...

Actually they have to places ready to park them.

I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
save a few bocks for transporting the device
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Bob Shaw on 04/04/2021 08:13 pm

(snip)

So what Im trying to say is that theyre doing everything correct at the moment, even if it means losing vehicles on every flight.

(snip)



Well, I agree, but it might also be pointed out that at the rate they're making the dang things they have to blow them up! They don't have anyplace to park them...

Actually they have to places ready to park them.

I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
save a few bocks for transporting the device

This is, of course, how Delos D Harriman eventually finagled his way to Luna in RAH's 'Rocketship Galileo'! All that's needed on top is a spacesuit, and he will travel that glory road!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: HVM on 04/04/2021 08:37 pm
SN11 was likely destroyed by a failure of a tank to hold pressure and burst. Had it been a raptor exploding the lox and methane tanks would be mostly intact but crumpled like SN10, not broken into tiny pieces of debris with the nose cone completely sheared off. I would guess the explosion originated at the header tank. Header tank failure would cause the common bulkhead to break apart and the vapors to ignite.
But where is Raptor SN52 then? It seems to be disbanded somewhere...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CJ on 04/04/2021 08:56 pm
If indeed a Raptor failure caused SN11's demise (as the excellent new NSF article indicates), IMHO we're seeing proof that wrapping engines in Kevlar or similar (such as on F9) is a very worthwhile thing to do on operational (non-prototype) vehicles. 

As to why SpaceX has not been doing so on the Starship prototypes - my theory is that it's a tradeoff; the engine cameras we see on their streams are for observing the Raptors in operation, something that could not be done were the engines wrapped/isolated.  So, SpaceX is accepting an additional risk of LOV in order to acquire as much data as they can (which is what prototypes are for).

 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kevin9 on 04/04/2021 09:09 pm
Does anyone thing the welded on tile pins to the outside of the pressurized tanks effects its structural integrity? The number of pins applied has increased in surface area with each starship and the tanks temperatures may play a part in the metals condition. I dont remember the tank being tested with a full coverage of the pins under pressure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 04/04/2021 09:18 pm


I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
save a few bocks for transporting the device

This is, of course, how Delos D Harriman eventually finagled his way to Luna in RAH's 'Rocketship Galileo'! All that's needed on top is a spacesuit, and he will travel that glory road!

While I appreciate the multiple RAH references, D. D. Harriman's death was a tragedy. Having spent his life creating all the technology and business needed to make Luna humanities second home, he was never allowed to leave Earth by insurance, business and later family members hounding him. He had to runaway, find some shady guys to front buying a used ship from literally himself and then be shipped as cargo. He has to sneak onto the Moon he essentially owned and died in the attempt. I can not imagine a more cursed demise that could befall a man.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/04/2021 11:24 pm

I'll admit I've never seen liquid methane, but I've seen both LOX and LN2, and they don't look like that. I've only seen the white clouds form when air is coming in contact with the cold temperatures and the water starts condensing out (if you have a cup of cryo liquid, and the ullage in the cup is comprised purely of boiloff, the white vapor will only form on the very top where the air hits it).

I would also bet it wasn't methane vapors condensing on the LOX line. When LOX condenses on the LN2 lines (similar temp difference), it doesn't form clouds, it just rains off.

Probably beating a dead horse since I mentioned my theory before, but if the fuel preburner was passing extra Oxygen or LOX into the regenerative system, it would result in not only GOX but also water (and other combustion products like CO2) in the methane tank ullage.
The autogen tapoff is after the engine cooling loop but before the preburner. If there was O2 in this line there were other problems.

Was not aware the autogenous pressurization tapoff was there (I thought it was high pressure methane liquid there, not gas) but makes sense if you can do it that way.

In that case, the oxygen in the methane tank (if indeed that was the source of the detonation) has to have come from the downcomer leaking.
I'm far from being an expert in explosions and the audio was far from being studio quality. The sharp crack tells me that it was relatively small, and probably high explosives. Admittedly while being in ignorance of what might come of different engine RUD scenarios. There was no double tap that would indicate an engine blowing and taking out a tank.


If you go back to SN4, the leaking methane blew under the ship followed by a larger detonation from the tank. A double tap on the order of 10's of milliseconds. My surmise is the bottom dome/puck we're driven up disrupting the downcomer and creating a lethal fuel oxygen munition and second contained detonation. I would expect a repeat if the engine blew.


IMO, if O2 were leaking into the methane tank there would be an explosion similar to the second tap. The O2 would build up until there was an ignition source. If it were to leak into the header the same would happen but with a deeper and less concussive sound of an explosion into a large not particularly resonant cavity.


If the FTS were to blow it would be a sharp crack followed by a conflagration of the remaining propellant. While this is not what Elon said about a RUD, it's not inconsistent.


Again, I'm not an explosives expert but I've been around a few explosions (or more accurately, they've been around me) and I know a bit about sound.

Similar.  I heard it first hand, and it was both sharp and relatively minor.  I did not expect to see SS11 in so many parts.  By the sound alone, I'd have thought it was a charge.  Given the results though I have to go with fuel-air mixture.

It most certainly did not sound like it broke up and then fireballed.  Airspeed at the time of restart was not high either, so aerodynamic forces would not have shredded it like that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Skyway on 04/05/2021 01:06 am
But where is Raptor SN52 then? It seems to be disbanded somewhere...

My bet is that it is under the nose.  ;D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/05/2021 02:30 am


I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
save a few bocks for transporting the device

This is, of course, how Delos D Harriman eventually finagled his way to Luna in RAH's 'Rocketship Galileo'! All that's needed on top is a spacesuit, and he will travel that glory road!

While I appreciate the multiple RAH references, D. D. Harriman's death was a tragedy. Having spent his life creating all the technology and business needed to make Luna humanities second home, he was never allowed to leave Earth by insurance, business and later family members hounding him. He had to runaway, find some shady guys to front buying a used ship from literally himself and then be shipped as cargo. He has to sneak onto the Moon he essentially owned and died in the attempt. I can not imagine a more cursed demise that could befall a man.

Guys, if you’re going to go off topic and make Heinlein references, at least get the name of the story right. The one you’re thinking of is “The Man Who Sold the Moob“. “Rocketship Galileo” was a juvie novel written for young boys set in the same general alternate timeline. Totally different story, however.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/05/2021 02:45 am

Guys, if you’re going to go off topic and make Heinlein references, at least get the name of the story right. The one you’re thinking of is “The Man Who Sold the Moob“.
Now, that's funny.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/05/2021 03:33 am

Guys, if you’re going to go off topic and make Heinlein references, at least get the name of the story right. The one you’re thinking of is “The Man Who Sold the Moob“.
Now, that's funny.
Who's the noob? (And why is he funny?)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 04/05/2021 04:10 am


I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
save a few bocks for transporting the device

This is, of course, how Delos D Harriman eventually finagled his way to Luna in RAH's 'Rocketship Galileo'! All that's needed on top is a spacesuit, and he will travel that glory road!

While I appreciate the multiple RAH references, D. D. Harriman's death was a tragedy. Having spent his life creating all the technology and business needed to make Luna humanities second home, he was never allowed to leave Earth by insurance, business and later family members hounding him. He had to runaway, find some shady guys to front buying a used ship from literally himself and then be shipped as cargo. He has to sneak onto the Moon he essentially owned and died in the attempt. I can not imagine a more cursed demise that could befall a man.

Guys, if you’re going to go off topic and make Heinlein references, at least get the name of the story right. The one you’re thinking of is “The Man Who Sold the Moob“. “Rocketship Galileo” was a juvie novel written for young boys set in the same general alternate timeline. Totally different story, however.

The "Man who sold the Moon" was the main story but DD's death is "Requiem" a short story published in book form as part of the Green Hills of Earth collection. But considering the three other titles mashed in, perhaps the mashup was the point.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: HVM on 04/05/2021 10:03 am
But where is Raptor SN52 then? It seems to be disbanded somewhere...

My bet is that it is under the nose.  ;D
I checked under there, and only thing I find was a mustache and bit of breakfast.


Guys, if you’re going to go off topic and make Heinlein references, at least get the name of the story right. The one you’re thinking of is “The Man Who Sold the Moob“.
Now, that's funny.
Who's the noob? (And why is he funny?)
Also, why are you all speaking about Man-Boobs e.g. Moobs? I think Heinlein would be against them. He would want citizens to be fit and healthy and ready for military service...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: HVM on 04/05/2021 11:09 am
https://twitter.com/elonmusk/status/1379022709737275393
So Raptor 52 had uncontained engine failure, and somehow blow up the fuel header tank too.

Example Antares NK-33 turbopump failure was more contained, tanks burst only when vehicle hit the ground.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Remes on 04/05/2021 11:28 am
I'm far from being an expert in explosions and the audio was far from being studio quality. The sharp crack tells me that it was relatively small, and probably high explosives. Admittedly while being in ignorance of what might come of different engine RUD scenarios. There was no double tap that would indicate an engine blowing and taking out a tank.

Have you listened to this recording (at 3:28):

https://youtu.be/l4eawtvznbc?t=208

That does sound like a double tap to me (if we are talking about the same thing). On other recordings I couldn't hear it (some far away, some peaking, ...). This recording is close and has studio quality.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Norm38 on 04/05/2021 11:54 am
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Poseidon on 04/05/2021 11:59 am
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.
It sounds like the leak was on the Raptor itself, not the SN11, so...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/05/2021 12:14 pm

Guys, if you’re going to go off topic and make Heinlein references, at least get the name of the story right. The one you’re thinking of is “The Man Who Sold the Moob“.
Now, that's funny.

Damn typos - I swear to Crom, autocorrect on the iPad is getting worse with every passing month … :) 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 04/05/2021 12:16 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.
It sounds like the leak was on the Raptor itself, not the SN11, so...

Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/05/2021 12:39 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.
It sounds like the leak was on the Raptor itself, not the SN11, so...

Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor
It's encouraging that the problem is being fixed "6 ways to Sunday". Sounds like they are all over it belt and braces on both the Raptor and the pipework. I doubt they will get this particular problem again (if they do I sure would not fancy being the guy responsible for the fix).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/05/2021 01:10 pm


https://twitter.com/elonmusk/status/1379022709737275393

Quote
Ascent phase, transition to horizontal & control during free fall were good.

A (relatively) small CH4 leak led to fire on engine 2 & fried part of avionics, causing hard start attempting landing burn in CH4 turbopump.

This is getting fixed 6 ways to Sunday.

For those unfamiliar with the expression "Six ways to Sunday" like myself.

Quote
The American expression 'Six ways to Sunday' is used with more than one meaning. Most people use it to mean 'in every possible way, with every alternative examined', as in "we checked him out six ways to Sunday before offering him that big loan"

Given Elon's penchant for the literal, I wouldn't be surprised if there were *at least* six separate fixes being made here.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Bob Shaw on 04/05/2021 01:11 pm
Apologies, it was of course 'The Man who sold the Moon' - and Harriman died on the Moon, 'though not necessarily at the point of impact'. Hmmm...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sucramdi on 04/05/2021 01:16 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.
It sounds like the leak was on the Raptor itself, not the SN11, so...

Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor
It's encouraging that the problem is being fixed "6 ways to Sunday". Sounds like they are all over it belt and braces on both the Raptor and the pipework. I doubt they will get this particular problem again (if they do I sure would not fancy being the guy responsible for the fix).

I bet those new, sleeker Raptors that Mary spotted most recently have a lot of tweaks that the flight team is eager to start working with. We've seen what looked like minor engine fires all the way back to SN5 so there was definitely time to address the cause.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/05/2021 01:19 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/05/2021 01:25 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.


Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor

It sounds like the leak was on the Raptor itself, not the SN11, so...
For me sounds like the leak was on the raptor, because the fire was on the raptor. So, strangely the theory I was supporting somewath was true. The explosion then arrived to the CH4 header via the downcomer. Could be possible that an hard start in CH4 turbopomp created a "shockwave" in the plumbing that then caused a rupture in a weak poin in the CH4 header? Maybe I'm wrong thinking that the explosion started in fuel header tank, is the separation betweeen the two halves of it  a sufficient proof of that?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 04/05/2021 01:29 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.


Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor

It sounds like the leak was on the Raptor itself, not the SN11, so...
For me sounds like the leak was on the raptor, because the fire was on the raptor. So, strangely the theory I was supporting somewath was true. The explosion then arrived to the CH4 header via the downcomer. Could be possible that an hard start in CH4 turbopomp created a "shockwave" in the plumbing that then caused a rupture in a weak poin in the CH4 header? Maybe I'm wrong thinking that the explosion started in fuel header tank, is the separation betweeen the two halves of it  a sufficient proof of that?

Please re-read the quote from Elon:

"A (relatively) small CH4 leak led to fire on engine 2..."
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/05/2021 01:34 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.
It sounds like the leak was on the Raptor itself, not the SN11, so...

Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor
It's encouraging that the problem is being fixed "6 ways to Sunday". Sounds like they are all over it belt and braces on both the Raptor and the pipework. I doubt they will get this particular problem again (if they do I sure would not fancy being the guy responsible for the fix).
The great benefit of working for SpaceX (likely) is that everyone owns the problems. Not a manager or a process.

I’m sure everyone working on the Raptor’s will incentivised to resolve this issue and the “six” before SN15 takes off. As part of this staging of builds and just going ahead (even with known bugs) is you continually improve. No doubt they’ll be some retrofitting based on what happened to SN11 to improve design two/three versions ahead.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: kttopdad on 04/05/2021 01:57 pm
Very true!  The idea that a private business would be willing and able to throw $billions at developing a manned spaceship probably wouldn't have made plausible science fiction in the '80s (but see Heinlein's The Man who Sold the Moon for for a 1950 counterexample).  I sometimes wonder whether Musk has read that and is emulating D.D. Harriman deliberately.

I asked Elon once if he'd read The Man who Sold the Moon.  He hadn't.  I wonder if he's read it in the decade since...  He may have no idea what lurks in his future if the sci-fi muses are guiding his journey!   :o
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Norm38 on 04/05/2021 02:33 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 04/05/2021 03:00 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

That depends on what's fried.  Maybe a sensor was fried and that's what Elon called "avionics", since it's part of that system.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 04/05/2021 03:06 pm
If you watch the SpaceX SN11 launch feed https://www.youtube.com/watch?v=gjCSJIAKEPM (https://www.youtube.com/watch?v=gjCSJIAKEPM)

you can see the leak appear rather suddenly on Raptor SN52 at around timestamp 6:12 or approx 25.8 seconds into flight, and start burning material other than CH4 before they switch the feed to the CH4 tank internals.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/05/2021 03:07 pm
Given Elon's penchant for the literal, I wouldn't be surprised if there were *at least* six separate fixes being made here.
..and if they'll also be done applying them by Sunday.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: awests on 04/05/2021 03:58 pm
If you watch the SpaceX SN11 launch feed https://www.youtube.com/watch?v=gjCSJIAKEPM (https://www.youtube.com/watch?v=gjCSJIAKEPM)

you can see the leak appear rather suddenly on Raptor SN52 at around timestamp 6:12 or approx 25.8 seconds into flight, and start burning material other than CH4 before they switch the feed to the CH4 tank internals.
Haven’t we seen fires in the engine bay before? What makes this one special?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 04/05/2021 04:08 pm
I for one am happy it was apparently not a methane tank detonation-- but I am surprised a hard start was so energetic, enough to obliterate the tanks but keep the raptors & skirts relatively together.

Perhaps once whatever debris from the engine RUD punched up into the methane tank, the tank BLEVE did the rest.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/05/2021 04:44 pm
I for one am happy it was apparently not a methane tank detonation-- but I am surprised a hard start was so energetic, enough to obliterate the tanks but keep the raptors & skirts relatively together.

Perhaps once whatever debris from the engine RUD punched up into the methane tank, the tank BLEVE did the rest.

That was not stated.

A hard start of Raptor led to the destruction of SN11.  I don't think that an engine explosion can directly shred the tank structure like that.  I think the engine RUD led to a tank explosion, either by shockwave propagation through fluid that failed the common bulkhead, or through the downcomer failing the header tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/05/2021 05:27 pm
If you watch the SpaceX SN11 launch feed https://www.youtube.com/watch?v=gjCSJIAKEPM (https://www.youtube.com/watch?v=gjCSJIAKEPM)

you can see the leak appear rather suddenly on Raptor SN52 at around timestamp 6:12 or approx 25.8 seconds into flight, and start burning material other than CH4 before they switch the feed to the CH4 tank internals.

From the attachment I saw, right befor the fire start, a small bright zone travelling arounf that pipe. What is it? Is it just a visual effect (nothing real)?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 04/05/2021 05:44 pm
If you watch the SpaceX SN11 launch feed https://www.youtube.com/watch?v=gjCSJIAKEPM (https://www.youtube.com/watch?v=gjCSJIAKEPM)

you can see the leak appear rather suddenly on Raptor SN52 at around timestamp 6:12 or approx 25.8 seconds into flight, and start burning material other than CH4 before they switch the feed to the CH4 tank internals.
Haven’t we seen fires in the engine bay before? What makes this one special?

It's not a normal fire, it's a sudden event of fire coming from a leak... We have never seen a sudden event like this before... The other fires are just wire insulation, or other things burning after fire temporarily engulfs the skirt after raptor start/shutdown. This fire was not preceded by any normal engulfing event, it appears out of nowhere and suddenly with quite vigor.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 04/05/2021 05:45 pm
If you watch the SpaceX SN11 launch feed https://www.youtube.com/watch?v=gjCSJIAKEPM (https://www.youtube.com/watch?v=gjCSJIAKEPM)

you can see the leak appear rather suddenly on Raptor SN52 at around timestamp 6:12 or approx 25.8 seconds into flight, and start burning material other than CH4 before they switch the feed to the CH4 tank internals.

From the attachment I saw, right befor the fire start, a small bright zone travelling arounf that pipe. What is it? Is it just a visual effect (nothing real)?

Sunlight peeking through a hole in the skirt as vehicle rotates, nothing big.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sevenperforce on 04/05/2021 06:02 pm
Based on Elon's explanation, my best guess is my earlier guess -- the hard start in the CH4 turbopump sent shrapnel and a shockwave up the methane downcomer.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barnalby on 04/05/2021 06:05 pm
Based on Elon's explanation, my best guess is my earlier guess -- the hard start in the CH4 turbopump sent shrapnel and a shockwave up the methane downcomer.

Could have been enough of a water hammer effect down the relatively strong downcomer to pop the header tank, at which point we got the big bada boom.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/05/2021 06:16 pm
If you watch the SpaceX SN11 launch feed https://www.youtube.com/watch?v=gjCSJIAKEPM (https://www.youtube.com/watch?v=gjCSJIAKEPM)

you can see the leak appear rather suddenly on Raptor SN52 at around timestamp 6:12 or approx 25.8 seconds into flight, and start burning material other than CH4 before they switch the feed to the CH4 tank internals.

From the attachment I saw, right befor the fire start, a small bright zone travelling arounf that pipe. What is it? Is it just a visual effect (nothing real)?

Sunlight peeking through a hole in the skirt as vehicle rotates, nothing big.

What a strange coincidence!

Do we know what raptor is the cause?We know that it was engine number 2, relative to the mounting configuration, but, sice raptors have been installed on sn11 before rollout, do we know what is its serial number? Could the guilty raptor be sn46 (that that has been placed after a swap)?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/05/2021 06:32 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

That depends on what's fried.  Maybe a sensor was fried and that's what Elon called "avionics", since it's part of that system.
I was thinking something more subtle like an overheated transistor, which was then unable to source full current to open a solenoid when commanded.  Unlike a blitzed sensor or a missing heartbeat, heat damage of that kind might be difficult (but not impossible) to detect before the electronics in question are called on to perform.  Could be addressed by additional health sensors, or by changing procedures to allow a safe abort if the solenoid fails when commanded, etc.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pete on 04/05/2021 07:20 pm
I wonder how they will go about avoiding a similar mishap in the future?

Preventing the leak, and thus the fire itself... of course.   
Better packaging & sealing of the sensitive circuitry... of course.
Both of these vulnerabilities would only exist in a rapid-development environment, not production specs.

Better health monitoring of the avionics?... possible. Likely, even, once they have a stable Raptor design and stop fiddling with them!

But... HOW can they protect against an engine RUD, as in this case a hard-start of the methane preburner, from propagating up into the plumbing and header tank? I would think that would require a *big* plumbing redesign? It's not as if you can just put some blast shielding in there, the way you can put between engines to protect them from each other.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SkyRate on 04/05/2021 07:30 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

Another old adage is "never check for an error condition you don't know how to handle". Adding health checks adds complexity, and from EMs "we were too dumb" comment, they clearly had been leaning strongly toward software simplicity for this phase of the test program.
For launch, you should ofc be leaning towards caution, but for the do-or-die landing burn? Nah, send the commands and hope.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aip on 04/05/2021 07:37 pm
I was thinking something more subtle like an overheated transistor, which was then unable to source full current to open a solenoid when commanded.  Unlike a blitzed sensor or a missing heartbeat, heat damage of that kind might be difficult (but not impossible) to detect before the electronics in question are called on to perform.  Could be addressed by additional health sensors, or by changing procedures to allow a safe abort if the solenoid fails when commanded, etc.
Yeah, likely one component or sensor on one board was fried, and there was either no (or a useless) monitoring circuit for that particular failure mode, or the detection circuit wasn't being utilized properly.

So by my count there are at least 6 fixes:

1) keep methane plumbing from leaking (likely addressed with cleaner plumbing on SN15+ raptors)
2) if methane plumbing is leaking (big pressure drop in one section), shut off the engine unless absolutely needed
3) add more heat shielding/insulation to keep the failed part(s) from getting fried if exposed to flames
4) if raptor electronics are sitting in a literal flamethrower, turn off the engine
5) add monitoring circuit(s) to test if component/sensor has failed
6) if monitoring circuit indicates failure, don't attempt to start engine unless absolutely needed

Also, now that they have seen in practice what a methane flamethrower can do, and with a high severity outcome, they'll examine every potential leak location in the system (flamethrower source), and every exposed location (flamethrower sink), and address/mitigate as appropriate. Wouldn't be surprised if this results in dozens of changes.

In the end, SN11 resulted in great data, failing differently than past tests. And even if SN11 had flown perfectly, a second flight might have surfaced the leak and avionics issues, so I maintain that testing SN* until failure is the best use for these test articles.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/05/2021 07:39 pm
But... HOW can they protect against an engine RUD, as in this case a hard-start of the methane preburner, from propagating up into the plumbing and header tank? I would think that would require a *big* plumbing redesign? It's not as if you can just put some blast shielding in there, the way you can put between engines to protect them from each other.

I think they can't. You can implement redundancy, to solve relight problems, but I think the only thing to do against exploding engines is to work on them and make them better. I think there is no way to save the ship if a raptor (combustion chamber or something in the powerhead) explodes. Even the F1 had issues with combustion instability(that is not raptor proble whatever), way worse than raptor. They solved that issues. So IMO SpaceX will solve the issues with raptor, working on them. They have expert engineers.

Whatever 15 raptor flew, and only one exploded. So if there are problems with general raptor design, that are not related with that single raptor (an error during manufacturing) they will be solved.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/05/2021 07:49 pm
I was thinking something more subtle like an overheated transistor, which was then unable to source full current to open a solenoid when commanded.  Unlike a blitzed sensor or a missing heartbeat, heat damage of that kind might be difficult (but not impossible) to detect before the electronics in question are called on to perform.  Could be addressed by additional health sensors, or by changing procedures to allow a safe abort if the solenoid fails when commanded, etc.
Yeah, likely one component or sensor on one board was fried, and there was either no (or a useless) monitoring circuit for that particular failure mode, or the detection circuit wasn't being utilized properly.

So by my count there are at least 6 fixes:

1) keep methane plumbing from leaking (likely addressed with cleaner plumbing on SN15+ raptors)
2) if methane plumbing is leaking (big pressure drop in one section), shut off the engine unless absolutely needed
3) add more heat shielding/insulation to keep the failed part(s) from getting fried if exposed to flames
4) if raptor electronics are sitting in a literal flamethrower, turn off the engine
5) add monitoring circuit(s) to test if component/sensor has failed
6) if monitoring circuit indicates failure, don't attempt to start engine unless absolutely needed

Also, now that they have seen in practice what a methane flamethrower can do, and with a high severity outcome, they'll examine every potential leak location in the system (flamethrower source), and every exposed location (flamethrower sink), and address/mitigate as appropriate. Wouldn't be surprised if this results in dozens of changes.

In the end, SN11 resulted in great data, failing differently than past tests. And even if SN11 had flown perfectly, a second flight might have surfaced the leak and avionics issues, so I maintain that testing SN* until failure is the best use for these test articles.

I agree with points 1,6,3   

Points 3,4: During sn10 launch the first attempt was aborted at t=-0.1 s because of higher than specification thrust from an engine. So I think they already have a conservative limits, and severe controls over the engine status. But I have no information to support that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacevalley27 on 04/05/2021 08:05 pm
Is known roughly how is high GSE 1?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/05/2021 08:10 pm
I freaking love the GSE tanks. 

How cheap is this for SpaceX versus commercial tanks. 

Let's get the rest headed for the pad not too!

Love it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/05/2021 08:14 pm
Is known roughly how is high GSE 1?

1 ring is 6ft or 1,8288m high. 15 rings + top dome should be around 30-31m high.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: smndk on 04/05/2021 08:37 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

Another old adage is "never check for an error condition you don't know how to handle". Adding health checks adds complexity, and from EMs "we were too dumb" comment, they clearly had been leaning strongly toward software simplicity for this phase of the test program.
For launch, you should ofc be leaning towards caution, but for the do-or-die landing burn? Nah, send the commands and hope.


But the landing burn only needs two engines. So if they had only known that it would be risky to ignite engine number two, SN11 might have landed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 04/05/2021 08:59 pm
I freaking love the GSE tanks. 

How cheap is this for SpaceX versus commercial tanks. 

Let's get the rest headed for the pad not too!

Love it.
It's awesome that the GSE tanks can be manufactured on the same production line that builds the spacecraft. Talk about economy!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: vessmech on 04/05/2021 09:15 pm
Does anyone know if these GSE tanks are designed/built/inspected to ASME Boiler Code?  I dont think Texas mandates ASME Code stamps for pressure vessels but there are insurance and other implications in building non Code pressure vessels.  Just curious if anyone saw pictures that showed any kind of name plate with design conditions on these storage vessels.  Thanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MTom on 04/05/2021 09:23 pm
Does anyone know if these GSE tanks are designed/built/inspected to ASME Boiler Code?  I dont think Texas mandates ASME Code stamps for pressure vessels but there are insurance and other implications in building non Code pressure vessels.  Just curious if anyone saw pictures that showed any kind of name plate with design conditions on these storage vessels.  Thanks.

Welcome to the forum!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/05/2021 09:23 pm
Does anyone know if these GSE tanks are designed/built/inspected to ASME Boiler Code?  I dont think Texas mandates ASME Code stamps for pressure vessels but there are insurance and other implications in building non Code pressure vessels.  Just curious if anyone saw pictures that showed any kind of name plate with design conditions on these storage vessels.  Thanks.

Great point on the pressure vessel cert/stamp.  It's not flying hardware so using thicker material for a larger safety margin are minimal impact. 

It will be interesting to see how they insulate them once they are secured at the pad.  I imagine pressure testing and some hook ups first then insulation.

Better GSE could really help the testing and flights too.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: waveney on 04/05/2021 09:26 pm
I was thinking something more subtle like an overheated transistor, which was then unable to source full current to open a solenoid when commanded.  Unlike a blitzed sensor or a missing heartbeat, heat damage of that kind might be difficult (but not impossible) to detect before the electronics in question are called on to perform.  Could be addressed by additional health sensors, or by changing procedures to allow a safe abort if the solenoid fails when commanded, etc.
Yeah, likely one component or sensor on one board was fried, and there was either no (or a useless) monitoring circuit for that particular failure mode, or the detection circuit wasn't being utilized properly.

So by my count there are at least 6 fixes:

1) keep methane plumbing from leaking (likely addressed with cleaner plumbing on SN15+ raptors)
2) if methane plumbing is leaking (big pressure drop in one section), shut off the engine unless absolutely needed
3) add more heat shielding/insulation to keep the failed part(s) from getting fried if exposed to flames
4) if raptor electronics are sitting in a literal flamethrower, turn off the engine
5) add monitoring circuit(s) to test if component/sensor has failed
6) if monitoring circuit indicates failure, don't attempt to start engine unless absolutely needed

Also, now that they have seen in practice what a methane flamethrower can do, and with a high severity outcome, they'll examine every potential leak location in the system (flamethrower source), and every exposed location (flamethrower sink), and address/mitigate as appropriate. Wouldn't be surprised if this results in dozens of changes.

In the end, SN11 resulted in great data, failing differently than past tests. And even if SN11 had flown perfectly, a second flight might have surfaced the leak and avionics issues, so I maintain that testing SN* until failure is the best use for these test articles.

I agree with points 1,6,3   

Points 3,4: During sn10 launch the first attempt was aborted at t=-0.1 s because of higher than specification thrust from an engine. So I think they already have a conservative limits, and severe controls over the engine status. But I have no information to support that.

To use Starship for large numbers of people in the  future, it needs to demonstrate a lot of fault resilience.  Faults happen what ever you do, you can engineer round lots of them, but there will always be another.   A resilient system can tolerate faults,, many faults and still struggle on and try its best to provide some service.

Part of fault resilience is fault containment, stopping faults getting lose and wrecking other things.

Part of fault resilience is taking a high enough level view, and killing what may be totally viable parts of the system, if it protects a much larger or important part of the system.

I have written two such system critical bits of software that take that high enough view to protect telecoms networks from unfortunate combinations of what are apparently minor faults.  If a particular component failed in one unlikely (but possible) way it would appear to be an unrelated fault in a different box, get two of those and the entire exchange dies, spot that combination at the high level, kill those two boxes (even though they only failed on one side of a duplicated system), everything else then survives.

I hope Space X has enough people like me with a high level nose for trouble looking out for ways to contain failures and prepared to write killer code they hope is never used.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/05/2021 09:35 pm


I am anxiously awaiting the day the "Musk's Used Spaceships/For Sale CHEAP" sign goes up. I might be tempted to raid my 401K.
save a few bocks for transporting the device

This is, of course, how Delos D Harriman eventually finagled his way to Luna in RAH's 'Rocketship Galileo'! All that's needed on top is a spacesuit, and he will travel that glory road!

While I appreciate the multiple RAH references, D. D. Harriman's death was a tragedy. Having spent his life creating all the technology and business needed to make Luna humanities second home, he was never allowed to leave Earth by insurance, business and later family members hounding him. He had to runaway, find some shady guys to front buying a used ship from literally himself and then be shipped as cargo. He has to sneak onto the Moon he essentially owned and died in the attempt. I can not imagine a more cursed demise that could befall a man.
Despite all obstacles, he built the hardware and business case for the moon. Against all odds he finally got there himself. The sadness is in us, not D.D.
He was satisfied.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/05/2021 09:36 pm
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

Another old adage is "never check for an error condition you don't know how to handle". Adding health checks adds complexity, and from EMs "we were too dumb" comment, they clearly had been leaning strongly toward software simplicity for this phase of the test program.
For launch, you should ofc be leaning towards caution, but for the do-or-die landing burn? Nah, send the commands and hope.


But the landing burn only needs two engines. So if they had only known that it would be risky to ignite engine number two, SN11 might have landed.

The timing of the avionics being fried probably had everything to do with it.  It seems unlikely that it got fried on the way up, or else we'd have seen the engine fail to shut down before the descent.  This means that the damage had to have happened sometime *during* engine restart.  This means that somewhere in the middle of the complicated startup sequence, the controls just stopped, and bad things happened.

The obvious solution to this is to have redundant avionics boxes, so if one fails, the other can take over, but in reality, this is a lot more complicated to implement than it would seem.  Each avionics system will never be in complete agreement over the state of the engine (and if you don't believe me, think about what happens for any sensor that has an analog output).  Unless you have a single ADC to convert it to a digital signal for both avionics systems (single point of failure!), they will each read a slightly different value due to hardware not being perfect, and when it so happens that the sensor passes a point telling the avionics that it needs to do something like adjust a value, they won't be in agreement for an instant.  At that point, you have a conflicting control signal, and then one of the avionics systems will get confused when it sees sensor readings change unexpectedly when it didn't send a command to do anything.

All that can of course be dealt with in hardware and software, but it unavoidably adds complexity, something quite undesirable when your hardware and software are in flux as you make revisions and adjustments with data from every new flight.  It becomes just another part that has to be changed, and another location for bugs to creep in.  Later on, after the engines and flight profile are well characterized and things settle down, you can think of dealing with redundancy, but in the meanwhile, it may do more harm than good in that it bogs things down.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: IANARS on 04/05/2021 09:45 pm
Posted reply in launch sites thread:

Cross posting from the prototypes thread:

Does anyone know if these GSE tanks are designed/built/inspected to ASME Boiler Code?  I dont think Texas mandates ASME Code stamps for pressure vessels but there are insurance and other implications in building non Code pressure vessels.  Just curious if anyone saw pictures that showed any kind of name plate with design conditions on these storage vessels.  Thanks.

Great point on the pressure vessel cert/stamp.  It's not flying hardware so using thicker material for a larger safety margin are minimal impact. 

It will be interesting to see how they insulate them once they are secured at the pad.  I imagine pressure testing and some hook ups first then insulation.

Better GSE could really help the testing and flights too.

So a quick look at Texas Boiler Law appears to require adherence to ASME Section VIII, Division 1, however ASME also excludes pressure vessels with design pressure below 15 psig from requiring certification. This is commonly used in my industry (Oil & Gas) to negate the requirement to certify some vessels/fabricated components.

I’d defer to some of the guys who are experienced in storing cryo rocket propellants as to whether that low a design pressure is common, however.

Thanks
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/05/2021 09:56 pm
I was thinking something more subtle like an overheated transistor, which was then unable to source full current to open a solenoid when commanded.  Unlike a blitzed sensor or a missing heartbeat, heat damage of that kind might be difficult (but not impossible) to detect before the electronics in question are called on to perform.  Could be addressed by additional health sensors, or by changing procedures to allow a safe abort if the solenoid fails when commanded, etc.
Yeah, likely one component or sensor on one board was fried, and there was either no (or a useless) monitoring circuit for that particular failure mode, or the detection circuit wasn't being utilized properly.

So by my count there are at least 6 fixes:

1) keep methane plumbing from leaking (likely addressed with cleaner plumbing on SN15+ raptors)
2) if methane plumbing is leaking (big pressure drop in one section), shut off the engine unless absolutely needed
3) add more heat shielding/insulation to keep the failed part(s) from getting fried if exposed to flames
4) if raptor electronics are sitting in a literal flamethrower, turn off the engine
5) add monitoring circuit(s) to test if component/sensor has failed
6) if monitoring circuit indicates failure, don't attempt to start engine unless absolutely needed

Also, now that they have seen in practice what a methane flamethrower can do, and with a high severity outcome, they'll examine every potential leak location in the system (flamethrower source), and every exposed location (flamethrower sink), and address/mitigate as appropriate. Wouldn't be surprised if this results in dozens of changes.

In the end, SN11 resulted in great data, failing differently than past tests. And even if SN11 had flown perfectly, a second flight might have surfaced the leak and avionics issues, so I maintain that testing SN* until failure is the best use for these test articles.

I agree with points 1,6,3   

Points 3,4: During sn10 launch the first attempt was aborted at t=-0.1 s because of higher than specification thrust from an engine. So I think they already have a conservative limits, and severe controls over the engine status. But I have no information to support that.

To use Starship for large numbers of people in the  future, it needs to demonstrate a lot of fault resilience.  Faults happen what ever you do, you can engineer round lots of them, but there will always be another.   A resilient system can tolerate faults,, many faults and still struggle on and try its best to provide some service.

Part of fault resilience is fault containment, stopping faults getting lose and wrecking other things.

Part of fault resilience is taking a high enough level view, and killing what may be totally viable parts of the system, if it protects a much larger or important part of the system.

I have written two such system critical bits of software that take that high enough view to protect telecoms networks from unfortunate combinations of what are apparently minor faults.  If a particular component failed in one unlikely (but possible) way it would appear to be an unrelated fault in a different box, get two of those and the entire exchange dies, spot that combination at the high level, kill those two boxes (even though they only failed on one side of a duplicated system), everything else then survives.

I hope Space X has enough people like me with a high level nose for trouble looking out for ways to contain failures and prepared to write killer code they hope is never used.

The issue here is that we're talking about software in active development.  Imagine that when you were working with those boxes, you knew that the system was still changing and evolving, with new versions rolling out every week, some of which may be major departures from the previous versions.  Does that sound like something that would have made your job a nightmare?

But this is where SpaceX is right now.  They're getting new information with every flight, and constantly discovering new problems.  You can view it as the requirements being revised with every test, and the code running on these systems is prototype code.

Later on, when the design has reached stable beta version 0.1 so to speak, it will be time to really focus on resiliency.  But maybe not while we're still in alpha.

In the meanwhile, what they need are programmers who understand enough about how code is made resilient that they can keep this in the back of their minds as they code, so that things stay well organized and adhere to basic API rules so that there aren't any nasty surprises.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: envy887 on 04/05/2021 10:29 pm
I wonder how they will go about avoiding a similar mishap in the future?

Preventing the leak, and thus the fire itself... of course.   
Better packaging & sealing of the sensitive circuitry... of course.
Both of these vulnerabilities would only exist in a rapid-development environment, not production specs.

Better health monitoring of the avionics?... possible. Likely, even, once they have a stable Raptor design and stop fiddling with them!

But... HOW can they protect against an engine RUD, as in this case a hard-start of the methane preburner, from propagating up into the plumbing and header tank? I would think that would require a *big* plumbing redesign? It's not as if you can just put some blast shielding in there, the way you can put between engines to protect them from each other.

Early experimenters with monopropellants learned how to do this to keep a engine detonation on the test stand from propagating back to propellant storage tanks. One thing you can do is a tight 360 degree bend so the pipe runs past itself. When the detonation tries to run around the bend, it cuts the plumbing before it has a chance to propagate through.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ulm_atms on 04/05/2021 10:53 pm
I was thinking something more subtle like an overheated transistor, which was then unable to source full current to open a solenoid when commanded.  Unlike a blitzed sensor or a missing heartbeat, heat damage of that kind might be difficult (but not impossible) to detect before the electronics in question are called on to perform.  Could be addressed by additional health sensors, or by changing procedures to allow a safe abort if the solenoid fails when commanded, etc.
Yeah, likely one component or sensor on one board was fried, and there was either no (or a useless) monitoring circuit for that particular failure mode, or the detection circuit wasn't being utilized properly.

So by my count there are at least 6 fixes:

1) keep methane plumbing from leaking (likely addressed with cleaner plumbing on SN15+ raptors)
2) if methane plumbing is leaking (big pressure drop in one section), shut off the engine unless absolutely needed
3) add more heat shielding/insulation to keep the failed part(s) from getting fried if exposed to flames
4) if raptor electronics are sitting in a literal flamethrower, turn off the engine
5) add monitoring circuit(s) to test if component/sensor has failed
6) if monitoring circuit indicates failure, don't attempt to start engine unless absolutely needed

Also, now that they have seen in practice what a methane flamethrower can do, and with a high severity outcome, they'll examine every potential leak location in the system (flamethrower source), and every exposed location (flamethrower sink), and address/mitigate as appropriate. Wouldn't be surprised if this results in dozens of changes.

In the end, SN11 resulted in great data, failing differently than past tests. And even if SN11 had flown perfectly, a second flight might have surfaced the leak and avionics issues, so I maintain that testing SN* until failure is the best use for these test articles.

I agree with points 1,6,3   

Points 3,4: During sn10 launch the first attempt was aborted at t=-0.1 s because of higher than specification thrust from an engine. So I think they already have a conservative limits, and severe controls over the engine status. But I have no information to support that.

To use Starship for large numbers of people in the  future, it needs to demonstrate a lot of fault resilience.  Faults happen what ever you do, you can engineer round lots of them, but there will always be another.   A resilient system can tolerate faults,, many faults and still struggle on and try its best to provide some service.

Part of fault resilience is fault containment, stopping faults getting lose and wrecking other things.

Part of fault resilience is taking a high enough level view, and killing what may be totally viable parts of the system, if it protects a much larger or important part of the system.

I have written two such system critical bits of software that take that high enough view to protect telecoms networks from unfortunate combinations of what are apparently minor faults.  If a particular component failed in one unlikely (but possible) way it would appear to be an unrelated fault in a different box, get two of those and the entire exchange dies, spot that combination at the high level, kill those two boxes (even though they only failed on one side of a duplicated system), everything else then survives.

I hope Space X has enough people like me with a high level nose for trouble looking out for ways to contain failures and prepared to write killer code they hope is never used.

The issue here is that we're talking about software in active development.  Imagine that when you were working with those boxes, you knew that the system was still changing and evolving, with new versions rolling out every week, some of which may be major departures from the previous versions.  Does that sound like something that would have made your job a nightmare?

But this is where SpaceX is right now.  They're getting new information with every flight, and constantly discovering new problems.  You can view it as the requirements being revised with every test, and the code running on these systems is prototype code.

Later on, when the design has reached stable beta version 0.1 so to speak, it will be time to really focus on resiliency.  But maybe not while we're still in alpha.

In the meanwhile, what they need are programmers who understand enough about how code is made resilient that they can keep this in the back of their minds as they code, so that things stay well organized and adhere to basic API rules so that there aren't any nasty surprises.

This whole convo is a good example of Agile development being a double edge sword.  Sure it's quick but like everything...their are cons too.

They really have to nail down Raptor design before they can start rounding up and dealing with failure modes/issues in a more complete way.  And from the looks of it by the massive changes in Raptor for SN15....they are still taking big swings at it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/05/2021 11:10 pm
I'm far from being an expert in explosions and the audio was far from being studio quality. The sharp crack tells me that it was relatively small, and probably high explosives. Admittedly while being in ignorance of what might come of different engine RUD scenarios. There was no double tap that would indicate an engine blowing and taking out a tank.

Have you listened to this recording (at 3:28):

https://youtu.be/l4eawtvznbc?t=208 (https://youtu.be/l4eawtvznbc?t=208)

That does sound like a double tap to me (if we are talking about the same thing). On other recordings I couldn't hear it (some far away, some peaking, ...). This recording is close and has studio quality.
Thank you for finding that. At 3:23 there was a crack-crack. Not very loud but qualitatively like the crack I was talking about with ~500ms delay between cracks. Maybe an echo. This can change with where the mic is. Not sure what it really was.


At 3:28 the big boom started. The five second gap is way longer than what I heard earlier. There seemed to be a transient at the front end with what I'd take to be something similar to the crack but it seemed to be tighter to the boom than what I heard in other vids.


The boom itself did not seem concussive. Loud and rumbling, but not a shock wave. Very close lightning is a good proxy. The boom is heart stoppingly sudden. Everything else is echos. This boom seemed to me to be consistent with an unzipped tin can ripping itself apart in a high wind while the residuals do the conflagration thing. But then, it could be the best audio in the world and I'm listening to it on a phone. DuH!


I was comfortable with my analysis until I heard this. Now I'm not so sure. Are you from the Trilateral Commission (or the Galactic Confederation) sewing dissent, confusion and alternate truths?  :o

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/05/2021 11:24 pm
I wonder if all the fixes for the SN11 failure are already part of the SN15 design, or if they will need to “retrofit” as Musk said.


Not necessarily (though likely)...it could have been a small leak on the main plumbing going to the Raptor

It sounds like the leak was on the Raptor itself, not the SN11, so...
For me sounds like the leak was on the raptor, because the fire was on the raptor. So, strangely the theory I was supporting somewath was true. The explosion then arrived to the CH4 header via the downcomer. Could be possible that an hard start in CH4 turbopomp created a "shockwave" in the plumbing that then caused a rupture in a weak poin in the CH4 header? Maybe I'm wrong thinking that the explosion started in fuel header tank, is the separation betweeen the two halves of it  a sufficient proof of that?
You might be onto something. A shockwave from a destroyed turbopump traveling up the manifold, into the downcomer and up to the header. This might explain the top of the methane header going its own way.


OTOH, There's a lot of direction changes in the manifold. Hard to picture a shock following this without blowing a joint off at a bend.


The more I know, the less I understand. I'll get over it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/05/2021 11:54 pm
I freaking love the GSE tanks. 

How cheap is this for SpaceX versus commercial tanks. 

Let's get the rest headed for the pad not too!

Love it.
It's awesome that the GSE tanks can be manufactured on the same production line that builds the spacecraft. Talk about economy!
Ah, well, when you get right down to it, SS  is a big cryo tank with extra bits. They already have the materials, tooling and expertise, so why not?


Gotta love it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/06/2021 12:26 am
Hi, long time lurker, first time posting. Please forgive long first post. 
Been following Musk since his early Tesla days,  as I enjoy studying new engineering designs.  

From what I see, Musk is the ultimate engineering sandbagger.    He is the guy who shows up at the races with a little rusted import car, acting stupid, with 1000 HP crammed under the hood. Looking to race people for money. 

 Smart man does it on purpose so competitors foolishly underestimate him.     I'm enjoying the super quick progression of Musk giving speeches standing in front of rusty water tanks few thought could ever fly, to hopper, to what now looks like the beginnings of a real spaceship. 

 I bet SN15 is a test bed closer to hopper, than what will actually land on the moon and then Mars in a few years time.    The moon/mars design they are likely currently working on. 

Known SN11 landing/raptor issues likely sorted out a long time ago with scrapping of sn12-13-14, and sn15's new raptors/plumbing redesign.  But they already had sn11 built, so may as well risk some fireworks.  As in business, even failure is an advantage, when it makes competitors foolishly underestimate you.     Sandbaggers will often lose races on purpose. Until real money is on the line.  Then they win every time. 

 Vertical landing SN15-SN20+ will be perfect for shaking out final raptor throttling design, and getting satellites into orbit, making some profit.  I bet they will be nailing most landings by then. 

But the real designs, we haven't seen yet, as Musk likes to keep cards close to chest. To surprise and wow people at the last minute.  Much wow... like starman listening to tunes sitting in a Tesla on his way to Mars, while two boosters casually land back on earth.  Or shocking wow like cybertruck.  That is his advertising strategy.  Wow factor.  It works.   Richest dude on the planet. 

What I enjoy most of Musks engineering, is he never overcomplicates things.  True believer in kiss (keep it simple stupid).   So simple even welders in the back yard can build it.  No clean room needed. 

I bet the mars starship will be a huge leap from sn20.  But still a relatively simple elegant design.   That is the one I am really looking forward to. 

 From an engineering standpoint, I bet it lands horizontally.    As it's the only lightweight uncomplicated design that makes sense for getting real tonnage to Mars. 

  It will likely have a fraptor (front raptor, or two)  hidden tucked between the forward fins.  Couple of rear raptors will gimbal down 90 degrees.   It will come in on heat shield side till it slows down enough to do a gentle 180 roll, then 3 or 4 raptors light and gently land it anywhere with serious tonnage. 

  Landing gear will be incorporated with fins.    The giant gigapress made section of frame where fins/landing gear and raptor mount, will also be hinge for giant forward ramp door.  Which opens downward. and we will see tesla mars semi rolling down the ramp with sections of Mars station one.  This is when we know we are finally in the future.  :)

To me, this is the simplest to manufacture way (and coolest way)  to get large cargo to the surface of Moon and Mars safely.   Plus the 3/4 raptors can gimbal and slightly angle debris away from the ship on initial takeoff.  As very fragile heat shield will be at the top of the ship.    Looking forward to fireworks from exciting heatshield testing coming soon. 

My guess,  first they have to get the raptor throttling design down as simple as possible, and this is what we are currently witnessing with vertical landings, before they do horizontal landing.  

They are so freaking close, even on first try with sn8, which is amazing.  At current rate,  I expect to see invasion of Tesla semis rolling on mars within 10 years. 

Enjoying the show, commentary, awesome photos, videos and updates! 

Frank
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/06/2021 12:49 am
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

Another old adage is "never check for an error condition you don't know how to handle". Adding health checks adds complexity, and from EMs "we were too dumb" comment, they clearly had been leaning strongly toward software simplicity for this phase of the test program.
For launch, you should ofc be leaning towards caution, but for the do-or-die landing burn? Nah, send the commands and hope.


But the landing burn only needs two engines. So if they had only known that it would be risky to ignite engine number two, SN11 might have landed.

The timing of the avionics being fried probably had everything to do with it.  It seems unlikely that it got fried on the way up, or else we'd have seen the engine fail to shut down before the descent.  This means that the damage had to have happened sometime *during* engine restart.  This means that somewhere in the middle of the complicated startup sequence, the controls just stopped, and bad things happened.

The obvious solution to this is to have redundant avionics boxes, so if one fails, the other can take over, but in reality, this is a lot more complicated to implement than it would seem.  Each avionics system will never be in complete agreement over the state of the engine (and if you don't believe me, think about what happens for any sensor that has an analog output).  Unless you have a single ADC to convert it to a digital signal for both avionics systems (single point of failure!), they will each read a slightly different value due to hardware not being perfect, and when it so happens that the sensor passes a point telling the avionics that it needs to do something like adjust a value, they won't be in agreement for an instant.  At that point, you have a conflicting control signal, and then one of the avionics systems will get confused when it sees sensor readings change unexpectedly when it didn't send a command to do anything.

All that can of course be dealt with in hardware and software, but it unavoidably adds complexity, something quite undesirable when your hardware and software are in flux as you make revisions and adjustments with data from every new flight.  It becomes just another part that has to be changed, and another location for bugs to creep in.  Later on, after the engines and flight profile are well characterized and things settle down, you can think of dealing with redundancy, but in the meanwhile, it may do more harm than good in that it bogs things down.
If they do the controllers the same as F9, they have triple redundancy. If one computer is in disagreement (most certainly a range, not a hard value) the two in agreement take over and the odd computer out reboots and resyncs. Probably not enough time for the whole process but enough for a poll to show the bad one to cut out.


Divergence in the A-D converters can be mapped and compensated for if it's large enough (you get what you pay for) but it's doubtful the mapping would extend to fire conditions.


Guessing: I'd say most of the sensors feed a single channel signal conditioner which in turn would feed into a GPIB bus or the modern equivalent for distribution to all three controllers. The sensor redundancy would come from having multiples whenever possible. Doesn't help if a fire heats the wires and changes resistance in those sensors depending on voltage, amperage or resistance. Pulse would probably be ok.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/06/2021 12:52 am
Hi, long time lurker, first time posting. Please forgive long first post.
Been following Musk since his early Tesla days,  as I enjoy studying new engineering designs.

Welcome to de-lurkerhood!!!  Enjoyed reading your thoughts.

Don't really agree that horizontal landing makes any sense whatsoever, much less that it's the lightest weight solution.  That seems to have been pretty thoroughly discussed and dismissed.  It's hard to hand-wave around all the massive engineering challenges to thrust-structures, Raptors in the people places, and 90 degree rotating rear Raptors.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: yg1968 on 04/06/2021 01:03 am
Here is an explanation of Elon't tweet that I actually understood:

https://twitter.com/WatchersTank/status/1379042604625584128
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 04/06/2021 01:09 am
Here is an explanation of Elon't tweet that I actually understood:

https://twitter.com/WatchersTank/status/1379042604625584128

This is a slightly errant definition of a "hard start." A Hard Start in a rocket engine is an overpressure condition inside of it -- an explosion -- when they're trying to start the engine.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dfp21 on 04/06/2021 03:06 am
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

Another old adage is "never check for an error condition you don't know how to handle". Adding health checks adds complexity, and from EMs "we were too dumb" comment, they clearly had been leaning strongly toward software simplicity for this phase of the test program.
For launch, you should ofc be leaning towards caution, but for the do-or-die landing burn? Nah, send the commands and hope.


But the landing burn only needs two engines. So if they had only known that it would be risky to ignite engine number two, SN11 might have landed.

The timing of the avionics being fried probably had everything to do with it.  It seems unlikely that it got fried on the way up, or else we'd have seen the engine fail to shut down before the descent.  This means that the damage had to have happened sometime *during* engine restart.  This means that somewhere in the middle of the complicated startup sequence, the controls just stopped, and bad things happened.

The obvious solution to this is to have redundant avionics boxes, so if one fails, the other can take over, but in reality, this is a lot more complicated to implement than it would seem.  Each avionics system will never be in complete agreement over the state of the engine (and if you don't believe me, think about what happens for any sensor that has an analog output).  Unless you have a single ADC to convert it to a digital signal for both avionics systems (single point of failure!), they will each read a slightly different value due to hardware not being perfect, and when it so happens that the sensor passes a point telling the avionics that it needs to do something like adjust a value, they won't be in agreement for an instant.  At that point, you have a conflicting control signal, and then one of the avionics systems will get confused when it sees sensor readings change unexpectedly when it didn't send a command to do anything.

All that can of course be dealt with in hardware and software, but it unavoidably adds complexity, something quite undesirable when your hardware and software are in flux as you make revisions and adjustments with data from every new flight.  It becomes just another part that has to be changed, and another location for bugs to creep in.  Later on, after the engines and flight profile are well characterized and things settle down, you can think of dealing with redundancy, but in the meanwhile, it may do more harm than good in that it bogs things down.
In the video I observe orange exhaust from the faulty raptor during the ascent, and blue/pink exhaust from the other 2 raptors. I'm guessing this is evidence of a serious internal leak, damaging/fouling  things during the ascent. Whatever bad happened, it started during the ascent.

Good riddance this version of raptors. Next version needs to be better instrumented and some external component should shut off fuel from any raptor that doesn't report health. (That's my advice, coming from the peanut gallery)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/06/2021 03:51 am
Here is an explanation of Elon't tweet that I actually understood:

https://twitter.com/WatchersTank/status/1379042604625584128

Absolutely wrong, that audio from the oficial stream is FALLING DEBRIS ONLY, the pad audio was openned to the stream late, after the explosion, as John Insprucker were still speaking when it happened. There is no audio from the rocket itself, as stated by the lady who runs the stream on her twitter, "ground assets only", the microphones are a couple shotgun mics inside windshields, one is located on the pad itself at a concrete box, the other mic is placed on top of a container under the new metal roof that may or may not be a restroom, close to where Zeus used to live.

Anyway, you can't hear engine start nor explosion on SpaceX oficial live stream. It's an unfounded comparision.

Btw, there's no way to have a mic under the engine skirt, it would be obliterated.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/06/2021 06:18 am
Hi, long time lurker, first time posting. Please forgive long first post.
Been following Musk since his early Tesla days,  as I enjoy studying new engineering designs.

Welcome to de-lurkerhood!!!  Enjoyed reading your thoughts.

Don't really agree that horizontal landing makes any sense whatsoever, much less that it's the lightest weight solution.  That seems to have been pretty thoroughly discussed and dismissed.  It's hard to hand-wave around all the massive engineering challenges to thrust-structures, Raptors in the people places, and 90 degree rotating rear Raptors.

Out of curiosity, love to see where forward raptors were discussed, if you could kindly point me to those threads or sections.  I missed those. Only saw parachute, airbag talk, and early flip talk.

I'm no rocket scientist, so can definitely be wrong.   But seems to me, adding one or two forward raptors would be much lighter that the huge very heavy landing gear that would be needed to land vertically on Mars and hang serious tonnage off the side of a very tall starship, and winch it down to surface.   

    Then there would be even bigger problem of heat shielding the huge landing gear.  Not to mention, damaging aft heat shields on mars landings and take offs.     Seems to me, even if you needed 4 dedicated landing raptors, if gimbling rear raptors 90 is unfeasible.  Still a lighter simpler safer solution.  Raptors don't weigh much.   But I could be wrong. 

I envision the mars starship being much bigger than current prototypes, as current prototypes don't need to be huge to sort out raptor design.   Once raptor is sorted, for mars, why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel.   But lot more capacity.   

  Moving crew compartments more forward, lengthening nose, so easy when working with steel. 

Elon moves fast,  thinks big, and likes to surprise.  So I expect some massive mars cruise liners one day.   Hopefully, I live long enough to see it. Would be cool.  You want it to be massive, as you are stuck on board for a long while.

The current tiny landing gear design looks perfect for just getting stuff to orbit, and returning ship to landing pad.

I'm just thinking out loud what surprises might be next.  Loved the no landing gear booster surprise.  Catching it on fins will be epic!  Can't wait to see those first tries!

 Perhaps the mars version of starship will be a monster launched on two or three boosters. That would be truly epic, yet a very doable surprise.   

I would book that cruise.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/06/2021 06:41 am
I'll wager that one of the fixes is improved health monitoring for the avionics box.  As Elon said, that raptor wasn't strictly needed; if the avionics knew the box was fried it could have simply skipped restart on that engine and landing would have been norminal (or found another different way to fail).

I would hope, as part of Software Safety, that there is a continual heartbeat through the avionics.  A fried box would not produce a heartbeat.  So I am surprised that fried avionics would be able to send bad commands.

Another old adage is "never check for an error condition you don't know how to handle". Adding health checks adds complexity, and from EMs "we were too dumb" comment, they clearly had been leaning strongly toward software simplicity for this phase of the test program.
For launch, you should ofc be leaning towards caution, but for the do-or-die landing burn? Nah, send the commands and hope.


But the landing burn only needs two engines. So if they had only known that it would be risky to ignite engine number two, SN11 might have landed.

The timing of the avionics being fried probably had everything to do with it.  It seems unlikely that it got fried on the way up, or else we'd have seen the engine fail to shut down before the descent.  This means that the damage had to have happened sometime *during* engine restart.  This means that somewhere in the middle of the complicated startup sequence, the controls just stopped, and bad things happened.

The obvious solution to this is to have redundant avionics boxes, so if one fails, the other can take over, but in reality, this is a lot more complicated to implement than it would seem.  Each avionics system will never be in complete agreement over the state of the engine (and if you don't believe me, think about what happens for any sensor that has an analog output).  Unless you have a single ADC to convert it to a digital signal for both avionics systems (single point of failure!), they will each read a slightly different value due to hardware not being perfect, and when it so happens that the sensor passes a point telling the avionics that it needs to do something like adjust a value, they won't be in agreement for an instant.  At that point, you have a conflicting control signal, and then one of the avionics systems will get confused when it sees sensor readings change unexpectedly when it didn't send a command to do anything.

All that can of course be dealt with in hardware and software, but it unavoidably adds complexity, something quite undesirable when your hardware and software are in flux as you make revisions and adjustments with data from every new flight.  It becomes just another part that has to be changed, and another location for bugs to creep in.  Later on, after the engines and flight profile are well characterized and things settle down, you can think of dealing with redundancy, but in the meanwhile, it may do more harm than good in that it bogs things down.
In the video I observe orange exhaust from the faulty raptor during the ascent, and blue/pink exhaust from the other 2 raptors. I'm guessing this is evidence of a serious internal leak, damaging/fouling  things during the ascent. Whatever bad happened, it started during the ascent.

Good riddance this version of raptors. Next version needs to be better instrumented and some external component should shut off fuel from any raptor that doesn't report health. (That's my advice, coming from the peanut gallery)

Could be possible that the different color exhaust is sign of a failure. But has been also suggested(IIRC on the 19 thread) that running a raptor more fuel rich (which makes the flame more orange) could be a way of throttling it, even if lowers the efficiency. Maybe they noticed issues and were running the engine fuel rich to avoid to create an O2 rich environment.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SkyRate on 04/06/2021 10:49 am
I wonder if the new big antenna on SN15 is simply the airplane version of a Starlink dish. Has anyone estimated the diameter?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/06/2021 11:10 am
I wonder if the new big antenna on SN15 is simply the airplane version of a Starlink dish. Has anyone estimated the diameter?

Why should they place a starlink antenna on sn15*? Near stargate they have two big dish antennas, maybe they added a bigger antenna because they might want to transmit with more reliability or something so. With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve thad.

* while I was writing I thought about a possible answer. Maybe with starlink they wold have a redundant telemetry? But is unprobable, because the old antenna that we saw on sn8-11 there aren't on sn15.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 04/06/2021 11:16 am
With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve that.

TM has no problem penetrating clouds (fog).  Don't know why they had the dropouts they did (vehicle orientation during the descent?), but it wasn't the fog.

Have a good one,
Mike
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pete on 04/06/2021 11:32 am
With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve that.

TM has no problem penetrating clouds (fog).  Don't know why they had the dropouts they did (vehicle orientation during the descent?), but it wasn't the fog.

Have a good one,
Mike

They did *very* recently adopt a new, fancy encryption of their telemetry streams. Maybe the chosen format is more vulnerable to tiny errors?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/06/2021 11:37 am
With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve that.

TM has no problem penetrating clouds (fog).  Don't know why they had the dropouts they did (vehicle orientation during the descent?), but it wasn't the fog.

Have a good one,
Mike
Condensation/humidity causing issues on that day? Lots of the indie photographers and live streamers were reporting extreme humidity. Assume that might have impacted the equipment on SN11.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: waveney on 04/06/2021 11:38 am
With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve that.

TM has no problem penetrating clouds (fog).  Don't know why they had the dropouts they did (vehicle orientation during the descent?), but it wasn't the fog.

Have a good one,
Mike

They did *very* recently adopt a new, fancy encryption of their telemetry streams. Maybe the chosen format is more vulnerable to tiny errors?

If you encrypt before applying error correction, you are generally safe from transmission errors.

If you try and encrypt the stream after error correction you MAY be very vulnerable, depending on the type of encryption.

As was shown in the recent data case, it has well defined frames with encoded content - SpaceX know what they are doing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SkyRate on 04/06/2021 12:00 pm
I wonder if the new big antenna on SN15 is simply the airplane version of a Starlink dish. Has anyone estimated the diameter?

Why should they place a starlink antenna on sn15*? Near stargate they have two big dish antennas, maybe they added a bigger antenna because they might want to transmit with more reliability or something so. With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve thad.

* while I was writing I thought about a possible answer. Maybe with starlink they wold have a redundant telemetry? But is unprobable, because the old antenna that we saw on sn8-11 there aren't on sn15.
I see at least four small patch antennas on this side of SN15, which I assume are the same 2 GPS + 2 telemetry as before, with a duplicate set on the opposite side.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/06/2021 12:11 pm
With sn11 they had problem with the downlike due to fog, maybe a a more powerful antenna will solve that.

TM has no problem penetrating clouds (fog).  Don't know why they had the dropouts they did (vehicle orientation during the descent?), but it wasn't the fog.

Have a good one,
Mike

They did *very* recently adopt a new, fancy encryption of their telemetry streams. Maybe the chosen format is more vulnerable to tiny errors?

If you encrypt before applying error correction, you are generally safe from transmission errors.

If you try and encrypt the stream after error correction you MAY be very vulnerable, depending on the type of encryption.

As was shown in the recent data case, it has well defined frames with encoded content - SpaceX know what they are doing.

In his video about the data from a f9 launch that was recived by some guy, that were able to see images fr the tanks, Sott Manly pointed out that maybe SPaceX F9 telemetry isn't encrypted, besides being easy to intercept, because of old agreement about ICBMs between the  world powers. The encrypted telemetry from SN 11 was during the static fire. Could be possible that during the hop, for the same reason, they can't encrypt data duting the hop?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 04/06/2021 12:32 pm
No, data encryption is common on TM data streams.  There are many things that SpaceX does that's cool and special, but data TM isn't one of them.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/06/2021 12:44 pm
https://twitter.com/13ericralph31/status/1379233656737161219

Quote
Just dawned on me that this is a much bigger deal than it might seem. For SpaceX to design and build its own custom bulk commodity storage tanks instead of buying what is arguably a fairly routine and cheap off-the-shelf technology, Starship production has to be DIRT CHEAP.

Here’s Eric’s write-up of that thought:

https://www.teslarati.com/spacex-starship-launch-pad-custom-storage-tanks/

Quote
SpaceX is building launch pad tanks out of Starship parts and that’s a big deal

By Eric Ralph
Posted on April 6, 2021

SpaceX has begun installing the first of numerous propellant storage tanks at its first orbital South Texas launch facilities – a mostly ordinary and expected step made extraordinary by the fact that those tanks will be built out of Starship parts.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/06/2021 01:42 pm
Hi, long time lurker, first time posting. Please forgive long first post.
Been following Musk since his early Tesla days,  as I enjoy studying new engineering designs.

Welcome to de-lurkerhood!!!  Enjoyed reading your thoughts.

Don't really agree that horizontal landing makes any sense whatsoever, much less that it's the lightest weight solution.  That seems to have been pretty thoroughly discussed and dismissed.  It's hard to hand-wave around all the massive engineering challenges to thrust-structures, Raptors in the people places, and 90 degree rotating rear Raptors.

Out of curiosity, love to see where forward raptors were discussed, if you could kindly point me to those threads or sections.  I missed those. Only saw parachute, airbag talk, and early flip talk.

I'm no rocket scientist, so can definitely be wrong.   But seems to me, adding one or two forward raptors would be much lighter that the huge very heavy landing gear that would be needed to land vertically on Mars and hang serious tonnage off the side of a very tall starship, and winch it down to surface.   

    Then there would be even bigger problem of heat shielding the huge landing gear.  Not to mention, damaging aft heat shields on mars landings and take offs.     Seems to me, even if you needed 4 dedicated landing raptors, if gimbling rear raptors 90 is unfeasible.  Still a lighter simpler safer solution.  Raptors don't weigh much.   But I could be wrong. 

I envision the mars starship being much bigger than current prototypes, as current prototypes don't need to be huge to sort out raptor design.   Once raptor is sorted, for mars, why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel.   But lot more capacity.   

  Moving crew compartments more forward, lengthening nose, so easy when working with steel. 

Elon moves fast,  thinks big, and likes to surprise.  So I expect some massive mars cruise liners one day.   Hopefully, I live long enough to see it. Would be cool.  You want it to be massive, as you are stuck on board for a long while.

The current tiny landing gear design looks perfect for just getting stuff to orbit, and returning ship to landing pad.

I'm just thinking out loud what surprises might be next.  Loved the no landing gear booster surprise.  Catching it on fins will be epic!  Can't wait to see those first tries!

 Perhaps the mars version of starship will be a monster launched on two or three boosters. That would be truly epic, yet a very doable surprise.   

I would book that cruise.

Welcome to the forum and I hope you have a very engaging time here. I’m no rocket scientist either and I have learnt a huge amount from some of the locals here some of whom have a wealth of knowledge and have worked with rocket technology.

Elon Musk is determined to send humans to Mars at the earliest opportunity and the current ship is sufficient for that need so I doubt there will be much emphasis on redesigning the ship for some time. Much as this might appeal from the cool angle.

“Why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel. But lot more capacity.” No doubt much larger ships are possible and will be built one day, but be under no illusion that words like “easy” or “simple” are appropriate. If you are building a plastic model it might be simple but if you are building a flying block of flats and you want to double or treble its volume it is no small thing. Especially if you still expect that flying block of flats to do a quick pirouette just before landing.

Starship was designed to land vertically and will not land horizontally. This has been confirmed by Elon Musk in a tweet and stands to reason from an engineering perspective. It is easy to think small scale and wonder at the possibilities (I have done just that myself) but be very wary of this thinking because the real thing is enormous and scaling can play havoc with calculations. A model Starship might be easily supported on its side or at any bizarre angle by gluing on legs, the real thing will not.

The entire mass of Starship of the first starship to land on Mars will have to be supported by legs whatever the orientation it lands in. From a structural point of view vertical is stronger. Starship tubular sections can easily support their own weight vertically, but would bow and wobble like a bowl of jelly if turned through 90 degrees.

The current legs are a quick, cheap and dirty solution only intended for early prototypes while they clarify which leg design would be best.

“Perhaps the mars version of starship will be a monster launched on two or three boosters. That would be truly epic, yet a very doable surprise.” It would be an epic surprise but not very doable. As many people here will tell you rockets aren’t lego. Going from Falcon 9 to Falcon Heavy caused a major headache for SpaceX, despite being “just” 3 boosters strapped together.   
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/06/2021 01:59 pm
Hi, long time lurker, first time posting. Please forgive long first post.
Been following Musk since his early Tesla days,  as I enjoy studying new engineering designs.

Welcome to de-lurkerhood!!!  Enjoyed reading your thoughts.

Don't really agree that horizontal landing makes any sense whatsoever, much less that it's the lightest weight solution.  That seems to have been pretty thoroughly discussed and dismissed.  It's hard to hand-wave around all the massive engineering challenges to thrust-structures, Raptors in the people places, and 90 degree rotating rear Raptors.

Out of curiosity, love to see where forward raptors were discussed, if you could kindly point me to those threads or sections.  I missed those. Only saw parachute, airbag talk, and early flip talk.

I'm no rocket scientist, so can definitely be wrong.   But seems to me, adding one or two forward raptors would be much lighter that the huge very heavy landing gear that would be needed to land vertically on Mars and hang serious tonnage off the side of a very tall starship, and winch it down to surface.   

    Then there would be even bigger problem of heat shielding the huge landing gear.  Not to mention, damaging aft heat shields on mars landings and take offs.     Seems to me, even if you needed 4 dedicated landing raptors, if gimbling rear raptors 90 is unfeasible.  Still a lighter simpler safer solution.  Raptors don't weigh much.   But I could be wrong. 

I envision the mars starship being much bigger than current prototypes, as current prototypes don't need to be huge to sort out raptor design.   Once raptor is sorted, for mars, why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel.   But lot more capacity.   

  Moving crew compartments more forward, lengthening nose, so easy when working with steel. 

Elon moves fast,  thinks big, and likes to surprise.  So I expect some massive mars cruise liners one day.   Hopefully, I live long enough to see it. Would be cool.  You want it to be massive, as you are stuck on board for a long while.

The current tiny landing gear design looks perfect for just getting stuff to orbit, and returning ship to landing pad.

I'm just thinking out loud what surprises might be next.  Loved the no landing gear booster surprise.  Catching it on fins will be epic!  Can't wait to see those first tries!

 Perhaps the mars version of starship will be a monster launched on two or three boosters. That would be truly epic, yet a very doable surprise.   

I would book that cruise.


“Why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel. But lot more capacity.” No doubt much larger ships are possible and will be built one day, but be under no illusion that words like “easy” or “simple” are appropriate. If you are building a plastic model it might be simple but if you are building a flying block of flats and you want to double or treble its volume it is no small thing. Especially if you still expect that flying block of flats to do a quick pirouette just before landing.
Agree. I add that a bigger ship will need more raptors, and they struggle to have 28 for a SuperHeavy, we are long before seeing bigger 12m or 15m or 18 m. It will happen, but not today, not tomorrow, nor in 5 years.
Quote

Starship was designed to land vertically and will not land horizontally. This has been confirmed by Elon Musk in a tweet and stands to reason from an engineering perspective. It is easy to think small scale and wonder at the possibilities (I have done just that myself) but be very wary of this thinking because the real thing is enormous and scaling can play havoc with calculations. A model Starship might be easily supported on its side or at any bizarre angle by gluing on legs, the real thing will not.

The entire mass of Starship of the first starship to land on Mars will have to be supported by legs whatever the orientation it lands in. From a structural point of view vertical is stronger. Starship tubular sections can easily support their own weight vertically, but would bow and wobble like a bowl of jelly if turned through 90 degrees.

Not speaking about how to slow down in that configuration and ro liftoff. Surely the answer is to put raptor on one side. That IMO is a terrible idea, because will generate a non simmetrical mass distribution (not a good thing when the ship will not be in orizontakl configuration, such during launch), because will add mass, because need more and more complicated plumbing and where can they fit these raptor on a side of the ship?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/06/2021 02:21 pm
I wonder if the new big antenna on SN15 is simply the airplane version of a Starlink dish. Has anyone estimated the diameter?

Someone posted a picture of Falcon 9 using the same "antenna"(in this thread iirc) so it's probably not a "Starlink dish".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kevin9 on 04/06/2021 03:05 pm
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/06/2021 03:51 pm
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/06/2021 03:56 pm
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.

Exactly. If anything, 2 engines are better for the flip. 2 engines= offset thrust which=a quicker flip, however 3 works best for now to help with redundancy.

IMO, landing burns should be 2 engines all the way down, but the third engine is on standby in the event of one failing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/06/2021 04:04 pm
 If the main problem is clean, properly pressurized fuel delivery, it seems like lighting three engines would make it worse.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/06/2021 04:26 pm
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.

Exactly. If anything, 2 engines are better for the flip. 2 engines= offset thrust which=a quicker flip, however 3 works best for now to help with redundancy.

IMO, landing burns should be 2 engines all the way down, but the third engine is on standby in the event of one failing.
There will be some interesting trades to be had when trying to minimise propellent consumption v redundancy. Raptor firing needs to be very close to the ground and the Raptors need to be fired up for the shortest time possible. So fire up all three then turn off one if all three fire? Or light two and and hope a third could light if needed? Or fire two and throttle the good one up if the other fails?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/06/2021 04:33 pm
If the main problem is clean, properly pressurized fuel delivery, it seems like lighting three engines would make it worse.

Yeah, but I mean you could program the failing engine to turn itself off somehow if it’s trying to produce thrust no? And as that is happening the third could light. Not an expert on this stuff, just making some statements  ::) .
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/06/2021 04:35 pm
If the main problem is clean, properly pressurized fuel delivery, it seems like lighting three engines would make it worse.
   

I love how forthcoming they are at discussing issues, and sharing with public.

If its a fuel plumbing issue, hopefully its addressed in sn15 changes.

 Also if it were a debris hitting engine bay plumbing issue, causing the leak, that caused the hard start raptor rud.  Hopefully that is addressed also.

They might of slightly overpressurised to compensate for the fuel starvation issues on previous attempts, and to also fuel all 3 raptors from header tank.   Causing the leak, that caused the rud.

Or... could be a combination, of slightly cranked higher fuel pressure in plumbing, combined with getting hit with debris on liftoff that caused the leak. 

Does anyone know if the new plumbing design, looks more shielded from takeoff/static fire debris, than the old design?    My bet is it is, as they been dealing with pad debris for a while now. 

One thing for sure... raptors sure do put on a concrete throwing show, with their high thrust capability.    I can just imagine a rocky mars takeoff, how far rocks will fly in low gravity.   Better put those space houses underground or very far away from landing areas. lol
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: plehrack on 04/06/2021 04:37 pm
I think it's time to abandon the kick flip maneuver, it was never intended to be a normal part of the landing sequence anyways. If the methalox hot gas thrusters that are in development are not ready, use an array of cold gas thrusters or temporarily use Super Draco's in a moon lander configuration to do the flip. The flings can be placed in a anhedral configuration for maximum aerodynamic assistance. Moon lander thrusters can slow the decent while the fuel slosh baffles out, then fire the Raptors in their proper vertical configuration.

The Super Draco design is well understood and compact, the infrastructure for hot gas thrusters has to be developed anyways. SpaceX is continuing to try to solve a problem that they don't even have in a mature Starship design.

Just my two cents.

Peter Lehrack
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/06/2021 04:42 pm
I think it's time to abandon the kick flip maneuver, it was never intended to be a normal part of the landing sequence anyways. If the methalox hot gas thrusters that are in development are not ready, use an array of cold gas thrusters or temporarily use Super Draco's in a moon lander configuration to do the flip. The flings can be placed in a anhedral configuration for maximum aerodynamic assistance. Moon lander thrusters can slow the decent while the fuel slosh baffles out, then fire the Raptors in their proper vertical configuration.

The Super Draco design is well understood and compact, the infrastructure for hot gas thrusters has to be developed anyways. SpaceX is continuing to try to solve a problem that they don't even have in a mature Starship design.

Just my two cents.

Peter Lehrack

First off, welcome to the forums  :)

Secondly, the kick flip maneuver is the only sort of logical thing that starship could use IMO. The flop causes the vehicle to use its body to create as much drag as possible, and being honest, when you have to deal with entry heating, no other way to enter seems logical than belly first.

Thirdly, the landing thrusters moon-ship will use probably will be vacuum optimized, considering they will only be used to land on the moon, and getting to work at sea level just seems like too much of a pain. And then on top of that, trying to develop new engines seems like it would fail. Raptor will work, it’s just as much in its infancy as starship as a whole. I’m willing to bet starting with SN16/17, success will start to rain.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: kendrome on 04/06/2021 04:42 pm
I think it's time to abandon the kick flip maneuver, it was never intended to be a normal part of the landing sequence anyways.

There was a tweet from Elon responding to Tim Dodd (I think), that stated that yes the Raptors are required for the flip even when they have methane powered thrusters.

Edit: Link to tweet https://twitter.com/Erdayastronaut/status/1357497673675382785
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: plehrack on 04/06/2021 04:59 pm
Thanks for the welcome!

By kick flip, I mean using the Raptors to do the flip which to the best of my understanding will not be required once the hot gas thrusters are ready. Starship does have to flip, it's only using the Raptors to do it right now because the Methalox hot gas thrusters aren't ready.

The tweet from EDA does not appear to be responded to by Elon in the above post in regards to the HGT's, Elon just responded about which Raptor is selected during a kick flip.

Peter
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Chatskiy on 04/06/2021 05:00 pm
possibly a better quote: "Intuitively, it would seem so, but turbopump-fed Raptors have much higher thrust & propellant mass fraction than pressure-fed gas thrusters & they’re already there"

https://twitter.com/elonmusk/status/1357520341355159555
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aip on 04/06/2021 05:00 pm
https://twitter.com/13ericralph31/status/1379233656737161219

Quote
Just dawned on me that this is a much bigger deal than it might seem. For SpaceX to design and build its own custom bulk commodity storage tanks instead of buying what is arguably a fairly routine and cheap off-the-shelf technology, Starship production has to be DIRT CHEAP.

Here’s Eric’s write-up of that thought:

https://www.teslarati.com/spacex-starship-launch-pad-custom-storage-tanks/

Quote
SpaceX is building launch pad tanks out of Starship parts and that’s a big deal

By Eric Ralph
Posted on April 6, 2021

SpaceX has begun installing the first of numerous propellant storage tanks at its first orbital South Texas launch facilities – a mostly ordinary and expected step made extraordinary by the fact that those tanks will be built out of Starship parts.

Huh, I thought SpaceX was mostly conserving real estate with 9m diameter tanks rather than off-the-shelf 3m diameter tanks. Per the article, "3 to 4 dozen" 100,000 gallon tanks would take up acres they don't have at the launch site, with no ability to scale up by a factor of 5 to 10 without years-long environmental reviews. And if an errant StarShip hits the tank farm, they can replace the tank themselves in weeks, rather than waiting months for a custom order.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/06/2021 05:10 pm
Hi, long time lurker, first time posting. Please forgive long first post.
Been following Musk since his early Tesla days,  as I enjoy studying new engineering designs.

Welcome to de-lurkerhood!!!  Enjoyed reading your thoughts.

Don't really agree that horizontal landing makes any sense whatsoever, much less that it's the lightest weight solution.  That seems to have been pretty thoroughly discussed and dismissed.  It's hard to hand-wave around all the massive engineering challenges to thrust-structures, Raptors in the people places, and 90 degree rotating rear Raptors.

Out of curiosity, love to see where forward raptors were discussed, if you could kindly point me to those threads or sections.  I missed those. Only saw parachute, airbag talk, and early flip talk.

I'm no rocket scientist, so can definitely be wrong.   But seems to me, adding one or two forward raptors would be much lighter that the huge very heavy landing gear that would be needed to land vertically on Mars and hang serious tonnage off the side of a very tall starship, and winch it down to surface.   

    Then there would be even bigger problem of heat shielding the huge landing gear.  Not to mention, damaging aft heat shields on mars landings and take offs.     Seems to me, even if you needed 4 dedicated landing raptors, if gimbling rear raptors 90 is unfeasible.  Still a lighter simpler safer solution.  Raptors don't weigh much.   But I could be wrong. 

I envision the mars starship being much bigger than current prototypes, as current prototypes don't need to be huge to sort out raptor design.   Once raptor is sorted, for mars, why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel.   But lot more capacity.   

  Moving crew compartments more forward, lengthening nose, so easy when working with steel. 

Elon moves fast,  thinks big, and likes to surprise.  So I expect some massive mars cruise liners one day.   Hopefully, I live long enough to see it. Would be cool.  You want it to be massive, as you are stuck on board for a long while.

The current tiny landing gear design looks perfect for just getting stuff to orbit, and returning ship to landing pad.

I'm just thinking out loud what surprises might be next.  Loved the no landing gear booster surprise.  Catching it on fins will be epic!  Can't wait to see those first tries!

 Perhaps the mars version of starship will be a monster launched on two or three boosters. That would be truly epic, yet a very doable surprise.   

I would book that cruise.

Welcome to the forum and I hope you have a very engaging time here. I’m no rocket scientist either and I have learnt a huge amount from some of the locals here some of whom have a wealth of knowledge and have worked with rocket technology.

Elon Musk is determined to send humans to Mars at the earliest opportunity and the current ship is sufficient for that need so I doubt there will be much emphasis on redesigning the ship for some time. Much as this might appeal from the cool angle.

“Why not 12-15 meters across, or even bigger?   Just as easy to build, a bit more steel, and few more raptors, little more fuel. But lot more capacity.” No doubt much larger ships are possible and will be built one day, but be under no illusion that words like “easy” or “simple” are appropriate. If you are building a plastic model it might be simple but if you are building a flying block of flats and you want to double or treble its volume it is no small thing. Especially if you still expect that flying block of flats to do a quick pirouette just before landing.

Starship was designed to land vertically and will not land horizontally. This has been confirmed by Elon Musk in a tweet and stands to reason from an engineering perspective. It is easy to think small scale and wonder at the possibilities (I have done just that myself) but be very wary of this thinking because the real thing is enormous and scaling can play havoc with calculations. A model Starship might be easily supported on its side or at any bizarre angle by gluing on legs, the real thing will not.

The entire mass of Starship of the first starship to land on Mars will have to be supported by legs whatever the orientation it lands in. From a structural point of view vertical is stronger. Starship tubular sections can easily support their own weight vertically, but would bow and wobble like a bowl of jelly if turned through 90 degrees.

The current legs are a quick, cheap and dirty solution only intended for early prototypes while they clarify which leg design would be best.

“Perhaps the mars version of starship will be a monster launched on two or three boosters. That would be truly epic, yet a very doable surprise.” It would be an epic surprise but not very doable. As many people here will tell you rockets aren’t lego. Going from Falcon 9 to Falcon Heavy caused a major headache for SpaceX, despite being “just” 3 boosters strapped together.


Thanks for the welcome!

The way I see it. Landing stress is the easy part. 

Lot more stress on fins and body entering atmosphere at warp speed, getting heated up, and slowing that down.      That to me is the hard part. Heat shielding, and figuring out heat reentry stress on chassis.  Which is why there is a nose in a giant cage right now, about to get torqued from the fin mounts. 

Needs to be a pretty strong cage frame in forward fin area to withstand reentry forces and not lose fins, or crack open the nose.

So if strength is already there to withstand reentry force and heat, short landing legs there should be just fine.

As for bigger ships.   Bigger heaver ship means thicker stronger hull. Making dealing with reentry forces and heat easier.   

Light ship, wants to skip on the atmosphere surface, like a rock skipping on a lake.  While a heavier thicker hulled ship can carve right thru like a giant icebreaker ship, and hopefully dissipate the heat better.

Of course none of it is really "easy".  Otherwise it would of been done already.   But cool to see someone up for the challenges, and willing to fail repeatedly till he gets it right. 

Seems Musk embraces: "Every try is half a victory."   Eventually, it will be sorted out.  Although may look completely different than was first envisioned years ago when sorted.  Its the best approach for success, which I have no doubt will be achieved.   They seem to be on a great path.   



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/06/2021 05:16 pm
Flip with raptors might be slightly more efficient than flip with thrusters, but if delaying raptor startup can give them better startup/working conditions then it will be the way to go
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/06/2021 05:20 pm
Welcome to the forum!

If the main problem is clean, properly pressurized fuel delivery, it seems like lighting three engines would make it worse.
   

I love how forthcoming they are at discussing issues, and sharing with public.

If its a fuel plumbing issue, hopefully its addressed in sn15 changes.

 Also if it were a debris hitting engine bay plumbing issue, causing the leak, that caused the hard start raptor rud.  Hopefully that is addressed also.

[\quote]
The leaks appears during the flight, so I'd rather think is not a debris issue
[qoute]

They might of slightly overpressurised to compensate for the fuel starvation issues on previous attempts, and to also fuel all 3 raptors from header tank.   Causing the leak, that caused the rud.

Or... could be a combination, of slightly cranked higher fuel pressure in plumbing, combined with getting hit with debris on liftoff that caused the leak. 

Does anyone know if the new plumbing design, looks more shielded from takeoff/static fire debris, than the old design?    My bet is it is, as they been dealing with pad debris for a while now. 


IIUC the plumbing run over the thrust dome, so are shielded by it.

https://mobile.twitter.com/fael097/status/1324479821997608960

Is an old image, but from the bottom the engine bay looks identic, the differences are in the nterior. IDK if the design showed is the current one.
Quote

One thing for sure... raptors sure do put on a concrete throwing show, with their high thrust capability.    I can just imagine a rocky mars takeoff, how far rocks will fly in low gravity.   Better put those space houses underground or very far away from landing areas. lol
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/06/2021 05:22 pm
Flip with raptors might be slightly more efficient than flip with thrusters, but if delaying raptor startup can give them better startup/working conditions then it will be the way to go

Agreed.  Trading off fuel for something must not be done lightly...but if the "something" is a tangible decrease in the possibility of a RUD...probably a worthwhile tradeoff.   I'm sure SpaceX will consider it...pending future test results for the next few prototype iterations.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 04/06/2021 05:30 pm
Flip with raptors might be slightly more efficient than flip with thrusters, but if delaying raptor startup can give them better startup/working conditions then it will be the way to go

Agreed.  Trading off fuel for something must not be done lightly...but if the "something" is a tangible decrease in the possibility of a RUD...probably a worthwhile tradeoff.   I'm sure SpaceX will consider it...pending future test results for the next few prototype iterations.

Its also another system that simply has to work onto an already long list of systems that have to work. Four kinds of failure after the flip doesn't mean the flip can't work.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/06/2021 05:37 pm
Flip with raptors might be slightly more efficient than flip with thrusters, but if delaying raptor startup can give them better startup/working conditions then it will be the way to go

Agreed.  Trading off fuel for something must not be done lightly...but if the "something" is a tangible decrease in the possibility of a RUD...probably a worthwhile tradeoff.   I'm sure SpaceX will consider it...pending future test results for the next few prototype iterations.

Its also another system that simply has to work onto an already long list of systems that have to work. Four kinds of failure after the flip doesn't mean the flip can't work.

gas gas pressure fed engines are stupid simple and very reliable
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/06/2021 05:45 pm
https://twitter.com/13ericralph31/status/1379233656737161219 (https://twitter.com/13ericralph31/status/1379233656737161219)

Quote
Just dawned on me that this is a much bigger deal than it might seem. For SpaceX to design and build its own custom bulk commodity storage tanks instead of buying what is arguably a fairly routine and cheap off-the-shelf technology, Starship production has to be DIRT CHEAP.

Here’s Eric’s write-up of that thought:

https://www.teslarati.com/spacex-starship-launch-pad-custom-storage-tanks/ (https://www.teslarati.com/spacex-starship-launch-pad-custom-storage-tanks/)

Quote
SpaceX is building launch pad tanks out of Starship parts and that’s a big deal

By Eric Ralph
Posted on April 6, 2021

SpaceX has begun installing the first of numerous propellant storage tanks at its first orbital South Texas launch facilities – a mostly ordinary and expected step made extraordinary by the fact that those tanks will be built out of Starship parts.
After thinking about it, SX can probably build the tanks much cheaper than buying.


Shipping. Those tanks are too big to ship so they have to be built on site. The material has to be shipped. The shipper adds freight on top of base cost and SX is buying and shipping enough materials that shipping costs will be near as low as it can go. This segues into economies of scale.


SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world. Unless the purchasing department is staffed by morons they get the best price possible. Counter to this, purchased tanks would probably be made out of less expensive mild steel.


Another aspect of economies of scale is that SX appears to have much more ring capacity than they use. Not sure about stacking capacity. A downside is the tanks take up limited bay space that could go to ship building.


Profit. An outside tank builder works a profit margin into their tanks. SX built tanks have nada profit worked in.


Scheduling and operations. All scheduling is organic to SX. No outsiders to coordinate with. They can stop and start as operations dictate. No contractors demanding payment for SX imposesd holdups.


All in all, building their own tanks is the smartest thing they've done since they hired a water tank company to build Hoppy. Hmmm, I didn't really say that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/06/2021 05:49 pm
Flip with raptors might be slightly more efficient than flip with thrusters, but if delaying raptor startup can give them better startup/working conditions then it will be the way to go
That’s a good point. If they keep having Starship failures because of the flip maneuver, I don’t doubt they’ll engineer around it. Flip earlier, with a combination of aero surfaces and thrusters, and just eat the higher delta-v that requires (due to the higher terminal velocity when in the vertical position.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/06/2021 05:57 pm
I think it's time to abandon the kick flip maneuver, it was never intended to be a normal part of the landing sequence anyways. If the methalox hot gas thrusters that are in development are not ready, use an array of cold gas thrusters or temporarily use Super Draco's in a moon lander configuration to do the flip. The flings can be placed in a anhedral configuration for maximum aerodynamic assistance. Moon lander thrusters can slow the decent while the fuel slosh baffles out, then fire the Raptors in their proper vertical configuration.

The Super Draco design is well understood and compact, the infrastructure for hot gas thrusters has to be developed anyways. SpaceX is continuing to try to solve a problem that they don't even have in a mature Starship design.

Just my two cents.

Peter Lehrack
Peter, AIUI, the flip has been there all along. Can you point to something?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/06/2021 06:02 pm
Welcome to the forum!

If the main problem is clean, properly pressurized fuel delivery, it seems like lighting three engines would make it worse.
   

I love how forthcoming they are at discussing issues, and sharing with public.

If its a fuel plumbing issue, hopefully its addressed in sn15 changes.

 Also if it were a debris hitting engine bay plumbing issue, causing the leak, that caused the hard start raptor rud.  Hopefully that is addressed also.

[\quote]
The leaks appears during the flight, so I'd rather think is not a debris issue
[qoute]

They might of slightly overpressurised to compensate for the fuel starvation issues on previous attempts, and to also fuel all 3 raptors from header tank.   Causing the leak, that caused the rud.

Or... could be a combination, of slightly cranked higher fuel pressure in plumbing, combined with getting hit with debris on liftoff that caused the leak. 

Does anyone know if the new plumbing design, looks more shielded from takeoff/static fire debris, than the old design?    My bet is it is, as they been dealing with pad debris for a while now. 


IIUC the plumbing run over the thrust dome, so are shielded by it.

https://mobile.twitter.com/fael097/status/1324479821997608960

Is an old image, but from the bottom the engine bay looks identic, the differences are in the nterior. IDK if the design showed is the current one.
Quote

One thing for sure... raptors sure do put on a concrete throwing show, with their high thrust capability.    I can just imagine a rocky mars takeoff, how far rocks will fly in low gravity.   Better put those space houses underground or very far away from landing areas. lol


Cool plumbing graphics!

It could be possible debris on takeoff dented/scratched/weakened that section of fuel plumbing, which then started to leak under high heat and vibration of 3 raptors at thrust, as we saw on video, then boom on relight. 

 I'm sure they are inspecting the hell out of the found parts.  I wonder if they will continue to share what they find?  Or if it even matters at this point, as sn15 is a whole new fuel plumbing design.   

  Sometimes it hard for me to believe, all these close up raptor photos and plumbing graphics being shared in public.   But then again, I'm sure these days,  China and Russia have even better photos of the production site from space, and spies.

I often wonder if some public stuff shared is fake, to throw copy cat countries off.  I would hope that is the case. lol


Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 04/06/2021 06:13 pm
SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world.

I *seriously* doubt that.  Think of all the appliance manufacturers making hundreds of thousands of stainless-sheeted refrigerators, dishwashers, and so on, plus all the plumbing manufacturers making all those stainless sinks and other products for homes and restaurants.  There are tons of uses of stainless sheet.  2019 global stainless production was around 52 million tons ~= 2 million truck loads.  That's not all sheet, but a lot of it is.  SpaceX has received dozens (maybe a couple hundred) truck loads?  Drop in the ocean would be my bet.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/06/2021 06:19 pm
Per Nomadd’s photo in the production update thread, we have 2 nosecones!

A glimpse of another nose lurking in Tent 3.

On right is most likely for SN16, along with its barrel section awaiting it outside.

On the left is most likely for SN17!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/06/2021 06:24 pm

Thanks for the welcome!

The way I see it. Landing stress is the easy part. 

Lot more stress on fins and body entering atmosphere at warp speed, getting heated up, and slowing that down.      That to me is the hard part. Heat shielding, and figuring out heat reentry stress on chassis.  Which is why there is a nose in a giant cage right now, about to get torqued from the fin mounts. 

Needs to be a pretty strong cage frame in forward fin area to withstand reentry forces and not lose fins, or crack open the nose.

So if strength is already there to withstand reentry force and heat, short landing legs there should be just fine.

As for bigger ships.   Bigger heaver ship means thicker stronger hull. Making dealing with reentry forces and heat easier.   

Light ship, wants to skip on the atmosphere surface, like a rock skipping on a lake.  While a heavier thicker hulled ship can carve right thru like a giant icebreaker ship, and hopefully dissipate the heat better.

Of course none of it is really "easy".  Otherwise it would of been done already.   But cool to see someone up for the challenges, and willing to fail repeatedly till he gets it right. 

Seems Musk embraces: "Every try is half a victory."   Eventually, it will be sorted out.  Although may look completely different than was first envisioned years ago when sorted.  Its the best approach for success, which I have no doubt will be achieved.   They seem to be on a great path.
Wow. I don't know where to start.


The aero loads during max heating are surprisingly low. It still needs to be investigated, but low.


Making the ship bigger will make it heavier but less dense. This is a good thing for aero breaking but very hard to do. It is easy to design a rocket longer but hard, Hard, HARD to make it wider. Longer is just more of the same. Wider is an entirely new design because cross section (engine space for example) scales at the square and volume (propellant capacity for example) scales at the cube. Almost every trade off needs to be rethought and every calculation redone. The result is an entirely different rocket.


Your misconception on skipping off is the same one I had until all these rascally NSFers educated me. What happens is if the reentering body is at too shallow an angle it cuts a cord line through the curved atmosphere that is wrapped around a sphere. It's a combination of angle and density. A light fluffy body slows down faster and starts dropping faster than the atmosphere curves. A dense body will punch through. For any density of body there is a minimum angle that will work.


Hope this helps.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: plehrack on 04/06/2021 06:29 pm
There is a difference between a 'flip' and a 'kick flip'. The 'kick flip' requires Raptors to be ignited in a horizontal position and continue firing during the flip while the fuel is sloshing around which has been, uh, problematic. Flipping with hot gas thrusters and igniting the Raptors in a vertical orientation after the sloshing settles fixes a lot of the current complexity and problems.

Peter
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DetailCurious on 04/06/2021 06:30 pm
https://twitter.com/13ericralph31/status/1379233656737161219 (https://twitter.com/13ericralph31/status/1379233656737161219)

Quote
Just dawned on me that this is a much bigger deal than it might seem. For SpaceX to design and build its own custom bulk commodity storage tanks instead of buying what is arguably a fairly routine and cheap off-the-shelf technology, Starship production has to be DIRT CHEAP.

Here’s Eric’s write-up of that thought:

https://www.teslarati.com/spacex-starship-launch-pad-custom-storage-tanks/ (https://www.teslarati.com/spacex-starship-launch-pad-custom-storage-tanks/)

Quote
SpaceX is building launch pad tanks out of Starship parts and that’s a big deal

By Eric Ralph
Posted on April 6, 2021

SpaceX has begun installing the first of numerous propellant storage tanks at its first orbital South Texas launch facilities – a mostly ordinary and expected step made extraordinary by the fact that those tanks will be built out of Starship parts.
After thinking about it, SX can probably build the tanks much cheaper than buying.


Shipping. Those tanks are too big to ship so they have to be built on site. The material has to be shipped. The shipper adds freight on top of base cost and SX is buying and shipping enough materials that shipping costs will be near as low as it can go. This segues into economies of scale.


SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world. Unless the purchasing department is staffed by morons they get the best price possible. Counter to this, purchased tanks would probably be made out of less expensive mild steel.


Another aspect of economies of scale is that SX appears to have much more ring capacity than they use. Not sure about stacking capacity. A downside is the tanks take up limited bay space that could go to ship building.


Profit. An outside tank builder works a profit margin into their tanks. SX built tanks have nada profit worked in.


Scheduling and operations. All scheduling is organic to SX. No outsiders to coordinate with. They can stop and start as operations dictate. No contractors demanding payment for SX imposesd holdups.


All in all, building their own tanks is the smartest thing they've done since they hired a water tank company to build Hoppy. Hmmm, I didn't really say that.

There is one more consideration.  You have to look at system costs, not isolated theoretical ones.

SX can build SS & boosters faster than it can fly them.  So either it keeps the facility busy building for scrap, it pays people to be idle, it does layoffs - or it can use the capacity to build tanks. 

Building tanks, the labor is "free".  And it's an activity that keeps their skills up - and maybe generates learnings that apply to flying vehicles.  Using excess capacity to build something that you need wipes out a fair bit of the cost that would be incurred if you only built tanks. 

It's like having people in a boring/useless but mandatory meeting knit socks.  You don't charge the people's time to the cost of socks.  Just the yarn.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/06/2021 06:33 pm
Flip with raptors might be slightly more efficient than flip with thrusters, but if delaying raptor startup can give them better startup/working conditions then it will be the way to go
That’s a good point. If they keep having Starship failures because of the flip maneuver, I don’t doubt they’ll engineer around it. Flip earlier, with a combination of aero surfaces and thrusters, and just eat the higher delta-v that requires (due to the higher terminal velocity when in the vertical position.
They don't need to go to the unstable vertical. Hold it at some lesser angle for a beat or two then light em off. 30deg? 45deg? Don't really know.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/06/2021 06:33 pm
There is a difference between a 'flip' and a 'kick flip'. The 'kick flip' requires Raptors to be ignited in a horizontal position and continue firing during the flip while the fuel is sloshing around which has been, uh, problematic. Flipping with hot gas thrusters and igniting the Raptors in a vertical orientation after the sloshing settles fixes a lot of the current complexity and problems.

Peter
With the slight caveat that it has been repeatedly stated that thrusters don't work the effect a flip. Not sure if hot gas thrusters specifically or only cold gas RCS were considered in these statements though, but hot gas thrusters seems to be too far away in any case for spacex to consider using instead of trying and trying again with main engine flips.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/06/2021 06:36 pm
I wonder if they’ll start just using them for other things, like housing? LOL. I mean,  a totally fitted out Starship would be like an RV, right? And they’re already using those...

A giant, vertical Airstream. LOL.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/06/2021 06:38 pm
Welcome to the forum!

If the main problem is clean, properly pressurized fuel delivery, it seems like lighting three engines would make it worse.
   

I love how forthcoming they are at discussing issues, and sharing with public.

If its a fuel plumbing issue, hopefully its addressed in sn15 changes.

 Also if it were a debris hitting engine bay plumbing issue, causing the leak, that caused the hard start raptor rud.  Hopefully that is addressed also.

[\quote]
The leaks appears during the flight, so I'd rather think is not a debris issue
[qoute]

They might of slightly overpressurised to compensate for the fuel starvation issues on previous attempts, and to also fuel all 3 raptors from header tank.   Causing the leak, that caused the rud.

Or... could be a combination, of slightly cranked higher fuel pressure in plumbing, combined with getting hit with debris on liftoff that caused the leak. 

Does anyone know if the new plumbing design, looks more shielded from takeoff/static fire debris, than the old design?    My bet is it is, as they been dealing with pad debris for a while now. 


IIUC the plumbing run over the thrust dome, so are shielded by it.

https://mobile.twitter.com/fael097/status/1324479821997608960

Is an old image, but from the bottom the engine bay looks identic, the differences are in the nterior. IDK if the design showed is the current one.
Quote

One thing for sure... raptors sure do put on a concrete throwing show, with their high thrust capability.    I can just imagine a rocky mars takeoff, how far rocks will fly in low gravity.   Better put those space houses underground or very far away from landing areas. lol


Cool plumbing graphics!

It could be possible debris on takeoff dented/scratched/weakened that section of fuel plumbing, which then started to leak under high heat and vibration of 3 raptors at thrust, as we saw on video, then boom on relight. 
IMO is possible
Quote

 I'm sure they are inspecting the hell out of the found parts.  I wonder if they will continue to share what they find?  Or if it even matters at this point, as sn15 is a whole new fuel plumbing design.   

If your theory is true  sn15 plumbing redesign won't affect the problem. As I said the changes to the plumbing are in the LOx tanks, if a pipe has been hitten and then leake, as you wonder, that pipe is in the raptor, and the changes to the piping aren't there. But maybe in the changes there is more shielding to Raptor powerheads. In this case, if the cause is what you say, the issue should be solved
Quote

  Sometimes it hard for me to believe, all these close up raptor photos and plumbing graphics being shared in public.

I too think about this often. Is a tradeoff between letting other company know what they are doing and engaging public
Quote

But then again, I'm sure these days,  China and Russia have even better photos of the production site from space, and spies.

I don't think China and Russia are too intersted int Starship. They have their own problems (I think they rather use their spies to look at DoD launches, and so at ULA)and rockets. We don't know any project of a completely reusable rocket from them, and maybe aren't even intersted
Quote

I often wonder if some public stuff shared is fake, to throw copy cat countries off.  I would hope that is the case. lol

I think it isn't as this. In this forum and outside there are really smart people and real rocket engineers, that would have understood that something they share is fake.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/06/2021 06:44 pm
SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world.

I *seriously* doubt that.  Think of all the appliance manufacturers making hundreds of thousands of stainless-sheeted refrigerators, dishwashers, and so on, plus all the plumbing manufacturers making all those stainless sinks and other products for homes and restaurants.  There are tons of uses of stainless sheet.  2019 global stainless production was around 52 million tons ~= 2 million truck loads.  That's not all sheet, but a lot of it is.  SpaceX has received dozens (maybe a couple hundred) truck loads?  Drop in the ocean would be my bet.
Agreed, but this is spread over many manufacturers. A sq meter of sheet will easily make ~9 14cm frying pans, one stove top, half a fridge door or one oven face. Go out to a Home Depot and hang around for awhile. How many stainless fridges are sold in a week? Don't forget multiple manufacturers.


Of course I've not run any numbers so I'm running on opinion. But still...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/06/2021 07:01 pm
Though I am hesitant to make what are most likely bad design suggestions, it seems obvious to me they should enlarge the methane down comer to the point where it is capacious enough to provide for a safe landing. It would need a valve on top that could close before the flip. This may move the common dome a bit, but won't change OML.

The best part is no spherical part?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/06/2021 07:10 pm
Per previous conversations, too long to quote, I don't think the closeup pictures of Raptor really give away any secrets. FFSC is known among engine builders, even if they haven't built them. The real secrets are the internals, the material science, and temperature/pressures that every component operates at, and the control algorithms that make it all work. Outside photos give very little of this detailed information.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 04/06/2021 07:21 pm
There is one more consideration.  You have to look at system costs, not isolated theoretical ones.

SX can build SS & boosters faster than it can fly them.  So either it keeps the facility busy building for scrap, it pays people to be idle, it does layoffs - or it can use the capacity to build tanks. 

Building tanks, the labor is "free".  And it's an activity that keeps their skills up - and maybe generates learnings that apply to flying vehicles.  Using excess capacity to build something that you need wipes out a fair bit of the cost that would be incurred if you only built tanks. 

It's like having people in a boring/useless but mandatory meeting knit socks.  You don't charge the people's time to the cost of socks.  Just the yarn.

All of those are good points but probably not the deciding factor. Even if the tanks were free, the cost to move them would be extreme.

You are looking at moving an object with the smallest dimension of 9 meters. That means major roads only (which must be shut down). It means moving every power line that crosses the route and no overpasses. It means coordinating with police and fire departments of every Podunk county on the way. Not to mention the vast number of permits required to do any of that stuff. Then perform the same circus act 6 more times to move them all.

The reason why houses are almost always torn down rather than moved is that the cost to move them is more than to just build a new one on site. Same economics applies here, even if SpaceX did not already have the capability to build the tanks, paying somebody else to set up and operate all the equipment to build tanks on site is likely far cheaper than moving them any distance.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/06/2021 07:21 pm
SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world.

I *seriously* doubt that.  Think of all the appliance manufacturers making hundreds of thousands of stainless-sheeted refrigerators, dishwashers, and so on, plus all the plumbing manufacturers making all those stainless sinks and other products for homes and restaurants.  There are tons of uses of stainless sheet.  2019 global stainless production was around 52 million tons ~= 2 million truck loads.  That's not all sheet, but a lot of it is.  SpaceX has received dozens (maybe a couple hundred) truck loads?  Drop in the ocean would be my bet.
Agreed, but this is spread over many manufacturers. A sq meter of sheet will easily make ~9 14cm frying pans, one stove top, half a fridge door or one oven face. Go out to a Home Depot and hang around for awhile. How many stainless fridges are sold in a week? Don't forget multiple manufacturers.


Of course I've not run any numbers so I'm running on opinion. But still...
US consumption of stainless steel is about 200,000 tons per month. If SpaceX makes a Starship or booster or GSE tank once a week, each about 200 tons (if you include scrap), that’s 800 tons per month. Or about 0.4% of US stainless consumption.

Of course, if you pick a certain alloy and a certain stock type and thickness, SpaceX could easily be the lion’s share. 304/316 are the most common type. Maybe 301 is 5%? I have no idea. That’d mean SpaceX is 8% of US consumption. If there are 10 different stock sizes, and SpaceX predominantly uses one, that could mean SpaceX is the biggest user of that specific stock.

Of course if SpaceX is making their own custom alloy then they will be the majority user of it, won’t they? ;)

A $30 million steel mini mill can produce around 100,000 tons of steel per year, which is 10 times what SpaceX needs (although if they increased throughout to one vehicle/tank/habitat/apartment a day, would be about right). So SpaceX could actually easily afford to buy and build their own steel mini mill for custom alloys.

Would help them figure out what they need to do for Mars, too.



EDIT: although if the rumor trail is right, they may end up using steel from this mill in Texas: https://electrek.co/2020/12/10/tesla-rumored-cybertruck-steel-new-billion-factory-texas/

(It is a kind of electric arc furnace steel mill, not a coke fired mill.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/06/2021 07:31 pm
Though I am hesitant to make what are most likely bad design suggestions, it seems obvious to me they should enlarge the methane down comer to the point where it is capacious enough to provide for a safe landing. It would need a valve on top that could close before the flip. This may move the common dome a bit, but won't change OML.

The best part is no spherical part?
I wonder why they didn't do that?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Paul_G on 04/06/2021 07:36 pm
Though I am hesitant to make what are most likely bad design suggestions, it seems obvious to me they should enlarge the methane down comer to the point where it is capacious enough to provide for a safe landing. It would need a valve on top that could close before the flip. This may move the common dome a bit, but won't change OML.

The best part is no spherical part?
I wonder why they didn't do that?

By having the methane header tank where it is, it may put the Centre of Mass in the right place - remove the header tank and you might move the CoM lower than you want it?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DigitalMan on 04/06/2021 07:51 pm
SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world.

I *seriously* doubt that.  Think of all the appliance manufacturers making hundreds of thousands of stainless-sheeted refrigerators, dishwashers, and so on, plus all the plumbing manufacturers making all those stainless sinks and other products for homes and restaurants.  There are tons of uses of stainless sheet.  2019 global stainless production was around 52 million tons ~= 2 million truck loads.  That's not all sheet, but a lot of it is.  SpaceX has received dozens (maybe a couple hundred) truck loads?  Drop in the ocean would be my bet.
Agreed, but this is spread over many manufacturers. A sq meter of sheet will easily make ~9 14cm frying pans, one stove top, half a fridge door or one oven face. Go out to a Home Depot and hang around for awhile. How many stainless fridges are sold in a week? Don't forget multiple manufacturers.


Of course I've not run any numbers so I'm running on opinion. But still...

It happens to be notoriously difficult to buy a new fridge nowadays. We tried to buy one a several months ago. I don't know how many are sold, but they tend to sell out right away around here.

Forget about getting a particular model you are interested in. The salespeople are attributing it to the pandemic.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/06/2021 07:51 pm
Also, because plumbing size is important.  Remember that these things are vibrating, and bouncing around, and shaking, and all kinds of things.  Resonances in plumbing and/or fluid flow are well known to happen.  The size of these things needs to be carefully tuned to minimize that kind of thing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 04/06/2021 08:01 pm
Though I am hesitant to make what are most likely bad design suggestions, it seems obvious to me they should enlarge the methane down comer to the point where it is capacious enough to provide for a safe landing. It would need a valve on top that could close before the flip. This may move the common dome a bit, but won't change OML.

The best part is no spherical part?
I wonder why they didn't do that?

They are certainly aware of such a trick - the original ITS booster used the downcomer as the header tank.

But a spherical tank is more optimal for long term storage during a interplanetary coast (to make it easier to keep the propellant in cryo form), so I imagine that's what they would prefer to keep.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/06/2021 08:02 pm
SX is, as a guess, the single largest user of stainless sheet in the US, and possibly the world.

I *seriously* doubt that.  Think of all the appliance manufacturers making hundreds of thousands of stainless-sheeted refrigerators, dishwashers, and so on, plus all the plumbing manufacturers making all those stainless sinks and other products for homes and restaurants.  There are tons of uses of stainless sheet.  2019 global stainless production was around 52 million tons ~= 2 million truck loads.  That's not all sheet, but a lot of it is.  SpaceX has received dozens (maybe a couple hundred) truck loads?  Drop in the ocean would be my bet.
Agreed, but this is spread over many manufacturers. A sq meter of sheet will easily make ~9 14cm frying pans, one stove top, half a fridge door or one oven face. Go out to a Home Depot and hang around for awhile. How many stainless fridges are sold in a week? Don't forget multiple manufacturers.


Of course I've not run any numbers so I'm running on opinion. But still...

It happens to be notoriously difficult to buy a new fridge nowadays. We tried to buy one a several months ago. I don't know how many are sold, but they tend to sell out right away around here.

Forget about getting a particular model you are interested in. The salespeople are attributing it to the pandemic.
I blame Elon Musk myself, but we are getting off topic...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/06/2021 08:06 pm
Though I am hesitant to make what are most likely bad design suggestions, it seems obvious to me they should enlarge the methane down comer to the point where it is capacious enough to provide for a safe landing. It would need a valve on top that could close before the flip. This may move the common dome a bit, but won't change OML.

The best part is no spherical part?
I wonder why they didn't do that?

Take a pipe with a little bit of air in it. As you tip it back and forth in the horizontal position the air bubble moves the length of the pipe. Now do that with a pipe with a spherical ball on one end. The bubble stays in the ball.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tyrred on 04/06/2021 10:18 pm
There is a difference between a 'flip' and a 'kick flip'. The 'kick flip' requires Raptors to be ignited in a horizontal position and continue firing during the flip while the fuel is sloshing around which has been, uh, problematic. Flipping with hot gas thrusters and igniting the Raptors in a vertical orientation after the sloshing settles fixes a lot of the current complexity and problems.

Peter

You keep using that word. I don't think it means what you think it means.

A kickflip is a skateboarding trick.  The board actually flips 360° around its long axis. Starship does no such thing.

Nit pick, but terminology matters.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: kdhilliard on 04/06/2021 10:19 pm
Tweeted yesterday (https://forum.nasaspaceflight.com/index.php?topic=47352.msg2215855#msg2215855) regarding the SN11 failure:
Quote from: Elon Musk
A (relatively) small CH4 leak led to fire on engine 2 & fried part of avionics, causing hard start attempting landing burn in CH4 turbopump.

Do we know which engine #2 was?
Was it one of the two which would have normally been started for the flip (à la SN10), or was it the third which was started as a precaution in case one of the other two failed to start?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/06/2021 10:24 pm

Wow. I don't know where to start.


The aero loads during max heating are surprisingly low. It still needs to be investigated, but low.


Making the ship bigger will make it heavier but less dense. This is a good thing for aero breaking but very hard to do. It is easy to design a rocket longer but hard, Hard, HARD to make it wider. Longer is just more of the same. Wider is an entirely new design because cross section (engine space for example) scales at the square and volume (propellant capacity for example) scales at the cube. Almost every trade off needs to be rethought and every calculation redone. The result is an entirely different rocket.


Your misconception on skipping off is the same one I had until all these rascally NSFers educated me. What happens is if the reentering body is at too shallow an angle it cuts a cord line through the curved atmosphere that is wrapped around a sphere. It's a combination of angle and density. A light fluffy body slows down faster and starts dropping faster than the atmosphere curves. A dense body will punch through. For any density of body there is a minimum angle that will work.


Hope this helps.

Of course it helps, I'm a dummy when it comes to space stuff.

I was guessing that at high altitude, max heat, not much force being applied.  But once that fully heated up speeding starship hits dense lower atmosphere, and transitions from plane' like burning off reentry speed mode, into stalling into slow terminal velocity skydive mode.  There would be substantial forces acting on the fins and body during that transition, and speed burn off.  Greater forces than just laying on its side on the ground.   


Now I'm rethinking, because of your reply, that initiating the stall with fins all the way back, lessens the force applied on them dramatically during stall maneuver into skydive mode. Then they slowly reopen them again, lessening the slowing down forces on them.  So maybe it won't be as much force applied to fins and body as I first thought. 



Interesting and exciting to see how it works out for sure.
Thanks for making me think!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kevin9 on 04/06/2021 10:37 pm
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.
Which is why the 3 should be started at that point to see what you have working, then turn off if need be. Getting the engine or number of engines you require at a seconds notice isnt something available at this moment in time. Shame to see it crash with a perfectly good engine not even used while broken ones flail about doing very little, just before it eats concrete. It makes sense, especially if humans are aboard the ship in the near future for this to be a proceedure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dakobed82 on 04/07/2021 04:56 am
Making the ship bigger will make it heavier but less dense. This is a good thing for aero breaking but very hard to do. It is easy to design a rocket longer but hard, Hard, HARD to make it wider. Longer is just more of the same. Wider is an entirely new design because cross section (engine space for example) scales at the square and volume (propellant capacity for example) scales at the cube. Almost every trade off needs to be rethought and every calculation redone. The result is an entirely different rocket.

I'm not a structural engineer, but I'm not sure we can assume that making the ship bigger will make it less dense.  As you mention, this is a classic example of the square-cube law at work.  To steal from the Wikipedia article on that topic, when an object is scaled up by a multiplier r, its volume and mass are increased by the cube of the multiplier while its surface area increases only by the square of said multiplier.   By rough approximation, only the surface area of Starship (the tank walls and domes) is available to resist loads, and that area grows by r-squared while mass grows by r-cubed assuming constant density.   Since most forces are proportional to mass, the loading per unit area increases by r.  To make the constant density assumption work, the average strength must increase by a factor of r; otherwise you need to add more material.

Sometimes this is not too difficult, and you might even be able to decrease density if relatively "fixed" mass can be amortized over a larger structure.  However, eventually you reach a point of diminishing returns to scale; keep going beyond that and eventually you'll exhaust the supply of stronger materials and better building techniques no matter how much extra cost you're willing to incur.

In any case, even if the constant density assumption holds, the square-cube law is still bad news for reentry.  Since surface area provides the aerodynamic drag to slow you down, the "density" you care about is surface loading (mass/area), not three-dimensional density (mass/volume).  With mass proportional to r-cubed and surface area proportional to r-squared, reentry gets harder the higher r goes.  Rocket Lab can apparently recover an Electron booster without an entry burn; the larger Falcon 9 has grid fins to increase the angle of attack during descent and provide some additional surface area for more drag but it still needs the Merlins to slow down sufficiently.  Starship has a much more heat-resistant skin and dramatically higher cross-sectional area on reentry, so it may get away without an entry burn, but that's a tougher challenge for a 12- or 18-meter Super Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hkultala on 04/07/2021 06:24 am
Flipping with hot gas thrusters and igniting the Raptors in a vertical orientation after the sloshing settles fixes a lot of the current complexity and problems.

What hot gas thrusters?

The orbital manuverng thrusters that will be installed on final Starship versions will not have enough thrust.

Also, firing those thrusters agains incoming airflow is not so simple.

And, then the flip would have to be don much earlier.

What you are proposing adds lots of extra weight, reduces performance, and adds new problem.s
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/07/2021 06:27 am
Flipping with hot gas thrusters and igniting the Raptors in a vertical orientation after the sloshing settles fixes a lot of the current complexity and problems.

What hot gas thrusters?

The orbital manuverng thrusters that will be installed on final Starship versions will not have enough thrust.

Also, firing those thrusters agains incoming airflow is not so simple.

And, then the flip would have to be don much earlier.

What you are proposing adds lots of extra weight, reduces performance, and adds new problem.s
The ones on Lunar Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 04/07/2021 06:59 am
Lunar starship will not be returning for a landing on earth, no heat shield or flaps. So lunar SS is irrelevant in regards to landing skydive mode and flip...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: retrojet on 04/07/2021 07:20 am
New Virtual Flyover Video:
SpaceX Starship Facility Update / April 2021
Covering the Starship Structures and Buildings at Roberts Road and at Pad39A.
The Launch-Pad-Tower as seen in this video was planed to be build in Boca Chica as well.

https://youtu.be/BfSI7Kj5R3M (https://youtu.be/BfSI7Kj5R3M)

The second picture attached, shows you an official spacex render, that sufaced end of last year (2020), showing the old design of the launch tower. The Launch Tower was already half way done at the Pad39A.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: smndk on 04/07/2021 07:54 am
Flipping with hot gas thrusters and igniting the Raptors in a vertical orientation after the sloshing settles fixes a lot of the current complexity and problems.

What hot gas thrusters?

The orbital manuverng thrusters that will be installed on final Starship versions will not have enough thrust.

Also, firing those thrusters agains incoming airflow is not so simple.

And, then the flip would have to be don much earlier.

What you are proposing adds lots of extra weight, reduces performance, and adds new problem.s
The ones on Lunar Starship.

Exactly which kind of landing thrusters are they planning on using on Lunar Starship? Methalox?

I think someone mentioned SuperDracos, but I dont suppose that they want to add hypergolics to StarShip?

Is it still the plan only to carry LOX and LCH4 on the final versions of StarShip?


Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/07/2021 08:08 am
...
Exactly which kind of landing thrusters are they planning on using on Lunar Starship? Methalox?
...
Yes, methalox.  Was called out in the NASA selection statement as a risk.
edit: see Artemis Source Selection - NextSTEP-2 Appendix H: Human Landing System Broad Agency Announcement NNH19ZCQ001K_APPENDIX-H-HLS (https://beta.sam.gov/api/prod/opps/v3/opportunities/resources/files/3488c1f1556745cb87c046135d8ffe00/download?api_key=null&token=), pg. 12-13, NASA 28-Apr-2021.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Surgeon on 04/07/2021 08:40 am
New Virtual Flyover Video:
SpaceX Starship Facility Update / April 2021
Covering the Starship Structures and Buildings at Roberts Road and at Pad39A.
The Launch-Pad-Tower as seen in this video was planed to be build in Boca Chica as well.



The second picture attached, shows you an official spacex render, that sufaced end of last year (2020), showing the old design of the launch tower. The Launch Tower was already half way done at the Pad39A.

thats awesome! How/where did that 'offical render' come from?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: retrojet on 04/07/2021 09:29 am
Austin Bernard posted a video in late 2020. It was an offical (but only internal uploaded) youtube video from the spacex channel. I just grabbed the picture showing the old design stand. Unfortunatly i can not find a link to the complete video. Maybe someone can share it?

New Virtual Flyover Video:
SpaceX Starship Facility Update / April 2021
Covering the Starship Structures and Buildings at Roberts Road and at Pad39A.
The Launch-Pad-Tower as seen in this video was planed to be build in Boca Chica as well.



The second picture attached, shows you an official spacex render, that sufaced end of last year (2020), showing the old design of the launch tower. The Launch Tower was already half way done at the Pad39A.

thats awesome! How/where did that 'offical render' come from?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: enbandi on 04/07/2021 09:50 am
Austin Bernard posted a video in late 2020. It was an offical (but only internal uploaded) youtube video from the spacex channel. I just grabbed the picture showing the old design stand. Unfortunatly i can not find a link to the complete video. Maybe someone can share it?

New Virtual Flyover Video:

The second picture attached, shows you an official spacex render, that sufaced end of last year (2020), showing the old design of the launch tower. The Launch Tower was already half way done at the Pad39A.

thats awesome! How/where did that 'offical render' come from?

Seems like this two below. Not sure if those are the original you seen, but the content match.
 
https://twitter.com/austinbarnard45/status/1328083098421047302
https://www.youtube.com/watch?v=GX-VLlnd9Ks

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tyrred on 04/07/2021 09:57 am
Austin Bernard posted a video in late 2020. It was an offical (but only internal uploaded) youtube video from the spacex channel. I just grabbed the picture showing the old design stand. Unfortunatly i can not find a link to the complete video. Maybe someone can share it?

New Virtual Flyover Video:
SpaceX Starship Facility Update / April 2021
Covering the Starship Structures and Buildings at Roberts Road and at Pad39A.
The Launch-Pad-Tower as seen in this video was planed to be build in Boca Chica as well.


The second picture attached, shows you an official spacex render, that sufaced end of last year (2020), showing the old design of the launch tower. The Launch Tower was already half way done at the Pad39A.

thats awesome! How/where did that 'offical render' come from?

Seems like this two below. Not sure if those are the original you seen, but the content match.
 
https://twitter.com/austinbarnard45/status/1328083098421047302


Credit: unknown... sadly we may never know what the porpoise of the two flanking towers was supposed to be.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: retrojet on 04/07/2021 10:10 am
i just found the video:

https://youtu.be/GX-VLlnd9Ks (https://youtu.be/GX-VLlnd9Ks)

I realy like the design of the launch stand. Looks more industrial and not that sleek and over-designed ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MdBee on 04/07/2021 10:18 am
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.
Which is why the 3 should be started at that point to see what you have working, then turn off if need be. [...]

IIRC this is what SN11 was trying to do, lighting all 3 Like SN10 did, and then disabling 2. The issue as I understand it wasn't that engine#2 was underperforming and could be disabled, but that it "overperformed" on ignition (hard start) and RUD'd, which they couldn't prevent in time.

F9 has a reinforced octoweb structure that limits the damage from an engine RUD, at least on ascent. Not sure we've seen anything similar for SS/SH yet?

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/07/2021 11:05 am
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.
Which is why the 3 should be started at that point to see what you have working, then turn off if need be. [...]

IIRC this is what SN11 was trying to do, lighting all 3 Like SN10 did, and then disabling 2. The issue as I understand it wasn't that engine#2 was underperforming and could be disabled, but that it "overperformed" on ignition (hard start) and RUD'd, which they couldn't prevent in time.

F9 has a reinforced octoweb structure that limits the damage from an engine RUD, at least on ascent. Not sure we've seen anything similar for SS/SH yet?
SN11 was trying to light 3 engines and shut down one. After SN10 they decided to have 2 engines running all the way to touchdown.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: fuzzout on 04/07/2021 11:38 am
I think best way to look at SN11 is to think: It was the last of suborbital gen 1 Starship prototypes, it was already built and they were running out of gen 1 raptors to use on it... so they just stapled together what they had and let 'er rip; they took what data they could from it and that's that.

I suspect SN8 exceeded expectations by almost nailing the touchdown. It's highly likely they calculated that they'd need more than 4 prototypes to reach the point that SN8 reached. The tech on those starships was likely not "landing-ready", it was just there to get it up in the air and have it skydive back down on target.

I can't wait to hear the gen 2 raptors fire; a more modern (it even looks sleeker) version of these beastly engines on a starship that's likely designed with the expectation of a smooth landing. It's gonna be a glorious thing to observe!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 04/07/2021 01:01 pm
For the "flip with hot gas thrusters" fans... Which is more efficent?

A separate thruster system burning the same propellant as autogen gasses, to stabilize the rocket vertical before lighting the main raptors...

Or dumping the same hot gas directly into the header tanks to counter ullage collapse, and let the "gas bubbles" get sucked up and condense back into propellant in the fuel lines?

The problems with the Helium system are a red herring. we want to get RID of the helium system. That means dealing with the Ullage collapse problem.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/07/2021 02:01 pm
An interesting question about reentry profile which doesn't apply to the 10km tests they are doing.

For the 10km test they transition to header tanks while they have thrust in the vertical position(X+ direction). This will cause all ullage gas to be in the header tank. They then kill the thrust and transition to horizontal. During skydiving they have a constant acceleration from air drag keeping (Z+ direction) the gas in the header tank.

For reentry they do the deorbit burn this would settle the propellants in the header tank and put the gas ullage bubble in the header tank(X+). Now they free fall for half an orbit until reentry interface. During reentry interface they now experience acceleration but if they are nose down the ullage bubble will not necessarily go to the header because the liquid and the gas will be randomly distributed.

Solutions:
1. After deorbit burn keep small ullage thrust from RCS to keep bubble in header for the whole half an orbit(X+).
2. Just before reentry interface do a small burn(from RCS?) to settle header tank.
3. Wait till just before the flip and put the nose up for (10s?) to move the bubble to the header tank.

Is this a problem? Maybe the bubble isn't big enough to cause a problem?

Attached axis picture.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/07/2021 03:32 pm
Making the ship bigger will make it heavier but less dense. This is a good thing for aero breaking but very hard to do. It is easy to design a rocket longer but hard, Hard, HARD to make it wider. Longer is just more of the same. Wider is an entirely new design because cross section (engine space for example) scales at the square and volume (propellant capacity for example) scales at the cube. Almost every trade off needs to be rethought and every calculation redone. The result is an entirely different rocket.

I'm not a structural engineer, but I'm not sure we can assume that making the ship bigger will make it less dense.  As you mention, this is a classic example of the square-cube law at work.  To steal from the Wikipedia article on that topic, when an object is scaled up by a multiplier r, its volume and mass are increased by the cube of the multiplier while its surface area increases only by the square of said multiplier.   By rough approximation, only the surface area of Starship (the tank walls and domes) is available to resist loads, and that area grows by r-squared while mass grows by r-cubed assuming constant density.   Since most forces are proportional to mass, the loading per unit area increases by r.  To make the constant density assumption work, the average strength must increase by a factor of r; otherwise you need to add more material.

Sometimes this is not too difficult, and you might even be able to decrease density if relatively "fixed" mass can be amortized over a larger structure.  However, eventually you reach a point of diminishing returns to scale; keep going beyond that and eventually you'll exhaust the supply of stronger materials and better building techniques no matter how much extra cost you're willing to incur.

In any case, even if the constant density assumption holds, the square-cube law is still bad news for reentry.  Since surface area provides the aerodynamic drag to slow you down, the "density" you care about is surface loading (mass/area), not three-dimensional density (mass/volume).  With mass proportional to r-cubed and surface area proportional to r-squared, reentry gets harder the higher r goes.  Rocket Lab can apparently recover an Electron booster without an entry burn; the larger Falcon 9 has grid fins to increase the angle of attack during descent and provide some additional surface area for more drag but it still needs the Merlins to slow down sufficiently.  Starship has a much more heat-resistant skin and dramatically higher cross-sectional area on reentry, so it may get away without an entry burn, but that's a tougher challenge for a 12- or 18-meter Super Starship.

I don't understand how scaling up size of starships design makes reentry harder.

I'm sure the engineers can figure out the proper spaceship density and trajectory for reentry for a superwide, superlong starship launched on two or more boosters from huge stand.   

Likely be just a few years before we see it, given how fast these steel ships can be designed and built.    In fact... sadly, I bet spaceforce is working on designing a huge space battleship right now, and it might be the first one we see get launched on multiple boosters. Not a super mars cruise liner.

The amazing thing is the amount of tonnage these giant boosters are going to be able to relatively cheaply put into orbit.  Total game changer.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/07/2021 03:53 pm
I don't understand how scaling up size of starships design makes reentry harder.

I'm sure the engineers can figure out the proper spaceship density and trajectory for reentry for a superwide, superlong starship launched on two or more boosters from huge stand.   

If you don't understand, try reading the post you quoted.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 04/07/2021 03:58 pm
I don't understand how scaling up size of starships design makes reentry harder.

An extremely over-simplified version:

When you double the length parameter (length/diameter), your mass tends to go up by a factor of 8 (2 cubed) while your drag goes up by a factor of only 4 (2 squared) because mass goes with volume (cubic) and drag goes with area (quadratic/squared).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/07/2021 03:59 pm
Making the ship bigger will make it heavier but less dense. This is a good thing for aero breaking but very hard to do. It is easy to design a rocket longer but hard, Hard, HARD to make it wider. Longer is just more of the same. Wider is an entirely new design because cross section (engine space for example) scales at the square and volume (propellant capacity for example) scales at the cube. Almost every trade off needs to be rethought and every calculation redone. The result is an entirely different rocket.

I'm not a structural engineer, but I'm not sure we can assume that making the ship bigger will make it less dense.  As you mention, this is a classic example of the square-cube law at work.  To steal from the Wikipedia article on that topic, when an object is scaled up by a multiplier r, its volume and mass are increased by the cube of the multiplier while its surface area increases only by the square of said multiplier.   By rough approximation, only the surface area of Starship (the tank walls and domes) is available to resist loads, and that area grows by r-squared while mass grows by r-cubed assuming constant density.   Since most forces are proportional to mass, the loading per unit area increases by r.  To make the constant density assumption work, the average strength must increase by a factor of r; otherwise you need to add more material.

Sometimes this is not too difficult, and you might even be able to decrease density if relatively "fixed" mass can be amortized over a larger structure.  However, eventually you reach a point of diminishing returns to scale; keep going beyond that and eventually you'll exhaust the supply of stronger materials and better building techniques no matter how much extra cost you're willing to incur.

In any case, even if the constant density assumption holds, the square-cube law is still bad news for reentry.  Since surface area provides the aerodynamic drag to slow you down, the "density" you care about is surface loading (mass/area), not three-dimensional density (mass/volume).  With mass proportional to r-cubed and surface area proportional to r-squared, reentry gets harder the higher r goes.  Rocket Lab can apparently recover an Electron booster without an entry burn; the larger Falcon 9 has grid fins to increase the angle of attack during descent and provide some additional surface area for more drag but it still needs the Merlins to slow down sufficiently.  Starship has a much more heat-resistant skin and dramatically higher cross-sectional area on reentry, so it may get away without an entry burn, but that's a tougher challenge for a 12- or 18-meter Super Starship.

I don't understand how scaling up size of starships design makes reentry harder.

I'm sure the engineers can figure out the proper spaceship density and trajectory for reentry for a superwide, superlong starship launched on two or more boosters from huge stand.   

Likely be just a few years before we see it, given how fast these steel ships can be designed and built.    In fact... sadly, I bet spaceforce is working on designing a huge space battleship right now, and it might be the first one we see get launched on multiple boosters. Not a super mars cruise liner.

The amazing thing is the amount of tonnage these giant boosters are going to be able to relatively cheaply put into orbit.  Total game changer.

Part of the etiquette here is learning that we try to stay on topic.  Nothing much of what you have discussed on this Prototypes thread has anything to do with these Prototypes.  There are dozens of topics which might house such a discussion and you are free to create new ones trying to frame an interesting topic.

But when you start drifting into nonsense like Space Force battleships, you need to shut it down here.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/07/2021 04:01 pm
So if SN20+ are supposed to be orbital, do we know if SN15-16 are going to aim for the same altitude as SN8-11, or something in between 10km and orbit?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/07/2021 04:04 pm
So if SN20+ are supposed to be orbital, do we know if SN15-16 are going to aim for the same altitude as SN8-11, or something in between 10km and orbit?
I have a feeling that they could actually go the same SN8-11 altitude on SN15-17, and then shoot straight for orbit at SN20+ because of Elon's wording of "need many attempts to survived Mach 25". And the current license limited them to no higher than 18 miles
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Danderman on 04/07/2021 04:27 pm
Probably many people have mentioned this, but there may be a reason that methane rocket engines are rare, there may be problems in the technology that are difficult to overcome.  And the engines are so rare, there is not a great experience base to lean on.

Since Starships carry separate prop tanks for landing, it may be necessary to add Merlin engines for landing.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/07/2021 04:27 pm
Sorry for taking us off topic, by discussing horizontal landing, and thicker hulled larger ships.

I was just thinking way ahead how a starship could land and takeoff on a rocky, maybe frozen surface, to be closer to water for refueling, planet vertically.   Without making large craters and blowing shrapnel directly at the engine bay and brittle heat shielding up one side.

  Landing on mars horizontally and vectoring thrust and debris to sides away from ship would be one solution that would be easier, and more stable to unload huge cargo.

Truth is, there are many solutions to any problem.  No reason why they couldn't drop robots to clear a nice huge flat rock into some kind of working landing pad.

I also thought, thicker metal hull of larger ship would mean less radiation problems in space, less heat problems on reentry, less worry about shrapnel or space debris piercing hull.  But I'm no rocket scientist, so I will stop speculating on what comes next, years from now.   

Just glad I can watch the show, and its finally happening, after years of nasa's sloth approach to progress.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 04/07/2021 04:29 pm
Probably many people have mentioned this, but there may be a reason that methane rocket engines are rare, there may be problems in the technology that are difficult to overcome.  And the engines are so rare, there is not a great experience base to lean on.

Since Starships carry separate prop tanks for landing, it may be necessary to add Merlin engines for landing.

Adding an entirely separate fuel type and the associated GSE is definitely not the solution to that problem.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: llanitedave on 04/07/2021 05:05 pm
Probably many people have mentioned this, but there may be a reason that methane rocket engines are rare, there may be problems in the technology that are difficult to overcome.  And the engines are so rare, there is not a great experience base to lean on.

Since Starships carry separate prop tanks for landing, it may be necessary to add Merlin engines for landing.


Maybe many people have, but I don't recall anyone who actually understands the engineering recommending it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/07/2021 05:06 pm
Probably many people have mentioned this, but there may be a reason that methane rocket engines are rare, there may be problems in the technology that are difficult to overcome.  And the engines are so rare, there is not a great experience base to lean on.

Since Starships carry separate prop tanks for landing, it may be necessary to add Merlin engines for landing.



Nah, no “problems in the technology.” It’s pure economics. Kerolox and hypergolics are simpler and offer lots of thrust for minimal technological complexity and maximal energy density. This is important for disposable booster stages and ICBM’s. For upper stages where ISP is king, hydrolox offers the best there is for chemical rockets provided you don’t need to worry about density all that much (so long as large tank volumes are not a constraint) and if you don’t care much about storability and boil-off rates. Once you change your paradigm to reusability, storability and (ideally) ISRU, methalox suddenly makes a hell of a lot of sense.

However, commercially-viable reusability has only been a serious focus for a relative handful of years. No serious research has been done toward methalox engines of the type and scale being built by SpaceX and Blue until now. This is literally how R&d works in practice.

And we are very much off-topic now for this thread so I’ll stop.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/07/2021 05:27 pm
Lunar starship will not be returning for a landing on earth, no heat shield or flaps. So lunar SS is irrelevant in regards to landing skydive mode and flip...
hkultala asked what thrusters, and I answered him. If they wanted to, they could just use the lunar Starship’s thrusters (with truncated nozzles for use near sea level).

I wasn’t making a prediction, just answering his question.

Or was it just a hypothetical question which he assumed had no feasible answer? ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 04/07/2021 05:47 pm
Lunar starship will not be returning for a landing on earth, no heat shield or flaps. So lunar SS is irrelevant in regards to landing skydive mode and flip...
hkultala asked what thrusters, and I answered him. If they wanted to, they could just use the lunar Starship’s thrusters (with truncated nozzles for use near sea level).

I wasn’t making a prediction, just answering his question.

Or was it just a hypothetical question which he assumed had no feasible answer? ;)
If I were Jeff Bezos, declaring a mission plan to BO to copy starship "they way it should have been" for NA, I'm thinking upper hull landing thrusters like lunar starship, but with deployable nozzle extensions that, when retracted, are a flush part of the heat shield. Solves the "open nozzle exposed to reentry" problem and gives a few extra points of ISP for the trouble.

But Starship itself is still looking like they're going to try a pure tail landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/07/2021 07:04 pm
An interesting question about reentry profile which doesn't apply to the 10km tests they are doing.

For the 10km test they transition to header tanks while they have thrust in the vertical position(X+ direction). This will cause all ullage gas to be in the header tank. They then kill the thrust and transition to horizontal. During skydiving they have a constant acceleration from air drag keeping (Z+ direction) the gas in the header tank.

For reentry they do the deorbit burn this would settle the propellants in the header tank and put the gas ullage bubble in the header tank(X+). Now they free fall for half an orbit until reentry interface. During reentry interface they now experience acceleration but if they are nose down the ullage bubble will not necessarily go to the header because the liquid and the gas will be randomly distributed.

Solutions:
1. After deorbit burn keep small ullage thrust from RCS to keep bubble in header for the whole half an orbit(X+).
2. Just before reentry interface do a small burn(from RCS?) to settle header tank.
3. Wait till just before the flip and put the nose up for (10s?) to move the bubble to the header tank.

Is this a problem? Maybe the bubble isn't big enough to cause a problem?

Attached axis picture.
Yes this is a problem. Putting the nose up for 10 seconds will ensure that Starship is traveling much faster in the same way that a sky diver falls much faster in a tuck than with arms and legs stretched out. This will involve firing up the Raptors significantly longer using more propellent. And minimising propellant use is the name of the game here.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bkent136 on 04/07/2021 07:12 pm
Probably many people have mentioned this, but there may be a reason that methane rocket engines are rare, there may be problems in the technology that are difficult to overcome.  And the engines are so rare, there is not a great experience base to lean on.

Since Starships carry separate prop tanks for landing, it may be necessary to add Merlin engines for landing.
It has nothing to do with the propellant used, but instead the flip maneuver at the end that begins by lighting up a full flow staged combustion cycle engine (actually 3) in freefall in the horizontal position. While Merlins are inherently simpler gas generator cycle engines, it's still likely they would suffer from the same issues in propellant feed instability and the bubbles that result in sloshing. This suggestion is short sighted at best.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/07/2021 07:16 pm
I don't understand how scaling up size of starships design makes reentry harder.

An extremely over-simplified version:

When you double the length parameter (length/diameter), your mass tends to go up by a factor of 8 (2 cubed) while your drag goes up by a factor of only 4 (2 squared) because mass goes with volume (cubic) and drag goes with area (quadratic/squared).

Thanks for the simplified version.  I am a total space dummy, never studied this stuff.

Hate to ask.   Trying to figure out in my head how this stuff works. But can you also give me a simple explanation why less drag on reentry is a bad thing?  Wouldn't less drag be less heat to deal with on reentry? Which I (maybe mistakenly) think is the hardest problem to solve, when it comes to reusability. 

 I also (maybe mistakenly) think starship is designed to fly across atmosphere like space shuttles, and burn off speed that way, before entering the stall, skydive maneuver.  

 So while a larger starship would be much heavier on takeoff. (Needing two or more boosters)  When it comes back to land,  it will be much lighter relative to its size, as fuel weight is almost empty. So a bigger starship would have more drag in freefall in that mode, with empty tanks, and empty cargo.    As cargo is in space or back on mars. 

So in my mind,  we would be talking about two different types of drag which gets a bit complicated to me.  Frontalish drag, when starship is piercing atmosphere and slowing down, and then super high drag of skydive mode. 

 Less drag to me, would mean they would fly in shuttle mode a bit further to shed speed, before entering stall and into skydive mode for final landing.  

Unless, I'm completely mistaken, and this thing is designed to come into the atmosphere in skydive mode, and doesn't fly at all like a shuttle.     Which makes me a real dummy.

  But again, having no cargo, and almost no fuel, should be relatively light for its bigger size.  Yet it would have a stiffer stronger hull, which bodes well for reusability in my mind.

Don't be shy to tell me if I'm completely off base. Like I said. Total space dummy here.  :) 

 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 04/07/2021 07:26 pm
I also (maybe mistakenly) think starship is designed to fly across atmosphere like space shuttles, and burn off speed that way, before entering the stall, skydive maneuver. 
As far as I understand, it is never expected to fly aerodynamically like the shuttle, it's doing a skydiver bellyflop the whole way down, it's just that the axis of the belly-flop changes more and more downwards as the horizontal speed relative to the air drops. 

I don't think it's belly-flopping at a full 90 degrees up high (and I'm not sure why) because I think I read it was something like  a ~70 degree sky-diver maneuver, but that asymmetric high-drag entry is probably the closest to looking space-shuttle-y I've seen in any of the renders.

But anyways, in short it's doing the skydiver/belly drop the whole way in I think.  The brakerons just LOOK like wings/canards, but they're just brakes.

Here's hoping I didn't pooch this up too much.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/07/2021 07:28 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: awests on 04/07/2021 07:32 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
The Hol(e)y dome! Impressive piece they’ve got there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/07/2021 07:36 pm
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
The Hol(e)y dome! Impressive piece they’ve got there.

Wow! I guess that's for BN3?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/07/2021 07:36 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
The Hol(e)y dome! Impressive piece they’ve got there.

I've been trying to think about what the thrust dome of a 28 engine BN would look like for at least a year now, I did not imagine this!  Amazing photo of amazing work.

So many internal stringers and the reinforcements around the inlets.  It's beautiful!

Can't wait to see how they load it to test the completed vehicle.

This looks like it could really work and get the job done!

The total amount of welding, oh my!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: awests on 04/07/2021 07:45 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
The Hol(e)y dome! Impressive piece they’ve got there.

I've been trying to think about what the thrust dome of a 28 engine BN would look like for at least a year now, I did not imagine this!  Amazing photo of amazing work.

So many internal stringers and the reinforcements around the inlets.  It's beautiful!

Can't wait to see how they load it to test the completed vehicle.

This looks like it could really work and get the job done!

The total amount of welding, oh my!
I want to see the stainless spaghetti plumbing when they flip it!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Curriston on 04/07/2021 08:17 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: maquinsa on 04/07/2021 08:17 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?

The twentyweb?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Miranoff on 04/07/2021 08:22 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?

The twentyweb?

The VentiWeb!

hang a starbucks sign on it for corporate sponsorship or something.

What an amazing piece of engineering that is.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 04/07/2021 08:27 pm
It does not look cheap to make.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: plehrack on 04/07/2021 08:34 pm
For the "flip with hot gas thrusters" fans... Which is more efficent?

A separate thruster system burning the same propellant as autogen gasses, to stabilize the rocket vertical before lighting the main raptors...

Or dumping the same hot gas directly into the header tanks to counter ullage collapse, and let the "gas bubbles" get sucked up and condense back into propellant in the fuel lines?

The problems with the Helium system are a red herring. we want to get RID of the helium system. That means dealing with the Ullage collapse problem.

The hot gas thrusters are part of the final design, I'm just suggesting replacing them until they are ready for integration with an array of CGTs or Super Dracos. Elon inferred that the HGTs can do the job but the Raptors are more efficient at it. We'll see what they decide to do, hopefully SN Gen2 will work the current issues out and it'll be a moot point.

Peter
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/07/2021 08:47 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?

The twentyweb?

Icosaweb
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nascent Ascent on 04/07/2021 08:48 pm
Wow. Elon might want to order one of those huge casting machines to make that part. Awesome.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/07/2021 08:50 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?

So whats the other 20 port thingy for? There appears to be 2 of them. Is this one just more complete?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacevalley27 on 04/07/2021 08:52 pm
Are there any theories on what this thrust dome might be used for?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KilroySmith on 04/07/2021 08:52 pm
OMG.  That dome is amazing.

I immediately noticed that the holes don't match nicely with the gores / panels in the dome.  It appears that there are 4 holes for every three panels, seems like it might simplify things to make the panels slightly smaller so they're identical with a hole in the middle of each, or larger so they're identical with two holes in each.  The hole cutting/welding could then be done on flat panels (or at least on individual panels) rather than on the dome as a whole - of course, maybe they do that, and just accept that there are three different panels. 

Anyone else want to see what the bottom side of that looks like?

Fascinating.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/07/2021 08:53 pm
So whats the other 20 port thingy for? There appears to be 2 of them. Is this one just more complete?

It looks to me like this one is an early production pathfinder.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hkultala on 04/07/2021 08:57 pm
For the "flip with hot gas thrusters" fans... Which is more efficent?

A separate thruster system burning the same propellant as autogen gasses, to stabilize the rocket vertical before lighting the main raptors...

Or dumping the same hot gas directly into the header tanks to counter ullage collapse, and let the "gas bubbles" get sucked up and condense back into propellant in the fuel lines?

The problems with the Helium system are a red herring. we want to get RID of the helium system. That means dealing with the Ullage collapse problem.

The hot gas thrusters are part of the final design, I'm just suggesting replacing them until they are ready for integration with an array of CGTs or Super Dracos. Elon inferred that the HGTs can do the job but the Raptors are more efficient at it. We'll see what they decide to do, hopefully SN Gen2 will work the current issues out and it'll be a moot point.

Peter

The hot gas orbital maneuvering thrusters that are part of the final design are not strong enough.

And the strong hot gas thrusters of the moon lander starship are not part of the normal starship design.

And Superdracoes use totally different (and toxic) fuels, would need another set of tanks and would complicate things a lot AND would make all handling of the starship much more dangerous and expensive. They really don't want to have hydrozine flying around when their starship crashes.

And no sane amount of cold gas thrusters have enough thrust either.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/07/2021 08:59 pm
For the "flip with hot gas thrusters" fans... Which is more efficent?

A separate thruster system burning the same propellant as autogen gasses, to stabilize the rocket vertical before lighting the main raptors...

Or dumping the same hot gas directly into the header tanks to counter ullage collapse, and let the "gas bubbles" get sucked up and condense back into propellant in the fuel lines?

The problems with the Helium system are a red herring. we want to get RID of the helium system. That means dealing with the Ullage collapse problem.

The hot gas thrusters are part of the final design, I'm just suggesting replacing them until they are ready for integration with an array of CGTs or Super Dracos. Elon inferred that the HGTs can do the job but the Raptors are more efficient at it. We'll see what they decide to do, hopefully SN Gen2 will work the current issues out and it'll be a moot point.

Peter

The hot gas orbital maneuvering thrusters that are part of the final design are not strong enough.

And the strong hot gas thrusters of the moon lander starship are not part of the normal starship design.

And Superdracoes use totally different (and toxic) fuels, would need another set of tanks and would complicate things a lot AND would make all handling of the starship much more dangerous and expensive. They really don't want to have hydrozine flying around when their starship crashes.

And no sane amount of cold gas thrusters have enough thrust either.

They may use HGT(hot gas thrusters) while in the skydive mode to settle propellants and they fire the raptors for the flip.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: enbandi on 04/07/2021 09:07 pm
Are there any theories on what this thrust dome might be used for?

My guess is that a scrap/obsolete version of the dome, used for practice/development purposes. Hint: the 40+ cutouts for the Superheavy thrust puck, but chunks for only 3 Raptors in the middle (StarShip specific).

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/07/2021 09:19 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?
That's my guess.  There's nothing that looks even close to engine mounts for the outer engines - just plumbing feed-throughs.  Also, while I think its expected the centre engines may be a bit lower that the outer ring, I think the vertical offset as it is points to an additional thrust structure tied the the outer skin onto which the outer 20 Raptors will be mounted.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Crispy on 04/07/2021 09:25 pm
It reminds me of the indian pastiche of Brighton Pavillion

I *really* want to see what the other side looks like.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/07/2021 09:44 pm
It does not look cheap to make.
Probably pretty cheap per unit thrust!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/07/2021 09:45 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?
That's my guess.  There's nothing that looks even close to engine mounts for the outer engines - just plumbing feed-throughs.  Also, while I think its expected the centre engines may be a bit lower that the outer ring, I think the vertical offset as it is points to an additional thrust structure tied the the outer skin onto which the outer 20 Raptors will be mounted.
We have already seen the outer engine mounts on BN1. Also, IIRC when they lifted BN1 thrust section on the big stand the engine mounts appeared to be at the same level.

Photo of the BN1 thrust section from @RGVAerialPhotography.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WormPicker959 on 04/07/2021 09:45 pm
It reminds me of the indian pastiche of Brighton Pavillion

I *really* want to see what the other side looks like.

Strange downcomers though.


Image Credit: NOT Mary. (Some bloke named Jim Holden/Alamy)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/07/2021 10:02 pm
They may use HGT(hot gas thrusters) while in the skydive mode to settle propellants and they fire the raptors for the flip.

I thought we were all in agreement that props were naturally settled during skydive mode since SS isn't in freefall?  Do you mean to add a HGT component to push props toward the rear?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/07/2021 10:03 pm
It does not look cheap to make.
Probably pretty cheap per unit thrust!

If there was ever a part that was begging to be welded by robots, the BN thrust dome would be it!

Edit: Who knows how many flights or BNs get built before they go for orbit.  But I can not wait to see this fly, and I'm willing to bet the first orbital attempt is built to have more thrust than the Saturn V.  (That's just good marketing)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Niklas Holsti on 04/07/2021 10:06 pm

I don't think it's belly-flopping at a full 90 degrees up high (and I'm not sure why) because I think I read it was something like  a ~70 degree sky-diver maneuver, but that asymmetric high-drag entry is probably the closest to looking space-shuttle-y I've seen in any of the renders.


I believe SpaceX have said that the 70-degree phase aims to get enough lift from the cylindrical body and the flaps to keep the Starship in the high, thin part of the atmosphere for a while, which limits the deceleration and heating. If they let the ship fall deeper, while still going very fast, both the deceleration and the heating would be much more stressful.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/07/2021 10:18 pm
Wow. Elon might want to order one of those huge casting machines to make that part. Awesome.
Won’t work with stainless steel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/07/2021 10:26 pm
They may use HGT(hot gas thrusters) while in the skydive mode to settle propellants and they fire the raptors for the flip.

I thought we were all in agreement that props were naturally settled during skydive mode since SS isn't in freefall?  Do you mean to add a HGT component to push props toward the rear?

I meant additional settling g's to move the bubbles to the front. Before reentry interface the rocket is zero g. Probably a brief period of 5-10 deg rear down during the skydive will move bubbles to the front. Why not a little additional settling g's from RCS.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Proesterchen on 04/07/2021 10:41 pm
I wonder if that forward dome being advanced to SN20 means that the SN15+ series has been found to be fundamentally flawed and is being relegated to proving the new puck design.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/07/2021 11:09 pm
I wonder if that forward dome being advanced to SN20 means that the SN15+ series has been found to be fundamentally flawed and is being relegated to proving the new puck design.
Too early to give conclusion. It's what production looks like, adding components in advance
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 04/08/2021 12:19 am
It does not look cheap to make.
Probably pretty cheap per unit thrust!

If there was ever a part that was begging to be welded by robots, the BN thrust dome would be it!

Edit: Who knows how many flights or BNs get built before they go for orbit.  But I can not wait to see this fly, and I'm willing to bet the first orbital attempt is built to have more thrust than the Saturn V.  (That's just good marketing)

It looks like that stand is set up for robotic welding and (hole) cutting.

The top ring, which the dome rests on, is on a series of rollers and, in the centre of the image, you can see the drive motor to spin it on the rest of the base.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 04/08/2021 02:04 am
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?
Wondering if the thrust dome only supports the center 8 engines and the outside ring is supported by some sort of Octoweb design like on the Falcon 9? No idea what they might call a web structure that supports 20 engines?
That's my guess.  There's nothing that looks even close to engine mounts for the outer engines - just plumbing feed-throughs.  Also, while I think its expected the centre engines may be a bit lower that the outer ring, I think the vertical offset as it is points to an additional thrust structure tied the the outer skin onto which the outer 20 Raptors will be mounted.
We have already seen the outer engine mounts on BN1. Also, IIRC when they lifted BN1 thrust section on the big stand the engine mounts appeared to be at the same level.

Photo of the BN1 thrust section from @RGVAerialPhotography.
 
 
BN1 is obsolete. I wouldn't base much on it anymore.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wagner on 04/08/2021 03:18 am
I also (maybe mistakenly) think starship is designed to fly across atmosphere like space shuttles, and burn off speed that way, before entering the stall, skydive maneuver. 
I don't think it's belly-flopping at a full 90 degrees up high (and I'm not sure why) because I think I read it was something like  a ~70 degree sky-diver maneuver, but that asymmetric high-drag entry is probably the closest to looking space-shuttle-y I've seen in any of the renders.
If you're just dropping at 90°, that's a fairly high G ballistic entry.  Even capsules "fly" a bit by coming in edge on.  It also allows you to adjust where you land, which is pretty critical if you're supposed to land on a pad, or in the welcoming arms of a gigantic crane.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thundermusicz on 04/08/2021 03:54 am
I also (maybe mistakenly) think starship is designed to fly across atmosphere like space shuttles, and burn off speed that way, before entering the stall, skydive maneuver. 
I don't think it's belly-flopping at a full 90 degrees up high (and I'm not sure why) because I think I read it was something like  a ~70 degree sky-diver maneuver, but that asymmetric high-drag entry is probably the closest to looking space-shuttle-y I've seen in any of the renders.
If you're just dropping at 90°, that's a fairly high G ballistic entry.  Even capsules "fly" a bit by coming in edge on.  It also allows you to adjust where you land, which is pretty critical if you're supposed to land on a pad, or in the welcoming arms of a gigantic crane.
I recall a tweet from Elon saying that Starship would have a 70 degree AoA (Angle of Attack), meaning the vehicle will be at 70 degrees to the oncoming airstream (for reference, the belly flop is 90 deg AoA as it falls vertically). So its not quite straight head on, but also not quite like Shuttle which was 30 deg AoA. So getting high surface area, but also using its fuselage as a lifting body to stay higher in the atmosphere longer.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barnalby on 04/08/2021 04:52 am
They should really add B-2 style split flaps to the trailing edges of the rear fins so that Starship can adjust pitch, roll, and yaw aerodynamically on reentry.

And while they're at it, they could just add wheeled landing gear that deploy through the heat shield so that it could- HEY!  WAIT A SECOND...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thundermusicz on 04/08/2021 06:07 am
They should really add B-2 style split flaps to the trailing edges of the rear fins so that Starship can adjust pitch, roll, and yaw aerodynamically on reentry.
Can't they already control pitch, roll, and yaw with the 4 existing flaps? I'm pretty sure that's one of the tests they did with SN11 that was difficult to pick up on because of the fog, but it definitely looked like they were doing some funky maneuvering.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 04/08/2021 07:25 am
@fael97 did you make any blueprint for the plumbing of starship with R-Vac with the new puck design [https://pbs.twimg.com/media/EmF_Gr0XIAERTJk?format=jpg&name=4096x4096]? [Credit: Rafael's Twitter]

I asked as I'm wondering why is SpaceX following the design of the old puck from Starship on SuperHeavy which had all the CH4 plumbing inside the LOX tank. I'm aware of tank alteration on SuperHeavy but again it'll be now LOX plumbing inside the CH4 tank. Then, I thought maybe they have just moved the plumbing outside for sea level Raptors and not the R-Vacs on Starship
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 04/08/2021 09:04 am
I wonder if that forward dome being advanced to SN20 means that the SN15+ series has been found to be fundamentally flawed and is being relegated to proving the new puck design.
As planned. the SN8 block was never indended to land, it was only intended to prove descent with brakerons was controllable. They nailed that on the first try, so they got a head start on the controls needed for SN15 block (landing) prototypes using the obsolete SN8-block hardware. The SN20 block will be Entry pathfinders, and also functional orbital spacecraft that can pay their own way.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/08/2021 03:31 pm
Did the previous series of SNs have stringers just above the top dome?  I don't recall seeing the weld marks there before.  Also, this is right where I recall seeing the nose crumple from a slow-mo screen grab of SN10's relaunch after landing.

Image credit: BCG's recent post on the updates thread
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/08/2021 03:37 pm
Did the previous series of SNs have stringers just above the top dome?  I don't recall seeing the weld marks there before.  Also, this is right where I recall seeing the nose crumple from a slow-mo screen grab of SN10's relaunch after landing.

Image credit: BCG's recent post on the updates thread

The crumple was up near the cone. Not down near the top dome.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barnalby on 04/08/2021 03:43 pm
It also appears that they're adding a nosecone to the noseless test jig article.  I'll lose it if it ends up being made out of reinforced carbon-carbon.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 04/08/2021 03:45 pm
Did the previous series of SNs have stringers just above the top dome?  I don't recall seeing the weld marks there before.  Also, this is right where I recall seeing the nose crumple from a slow-mo screen grab of SN10's relaunch after landing.

Image credit: BCG's recent post on the updates thread

The crumple was up near the cone. Not down near the top dome.

I believe that they had stringers in the cylindrical portion of the payload bay but none in the nose cone section.

John
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/08/2021 04:30 pm
FrankX, most of what you want to learn can be gleaned from the other threads in this forum, like the General Engineering thread, the trajectory thread, etc. This one is for the the actual (current and as they are being built/flown/destroyed) Texas Prototypes.

*****
Speaking of which, holy crap, look at this booster thrust dome posted today by Mary! :O This is the first one we’ve seen with provisions for all 28 engines isn’t it?

Thanks, I did just that, read a few threads, and gleaned I'm on the right path with my thinking.  Larger ship coming in low on fuel and cargo, should be easier on reentry than a smaller ship.  Due to most of the volume weight of the larger ship being fuel and cargo.   They are intending on flying this thing in upper atmosphere long as possible to bleed of speed, before entering slow skydive mode as I thought.  So larger ship on multiple boosters would get a lot more tonnage to space, and should be easier to get back in one piece, win win.

But there is no reason to make larger ships or boosters from the get go for development, which is likely why Elon shrunk the diameter from initial 12m to 9m.     Easier to mass produce 9m boosters quickly. Then later, if need be ,put multiple boosters under larger starships.   What a sight that would be!

But I've derailed this thread enough. 



HOLY DRUM... that thing will see some serious vibration!   Really impresses me that a person can almost fit down those fuel line openings.   These raptors are not gas sippers, that is for sure!

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/08/2021 04:38 pm
Took Nomadd’s photo and touched up the brightness on the skirt area. Obviously no raptors, but just worth checking  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/08/2021 04:45 pm
Lunar starship will not be returning for a landing on earth, no heat shield or flaps. So lunar SS is irrelevant in regards to landing skydive mode and flip...
hkultala asked what thrusters, and I answered him. If they wanted to, they could just use the lunar Starship’s thrusters (with truncated nozzles for use near sea level).

I wasn’t making a prediction, just answering his question.

Or was it just a hypothetical question which he assumed had no feasible answer? ;)
If I were Jeff Bezos, declaring a mission plan to BO to copy starship "they way it should have been" for NA, I'm thinking upper hull landing thrusters like lunar starship, but with deployable nozzle extensions that, when retracted, are a flush part of the heat shield. Solves the "open nozzle exposed to reentry" problem and gives a few extra points of ISP for the trouble.

But Starship itself is still looking like they're going to try a pure tail landing.

With this starship design, no reason to put anything on heats shield side.  That just complicates things.   Heatshield side needs to be clean as possible, and well insulated. No doors if possible. 

But there is nothing stopping them from putting thrusters, and landing gear on stainless side.    Come in atmosphere on heatshield side, then once thru the heat, do gentle 180 roll into skydive mode.  Ship can skydive either way.    That gives propellant plenty of time to settle, as no last minute flip maneuver.  Just fire thrusters , lower landing gear from stainless side and land.

   But the thrusters would have to have serious power, like 4 mini quarter size raptors to pull off horizontal landing.      Of course on moon and mars, landing is much easier, lower gravity.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GetCrispy on 04/08/2021 04:59 pm
Ship can skydive either way.

It can only skydive with the heatshield down. The flaps don't have the same range of motion in the other direction, and the area where the flap meets the fuselage is different on top than on the bottom.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/08/2021 05:26 pm
Ship can skydive either way.

It can only skydive with the heatshield down. The flaps don't have the same range of motion in the other direction, and the area where the flap meets the fuselage is different on top than on the bottom.


Yes, on current ship.  But a horizontal landing ship would be a total upgrade redesign with flap range in both directions.

    BTW- was just commenting on the Bezos, copying starship design post above.

But starship design copiers would run into trouble quickly trying to work out horizontal landing first.    First, raptor type fuel design, thrust, and precise throttling needs to be worked out. Before adding multiple axis vertical landing.

So Elons approach of developing vertical landing first, on mostly thrust of single engine is likely best.  Got to walk before you can run.   Then shrink raptors design down to bad ass thrusters, using same fuel as raptor.

In any case... future is looking pretty cool!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/08/2021 05:30 pm
and how heat shielding of the hinge of 180 deg capable flap is going to be design?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: HVM on 04/08/2021 05:48 pm
and how heat shielding of the hinge of 180 deg capable flap is going to be design?
I would add the tweet or image of SpaceXers taking pictures of shuttle TPS near flight surfaces here... (If I would find it)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FrankX on 04/08/2021 05:51 pm
and how heat shielding of the hinge of 180 deg capable flap is going to be design?

Its a challenge for sure, but so is sealing the current design.   But to do both entry and skydive maneuver, flaps don't need to be on centerline of ship.   They can be much lower, like on planes, and hinge further away from heat on reentry, as its behind curvature of heat shielding.    They also likely don't need full 180 motion to do roll, or skydive. Flaps having to fold all the way back is more for flip maneuver.

 But all that will be worked out with current design prototypes.

Just like everything else, we will likely see many redesigns on heat shields and flaps before they get it right.  This is how you make progress.  You try stuff out... see what works, and what doesn't makes fireworks.    I love this rapid style of progress!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nescio Erucis on 04/08/2021 06:35 pm
It also appears that they're adding a nosecone to the noseless test jig article.  I'll lose it if it ends up being made out of reinforced carbon-carbon.
Doesn't look like stainless, anyway.
https://forum.nasaspaceflight.com/index.php?topic=52398.msg2217561#msg2217561
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/08/2021 06:41 pm
They may use HGT(hot gas thrusters) while in the skydive mode to settle propellants and they fire the raptors for the flip.

I thought we were all in agreement that props were naturally settled during skydive mode since SS isn't in freefall?  Do you mean to add a HGT component to push props toward the rear?

I meant additional settling g's to move the bubbles to the front. Before reentry interface the rocket is zero g. Probably a brief period of 5-10 deg rear down during the skydive will move bubbles to the front. Why not a little additional settling g's from RCS.
Yes! Ease into the flip instead of slamming into it. Keep that slosh down. Burning a bit more props is better than playing lawn dart. Might also help if they can work the flaps and RCS to put the center of rotation as close to the fuel header as possible.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/08/2021 07:44 pm
You can see that black nose cone tip on the ground in front of the stand on Mary's photo. Hopefully there's gonna be better photos later. :)

https://twitter.com/BocaChicaGal/status/1380172626870603780
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/08/2021 08:04 pm
This is: "Texas Prototype(s) Thread 20 : Discussion" so there should be discussion only about starship and superheavy existing prototypes
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CruddyCuber on 04/08/2021 08:11 pm
You can see that black nose cone tip on the ground in front of the stand on Mary's photo. Hopefully there's gonna be better photos later. :)

https://twitter.com/BocaChicaGal/status/1380172626870603780

Here it is up close and circled for anyone having trouble spotting it like me.

Image credit:  Bocachicagal
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 04/08/2021 08:13 pm
I see people completely missed my statement earlier.

You dont need to prevent slosh if you dont have a helium system.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/08/2021 08:14 pm
and there is plenty of threads where wild speculation of how to redesign SS is allowed.
star ship landing legs. Very speculative. (because we don't have any yet)
https://forum.nasaspaceflight.com/index.php?topic=51518.0
Off topic discussions
https://forum.nasaspaceflight.com/index.php?topic=51518.0

just to name a few.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/08/2021 08:15 pm
Forgive me, I thought this was a mars starship discussion thread.  Not an 'update' thread.  So thought discussing how they might later optimize mars starship , just for mars gravity, be relevant.   Not sure why, but seems I may have frakked off a few here, so will stop. 

Didn't mean to piss in anyone's cheerios.

You aren't frakking anyone off or pissing in anyone's cheerios.  You are failing to observe and respect the manner in which NSF operates.

You don't have to "think" about what this thread is for.  The first post tells you what it is for:

New thread (20) for discussion of the Starship prototype being built in Boca Chica, Texas
---

RULES

There are 10s of millions of views on these Starship threads, so remember when you post your post is being viewed by a lot of people. Make sure you're posting something interesting:

Stay on topic (don't wander, use new or other threads). This is ONLY about discussing the prototypes
Make sure your post is useful and adding something. Failure to do so will see your post removed.

some emphasis mine.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/08/2021 08:15 pm
BTW-  In future, might not even be reason giant stronger/safer mars starship needing to return all the way to earth.  It just needs to return to earth orbit, where it can dock with a space station, be reloaded, refueled.  Returning people can use capsules or other smaller vehicles made just for reentry.

   Solving all reentry problems for a big mars cruiser.   To me, the key to Musks whole program is how much tonnage these giant boosters can get into space.    I can just imagine what multiple bolted together boosters can lift.   They will be able to build one huge space station quickly for sure.   Sci'fi future is almost here.

Think you might want to take that discussion to the  "I risk sending a thread off topic" Homeless Posts Thread (https://forum.nasaspaceflight.com/index.php?topic=51518.0) as what you are proposing is a fundamental change in the architecture and conops for SS-Mars, unrelated to this thread (actual stuff in progress).

In particular, your suggestion of "one huge space station"--and the implications thereof (such as Mars return to LEO)--are way off topic as it has no relevance to this thread "SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion".

Or start your own thread--but be warned the variations you suggest have been previously discussed at length, so expect pushback unless you are bringing something new to the table.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/08/2021 08:19 pm
Those 3 thingies on new black nose tip looks like markers for precise optical tracking

https://twitter.com/news_starship/status/1380250354042990602
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/08/2021 08:19 pm
You can see that black nose cone tip on the ground in front of the stand on Mary's photo. Hopefully there's gonna be better photos later. :)

https://twitter.com/BocaChicaGal/status/1380172626870603780

Here it is up close and circled for anyone having trouble spotting it like me.

Image credit:  Bocachicagal

Is that a docking adapter mockup for a lunar Starship?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/08/2021 08:26 pm
...
You dont need to prevent slosh if you dont have a helium system.
Trying to parse that double negative... Apologies for being pedantic, but I read that as "you need to prevent slosh if you have a helium system"?  Which makes no sense.  Please explicate.  Thanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dondar on 04/08/2021 08:28 pm
the black cone looks to have serious crane hinge system (for 150m super-crane obviously) +service entrance for personnel. The colour is peculiar. it looks likes to be made from metal free carbon-fiber. It can be a radome beside above mentioned things.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Remes on 04/08/2021 08:40 pm
I see people completely missed my statement earlier.

You dont need to prevent slosh if you dont have a helium system.

You need slosh baffles in order to avoid hundreds of tons of propellant to press against the wall back and forth. Regardless how you pressurize the tanks. Your previous post is simply not correct.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/08/2021 08:42 pm
It looks like painted steel to me, but who am I to judge...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 04/08/2021 08:42 pm
The black cap appears to be a load cap, made from steel, likely to tension up the nose in the structural test stand. No flight article...

My 2c
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/08/2021 08:44 pm
Another possibility - could NASA have said "you *must* have a launch escape system to get crew rated for any of our missions"?

Is it possible that this is a dummy for a crew capsule to sit on the top with super dracos in case it all goes tits up?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/08/2021 08:46 pm
Those 3 thingies on new black nose tip looks like markers for precise optical tracking

https://twitter.com/news_starship/status/1380250354042990602
This looks a bit like a docking mockup/prototype to me.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/08/2021 08:46 pm
The black cap appears to be a load cap, made from steel, likely to tension up the nose in the structural test stand. No flight article...

My 2c

and those markers for optical tracking are likely to measure displacement
now everything starts to make sense
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/08/2021 08:47 pm
Another possibility - could NASA have said "you *must* have a launch escape system to get crew rated for any of our missions"?

Is it possible that this is a dummy for a crew capsule to sit on the top with super dracos in case it all goes tits up?

No.  Anything in that regard would be premature at this point.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CardBoardBoxProcessor on 04/08/2021 08:51 pm
New black fixture on nose of tipless nose cone further supports theory this is a heatshield  attachment jig device.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 04/08/2021 09:07 pm
...
You dont need to prevent slosh if you dont have a helium system.
Trying to parse that double negative... Apologies for being pedantic, but I read that as "you need to prevent slosh if you have a helium system"?  Which makes no sense.  Please explicate.  Thanks.
The helium presurization system they installed in SN9 and SN10 were the cause of the "bubble injestion" problems. SN8 didnt have any problems starting up or running through the flip, but it had fuel pressure problems because all the bubbles turned back into fuel instead of pressurizing the fuel tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CruddyCuber on 04/08/2021 09:13 pm
...
You dont need to prevent slosh if you dont have a helium system.
Trying to parse that double negative... Apologies for being pedantic, but I read that as "you need to prevent slosh if you have a helium system"?  Which makes no sense.  Please explicate.  Thanks.
The helium presurization system they installed in SN9 and SN10 were the cause of the "bubble injestion" problems. SN8 didnt have any problems starting up or running through the flip, but it had fuel pressure problems because all the bubbles turned back into fuel instead of pressurizing the fuel tank.

IIRC, the SN8 fuel pressurization issues were caused by LCH4 slosh which caused the GCH4 pressurant to condense back into a liquid, causing the loss of fuel pressure.  Slosh would need to be prevented to address that issue as well.

Edit:  Excerpt from Elon tweet on 3/9/21.  (Don't know how to embed a tweet, sorry.)
"Helium in header was used to prevent ullage collapse from slosh, which happened in prior flight."
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BlackholeLP on 04/08/2021 09:47 pm
I'm going to put my money on tensioning hypothesis, perhaps as part of a stage separation simulation rig?

Really though, who can tell at this point.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: especedespace on 04/08/2021 09:56 pm
Another possibility - could NASA have said "you *must* have a launch escape system to get crew rated for any of our missions"?

Is it possible that this is a dummy for a crew capsule to sit on the top with super dracos in case it all goes tits up?
ok the shape looks vaguely familiar https://komonews.com/news/local/apollo-11-capsule-to-go-on-road-trip-visit-seattles-museum-of-flight (https://komonews.com/news/local/apollo-11-capsule-to-go-on-road-trip-visit-seattles-museum-of-flight), but the idea seems wild
(Photo Smithonian Institute)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/08/2021 11:09 pm
I'm almost certain that thing on the nosecone is some sort of tensioning jig, but I'm having a bit of a hard time working out why they would tension it down. Is max-q that intense that there is danger in collapsing the nose? Or might they apply tension in the lateral direction? Actually now that I think about it, that make more sense. Perhaps it could simulate force experienced during the bellyflop. But then what about those things attached to where the upper flaps are located? Shouldn't that simulate force in this direction (if tensioned)? I don't quite get it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 04/08/2021 11:40 pm
I'm almost certain that thing on the nosecone is some sort of tensioning jig, but I'm having a bit of a hard time working out why they would tension it down. Is max-q that intense that there is danger in collapsing the nose? Or might they apply tension in the lateral direction? Actually now that I think about it, that make more sense. Perhaps it could simulate force experienced during the bellyflop. But then what about those things attached to where the upper flaps are located? Shouldn't that simulate force in this direction (if tensioned)? I don't quite get it.

Perhaps it is not tension down but tension up? If there were posts going from the eyelets on the black hat down to the white pillars, the posts would be in compression but put tension on the nose cone. If this is a chomper cutting jig, that would be a perfect setup to maintain the shape of the nose while the door is cut.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 04/08/2021 11:40 pm
I'm almost certain that thing on the nosecone is some sort of tensioning jig, but I'm having a bit of a hard time working out why they would tension it down. Is max-q that intense that there is danger in collapsing the nose? Or might they apply tension in the lateral direction? Actually now that I think about it, that make more sense. Perhaps it could simulate force experienced during the bellyflop. But then what about those things attached to where the upper flaps are located? Shouldn't that simulate force in this direction (if tensioned)? I don't quite get it.
It spreads the load of the structural test over the whole nose, not just one point.  Most likely for ascent to make sure cargo gets to orbit.  Reentry and landing are not as important at the moment. Aerodynamic forces will be simulated on the flaps and the nose while the thrust of the engines will be pushing from below.  Main concern is probably the structural integrity of the cargo door, but this test article is obviously door-less so it is more or less a benchmark.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tgio on 04/09/2021 12:02 am
I'm almost certain that thing on the nosecone is some sort of tensioning jig, but I'm having a bit of a hard time working out why they would tension it down. Is max-q that intense that there is danger in collapsing the nose? Or might they apply tension in the lateral direction? Actually now that I think about it, that make more sense. Perhaps it could simulate force experienced during the bellyflop. But then what about those things attached to where the upper flaps are located? Shouldn't that simulate force in this direction (if tensioned)? I don't quite get it.

Maybe the flap jigs would apply tension in one lateral direction ("up" during the bellyflop) to simulate the aero forces on the flaps during the bellyflop, and the nose jig would apply tension in the opposite lateral direction ("down") to simulate the full header tank? They don't seem to have had any issues with the header tank "bending" the nosecone on descent on flights so far, but perhaps the future chomper cutout reduces the structural integrity of the nose such that they need to test it prior to flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 04/09/2021 02:09 am
They lowered a hydraulic ram and load cell into the nose prior to capping it... interesting...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/09/2021 03:28 am
That would imply an upward pressure, no? Or perhaps someone here knows something about these pistons. Can they apply force in either direction? If the ram is able to pull down, would this simulate a full header tank perhaps?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/09/2021 03:54 am
That would imply an upward pressure, no? Or perhaps someone here knows something about these pistons. Can they apply force in either direction? If the ram is able to pull down, would this simulate a full header tank perhaps?
Depends on the cylinder - A single acting cylinder can only push or pull, depending on how its designed.  Double acting cylinders can do both.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/09/2021 07:19 am
I'm almost certain that thing on the nosecone is some sort of tensioning jig, but I'm having a bit of a hard time working out why they would tension it down. Is max-q that intense that there is danger in collapsing the nose? Or might they apply tension in the lateral direction? Actually now that I think about it, that make more sense. Perhaps it could simulate force experienced during the bellyflop. But then what about those things attached to where the upper flaps are located? Shouldn't that simulate force in this direction (if tensioned)? I don't quite get it.
I still think it might all be a test rig to figure out how best to support the weight of Starship on the forward flaps, so it can be caught by the launch tower like SH.

I'm not sure how the nose jig would fit in to that, unless it is a test safety device.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/09/2021 07:26 am
It has 2 hose connectors so it's probably a double acting cylinder. If someone knew what load cells they use then maybe you could figure out if you can measure pulling force/tension with this load cell.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bkent136 on 04/09/2021 12:13 pm
Could the new nose structure be something for the Lunar mockup? Maybe a dragon docking station? Or maybe Lunar landing thruster ports? Is there only one hole out of the side?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robertross on 04/09/2021 12:38 pm
That would imply an upward pressure, no? Or perhaps someone here knows something about these pistons. Can they apply force in either direction? If the ram is able to pull down, would this simulate a full header tank perhaps?
Depends on the cylinder - A single acting cylinder can only push or pull, depending on how its designed.  Double acting cylinders can do both.

From the pic:
https://forum.nasaspaceflight.com/index.php?topic=52398.msg2217801#msg2217801

The cylinder is definitely double acting.
But the question is, what is the load cell (blue) designed for (tension or compression, or possibly both)? That is the determining factor.

I would venture a guess it's for compression, and the ram is to exert force on the nosecone, being supported by the fabricated steel structure. Perhaps for testing nose cone separation loads and required explosive bolt tension?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 04/09/2021 01:07 pm
That would imply an upward pressure, no? Or perhaps someone here knows something about these pistons. Can they apply force in either direction? If the ram is able to pull down, would this simulate a full header tank perhaps?
Depends on the cylinder - A single acting cylinder can only push or pull, depending on how its designed.  Double acting cylinders can do both.

From the pic:
https://forum.nasaspaceflight.com/index.php?topic=52398.msg2217801#msg2217801

The cylinder is definitely double acting.
But the question is, what is the load cell (blue) designed for (tension or compression, or possibly both)? That is the determining factor.

I would venture a guess it's for compression, and the ram is to exert force on the nosecone, being supported by the fabricated steel structure. Perhaps for testing nose cone separation loads and required explosive bolt tension?

SpaceX don’t use explosive bolts and the nose cone won’t separate. This is only the top half and the staging interface is at the bottom.  Occam’s razor suggests an aero loads simulator. Weight elimination was Elon’s priority #3. It looks like they are testing fairing section launch and landing loads to see if they can shave off some excess steel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sugmullun on 04/09/2021 01:17 pm
Could the whole setup,including external frame, when finished, be a structural test device for superheavy simulating starship load in flight?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/09/2021 01:45 pm
First thought on the cap is it is something like what falcon core stages have on their head while undergoing static firing in mcgregor.....

I’m thinking this is just a full up test on the nose to verify it can survive the high stresses that higher altitude flights and SH flights will include (MAXQ/Supersonic)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: donaldp on 04/09/2021 01:56 pm
If the nose is supposed to support 100t of payload then they need to test how that payload is supported by the nosecone either via the walls or some adapter onto the top of the tanks below. That  together with the dynamic loads of launch or descent could lead to some complex load paths. I guess they need to test all of this. I assume that we don't know what the internal structure of that particular nose code actually consist of?

Different configurations of starship may well have very different load requirements so I guess the jig is designed to test all sorts of loads.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/09/2021 02:00 pm
First thought on the cap is it is something like what falcon core stages have on their head while undergoing static firing in mcgregor.....

I’m thinking this is just a full up test on the nose to verify it can survive the high stresses that higher altitude flights and SH flights will include (MAXQ/Supersonic)

With F9, that load cap is to emulate the weight of the second stage though, no? You might be right about testing stresses at MaxQ/supersonic but I have a hard time understanding why stresses would be so great on a small area that it warrants setting up a jig like this. Then again, I'm far from being an aerodynamicist! It's the only thing that sort of makes sense to me at this point (testing aero loads).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/09/2021 02:03 pm
If the nose is supposed to support 100t of payload then they need to test how that payload is supported by the nosecone either via the walls or some adapter onto the top of the tanks below.

Yes, but the nose tip (lox header tank) isn't supporting 100 tonnes of payload. That will be likely supported by a payload adapter, transmitting the load paths directly to the tank section.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: donaldp on 04/09/2021 02:10 pm
If the nose is supposed to support 100t of payload then they need to test how that payload is supported by the nosecone either via the walls or some adapter onto the top of the tanks below.

Yes, but the nose tip (lox header tank) isn't supporting 100 tonnes of payload. That will be likely supported by a payload adapter, transmitting the load paths directly to the tank section.

Thats an assumption... the best part is no part.. The nose cone exists so why not use that as part of the payload adapter which is also what this jig may be designed to test. i.e. the various paylod adapters as part of the nose. Besides I'm not sure that a payload adapter independant of the nosecone would support all the load when starship is descending horizontally surely they will be an integral structure.

I should proably clarify that by nose I'm talking about the whole structure not just the tip and lox tank that's missing on this particular one.

(Editied for clarity).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/09/2021 03:08 pm
If the nose is supposed to support 100t of payload then they need to test how that payload is supported by the nosecone either via the walls or some adapter onto the top of the tanks below. That  together with the dynamic loads of launch or descent could lead to some complex load paths. I guess they need to test all of this. I assume that we don't know what the internal structure of that particular nose code actually consist of?

Different configurations of starship may well have very different load requirements so I guess the jig is designed to test all sorts of loads.
Always good to hear a nice, concise explanation. And about as accurate as any I've seen so far.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/09/2021 03:16 pm
If the nose is supposed to support 100t of payload then they need to test how that payload is supported by the nosecone either via the walls or some adapter onto the top of the tanks below. That  together with the dynamic loads of launch or descent could lead to some complex load paths. I guess they need to test all of this. I assume that we don't know what the internal structure of that particular nose code actually consist of?

Different configurations of starship may well have very different load requirements so I guess the jig is designed to test all sorts of loads.

Also keep in mind we have seen a test tank of 3mm supposedly to see if the whole starship can be made of 3mm which would reduce weight significantly.
So if they use 3mm which would take the stress of 6bar pressure for the tanks they could probably go even thinner for the nose cone(2mm) which would need 1bar pressure(only for crew). Even further weight reduction. I think the whole nose cone has ribbing so it wont buckle.

1. tanks and bottom 3mm
2. nose cone 2mm
3. crew and cargo could have different thicknesses.

Shave weight where you can and test the hell out of it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/09/2021 07:41 pm
twitter.com/w00ki33/status/1380575287516176384

Quote
The beauty of iteration. #spacex

Starship MK1 – Sept 2019
Starship SN9 – Jan 2021

https://twitter.com/elonmusk/status/1380606296945135617

Quote
Simulation is improving rendering resolution  …
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/09/2021 08:03 pm
I think the whole nose cone has ribbing so it wont buckle.

For crew, the nosecone won't have simply ribbing, it would have floors inside (think ribbing all the way to the center, so extra strong) and walls (super thick stringers) or are we going with the idea that the nosecones are just sleeved on top of the crew module that sits like a huge self contained payload inside the nosecone (and then, why does the cone itself need to be pressed?)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/09/2021 08:08 pm
If the nose is supposed to support 100t of payload then they need to test how that payload is supported by the nosecone either via the walls or some adapter onto the top of the tanks below. That  together with the dynamic loads of launch or descent could lead to some complex load paths. I guess they need to test all of this. I assume that we don't know what the internal structure of that particular nose code actually consist of?

Different configurations of starship may well have very different load requirements so I guess the jig is designed to test all sorts of loads.

Also keep in mind we have seen a test tank of 3mm supposedly to see if the whole starship can be made of 3mm which would reduce weight significantly.
So if they use 3mm which would take the stress of 6bar pressure for the tanks they could probably go even thinner for the nose cone(2mm) which would need 1bar pressure(only for crew). Even further weight reduction. I think the whole nose cone has ribbing so it wont buckle.

1. tanks and bottom 3mm
2. nose cone 2mm
3. crew and cargo could have different thicknesses.

Shave weight where you can and test the hell out of it.

I'm not certain about the entire nose being thinner.  The compound curvature and decreasing diameter toward the tip will help with strength, but the cargo version will have all kinds of structural compromises.

SpaceX would have a hard time getting custom widths of stainless, but maybe custom thicknesses to match requirements would be more achievable, 2.4 mm for the nose or 3.6 mm for the tanks or some such thing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/09/2021 08:10 pm
I think the whole nose cone has ribbing so it wont buckle.

For crew, the nosecone won't have simply ribbing, it would have floors inside (think ribbing all the way to the center, so extra strong) and walls (super thick stringers) or are we going with the idea that the nosecones are just sleeved on top of the crew module that sits like a huge self contained payload inside the nosecone (and then, why does the cone itself need to be pressed?)

I meant stringers. Couldn't remember the word so I used ribbing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rocketmaniac000 on 04/09/2021 09:18 pm
I honestly think all 3 engines are needed for the moment the starship goes from belly to straight when landing.
2 from then on sure, but the ship coped with the pendulum effect during the swing down a lot better when sn10 used the 3 engines to strighten up. Sn9 struggled during that moment with little engine thrust and body slamed the pad like a WWE wrestler.
SN8 flipped perfectly fine with just 2 engines. SN9 struggled because it only had one engine running.
Which is why the 3 should be started at that point to see what you have working, then turn off if need be. Getting the engine or number of engines you require at a seconds notice isnt something available at this moment in time. Shame to see it crash with a perfectly good engine not even used while broken ones flail about doing very little, just before it eats concrete. It makes sense, especially if humans are aboard the ship in the near future for this to be a proceedure.
In my opinion, getting the engines started could actually work very efficiently.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ioncloud9 on 04/09/2021 10:16 pm
https://twitter.com/rgvaerialphotos/status/1380632489501331459

Quote
Hexagram spotted next to the mystery nosecone

Its Jewish space lasers I knew it!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BlackholeLP on 04/09/2021 10:39 pm
What the hell are we looking at? I would say some sort of weird catch mechanism prototype, but the hex aperture is too small. They can't slide that over the nosecone... are they going to attach it to hydraulics and crush test the thing? With the hydraulic item they lifted inside... resisting? I really have no idea at this point.

Or are they going to lift the cone out and then attach this new hexagon and this is being overthought?

Could this have something to do with the hexagonal attachment point seen on SH domes? Maybe a stage separation rig after all?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Adriano on 04/09/2021 10:54 pm
I think it is a contraption to test the structure applying loads to the nose and to the forward flap hinges and possibly to attachment points on the inside.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 04/09/2021 11:35 pm
Looks like the skeleton for what a nose with a lid would need.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/10/2021 12:02 am
I think now that the nose is inside, this gets slipped over the nose to make a second "level" to the structure, with more cross-braced vertical members joining this with the base.  Then various hydraulic cylinders can be run between the frame and the flaps, nose, etc to simulate various loads.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: magicsound on 04/10/2021 12:06 am
Regarding the engine restart difficulty in the "flip" maneuver,  a small drogue parachute would help a lot, and might provide enough ullage that the header tanks wouldn't be needed for the restart. It's a pretty simple and obvious solution to test, and while this black nose cone cap doesn't look entirely suitable, it does displace the top header tank from its previous location.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 04/10/2021 12:11 am
I only see one socket/lift point on the hex. It is on the inside of the top right point.

It appears there are bolts or something on the bottom of each of the outside points, it looks like wood or something holding those up. The bottom of each of the outside points are also hexagons matching the top of the mystery structure pillars. So this bolts to the top of the pillars maybe?

What the hell is this?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/10/2021 12:26 am
Regarding the engine restart difficulty in the "flip" maneuver,  a small drogue parachute would help a lot, and might provide enough ullage that the header tanks wouldn't be needed for the restart. It's a pretty simple and obvious solution to test, and while this black nose cone cap doesn't look entirely suitable, it does displace the top header tank from its previous location.

A quickly replaceable drogue chute reminds me of the Tesla replaceable battery.

An interesting idea as a backup plan, but didn't end up getting used.  Turns out charging problem got solved.  I suspect the ullage collapse issue will also get solved.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/10/2021 12:51 am
Regarding the engine restart difficulty in the "flip" maneuver,  a small drogue parachute would help a lot, and might provide enough ullage that the header tanks wouldn't be needed for the restart. It's a pretty simple and obvious solution to test, and while this black nose cone cap doesn't look entirely suitable, it does displace the top header tank from its previous location.

A quickly replaceable drogue chute reminds me of the Tesla replaceable battery.

An interesting idea as a backup plan, but didn't end up getting used.  Turns out charging problem got solved.  I suspect the ullage collapse issue will also get solved.

Parachute discussion moved to https://forum.nasaspaceflight.com/index.php?topic=52986.msg2218321#msg2218321
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Metalskin on 04/10/2021 02:47 am
I think now that the nose is inside, this gets slipped over the nose to make a second "level" to the structure, with more cross-braced vertical members joining this with the base.  Then various hydraulic cylinders can be run between the frame and the flaps, nose, etc to simulate various loads.

This is my thought as well. To my eye, it seems that the hex shape will align with the existing structure and the internal brace cross over (on either op sides) will marry up up with the flap structures on the nose.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AlejandroC28 on 04/10/2021 03:23 am
re: orbit

Does anyone believe at this point that SpaceX have the production rate of several Raptors a week required to get anywhere near their aspirational target launch date?

Elon just tweeted that the goal is to get SH BN2 to the launchpad, with engines, by end of April. And that if they’re lucky it might even be capable of reaching orbit - presumably on its own, without a second stage.

That raises a question.  Will BN2 have a modified bottom to go on the test stands (which are designed for a Starship aft end not a Superheavy) or will they need to get the table installed on top of the columns at the orbital launch site first?



I have a Question.
How methane leakage of storage systems in the Starship ship is controlled, which types of devices are used and brands of manufacturers?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/10/2021 03:57 am
  Enlarging the photo from RGVAerialPhotography, it appears that there are bolt holes in the top plates of the vertical members of the white mystery structure. Yes, the enlargement is not the best, but maybe someone can find a better example from previous posts.
  I would suggest that the hexagram structure will go on top of a second level of vertical members bolted to the first level. Overall, it seems that a heavily braced structure is being created to apply loads to the nose cone and fin structures. Where they are the going to hang the disco ball?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Remes on 04/10/2021 06:20 am
I'm almost certain that thing on the nosecone is some sort of tensioning jig, but I'm having a bit of a hard time working out why they would tension it down.
A buckling test. That is standard procedure in order to validate the theoretical design.

It would encompass static/dynamic loads, bending moments (tvc), aerodynamic, some fuel slosh, ...

On youtube there is a video of the sls buckling test, if one has never seen one.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hkultala on 04/10/2021 10:51 am
Is the hole in the nose cap downwards or upwards (when in belly first attitude) ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tyrred on 04/10/2021 11:26 am
Is the hole in the nose cap downwards or upwards (when in belly first attitude) ?

Given the placement of thrusters, it would be upwards (+Z) it seems.

This will probably never fly, it just looks like some interesting test apparatus at this point.

But what do I know.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gefere on 04/10/2021 04:08 pm
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rcoppola on 04/10/2021 04:28 pm
I wonder if they'll also test lifting the Starship from up higher on the nose so they don't need any extrusions that far down the windward side where the current lift connect apparatus is. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/10/2021 06:30 pm
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.

Does it fit 100 passengers?

Moving on. Is it testing how hard they can pull on the nose tip? Actio=reactio they push from inside instead of actually pulling from above. Thinking about a new shepherd like drag brake that extends out and helps with flipping at the longest leverage arm that they have, the nose tip.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Poseidon on 04/10/2021 07:09 pm
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.

Does it fit 100 passengers?

This is not required for the Nasa lunar lander contract.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AndyH on 04/10/2021 07:56 pm
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.

Does it fit 100 passengers?
This is not required for the Nasa lunar lander contract.
Neither is yet another off-topic round of "must haz escape tower for human ratingz". 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gefere on 04/10/2021 09:04 pm
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.

Does it fit 100 passengers?
This is not required for the Nasa lunar lander contract.
Neither is yet another off-topic round of "must haz escape tower for human ratingz".

Words in people's mouths much? Nobody's said that (uh, recently). And for the record I think the flip will work out fine. It's just 1) if they thought they could able to launch people a couple years sooner and possibly grab some Artemis launches, there's a lot of money in that; and 2) that thing sure is capsule-shaped.

If I were running the project, I'd say "that's a distraction; let's get to orbit first." But I'd say that about catching the booster with the launch tower, too, so what do I know?

Another thing I don't understand: if it's a structural load test setup, why cut off pieces of the structure you're trying to test? Why not weld on attachment points if you need them?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 04/10/2021 09:23 pm
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.

Does it fit 100 passengers?
This is not required for the Nasa lunar lander contract.
Neither is yet another off-topic round of "must haz escape tower for human ratingz".

Words in people's mouths much? Nobody's said that (uh, recently). And for the record I think the flip will work out fine. It's just 1) if they thought they could able to launch people a couple years sooner and possibly grab some Artemis launches, there's a lot of money in that; and 2) that thing sure is capsule-shaped.

If I were running the project, I'd say "that's a distraction; let's get to orbit first." But I'd say that about catching the booster with the launch tower, too, so what do I know?

Another thing I don't understand: if it's a structural load test setup, why cut off pieces of the structure you're trying to test? Why not weld on attachment points if you need them?

I think it's hard to judge scale from that distance but I think that capsule shaped object is rather tiny even for only 2 people in flight suits. There are images with workers standing on top of the nose in the production updates thread, shortly before the object was placed on it. check it out. Not to mention any seats/screens/interior.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: electricdawn on 04/10/2021 09:25 pm
I don't think(!) that SpaceX is bothering at all right now with a launch escape system on Starship. They have bigger fish to fry.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/10/2021 09:37 pm
I don't think(!) that SpaceX is bothering at all right now with a launch escape system on Starship. They have bigger fish to fry.

Skip the hedging. ;)  They aren't bothering with LES now.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MTom on 04/10/2021 09:44 pm
  Enlarging the photo from RGVAerialPhotography, it appears that there are bolt holes in the top plates of the vertical members of the white mystery structure. Yes, the enlargement is not the best, but maybe someone can find a better example from previous posts.
  I would suggest that the hexagram structure will go on top of a second level of vertical members bolted to the first level. Overall, it seems that a heavily braced structure is being created to apply loads to the nose cone and fin structures. Where they are the going to hang the disco ball?

IMHO there are the columns for the "second level", from BCG pics.
https://forum.nasaspaceflight.com/index.php?topic=52398.msg2218611#msg2218611

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dondar on 04/10/2021 09:45 pm
https://twitter.com/rgvaerialphotos/status/1380632489501331459

Quote
Hexagram spotted next to the mystery nosecone
interesting, the bolt-holes in the black rig are not symmetrical, servicing hole (I call it service hole because it looks like exactly all other service hatches in Starships) is between these three holes. Now thinking about it, the strange bar structures on sides of this nosecone are placed where the flaps are and look to be controllable. The hexagonal thing lying next to it is also not symmetrical.
I tend to agree with previous posts that they build a rig to test descend loads and structural asymmetry supports  this.  (the service hole is on a side which is supposed to be down during diving phase.). Why black? It really doesn't look like steel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 04/10/2021 09:47 pm
Guys, the load cap is about as aerodynamic as an excavator and made from pretty thick steel. The manhole is for assembly/ inspection purposes, not for somebody to sit in. The whole SS nose section is getting encased in a steel cage that will connect the cap to the base.
How could this possibly be an LAS prototype or a flight article? An escape capsule? Just because it’s an inverted cone?
Isn’t that a bit simplistic and ignoring everything else about the test rig? Less phantasy, wishful thinking and a bit more logic would be appreciated...

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: petrsida on 04/10/2021 10:23 pm
I think they are building a jig for making a cargo space lid and and to test its stress.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/10/2021 11:31 pm
I think they are building a jig for making a cargo space lid and and to test its stress.

I can't think of a time a jig used in fabrication doubled as a stand for stress testing. Seems unlikely.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: niwax on 04/11/2021 12:04 am
Here is my rampant speculation: Starships coming back from higher altitudes or even orbit will have much higher loads on the flaps and hinges. This rig allows them to test that, possibly in combination with different nose cone construction methods regarding cutouts for cargo or docking ports.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jim Aldridge on 04/11/2021 12:07 am
https://twitter.com/_brendan_lewis/status/1380646421410377728

Quote
The current status of SpaceX's Starship & Superheavy prototypes. 10th April 2021

I love these graphics.  It helps every now and then to get a quick visual on the production status.  It is also interesting to see how far along they get in production of some iterations, only to decide to scrap the intermediate models and jump ahead...like they did between SN11 and SN15, and might do between SN17 and SN20, depending on how the testing goes.  Great work Brendan Lewis!!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 04/11/2021 02:50 am
I think they are building a jig for making a cargo space lid and and to test its stress.

I can't think of a time a jig used in fabrication doubled as a stand for stress testing. Seems unlikely.
Based on how Spacex have been constructing Starship’s, this is not a construction jig.

Personally I think some sort of load testing of cargo area to see how/where stringers need to be added.  Will possibly get used repeatedly to try out different configurations (clamshell, Lunar lander etc. - basically any version with large doors).

Was also wondering if they may consider a cargo area with thinner shell.  Build one, put some pressure on and see if the modelling matches reality- faster and cheaper than building a whole Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AndyH on 04/11/2021 03:46 am
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.

Yes, a structural load test is more likely. I didn't say it was a good theory. But hey, it's a conic section with a hatch and room for a tower.

Does it fit 100 passengers?
This is not required for the Nasa lunar lander contract.
Neither is yet another off-topic round of "must haz escape tower for human ratingz".

Words in people's mouths much? Nobody's said that (uh, recently).

 And for the record I think the flip will work out fine. It's just 1) if they thought they could able to launch people a couple years sooner and possibly grab some Artemis launches, there's a lot of money in that; and 2) that thing sure is capsule-shaped.
Haven't seen my favorite theory mooted: the nose cap is a boilerplate for a capsule-style launch escape system.
This keeps coming up and it's just as invalid now as it's been since Hopper.  Starship won't have a capsule or an external escape system.  That particular pet theory has been mooted repeatedly and is off topic here.

https://forum.nasaspaceflight.com/index.php?topic=53396.msg2208852#msg2208852 (https://forum.nasaspaceflight.com/index.php?topic=53396.msg2208852#msg2208852)
https://forum.nasaspaceflight.com/index.php?topic=52537.msg2200470#msg2200470 (https://forum.nasaspaceflight.com/index.php?topic=52537.msg2200470#msg2200470)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tcollins2145 on 04/11/2021 04:24 am
Elon's Twitter
https://twitter.com/elonmusk/status/1379876450744995843 (https://twitter.com/elonmusk/status/1379876450744995843)



Next Post
https://twitter.com/Davis_404/status/1379975209877442561 (https://twitter.com/Davis_404/status/1379975209877442561)



My Question:
Any chance this new modified nosecone is for future SN-xx to work with tower and this is a pathfinder and for testing?  I was just curious what others here more knowledgeable than me might think!  I think I did the hyperlinks correctly.  It's my first post.  Feel free to message me if I did something wrong.  I tried to stay on topic, and I saw nothing mentioned prior to this on the subject.

Edited to try to correct hyperlinks
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Utopia Planitia on 04/11/2021 09:00 am
 I’m not qualified or experienced enough to make an educated guess as to what it’s testing exactly, but I think the fact they’re putting it in a cage is significant - one benefit of doing that is the ability to rotate it and perhaps test its ability to handle whatever they’re testing through the flip manoeuvres
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 04/11/2021 11:39 am
There was speculation about this object: 
 
https://twitter.com/WatchersTank/status/1380844346224836611?s=19
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/11/2021 01:38 pm
Something to watch out for on future SN's 
 
https://twitter.com/WatchersTank/status/1380844346224836611?s=19

A while ago there was a discussion about that white dish on sn15, never seen in other prototypes. Someone suggested that could a starlink dish, but the general agreement was that it wasn't. Seems like that we were wrong.

The document also says "altitude not higher than 12.5 km", so ISTM that they aren't going to fly higher, for now. This demonstrates that sn15 is for testing landing, and not supersonic flight regime. Better to change one variable at the time.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/11/2021 02:22 pm
Given the fit and finish of the bits and pieces hanging on the outside of Starship it’s not ready for super sonic flight anyway.  There are early prototypes for landing practice, so I get that.  Cabling and conduits are hanging everywhere.

From EM’s tweets it seems like SN20 is where they will making things more flight worthy.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: LDLB on 04/11/2021 03:54 pm
Given the fit and finish of the bits and pieces hanging on the outside of Starship it’s not ready for super sonic flight anyway.  There are early prototypes for landing practice, so I get that.  Cabling and conduits are hanging everywhere.

From EM’s tweets it seems like SN20 is where they will making things more flight worthy.

I appreciate it's not the most aerodynamic at the moment, however there's no particular reason why the current generation can't go supersonic. However, I do acknowledge it wouldn't be far beyond the sound barrier as it looks currently.

SN15 has made good progress in streamlining the vehicle. Depress vents are smaller and more compact, and there's all-round general tidyness over the last generation. I would definitely say SN8-SN11 weren't made for supersonic, but I wouldn't be surprised if SN15 up to SN20, will do at some point (once a successful recovery has been achieved). Even pushing to around 20km can get you beyond the barrier. Of course it's not just about going supersonic, but you'll get significantly more flight time on various pieces of hardware, notably Raptors.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/11/2021 04:02 pm
Given the fit and finish of the bits and pieces hanging on the outside of Starship it’s not ready for super sonic flight anyway.  There are early prototypes for landing practice, so I get that.  Cabling and conduits are hanging everywhere.

From EM’s tweets it seems like SN20 is where they will making things more flight worthy.

I appreciate it's not the most aerodynamic at the moment, however there's no particular reason why the current generation can't go supersonic. However, I do acknowledge it wouldn't be far beyond the sound barrier as it looks currently.

SN15 has made good progress in streamlining the vehicle. Depress vents are smaller and more compact, and there's all-round general tidyness over the last generation. I would definitely say SN8-SN11 weren't made for supersonic (once a successful recovery has been achieved), but I wouldn't be surprised if SN15 up to SN20, will do at some point. Even pushing to around 20km can get you beyond the barrier. Of course it's not just about going supersonic, but you'll get significantly more flight time on various pieces of hardware, notably Raptors.

Good point on more flight time for raptors and the free fall.

I've not been worried about the ragged appearance, that can all be tightened up once they know how they can land it safely.  The rest is work after that, but then they move on to heatshield, on orbit fuel transfer and the Cargo door.  That is going to be very interesting. 

SpaceX is much bigger than it use to be financially, but this is still a mega rocket on shoe string.  It's fun to see how they are solving the big problems without taking on everything at once.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: vaporcobra on 04/11/2021 06:05 pm
Hi guys, hope this hasn't already been asked, but does anyone know or have any guesses as to what is that white thing (in the red box in the pic) on SN15?

Photo by Jack Beyer for NSF, from twitter (sorry, don't know how to put the link without the preview being shown  :-\ )

My post fell through the cracks (https://forum.nasaspaceflight.com/index.php?topic=53361.msg2212710#msg2212710) during the late FAA inspector furor 😅 I'm still very curious, too. Much better photos from Mary during SN15's high bay move today, thankfully!

Have to admit that my first thought was a Starlink dish, as the location makes no sense for a window test. If not Starlink, some other kind of flat-panel antenna, or possibly an EMR-transparent 'window' for some other kind of communications equipment.

Looks like my intuition was right on the money the first time around... 😅
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/11/2021 06:18 pm
Given the fit and finish of the bits and pieces hanging on the outside of Starship it’s not ready for super sonic flight anyway.  There are early prototypes for landing practice, so I get that.  Cabling and conduits are hanging everywhere.

From EM’s tweets it seems like SN20 is where they will making things more flight worthy.

I appreciate it's not the most aerodynamic at the moment, however there's no particular reason why the current generation can't go supersonic. However, I do acknowledge it wouldn't be far beyond the sound barrier as it looks currently.

SN15 has made good progress in streamlining the vehicle. Depress vents are smaller and more compact, and there's all-round general tidyness over the last generation. I would definitely say SN8-SN11 weren't made for supersonic, but I wouldn't be surprised if SN15 up to SN20, will do at some point (once a successful recovery has been achieved). Even pushing to around 20km can get you beyond the barrier. Of course it's not just about going supersonic, but you'll get significantly more flight time on various pieces of hardware, notably Raptors.

That will be an intersting test, many minutes of raptor firing. But I think, as far my experience with other engineering things is correct, it is better to not change a lot of variables at one time, otherwise you won't know what went wrong. IMO sn15 has no excuses to not land, the problems with that should be solved.

As you say sn15+ should not have problem going over Mach 1, and could be the job for sn16 or maybe sn17.

BTW, has sn19 been scrapped? It has been for a while that we didn't see new partes. IIRC sn17 and sn18 seem under construction.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: oldAtlas_Eguy on 04/11/2021 06:26 pm
Although the hardware of the Starlink UT mounted on SN15 may be 'electrically identical' to the UTs currently used throughout the US. The software may not be. Just need a flight qualified electrical device (router/switch) to connect to that has a power over ethernet connector.

Anyway a Starlink UT would support ~6 4K video streams plus a backup stream for the regular telemetry as well. It should maintain connect during for most of the stable low attitude change portion of flight without much problems. But the pitch over at apogee and the pitch up at landing may be to fast for it to maintain it's connection. But it could still work. Do not know just how good a more advanced software could make a UT for use in a flight vehicle.

With a secondary source for data downloads it improves the confidence that data can be gathered. For orbital need a way to maintain a telemetry feed during the attempt latter this year. This would be a test to determine if it is feasible to use Starlink for such a link vs using ships parked out in the gulf along the flight path to gather telemetry data during the ascent to orbit. Tail on always presents a difficult telemetry link and is fraught with many drops. That is why the Eastern Range has telemetry sites north and south at quite a few km from the launch sites. To get better angles and better links to the telemetry of a orbital launch regardless of the launch azimuth.

Other note. I do not think SN19 has been scrapped just put on hold awaiting the level of flight success of SN15 possibly as well SN16. If things go well SN19 may not get built. If things do not more pieces may show up. Then again things (design) may have altered to the point that SN19 is considered too obsolete and  if things go poorly then orbital attempt may wait for a latter SN than SN20 or just ignore the current return and landing difficulties and continue on with attempt to orbit anyway.

Added: With a Starship to Starlink link it is possible to gather and return telemetry data during the what is known as the reentry blackout period.
https://arc.aiaa.org/doi/abs/10.2514/1.A32880 (https://arc.aiaa.org/doi/abs/10.2514/1.A32880)
Would just need the right timing to get a sat in line of site of the hole in the plasma that exists above the vehicle. Note that due to being 1/2 the normal distance signal strengths would be 6db higher

This would enable the gathering of performance data during reentry even if the vehicle failed during reentry where it would normally be out of contact.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aero on 04/11/2021 09:11 pm
I found this on the Boring Co. thread for some reason.

https://www.elonx.net/ (https://www.elonx.net/)

It gives a complete run-down of what happened to SN10.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: _MECO on 04/11/2021 09:51 pm
Given the fit and finish of the bits and pieces hanging on the outside of Starship it’s not ready for super sonic flight anyway.  There are early prototypes for landing practice, so I get that.  Cabling and conduits are hanging everywhere.

From EM’s tweets it seems like SN20 is where they will making things more flight worthy.

I appreciate it's not the most aerodynamic at the moment, however there's no particular reason why the current generation can't go supersonic. However, I do acknowledge it wouldn't be far beyond the sound barrier as it looks currently.

SN15 has made good progress in streamlining the vehicle. Depress vents are smaller and more compact, and there's all-round general tidyness over the last generation. I would definitely say SN8-SN11 weren't made for supersonic, but I wouldn't be surprised if SN15 up to SN20, will do at some point (once a successful recovery has been achieved). Even pushing to around 20km can get you beyond the barrier. Of course it's not just about going supersonic, but you'll get significantly more flight time on various pieces of hardware, notably Raptors.
BTW, has sn19 been scrapped? It has been for a while that we didn't see new partes. IIRC sn17 and sn18 seem under construction.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Proesterchen on 04/11/2021 10:29 pm
Today's SN-20 leg skirt double (WO ä1642026) could be a do-over, as there already was another SN-20 leg skirt double (WO #1596856) earlier in March.

Could be a sign of an issue during outfitting of the skirt or changes needed for an updated staging interface with the booster.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Proesterchen on 04/11/2021 10:33 pm
As you say sn15+ should not have problem going over Mach 1, and could be the job for sn16 or maybe sn17.

BTW, has sn19 been scrapped? It has been for a while that we didn't see new partes. IIRC sn17 and sn18 seem under construction.
To this point, we haven't even seen the start of assembly for any Starship beyond SN-15, so SN-1x may be done as BN-2 and GSE take the bulk of capacity with BN-3 and SN-20 starting to come together.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pueo on 04/11/2021 11:01 pm
Added: With a Starship to Starlink link it is possible to gather and return telemetry data during the what is known as the reentry blackout period.
https://arc.aiaa.org/doi/abs/10.2514/1.A32880 (https://arc.aiaa.org/doi/abs/10.2514/1.A32880)
Would just need the right timing to get a sat in line of site of the hole in the plasma that exists above the vehicle. Note that due to being 1/2 the normal distance signal strengths would be 6db higher

This would enable the gathering of performance data during reentry even if the vehicle failed during reentry where it would normally be out of contact.

During the re-entry blackout the Shuttle communicated with ground using its S-band antennas and the TDRSS.  It couldn't use its Ku-band antenna because being mechanically steered it was stored in the payload bay.  I bet NASA would have loved having an electrically steered Ku-band antenna back in the day.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: oldAtlas_Eguy on 04/11/2021 11:29 pm
Added: With a Starship to Starlink link it is possible to gather and return telemetry data during the what is known as the reentry blackout period.
https://arc.aiaa.org/doi/abs/10.2514/1.A32880 (https://arc.aiaa.org/doi/abs/10.2514/1.A32880)
Would just need the right timing to get a sat in line of site of the hole in the plasma that exists above the vehicle. Note that due to being 1/2 the normal distance signal strengths would be 6db higher

This would enable the gathering of performance data during reentry even if the vehicle failed during reentry where it would normally be out of contact.

During the re-entry blackout the Shuttle communicated with ground using its S-band antennas and the TDRSS.  It couldn't use its Ku-band antenna because being mechanically steered it was stored in the payload bay.  I bet NASA would have loved having an electrically steered Ku-band antenna back in the day.
It is all a matter of beaming through the hole. Starlink has a couple of advantages as the signal strengths not counting the loss due edge effects from the surrounding plasma will be significantly greater than on the ground. No atmospheric losses and as well 1/2 the distance. TDRSS only operated in space and since it was  at GEO and the Shuttle at LEO there was no difference in signal strengths than in normal usage. So there should not be a problem for the Starlink UT on a Starship in operating at near full data rates of almost 100Mbps.

As far as the hole and finding a sat there at this time may be spotty coverage. But 3 months from now there will be as many or more than 300 Starlink sats additional than what there is now in their operational orbital positions. A 33% increase in the total. eventually there will be enough sats for solid coverage at any time and any inclination. With just the right geometry and timing SS20 could have a solid link through Starlink for the complete duration of the normal blackout period. Before and after that would be able to connect to more alternate sats at lower incidence angles on the UT's array.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/12/2021 01:29 am
Added: With a Starship to Starlink link it is possible to gather and return telemetry data during the what is known as the reentry blackout period.
https://arc.aiaa.org/doi/abs/10.2514/1.A32880 (https://arc.aiaa.org/doi/abs/10.2514/1.A32880)
Would just need the right timing to get a sat in line of site of the hole in the plasma that exists above the vehicle. Note that due to being 1/2 the normal distance signal strengths would be 6db higher

This would enable the gathering of performance data during reentry even if the vehicle failed during reentry where it would normally be out of contact.

During the re-entry blackout the Shuttle communicated with ground using its S-band antennas and the TDRSS.  It couldn't use its Ku-band antenna because being mechanically steered it was stored in the payload bay.  I bet NASA would have loved having an electrically steered Ku-band antenna back in the day.
It is all a matter of beaming through the hole. Starlink has a couple of advantages as the signal strengths not counting the loss due edge effects from the surrounding plasma will be significantly greater than on the ground. No atmospheric losses and as well 1/2 the distance. TDRSS only operated in space and since it was  at GEO and the Shuttle at LEO there was no difference in signal strengths than in normal usage. So there should not be a problem for the Starlink UT on a Starship in operating at near full data rates of almost 100Mbps.

As far as the hole and finding a sat there at this time may be spotty coverage. But 3 months from now there will be as many or more than 300 Starlink sats additional than what there is now in their operational orbital positions. A 33% increase in the total. eventually there will be enough sats for solid coverage at any time and any inclination. With just the right geometry and timing SS20 could have a solid link through Starlink for the complete duration of the normal blackout period. Before and after that would be able to connect to more alternate sats at lower incidence angles on the UT's array.

The closer distance to the Starlink sats may actually be a disadvantage since it means there are fewer of them in a given field of view through the hole, and that they will cross out of line of sight sooner.

How wide is the plasma cone anyway?  I guess it depends on the current mach speed of the vehicle?  The hole should point just a bit above the horizon for the high speed portion of reentry, shouldn't it?  That's good since it will "look into the distance" and see a larger area of the satellite orbit shell.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/12/2021 01:36 am
  Reviewing the new pics in the Boca Chica Production Update Master Thread is always a treat at end of the day. Many thanks to all the contributors: bocachicagal, Nomadd, FutureSpaceTourist, BradyKenniston, and the many others. Your time and efforts allow folks far away to have a front row seat to daily developments.
  I didn't realize that the flap emulators/jigs protrude as much as they do outside the envelope of the hexagonal white structure that is being assembled around the nose cone and barrel section. It would seem that the horizontal bracing in those areas will have to be very different or not put in at all.
  Pic is the first one from reply #1234 in the BC production update thread (credit: bocachicagal) 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BlackholeLP on 04/12/2021 01:54 am
If SN20 is an orbital vehicle, I wonder if SNs 16-18 might be slated for suborbital mach flights if a previous vehicle manages the landing on the current test trajectories, thus giving a purpose to the increased TPS coverage.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/12/2021 02:27 am
If SN20 is an orbital vehicle, I wonder if SNs 16-18 might be slated for suborbital mach flights if a previous vehicle manages the landing on the current test trajectories, thus giving a purpose to the increased TPS coverage.

The number of SN's needed between 15 and 20 may depend on if they successfully land one and are able to refly it.

they maybe reaching a point where they can't learn much more with out going to higher altitude and velocity. 

If SN15 goes well maybe there is a lot of other SN work that jumps to 20 and BN2 and GSE.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Cheapchips on 04/12/2021 11:07 am
I was confused by the Starlink dish pointing at the horizon. Home mounted ones have that motor to angle them. 

Being up several stories and ping not being an issue means that it's happy to latch onto a satellite closer to the horizon until it's freefalling?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/12/2021 12:27 pm
I was confused by the Starlink dish pointing at the horizon. Home mounted ones have that motor to angle them. 

Being up several stories and ping not being an issue means that it's happy to latch onto a satellite closer to the horizon until it's freefalling?
Or maybe they just have a Starlink satellite bolted to the side of the high bay  ;D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: waveney on 04/12/2021 01:11 pm
I was confused by the Starlink dish pointing at the horizon. Home mounted ones have that motor to angle them. 

Being up several stories and ping not being an issue means that it's happy to latch onto a satellite closer to the horizon until it's freefalling?
Or maybe they just have a Starlink satellite bolted to the side of the high bay  ;D

Or they time the launch to align with a starlink satellite at an appropriate angle.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chief on 04/12/2021 02:34 pm
I was confused by the Starlink dish pointing at the horizon. Home mounted ones have that motor to angle them. 

Being up several stories and ping not being an issue means that it's happy to latch onto a satellite closer to the horizon until it's freefalling?
Or maybe they just have a Starlink satellite bolted to the side of the high bay  ;D

Or they time the launch to align with a starlink satellite at an appropriate angle.

Despite their outward shape, Starlink "dishes" aren't parabolic reflector dishes - they are phased array antennas where the beam angle is steered electrically, not by the angle of a reflector. The units angle themselves to optimise the steerable range, so suboptimal angling restricts the number of satellites in view and the period for which they can be seen.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 04/12/2021 02:58 pm
I was watching the slow pan up BN1 in yesterday's update video and wondering if it could be edited into a Space Balls version of the original Star Wars opening scene of the bottom of the Imperial war ship. I bet Musk would love it  ::)

Edit - Follow up on Off Topic thread
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/12/2021 03:04 pm
I was confused by the Starlink dish pointing at the horizon. Home mounted ones have that motor to angle them. 

Being up several stories and ping not being an issue means that it's happy to latch onto a satellite closer to the horizon until it's freefalling?
This far south, I think Starlink is still a ways from a horizontally facing dish having a reliable connection. Dishes aren't allowed to point below 25 degrees, so it's working view will be pretty limited. It might be ok while they're bellyflopping and the dish is pointed up. But a dish that even works while the ship is pointing all over the place might not exactly be stock.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sucramdi on 04/12/2021 03:04 pm
Since that date has passed, it is irrelevant

RE the Starlink terminal authorization request; the date must be a typo, the request was filed April 9, 2021:

https://fcc.report/ELS/Space-Exploration-Holdings-LLC/0566-EX-ST-2021
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 04/12/2021 03:20 pm
Since that date has passed, it is irrelevant

RE the Starlink terminal authorization request; the date must be a typo, the request was filed April 9, 2021:

https://fcc.report/ELS/Space-Exploration-Holdings-LLC/0566-EX-ST-2021
Good observation, sound theory.  A license application with a start date almost a year in the past sure seems unlikely.  I've edited my post again to reference your note.  I'm on Team Typo now.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sucramdi on 04/12/2021 03:37 pm
Since that date has passed, it is irrelevant

RE the Starlink terminal authorization request; the date must be a typo, the request was filed April 9, 2021:

https://fcc.report/ELS/Space-Exploration-Holdings-LLC/0566-EX-ST-2021
Good observation, sound theory.  A license application with a start date almost a year in the past sure seems unlikely.  I've edited my post again to reference your note.  I'm on Team Typo now.

Also of note, last April SN3 popped and SN4 was moved to the stand. Any flight plans within 60 days would have been the 150m hops, 12.5km is a recent target from SN8+.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/12/2021 04:00 pm
Added: With a Starship to Starlink link it is possible to gather and return telemetry data during the what is known as the reentry blackout period.
https://arc.aiaa.org/doi/abs/10.2514/1.A32880 (https://arc.aiaa.org/doi/abs/10.2514/1.A32880)
Would just need the right timing to get a sat in line of site of the hole in the plasma that exists above the vehicle. Note that due to being 1/2 the normal distance signal strengths would be 6db higher

This would enable the gathering of performance data during reentry even if the vehicle failed during reentry where it would normally be out of contact.

During the re-entry blackout the Shuttle communicated with ground using its S-band antennas and the TDRSS.  It couldn't use its Ku-band antenna because being mechanically steered it was stored in the payload bay.  I bet NASA would have loved having an electrically steered Ku-band antenna back in the day.
It is all a matter of beaming through the hole. Starlink has a couple of advantages as the signal strengths not counting the loss due edge effects from the surrounding plasma will be significantly greater than on the ground. No atmospheric losses and as well 1/2 the distance. TDRSS only operated in space and since it was  at GEO and the Shuttle at LEO there was no difference in signal strengths than in normal usage. So there should not be a problem for the Starlink UT on a Starship in operating at near full data rates of almost 100Mbps.

As far as the hole and finding a sat there at this time may be spotty coverage. But 3 months from now there will be as many or more than 300 Starlink sats additional than what there is now in their operational orbital positions. A 33% increase in the total. eventually there will be enough sats for solid coverage at any time and any inclination. With just the right geometry and timing SS20 could have a solid link through Starlink for the complete duration of the normal blackout period. Before and after that would be able to connect to more alternate sats at lower incidence angles on the UT's array.
Sorry, but I never understood why it is possible to communicate with a spacecraft during reentry. I understood that the plasma caused loss of comunicatio. What am I missing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 04/12/2021 04:05 pm
Added: With a Starship to Starlink link it is possible to gather and return telemetry data during the what is known as the reentry blackout period.
https://arc.aiaa.org/doi/abs/10.2514/1.A32880 (https://arc.aiaa.org/doi/abs/10.2514/1.A32880)
Would just need the right timing to get a sat in line of site of the hole in the plasma that exists above the vehicle. Note that due to being 1/2 the normal distance signal strengths would be 6db higher

This would enable the gathering of performance data during reentry even if the vehicle failed during reentry where it would normally be out of contact.

During the re-entry blackout the Shuttle communicated with ground using its S-band antennas and the TDRSS.  It couldn't use its Ku-band antenna because being mechanically steered it was stored in the payload bay.  I bet NASA would have loved having an electrically steered Ku-band antenna back in the day.
It is all a matter of beaming through the hole. Starlink has a couple of advantages as the signal strengths not counting the loss due edge effects from the surrounding plasma will be significantly greater than on the ground. No atmospheric losses and as well 1/2 the distance. TDRSS only operated in space and since it was  at GEO and the Shuttle at LEO there was no difference in signal strengths than in normal usage. So there should not be a problem for the Starlink UT on a Starship in operating at near full data rates of almost 100Mbps.

As far as the hole and finding a sat there at this time may be spotty coverage. But 3 months from now there will be as many or more than 300 Starlink sats additional than what there is now in their operational orbital positions. A 33% increase in the total. eventually there will be enough sats for solid coverage at any time and any inclination. With just the right geometry and timing SS20 could have a solid link through Starlink for the complete duration of the normal blackout period. Before and after that would be able to connect to more alternate sats at lower incidence angles on the UT's array.
Sorry, but I never understood why it is possible to communicate with a spacecraft during reentry. I understood that the plasma caused loss of comunicatio. What am I missing?

There's a "hole" in the back of the plasma sheath; signals can be relayed to a satellite (the Shuttle used TDRSS (https://en.wikipedia.org/wiki/U.S._tracking_and_data_relay_satellite)) and back to the ground from there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: fisico on 04/12/2021 05:25 pm
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=current&application_seq=105749

Could this mean a 20km hop for sn15?
It is strange because the starlink user terminal request is stating 12,5km.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 04/12/2021 06:01 pm
Maybe they plan to initially test on "short" proof of landing hop(s) and then amend application for higher hops based on the results?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/12/2021 06:03 pm
(https://i.imgur.com/BLGWQQ8.png)

This is a SpaceX fluid dynamics simulation of dragon reentering at hypersonic speeds.  Note that the red areas (representing highly compressed and heated plasma) form a bow shock.  They form in a small area in the wake of the ship, but on the whole, there isn't much plasma behind the ship.  As long as you can aim your radio signal out of that hole, you're able to get it somewhere.  Hopefully up to a satellite that can then relay it somewhere useful.

Starship should form a similar hole, though obviously actual CFD simulations will be needed to figure out where.

Image source - SpaceX video about how they do CFD on GPUs https://www.youtube.com/watch?v=vYA0f6R5KAI
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AlejandroC28 on 04/12/2021 07:13 pm
Detail very thoroughly all the chemicals used for the operation of the spacecraft, from the testing and inspection procedures of the spacecraft to the take-off and landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/12/2021 08:17 pm
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OneSpeed on 04/12/2021 10:30 pm
The trailer tyres are ST235/80R16, so for a 16" rim, the grid fin is about 4.65m long. The trailer width is 2.6m so it is around 2.4m wide. This is over 4 times the area of the Falcon 9 Ti grid fin, which is about 2.0 x 1.3m.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/12/2021 10:37 pm
I'll take "why you test with Liquid Nitrogen before LOX/LMG" for $400, Alex.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/12/2021 11:31 pm
I'll take "why you test with Liquid Nitrogen before LOX/LMG" for $400, Alex.

What happened exactly? Do we know why there was a nitrogen dump?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/13/2021 12:01 am
I'll take "why you test with Liquid Nitrogen before LOX/LMG" for $400, Alex.

What happened exactly? Do we know why there was a nitrogen dump?

Not sure, but here's the post from the updates that makes it look like it was GSE, not Starship:

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2219500#msg2219500
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/13/2021 12:23 am
What happened exactly? Do we know why there was a nitrogen dump?
Likely because they did not need it after cryo test.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/13/2021 12:54 am
What happened exactly? Do we know why there was a nitrogen dump?
Likely because they did not need it after cryo test.

Hmm, ok. The most recent update thread post https://forum.nasaspaceflight.com/index.php?topic=53509.msg2219526#msg2219526 sounds good. I thought @InterestedEngineer was saying that it was an unintended leak.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/13/2021 01:07 am
What happened exactly? Do we know why there was a nitrogen dump?
Likely because they did not need it after cryo test.

Hmm, ok. The most recent update thread post https://forum.nasaspaceflight.com/index.php?topic=53509.msg2219526#msg2219526 sounds good. I thought @InterestedEngineer was saying that it was an unintended leak.

Not sure if unintended.  Unusual, though.

1.  Test like you fly.  Dumping LOX or LMG is a really bad idea.
2.  They use LN to cool their methane, so there really isn't a need to throw it away
3.  They normally don't dump that much nitrogen at once for cryo tests
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dubbie on 04/13/2021 02:31 am
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"

Plain carbon steel seems like a very strange material.
I doubt this is a flight article. It must be a production test article of some sort There are a lot of materials that would be better for this task. Plain steel is the worst of all worlds.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/13/2021 02:48 am
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"

Plain carbon steel seems like a very strange material.
I doubt this is a flight article. It must be a production test article of some sort There are a lot of materials that would be better for this task. Plain steel is the worst of all worlds.

You can't tell what alloy it is by looking at it. It may save a little bit of money while they are still making craters, but it may also be the most economical material for the job. Aluminum alloys can't take the heat. Titanium might cost more than the whole booster. SpaceX has lots of data on what grid fins need to withstand for a returning booster.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/13/2021 03:16 am
...
3.  They normally don't dump that much nitrogen at once for cryo tests

Cite please?  Based on previous tests, seems they get rid of it as soon after they are done--no sense in keeping it around?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/13/2021 03:24 am
Today's SN-20 leg skirt double (WO ä1642026) could be a do-over, as there already was another SN-20 leg skirt double (WO #1596856) earlier in March.

Could be a sign of an issue during outfitting of the skirt or changes needed for an updated staging interface with the booster.
Or new legs
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 04/13/2021 03:50 am
Cite please?  Based on previous tests, seems they get rid of it as soon after they are done--no sense in keeping it around?
Can you explain what you mean by then 'getting rid of it' as soon as they're done?  The amount of nitrogen vapor released after a cryotest seems a LOT less than what we saw during the various implosions.  As for 'no sense in keeping it around', draining it back into the liquid nitrogen storage tanks would seem very useful for their LOX chilling and other cryotests, not to mention the benefits of not needing to manage the logistics of having a bunch more trucks of liquid nitrogen shipped in.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/13/2021 04:03 am
If SN20 is an orbital vehicle, I wonder if SNs 16-18 might be slated for suborbital mach flights if a previous vehicle manages the landing on the current test trajectories, thus giving a purpose to the increased TPS coverage.
The TPS still looks to be a work in progress and not yet ready for high temp testing. Tile design, install technique and mechanical response at low thermal loads can be tested parallel to nailing the landing with neither interfering with the other.


In the blowup of BCG's pic we can see that the tiles are not of uniform size. The gap area is roughly along the center of curvature so there's perspective concerns for the image. Some of the tiles are a bit smaller but the gap around them is not symmetrical. The attachment points must be offset. The implied question is: is it the mounting points on the tiles that are wonkie or the pin placement? IMO robotic placement would have a tighter olerance than what we see here so my vote goes for wonkie tiles.


Why? Don't know much about tile fabrication so I'd like to think that it would have tighter tolerances than what we see here. But I don't really know. Maybe the offset is intentional for testing only.


The surface treatment seems to vary also. A question of batch control or another example of playing with it for experiments sake. Don't have an answer.


IMO, all the variation, intentional or not, means higher temp profiles are not on the SX radar. They'll do it when they're comfortable with it. In he meantime, expanding the array still makes good sense as a step towards full coverage.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/13/2021 04:03 am
Can you explain what you mean by then 'getting rid of it' as soon as they're done?  The amount of nitrogen vapor released after a cryotest seems a LOT less than what we saw during the various implosions.  As for 'no sense in keeping it around', draining it back into the liquid nitrogen storage tanks would seem very useful for their LOX chilling and other cryotests, not to mention the benefits of not needing to manage the logistics of having a bunch more trucks of liquid nitrogen shipped in.

Getting it out = out of the test article, or at least reducing it below critical levels. Did not opine on where it went... vent to atmosphere, pump back to storage?  No opinion; will leave that to SpaceX.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tater on 04/13/2021 04:09 am
The tile "variation" looks like variable tile set depth to me. Ie: the steel substrate/pins are not uniform above the surface*, so some tiles are a few mm higher or lower than their neighbors, showing the sides of the neighboring tile.

*perhaps better said, the steel surface the pins are attached to is not a perfect circle at any Starship hull cross section due to dents, etc. They might even self-correct once pressurized.'

EDIT: watching the YouTube vid, it looks like one of their tile molds is not so great, it's not a regular hexagon for at least 1 tile I saw.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/13/2021 04:17 am
...
3.  They normally don't dump that much nitrogen at once for cryo tests

Cite please?  Based on previous tests, seems they get rid of it as soon after they are done--no sense in keeping it around?

cite please these previous tests. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/13/2021 04:22 am
...
3.  They normally don't dump that much nitrogen at once for cryo tests

Cite please?  Based on previous tests, seems they get rid of it as soon after they are done--no sense in keeping it around?

Cite: SN10 cryoproof test.  No dump, just normal detanking:  https://www.youtube.com/watch?v=01j90yvN_tA

Dumping LN is unusual, since:

(a) SN10 cryo test has no nitrogen dump and
(b) the announcers in  today's broadcast for SN15 thought the LN dump was unusual
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/13/2021 04:39 am
We have exactly no idea on how they're doing the testing config. Remembered when people are seeing engine chill vent for the first time in SN4 and they reacted "holy moly, the LOX is leaking like waterfall!"

And the LN dump is coming from the pipe, so this isn't no way unexpected
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 04/13/2021 05:00 am
We have exactly no idea on how they're doing the testing config. Remembered when people are seeing engine chill vent for the first time in SN4 and they reacted "holy moly, the LOX is leaking like waterfall!"

And the LN dump is coming from the pipe, so this isn't no way unexpected

Don't forget SN15 has different plumbing, too. Tests may be different or more extensive.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Wolfram66 on 04/13/2021 05:02 am
SN15 has the revised thrust puck architecture, correct? Bleeds and dumps may look different with the changes to its nether regions, 🤔
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: YoannMoguer on 04/13/2021 09:01 am
Hello everyone. What are your thoughts on BN2 re-using tank parts from BN1? Scrapping all of those rings would be a waste of money/time/energy and I am pretty sure that the main differences between BN1 and BN2 are not located on the tanks (and remember SN4 reusing parts of the unfortunate SN3)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tyrred on 04/13/2021 09:16 am
Hello everyone. What are your thoughts on BN2 re-using tank parts from BN1? Scrapping all of those rings would be a waste of money/time/energy and I am pretty sure that the main differences between BN1 and BN2 are not located on the tanks (and remember SN4 reusing parts of the unfortunate SN3)

At this point, they gain better experience by starting with new build each time.

The build teams are refining/iterating the next big thing.

Plus Elon said something about BN1 already being obsolete - why reuse obsolete tankage in the journey towards flight booster? BN1 probably has multiple intrusions in it's rings in places that will not be exactly where they will be on BN2.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/13/2021 11:29 am
...
3.  They normally don't dump that much nitrogen at once for cryo tests

Cite please?  Based on previous tests, seems they get rid of it as soon after they are done--no sense in keeping it around?

Isn't this the first cleaning of the new tanks of the booster.
Essentially all the water, metal particles, welding oxides all cleaned out of the tank.
Sounds like a good idea to dump it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/13/2021 11:46 am
The trailer tyres are ST235/80R16, so for a 16" rim, the grid fin is about 4.65m long. The trailer width is 2.6m so it is around 2.4m wide. This is over 4 times the area of the Falcon 9 Ti grid fin, which is about 2.0 x 1.3m.

I may be wrong but wheel diameters are measured at the bead diameter which is inside of where you measured.
So I get 212 pixels for the 16" tire size.
3100/212*16in =5.94m
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/13/2021 11:57 am
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"

Plain carbon steel seems like a very strange material.
I doubt this is a flight article. It must be a production test article of some sort There are a lot of materials that would be better for this task. Plain steel is the worst of all worlds.

You can't tell what alloy it is by looking at it. It may save a little bit of money while they are still making craters, but it may also be the most economical material for the job. Aluminum alloys can't take the heat. Titanium might cost more than the whole booster. SpaceX has lots of data on what grid fins need to withstand for a returning booster.

wikipedia has:
titanium mp: 1668C
ss304 mp: 1450C
So 200C greater for Ti.
But ss304 has max temp mech of 710C
Ti "loses strength" over 410C
And
ss304 tensile is 1180MPa
Ti tensile is 434MPa

Altogether stainless seems vastly superior to Ti.
https://en.wikipedia.org/wiki/Titanium#Physical_properties
https://www.makeitfrom.com/material-properties/Half-Hard-304-Stainless-Steel
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/13/2021 11:57 am

Isn't this the first cleaning of the new tanks of the booster.
Essentially all the water, metal particles, welding oxides all cleaned out of the tank.
Sounds like a good idea to dump it.

The cleaning procedures for a methane tank are different, but there are specified, defined industry standards born of hard experience for cleaning LOX tanks. Flushing with LN2 is not sufficient.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/13/2021 11:59 am

Isn't this the first cleaning of the new tanks of the booster.
Essentially all the water, metal particles, welding oxides all cleaned out of the tank.
Sounds like a good idea to dump it.

The cleaning procedures for a methane tank are different, but there are specified, defined industry standards born of hard experience for cleaning LOX tanks. Flushing with LN2 is not sufficient.

Well maybe not the main cleaning then but isn't the best way to make sure there isn't any water in there is to flush with LN2?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/13/2021 12:57 pm
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"

Plain carbon steel seems like a very strange material.
I doubt this is a flight article. It must be a production test article of some sort There are a lot of materials that would be better for this task. Plain steel is the worst of all worlds.

You can't tell what alloy it is by looking at it. It may save a little bit of money while they are still making craters, but it may also be the most economical material for the job. Aluminum alloys can't take the heat. Titanium might cost more than the whole booster. SpaceX has lots of data on what grid fins need to withstand for a returning booster.

wikipedia has:
titanium mp: 1668C
ss304 mp: 1450C
So 200C greater for Ti.
But ss304 has max temp mech of 710C
Ti "loses strength" over 410C
And
ss304 tensile is 1180MPa
Ti tensile is 434MPa

Altogether stainless seems vastly superior to Ti.
https://en.wikipedia.org/wiki/Titanium#Physical_properties (https://en.wikipedia.org/wiki/Titanium#Physical_properties)
https://www.makeitfrom.com/material-properties/Half-Hard-304-Stainless-Steel (https://www.makeitfrom.com/material-properties/Half-Hard-304-Stainless-Steel)


Thought they already said they're using welded stainless steel for the booster grid fins.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/13/2021 01:00 pm
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"

Plain carbon steel seems like a very strange material.
I doubt this is a flight article. It must be a production test article of some sort There are a lot of materials that would be better for this task. Plain steel is the worst of all worlds.

You can't tell what alloy it is by looking at it. It may save a little bit of money while they are still making craters, but it may also be the most economical material for the job. Aluminum alloys can't take the heat. Titanium might cost more than the whole booster. SpaceX has lots of data on what grid fins need to withstand for a returning booster.

wikipedia has:
titanium mp: 1668C
ss304 mp: 1450C
So 200C greater for Ti.
But ss304 has max temp mech of 710C
Ti "loses strength" over 410C
And
ss304 tensile is 1180MPa
Ti tensile is 434MPa

Altogether stainless seems vastly superior to Ti.
https://en.wikipedia.org/wiki/Titanium#Physical_properties (https://en.wikipedia.org/wiki/Titanium#Physical_properties)
https://www.makeitfrom.com/material-properties/Half-Hard-304-Stainless-Steel (https://www.makeitfrom.com/material-properties/Half-Hard-304-Stainless-Steel)


Thought they already said they're using welded stainless steel for the booster grid fins.

Mostly responding to the dubbie etc who think steel is bad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/13/2021 01:04 pm
The grid fin just delivered on a trailer to Starbase is plain ol' steel. Stain-y steel. These fins will look amazing after a few cycles of temper coloring from reentry and oxidation from sitting out side. The mirror stainless, matte black tile and raw steel are really going sing.

To update: "Form follows function," How about: "The best aesthetics is no aesthetics?"

Plain carbon steel seems like a very strange material.
I doubt this is a flight article. It must be a production test article of some sort There are a lot of materials that would be better for this task. Plain steel is the worst of all worlds.

We've been told this is how they will be.  The current plan of record:

https://twitter.com/elonmusk/status/1179799146464628736
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/13/2021 01:24 pm

Isn't this the first cleaning of the new tanks of the booster.
Essentially all the water, metal particles, welding oxides all cleaned out of the tank.
Sounds like a good idea to dump it.

The cleaning procedures for a methane tank are different, but there are specified, defined industry standards born of hard experience for cleaning LOX tanks. Flushing with LN2 is not sufficient.

Well maybe not the main cleaning then but isn't the best way to make sure there isn't any water in there is to flush with LN2?
No.  First you're hoping none of the water freezes and sticks to any surface.  At LN2 temperatures water ice is perfectly happy to hang around indefinitely, so anything frozen onto surfaces or in nooks and crannies wouldn't be going anywhere.  Second, at LN2 temperatures water ice is just another mineral with hardness similar to things like quartz and feldspar - basically you've turned your water into sand (mechanically speaking, anyway).  Much better to just purge with dry GN2 and let evaporation do its work (conveniently, LN2 boil-off is very ).  Even better if you can warm gently while doing it (e.g., leave it out in the sun).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Cheapchips on 04/13/2021 01:46 pm
The SH grid fin doesn't have a double hinge like the F9 ones do.  I wonder what the folding design will look like?

Can they get away with not folding them on accent? 

Mid stack steering certainly sounds terrible from my ignorant perspective


Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/13/2021 04:30 pm

Isn't this the first cleaning of the new tanks of the booster.
Essentially all the water, metal particles, welding oxides all cleaned out of the tank.
Sounds like a good idea to dump it.

The cleaning procedures for a methane tank are different, but there are specified, defined industry standards born of hard experience for cleaning LOX tanks. Flushing with LN2 is not sufficient.

Well maybe not the main cleaning then but isn't the best way to make sure there isn't any water in there is to flush with LN2?
Nope. LN2 will freeze the water. After it drains the water melts and your back where you started. We've seen them with totes, presumably soap or detergent, near the access ports. I expect a good solid washdown and flush followed by alcohol or acetone in the methane tank, and whatever is called for in the O2 tank. Gotta make sure there are no organic left in the O2 tank. Final flush would be dry GN2.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ruct Cohle on 04/13/2021 05:55 pm
I have a question. Is it exactly stainless steel? If so, why is it covered? I don't think that grids need perfect weldability and corrosion resistance as Starship tanks do. They can be made from medium carbon UHSS steel. A source is BCG
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/13/2021 06:02 pm
I have a question. Is it exactly stainless steel? If so, why is it covered? I don't think that grids need perfect weldability and corrosion resistance as Starship tanks do. They can be made from medium carbon UHSS steel. A source is BCG
Yeah, looks like non-stainless steel to me.

Also, I kind of think these may be early test fins. That may explain why they don't have a second joint. The fins can just stay deployed for recovery tests.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/13/2021 06:45 pm
I have a question. Is it exactly stainless steel? If so, why is it covered? I don't think that grids need perfect weldability and corrosion resistance as Starship tanks do. They can be made from medium carbon UHSS steel. A source is BCG
Yeah, looks like non-stainless steel to me.

Also, I kind of think these may be early test fins. That may explain why they don't have a second joint. The fins can just stay deployed for recovery tests.

Even stainless steel will have significant corrosion on the outside if it's been forged.  This is then removed by grinding and polishing to make it smooth and shiny.

Also, I can't imagine why they wouldn't use stainless, even in a rough prototype.  My understanding is that the steel they're using for Starship is both cheap and easy to machine and weld, so why on earth would they introduce a variable like that without any particular reason?  The final fins are going to have to be pretty corrosion resistant since they're going to be one of the hottest spots on the vehicle as it reenters.

Flying up with fins deployed sounds like a bad idea to me.  It would be very aerodynamically unstable.  We're just seeing one part and not the whole mechanism, so it's probably premature to judge.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/13/2021 06:59 pm
The SH grid fin doesn't have a double hinge like the F9 ones do.  I wonder what the folding design will look like?

Can they get away with not folding them on accent? 

Mid stack steering certainly sounds terrible from my ignorant perspective
I was looking for the folding hinge and couldn't make one out. That said, Mary's pic shows a gap between the base of the fin and the inboard boxy structure. There's no sign of a hinge pin and a simple hinge there would not work without a clearance cut away at the hinge fin base.

Leaving the hinges fins deployed during assent would impose a lot of drag and opens up the possibility of shock impingement. It doesn't make sense. OTOH, no folding hinge would make them a lot stronger if they're used to grab SH in mid air on landing. Still, my methane producing gut says that landing leg mass would impose less penalty than fin drag on ascent. As happens so often, all I can say is WTF?

A late thought. Maybe a compromise position. Fins stay extended but rotated edge on to the air flow. Still a lot of drag, but less than flat on. Still sounds weird.


Edit: fixed hinge
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/13/2021 07:07 pm
It looks like the bridge crane handled it's first job OK.
 BN2 lower bulkhead was sleeved.

BN 1 falls but BN 2 rises!

What "design changes", like Elon Musk said have we seen?

About the grid fins, I would challeng the hypotesis that they are a pathfinder with different material. They could be a pathfinder, but sice AFAIU welding and working on stainless steel and normal steel si quite different why shoud they build a pathfinder with oneother material?

They couldbe a pathfinder, but I don't see reason to built them if they at the end will use stainless.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kazioo on 04/13/2021 07:37 pm
A late thought. Maybe a compromise position. Fins stay extended but rotated edge on to the air flow. Still a lot of drag, but less than flat on. Still sounds weird.

Two of these fins would be right behind Starship flaps, so maybe the total additional drag wouldn't so bad?

How about a mixed solution? Two grid fins without hinges in the positions were the flaps are and two classic grid fins with hinges, but only those without hinges are used for the catch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/13/2021 07:41 pm
Two of these fins would be right behind Starship flaps, so maybe the total additional drag wouldn't so bad?

How about a mixed solution? Two grid fins without hinges in the positions were the flaps are and two classic grid fins with hinges, but only those without hinges are used for the catch.

Starship has flaps; does not have grid fins.  Booster does not have flaps; has grid fins.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chevvie on 04/13/2021 07:57 pm
A late thought. Maybe a compromise position. Fins stay extended but rotated edge on to the air flow. Still a lot of drag, but less than flat on. Still sounds weird.

Two of these fins would be right behind Starship flaps, so maybe the total additional drag wouldn't so bad?

How about a mixed solution? Two grid fins without hinges in the positions were the flaps are and two classic grid fins with hinges, but only those without hinges are used for the catch.

I think musk said on Twitter they are using load points to catch the booster and not the grid fins.

Lemme see if i can find it... 

https://twitter.com/elonmusk/status/1380259201436422145
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: awests on 04/13/2021 08:01 pm
I have a question. Is it exactly stainless steel? If so, why is it covered? I don't think that grids need perfect weldability and corrosion resistance as Starship tanks do. They can be made from medium carbon UHSS steel. A source is BCG
Yeah, looks like non-stainless steel to me.

Also, I kind of think these may be early test fins. That may explain why they don't have a second joint. The fins can just stay deployed for recovery tests.

Even stainless steel will have significant corrosion on the outside if it's been forged.  This is then removed by grinding and polishing to make it smooth and shiny.

Also, I can't imagine why they wouldn't use stainless, even in a rough prototype.  My understanding is that the steel they're using for Starship is both cheap and easy to machine and weld, so why on earth would they introduce a variable like that without any particular reason?  The final fins are going to have to be pretty corrosion resistant since they're going to be one of the hottest spots on the vehicle as it reenters.

Flying up with fins deployed sounds like a bad idea to me.  It would be very aerodynamically unstable.  We're just seeing one part and not the whole mechanism, so it's probably premature to judge.
Agreed, not all stainless is supplied in a nice bright finish.
Maybe there is another structural actuation point within the fin that we can’t see from this view? I would imagine you would want to place the “deployment” attachment point further away from the rotational pivot point to use the mechanical advantage of a lever arm.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 04/13/2021 08:43 pm
The SH grid fin doesn't have a double hinge like the F9 ones do.  I wonder what the folding design will look like?

Can they get away with not folding them on accent? 

Mid stack steering certainly sounds terrible from my ignorant perspective
I was looking for the folding hinge and couldn't make one out. That said, Mary's pic shows a gap between the base of the fin and the inboard boxy structure. There's no sign of a hinge pin and a simple hinge there would not work without a clearance cut away at the hinge base.


Leaving the hinges deployed during assent would impose a lot of drag and opens up the possibility of shock impingement. It doesn't make sense. OTOH, no folding hinge would make them a lot stronger if they're used to grab SH in mid air on landing. Still, my methane producing gut says that landing leg mass would impose less penalty than fin drag on ascent. As happens so often, all I can say is WTF?


A late thought. Maybe a compromise position. Fins stay extended but rotated edge on to the air flow. Still a lot of drag, but less than flat on. Still sounds weird.

I’m not convinced that shock impingement on the way up is going to be significantly worse than on the way down?  There is also the weight penalty of the hinges and folding mechanism to set against the drag penalty. Maybe it’s close enough for simplicity to win the trade study.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ballistic_Reindeer on 04/13/2021 11:10 pm
Grid fin loaded onto flatbed at the production site.

Emphasis mine. Before we digress into a four page discussion regarding material of construction, design methodology and function, I'd like to politely call out that we've seen these before, and that they are LEAVING the build site.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barry Brisco on 04/13/2021 11:38 pm
I was looking for the folding hinge and couldn't make one out. That said, Mary's pic shows a gap between the base of the fin and the inboard boxy structure. There's no sign of a hinge pin and a simple hinge there would not work without a clearance cut away at the hinge base.

Leaving the hinges deployed during assent would impose a lot of drag and opens up the possibility of shock impingement. It doesn't make sense.
The grid fin pictured could be a a simplified design only intended to be used on BN2 for a “hop” test to a limited altitude.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 04/14/2021 12:13 am
Hello everyone. What are your thoughts on BN2 re-using tank parts from BN1? Scrapping all of those rings would be a waste of money/time/energy and I am pretty sure that the main differences between BN1 and BN2 are not located on the tanks (and remember SN4 reusing parts of the unfortunate SN3)

If you are going to try and find a 'second life' for the surplus BN1 sections then using them to make the inner tanks for the Orbital Launch Pad's GSE tank farm would make more sense.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 04/14/2021 12:32 am
Ring being moved at the propellant production site.

Is it me or does this ring looks like it might be 12 m in diameter? Considering where it is now, I would think quite possible.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Qau4 on 04/14/2021 01:22 am
Ring being moved at the propellant production site.

Is it me or does this ring looks like it might be 12 m in diameter? Considering where it is now, I would think quite possible.

I believe it is 12m iicr
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/14/2021 01:54 am
Ring being moved at the propellant production site.

Is it me or does this ring looks like it might be 12 m in diameter? Considering where it is now, I would think quite possible.
It's definitely 12m. They brought in Imcar tooling to make the outer skins for the GSE tanks at the orbital site, with the big domes to cap them off.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Legios on 04/14/2021 02:36 am
My understanding was that since Super Heavy staged much lower and slower than F9, that it would not be subject to the same thermal loads.

Not sure that thermals are driving grid fin material selection.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/14/2021 04:04 am
  A lot of ideas posted about grid fin material, deployment, stowage, etc. Can't offer any substantive input to those discussions. Rather, an observation about what can be seen from some of the great pictures provided by 'bocachicagal'.
  In looking at the pic from the Boca Chica Update Master Thread (and also reply #823 above) the shiny area on the perimeter with the 10 bolts is very interesting. It has a very thick transverse plate going from one side to the other (see enlargement provided). The main body of the fin has a diagonal waffle structure like the  Falcon 9 fins. It is hard to determine the pattern from the root to the main body of the fin. It appears that at the point the grid fin reaches max width is where the thick transverse plate has been put in. Zoom in on the original picture and study the amount of finish work on the inboard side of the grid fin in this area. The level of finish hints at pieces that have been machined. Very intrigued by the use of 10 closely spaced bolts that tie into the transverse plate assembly.
  Yes, it is a prototype and many engineering and fabrication ideas are in play here, but it would be great to hear the reasons behind using the massive bolts at the root of the grid fin.

Enlargement of photo #1 from BC Production Updates Master Thread, post #1244 credit "bocachicagal".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OneSpeed on 04/14/2021 08:42 am
I may be wrong but wheel diameters are measured at the bead diameter which is inside of where you measured.
So I get 212 pixels for the 16" tire size.
3100/212*16in =5.94m

You're right, I didn't look closely enough, and measured the diameter at some smudges on the tyre, not the actual rim! That makes it 5½ times the area of the Falcon 9 Ti fin.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: warp99 on 04/14/2021 10:35 am
My understanding was that since Super Heavy staged much lower and slower than F9, that it would not be subject to the same thermal loads.

Not sure that thermals are driving grid fin material selection.
.
It seems unlikely that SH will stage lower and slower than the F9 booster.  Yes SH is doing RTLS but they will be skipping the re-entry burn so can use more of the propellant during the ascent phase and have much higher Isp engines so get more delta V from a given mass of propellant. 

So they should stage a bit higher and significantly faster than F9.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/14/2021 12:05 pm
A late thought. Maybe a compromise position. Fins stay extended but rotated edge on to the air flow. Still a lot of drag, but less than flat on. Still sounds weird.

Two of these fins would be right behind Starship flaps, so maybe the total additional drag wouldn't so bad?

How about a mixed solution? Two grid fins without hinges in the positions were the flaps are and two classic grid fins with hinges, but only those without hinges are used for the catch.
There's some sense here but for one point. Extended fins directly below the flaps would catch shock impingement from the flaps. The fins are designed to create shock with the grid structure allow shocks to pass through without impingement. They're not designed to take shock from elsewhere (I think).

Rotate your idea 90deg and folding fins are below the flaps. This could work.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/14/2021 12:41 pm
The SH grid fin doesn't have a double hinge like the F9 ones do.  I wonder what the folding design will look like?

Can they get away with not folding them on accent? 

Mid stack steering certainly sounds terrible from my ignorant perspective
I was looking for the folding hinge and couldn't make one out. That said, Mary's pic shows a gap between the base of the fin and the inboard boxy structure. There's no sign of a hinge pin and a simple hinge there would not work without a clearance cut away at the hinge base.


Leaving the hinges deployed during assent would impose a lot of drag and opens up the possibility of shock impingement. It doesn't make sense. OTOH, no folding hinge would make them a lot stronger if they're used to grab SH in mid air on landing. Still, my methane producing gut says that landing leg mass would impose less penalty than fin drag on ascent. As happens so often, all I can say is WTF?


A late thought. Maybe a compromise position. Fins stay extended but rotated edge on to the air flow. Still a lot of drag, but less than flat on. Still sounds weird.

I’m not convinced that shock impingement on the way up is going to be significantly worse than on the way down?  There is also the weight penalty of the hinges and folding mechanism to set against the drag penalty. Maybe it’s close enough for simplicity to win the trade study.
Yes, shock on the way down will be much worse than on the way up. The difference is on the way up the shock will trail back along the tanks with impingement on the tanks. On the way down the shock will be streaming (probably not the right word) up into free space and impinge on nothing. Maybe the grids can be canted very slightly to keep shock off the tanks. DIIK. (Damn If I Know)


And yes, those grid fins are monsters. A hinge would be a serious chunk of metal. And I've a hunch that pic was only the fin root. Maybe only a half or a third of the full length. Simple does have its attractions. I'm not sure Buck Rogers would approve of no legs.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barnalby on 04/14/2021 01:22 pm
An observation vis a vis the lock of stainless on the fins is that if they're going to be used to catch Starship, carrying that sort of weight in an extremely dynamic and unpredictable manner, then it probably makes sense to build them from some alloy that possesses a great deal more ductility than the relatively brittle stainless that the rest of Starship is constructed of.  The sort of steel that they build truck frames and construction equipment out of. 

Steel with those properties is almost certainly going to be some sort of decidedly non-stainless steel.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hallmh on 04/14/2021 01:36 pm

I'm rather late to this very interesting party, so I may have misunderstood something; perhaps someone can enlighten me?

It seems to me that some here are assuming Starship will have grid fins. Surely that would be redundant - it has the four flaps, plus gimballing Raptors, to guide it to a precise landing. That would mean the grid fins we're seeing are only intended for Superheavy.

If, as seems likely, SpaceX intend to catch Starship with the launch tower, they won't need anything more elaborate than arms that will open out from the nosecone. They could even use the trailing edges of the forward flaps for the purpose, although that would require beefing up its hinges quite a bit.

As I say, I may have missed the point entirely!

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 04/14/2021 01:48 pm
SuperHeavy has the grid fins, not SS (the 2nd stage)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/14/2021 02:06 pm
An observation vis a vis the lock of stainless on the fins is that if they're going to be used to catch Starship, carrying that sort of weight in an extremely dynamic and unpredictable manner, then it probably makes sense to build them from some alloy that possesses a great deal more ductility than the relatively brittle stainless that the rest of Starship is constructed of.  The sort of steel that they build truck frames and construction equipment out of. 

Steel with those properties is almost certainly going to be some sort of decidedly non-stainless steel.
Catching the booster by the grid fins is no longer the plan, it will be caught on dedicated load points below the grid fins.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/14/2021 02:24 pm
An observation vis a vis the lock of stainless on the fins is that if they're going to be used to catch Starship, carrying that sort of weight in an extremely dynamic and unpredictable manner, then it probably makes sense to build them from some alloy that possesses a great deal more ductility than the relatively brittle stainless that the rest of Starship is constructed of.  The sort of steel that they build truck frames and construction equipment out of. 

Steel with those properties is almost certainly going to be some sort of decidedly non-stainless steel.
Catching the booster by the grid fins is no longer the plan, it will be caught on dedicated load points below the grid fins.
It doesn't change your point but I envision the grid fins still playing a part w.r.t. being the initial point of engagement for the mechanism that will close on those load points.  It seems likely you want to have the catching mechanism match vertical velocity with SH by engagement with the grid fins then closing clamps on load points quickly with relative velocity of zero even though the booster has yet to stop falling.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barnalby on 04/14/2021 02:40 pm
And I wouldn't be surprised if the grid fins serve as a sort of secondary fallback if the catching mechanism doesn't properly engage with the dedicated hardpoints.

Point is that you'll want a variety of steel with a bit more "spring" in it than stainless for that job.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/14/2021 02:58 pm
Does anyone know what happens to the scrapped Raptors and Starships/boosters? Who does SpaceX sell the scrap to, etc?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/14/2021 02:59 pm
An observation vis a vis the lock of stainless on the fins is that if they're going to be used to catch Starship, carrying that sort of weight in an extremely dynamic and unpredictable manner, then it probably makes sense to build them from some alloy that possesses a great deal more ductility than the relatively brittle stainless that the rest of Starship is constructed of.  The sort of steel that they build truck frames and construction equipment out of. 

Steel with those properties is almost certainly going to be some sort of decidedly non-stainless steel.
Catching the booster by the grid fins is no longer the plan, it will be caught on dedicated load points below the grid fins.
It doesn't change your point but I envision the grid fins still playing a part w.r.t. being the initial point of engagement for the mechanism that will close on those load points.  It seems likely you want to have the catching mechanism match vertical velocity with SH by engagement with the grid fins then closing clamps on load points quickly with relative velocity of zero even though the booster has yet to stop falling.

Yes the load points should be very close to the grid fins because they have internal strengthening for the grid fins and the load points will be able to take advantage of the extra strength in that area.
 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/14/2021 03:07 pm
Does anyone know what happens to the scrapped Raptors and Starships/boosters? Who does SpaceX sell the scrap to, etc?

Don't know about the tanking, but I bet the scrapped Raptors are sent to a secure destruction vendor for ITAR purposes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsnellenberger on 04/14/2021 03:12 pm
Yes the load points should be very close to the grid fins because they have internal strengthening for the grid fins and the load points will be able to take advantage of the extra strength in that area.
That, and this hardware probably all wants to be located in/attached-to the “quasi-interstage” ring at the top of the booster anyway, not the tank.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/14/2021 03:48 pm
SN15 with a few extra tiles.
Did they put more tiles on at the launch site, or were these all on when it was moved down the road?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/14/2021 04:09 pm
Does anyone know what happens to the scrapped Raptors and Starships/boosters? Who does SpaceX sell the scrap to, etc?

I would bet that the scrapped steel gets returned to the steel works and chomped up.  One of the ingredients in steel making is chunks of scrap steel.  It helps start the right crystal formation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vanspace on 04/14/2021 04:10 pm
My understanding was that since Super Heavy staged much lower and slower than F9, that it would not be subject to the same thermal loads.

Not sure that thermals are driving grid fin material selection.
.
It seems unlikely that SH will stage lower and slower than the F9 booster.  Yes SH is doing RTLS but they will be skipping the re-entry burn so can use more of the propellant during the ascent phase and have much higher Isp engines so get more delta V from a given mass of propellant. 

So they should stage a bit higher and significantly faster than F9.

You missed something in your reasoning. They don't skip the re-entry burn. They do a boost-back burn which covers the slowdown for re-entry burn and is extended to a much longer burn to reverse direction.

Tl;DR  RLTS boost-back requires MORE fuel than landing downrange via re-entry burn.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/14/2021 04:21 pm
SN15 with a few extra tiles.
Did they put more tiles on at the launch site, or were these all on when it was moved down the road?

No, from pictures seems they added a square of tiles between yesterday and today.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/14/2021 05:16 pm
My understanding was that since Super Heavy staged much lower and slower than F9, that it would not be subject to the same thermal loads.

Not sure that thermals are driving grid fin material selection.
.
It seems unlikely that SH will stage lower and slower than the F9 booster.  Yes SH is doing RTLS but they will be skipping the re-entry burn so can use more of the propellant during the ascent phase and have much higher Isp engines so get more delta V from a given mass of propellant. 

So they should stage a bit higher and significantly faster than F9.

You missed something in your reasoning. They don't skip the re-entry burn. They do a boost-back burn which covers the slowdown for re-entry burn and is extended to a much longer burn to reverse direction.

Tl;DR  RLTS boost-back requires MORE fuel than landing downrange via re-entry burn.
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barry Brisco on 04/15/2021 12:08 am
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 04/15/2021 12:37 am
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?

- From Elon. SH stainless steel will be able to handle the heat. F9 Aluminum would not.

John
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ZChris13 on 04/15/2021 01:23 am
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?
I have gleaned from Elon tweets that it is a core requirement of Super Heavy from the very beginning. The Falcon 9 reentry burn was a compromise that SpaceX does not feel is necessary in a clean sheet design.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/15/2021 03:02 am
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?
I have gleaned from Elon tweets that it is a core requirement of Super Heavy from the very beginning. The Falcon 9 reentry burn was a compromise that SpaceX does not feel is necessary in a clean sheet design.

Watching the SpaceX navy grow and how long it takes to get the F9 boosters back to port, you can see why Elon wants the Launch tower to catch the booster.

It could be back on the launch mount in minutes or hours not a month.  Payload penalty be dammed, get more flights.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bkent136 on 04/15/2021 12:25 pm
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?
I have gleaned from Elon tweets that it is a core requirement of Super Heavy from the very beginning. The Falcon 9 reentry burn was a compromise that SpaceX does not feel is necessary in a clean sheet design.

Watching the SpaceX navy grow and how long it takes to get the F9 boosters back to port, you can see why Elon wants the Launch tower to catch the booster.

It could be back on the launch mount in minutes or hours not a month.  Payload penalty be dammed, get more flights.
I may have missed something, but why would catching the booster cause a payload penalty? I would think you could increase payload slightly, as the booster doesn't have to carry the mass of landing legs, and instead just some load points aft of the gridfins.

Edit: or are you talking about RTLS being the cause of the payload penalty? That has nothing to do with the tower catching the booster.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/15/2021 01:38 pm

So currently no road closures scheduled. Expect some will appear for static fire etc soon.

I think we’ll need to see Raptors installed before they request road closures, no?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 04/15/2021 01:41 pm
Landing downrange the booster doesn't have to boost back to the launch site.  Boosting back requires saving some extra fuel to do so, thus the payload penalty.  F9 lands on droneships to avoid the boost back burn so they can launch 60 Starlink satellites.  Otherwise they may not be able to launch but 50 or less. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ppb on 04/15/2021 03:10 pm
I read somewhere that they could only launch 40 for F9 RTLS.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 04/15/2021 03:17 pm
I read somewhere that they could only launch 40 for F9 RTLS.
A new ASDS is being purpose built for VAFB launches. Scott Manley also states rumours that ASOG is now going to debut on the west coast fleet. Other ASDS's are to be built after 4E is upgraded to conduct modernized F9 and FH operations at an increased flight rate. ASOG is supposed to debut this summer at the earliest.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/15/2021 03:51 pm
https://youtu.be/Sv269e1O2Ik
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/15/2021 04:46 pm
I read somewhere that they could only launch 40 for F9 RTLS.
A new ASDS is being purpose built for VAFB launches. Scott Manley also states rumours that ASOG is now going to debut on the west coast fleet. Other ASDS's are to be built after 4E is upgraded to conduct modernized F9 and FH operations at an increased flight rate. ASOG is supposed to debut this summer at the earliest.

I need a dictionary to understand all the acronyms.  I know what RTLS is.  What are ASOG and ASDS?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/15/2021 04:50 pm
I read somewhere that they could only launch 40 for F9 RTLS.
A new ASDS is being purpose built for VAFB launches. Scott Manley also states rumours that ASOG is now going to debut on the west coast fleet. Other ASDS's are to be built after 4E is upgraded to conduct modernized F9 and FH operations at an increased flight rate. ASOG is supposed to debut this summer at the earliest.

I need a dictionary to understand all the acronyms.  I know what RTLS is.  What are ASOG and ASDS?

ASDS = Autonomous Spaceport Drone Ship
ASOG = A Shortfall of Gravitas (another Iain M. Banks reference, like the other drone ships)

For reference:

JRTI = Just Read the Instructions
OCISLY = Of Course I Still Love You

Edit...
There is a good Wikipedia article (https://en.wikipedia.org/wiki/Autonomous_spaceport_drone_ship) with more information about the various drone ships.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ronatu on 04/15/2021 06:53 pm
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?
I have gleaned from Elon tweets that it is a core requirement of Super Heavy from the very beginning. The Falcon 9 reentry burn was a compromise that SpaceX does not feel is necessary in a clean sheet design.

Watching the SpaceX navy grow and how long it takes to get the F9 boosters back to port, you can see why Elon wants the Launch tower to catch the booster.

It could be back on the launch mount in minutes or hours not a month.  Payload penalty be dammed, get more flights.

No reentry burn???
How they plan to get back to launch pad??
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 04/15/2021 06:58 pm
They aren't comparing downrange to RTLS landings. They are comparing F9 RTLS to SH RTLS. Falcon 9 has to do both a boostback and an entry burn. Superheavy will only do a boostback, skipping the entry burn.
Sorry, I missed this bit of info. How do we know that SH is not doing an entry burn?
I have gleaned from Elon tweets that it is a core requirement of Super Heavy from the very beginning. The Falcon 9 reentry burn was a compromise that SpaceX does not feel is necessary in a clean sheet design.

Watching the SpaceX navy grow and how long it takes to get the F9 boosters back to port, you can see why Elon wants the Launch tower to catch the booster.

It could be back on the launch mount in minutes or hours not a month.  Payload penalty be dammed, get more flights.

No reentry burn???
How they plan to get back to launch pad??


The three possible burns are:

Boostback (to get on target to the launch pad)
Entry (to keep from getting crushed/heated by atmospheric entry)
Landing (to land)

They want to do Boostback and Landing, but not Entry.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/15/2021 07:08 pm
No reentry burn???
How they plan to get back to launch pad??

There are two types of burns that rtls f9 does, boostback burn and reentry burn. Boostback burn is to cancel out horizontal velocity and add some velocity in the direction of launchsite so ballistic trajectory is close to lauchsite. Reentry burn is later, and only slows down f9 just before reentering atmosphere so reentry heating is reduced. Superheavy will be most likely more capable of dealing with reentry heat so reentry burn might not be needed but it will have to do boostback burn most likely. Also spacex boosters can somewhat "fly" in atmosphere using gridfins, but most of horizontal velocity has to be acquired by boostback burn.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 04/15/2021 11:09 pm
I asked over in L2 (what a resource!) for a reference and was directed to this thread:

https://forum.nasaspaceflight.com/index.php?topic=49127.msg1999201#msg1999201

EM's comment on SH's entry profile: it's at the very end of the presentation, and essentially he hopes to avoid the entry burn.  Nothing more definitive than a hope.  So I'd say the jury is still out on entry burn.

Have a good one,
Mike
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ionmars on 04/15/2021 11:09 pm
No reentry burn???
How they plan to get back to launch pad??

The three possible burns are:

Boostback (to get on target to the launch pad)
Entry (to keep from getting crushed/heated by atmospheric entry)
Landing (to land)

They want to do Boostback and Landing, but not Entry.
Add: As said by Lee Jay, the boostback burn will align the SH booster towards the landing pad. This  also involves re-entry into the atmosphere. Continued steering towards the pad will be accomplished by the grid fins, which saves fuel compared to a continued burn. The final landing burn will guide the vehicle accurately and gently onto the pad.

Starship in orbit will be traveling much faster, so an entry burn will be required to de-orbit and re-enter the atmosphere.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/15/2021 11:56 pm
I asked over in L2 (what a resource!) for a reference and was directed to this thread:

https://forum.nasaspaceflight.com/index.php?topic=49127.msg1999201#msg1999201

EM's comment on SH's entry profile: it's at the very end of the presentation, and essentially he hopes to avoid the entry burn.  Nothing more definitive than a hope.  So I'd say the jury is still out on entry burn.

Have a good one,
Mike

Thanks for that question and pointing out the answer: it's aspirational, not definite.

There's more to the F9 entry burn than simply slowing down the vehicle (which it most definitely does). The exhaust gases also create sort of an extended bowshock for the tail section of the vehicle at a key point in the descent; the stagnation point for the entering vehicle is moved further away from the vehicle by the exhaust gases, and those gases themselves serve to help insulate the aft end of the vehicle from some of the radiant and convective heat flux of entry. Absent the re-entry burn, the entire aft section will be exposed to very, very high thermal loads all the way through the worst parts of the entry profile.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: r8ix on 04/16/2021 01:05 am
Anybody catch serial #s on those 3 Raptors?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sucramdi on 04/16/2021 01:06 am
Anybody catch serial #s on those 3 Raptors?

Quote
Raptors sn# 54, 61, 66

https://twitter.com/spacepadreisle/status/1382861560129855491?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: TomH on 04/16/2021 01:33 am
I need a dictionary to understand all the acronyms.

Here ya go:

https://forum.nasaspaceflight.com/index.php?topic=34802.0

http://www.allacronyms.com
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: r8ix on 04/16/2021 01:36 am
Anybody catch serial #s on those 3 Raptors?

Quote
Raptors sn# 54, 61, 66

https://twitter.com/spacepadreisle/status/1382861560129855491?
Thanks. It wasn't there until the edit, in my defense...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/16/2021 02:16 am
The hijinks continue: "New Raptor, Who Dis?" Credit Lab Padre
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/16/2021 12:40 pm
I would be really surprised if SN15 flies in the same week as the Crew Dragon launch. I think they are aiming for launch readiness in case Crew Dragon gets delayed for any reason. Just a hunch based on past planning.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 04/16/2021 12:42 pm
They are different teams with different resources.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ETurner on 04/16/2021 12:46 pm
There's more to the F9 entry burn than simply slowing down the vehicle (which it most definitely does). The exhaust gases also create sort of an extended bowshock for the tail section of the vehicle at a key point in the descent; the stagnation point for the entering vehicle is moved further away from the vehicle by the exhaust gases, and those gases themselves serve to help insulate the aft end of the vehicle from some of the radiant and convective heat flux of entry. Absent the re-entry burn, the entire aft section will be exposed to very, very high thermal loads all the way through the worst parts of the entry profile.
If the purpose of an SH entry burn would be to move the bow shock away rather than to decelerate the vehicle, it may be that a single deeply throttled engine would suffice (the requirements are not obvious). Since the burn would be relatively brief and low-thrust, the propellant cost might be quite modest.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 04/16/2021 12:56 pm
The point is, SH not having an entry burn is not a done deal; it may/may not have one.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rockets4life97 on 04/17/2021 01:08 am
It seems like 2.9 billion from NASA for the lunar lander will help speed Starship development.

What can SpaceX spend money on to speed things up? More engineers to work on second and third order development needs?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ericgu on 04/17/2021 03:00 am
My understanding was that since Super Heavy staged much lower and slower than F9, that it would not be subject to the same thermal loads.

Not sure that thermals are driving grid fin material selection.
.
It seems unlikely that SH will stage lower and slower than the F9 booster.  Yes SH is doing RTLS but they will be skipping the re-entry burn so can use more of the propellant during the ascent phase and have much higher Isp engines so get more delta V from a given mass of propellant. 

So they should stage a bit higher and significantly faster than F9.

I did some approximate calculations based on estimates of Starship/Super Heavy and what we know about Falcon 9.

Starship with 100 tons penciled in with about the same delta v as the Falcon 9 with a starlink payload does. So I expect them to stage at pretty much the same sort of spot.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/17/2021 03:18 am
I did some approximate calculations based on estimates of Starship/Super Heavy and what we know about Falcon 9.

Starship with 100 tons penciled in with about the same delta v as the Falcon 9 with a starlink payload does. So I expect them to stage at pretty much the same sort of spot.

I suspect that something is wrong in your calculations, starship should have 1km/s more delta v available than f9 second stage uses for starlink launches.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: marokrile on 04/17/2021 04:41 am
https://twitter.com/SpaceX/status/1383160370248896512
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: marokrile on 04/17/2021 04:49 am
Latest design, smaller landing engines, and solar aray
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: marokrile on 04/17/2021 04:52 am
and Moon Tesla Quad
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: volker2020 on 04/17/2021 12:42 pm
It seems like 2.9 billion from NASA for the lunar lander will help speed Starship development.

What can SpaceX spend money on to speed things up? More engineers to work on second and third order development needs?

There is quite some overlapping here. In Orbit Refueling will be part of the project, likely hot gas thrusters (unless they scrapped those), live support systems for Spaceship, human interfaces, interior ... Quite a lot of useful stuff that perfectly align with SpaceX long term plans.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ilias Pap on 04/17/2021 10:15 pm
https://twitter.com/starshipgazer/status/1383471055700840448

Quote
Raptor #61 a couple of minutes before being lifted into Starship SN15:

All three raptors are now installed on sn15

No they are not this was the first installed just a later tweet (he answers that in a comment)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: maquinsa on 04/17/2021 10:18 pm
https://twitter.com/starshipgazer/status/1383471055700840448

Quote
Raptor #61 a couple of minutes before being lifted into Starship SN15:

All three raptors are now installed on sn15

No they are not this was the first installed just a later tweet (he answers that in a comment)

Sorry, my error
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/17/2021 11:23 pm
Latest production update looks like SN20 is getting a lot more love than SN19.

Looks like 19 is going to get skipped.  I wonder if 18 or even 17 may also get jumped.

It’s amazing that we are seeing SN20 parts and that this maybe the first orbital vehicle.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/17/2021 11:32 pm
https://twitter.com/lrocket/status/1383139742397517825

Quote
Years ago people would tell me there is no business case for Starship how will you pay for it and my answer was Lunar missions

twitter.com/nasaspaceflight/status/1383141876392468483

Quote
Still think Point to Point could become a cash cow and would also be a game-changer.

I tend to go on about my love for Point to Point at least every second day, however. 😅

https://twitter.com/lrocket/status/1383558817628057600

Quote
Agree the real money longer term could be space tourism and point to point but lunar is the path to up-front development investment (govt)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DistantTemple on 04/18/2021 12:31 am
Will SX's new status as NASA's HLS contractor ease timely acquisition of permitting for related Earth-side infrastructure development, for example at BC and The Cape?
Will it be easier for SX to build the SS/SH launch and handling facilities at 39A etc... and if SS and SH are to be manufactured at Roberts Road, then are any road alterations needed for SPMT transit to 39A etc. With environmental reviews, there is the "no action alternative", which could be pretty severe if it consisted of "the Artemins program will be put on hold without this approval!".
Will it make it easier for the FAA to provide inspection staff at the "drop of a hat", or pay for them to wait a few days in Brownsville????
ISTM this HLS award moves SX solidly into the mainstream. Developments at BC are now part of a National Priority, despite being a private business.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 04/18/2021 01:40 am
For further discussion of the HLS Lunar Starship
https://forum.nasaspaceflight.com/index.php?topic=50806.new#new
 :)
Mostly doesn't belong on the Prototype thread
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/18/2021 07:48 am
Latest production update looks like SN20 is getting a lot more love than SN19.

Looks like 19 is going to get skipped.  I wonder if 18 or even 17 may also get jumped.

It’s amazing that we are seeing SN20 parts and that this maybe the first orbital vehicle.

That is possible, but an update on SpaceX website said that they have 5 prototypes inproduction: SN16, 17,18,19,20
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/18/2021 08:22 am
Latest production update looks like SN20 is getting a lot more love than SN19.

Looks like 19 is going to get skipped.  I wonder if 18 or even 17 may also get jumped.

It’s amazing that we are seeing SN20 parts and that this maybe the first orbital vehicle.

That is possible, but an update on SpaceX website said that they have 5 prototypes inproduction: SN16, 17,18,19,20

Didn't it say five vehicles? I'd think that could include BN2 / BN3, which would allow for SN19 and maybe 18 to be skipped.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 04/18/2021 08:23 am
Also, SN15 is technically still in production and should therefore count, too...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lampyridae on 04/18/2021 08:45 am
Latest production update looks like SN20 is getting a lot more love than SN19.

Looks like 19 is going to get skipped.  I wonder if 18 or even 17 may also get jumped.

It’s amazing that we are seeing SN20 parts and that this maybe the first orbital vehicle.

That is possible, but an update on SpaceX website said that they have 5 prototypes inproduction: SN16, 17,18,19,20

The reason why SN20 is skipping the queue so to speak is probably because it has a different test role.

SN15-19 are for testing the belly flop and landing flip. There will be iterative changes so they may be holding off on SN19 in case they want to implement more widespread (likely mostly invisible) structural changes or manufacturing techniques. Or it might just be scrapped if SN15-18 perform beautifully.
SN20-25? are for testing orbital flight and re-entry, SpaceX is not expecting them to land, it would just be nice if they did. But they do need to function in orbit, and have a full TPS so there is a longer lead time on them. SN21 might incorporate changes based on SN15-19 so you might see that only kicking off once SN19 is fully under way.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 01:48 pm
Quote from: Lampyridae link=topic=53471.msg2222637#msg2222637
SN20-25? are for testing orbital flight and re-entry, SpaceX is not expecting them to land, it would just be nice if they did. But they do need to function in orbit, and have a full TPS so there is a longer lead time on them. SN21 might incorporate changes based on SN15-19 so you might see that only kicking off once SN19 is fully under way.

I agree.  I also think that SN20 represents the "baseline" for an orbital vehicle in terms of strength.  So I expect SN21 to be manufactured only after the learnings from SN20...plus additional learnings from stress testing using the testing rig.

My thoughts are that the cadence of testing orbital vehicles Sn20+ is going to slow down somewhat from the current pace.  They may end up continuing to test sub-orbital landing prototypes in parallel with orbital launches / tests.

They are going to now also need to start testing LEO refueling in earnest.  They may choose to create initial test/prototype vehicles for that with no intention of returning them to Earth...(no TPS / re-entry)...so that offers another potentially parallel prototype path.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: deadman1204 on 04/18/2021 02:24 pm
It would have to.  Until they can safely land a booster, they'll be super limited
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 02:38 pm
It'll be interesting if the first orbital test will include (for the booster)

a) Intentional soft landing out at sea
b) Attempt to RTLS and land on legs
c) Attempt to RTLS and land via "catch"

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/18/2021 02:48 pm
Also, SN15 is technically still in production and should therefore count, too...

I thought this while posting my previous post, but I took "in production" as in active construction, not constructed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 04/18/2021 02:49 pm
They are going to now also need to start testing LEO refueling in earnest.
I think they will want to work all the kinks out while doing Starlink launches.  I really can't imagine them starting parallel work on a fuel tanker prototype until they are satisfied with the base version, although components of the refueling system may already be in development.  More interesting question might be where those refueled vehicles would be headed.  Before September 2022 maybe Mars.  If they miss that window, probably the moon.  Don't know about high earth orbit.

EDIT:  Refueling will most likely require offshore launch platforms so they need to be readied also.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 03:01 pm
EDIT:  Refueling will most likely require offshore launch platforms so they need to be readied also.

Ultimately, I agree (for production refueling to capacity...requiring multiple launches and therefore launched offshore).

However, for initial tests I don't think they need to launch multiple tankers: just two. One recipient vehicle in orbit...and a second tanker vehicle launched that they can run several tests with.  They can even run multiple dockings / propellant transfers with the same tanker.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 04/18/2021 03:47 pm
It'll be interesting if the first orbital test will include (for the booster)

a) Intentional soft landing out at sea
b) Attempt to RTLS and land on legs
c) Attempt to RTLS and land via "catch"
I've seen option a 'floated' (sorry) pretty often, has anything SpaceX has done during the Starship process suggested this fits their strategy?  Maybe I'm missing something, but unlike the first tentative Falcon landing dry-runs (for values of dry) where they sea-landed boosters, it seems like they've adopted a fairly aggressive strategy of allowing for success even if it involves some risk to ground infrastructure.

The most powerful example of this I can think of is the flight of SN8; the skydiver+flip maneuver was full of brand new concepts in a way a landing Superheavy profile doesn't yet they still aimed it at their launch/landing site and give it a shot. 

With all the Falcon landing legacy, it seems like aiming for recovery on that first Superheavy return fits their model much better than an intentional water-ditching.  To that point, I think even a legs-landing on that first attempt seems unlikely unless it's because of external factors (like the tower isn't ready to catch it).

As I said, I may be missing something and even though I can see the risks of attempting this, they seem modest compared to the SN8 decision.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 04:15 pm
It'll be interesting if the first orbital test will include (for the booster)

a) Intentional soft landing out at sea
b) Attempt to RTLS and land on legs
c) Attempt to RTLS and land via "catch"
I've seen option a 'floated' (sorry) pretty often, has anything SpaceX has done during the Starship process suggested this fits their strategy?  Maybe I'm missing something, but unlike the first tentative Falcon landing dry-runs (for values of dry) where they sea-landed boosters, it seems like they've adopted a fairly aggressive strategy of allowing for success even if it involves some risk to ground infrastructure.

The most powerful example of this I can think of is the flight of SN8; the skydiver+flip maneuver was full of brand new concepts in a way a landing Superheavy profile doesn't yet they still aimed it at their launch/landing site and give it a shot. 

With all the Falcon landing legacy, it seems like aiming for recovery on that first Superheavy return fits their model much better than an intentional water-ditching.  To that point, I think even a legs-landing on that first attempt seems unlikely unless it's because of external factors (like the tower isn't ready to catch it).

As I said, I may be missing something and even though I can see the risks of attempting this, they seem modest compared to the SN8 decision.

I think you're missing two things:
1) There is / will be a LOT more infrastructure in place once they are ready for an orbital launch...so there is much more to lose with a ill-placed RUD.
2) Even though the SN8 flip maneuver was high risk...the flight profile up to that point was pretty simple.

While SpaceX now has obviously a ton of data with respect to boostback burns, reentry and landing flightpaths...I think the Super Heavy is of such a different scale that they will want at least one soft water landing before attempting to land a booster back at the launch site. 

One big difference between Falcon 9 and Super Heavy is that the SH will not have a re-entry burn...and that probably has enough unknowns in and of itself to warrant a water landing for at least the first attempt.

All IMO of course!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/18/2021 04:20 pm
The last crop of posts are vastly off-topic for this thread. The General Engineering thread, Fleets and Facilities forum etc are better fits for this kind of general kibitzing about plans and flight profiles for future orbital operations.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 04/18/2021 04:26 pm
EDIT:  Refueling will most likely require offshore launch platforms so they need to be readied also.

Ultimately, I agree (for production refueling to capacity...requiring multiple launches and therefore launched offshore).

However, for initial tests I don't think they need to launch multiple tankers: just two. One recipient vehicle in orbit...and a second tanker vehicle launched that they can run several tests with.  They can even run multiple dockings / propellant transfers with the same tanker.

Maybe.  Don't know much about delta-V, but what about a single fuel transfer for a circumlunar trajectory?  Could theoretically happen from Boca or launches both from Boca and offshore.  Might also be a good benchmark for NASA.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 04:30 pm
The last crop of posts are vastly off-topic for this thread. The General Engineering thread, Fleets and Facilities forum etc are better fits for this kind of general kibitzing about plans and flight profiles for future orbital operations.
I don't see how the so called "kibitzing" about SS / SH belongs in a forum other than this one...you know, the "SH / SS" forum.

That being said, I will refrain from further said kibitzing in this particular thread within this forum....even if it is painfully unclear what does and does not "belong" in a "discussion" thread about the "Texas prototypes".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/18/2021 05:04 pm
The last crop of posts are vastly off-topic for this thread. The General Engineering thread, Fleets and Facilities forum etc are better fits for this kind of general kibitzing about plans and flight profiles for future orbital operations.
I don't see how the so called "kibitzing" about SS / SH belongs in a forum other than this one...you know, the "SH / SS" forum.

That being said, I will refrain from further said kibitzing in this particular thread within this forum....even if it is painfully unclear what does and does not "belong" in a "discussion" thread about the "Texas prototypes".

IIUC this thread is to discuss about prototypes, such as sn15/bn2 etc. of their constructon and testing and of the results of the last one.  Things such flight plans are best suited for the engineering thread.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 05:14 pm
IIUC this thread is to discuss about prototypes, such as sn15/bn2 etc....

Makes sense....

Quote
... of their constructon and testing and of the results of the last one.  Things such flight plans are best suited for the engineering thread.

I will remember that going forward.  Just don't expect anyone to automagically "know" this since no where in the first post of this thread (or anywhere else I'm aware of) is this stated or even implied.

Anyway...back to "on topic" discussion...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/18/2021 06:27 pm
The last crop of posts are vastly off-topic for this thread. The General Engineering thread, Fleets and Facilities forum etc are better fits for this kind of general kibitzing about plans and flight profiles for future orbital operations.
I don't see how the so called "kibitzing" about SS / SH belongs in a forum other than this one...you know, the "SH / SS" forum.

That being said, I will refrain from further said kibitzing in this particular thread within this forum....even if it is painfully unclear what does and does not "belong" in a "discussion" thread about the "Texas prototypes".

Just take 30 seconds and scan down the list of threads. You'll get the idea.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/18/2021 06:56 pm
The last crop of posts are vastly off-topic for this thread. The General Engineering thread, Fleets and Facilities forum etc are better fits for this kind of general kibitzing about plans and flight profiles for future orbital operations.

Darn. And this discussion was just getting interesting and I had a very good opinion to state in rebuttal to the posts above (and below).
 :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 07:05 pm

Just take 30 seconds and scan down the list of threads. You'll get the idea.

I may not be a rocket scientist...but I'm not an idiot.  The question I posed that apparently derailed this thread had to do with a future Texas Prototype (BN-3)...and specifically what the test campaign for that Texas Prototype might look like.

I scanned the list of threads.  I see no other existing thread where that kind of post fits better than this one:
* Any "updates" threads:  no (shudder at the thought)
* Heat shields, landing legs, or other subsystem specific threads?   No
* Any of the various moonship / artemis program threads? No
* Boring Company:  (what is that thread even doing in this forum? )
* RUDs, payloads...raptors....No
* General Engineering...really?  You think a post about test campaign speculation on a specific upcoming Texas Prototype (BN-3) is more appropriate in an engineering thread vs. a prototype thread? 

* "I risk sending a thread off topic" thread...sure I suppose it could go here....I mean...ANYTHING can go here.

The only other alternative would be to create a new thread.  Fair enough.

Look, I absolutely despise the fact that I have become "that guy" in this thread that's going to whine about posting "etiquette/rules".  I am merely suggesting that just because the specific "Texas Prototype" topic I posted about in this DISCUSSION thread may not be of personal interest to you...doesn't necessarily mean it's not appropriate for this thread or is not worthy of discussion. 

Consider that maybe...just maybe...I did take 30 seconds to look at the list of topics and I came to the conclusion that this thread is in fact the most appropriate home for it  compared to the other existing threads.

Now that I've taken my 30+ seconds, how about you take 30 seconds to consider if speculation on BN-3 testing campaign is really so off topic for this thread?



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 04/18/2021 07:30 pm

Just take 30 seconds and scan down the list of threads. You'll get the idea.

I may not be a rocket scientist...but I'm not an idiot.  The question I posed that apparently derailed this thread had to do with a future Texas Prototype (BN-3)...and specifically what the test campaign for that Texas Prototype might look like.

I scanned the list of threads.  I see no other existing thread where that kind of post fits better than this one:
* Any "updates" threads:  no (shudder at the thought)
* Heat shields, landing legs, or other subsystem specific threads?   No
* Any of the various moonship / artemis program threads? No
* Boring Company:  (what is that thread even doing in this forum? )
* RUDs, payloads...raptors....No
* General Engineering...really?  You think a post about test campaign speculation on a specific upcoming Texas Prototype (BN-3) is more appropriate in an engineering thread vs. a prototype thread? 

* "I risk sending a thread off topic" thread...sure I suppose it could go here....I mean...ANYTHING can go here.

The only other alternative would be to create a new thread.  Fair enough.

Look, I absolutely despise the fact that I have become "that guy" in this thread that's going to whine about posting "etiquette/rules".  I am merely suggesting that just because the specific "Texas Prototype" topic I posted about in this DISCUSSION thread may not be of personal interest to you...doesn't necessarily mean it's not appropriate for this thread or is not worthy of discussion. 

Consider that maybe...just maybe...I did take 30 seconds to look at the list of topics and I came to the conclusion that this thread is in fact the most appropriate home for it  compared to the other existing threads.

Now that I've taken my 30+ seconds, how about you take 30 seconds to consider if speculation on BN-3 testing campaign is really so off topic for this thread?
https://forum.nasaspaceflight.com/index.php?topic=49276.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/18/2021 07:59 pm
Mods...please move the last several posts to the "NASASpaceflight.com and NSF Forum Site Rules/News" forum or wherever else you feel appropriate.  I do not want to clutter up this thread any more than I already have.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 04/18/2021 08:01 pm

https://forum.nasaspaceflight.com/index.php?topic=49276.0

I moved my comments on SH first flight there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 04/18/2021 09:23 pm
I know that they have a TFR for Tuesday 20. , but do they have a launch authorization too?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 04/18/2021 11:59 pm
https://twitter.com/nextspaceflight/status/1383926216353226752?
Please check the previous posts in the update thread. You keep posting updates that have already been posted.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/19/2021 01:59 am
I know that they have a TFR for Tuesday 20. , but do they have a launch authorization too?

They need to static fire first.

Did they ever install a third raptor?  Didn't see that in the updates thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 04/19/2021 04:11 am
I know that they have a TFR for Tuesday 20. , but do they have a launch authorization too?

They need to static fire first.

Did they ever install a third raptor?  Didn't see that in the updates thread.

Not yet. One went back to the build site, and a new third engine was wheeled out earlier tonight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 04/19/2021 09:29 am
If it is SN54 it is the old one!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: samgineer on 04/19/2021 09:58 am
If it is SN54 it is the old one!
SN54 is as I know is one of the first from new Raptor design. Old one won´t fit in SN15 redesigned puck.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/19/2021 10:40 am
If it is SN54 it is the old one!
SN54 is as I know is one of the first from new Raptor design. Old one won´t fit in SN15 redesigned puck.
Or he probably meant that the it's the same engine that was rolled out with the other two a few days ago rather than a new engine
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: loekf on 04/19/2021 11:11 am
If it is SN54 it is the old one!
SN54 is as I know is one of the first from new Raptor design. Old one won´t fit in SN15 redesigned puck.

My guess is that they had integration issues with the new puck and didn't want to risk the Raptors on site trying to make things work. Could be piping or cabling slightly misaligned.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/19/2021 12:20 pm
If it is SN54 it is the old one!
SN54 is as I know is one of the first from new Raptor design. Old one won´t fit in SN15 redesigned puck.

My guess is that they had integration issues with the new puck and didn't want to risk the Raptors on site trying to make things work. Could be piping or cabling slightly misaligned.

Having designed some similarly complicated interfaces for space hardware before, in the absence of further details from Elon, I’d suggest the possibility of a damaged or dinged fluid coupling or electronic telemetry/control cable connector, possibly damaged during the first install attempt the other day.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 04/19/2021 01:11 pm
If it is SN54 it is the old one!
SN54 is as I know is one of the first from new Raptor design. Old one won´t fit in SN15 redesigned puck.
Or he probably meant that the it's the same engine that was rolled out with the other two a few days ago rather than a new engine

Exactly 👍
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/19/2021 03:19 pm
Quote from: Lampyridae link=topic=53471.msg2222637#msg2222637
SN20-25? are for testing orbital flight and re-entry, SpaceX is not expecting them to land, it would just be nice if they did. But they do need to function in orbit, and have a full TPS so there is a longer lead time on them. SN21 might incorporate changes based on SN15-19 so you might see that only kicking off once SN19 is fully under way.

I agree.  I also think that SN20 represents the "baseline" for an orbital vehicle in terms of strength.  So I expect SN21 to be manufactured only after the learnings from SN20...plus additional learnings from stress testing using the testing rig.

My thoughts are that the cadence of testing orbital vehicles Sn20+ is going to slow down somewhat from the current pace.  They may end up continuing to test sub-orbital landing prototypes in parallel with orbital launches / tests.

They are going to now also need to start testing LEO refueling in earnest.  They may choose to create initial test/prototype vehicles for that with no intention of returning them to Earth...(no TPS / re-entry)...so that offers another potentially parallel prototype path.
Or maybe 20 will, depending on what they run into in SN15+, be a production pathfinder and scrapped. Agile. We don't know. They don't know.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/19/2021 03:29 pm
EDIT:  Refueling will most likely require offshore launch platforms so they need to be readied also.

Ultimately, I agree (for production refueling to capacity...requiring multiple launches and therefore launched offshore).

However, for initial tests I don't think they need to launch multiple tankers: just two. One recipient vehicle in orbit...and a second tanker vehicle launched that they can run several tests with.  They can even run multiple dockings / propellant transfers with the same tanker.
It's reasonable to expect early props transfer attempts without a dedicated tanker variant. Minimum necessary for PoC is two ships on orbit and the transfer of only enough to reach a steady state of flow. One or both ships can be used for Starlink launches, or not.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Joey D on 04/19/2021 03:37 pm
It's reasonable to expect early props transfer attempts without a dedicated tanker variant. Minimum necessary for PoC is two ships on orbit and the transfer of only enough to reach a steady state of flow. One or both ships can be used for Starlink launches, or not.

Agreed.  I was responding to the assumption that fuel transfer tests would require multiple "rapid succession" off-shore launches.  I don't believe that will be required
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/19/2021 03:39 pm
The last crop of posts are vastly off-topic for this thread. The General Engineering thread, Fleets and Facilities forum etc are better fits for this kind of general kibitzing about plans and flight profiles for future orbital operations.
I don't see how the so called "kibitzing" about SS / SH belongs in a forum other than this one...you know, the "SH / SS" forum.

That being said, I will refrain from further said kibitzing in this particular thread within this forum....even if it is painfully unclear what does and does not "belong" in a "discussion" thread about the "Texas prototypes".

Just take 30 seconds and scan down the list of threads. You'll get the idea.
In theory, the different threads cleave cleanly. In practice there is overlap.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 04/19/2021 03:44 pm
It's reasonable to expect early props transfer attempts without a dedicated tanker variant. Minimum necessary for PoC is two ships on orbit and the transfer of only enough to reach a steady state of flow. One or both ships can be used for Starlink launches, or not.
I'd expect interim milestones -- unmated zero-G ops, docking, wet seal, leader/follower coordination, etc.  Likely one or more of these passes per test of course, and I doubt we'll see that level of specificity reported, but we should probably keep in mind that there can be forward progress without achievement of "successful in-orbit propellant transfer."
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/19/2021 03:51 pm

Just take 30 seconds and scan down the list of threads. You'll get the idea.

I may not be a rocket scientist...but I'm not an idiot.  The question I posed that apparently derailed this thread had to do with a future Texas Prototype (BN-3)...and specifically what the test campaign for that Texas Prototype might look like.

I scanned the list of threads.  I see no other existing thread where that kind of post fits better than this one:
* Any "updates" threads:  no (shudder at the thought)
* Heat shields, landing legs, or other subsystem specific threads?   No
* Any of the various moonship / artemis program threads? No
* Boring Company:  (what is that thread even doing in this forum? )
* RUDs, payloads...raptors....No
* General Engineering...really?  You think a post about test campaign speculation on a specific upcoming Texas Prototype (BN-3) is more appropriate in an engineering thread vs. a prototype thread? 

* "I risk sending a thread off topic" thread...sure I suppose it could go here....I mean...ANYTHING can go here.

The only other alternative would be to create a new thread.  Fair enough.

Look, I absolutely despise the fact that I have become "that guy" in this thread that's going to whine about posting "etiquette/rules".  I am merely suggesting that just because the specific "Texas Prototype" topic I posted about in this DISCUSSION thread may not be of personal interest to you...doesn't necessarily mean it's not appropriate for this thread or is not worthy of discussion. 

Consider that maybe...just maybe...I did take 30 seconds to look at the list of topics and I came to the conclusion that this thread is in fact the most appropriate home for it  compared to the other existing threads.

Now that I've taken my 30+ seconds, how about you take 30 seconds to consider if speculation on BN-3 testing campaign is really so off topic for this thread?
And here we have an example of where the cleaving is at least a little bit a matter of personal perception.


If I may make a suggestion. Compared to past examples, this splinter thread is not so far off or extensive as to demand a formal splintering. Allow a splinter enough momentum to develop a clear splinter identity, then complain. If there is no other discussion that EXACTLY hits the mark and it's bothering you, start a new thread yourself and point everybody to it. If the topic does not interest you, you need never see that thread again.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/19/2021 04:05 pm
It's reasonable to expect early props transfer attempts without a dedicated tanker variant. Minimum necessary for PoC is two ships on orbit and the transfer of only enough to reach a steady state of flow. One or both ships can be used for Starlink launches, or not.
I'd expect interim milestones -- unmated zero-G ops, docking, wet seal, leader/follower coordination, etc.  Likely one or more of these passes per test of course, and I doubt we'll see that level of specificity reported, but we should probably keep in mind that there can be forward progress without achievement of "successful in-orbit propellant transfer."
Sounds like the Boeing or ULA approach. Each test you describe can be considered a sub test in the sequence. If one sub test fails then another test launch would be needed to move ahead. OTOH, if all sub tests succeed one one flight, the whole concept is validated.


Think SN8. The approach your suggesting would have gone through the climb, and maybe the pitch over, then left it to fall back uncontrolled. Instead they went for the whole enchilada and hit the wall only after validating the entire skydive concept. Still needs some work...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dnavas on 04/19/2021 05:05 pm
Sounds like the Boeing or ULA approach. Each test you describe can be considered a sub test in the sequence. If one sub test fails then another test launch would be needed to move ahead. OTOH, if all sub tests succeed one one flight, the whole concept is validated.

Depends which side you're talking about.  If you have lots of interim steps, you can take the next step with your previous test article, rather than wait for the next batch.  There are step functions, of course, beyond which you cannot go -- without a heat shield you're not practicing hot re-entries, but you don't need a tanker to practice in -orbit refueling.  You need to get to orbit, mind you, but you don't need to get back, so you go up, you work on in-orbit ops, then you try a re-entry -- we won't know which one is the long-pole until we get there, so you build your prototypes with more capabilities than you expect to be able to prove out.  And then when things go better than expected, it looks worse (they didn't laaaand!) but really four SN#s are cancelled and the schedule moves forward in unexpected ways.

My point is that there isn't really a minimum PoC, there are lots of little tests, some subset of them proves some conceptual feat, but they are unlikely to constrain themselves to a strict hierarchy of execution.  They might get to the moon before they get their tiles to work (extreme, and probably expensive example with the loss off n-tankers per lunar flight).

[ed: of course, they might just do re-entry burns prior to fully working tiles and suffer the loss in performance instead]
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 04/19/2021 05:43 pm
I really love how low tech much of their operation appears. You've got a state-of-the-art rocket engine being delivered to the launch site on a flatbed trailer pulled by a pick-up truck. It's offloaded by a fork lift and installed with a scissor lift on a rocket that was built in a barn. No cost plus here!  8)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: _MECO on 04/19/2021 06:00 pm
I really love how low tech much of their operation appears. You've got a state-of-the-art rocket engine being delivered to the launch site on a flatbed trailer pulled by a pick-up truck. It's offloaded by a fork lift and installed with a scissor lift on a rocket that was built in a barn. No cost plus here!  8)
Technology where technology's due. There's great symbolism between the ethos of SpaceX compared to other Aerospace comanies. Company XYZ might painstakingly mill isogrid tanks that have excellent mass margins and have paid a mere $100 million for the engines on their booster. Meanwhile SpaceX welds stringers because they had a sale at Ace Hardware that day and they make their own engines at less than $2 million a pop. What's so wrong with a grimy forklift? If your engine can swallow a wing nut and be fine then some dust won't be the end of the world (at least so long as it isn't in the LOX tank.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/19/2021 08:07 pm
I really love how low tech much of their operation appears. You've got a state-of-the-art rocket engine being delivered to the launch site on a flatbed trailer pulled by a pick-up truck. It's offloaded by a fork lift and installed with a scissor lift on a rocket that was built in a barn. No cost plus here!  8)
If Starship is going to scale, it can’t scale with expensive operations (fit, test and repair). So why not expose engines to the real life day-to-day bumps and get those issues exposed quickly? Wrapping these engines in cotton wool won’t improve their operation the slightest.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/19/2021 08:29 pm
I really love how low tech much of their operation appears. You've got a state-of-the-art rocket engine being delivered to the launch site on a flatbed trailer pulled by a pick-up truck. It's offloaded by a fork lift and installed with a scissor lift on a rocket that was built in a barn. No cost plus here!  8)

A little off topic, but had to throw in historic pic that emulates present day. Boiler plate Mercury capsule being delivered to pad on flatbed. If you look closely you can see the mattress being used as cushioning between the capsule pallet and bed of truck. Some one more knowledgeable may be able to credit original source, but its on the web at: https://imgur.com/gallery/zNU2E6a
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 04/19/2021 09:25 pm
I really love how low tech much of their operation appears. You've got a state-of-the-art rocket engine being delivered to the launch site on a flatbed trailer pulled by a pick-up truck. It's offloaded by a fork lift and installed with a scissor lift on a rocket that was built in a barn. No cost plus here!  8)

A little off topic, but had to throw in historic pic that emulates present day. Boiler plate Mercury capsule being delivered to pad on flatbed. If you look closely you can see the mattress being used as cushioning between the capsule pallet and bed of truck. Some one more knowledgeable may be able to credit original source, but its on the web at: https://imgur.com/gallery/zNU2E6a
Yes, in the very earliest days of NASA they were still "winging it" like SpaceX has done, inventing your procedures as you go along through trial and error, and adapting existing equipment to the purpose.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/19/2021 09:43 pm
New video premiering shortly (on the hour)

https://youtu.be/4D02-Kw0mPU
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/20/2021 12:56 am
The update thread says SN15 static fire was pushed back to Wednesday and TFR was canceled for Thursday... was there a problem with installing the engines?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/20/2021 02:11 am
The update thread says SN15 static fire was pushed back to Wednesday and TFR was canceled for Thursday... was there a problem with installing the engines?

We don’t know.

One of the joys of roadside rocket science while Texas tank watching  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/20/2021 02:54 am
Could those BN grid fins be made of https://en.wikipedia.org/wiki/Weathering_steel ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SeaRaven on 04/20/2021 05:49 am
Could those BN grid fins be made of https://en.wikipedia.org/wiki/Weathering_steel ?

COR-TEN is designed to rust in order to produce that weathered patina so beloved of architects, but Fe2O3·nH2O and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3) contained in the rust triggers corrosion in stainless steel.  Any rust stains on the tank barrels will trigger this cascade.

I found this out to my cost when I let iron sparks from a disc cutter splatter a 316 stainless steel stanchion baseplate.  Despite rubbing the dust off, the stanchion started to stain and rust within 3 weeks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/20/2021 01:11 pm
The update thread says SN15 static fire was pushed back to Wednesday and TFR was canceled for Thursday... was there a problem with installing the engines?

Still thinking that SpaceX doesn't want Starship to conflict with Crew Dragon, whether due to company resources or public display. This has been their past pattern. They may have scheduled it with a possible delay on Crew Dragon, but cancelled it when all looks like Crew Dragon is a go for Thursday.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nuukee on 04/20/2021 01:14 pm
Still thinking that SpaceX doesn't want Starship to conflict with Crew Dragon, whether due to company resources or public display. This has been their past pattern. They may have scheduled it with a possible delay on Crew Dragon, but cancelled it when all looks like Crew Dragon is a go for Thursday.

You mean just like exploding SN4 during static fire one day before their first crewed launch? ;-)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 04/20/2021 01:17 pm
The update thread says SN15 static fire was pushed back to Wednesday and TFR was canceled for Thursday... was there a problem with installing the engines?

Still thinking that SpaceX doesn't want Starship to conflict with Crew Dragon, whether due to company resources or public display. This has been their past pattern. They may have scheduled it with a possible delay on Crew Dragon, but cancelled it when all looks like Crew Dragon is a go for Thursday.
Yeah, good point. They probably don't want to risk a "SpaceX fireball" on the news a day or two before a SpaceX crew launch, as there will be enough people who don't understand that Starship and F9/Dragon are entirely different things.

They did this for one of the previous Crew Dragon launches, I believe.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/20/2021 01:35 pm
The update thread says SN15 static fire was pushed back to Wednesday and TFR was canceled for Thursday... was there a problem with installing the engines?

Still thinking that SpaceX doesn't want Starship to conflict with Crew Dragon, whether due to company resources or public display. This has been their past pattern. They may have scheduled it with a possible delay on Crew Dragon, but cancelled it when all looks like Crew Dragon is a go for Thursday.
Yeah, good point. They probably don't want to risk a "SpaceX fireball" on the news a day or two before a SpaceX crew launch, as there will be enough people who don't understand that Starship and F9/Dragon are entirely different things.

They did this for one of the previous Crew Dragon launches, I believe.

There's that for sure, but also it appears the everyone in SpaceX pauses to view major events like this to show employees what their work is producing. Very good for morale. Also, every major SpaceX event is also public relations event intended to promote public support. This is why SpaceX does such great F9 launch broadcasts as well. They may want to keep these separated for that reason. I'm pretty sure there are still shared resources used for both types of launches as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/20/2021 03:07 pm
Still thinking that SpaceX doesn't want Starship to conflict with Crew Dragon, whether due to company resources or public display. This has been their past pattern. They may have scheduled it with a possible delay on Crew Dragon, but cancelled it when all looks like Crew Dragon is a go for Thursday.

You mean just like exploding SN4 during static fire one day before their first crewed launch? ;-)
It didn't explode during static fire.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/20/2021 03:41 pm
A few possibilities come to mind for the delay:

- crew 2, let's wait until that's over
- HLS, pressure is off (or less) to complete another flight before award
- issues with vehicle, potentially Raptor, thereby causing delays
- GSE taking priority, and potential conflicts with operations

Just some ideas
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: oldAtlas_Eguy on 04/20/2021 03:52 pm
A few possibilities come to mind for the delay:

- crew 2, let's wait until that's over
- HLS, pressure is off (or less) to complete another flight before award
- issues with vehicle, potentially Raptor, thereby causing delays
- GSE taking priority, and potential conflicts with operations

Just some ideas
FAA flight license/approval for the test flight? But that is not required for the hotfire. But if the flight is delayed then a delay of the hotfire could be to support not interrupting workflows elsewhere around the site unless really needed. You would want to have the two hotfire and flight as close together as you can get them to make the least total impact on workflows and equipment movement. Only move stuff once for both not once each. It's a cost cutting item.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: butters on 04/20/2021 04:00 pm
Occam's razor says that the weather forecast in Boca Chica isn't looking good for Thursday or especially Friday. The weekend looks lovely, but they don't launch on weekends.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 04/20/2021 04:04 pm
I really love how low tech much of their operation appears. You've got a state-of-the-art rocket engine being delivered to the launch site on a flatbed trailer pulled by a pick-up truck. It's offloaded by a fork lift and installed with a scissor lift on a rocket that was built in a barn. No cost plus here!  8)

A little off topic, but had to throw in historic pic that emulates present day. Boiler plate Mercury capsule being delivered to pad on flatbed. If you look closely you can see the mattress being used as cushioning between the capsule pallet and bed of truck. Some one more knowledgeable may be able to credit original source, but its on the web at: https://imgur.com/gallery/zNU2E6a

And of course:
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Curriston on 04/20/2021 05:19 pm
A few possibilities come to mind for the delay:

- crew 2, let's wait until that's over
- HLS, pressure is off (or less) to complete another flight before award
- issues with vehicle, potentially Raptor, thereby causing delays
- GSE taking priority, and potential conflicts with operations

Just some ideas
Well, there is the fact that SN15 and Raptor are a new design, I expect some preburner tests, maybe a couple static fires to get a good handle on things before a launch? No sense of getting too excited about this test, there are lots of other things happening at the launch site to keep you occupied!!!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/20/2021 07:58 pm
A few possibilities come to mind for the delay:
It seems very strange that anyone is calling this a delay.  Anyone who expected SN15 to launch 3 days after arriving at the pad, with no static fire was living in cloud cuckoo land.  There's a ton of changes both on the ship, and the engines.  They're doing more comprehensive testing than they have for a good long time, for good reason.  There's at very least a wet dress rehearsal and a static fire going to happen before a launch.  Expecting them to happen faster than SN11, when it's a new design is just not realistic.

Quote
- crew 2, let's wait until that's over
I really don't think either NASA or SpaceX gives a hoot.  They both know it's an entirely different rocket at an entirely different phase of development.

Quote
- HLS, pressure is off (or less) to complete another flight before award
SpaceX aren't going to be rushing things to flight before they're ready because they think NASA can't see that they're running a development program.  If anything, launching a starship before it's ready is going to make NASA less likely to award them a contract, not more.

Quote
- issues with vehicle, potentially Raptor, thereby causing delays
I doubt it - they're just taking their time and making sure everything fits as it's expected to.  This again is a significantly different design.  They'll have to work through every bit of fitment checking that it's dead right.

Quote
- GSE taking priority, and potential conflicts with operations
I'd be amazed if GSE for a launch pad that's not even built yet was taking priority over Starship launches.  The GSE tanks are in no way the long pole on the orbital launch site.

Here's the cause of the delay in my opinion - it isn't a delay.  This is normal operation, and exactly the normal proceedure for checking out a new ship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/20/2021 10:13 pm
Here's the cause of the delay in my opinion - it isn't a delay.  This is normal operation, and exactly the normal proceedure for checking out a new ship.

There was good evidence from several sources that SpaceX had HOPED to static fire the vehicle yesterday and fly today. Road closures were set, the FAA had issued TFRs, etc. All those were canceled.

You know, it's not a sin to admit delays happen and SpaceX's targets are aspirational best-case scenarios.
 Sometimes life just doesn't work out and it's okay to accept that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/20/2021 11:30 pm
Here's the cause of the delay in my opinion - it isn't a delay.  This is normal operation, and exactly the normal proceedure for checking out a new ship.

There was good evidence from several sources that SpaceX had HOPED to static fire the vehicle yesterday and fly today. Road closures were set, the FAA had issued TFRs, etc. All those were canceled.

You know, it's not a sin to admit delays happen and SpaceX's targets are aspirational best-case scenarios.
 Sometimes life just doesn't work out and it's okay to accept that.
SpaceX has filed for TFRs several times in the past when they had absolutely no chance at all of doing any work at all.  There was a point at SN10 when people were yelling about there being a flight the next day even though SN10 hadn't even made it to the pad yet.

There's clearly at least an element of automation going into the TFR filing.  It's really not reasonable to assume that because a TFR was filed, they actually thought they might fly.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 04/20/2021 11:42 pm
No one ever got fired for filing for a TFR that didn't get used.

On the other hand...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/20/2021 11:55 pm
A few possibilities come to mind for the delay:
It seems very strange that anyone is calling this a delay.  Anyone who expected SN15 to launch 3 days after arriving at the pad, with no static fire was living in cloud cuckoo land.  There's a ton of changes both on the ship, and the engines.  They're doing more comprehensive testing than they have for a good long time, for good reason.  There's at very least a wet dress rehearsal and a static fire going to happen before a launch.  Expecting them to happen faster than SN11, when it's a new design is just not realistic.

Quote
- crew 2, let's wait until that's over
I really don't think either NASA or SpaceX gives a hoot.  They both know it's an entirely different rocket at an entirely different phase of development.

Quote
- HLS, pressure is off (or less) to complete another flight before award
SpaceX aren't going to be rushing things to flight before they're ready because they think NASA can't see that they're running a development program.  If anything, launching a starship before it's ready is going to make NASA less likely to award them a contract, not more.

Quote
- issues with vehicle, potentially Raptor, thereby causing delays
I doubt it - they're just taking their time and making sure everything fits as it's expected to.  This again is a significantly different design.  They'll have to work through every bit of fitment checking that it's dead right.

Quote
- GSE taking priority, and potential conflicts with operations
I'd be amazed if GSE for a launch pad that's not even built yet was taking priority over Starship launches.  The GSE tanks are in no way the long pole on the orbital launch site.

Here's the cause of the delay in my opinion - it isn't a delay.  This is normal operation, and exactly the normal proceedure for checking out a new ship.

Wow, you went to a lot of work to try to poke holes in what I said! Look, I had no opinion either way that SN15 would or would not launch on Tuesday, although it did seem optimistic. And yes, it was a delay because SpaceX had hoped to fly on Tuesday, as Herb pointed out. That's obvious. It didn't happen, so it's a schedule slip for them, also known as a delay. Simple as that. Whether or not it was unexpected is beside the point. I was just throwing ideas out there as to why that might be.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 04/21/2021 12:08 am
SpaceX has filed for TFRs several times in the past when they had absolutely no chance at all of doing any work at all.  There was a point at SN10 when people were yelling about there being a flight the next day even though SN10 hadn't even made it to the pad yet.

There's clearly at least an element of automation going into the TFR filing.  It's really not reasonable to assume that because a TFR was filed, they actually thought they might fly.

I call BS on this.

"People yelling" isn't "SpaceX filing a TFR" and I guarandamntee you SX has never filed a TFR for a day after one in which a flight article has yet to be moved to the pad.

They may be front-running planned activities by some period of time (one day, not on pad, isn't it) but that's not the same as "no chance".

I'll guarantee you there is no automation in play.

They file TFR's based on expectation, but things are fluid and change.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: daavery on 04/21/2021 01:13 am
it appears the Spacex has a plan that files 2 weeks of launch TFRs and then release 3 days at a time from that block
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/21/2021 01:26 am
it appears the Spacex has a plan that files 2 weeks of launch TFRs and then release 3 days at a time from that block


SpaceX can't "file a TFR." TFRs are granted by the FAA. SpaceX can *request* TFR's which may then be granted or denied by the FAA. The approval process has probably gotten streamlined since they first started requesting these, but neither the request nor approval is without oversight. And just like any business working with regulated resources (in this case, airspace), if the the FAA feels they are being taken advantage of (SpaceX "crying wolf" by requesting dispensations it has no intention of using), the FAA will tighten the approval process.

Similarly, SpaceX is limited in the number of days per year they can request closure of access to the beach - they request dates they have reasonable belief they can take advantage of, and withdraw those requests as soon as it becomes clear they won't be able to use.

Every single sign leads any reasonable outside observer to believe that as of about a week or so ago, the plan was static fire Monday, flight Tuesday. Multiple trusted sources with contacts at SpaceX were talking about these plans as recently as this past weekend. The fact that it didn't happen that way is simple reality getting in the way of best-case scenarios. It's not any kind of attack on SpaceX to understand these facts.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 04/21/2021 01:44 am
A new booster dome labeled "B2.1 Dome" was spotted


This is not the way that they have named prototype vehicle intended to fly before. The nomenclature with a “.1” is different. The only place I remember seeing that nomenclature before is on test articles like SN7 flavors of tanks that only serve for pressure tests
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/21/2021 01:59 am
A new booster dome labeled "B2.1 Dome" was spotted


This is not the way that they have named prototype vehicle intended to fly before. The nomenclature with a “.1” is different. The only place I remember seeing that nomenclature before is on test articles like SN7 flavors of tanks that only serve for pressure tests
I saw an upper dome labeled BN1 after there was already one stacked in the Highbay. Mistakes or design changes might cause them to build a second item with a slightly different name.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WindyCity on 04/21/2021 03:35 am
Would folks have expected a pre-burner test prior to a static fire, given that SN15 has a new iteration of raptors?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Chris Bergin on 04/21/2021 03:35 pm
I think it should also be posted here:

Today's road closure modified in a rather odd way. I think the first part of te closure (from 12:00 p.m. to 2:00 p.m.) could be used for a transfer to the test site.

From 05:00 p.m. to 07:00 p.m. they could run tests on SN15 (?)

There won't be a Static Fire test on SN15 today. Trust the people and a site with a track record and the ability to ask the right people, not random discords that claim Launch Mounts are absolutely Water Towers. ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Paul Howard on 04/21/2021 04:02 pm
Will they do a preburner?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Chris Bergin on 04/21/2021 04:05 pm
Will they do a preburner?

Nah, that'd be in the guise of a Static Fire test. Perhaps a WDR. This vehicle's only been tested with LN2 so far.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/21/2021 04:11 pm
Thanks to Chris B for the update.  :D
 
Really think these “delays” are just them triple checking everything to verify everything is rock solid so that they can successfully bring back 15. It could be them waiting for FAA approval to fire up, just so there is no long bridge between SF and flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/21/2021 04:19 pm
Road is closed. Likely a move of some sort.

Credit: LabPadre Sentinel Cam

Yes, a big partially assembled LR 11350.

Credit LabPadre pad cam

(seemed to be more of a discussion than an update, so posting the reply here)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/21/2021 06:23 pm
I nominate calling the  LR 11350 crane a simple name, "Big Red".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/21/2021 06:33 pm
I nominate calling the  LR 11350 crane a simple name, "Big Red".

Or 'Tiny'

I don't know why SpaceX drives cranes around so much.  Hopefully these days come to close after the Orbital site is built out.

It's a lot of time and resources going into moving cranes instead of building, moving and flying rockets.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/21/2021 06:38 pm
Thanks to Chris B for the update.  :D
 
Really think these “delays” are just them triple checking everything to verify everything is rock solid so that they can successfully bring back 15. It could be them waiting for FAA approval to fire up, just so there is no long bridge between SF and flight.

I agree, because if they test this prototype extensively they will have data for the next prototypes, so IMO it is worth it. Now that the focus is the landing I espect extensive tests, and even small issues (or issues that seem small to us) may push them to do extensive checks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 04/21/2021 07:22 pm
Thanks to Chris B for the update.  :D
 
Really think these “delays” are just them triple checking everything to verify everything is rock solid so that they can successfully bring back 15. It could be them waiting for FAA approval to fire up, just so there is no long bridge between SF and flight.


Do we know if the FAA requires approval for static fires, or only actual flights?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: neoforce on 04/21/2021 07:54 pm


I don't know why SpaceX drives cranes around so much.  Hopefully these days come to close after the Orbital site is built out.

It's a lot of time and resources going into moving cranes instead of building, moving and flying rockets.

Seems clear that these days will come to a close once both orbital sites are built.  (given the pending request to build a second site adjacent to the first)    After all the main purpose of the LR 11350 is to build the launch tower, right?  So once both towers are done, they shouldn't have that crane.  And since its a very expensive rental, better to have it out of the way before SN15 launches
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/21/2021 08:15 pm
Thanks to Chris B for the update.  :D
 
Really think these “delays” are just them triple checking everything to verify everything is rock solid so that they can successfully bring back 15. It could be them waiting for FAA approval to fire up, just so there is no long bridge between SF and flight.


Do we know if the FAA requires approval for static fires, or only actual flights?


Not sure. No real logic to that guess I made other than them not wanting to wait a long period between firing and flying.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 04/22/2021 09:13 am
https://twitter.com/bocacharts/status/1385138605413310466

Quote
All Major Testing (as of 2am on 22 April 2021)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/22/2021 03:55 pm
https://www.cameroncounty.us/spacex/


Since the first road closure of today as been used for transport, could the second be used for static fire? But it would seem strange to me, since they would need to be very very quick. But there is still the flight TFR fot tomorrow and there is a flight road/beach closure for tomorrow too. Could they attempt a static fire and then launch today, like they did with sn11 (but then scrubbed)?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: James54 on 04/22/2021 03:58 pm
I nominate calling the  LR 11350 crane a simple name, "Big Red".

Since the Dutch word "mammonet" (mammoth in English) is on the side of the crane I nominate "Red Mammoth".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DistantTemple on 04/22/2021 04:04 pm
I nominate calling the  LR 11350 crane a simple name, "Big Red".

Since the Dutch word "mammonet" (mammoth in English) is on the side of the crane I nominate "Red Mammoth".
Well good on you not to name it White Elephant or we'd be getting our f*sts  out!
Its structurally more structurally similar to a giraffe,
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/22/2021 04:07 pm
I like Red Mammoth,  the Mammoth is one of my favorite animals, top of my list of species to bring back.

Looking forward to seeing them stack the big steel.  Will it be stick by stick, or will they pre-assemble 1 level at a time and do large picks with the Red Mammoth.

I've been on projects that built structures this way, it be safer and reduces the time to make picks as it gets taller.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/22/2021 04:12 pm
I nominate calling the  LR 11350 crane a simple name, "Big Red".

Since the Dutch word "mammonet" (mammoth in English) is on the side of the crane I nominate "Red Mammoth".

The Leibherr crane with the Mammoet sign on it is not the crane at the launch site. I believe it is a picture of the same model crane being used to assemble windmills.

Edited to fix crane mfg.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 04/22/2021 04:14 pm
https://www.cameroncounty.us/spacex/


Since the first road closure of today as been used for transport, could the second be used for static fire? But it would seem strange to me, since they would need to be very very quick. But there is still the flight TFR fot tomorrow and there is a flight road/beach closure for tomorrow too. Could they attempt a static fire and then launch today, like they did with sn11 (but then scrubbed)?

My bet is on the second closure being used to move Cranezilla (or was it "Bluezilla"?) back to the staging area since it needs to be away from the launch pad before flight.  Looks like they are unhooking it from the GSE tank now so they should be able to move it onto the rollers once the nosecone is unloaded.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/22/2021 04:57 pm
Clifford? (The big red dog crane)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/22/2021 05:03 pm
https://www.cameroncounty.us/spacex/


Since the first road closure of today as been used for transport, could the second be used for static fire? But it would seem strange to me, since they would need to be very very quick. But there is still the flight TFR fot tomorrow and there is a flight road/beach closure for tomorrow too. Could they attempt a static fire and then launch today, like they did with sn11 (but then scrubbed)?

My bet is on the second closure being used to move Cranezilla (or was it "Bluezilla"?) back to the staging area since it needs to be away from the launch pad before flight.  Looks like they are unhooking it from the GSE tank now so they should be able to move it onto the rollers once the nosecone is unloaded.

  GSE #3 is coming along fast, as well as its foundation. Test flight soon means move crane soon. Test flight later, place GSE #3 before move?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/22/2021 05:30 pm
https://twitter.com/fabiangranjaa/status/1385265119601459200?s=19
https://twitter.com/fabiangranjaa/status/1385269857642418177?s=19
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/22/2021 05:44 pm
Why did my post get deleted?  "Crane Kong" is hardly offensive.  ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 04/22/2021 07:04 pm
Why did my post get deleted?  "Crane Kong" is hardly offensive.  ???

I think that's what RGV and LabPadre are calling it.

---

Hmm, so apparently this Fabian works there. Cool picture. It's interesting that he mentioned "orbital" flight. I wonder if that just means max-q + g loads on the way to orbit.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/22/2021 07:33 pm
Why did my post get deleted?  "Crane Kong" is hardly offensive.  ???

I think that's what RGV and LabPadre are calling it.

---

Hmm, so apparently this Fabian works there. Cool picture. It's interesting that he mentioned "orbital" flight. I wonder if that just means max-q + g loads on the way to orbit.
Oh.  Well if they came up with it first that's cool.  It is rather obvious. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/22/2021 07:48 pm
https://twitter.com/fabiangranjaa/status/1385265119601459200?s=19
https://twitter.com/fabiangranjaa/status/1385269857642418177?s=19

So that confirms a test stand for forces experienced, most probably during reentry. But how will they apply stress, on which point? Did we spot some sort of hydraulic cilinders?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/22/2021 07:50 pm
yes, there is at least one inside nosecone
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: daavery on 04/22/2021 08:10 pm
piping and servo valves for at least 6 cylinders ( 2 per flap structure and 2 on nose front/sides) visible in pix
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/22/2021 08:13 pm
https://twitter.com/rgvaerialphotos/status/1385323283764047872

Quote
Starship SN16🚀

SN16 is in the mid bay. Could we see another time two starship at the pad (maybe not sn15 and sn16)? Since damages to sn10 were at worst negligible, but there isn't any reason to rollout before the time. Another question, why we see some times pad A or pad B used(SN15 pad A, sn11 used B)? Are there any differences beetween them?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: novo2044 on 04/22/2021 08:31 pm
Has anyone seen anything like this before?  I'm baffled how they can recreate aero forces with this rig.  Unless they are going to bolt things to the frame later?  Almost seems easier to just fire a spare SN straight up and let it land vertically.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sucramdi on 04/22/2021 08:43 pm
Has anyone seen anything like this before?  I'm baffled how they can recreate aero forces with this rig.  Unless they are going to bolt things to the frame later?  Almost seems easier to just fire a spare SN straight up and let it land vertically.

McGregor has a few structural test stands for Falcon 9 first and second stages. No idea how they work though.
https://forum.nasaspaceflight.com/index.php?topic=28332.msg1011837#msg1011837
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/22/2021 09:01 pm
Has anyone seen anything like this before?  I'm baffled how they can recreate aero forces with this rig.  Unless they are going to bolt things to the frame later?  Almost seems easier to just fire a spare SN straight up and let it land vertically.

Looks fine to me.  They can use hydraulics, cables and steel members to put the loads they need on this. 

I'm interested to see how it goes and what they learn.  Also, if this rig gets used again for different configurations like Lunar, tanker and cargo with the payload bay door cut into it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: launchwatcher on 04/22/2021 09:26 pm
I nominate calling the  LR 11350 crane a simple name, "Big Red".

Since the Dutch word "mammonet" (mammoth in English) is on the side of the crane I nominate "Red Mammoth".
Where did you see that?  Mammoet is a Dutch heavy lift company.   Its logo is the silhoutte of a mammoth; Fagioli is an Italian heavy lift company.    (Its logo is not the silhouette of a bean).    Both of them operate LR11350's; the one in Boca Chica appears to belong to Fagioli.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/22/2021 09:32 pm
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 04/22/2021 09:38 pm
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???

The pillars are not fully filled all the way with concrete - yet. (probably only 80-85% to the top) But there is rebar extending up all the way to the top, and these hanging cylinders are placed between the rebar. Then the rest of the concrete is pureed though the center hole in the cap. (I believe)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/22/2021 09:44 pm
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???



They will probably pump concrete or grouts into the top of the round metal plate. 

They can apply bonding compound to the top of the existing concrete before placing more on top of it.  But as long as the existing rebar and new bolts over lap within the concrete enough, then it works out.

My question is if they are anchor bolts intended to be used with structure to be applied above, or if they are just reinforcing items.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MTom on 04/22/2021 10:01 pm
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???



They will probably pump concrete or grouts into the top of the round metal plate. 

They can apply bonding compound to the top of the existing concrete before placing more on top of it.  But as long as the existing rebar and new bolts over lap within the concrete enough, then it works out.

My question is if they are anchor bolts intended to be used with structure to be applied above, or if they are just reinforcing items.


About lap length of rebar:

Quote
The tension forces are required to be transferred from one bar to the other bar at the location of discontinuity of the bar. So the second bar is kept closely to the first bar and overlapping is done. This amount of overlapping between two bars is called “lap length”. Lapping is usually done where minimum bending stress is encountered. In general, lap length is 50d which means 50 times the bar diameter, if both bars are of same diameter.
https://civildigital.com/calculation-lap-length-reinforced-concrete-structures/
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 04/23/2021 12:45 am
https://twitter.com/fabiangranjaa/status/1385265119601459200?s=19
https://twitter.com/fabiangranjaa/status/1385269857642418177?s=19

Please someone tell me those pictures was saved by somebody.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 04/23/2021 02:51 am


Please someone tell me those pictures was saved by somebody.

If they weren’t supposed to be taken or they weren’t supposed to be shared, then we don’t want them on this forum. Places like this exist because we all treat this stuff appropriately
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/23/2021 08:48 am
https://twitter.com/fabiangranjaa/status/1385265119601459200?s=19
https://twitter.com/fabiangranjaa/status/1385269857642418177?s=19

Please someone tell me those pictures was saved by somebody.

There was just a photo taken from a manlift, nothing we cant already see from Mary's photos, so you didn't miss anything.  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/23/2021 08:58 pm
The fact that they still aren't ready for sf in a whole week now is a cause of concern
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 04/23/2021 09:08 pm
The fact that they still aren't ready for sf in a whole week now is a cause of concern
in a test programme of a new version if it takes longer that SN6 and earlier's fully flow to last pre-launch test then that might be a cause for concern but its a test programme with additional RRT test points and objectives so I do not think we are at a point. Also every test delay allows OLP-A to be finished earlier. It is a fine balance.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/23/2021 09:14 pm
The fact that they still aren't ready for sf in a whole week now is a cause of concern
in a test programme of a new version if it takes longer that SN6 and earlier's fully flow to last pre-launch test then that might be a cause for concern but its a test programme with additional RRT test points and objectives so I do not think we are at a point. Also every test delay allows OLP-A to be finished earlier. It is a fine balance.

Today we saw a "lox dump test". Did we see anything like this before, and if,when? (I'm following starship from sn8 static fires, and I don't remember any of such test).

Could the goal be to refine tanks emptying after landing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 04/23/2021 11:22 pm
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???

The pillars are not fully filled all the way with concrete - yet. (probably only 80-85% to the top) But there is rebar extending up all the way to the top, and these hanging cylinders are placed between the rebar. Then the rest of the concrete is pureed though the center hole in the cap. (I believe)

It's very easy to imagine a flange hidden inside the tube, similar to the one we see on top of the new rebar, that sticks out a foot or two from the existing concrete for them to bolt the new rebar to before they fill it over with concrete.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: PreferToLurk on 04/24/2021 01:10 am
The fact that they still aren't ready for sf in a whole week now is a cause of concern
SN15 is ahead of the pace of every other SS prototype.  They missed an internal target date by a week.  They do that all the time. All schedules are aspirational, and week long delays are the norm.  This delay is entirely inconsequential.

Edit: not taking things personal
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/24/2021 01:54 am
I'm loving that the fact that it's taken them a week to do a static fire is "cause for concern".  Can you imagine if you'd said "yeh, they delayed the static fire for a week, we're really concerned about it" 2 years ago!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 04/24/2021 02:53 am
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???

The pillars are not fully filled all the way with concrete - yet. (probably only 80-85% to the top) But there is rebar extending up all the way to the top, and these hanging cylinders are placed between the rebar. Then the rest of the concrete is pureed though the center hole in the cap. (I believe)

It's very easy to imagine a flange hidden inside the tube, similar to the one we see on top of the new rebar, that sticks out a foot or two from the existing concrete for them to bolt the new rebar to before they fill it over with concrete.
The primary rebar cage bolt alignment plates very likely are not permanent. The central hole is for crew access for rebar and concrete work. The rebar cage extensions will bolt on after the alignment plate is removed and vertical pipe extensions welded. Alignment plates are a thing. Hammers after pour will "always" be required anyway for the sake of hammering on stuff.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 04/24/2021 03:09 am
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???

The pillars are not fully filled all the way with concrete - yet. (probably only 80-85% to the top) But there is rebar extending up all the way to the top, and these hanging cylinders are placed between the rebar. Then the rest of the concrete is pureed though the center hole in the cap. (I believe)

It's very easy to imagine a flange hidden inside the tube, similar to the one we see on top of the new rebar, that sticks out a foot or two from the existing concrete for them to bolt the new rebar to before they fill it over with concrete.
The primary rebar cage bolt alignment plates very likely are not permanent. The central hole is for crew access for rebar and concrete work. The rebar cage extensions will bolt on after the alignment plate is removed and vertical pipe extensions welded. Alignment plates are a thing. Hammers after pour will "always" be required anyway for the sake of hammering on stuff.

Those plates are three or four inches thick, they will be part of the final product, imo.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 04/24/2021 03:19 am
What are the tie-rods in this picture embedded in?  In the video it looks like they're just hanging free, and not constrained by anything as the plate is lowered.  Uncured cement?  And if the latter, what of the interface between the previously cured cement inside the tubes and the new stuff?  ???

The pillars are not fully filled all the way with concrete - yet. (probably only 80-85% to the top) But there is rebar extending up all the way to the top, and these hanging cylinders are placed between the rebar. Then the rest of the concrete is pureed though the center hole in the cap. (I believe)

It's very easy to imagine a flange hidden inside the tube, similar to the one we see on top of the new rebar, that sticks out a foot or two from the existing concrete for them to bolt the new rebar to before they fill it over with concrete.
The primary rebar cage bolt alignment plates very likely are not permanent. The central hole is for crew access for rebar and concrete work. The rebar cage extensions will bolt on after the alignment plate is removed and vertical pipe extensions welded. Alignment plates are a thing. Hammers after pour will "always" be required anyway for the sake of hammering on stuff.

Those plates are three or four inches thick, they will be part of the final product, imo.
Just to weld this on top of them. I see it the other way as the plates lack pins for concrete.

This is the next sections of pipe to go on: https://forum.nasaspaceflight.com/index.php?topic=52398.msg2225587#msg2225587
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 04/24/2021 04:44 am
The fact that they still aren't ready for sf in a whole week now is a cause of concern
SN15 is ahead of the pace of every other SS prototype.  They missed an internal target date by a week.  They do that all the time. All schedules are aspirational, and week long delays are the norm.  This delay is entirely inconsequential.

Edit: not taking things personal
Maybe (and especially since NASA committed to Lunar) they are taking things a little slower to improve chances of success.

I imagine it would look really good for SN15 to land in one piece just after the contract award, with more crew on ISS courtesy of CR 2 and a new NASA admin at the helm.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 04/24/2021 05:38 am
Well there’s also the pragmatic fact that they are wrapped up in building GSE tanks along with SN-16&17. Given we’re not seeing pieces of SN 18 or 19 yet but we have seen SN-20, it may be helpful to avoid having to build them if they can just start landing 15,16 etc until they’re through the GSE building interruption to Starship tank manufacturing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/24/2021 09:41 am
The fact that they still aren't ready for sf in a whole week now is a cause of concern
SN15 is ahead of the pace of every other SS prototype.  They missed an internal target date by a week.  They do that all the time. All schedules are aspirational, and week long delays are the norm.  This delay is entirely inconsequential.

Edit: not taking things personal
Maybe (and especially since NASA committed to Lunar) they are taking things a little slower to improve chances of success.

I imagine it would look really good for SN15 to land in one piece just after the contract award, with more crew on ISS courtesy of CR 2 and a new NASA admin at the helm.
Although I see your point, I disagree. Starship is its own experimental project with its own cadence. If SpaceX took NASAs attitude to development, we’d already be in a bad situation to developmental knock backs. Maybe they’ve taken the foot off the pedal to not clash the two events considering they had personnel onboard Falcon 9. But still, these teams are probably separate and don’t mix resources to keep up the cadence (imagine there is some support from Hawthorne on continuous feedback in engine and design development).

As someone else has said, it’s probably other factors that are delaying SF and launch. Not sure sticking SN15 is priority for media and public relation reasons. If it fails, it fails gracefully with data (plus they have 16-19 test vehicles if they need more time to test bugs they find with 15).

I think they are solving the last few % of known bugs to get a good landing and conduct reusability testing (send these starships off more than once). This is the beauty of allowing failures to occur in a controlled manor. Media have seen it enough times to expect it now.


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Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/24/2021 09:55 am
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Moritz Kibler on 04/24/2021 10:10 am
And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

It is very likely at this point. One of the labels on a BN2 section showed it as a test tank and also no sections except for FWD and AFT dome were spotted so far. Also the fact that another dome is labeled B2.1 could be another indication of that (similar to the SN7 series). It is also possible that BN2 is a test tank and B2.1 the full booster but it's not known.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/24/2021 10:27 am
SpaceX adjusts how careful they are with testing based on how the previous tests have gone. They’ve had 4 explosions on landing in a row, so they’ve recalibrated a bit.

Also, prototypes are getting more expensive. Not too long now until the orbital prototype which will have residual value beyond just a single test flight. More expensive and valuable vehicles means you start putting more money and effort into mission assurance.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/24/2021 12:00 pm
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

He does. But as stated above, looking at parts it makes sense.

For BN2 we have a sleeved thrust dome with only 3 rings, and no mount on bottom like BN1 had.

However, Mary spotted a BN thrust dome sleeve that was flipped the other day, and it has those bottom mounts, which signals raptors.

The new BN dome Mary spotted yesterday is very likely for BN2.1 rather than for BN3. Could be wrong though.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/24/2021 12:15 pm
BN 2.0 has the structure on top of the dome right? Could part of it’s testing be fitting Starship on top for a fit check? Maybe even a fueling test of Starship through it? Basically just testing the interstage portion of BN.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/24/2021 01:06 pm
BN 2.0 has the structure on top of the dome right? Could part of it’s testing be fitting Starship on top for a fit check? Maybe even a fueling test of Starship through it? Basically just testing the interstage portion of BN.

IMO an interstage test article is possible, since that part would need to work for tens of times.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/24/2021 01:11 pm
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

He does. But as stated above, looking at parts it makes sense.

For BN2 we have a sleeved thrust dome with only 3 rings, and no mount on bottom like BN1 had.

However, Mary spotted a BN thrust dome sleeve that was flipped the other day, and it has those bottom mounts, which signals raptors.

The new BN dome Mary spotted yesterday is very likely for BN2.1 rather than for BN3. Could be wrong though.
So, IIUC, they will mate the aft and forward sections skipping everything in between. Why are they building a test tank for Superheavy? This is a big change, BN2 was said to be a flying prototype, now itis only a test tank made of a couple of rings.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/24/2021 01:57 pm
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

He does. But as stated above, looking at parts it makes sense.

For BN2 we have a sleeved thrust dome with only 3 rings, and no mount on bottom like BN1 had.

However, Mary spotted a BN thrust dome sleeve that was flipped the other day, and it has those bottom mounts, which signals raptors.

The new BN dome Mary spotted yesterday is very likely for BN2.1 rather than for BN3. Could be wrong though.
So, IIUC, they will mate the aft and forward sections skipping everything in between. Why are they building a test tank for Superheavy? This is a big change, BN2 was said to be a flying prototype, now itis only a test tank made of a couple of rings.

Very likely to test the SH thrust dome and puck under high loads. The entire dome and puck are unproven and putting it through its paces before strapping a butt load of raptors onto it seems smart.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/24/2021 02:15 pm
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

He does. But as stated above, looking at parts it makes sense.

For BN2 we have a sleeved thrust dome with only 3 rings, and no mount on bottom like BN1 had.

However, Mary spotted a BN thrust dome sleeve that was flipped the other day, and it has those bottom mounts, which signals raptors.

The new BN dome Mary spotted yesterday is very likely for BN2.1 rather than for BN3. Could be wrong though.
So, IIUC, they will mate the aft and forward sections skipping everything in between. Why are they building a test tank for Superheavy? This is a big change, BN2 was said to be a flying prototype, now itis only a test tank made of a couple of rings.

Very likely to test the SH thrust dome and puck under high loads. The entire dome and puck are unproven and putting it through its paces before strapping a butt load of raptors onto it seems smart.

Could the thrust ram be used for this too?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 04/24/2021 03:51 pm
Given the major changes to the BN2.x design informed by actually building the BN1 path finder, such as swapping the fuel and oxidizer tanks, some tank testing does not seem remiss. Whether the test dome, tank or complete improved booster is called 2.0, 2.1 or 3.0 is the sort of OCD naming detail that does not change the actual engineering involved. Musk is certainly not afraid to change names or plans, but given public statements that "BN2" will fly I rather suspect that the path of least resistance for PR reasons will be a naming system that is somewhat "flexible". Even if that ends up requiring 2.1 be before 2.0 in the scheme of things. ::)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: abaddon on 04/24/2021 04:13 pm
Also, prototypes are getting more expensive.
Are they?  Yes, they're adding stuff, but they're also (presumably) getting better at making them.  Do you have any evidence that they're getting more expensive?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BT52 on 04/24/2021 04:23 pm

Very likely to test the SH thrust dome and puck under high loads. The entire dome and puck are unproven and putting it through its paces before strapping a butt load of raptors onto it seems smart.

Could the thrust ram be used for this too?

Why not. I think they will use "nosecone" MECO test jig just for that. They just add more hydraulic cylinders and rejig the whole apparatus and u got way to test dynamic loads on structure on top and bottom.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/24/2021 04:30 pm
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

He does. But as stated above, looking at parts it makes sense.

For BN2 we have a sleeved thrust dome with only 3 rings, and no mount on bottom like BN1 had.

However, Mary spotted a BN thrust dome sleeve that was flipped the other day, and it has those bottom mounts, which signals raptors.

The new BN dome Mary spotted yesterday is very likely for BN2.1 rather than for BN3. Could be wrong though.
So, IIUC, they will mate the aft and forward sections skipping everything in between. Why are they building a test tank for Superheavy? This is a big change, BN2 was said to be a flying prototype, now itis only a test tank made of a couple of rings.

Very likely to test the SH thrust dome and puck under high loads. The entire dome and puck are unproven and putting it through its paces before strapping a butt load of raptors onto it seems smart.

Could the thrust ram be used for this too?
If by "thrust ram" you refer to the whole hydraulic thrust simulation fixture they've used a number of times to apply force to Starship engine mounts and TVC attachments during pressure tests, no.  It's configured for Starship seal level Raptor mounts, and would not match the geometry of Superheavy.  That said, it would be unsurprising to see a similar article appear soon that was built to test the SH thrust structure.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/24/2021 04:51 pm
Also, prototypes are getting more expensive.
Are they?  Yes, they're adding stuff, but they're also (presumably) getting better at making them.  Do you have any evidence that they're getting more expensive?
Yes, because they added more stuff to them and are using more quality control measures. That's "evidence." And the earlier ones were manufacturing pathfinders even more than the current ones are, so their effective cost for testing purposes was lower than current ones.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 04/24/2021 05:03 pm
Also, prototypes are getting more expensive.
Are they?  Yes, they're adding stuff, but they're also (presumably) getting better at making them.  Do you have any evidence that they're getting more expensive?
Yes, because they added more stuff to them and are using more quality control measures. That's "evidence." And the earlier ones were manufacturing pathfinders even more than the current ones are, so their effective cost for testing purposes was lower than current ones.
You could say they’re becoming less expensive because time-to-build is less, time to assemble is less and time to launch is getting less.

Electronics is peanuts and software vs raw materials (that would stay constant, then get less as they obtain more steel etc)


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Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 04/24/2021 05:09 pm
Avionics may be a substantial portion of the value of a vehicle that you build quickly.

And again, the earlier vehicles were mostly valuable in terms of being manufacturing pathfinders. With those paths already being found, the newer ones cost SpaceX proportionally more for testing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/24/2021 07:47 pm
Guys, launch mount discussion belongs to the Launch Site thread ---> https://forum.nasaspaceflight.com/index.php?topic=49086.0

And, @_brendan_lewis diagram shows BN2 as a test tank. Is this true?(I'm guessing it's some insider info from L2 or something?)

He does. But as stated above, looking at parts it makes sense.

For BN2 we have a sleeved thrust dome with only 3 rings, and no mount on bottom like BN1 had.

However, Mary spotted a BN thrust dome sleeve that was flipped the other day, and it has those bottom mounts, which signals raptors.

The new BN dome Mary spotted yesterday is very likely for BN2.1 rather than for BN3. Could be wrong though.
So, IIUC, they will mate the aft and forward sections skipping everything in between. Why are they building a test tank for Superheavy? This is a big change, BN2 was said to be a flying prototype, now itis only a test tank made of a couple of rings.

Very likely to test the SH thrust dome and puck under high loads. The entire dome and puck are unproven and putting it through its paces before strapping a butt load of raptors onto it seems smart.

Could the thrust ram be used for this too?
If by "thrust ram" you refer to the whole hydraulic thrust simulation fixture they've used a number of times to apply force to Starship engine mounts and TVC attachments during pressure tests, no.  It's configured for Starship seal level Raptor mounts, and would not match the geometry of Superheavy.  That said, it would be unsurprising to see a similar article appear soon that was built to test the SH thrust structure.

Has the thrust ram ever used to stress an article to faiulure? IIRC no, but i could have  missed some test. Is there an obviouse controindication to do that? (for example a shower of liquid nitrogen after a tank rapture will damage it significantly?).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/24/2021 09:28 pm
There is a new method for creating metal composites.
It is easy, cheap and offers enormous possibilities - finally, we can easily create metal objects with a bone-like structure...

A fragment of engine nozzle:

Welcome to NSF.

Is that photo a part from a SpaceX rocket produced in Boca Chica? If not, please consider a more appropriate thread and probably NSF subforum for general aerospace manufacturing techniques.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Gonz58 on 04/24/2021 10:45 pm
https://forum.nasaspaceflight.com/index.php?topic=49086.0


Has the thrust ram ever used to stress an article to faiulure? IIRC no, but i could have  missed some test. Is there an obviouse controindication to do that? (for example a shower of liquid nitrogen after a tank rapture will damage it significantly?).

There hadn't been failure because of trust ram, but when SN3 RUD and crumpled and the tank fail, a lot of ln2 fall down on the trust ram. It get badly damaged
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/25/2021 12:05 am
Did SN18 & SN19 get skipped?  ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/25/2021 12:34 am
Also, prototypes are getting more expensive.
Are they?  Yes, they're adding stuff, but they're also (presumably) getting better at making them.  Do you have any evidence that they're getting more expensive?
Yes, because they added more stuff to them and are using more quality control measures. That's "evidence." And the earlier ones were manufacturing pathfinders even more than the current ones are, so their effective cost for testing purposes was lower than current ones.
The finish quality has gone up. The complexity has gone up. The precision has gone up. The tooling has expanded. The propellant quantity has gone up. The FAA oversight seems to have gone up.


Counter to this, the experience, from admin to engineering to hard hats to even their vendors, has gone up. Is guess expense has gone up but well below an order of magnitude.


When the engine count goes up the cost will spike, possibly mitigated by engine reuse when they don't RUD. Let's hope for lots of mitigation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/25/2021 01:23 am
When the engine count goes up the cost will spike, possibly mitigated by engine reuse when they don't RUD. Let's hope for lots of mitigation.
It's unlikely they'll crash as many (if any) boosters.  Also the first flights won't be using the full 28 (or whatever it is today).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 04/25/2021 03:51 am
Slightly OT: Did you all see the announcement that Elon Musk will be hosting Saturday Night Live on May 8?
This is not a joke.

I'm guessing there won't be an SN flight on that day ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 04/25/2021 05:02 am
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/25/2021 05:25 am
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.

Starsky would work for me, and is easily expandable for when they get a second cat
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsnellenberger on 04/25/2021 01:47 pm
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.
Interesting dome:  Starship pad & orbital fueling/refueling drogue???
Cat name: Better to just ask - the cat knows its name.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 04/25/2021 02:17 pm
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.
Interesting dome:  Starship pad & orbital fueling/refueling drogue???
Cat name: Better to just ask - the cat knows its name.
 
 
Its an aft dome, You can see the Raptor mounts on the top. The positioning of the weird section in question matches where an RVac would be located. 
The refueling system will likely be much more discrete, probably using the same connections the GSE uses to fuel through the SH.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsnellenberger on 04/25/2021 03:05 pm
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.
Interesting dome:  Starship pad & orbital fueling/refueling drogue???
Cat name: Better to just ask - the cat knows its name.
 
 
Its an aft dome, You can see the Raptor mounts on the top. The positioning of the weird section in question matches where an RVac would be located. 
The refueling system will likely be much more discrete, probably using the same connections the GSE uses to fuel through the SH.

Yes, I saw that it is a Starship aft dome. I suppose it could be an RVac mount, but wouldn’t there be 6 hubcaps in that case? For hydraulic testing purposes, even if they don’t install all 6 Raptors for the initial flights...

We don’t know the details of the “final” Starship, Booster, *and* Tanker interface design yet, aside from concept art and the requirement that it be fully autonomous. If Starship and Tanker dock tail-to-tail (how? using what hardware?  GigaIDSS?), maybe they’ll retain the prototype’s GSE umbilical design. Or maybe the prototypes are using the Booster GSE design for the time being, and the first Starship that launches atop a Booster will be different...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 04/25/2021 03:16 pm
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.
Interesting dome:  Starship pad & orbital fueling/refueling drogue???
Cat name: Better to just ask - the cat knows its name.
 
 
Its an aft dome, You can see the Raptor mounts on the top. The positioning of the weird section in question matches where an RVac would be located. 
The refueling system will likely be much more discrete, probably using the same connections the GSE uses to fuel through the SH.

Ain't this dome first seen few weeks back?
https://twitter.com/RGVaerialphotos/status/1380627708430974978/photo/1
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 04/25/2021 03:18 pm
Interesting dome.
SpaceX's black and white cat. The first time I saw the can was way back when Mk1 was being built.
 
 
RVac mounting pathfinder?   
 
Shall we start a poll to name the cat? I vote StarKitty keeping on the theme.
Interesting dome:  Starship pad & orbital fueling/refueling drogue???
Cat name: Better to just ask - the cat knows its name.
 
 
Its an aft dome, You can see the Raptor mounts on the top. The positioning of the weird section in question matches where an RVac would be located. 
The refueling system will likely be much more discrete, probably using the same connections the GSE uses to fuel through the SH.

Yes, I saw that it is a Starship aft dome. I suppose it could be an RVac mount, but wouldn’t there be 6 hubcaps in that case? For hydraulic testing purposes, even if they don’t install all 6 Raptors for the initial flights...

We don’t know the details of the “final” Starship, Booster, *and* Tanker interface design yet, aside from concept art and the requirement that it be fully autonomous. If Starship and Tanker dock tail-to-tail (how? using what hardware?  GigaIDSS?), maybe they’ll retain the prototype’s GSE umbilical design. Or maybe the prototypes are using the Booster GSE design for the time being, and the first Starship that launches atop a Booster will be different...
Emphasis added - No, there will only be 3 "hubcaps" as there will only be three RVacs. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 04/25/2021 04:56 pm


https://twitter.com/ercxspace/status/1386059531839361030

Quote
To the moon.

#SpaceX #Starship

That's gorgeous, but if they really intend to catch Starships too, then the catcher mechanism must probably do so while a Superheavy is located on the launch mount, so has to swivel at least partway around the tower - maybe even all the way to the back.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Taxidermista on 04/25/2021 05:43 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JohnM on 04/25/2021 05:46 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?

SpaceX is working on Phobos and Deimos
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 04/25/2021 05:53 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?

SpaceX is working on Phobos and Deimos
And some day maybe their namesakes, too!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 04/25/2021 05:56 pm
We don’t know the details of the “final” Starship, Booster, *and* Tanker interface design yet, aside from concept art and the requirement that it be fully autonomous. If Starship and Tanker dock tail-to-tail (how? using what hardware?  GigaIDSS?), maybe they’ll retain the prototype’s GSE umbilical design. Or maybe the prototypes are using the Booster GSE design for the time being, and the first Starship that launches atop a Booster will be different...
   
 
Well, if you think about the problem then there are a few "simple" solutions keeping in Musk's philosophy of the best part is no part. 
Develop the staging connection in such a way that is androgynous, so 2 Starships could dock tail to tail. Think along the lines of docking latches. "GigaIDSS" not needed. 
Ditto with the GSE connections, design in such a way that 2 SS can interface, as well as SS & SH.   
 
A probe and drogue system? The best part is no part. 
 
However, this is probably leaning on off topic for this thread so I will leave this here. We're all just speculating (mostly) and we all know that the design isnt final, but I will say with 99.99% confidence that this has nothing to do with refueling. I wouldn't be so quick to dismiss arguments like that, especially when said arguments are just speculation. 
   
But hey, If I am wrong, I will do a Peter Beck and eat a hat.
 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 04/25/2021 05:59 pm
Ain't this dome first seen few weeks back?
https://twitter.com/RGVaerialphotos/status/1380627708430974978/photo/1
 
 
Welp, I missed that. *shrug*
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 04/25/2021 06:12 pm
This dome has been around for weeks if not months. Someone guessed that it was probably meant for SN12 but became a "pathfinder dome" after SN12-14 got scrapped.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mpusch on 04/25/2021 07:45 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?

Doesn't seem to be a limiting factor at all. If they were doing static fires 5 days a week you might have a point.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CrazySpace on 04/26/2021 10:57 am
works in the lift on SN15 are now finished
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: deadman1204 on 04/26/2021 01:36 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?

SpaceX isn't at a point to test a Starship like 300 days out of the year. This isn't an issue. They simply schedule their work around the limitations.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/26/2021 03:52 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?
In case you haven't noticed, they're building a launch site there, which would be hard to do if it was shut down for testing 365 days a year.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Taxidermista on 04/26/2021 05:17 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?
In case you haven't noticed, they're building a launch site there, which would be hard to do if it was shut down for testing 365 days a year.

I think it is shut down 104 days a year, not 365.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/26/2021 05:53 pm
https://twitter.com/starshipgazer/status/1386537852117286914

Quote
Night work on SN15:

Is this bright yellow diagonal bundle of cabling new to SN15, or just more prominent due to its color?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/26/2021 06:02 pm
yes, placement of almost everything is different on sn15, aerocovers are even different
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/26/2021 06:03 pm
https://twitter.com/starshipgazer/status/1386537852117286914

Quote
Night work on SN15:

Is this bright yellow diagonal bundle of cabling new to SN15, or just more prominent due to its color?

Not new. Been there since SN8 I believe.

Edit: never mind!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/26/2021 07:15 pm
Not new. Been there since SN8 I believe.

Edit: never mind!

I know there has been cabling on prior vehicles but SN15’s appear to be connected to feed through fittings or openings in a very different location, resulting in a much longer diagonal run compared to prior versions. That’s what I’m getting at.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/27/2021 02:26 am
From today's NSF summary video.  There's some ring stacks been produced and have a metal hoop on top.  Is this a stiffener to prevent flopping in the wind?  Possibly because it's happened before?  Possibly because they're thinner steel?

Have I missed these for a while, or are these new?

(https://i.imgur.com/9GnapgY.png)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 04/27/2021 02:52 am
From today's NSF summary video.  There's some ring stacks been produced and have a metal hoop on top.  Is this a stiffener to prevent flopping in the wind?  Possibly because it's happened before?  Possibly because they're thinner steel?

Have I missed these for a while, or are these new?

(https://i.imgur.com/9GnapgY.png)

Almost certainly wind related and a very smart move. They have been around for about a month now. I assume they will be manufacturing more of them as there are a number of stacks that do not have them - though they may have internal stiffeners inside them.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/27/2021 04:32 am
Is there no name/number for the nosecone section in the weird test structure? That's kind of surprising, if so, given that SN7.2 (for example) was just a tank...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chief on 04/27/2021 11:03 am
Is there no name/number for the nosecone section in the weird test structure? That's kind of surprising, if so, given that SN7.2 (for example) was just a tank...

Several weeks back Jack photographed a label on it that said "Serial #: NC12":

https://forum.nasaspaceflight.com/index.php?topic=52398.msg2205065#msg2205065
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/27/2021 12:27 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?
In case you haven't noticed, they're building a launch site there, which would be hard to do if it was shut down for testing 365 days a year.
I think it is shut down 104 days a year, not 365.
I think the point was that if SpaceX could and did use Boca Chica 365 days a year for testing, they wouldn't be able to build the orbital launch site as they would always need to evacuate the area due to testing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 04/27/2021 12:37 pm
When he eventually buys all the property in the area, and gets orbital.  Maybe he can get the county to "quit claim" the roads and he can take them over and close them at will.  However, the beach is still supposed to be public property to the high tide line.  I know in Florida, you may have a high rise condo in front of the beach.  The beach is still public property. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/27/2021 03:46 pm
104 days per year SpaceX can't test its prototypes at Boca Chica, 28.4% of the time wasted. Why this is not driving Musk crazy and looking for alternatives?
In case you haven't noticed, they're building a launch site there, which would be hard to do if it was shut down for testing 365 days a year.
I think it is shut down 104 days a year, not 365.
I think the point was that if SpaceX could and did use Boca Chica 365 days a year for testing, they wouldn't be able to build the orbital launch site as they would always need to evacuate the area due to testing.

I agree, and, after that, why should Musk be driving crazy and sheaching for alternatives, because there aren't other places like BC with the same situation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/27/2021 03:55 pm
Targeting a second static fire test tomorrow. Mary has received overpressure notice.

Do you think that Elon last tweet about a completed static fire outdated this or will they atill attempt a second SF? Does "completed" mean "sucessful"?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 04/27/2021 04:14 pm
Road closure for today still stands!

I think we need a camera at the gas-well-side! Start-tower-sections will go up there!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/27/2021 05:25 pm
Targeting a second static fire test tomorrow. Mary has received overpressure notice.

Do you think that Elon last tweet about a completed static fire outdated this or will they atill attempt a second SF? Does "completed" mean "sucessful"?

It’s another static fire that they will be attempting today from the headers.  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Tangilinear Interjar on 04/27/2021 05:31 pm
Something I noticed on the integration tower columns that may inform a bit about possible catch mechanism design.

Three of the four columns have two line patterns of precisely placed holes on either side of the column. These holes are not threaded so I wonder if they are alignment holes for some structure that will ultimately be welded to the tower.

Someone with better mechanical engineering knowledge than me should comment but it seems to me that a mechanism that translates up and down the tower but needs to stay precise and tightly integrated to the tower would only want three rails for proper constraint.

Edit, just realized that this maybe should have been in the launchsite thread. Copied it over there, please delete if needed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/27/2021 06:30 pm
Targeting a second static fire test tomorrow. Mary has received overpressure notice.

Do you think that Elon last tweet about a completed static fire outdated this or will they atill attempt a second SF? Does "completed" mean "sucessful"?

It’s another static fire that they will be attempting today from the headers.  :)

Great point.

Is there any way we can understand if a static fire is from headers or main tanks? I thought we could look at LOx header frost, but I saw happened in every SF, so it is not a good indicator about this.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/27/2021 06:47 pm
Targeting a second static fire test tomorrow. Mary has received overpressure notice.

Do you think that Elon last tweet about a completed static fire outdated this or will they atill attempt a second SF? Does "completed" mean "sucessful"?

It’s another static fire that they will be attempting today from the headers.  :)

Great point.

Is there any way we can understand if a static fire is from headers or main tanks? I thought we could look at LOx header frost, but I saw happened in every SF, so it is not a good indicator about this.

We don’t know for sure, but I think they just fill the LOX header every firing from the main tanks just for data/rehearsal/proofing to verify them.

As for how to know the difference, its kinda hard to know for sure, but today one way to know for sure is if they decide to fill just the headers and the headers only, because if that is the case, then prop load times should be relatively quick, and there shouldn’t be any sort of frost on the main tanks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/27/2021 06:58 pm
Judging from the weather, the best chance for a flight this week is Friday:

https://docs.google.com/document/d/1WFcMJv9pN8X5EqBB60cHvXtmUemJrkS1ZamKI2Lj2Tw/edit

TFR for Wednesday got pulled, won't surprise me if Thursday gets pulled as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/28/2021 04:56 pm
I've never seen the discussion thread go days without posts.  What happened?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 04/28/2021 06:10 pm
I've never seen the discussion thread go days without posts.  What happened?

Too many splinter threads. Most of the action right now is going on at the launch sites, and facilities which all have their own threads.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 04/28/2021 06:41 pm
Where's the splinter thread about the splinters thread?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: _MECO on 04/28/2021 06:43 pm
Where's the splinter thread about the splinters thread?
Same place all these comments are going very soon.
https://forum.nasaspaceflight.com/index.php?topic=53586.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 04/28/2021 08:18 pm
  Looking forward to SN15 test flight, but don't think it will happen until all the high dollar cranes are off site. Would be interesting to know what the work contract says in regards to 'test flights/rocket activity' for the none SpaceX cranes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/28/2021 08:23 pm
  Looking forward to SN15 test flight, but don't think it will happen until all the high dollar cranes are off site. Would be interesting to know what the work contract says in regards to 'test flights/rocket activity' for the none SpaceX cranes.
I’m sure SpaceX is liable for any damage. In fact their launch license for the site requires something like a $190M bond. They’re not looking to wreck expensive rental equipment, but it’s insured.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/28/2021 10:57 pm
weather forecast looks like best day for flight is Thursday.   Some clouds, light wind, no storms.

Friday thunderstorms predicted

https://www.wunderground.com/forecast/us/tx/boca-chica
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: clongton on 04/29/2021 12:09 am
Interesting. The SLS Core Stage arrived at KSC today by barge. I wonder how Starship will arrive?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/29/2021 12:11 am
Interesting. The SLS Core Stage arrived at KSC today by barge. I wonder how Starship will arrive?

The KSC Starships (and I think that could be the Lunar Starship) will be built in Florida. 

There will be multiple ship yards.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: clongton on 04/29/2021 12:14 am
Interesting. The SLS Core Stage arrived at KSC today by barge. I wonder how Starship will arrive?

The KSC Starships (and I think that could be the Lunar Starship) will be built in Florida. 
There will be multiple ship yards.

Why not just fly it in?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Malatrope on 04/29/2021 12:26 am
Interesting. The SLS Core Stage arrived at KSC today by barge. I wonder how Starship will arrive?

Right in the middle of the biggest landing zone, with brass band and cheerleaders to the side. Way to the side.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/29/2021 12:31 am
Please stop posting duplicates in the update thread, I posted what you said already.

Flight of SN15 is targeted for NET Friday. Status:
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 04/29/2021 12:35 am
Right in the middle of the biggest landing zone, with brass band and cheerleaders to the side. Way to the side.

There's only one correct choice for them to play.  ;D (https://www.youtube.com/watch?v=ciFwOndlBxE)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thundermusicz on 04/29/2021 12:55 am
Right in the middle of the biggest landing zone, with brass band and cheerleaders to the side. Way to the side.

There's only one correct choice for them to play.  ;D (https://www.youtube.com/watch?v=ciFwOndlBxE)
How long until the Space Force gets their own song? And back to the topic of prototypes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Everything Space on 04/29/2021 01:07 am
Please stop posting duplicates in the update thread, I posted what you said already.

Flight of SN15 is targeted for NET Friday. Status:

There is an additional tweet and information in the reply.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/29/2021 01:13 am
Please stop posting duplicates in the update thread, I posted what you said already.

Flight of SN15 is targeted for NET Friday. Status:

There is an additional tweet and information in the reply.

You’re pimping your own content to boost your own traffic and duplicating the original information, already posted.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/29/2021 01:26 am
How long until the Space Force gets their own song?
They'll probably just steal the Star Trek song and change one note.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/29/2021 03:10 am
Do we know what exactly the nose cone proof test was testing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 04/29/2021 03:27 am
This new tower is going to be epic. I love it!

photo: BocaChicaGal
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 04/29/2021 04:29 am
It looks like the section with all the heat tiles that came out of tent 3 will be a base for the next nose.
 The next SN or gse tank or whatever it is has started rising in Midbay.

My guess is it will be an SN or BN, because IIRC the GSE tanks haven't had the access hatches. I would think that the GSE tanks don't need the same amount of interior work after stacking.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 04/29/2021 05:51 am
What is going on iside the Highbay ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jumparound on 04/29/2021 07:07 am
Just wondering... whats happening to the discared steel at the scapyard? i did a forum search but could'nt find anything.
That BN1 will yield a few tons ;-)

Is it being taken away? Will it turn out to be recycled as cybertrucks? questions... questions...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 04/29/2021 08:48 am
What is going on iside the Highbay ?
It's vacant at the moment. SN16 will likely be next to go in for stacking.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oersted on 04/29/2021 09:32 am
This new tower is going to be epic. I love it!

photo: BocaChicaGal

I love the way they placed it so it points a corner towards the pad. Such a clever way of deflecting the plume impact.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/29/2021 10:46 am
It looks like the section with all the heat tiles that came out of tent 3 will be a base for the next nose.
 The next SN or gse tank or whatever it is has started rising in Midbay.

My guess is it will be an SN or BN, because IIRC the GSE tanks haven't had the access hatches. I would think that the GSE tanks don't need the same amount of interior work after stacking.

What was stacked was SN17’s 3 ring common dome section (spotted with full tiling!) , onto a 4 ring LOX section.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: novo2044 on 04/29/2021 12:58 pm
I've always been impressed without little steel it takes to support a skyscraper, or tall crane.  So looking at this monster makes me wonder, if all it's doing it lifting the stack does it not seem somewhat overbuilt?  Like by a fair margin?  I assume they plan on testing the tower-catch mechanism so this level of robustness might be appropriate.  But big steel isn't something I am too familiar with.

Any experts comment on what sort of loads concrete filled steel columns of that size could support?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oersted on 04/29/2021 01:04 pm
It will have to withstand hundreds of powerful 28-Raptor rocket plumes up and down its length. It had better be overbuilt!

Probably also a best to build it from the material that presents the smallest profile, so it offers as little resistance to the plume as possible.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 04/29/2021 01:16 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 04/29/2021 01:22 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?
Yes, that nosecone. The structural forces obviously can be replicated without having to use the actual aerodynamic forces itself
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: MTom on 04/29/2021 01:37 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?

This is the test stand for MaxQ stress test.
The forces at MaxQ are simulated with hydraulic cylinders.

Edit:
To clarify my statements, this is how I interpreted the Informations in this forum until now.
This is only my opinion, without space industry experience (armchair engineering :) )
If my interpretation will be wrong, sorry for that.

https://youtu.be/bLutbCpGcPo

Edit to add: now live
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 04/29/2021 01:56 pm
I'm gonna guess that the "stand" is actually an integrity test for "the claw" that will pick up and move the starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Prae_ on 04/29/2021 02:38 pm
I'm gonna guess that the "stand" is actually an integrity test for "the claw" that will pick up and move the starship.

A SpaceX employee posted a picture of him at the top on the crane and likely in breaking his NDA said it was for testing structural stress of orbital flight. (Max-Q and supersonic pressure forces on the nose tip propagating down the rest of the structure.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/29/2021 02:45 pm
I'm gonna guess that the "stand" is actually an integrity test for "the claw" that will pick up and move the starship.

A SpaceX employee posted a picture of him at the top on the crane and likely in breaking his NDA said it was for testing structural stress of orbital flight. (Max-Q and supersonic pressure forces on the nose tip propagating down the rest of the structure.)

More importantly, other folks known to have a track record of reliability and contacts within SpaceX have posted that it is a structural test stand, which had been theorized for some time anyway by those of us with engineering and test experience.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 04/29/2021 03:47 pm
I wonder if they'll use the rig to test to failure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 04/29/2021 04:02 pm
I wonder if they'll use the rig to test to failure.
Its the SpaceX way... we will see
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 04/29/2021 04:22 pm
Since TFR for tomorrow has not been removed we can assume that staic fires were succesfuls.  Why did they test in the last SF only one engine? Could be that the engine was suspect, and then showed instead ok at the second SF?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/29/2021 04:25 pm
Since TFR for tomorrow has not been removed we can assume that staic fires were succesfuls.  Why did they test in the last SF only one engine? Could be that the engine was suspect, and then showed instead ok at the second SF?

First firing was from main tanks, second was feeding from the header tanks, all is well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 04/29/2021 04:35 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?
LabPadre says lots of things.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/29/2021 06:27 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?
While Nomadd's reply is on point, I don't see any reason why they couldn't test max q without launching.  All max q means is the craft experiencing the maximum amount of structural load is going through the ship.  There are plenty of ways of testing structural load without launching things, and SpaceX certainly is gearing up to do a bunch of testing of structural load right there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 04/29/2021 06:35 pm
I've always been impressed without little steel it takes to support a skyscraper, or tall crane.  So looking at this monster makes me wonder, if all it's doing it lifting the stack does it not seem somewhat overbuilt?  Like by a fair margin?  I assume they plan on testing the tower-catch mechanism so this level of robustness might be appropriate.  But big steel isn't something I am too familiar with.

Any experts comment on what sort of loads concrete filled steel columns of that size could support?
Not any sort of expert, but the tower does not have to be lite, but it does need to support 100+ton lifts, probably catch similar weight and handle high (possibly hurricane strength) winds all with a height of some 470ft.

And not just once or for a couple of months but if successful for many years, in a highly corrosive environment.

So my armchair view - thicker/heavier is likely better.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 04/29/2021 06:38 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?
While Nomadd's reply is on point, I don't see any reason why they couldn't test max q without launching.  All max q means is the craft experiencing the maximum amount of structural load is going through the ship.  There are plenty of ways of testing structural load without launching things, and SpaceX certainly is gearing up to do a bunch of testing of structural load right there.

It means the nose cone test structure was tested yesterday, NOT SN15, the test structure and SN12 Nose/CH4 tank stack is being used to test nosecone and CH4 tank for MaxQ orbital flight loads to verify the steel wont buckle, hydraulic ram in the nose and (under CH4 tank) compress the nose and CH4 tank stack in a way that replicates orbital flight MaxQ loads, and the flap actuators are connected to hydraulic shocks to simulate aerodynamic load/drag to test lateral strain on nose section during MaxQ. The stack was most likely compressed with ambient N2 in yesterdays test to verify it is holding pressure, but I didn't see any flap movement so more tests are likely after SN15's test flight, possibly destructive tests to determine design limits.

Why there is confusion on which vehicle was tested yesterday is pretty sad, and it's obvious what the test structure is for... Cmon folks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 04/29/2021 07:06 pm
What is LabPadre referring to in his side bar "1st MaxQ test conducted"? Nose cone test? How could they test for MaxQ without launching?
While Nomadd's reply is on point, I don't see any reason why they couldn't test max q without launching.  All max q means is the craft experiencing the maximum amount of structural load is going through the ship.  There are plenty of ways of testing structural load without launching things, and SpaceX certainly is gearing up to do a bunch of testing of structural load right there.

It means the nose cone test structure was tested yesterday, NOT SN15, the test structure and SN12 Nose/CH4 tank stack is being used to test nosecone and CH4 tank for MaxQ orbital flight loads to verify the steel wont buckle, hydraulic ram in the nose and (under CH4 tank) compress the nose and CH4 tank stack in a way that replicates orbital flight MaxQ loads, and the flap actuators are connected to hydraulic shocks to simulate aerodynamic load/drag to test lateral strain on nose section during MaxQ. The stack was most likely compressed with ambient N2 in yesterdays test to verify it is holding pressure, but I didn't see any flap movement so more tests are likely after SN15's test flight, possibly destructive tests to determine design limits.

Why there is confusion on which vehicle was tested yesterday is pretty sad, and it's obvious what the test structure is for... Cmon folks.


I do not think anyone - certainly not me - thought this testing was happening on SN15.  With so much going on in the SpaceX forums it is next to impossible to stay up to date with everything - I completely missed the NSF stream on the nose structural changes - first thing I noticed was LabPadre brief note.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 04/29/2021 07:14 pm
I've always been impressed without little steel it takes to support a skyscraper, or tall crane.  So looking at this monster makes me wonder, if all it's doing it lifting the stack does it not seem somewhat overbuilt?  Like by a fair margin?  I assume they plan on testing the tower-catch mechanism so this level of robustness might be appropriate.  But big steel isn't something I am too familiar with.

Any experts comment on what sort of loads concrete filled steel columns of that size could support?
Not any sort of expert, but the tower does not have to be lite, but it does need to support 100+ton lifts, probably catch similar weight and handle high (possibly hurricane strength) winds all with a height of some 470ft.

And not just once or for a couple of months but if successful for many years, in a highly corrosive environment.

So my armchair view - thicker/heavier is likely better.

If you saw a railroad bridge built to a Safety Factor of 2.0, you'd probably never cross it because you'd think it looks too rickety. In general, structures like building have very, very large Safety Factors designed in to them, but you'd be amazed at the amount of force wind loads can place on a structure.

That being said, a building generally is built to withstand static loads (other than earthquake loads or wind loads) which stress the structure quite differently than the dynamic loads from catching a booster or lifting a SS with a crane attached to the top. Without any real analysis of dynamic and static forces this structure will see, it's all hand-waving and speculation on what is 'should' look like compared to other structures we generally see under construction.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 04/29/2021 07:32 pm
I've always been impressed without little steel it takes to support a skyscraper, or tall crane.  So looking at this monster makes me wonder, if all it's doing it lifting the stack does it not seem somewhat overbuilt?  Like by a fair margin?  I assume they plan on testing the tower-catch mechanism so this level of robustness might be appropriate.  But big steel isn't something I am too familiar with.

Any experts comment on what sort of loads concrete filled steel columns of that size could support?
Not any sort of expert, but the tower does not have to be lite, but it does need to support 100+ton lifts, probably catch similar weight and handle high (possibly hurricane strength) winds all with a height of some 470ft.

And not just once or for a couple of months but if successful for many years, in a highly corrosive environment.

So my armchair view - thicker/heavier is likely better.

If you saw a railroad bridge built to a Safety Factor of 2.0, you'd probably never cross it because you'd think it looks too rickety. In general, structures like building have very, very large Safety Factors designed in to them, but you'd be amazed at the amount of force wind loads can place on a structure.

That being said, a building generally is built to withstand static loads (other than earthquake loads or wind loads) which stress the structure quite differently than the dynamic loads from catching a booster or lifting a SS with a crane attached to the top. Without any real analysis of dynamic and static forces this structure will see, it's all hand-waving and speculation on what is 'should' look like compared to other structures we generally see under construction.
To add to the hand waving, I can imagine that catching 120 tons of moving rocket booster, significantly off centre, while a rocket exhaust heats up the lower sections of the tower requires some "significant" engineering.

It doesn't surprise me at all that this thing needs some absolutely huge supports.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: oldAtlas_Eguy on 04/29/2021 09:38 pm
Cross post from the Starlink : New FCC and ITU Filings thread.

41000 feet = 12.5km.

This is for all of those suborbital experiments over the next 2 months. Could be just one flight or SN15, 16, 17,18 and 19 -> as many as 5 flights. Though I doubt SpaceX could do more than just SN15,16, and 17 in the next 2 months.

For an orbital Starship would need another license.

There is an interesting possible reason that the license period ends 28 June 2021. That is a possible change in that SpaceX would not need to continue sub orbital testing anymore with the next flight after that date being an orbital test. Once flight to orbit is successful. At least the part about reaching orbit. Then the need to continue doing monthly sub orbital tests disappear with the fact that testing the landing capability of the SS can be better done and more cheaply as a byproduct of an Orbital launch with actual payloads to LEO such as some Starlink sats or some other on orbit tests like on orbit refueling that has to be done in orbit.

The reason is that this may be the first of more substantial evidence of that after the end of June the suborbital test program may be done or at least halted for a significant duration while orbital testing takes the drivers seat. With SN17 getting what looks like a possible full SS set of tiles that may be the last to be tested occuring in the second half of June. If SN15 goes real well SN16 build may be halted and SN17 build advanced so to do just the SN17 test with full tile set. So that experience and real flight data of the SS with tiles can be gathered prior to the orbital attempt.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ChrML on 04/29/2021 09:48 pm
By the looks of the booster catching tower, would it be strong enough to withstand a booster crashing into it?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SpeakertoAnimals on 04/29/2021 10:02 pm
By the looks of the booster catching tower, would it be strong enough to withstand a booster crashing into it?
First answer: depends on many variables. Mass, velocity, and impact angle come to mind immediately.
Second answer: sometimes yes, sometimes no.

More variables: point of impact, both vehicle and tower.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Redclaws on 04/29/2021 10:03 pm
By the looks of the booster catching tower, would it be strong enough to withstand a booster crashing into it?

Think about that for a second - what does “crashing in to it” mean?  That’s going to vary from a landing messy enough that the booster tanks crack and it maybe undergoes deflagration up to “terminal velocity impact”.

I think it might be hardened a bit so it could maybe survive a nearby impact or near zero speed landing failure, but crashing........
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SpeakertoAnimals on 04/29/2021 10:08 pm
By the looks of the booster catching tower, would it be strong enough to withstand a booster crashing into it?

Think about that for a second - what does “crashing in to it” mean?  That’s going to vary from a landing messy enough that the booster tanks crack and it maybe undergoes deflagration up to “terminal velocity impact”.

I think it might be hardened a bit so it could maybe survive a nearby impact or near zero speed landing failure, but crashing........
You forgot empty booster falling over with no engines installed. I think that is still a crash.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BlackholeLP on 04/29/2021 10:22 pm
Honestly, the prospect of tower crashes is another reason why I still think stage-2 catches with the tower are a bad idea. Super Heavy coming in vertically is one thing; a Starship coming in with the flip maneuver could potentially be far less reliable, and would near double the overall amount of catches the tower has to perform regardless; and for every SN8-11 style failure, that's another potential chance that that tower is out of commission for months if not years, depending on damage severity.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/29/2021 11:12 pm
Honestly, the prospect of tower crashes is another reason why I still think stage-2 catches with the tower are a bad idea. Super Heavy coming in vertically is one thing; a Starship coming in with the flip maneuver could potentially be far less reliable, and would near double the overall amount of catches the tower has to perform regardless; and for every SN8-11 style failure, that's another potential chance that that tower is out of commission for months if not years, depending on damage severity.

Given the tower is going to take < 3 months to build the first time, honestly the pessimism is unwarranted.

There will also be multiple launch locations for redundancy.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: xvel on 04/29/2021 11:48 pm
I can bet all my money that this tower will not be ready in 3 months.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 04/30/2021 12:09 am
Is anybody giving odds on the next nosecone to be tested/flogged being a chomper?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/30/2021 12:37 am
https://twitter.com/nextspaceflight/status/1387913496264798214?

https://twitter.com/nextspaceflight/status/1387831350011392000?

The FTS installation is missing from the checklist
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thundermusicz on 04/30/2021 12:41 am
Honestly, the prospect of tower crashes is another reason why I still think stage-2 catches with the tower are a bad idea. Super Heavy coming in vertically is one thing; a Starship coming in with the flip maneuver could potentially be far less reliable, and would near double the overall amount of catches the tower has to perform regardless; and for every SN8-11 style failure, that's another potential chance that that tower is out of commission for months if not years, depending on damage severity.
I believe the point of catching Starships is that they wouldn't have to do the flip; it would be caught horizontally. I'm pretty sure this would have to be done with some other structure, but I also have no idea how you would make a system that can do that...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/30/2021 01:02 am
Honestly, the prospect of tower crashes is another reason why I still think stage-2 catches with the tower are a bad idea. Super Heavy coming in vertically is one thing; a Starship coming in with the flip maneuver could potentially be far less reliable, and would near double the overall amount of catches the tower has to perform regardless; and for every SN8-11 style failure, that's another potential chance that that tower is out of commission for months if not years, depending on damage severity.
I believe the point of catching Starships is that they wouldn't have to do the flip; it would be caught horizontally. I'm pretty sure this would have to be done with some other structure, but I also have no idea how you would make a system that can do that...

Catching Starship is not feasible, if only because it can't be done for Mars. Starship itself - as envisioned - will always need to transition from bellyflop to vertical.

If Elon scraps the current concept and goes to a "Space:1999 Eagle Transporter" style horizontal lander architecture, all bets are off. But it won't be "Starship" as we know it today and is waaaay off-topic for this thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: M.E.T. on 04/30/2021 01:16 am
Honestly, the prospect of tower crashes is another reason why I still think stage-2 catches with the tower are a bad idea. Super Heavy coming in vertically is one thing; a Starship coming in with the flip maneuver could potentially be far less reliable, and would near double the overall amount of catches the tower has to perform regardless; and for every SN8-11 style failure, that's another potential chance that that tower is out of commission for months if not years, depending on damage severity.
I believe the point of catching Starships is that they wouldn't have to do the flip; it would be caught horizontally. I'm pretty sure this would have to be done with some other structure, but I also have no idea how you would make a system that can do that...

Catching Starship is not feasible, if only because it can't be done for Mars. Starship itself - as envisioned - will always need to transition from bellyflop to vertical.

If Elon scraps the current concept and goes to a "Space:1999 Eagle Transporter" style horizontal lander architecture, all bets are off. But it won't be "Starship" as we know it today and is waaaay off-topic for this thread.

If there is a way to catch Starship horizontally (Elon alluded to a kind of hypothetical bouncy castle a few times, although it seems impractical to me), then it would apply to tanker and Earth orbit vehicles only. By saving the mass of landing fuel and landing legs, it would increase the payload capacity of tankers in particular, which would reduce the number of  tanker launchers required to refuel Starships heading to the Moon and Mars.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dfp21 on 04/30/2021 01:24 am
Musk has recently said he wants to catch both the booster and the 2nd stage to enable fast turnaround. Fast, meaning hours, not days.

The catcher would place the 2nd stage on top of a previously-caught booster.

(interview with Peter Diamandis)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 04/30/2021 02:03 am
Honestly, the prospect of tower crashes is another reason why I still think stage-2 catches with the tower are a bad idea. Super Heavy coming in vertically is one thing; a Starship coming in with the flip maneuver could potentially be far less reliable, and would near double the overall amount of catches the tower has to perform regardless; and for every SN8-11 style failure, that's another potential chance that that tower is out of commission for months if not years, depending on damage severity.
I believe the point of catching Starships is that they wouldn't have to do the flip; it would be caught horizontally. I'm pretty sure this would have to be done with some other structure, but I also have no idea how you would make a system that can do that...

Catching Starship is not feasible, if only because it can't be done for Mars. Starship itself - as envisioned - will always need to transition from bellyflop to vertical.

If Elon scraps the current concept and goes to a "Space:1999 Eagle Transporter" style horizontal lander architecture, all bets are off. But it won't be "Starship" as we know it today and is waaaay off-topic for this thread.

there's a thread for no legs starship and has all sorts of creative ideas from a counterweight swinging bouncy castle to tailhooks ala the Navy.   Go read and comment there: 

https://forum.nasaspaceflight.com/index.php?topic=53571.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Semmel on 04/30/2021 01:31 pm
It looks like the section with all the heat tiles that came out of tent 3 will be a base for the next nose.
 The next SN or gse tank or whatever it is has started rising in Midbay.

These heat shild tiles are looking sooo cool! When a Starship is done, its gonna will look like charcoal black dragon skin. Love it!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/30/2021 03:44 pm
PSA for today’s SN15 flight attempt to everyone:

Please please PLEASE check twice what thread you are posting in, and ask yourself if what you are posting is a duplicate to something already in updates, or if it’s discussion.

If it’s discussion, post it up here, and someone will respond (trust me, we have an awesome active community  ;D )

Carry on, and happy tank watching  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StarshipSLS on 04/30/2021 04:33 pm
SpaceX website does not have an update yet. No village evac yet.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StarshipSLS on 04/30/2021 05:19 pm
Still no village evac or SpaceX confirmation. Weather is still bad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jackerson on 04/30/2021 05:37 pm
The consensus for the entire day has been that the weather will improve this afternoon. Repeating that the weather is currently bad is not helpful information.

Still no village evac or SpaceX confirmation. Weather is still bad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jackerson on 04/30/2021 05:43 pm
Is the FAA inspector on site?

The consensus for the entire day has been that the weather will improve this afternoon. Repeating that the weather is currently bad is not helpful information.

Still no village evac or SpaceX confirmation. Weather is still bad.
Weather is not the issue.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 04/30/2021 05:47 pm
Is the FAA inspector on site?

Welcome to NSF but this is not an Update. Please post comments and questions in a discussion thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/30/2021 05:47 pm
Is the FAA inspector on site?
Yes.  Take this to the discussion thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jackerson on 04/30/2021 05:57 pm
If weather wasn't the issue, what do you think was? I was impressed with how they didn't have to replace any Raptors after two static fires.

The consensus for the entire day has been that the weather will improve this afternoon. Repeating that the weather is currently bad is not helpful information.

Still no village evac or SpaceX confirmation. Weather is still bad.
Weather is not the issue.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/30/2021 06:03 pm
Still no village evac or SpaceX confirmation. Weather is still bad.

Stop posting in updates, all you are doing is duplicating and spreading speculation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nescio Erucis on 04/30/2021 06:12 pm
From the SN15 thread:
https://forum.nasaspaceflight.com/index.php?topic=53509.msg2230251#msg2230251
Nomadd says weather was not the reason for the scrub.
Does it have something to do with this?
https://twitter.com/wapodavenport/status/1387828942418161665

ie, that perhaps the FAA hasn't had time to "verify that SpaceX has implemented corrective actions"?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/30/2021 06:30 pm
https://apogeereport.com/spacex-to-put-fins-on-super-heavy-booster-and-bellyflop-it-like-starship/

What the snuh?

Dude. This is a fake troll.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JET777 on 04/30/2021 06:31 pm
The consensus for the entire day has been that the weather will improve this afternoon. Repeating that the weather is currently bad is not helpful information.

Still no village evac or SpaceX confirmation. Weather is still bad.
Weather is not the issue.
it's because of SpaceX Crew-1 Astronauts Depart?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: uncas on 04/30/2021 06:31 pm
https://apogeereport.com/spacex-to-put-fins-on-super-heavy-booster-and-bellyflop-it-like-starship/

What the snuh?

It's a satire site.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bluemars1 on 04/30/2021 06:32 pm
It's a satire site (see About). It's meant to be a joke
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rekt1971 on 04/30/2021 06:36 pm
https://apogeereport.com/spacex-to-put-fins-on-super-heavy-booster-and-bellyflop-it-like-starship/

What the snuh?

It's a satire site.

Wait, so you're telling me that Rmitry Dogozin isn't a plumbing engineer for Starship?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ionmars on 04/30/2021 06:38 pm
April fools day 4/01/21 4/30/21.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 04/30/2021 06:39 pm
The consensus for the entire day has been that the weather will improve this afternoon. Repeating that the weather is currently bad is not helpful information.

Still no village evac or SpaceX confirmation. Weather is still bad.
Weather is not the issue.
it's because of SpaceX Crew-1 Astronauts Depart?

CHECK THE THREAD PLEASE! Getting annoying by now

No, dragon and falcon have nothing to do with Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 04/30/2021 06:41 pm
It's a satire site (see About). It's meant to be a joke

Phew, missed that, thanks.

Sure is a niche nerdy joke.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: joek on 04/30/2021 06:43 pm
https://apogeereport.com/spacex-to-put-fins-on-super-heavy-booster-and-bellyflop-it-like-starship/
What the snuh?
Dude. This is a fake troll.
And not a very good one IMO.  Jeepers, could not they have done a better on the fins?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WormPicker959 on 04/30/2021 07:54 pm
https://apogeereport.com/spacex-to-put-fins-on-super-heavy-booster-and-bellyflop-it-like-starship/
What the snuh?
Dude. This is a fake troll.
And not a very good one IMO.  Jeepers, could not they have done a better on the fins?

The "SpaceX Engineer" quoted in the article is named Rmitri Dogozin, a very niche joke. Missed the opportunity to talk about a trampoline, though...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: kalmes on 04/30/2021 08:16 pm
It's a satire site (see About). It's meant to be a joke

Wow! That is a lot of Photoshop jokes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Everything Space on 04/30/2021 10:06 pm
Mary has received a notice for 5AM to 7PM tomorrow. This looks like the same wording of the notice that was given out yesterday.

https://twitter.com/BocaChicaGal/status/1388247634687713286

Quote
I have received an Alert notice for tomorrow Saturday , May 1 from 5 a.m. - 7 p.m. There is no road and beach closure scheduled at this time. I do not know why I have received this notice. #WenHop :fire::rocket::fire:
@NASASpaceflight

What do you think this was for? Could it be for test flight?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 04/30/2021 10:22 pm
Mary has received a notice for 5AM to 7PM tomorrow. This looks like the same wording of the notice that was given out yesterday.

Quote
I have received an Alert notice for tomorrow Saturday , May 1 from 5 a.m. - 7 p.m. There is no road and beach closure scheduled at this time. I do not know why I have received this notice. #WenHop :fire::rocket::fire:
@NASASpaceflight

What do you think this was for? Could it be for test flight?

Unless they want to do another static fire (which doesn't normally happen on weekends either), I don't see what else it could be for?

I wonder if they feel it's worth using up one of their weekend closures at this point to avoid any scheduling problems with the FAA inspector.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 04/30/2021 11:18 pm
If weather wasn't the issue, is it known why today's attempt didn't happen?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 05/01/2021 03:24 am
https://twitter.com/nickyx15a/status/1388144924143628290

Quote
Spotted a new Raptor engine getting delivered ahead of SN15's flight today with @austinbarnard45 . Did not catch a number, but it is marked "INSERT MEME HERE". The guy running this joke must be short on ideas today 😅
📸 -Myself for @SpaceflightIns

Edit to add:

https://twitter.com/austinbarnard45/status/1388147548205027329

No it's because Raptors are the first rocket engine to run on MemeLOX
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/01/2021 08:33 am

About 3 month ago landing legs for sn16 were spotted, but IIUC after sn10 flight they were scrapped. What kind of legs has sn16?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/01/2021 10:08 am
https://twitter.com/bocacharts/status/1388428529268928515

Quote
All Major Testing - Saturday 1 May 2021
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DistantTemple on 05/01/2021 11:43 am
https://twitter.com/nickyx15a/status/1388144924143628290

Quote
Spotted a new Raptor engine getting delivered ahead of SN15's flight today with @austinbarnard45 . Did not catch a number, but it is marked "INSERT MEME HERE". The guy running this joke must be short on ideas today 😅
📸 -Myself for @SpaceflightIns
.... snip (DT showing pic once only)

No it's because Raptors are the first rocket engine to run on MemeLOX

Beware: "don't give that any oxygen"... seriously? ..... of course that's the CH4 inlet!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tyrred on 05/01/2021 11:50 am

About 3 month ago landing legs for sn16 were spotted, but IIUC after sn10 flight they were scrapped. What kind of legs has sn16?

Still no sign of new leg design AFAIK.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/01/2021 12:21 pm
Though Micahel Baylor is saying he understands that the flight target is now NET Monday:

https://twitter.com/nextspaceflight/status/1388289462287753216

Michael has very good sources and is undoubtedly correct. The TFR’s were requested and processed by the FAA via their own processes, but the County still gets to decide if closing access to the beach and state park is allowable, and they really don’t like doing that on weekends.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Levy on 05/01/2021 06:30 pm
It was SN17's aft skirt that was scrapped not SN16's but yes as said before still no sign of a new design yet
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 05/01/2021 08:04 pm
Are they skipping SN18 & SN19?  ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 05/01/2021 08:30 pm
Are they skipping SN18 & SN19?  ???

All signs point to yes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WormPicker959 on 05/01/2021 09:16 pm
This recent photo (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2230946#msg2230946) of the tower from bacachicagal shows an increased number of crossbeams (not sure if that's the right term) on the upper level of the tower. The levels below this do not have such reinforcement. I believe this indicates there will be a floor at this level, what say you engineers?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/01/2021 10:13 pm
This recent photo (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2230946#msg2230946) of the tower from bacachicagal shows an increased number of crossbeams (not sure if that's the right term) on the upper level of the tower. The levels below this do not have such reinforcement. I believe this indicates there will be a floor at this level, what say you engineers?

Yup.  It's for a floor.  The term is Joist (https://en.wikipedia.org/wiki/Joist).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/02/2021 06:08 pm
FAA latest advisory confirms that the Starship launch is scheduled between 7AM-8PM local time tomorrow. (thanks for corrections)

https://www.fly.faa.gov/adv/adv_otherdis.jsp?advn=17&adv_date=05022021&facId=DCC&title=OPERATIONS+PLAN&titleDate=05/02/21

There are the the TFRs for Monday, but no road closure. Wath is going on?  Has something like this ever happened? Were there  signs of less accomodant policy by the county?

Nothing is "going on".  The county is outstanding.  No need to leap to FUD (Fear, Uncertainty, Doubt).  The road closures will come.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WormPicker959 on 05/02/2021 08:12 pm
This recent photo (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2230946#msg2230946) of the tower from bacachicagal shows an increased number of crossbeams (not sure if that's the right term) on the upper level of the tower. The levels below this do not have such reinforcement. I believe this indicates there will be a floor at this level, what say you engineers?

Yup.  It's for a floor.  The term is Joist (https://en.wikipedia.org/wiki/Joist).

Thanks for the correction!

Based on absolutely nothing, I think there will be a floor at each "top" of each "section" (again, forgive my lack of correct terminology), like the 11 floors of 39A. But I have no idea! I don't even know what the floors are even for at 39A. What do you all think?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 05/02/2021 08:37 pm
They will need a floor/base for connecting the different upper sections, if they don't want to use a 100 m high manlift
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 05/02/2021 11:11 pm
The tower-related talks are not part of Prototype discussion.

Here is a more suitable thread for the same

SpaceX Texas launch site Discussion and Updates - Thread 10
https://forum.nasaspaceflight.com/index.php?topic=49086.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/03/2021 08:25 am
Hi. I'm new here

What a great work you do and what a great community this is. I have been reading this forum these last months and  now I decide to create an account.

Let's see if they schedule road clousures for upcoming days. Seems there will be nice weather both tuesday and wednesday
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 05/03/2021 08:32 am
Hi. I'm new here

What a great work you do and what a great community this is. I have been reading this forum these last months and  now I decide to create an account.

Let's see if they schedule road clousures for upcoming days. Seems there will be nice weather both tuesday and wednesday
Welcome to the forums.  Jump in and join the discussions, but please remember that threads with names ending in "updates" are for posting information only, not for discussion about those updates.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/03/2021 08:37 am
Hi. I'm new here

What a great work you do and what a great community this is. I have been reading this forum these last months and  now I decide to create an account.

Let's see if they schedule road clousures for upcoming days. Seems there will be nice weather both tuesday and wednesday
Welcome to the forums.  Jump in and join the discussions, but please remember that threads with names ending in "updates" are for posting information only, not for discussion about those updates.

Ups, sorry, true.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 05/03/2021 11:59 am
The tower-related talks are not part of Prototype discussion.

Here is a more suitable thread for the same

SpaceX Texas launch site Discussion and Updates - Thread 10
https://forum.nasaspaceflight.com/index.php?topic=49086.0

Sorry, thx for new adress!

How high will SN 15 fly?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/03/2021 12:19 pm
The tower-related talks are not part of Prototype discussion.

Here is a more suitable thread for the same

SpaceX Texas launch site Discussion and Updates - Thread 10
https://forum.nasaspaceflight.com/index.php?topic=49086.0

Sorry, thx for new adress!

How high will SN 15 fly?
10 km as usual
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/03/2021 12:40 pm
Yeah plan seems to be 10 km until they can stick the landing. 

Then expand the envelope. 

It seems like a big jump to go from SN15 to orbital with SN20. 

But it’s also a very Elon test idea.  Test as much as possible as soon as possible.

Maybe it takes 10 SN’s to orbit to get things to work. And if it does the booster operations would be pretty smooth by then.

Also, I can see BN2 being a testing work horse that helps develop the tower catching plan.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Surgeon on 05/03/2021 01:01 pm
Yeah plan seems to be 10 km until they can stick the landing. 

Then expand the envelope. 

It seems like a big jump to go from SN15 to orbital with SN20. 

But it’s also a very Elon test idea.  Test as much as possible as soon as possible.

Maybe it takes 10 SN’s to orbit to get things to work. And if it does the booster operations would be pretty smooth by then.

Also, I can see BN2 being a testing work horse that helps develop the tower catching plan.

Very true.

The next big milestone (after they nail the landing) would be maintaining control from supersonic, through trans-sonic, down to sub-sonic flight.

You can definitely do that coming back from orbit :D
...although if you really wanted that to be the first time or not.... that's another question
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tssp_art on 05/03/2021 02:35 pm
The next big milestone (after they nail the landing) would be maintaining control from supersonic, through trans-sonic, down to sub-sonic flight.

That is a big milestone but there are two important ones that come before it. First, going from launch, through transonic and supersonic (surviving Max-Q) and second, surviving the dynamic heating of re-entry. That last one is going to be especially challenging I think.

Quote
You can definitely do that coming back from orbit :D
...although if you really wanted that to be the first time or not.... that's another question

My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/03/2021 02:41 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jak Kennedy on 05/03/2021 02:50 pm
So the flight is now planned for tomorrow. May the Forth be with you SN15

Sorry, couldn't resist 😁

Edit: slight spelling correction
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tssp_art on 05/03/2021 02:56 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/03/2021 03:09 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Or SN15 with a second flight. 

If they can land an SN, they can refly it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: volker2020 on 05/03/2021 04:25 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Or SN15 with a second flight. 

If they can land an SN, they can refly it.

I wonder. I see a lot of BN-3 parts but only one BN-2 part. Are they skipping BN-2 directly going for BN-3?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/03/2021 04:31 pm
FAA latest advisory confirms that the Starship launch is scheduled between 7AM-8PM local time tomorrow. (thanks for corrections)

https://www.fly.faa.gov/adv/adv_otherdis.jsp?advn=17&adv_date=05022021&facId=DCC&title=OPERATIONS+PLAN&titleDate=05/02/21

There are the the TFRs for Monday, but no road closure. Wath is going on?  Has something like this ever happened? Were there  signs of less accomodant policy by the county?

Nothing is "going on".  The county is outstanding.  No need to leap to FUD (Fear, Uncertainty, Doubt).  The road closures will come.
Sorry.
I removed the post.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/03/2021 04:40 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Or SN15 with a second flight. 

If they can land an SN, they can refly it.

I wonder. I see a lot of BN-3 parts but only one BN-2 part. Are they skipping BN-2 directly going for BN-3?

Nope. BN2 parts exist.

It looks like BN2 might be a test tank, and the label spotted for BN2.1 could be the full scale booster.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/03/2021 04:57 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

I don't think so, because sn16 is nearly ready, so in tha case of a succesful flight IMO they will inspect it down to the millimeter, and at the same time test (cryo prof, static fire) sn16.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Or SN15 with a second flight. 

If they can land an SN, they can refly it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 05/03/2021 09:12 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

I don't think so, because sn16 is nearly ready, so in tha case of a succesful flight IMO they will inspect it down to the millimeter, and at the same time test (cryo prof, static fire) sn16.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Or SN15 with a second flight. 

If they can land an SN, they can refly it.

Seems a bit iffy to go through max-Q with all that exposed cabling.  Has anyone seen any conduit/covers/cable runs for the top (leeward) side of Starship in the photos?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 05/03/2021 09:14 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Felix went supersonic jumping from about 38km, so I suspect a way of testing Starship before a full re-entry is to go up to about 40km while hitting max-Q, and then falling down and hitting supersonic while flat (or 70 degrees) to the earth.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/03/2021 09:36 pm
Let's see if SN15 manages to land properly first. I think now for SpaceX it has to be important to see the consecuences of the flight and landing in terns of possible structural damage or whatever. It will be nice information for further tests and development
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/03/2021 10:12 pm
Let's see if SN15 manages to land properly first. I think now for SpaceX it has to be important to see the consecuences of the flight and landing in terns of possible structural damage or whatever. It will be nice information for further tests and development

If they land, there will still be ways to improve the landing. 

Maybe fly the same flight with tweaked parameters at the very end.  Or even identical to see if it is repeatable.

If the hardware is built, checked out and paid for why not.  Just pick it up, roll it up to the suborbital pad, static fire and repeat.  So like 7-10 day cycle time, no problem!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 05/03/2021 11:16 pm
My guess is they will try a supersonic high altitude "hop" before they go orbital using SN16 or SN17.

Orbital is with BN3/SN20

https://www.nasaspaceflight.com/2021/03/starship-sn11-spacex-orbital-flight-summer/

Poor wording on my part - My guess is they will try a supersonic high altitude "hop" using SN16 or SN17 before they go orbital (with SN20).

Felix went supersonic jumping from about 38km, so I suspect a way of testing Starship before a full re-entry is to go up to about 40km while hitting max-Q, and then falling down and hitting supersonic while flat (or 70 degrees) to the earth.

Of course the area and mass are quite different, so not sure how comparable a suited person is in terms of terminal velocity versus a Starship that's low on fuel.

Also I was surprised to read recently that Felix's record has been superceded by a Google VP - jumped from higher than Felix.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/04/2021 12:16 am
I could not be more excited about the Orbital launch mount, tower and infrastructure.

Building all this GSE is the biggest step needed to orbital flights of the largest rocket ever built and the first fully reusable 2 stage vehicle.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/04/2021 12:21 am
I could not be more excited about the Orbital launch mount, tower and infrastructure.

Building all this GSE is the biggest step needed to orbital flights of the largest rocket ever built and the first fully reusable 2 stage vehicle.

And that's great that you're excited. So take a deep breath, calm your mind, and find the right forum and thread. ;)

https://forum.nasaspaceflight.com/index.php?topic=49086.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/04/2021 01:46 am
From Mary's pictures today we have a new thrust puck design, well a variation at least...

Two features of note;
1) the downcomer is longer and appears to have the bellows integrated (suggested by the wrapped up section).
2) there's a horizontal pipe running through the inverted cone from potentially the external methane distribution manifold.

Thoughts on the horizontal pipe?
It looks a bit small to be the feed for the VacRaptors if there's only one...
Why branch from outside the tank and feed back in? Would that be to keep some sort of valve outside the LOX?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bfabry on 05/04/2021 01:57 am
From Mary's pictures today we have a new thrust puck design, well a variation at least...

Two features of note;
1) the downcomer is longer and appears to have the bellows integrated (suggested by the wrapped up section).
2) there's a horizontal pipe running through the inverted cone from potentially the external methane distribution manifold.

Thoughts on the horizontal pipe?
It looks a bit small to be the feed for the VacRaptors if there's only one...
Why branch from outside the tank and feed back in? Would that be to keep some sort of valve outside the LOX?

I think that horizontal pipe existed for SN12, it was just much shorter in the horizontal direction. What speculation I can find on it is guessing that it's the CH4 fuel fill line? https://twitter.com/fael097/status/1324479821997608960/photo/1
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jwrjr on 05/04/2021 02:22 am
Anyone know where the SN15 launch can be viewed online other than Youtube?  I'll be at work and for some reason the Air Force has blocked Youtube (including Youtube streams embedded in other pages).  Thanks!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: haywoodfloyd on 05/04/2021 02:36 am
Anyone know where the SN15 launch can be viewed online other than Youtube?  I'll be at work and for some reason the Air Force has blocked Youtube (including Youtube streams embedded in other pages).  Thanks!

Try the SpaceX website. They usually start the video a few minutes before launch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 05/04/2021 02:49 am
Try the SpaceX website. They usually start the video a few minutes before launch.
I think the SpaceX website usually uses an embedded youtube video so that may not work either.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CruddyCuber on 05/04/2021 03:12 am
Anyone know where the SN15 launch can be viewed online other than Youtube?  I'll be at work and for some reason the Air Force has blocked Youtube (including Youtube streams embedded in other pages).  Thanks!

Could you watch it on your phone using cellular data?  That's what I've been doing because my highschool's devices block YouTube as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JaimeZX on 05/04/2021 03:38 am
This. If launches happen while I'm at work anymore, I go to my phone. The FH test launch was one of the last I watched in the office.  But this is getting quite off-topic. ;) 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 05/04/2021 04:04 am
Anyone know where the SN15 launch can be viewed online other than Youtube?  I'll be at work and for some reason the Air Force has blocked Youtube (including Youtube streams embedded in other pages).  Thanks!

Because YouTube eats up 90% of AF bandwidth otherwise and the taxpayers pay a premium for it (besides all the lost airman productivity on gamer videos). Rumble is probably blocked too.
Two options: 1. Don’t watch it at work, unless you’re on your cellphone at the food court.
2. Convince the commanding officer it’s good for morale and get GO approval for a temp exception. Good luck.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 05/04/2021 09:59 am
Anyone know where the SN15 launch can be viewed online other than Youtube?  I'll be at work and for some reason the Air Force has blocked Youtube (including Youtube streams embedded in other pages).  Thanks!

Pretty sure SpaceX also streams SS tests on Twitter, and people also restream/watch them on Twitch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rakaydos on 05/04/2021 10:24 am
From Mary's pictures today we have a new thrust puck design, well a variation at least...

Two features of note;
1) the downcomer is longer and appears to have the bellows integrated (suggested by the wrapped up section).
2) there's a horizontal pipe running through the inverted cone from potentially the external methane distribution manifold.

Thoughts on the horizontal pipe?
It looks a bit small to be the feed for the VacRaptors if there's only one...
Why branch from outside the tank and feed back in? Would that be to keep some sort of valve outside the LOX?
Based on bfabry's post, I would speculate that that's the refueling pipe for whichever propellant it's hooked up to.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/04/2021 12:43 pm
Anyone know where the SN15 launch can be viewed online other than Youtube?  I'll be at work and for some reason the Air Force has blocked Youtube (including Youtube streams embedded in other pages).  Thanks!

I also work at a gov't site, without cell phone access, and have no luck watching the typical streams.  However, I can go through my corporate VPN, which opens a virtual desktop, and access Youtube from there.  It's heavily pixelated, to the point of being all but unwatchable, but I can watch the outline of success/failure.  Rewatch at home...  It's okay for background viewing because most of work is on separate networks.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CrazySpace on 05/04/2021 01:40 pm
If today is a falcon 9 launch, do you think that SN15 will be launched? I think that not, and you??
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 05/04/2021 01:43 pm
teslarati.com thinks: "no way"
But why not?
Aren't this two flights two total different things for SX?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mandrewa on 05/04/2021 01:51 pm
From Mary's pictures today we have a new thrust puck design, well a variation at least...

Two features of note;
1) the downcomer is longer and appears to have the bellows integrated (suggested by the wrapped up section).
2) there's a horizontal pipe running through the inverted cone from potentially the external methane distribution manifold.

Thoughts on the horizontal pipe?
It looks a bit small to be the feed for the VacRaptors if there's only one...
Why branch from outside the tank and feed back in? Would that be to keep some sort of valve outside the LOX?

I think that horizontal pipe existed for SN12, it was just much shorter in the horizontal direction. What speculation I can find on it is guessing that it's the CH4 fuel fill line? https://twitter.com/fael097/status/1324479821997608960/photo/1

See https://forum.nasaspaceflight.com/index.php?topic=52205.msg2150689#msg2150689
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 05/04/2021 02:17 pm
They are getting ready to flip BN3 thrust section


Edit - N not H!!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 05/04/2021 02:39 pm
They are getting ready to flip BH3 thrust section
Is BH3 new nomenclature for BN3/the third Superheavy prototype structure?  Or is it something else?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 05/04/2021 03:33 pm
They are getting ready to flip BH3 thrust section
Is BH3 new nomenclature for BN3/the third Superheavy prototype structure?  Or is it something else?
More likely due to the proximity of the N and H keys on a QWERTY keyboard
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/04/2021 03:40 pm
Scrubbed out of nowhere, curious what happened today to cause it  :o
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/04/2021 03:46 pm
Scrubbed out of nowhere, curious what happened today to cause it  :o

Yes, very curiouse, because there was no tank farm activity, nor anything seemd happening. Could the cause be the weather, not bad but still cloudy (even if there are many hours left in the window )?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/04/2021 03:54 pm
Scrubbed out of nowhere, curious what happened today to cause it  :o

Yes, very curiouse, because there was no tank farm activity, nor anything seemd happening. Could the cause be the weather, not bad but still cloudy (even if there are many hours left in the window )?

Weather looked perfect today. Only thing I could think of is either something came up in final checkouts, or the Starlink launch set for later is an interference.

Looking ahead to weather, its suppose to be cloudy and rainy essentially all day tomorrow and Thursday. Next best day to attempt would be Friday IMO.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/04/2021 03:56 pm
Don't know if this is helpful or not, but since it apparently comes from Nextspaceflight it may have some credibility:

https://twitter.com/ChrisCrosss98/status/1389608376984694792
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/04/2021 04:02 pm
Scrubbed out of nowhere, curious what happened today to cause it  :o

Yes, very curiouse, because there was no tank farm activity, nor anything seemd happening. Could the cause be the weather, not bad but still cloudy (even if there are many hours left in the window )?

Weather looked perfect today. Only thing I could think of is either something came up in final checkouts, or the Starlink launch set for later is an interference.

Looking ahead to weather, its suppose to be cloudy and rainy essentially all day tomorrow and Thursday. Next best day to attempt would be Friday IMO.

Yes, friday seems to be the best day aparently.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/04/2021 04:20 pm
Don't know if this is helpful or not, but since it apparently comes from Nextspaceflight it may have some credibility:

https://twitter.com/ChrisCrosss98/status/1389608376984694792

Maria pointer just tweeted that this is what she was told. ULW’s strike again.....
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/04/2021 04:24 pm
Don't know if this is helpful or not, but since it apparently comes from Nextspaceflight it may have some credibility:

https://twitter.com/ChrisCrosss98/status/1389608376984694792

Maria pointer just tweeted that this is what she was told. ULW’s strike again.....

Are ULW a problem only for this low altitude/particular flight profile or for all launches? Could be that this particular flight profile, with a long high altitude hover is very sensitive to ULW, unlike the straight up axcent on an orbital flight?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/04/2021 04:33 pm
Don't know if this is helpful or not, but since it apparently comes from Nextspaceflight it may have some credibility:

https://twitter.com/ChrisCrosss98/status/1389608376984694792

Maria pointer just tweeted that this is what she was told. ULW’s strike again.....

Are ULW a problem only for this low altitude/particular flight profile or for all launches? Could be that this particular flight profile, with a long high altitude hover is very sensitive to ULW, unlike the straight up axcent on an orbital flight?

Very likely yes. Since in the current flight profile the vehicle ascends slowly, it’s really prone to winds. All it would take is really a big gust to end its life.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/04/2021 05:12 pm
Don't know if this is helpful or not, but since it apparently comes from Nextspaceflight it may have some credibility:

https://twitter.com/ChrisCrosss98/status/1389608376984694792

Maria pointer just tweeted that this is what she was told. ULW’s strike again.....

Are ULW a problem only for this low altitude/particular flight profile or for all launches? Could be that this particular flight profile, with a long high altitude hover is very sensitive to ULW, unlike the straight up axcent on an orbital flight?

Very likely yes. Since in the current flight profile the vehicle ascends slowly, it’s really prone to winds. All it would take is really a big gust to end its life.

Not due to structural concerns. Starship is fairly short and stout for its diameter (unlike, say, Falcon 9). Upper level winds are a problem for trajectory shaping and debris-field modeling in case of failure or FTS detonation, and - especially for long, slender rockets like F9 - susceptibility to wind shear. Sudden changes of magnitude and/or direction as the vehicle ascends through layers of air moving differently from one another.

I think that Starship, having a fairly low fineness ratio, is much less subject to structural concerns due to wind shear, especially in light of its slow ascent, but much more susceptible to being nudged out of its planned flight corridor for both ascent and return.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 05/04/2021 05:36 pm
They are getting ready to flip BH3 thrust section
Is BH3 new nomenclature for BN3/the third Superheavy prototype structure?  Or is it something else?
More likely due to the proximity of the N and H keys on a QWERTY keyboard


Correct :(
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: libra on 05/04/2021 05:45 pm
They are getting ready to flip BH3 thrust section
Is BH3 new nomenclature for BN3/the third Superheavy prototype structure?  Or is it something else?
More likely due to the proximity of the N and H keys on a QWERTY keyboard


Correct :(

COVFEFE
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Sohl on 05/04/2021 06:18 pm
I think that Starship, having a fairly low fineness ratio, is much less subject to structural concerns due to wind shear, especially in light of its slow ascent, but much more susceptible to being nudged out of its planned flight corridor for both ascent and return.

This makes a lot of sense to me.  They would not want to keep a lot of surplus fuel to actively overcome a large deviation due to wind.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/04/2021 06:44 pm
From Mary's pictures today we have a new thrust puck design, well a variation at least...

Two features of note;
1) the downcomer is longer and appears to have the bellows integrated (suggested by the wrapped up section).
2) there's a horizontal pipe running through the inverted cone from potentially the external methane distribution manifold.

Thoughts on the horizontal pipe?
It looks a bit small to be the feed for the VacRaptors if there's only one...
Why branch from outside the tank and feed back in? Would that be to keep some sort of valve outside the LOX?

I think that horizontal pipe existed for SN12, it was just much shorter in the horizontal direction. What speculation I can find on it is guessing that it's the CH4 fuel fill line? https://twitter.com/fael097/status/1324479821997608960/photo/1 (https://twitter.com/fael097/status/1324479821997608960/photo/1)
IIRC, there is a feed line from the LOX header that runs the length of the ship INSIDE the tanks. Maybe it hooks up to this pipe?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wolfi44 on 05/04/2021 08:16 pm
https://twitter.com/spacex360/status/1389643570009841669

Quote
SpaceX are now targeting tomorrow (Wednesday) for SN15’s flight per FAA advisory!

Launch Window 1200-0100Z - is this UTC or Boca Chica local time ?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/04/2021 08:24 pm
https://twitter.com/spacex360/status/1389643570009841669

Quote
SpaceX are now targeting tomorrow (Wednesday) for SN15’s flight per FAA advisory!

Launch Window 1200-0100Z - is this UTC or Boca Chica local time ?

The Z after the times indicates Zulu or UTC.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 05/04/2021 08:38 pm
I'm not getting into the source, but SpaceX is telling their own people they scrubbed for winds today.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: haywoodfloyd on 05/04/2021 08:43 pm
Weather for Wednesday and Thursday showing rain both days.
Friday looks good.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: khorton on 05/04/2021 10:24 pm
Tomorrow's altitude wind forecast seems better than today's.
Checking the soundings for Brownsville, at this moment there are winds of around 50knots. However, for tomorrow is expected to be between 30 and 35knots, which sounds well, or at least, better than 50.
For thursday it's quite the same, and for friday there are no soundings forecasts yet.

The bad aspect for tomorrow is the rain and visibility, but seems it will be light rain and even no rain towards the end of the window. Maybe we don´t have to wait until friday
50 kt is quite a normal wind speed for 10 km height in my experience as a pilot flying at these altitudes many times, so I'd be surprised if it was outside their upper wind limits.  Maybe they had reason to believe that the actual wind at altitude at Boca Chica would be higher than that, or maybe there was some other reason for the scrub.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 05/05/2021 12:03 am
Tomorrow's altitude wind forecast seems better than today's.
Checking the soundings for Brownsville, at this moment there are winds of around 50knots. However, for tomorrow is expected to be between 30 and 35knots, which sounds well, or at least, better than 50.
For thursday it's quite the same, and for friday there are no soundings forecasts yet.

The bad aspect for tomorrow is the rain and visibility, but seems it will be light rain and even no rain towards the end of the window. Maybe we don´t have to wait until friday
50 kt is quite a normal wind speed for 10 km height in my experience as a pilot flying at these altitudes many times, so I'd be surprised if it was outside their upper wind limits.  Maybe they had reason to believe that the actual wind at altitude at Boca Chica would be higher than that, or maybe there was some other reason for the scrub.

SpaceX installed a bunch of weather radar, IIRC near the satellite dishes, which would give them a better picture of local conditions.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: daavery on 05/05/2021 12:52 am
weather system is over in the oil farm area S of the new air reduction plant - it's a radar winds aloft 0 - 10KM system
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/05/2021 12:29 pm
The weather seems to be cloudy but not terrible weather. Most probability of rain is now and it supose the weather to be better within the next hours. Less wind too.

Let's see what happens  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/05/2021 12:31 pm
https://twitter.com/spacex360/status/1389915279522738180?

https://twitter.com/nextspaceflight/status/1389795979516256258?

Dude. Stop posting something that’s already been posted. Updates exist to inform people of things to know, not to make people aware of who you are.

A tweet you posted is literally your own tweet 🤦‍♂️
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 05/05/2021 03:51 pm
Why are they building Integration Tower sections at the Propellent Production site? Wouldn't it be easier to build them at the tower, like they did with the High Bay? ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wheedude on 05/05/2021 03:57 pm
Why are they building Integration Tower sections at the Propellent Production site? Wouldn't it be easier to build them at the tower, like they did with the High Bay? ???

My guess is this is more efficient.  If the pad must close out every so often for tests, that's time lost on the tower build.  At the same time, between the other work going on- rebuilding the landing pad after crashes, building the other parts of the facility (sheds, bunker, orbital launch mount)- they probably are forced to jockey for space to work.  If they can build the tower in sections elsewhere, they only need enough time on-site to stack and secure. 
I see this on the campus where I work- we have new buildings going up constantly... instead of building from the ground up on site, they actually bring in huge prefab sections of steel and concrete wall, using a single crane on site to put them together like giant Legos.  It really saves time.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Burningdan87 on 05/05/2021 04:03 pm
It's also safer and easier. Less time spend at height bolting things together with beams swinging in the breeze.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/05/2021 04:04 pm
Why are they building Integration Tower sections at the Propellent Production site? Wouldn't it be easier to build them at the tower, like they did with the High Bay? ???

My guess is this is more efficient.  If the pad must close out every so often for tests, that's time lost on the tower build.  At the same time, between the other work going on- rebuilding the landing pad after crashes, building the other parts of the facility (sheds, bunker, orbital launch mount)- they probably are forced to jockey for space to work.  If they can build the tower in sections elsewhere, they only need enough time on-site to stack and secure. 
I see this on the campus where I work- we have new buildings going up constantly... instead of building from the ground up on site, they actually bring in huge prefab sections of steel and concrete wall, using a single crane on site to put them together like giant Legos.  It really saves time.

Plus, it means you don't have people working at enormous heights.  Plus, your crane doesn't need to be absolutely massive and dangling a huge chunk of steel at huge heights where it's harder to control for anywhere near as long.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/05/2021 04:44 pm
Why are they building Integration Tower sections at the Propellent Production site? Wouldn't it be easier to build them at the tower, like they did with the High Bay? ???

My guess is this is more efficient.  If the pad must close out every so often for tests, that's time lost on the tower build.  At the same time, between the other work going on- rebuilding the landing pad after crashes, building the other parts of the facility (sheds, bunker, orbital launch mount)- they probably are forced to jockey for space to work.  If they can build the tower in sections elsewhere, they only need enough time on-site to stack and secure. 
I see this on the campus where I work- we have new buildings going up constantly... instead of building from the ground up on site, they actually bring in huge prefab sections of steel and concrete wall, using a single crane on site to put them together like giant Legos.  It really saves time.

So they don't clear the manufacturing site during testing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 05/05/2021 04:48 pm
Why are they building Integration Tower sections at the Propellent Production site? Wouldn't it be easier to build them at the tower, like they did with the High Bay? ???

My guess is this is more efficient.  If the pad must close out every so often for tests, that's time lost on the tower build.  At the same time, between the other work going on- rebuilding the landing pad after crashes, building the other parts of the facility (sheds, bunker, orbital launch mount)- they probably are forced to jockey for space to work.  If they can build the tower in sections elsewhere, they only need enough time on-site to stack and secure. 
I see this on the campus where I work- we have new buildings going up constantly... instead of building from the ground up on site, they actually bring in huge prefab sections of steel and concrete wall, using a single crane on site to put them together like giant Legos.  It really saves time.

So they don't clear the manufacturing site during testing?

I believe the gas well site (where the tower sections are being assembled) is just outside of the evacuation zone.   The main production area is cleared when they do flights but not for static fires.  The launch site has to be cleared whenever there is a flight, static fire, or any pressurized operations on the vehicles.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 05/05/2021 05:11 pm
Why are they building Integration Tower sections at the Propellent Production site? Wouldn't it be easier to build them at the tower, like they did with the High Bay? ???


You can find the answer to your question on Launch Site Thread where this has already been discussed.

SpaceX Texas launch site Discussion and Updates - Thread 10
https://forum.nasaspaceflight.com/index.php?topic=49086.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/05/2021 06:48 pm
Why is every event worthy of an "!" ?

Not an update  ;D  ;)

Much excite is the reason  :D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: pb2000 on 05/05/2021 06:49 pm
Why is every event worthy of an "!" ?
Tisk Tisk, posting discussion in the updates only thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 05/05/2021 06:49 pm
Why is every event worthy of an "!" ?

Not an update  ;D ;)

Much excite is the reason  :D


May the 5ith!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/05/2021 06:50 pm
It's a pity to see almost all Texas clear on the weather satellite and only cloudy in this tiny part

Let's see if the clouds move or they stay stuck
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rekt1971 on 05/05/2021 06:52 pm
Here we go again, please don't post in the UPDATE thread or you will summon Herb.



And he won't be happy... (neither am I)  :(
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/05/2021 06:53 pm
Here we go again, please don't post in the UPDATE thread or you will summon Herb.



And he won't be happy... (neither am I)  :(

Sorry, rookie mistake with my reply...  But I already understand your warning!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 05/05/2021 06:56 pm
Why is every event worthy of an "!" ?

Not an update  ;D ;)

Much excite is the reason  :D


May the 5ith!
The Cinco de Mayo launch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ELinder on 05/05/2021 07:03 pm
Is there a link to the SpaceX stream for todays  attempt?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rekt1971 on 05/05/2021 07:04 pm
Is there a link to the SpaceX stream for todays  attempt?

Not yet, they will post it about 5 minutes before launch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 05/05/2021 07:05 pm
Why is every event worthy of an "!" ?

Not an update  ;D ;)

Much excite is the reason  :D


May the 5ith!
The Cinco de Mayo launch.

Isn't cinco de mayo celebrated with fireworks? Elon is going to light the biggest rocket ever so close to the mexican border. Let's hope this one comes down in one piece and stays that way.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 05/05/2021 07:05 pm
not posted yet. It will appear here https://www.spacex.com/vehicles/starship/, usually about ~15 min before the scheduled time. Start checking at 2:40 pm CDT today.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Pete on 05/05/2021 07:07 pm
May the 5ith!

GAck, I'm slow sometimes.

I only now realized that " may the 4th be with you" is directly followed by the "5ith"



Yeah, this has nothing to do with SpaceX, mods may nuke it as they wish
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ELinder on 05/05/2021 07:10 pm
Is there a link to the SpaceX stream for todays  attempt?

Not yet, they will post it about 5 minutes before launch.

I hope so, the don't even have the usual preflight blurb on the Starship page they usually do the day of an attempt.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/05/2021 07:46 pm
Pad Clear!!!!!!!!!!!!!!!!!!!!!!!!!

Come on, guys. No need to troll a guy who’s contributed more knowledge and real-world actual hands-on experience with rockets and the space industry than most of the rest of us combined. :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: daveglo on 05/05/2021 08:48 pm
Pad Clear!!!!!!!!!!!!!!!!!!!!!!!!!

Come on, guys. No need to troll a guy who’s contributed more knowledge and real-world actual hands-on experience with rockets and the space industry than most of the rest of us combined. :)

Spot ON, Herb.  Miss the days of Steven P, about half the time the commentary was something smooth like "Launch."  ;)

Pro. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/05/2021 08:51 pm
So … back to the rocket ..,

Anyone paying closer attention to the streams than me able to figure out what the team who returned to the pad were actually doing? I don’t see any lifts up on the vehicle but I’m also mostly working. I do see them all leaving now.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 05/05/2021 09:15 pm
Pad Clear!!!!!!!!!!!!!!!!!!!!!!!!!

Come on, guys. No need to troll a guy who’s contributed more knowledge and real-world actual hands-on experience with rockets and the space industry than most of the rest of us combined. :)
I interpreted his comment as poking fun at our enthusiasm and was just responding in-kind. Meant no disrespect. Sorry if it came across that way.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 05/05/2021 09:18 pm
So … back to the rocket ..,

Anyone paying closer attention to the streams than me able to figure out what the team who returned to the pad were actually doing? I don’t see any lifts up on the vehicle but I’m also mostly working. I do see them all leaving now.

Loose Spots.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thechungster on 05/05/2021 10:49 pm
It seemed like they did the flip and landing on only engines 1 and 2! Definitely didn't expect the flip to use two engines (especially those two unlike on SN8 which used engines 2 and 3)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GetCrispy on 05/05/2021 10:51 pm
It seemed like they did the flip and landing on only engines 1 and 2! Definitely didn't expect the flip to use two engines (especially those two unlike on SN8 which used engines 2 and 3)

Insprucker said they would light three, but it was unclear to me whether the E3 lot and then shut down before the video came back, or didn’t light at all.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Fmedici on 05/05/2021 10:52 pm
How how likely is it that SN15 will fly again? Will they just switch to SN16 and scrap SN15?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: punder on 05/05/2021 10:53 pm
WOO HOO! Congrats SpaceX!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thechungster on 05/05/2021 10:54 pm
It seemed like they did the flip and landing on only engines 1 and 2! Definitely didn't expect the flip to use two engines (especially those two unlike on SN8 which used engines 2 and 3)

Insprucker said they would light three, but it was unclear to me whether the E3 lot and then shut down before the video came back, or didn’t light at all.

I think at +5:45 you can see a bit of the tank farm in the feed before they cut to the wide shot. Usually engine 3 was the first to relight so we should've seen something if that was the case.

Yeah and Insprucker also said they'd attempt to land on one engine, but perhaps he was just following the SN10/SN11 script.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/05/2021 10:55 pm
Awesome!  8) But SN11 landed *VERY* close to the edge of the pad... (eek)

But eventually it will they will land much more precisely, like latest Starlink mission.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/05/2021 10:55 pm
How how likely is it that SN15 will fly again? Will they just switch to SN16 and scrap SN15?

I really hope they DON'T scrap SN15!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Halidon on 05/05/2021 10:58 pm
Beyond the obvious successes, I was struck in this flight by the extent to which (at least to me) the Raptors looked very "clean" throughout the flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 05/05/2021 11:00 pm
Beyond the obvious successes, I was struck in this flight by the extent to which (at least to me) the Raptors looked very "clean" throughout the flight.
Yep. No engine fires on the way up that I could see.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Orbiter on 05/05/2021 11:01 pm
Not sure if anyone pointed it out, but all the heatshield tiles seemed to be intact.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: punder on 05/05/2021 11:02 pm
They mounted the exterior camera on one of the flaps! Awesome.

Do they record the video onboard? That would be nice.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/05/2021 11:03 pm
Did anyone see a clear indication of a 3-engine restart or was it 2-engines?

And they landed with 2, so deeper throttle or more aggressive hover-slam.. (so difficult to gauge terminal acceleration)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: quagmire on 05/05/2021 11:05 pm
SpaceX feed was spotty. Could see all three engines gimbal for relight, but only saw 2 engine lit and the 3rd went back to stowed position. Not sure if failure to relight or had two good engines so computer didn't bother relighting 3rd.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alpha Control on 05/05/2021 11:05 pm
The fire was still burning as the webcast ended. Do we have confirmation that the fire is extinguished?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/05/2021 11:05 pm
Yes, it looked like only 2 Raptors lit. I don't know if that was intentional but John I. said three engines.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: steveleach on 05/05/2021 11:06 pm
The fire was still burning as the webcast ended. Do we have confirmation that the fire is extinguished?
Yep, fire seems to be out. NSF youtube stream is still showing it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: faadaadaa on 05/05/2021 11:07 pm
SpaceX, great job on finally landing (and keeping one) intact.  Now upgrade your fire suppression systems with multiple water cannons, foam, halon, SOMETHING.  It's like they're using a garden hose right now.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: abaddon on 05/05/2021 11:08 pm
It looks like when it landed the vehicle jumped or slid across the ground.
Nice catch.  Not surprising, Falcon will also drift a bit right before touchdown.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Jim Graves on 05/05/2021 11:13 pm
SN-15 stuck the landing! I have been wanting to say that since SN-8 made it's historic first flight. Given that SN 8-11 went bang I was hopeful the upgrades would give SN-15 a greater chance of a complete success, but that fire on the pad worries me. I am definitely interested to know what the cause of the fire was and how it can be prevented on future starships. However, as SN-15 stands tall and proud on the pad, the concept is proven.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/05/2021 11:17 pm
It looks like when it landed the vehicle jumped or slid across the ground. Note the darker spots next to each of the locations the legs are. (Also that was REALLY close to missing the pad.)

Please folks, stop posting comments and discussion in the Updates thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: punder on 05/05/2021 11:17 pm
It looks like when it landed the vehicle jumped or slid across the ground.
Nice catch.  Not surprising, Falcon will also drift a bit right before touchdown.
Why right? Why not left?

Sorry, I’ll take it to the party thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThereIWas3 on 05/05/2021 11:28 pm
I thought I saw the fire start on the ground as the ship got close.  This was on the camera in the engine bay.  So maybe something ignited on the ground and then the ship landed on it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ppb on 05/05/2021 11:29 pm
Big congratulations to the SpaceX engineering team. Biggest challenges in order of priority now as I see it are: 1) prove successful landings are repeatable; 2) prove feasibility/durability of heat shield through orbital reentry; 3) reflight of both stages; 4) orbital refueling.  Tremendously exciting times indeed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AlexDS on 05/05/2021 11:30 pm
I think with the 2 Raptor landing burn it kicked itself a bit sideways and with that really close to the edge of the landing pad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/05/2021 11:36 pm
It looked like the landing was an intentional "reverse powerslide"... i.e. the same as SN5/6 takeoff (goes sideways as it lifts off due to assymetric thrust), but done in reverse.

So SN15 came in with a slight horizontal velocity and tried to cancel out both horizontal and vertical velocity at the same time to land exactly upright. Which it almost did perfectly - as @mlinder pointed out (https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233146#msg2233146), it did slide slightly on the ground.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: thirtyone on 05/05/2021 11:38 pm
Since it was a two engine landing burn - is it possible the new raptors have even deeper throttle range than the original ones? or is there just enough ballast mass in this vehicle?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/05/2021 11:39 pm
Since it was a two engine landing burn - is it possible the new raptors have even deeper throttle range than the original ones? or is there just enough ballast mass in this vehicle?

It might have had more propellant ballast, as it has been venting for a while now. As they optimize things fully, I'd expect them to land as empty as possible.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/05/2021 11:42 pm
For those who may not have been watching NSF's own stream, there's some really fun new "Starship Landing Club" merch in the NSF site store. I just picked up a new coffee mug as a memento and to help thank the team for all the great coverage these past many months.

https://shop.nasaspaceflight.com/collections/landing-club
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 05/05/2021 11:43 pm
Congrats Elon and all the SpaceX team! 8)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 05/05/2021 11:48 pm
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad. Presumably the deorbit timing would need to be precise enough to get them close to the right touchdown spot, and then the reentry flap movements would need to further navigate Starship to the appropriate vertical point where the pad can be attained during the skydive. I wonder if a future 10km test flight could put some "lateral crossrange" into the top of the flight so that SS needs to navigate during skydive to the pad? A SN16 flight, or SN15 reflight, might be able to do a bit of testing in this realm.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/05/2021 11:52 pm
Did anyone see a clear indication of a 3-engine restart or was it 2-engines?

And they landed with 2, so deeper throttle or more aggressive hover-slam.. (so difficult to gauge terminal acceleration)

As indicated to me, the 2 landing engines were NOT the preferred engines.   A preferred engine either didn't relight or was voted off the island.

So not QUITE nominal.  Nominal in the sense that the back-up engine strategy worked well and once the change-over occurred, everything went to plan - but the contingency WAS used.  A point to note.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vultur on 05/05/2021 11:54 pm
So cool!

I figured they'd fixed the "previous generation" (SN8-11) issues, but thought something new might blow up. But it didn't. Awesome.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/06/2021 12:01 am
Did anyone see a clear indication of a 3-engine restart or was it 2-engines?

And they landed with 2, so deeper throttle or more aggressive hover-slam.. (so difficult to gauge terminal acceleration)

As indicated to me, the 2 landing engines were NOT the preferred engines.   A preferred engine either didn't relight or was voted off the island.

So not QUITE nominal.  Nominal in the sense that the back-up engine strategy worked well and once the change-over occurred, everything went to plan - but the contingency WAS used.  A point to note.

How was it indicated to you? If you are referring to the SpaceX SN15 webcast, it is possible that Insprucker(?) misread or did not have up to date info.

Looking at the stream, they did not even attempt to start the 3rd engine. (see attached GIF). So either a fault was detected before startup or they only attempted to start 2. So we don't yet know for sure if the landing when 100% as planned, or an engine problem was detected and the back-up strategy was 100% successful.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/06/2021 12:06 am
Beyond the obvious successes, I was struck in this flight by the extent to which (at least to me) the Raptors looked very "clean" throughout the flight.
It was clean, no fires and none of the wild swinging around we saw on previous flights.  Of course, maybe the occasionally frozen video helped with that, some?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: netavatar on 05/06/2021 12:08 am
Did anyone see a clear indication of a 3-engine restart or was it 2-engines?

If Starship relights engines in a staggered way, then if by light all 3, could they mean that all 3 are in the relight sequence/plan, but if the first two relight okay, then the 3rd one is canceled and it's not a fault.

So I'm also curious about where it was indicated that the engine that didn't relight was in the plan to be used.

And they landed with 2, so deeper throttle or more aggressive hover-slam.. (so difficult to gauge terminal acceleration)

As indicated to me, the 2 landing engines were NOT the preferred engines.   A preferred engine either didn't relight or was voted off the island.

So not QUITE nominal.  Nominal in the sense that the back-up engine strategy worked well and once the change-over occurred, everything went to plan - but the contingency WAS used.  A point to note.

How was it indicated to you? If you are referring to the SpaceX SN15 webcast, it is possible that Insprucker(?) misread or did not have up to date info.

Looking at the stream, they did not even attempt to start the 3rd engine. (look at it again). So either a fault was detected before startup or they only attempted to start 2. So we don't yet know for sure if the landing when 100% as planned, or an engine problem was detected and the back-up strategy was 100% successful.

If there's a staggered relight sequence, then if first two relight okay, 3rd engine relight may be canceled. Spacex may still consider all 3 engines as part of the relight sequence.

I'm also interested in where it was indicated that the engine that didn't relight was supposed to be a landing engine.



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/06/2021 12:15 am
Did anyone see a clear indication of a 3-engine restart or was it 2-engines?

If Starship relights engines in a staggered way, then if by light all 3, could they mean that all 3 are in the relight sequence/plan, but if the first two relight okay, then the 3rd one is canceled and it's not a fault.

So I'm also curious about where it was indicated that the engine that didn't relight was in the plan to be used.

And they landed with 2, so deeper throttle or more aggressive hover-slam.. (so difficult to gauge terminal acceleration)

As indicated to me, the 2 landing engines were NOT the preferred engines.   A preferred engine either didn't relight or was voted off the island.

So not QUITE nominal.  Nominal in the sense that the back-up engine strategy worked well and once the change-over occurred, everything went to plan - but the contingency WAS used.  A point to note.

How was it indicated to you? If you are referring to the SpaceX SN15 webcast, it is possible that Insprucker(?) misread or did not have up to date info.

Looking at the stream, they did not even attempt to start the 3rd engine. (look at it again). So either a fault was detected before startup or they only attempted to start 2. So we don't yet know for sure if the landing when 100% as planned, or an engine problem was detected and the back-up strategy was 100% successful.

If there's a staggered relight sequence, then if first two relight okay, 3rd engine relight may be canceled. Spacex may still consider all 3 engines as part of the relight sequence.

I'm also interested in where it was indicated that the engine that didn't relight was supposed to be a landing engine.
Some random guy noted that the "maximum lever arm" selection criteria was not observed, so potentially one of the chosen ones got voted off the island.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DigitalMan on 05/06/2021 12:22 am
Did anyone see a clear indication of a 3-engine restart or was it 2-engines?

If Starship relights engines in a staggered way, then if by light all 3, could they mean that all 3 are in the relight sequence/plan, but if the first two relight okay, then the 3rd one is canceled and it's not a fault.

So I'm also curious about where it was indicated that the engine that didn't relight was in the plan to be used.

And they landed with 2, so deeper throttle or more aggressive hover-slam.. (so difficult to gauge terminal acceleration)

As indicated to me, the 2 landing engines were NOT the preferred engines.   A preferred engine either didn't relight or was voted off the island.

So not QUITE nominal.  Nominal in the sense that the back-up engine strategy worked well and once the change-over occurred, everything went to plan - but the contingency WAS used.  A point to note.

How was it indicated to you? If you are referring to the SpaceX SN15 webcast, it is possible that Insprucker(?) misread or did not have up to date info.

Looking at the stream, they did not even attempt to start the 3rd engine. (look at it again). So either a fault was detected before startup or they only attempted to start 2. So we don't yet know for sure if the landing when 100% as planned, or an engine problem was detected and the back-up strategy was 100% successful.

If there's a staggered relight sequence, then if first two relight okay, 3rd engine relight may be canceled. Spacex may still consider all 3 engines as part of the relight sequence.

I'm also interested in where it was indicated that the engine that didn't relight was supposed to be a landing engine.
Some random guy noted that the "maximum lever arm" selection criteria was not observed, so potentially one of the chosen ones got voted off the island.

From Everyday Astronauts footage, the 2 raptors looked in-line horizontal to the ground. Could be that is not a coincidence.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/06/2021 12:28 am
There are enough dropped frames in the official stream that it's very possible that the third engine was lit briefly for a fraction of a second, then shut down when they had all engines healthy, but we missed it.

It's also possible that they decided that lighting all three engines was actually exacerbating the header tank problem just by drawing the fuel out that much faster. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/06/2021 12:38 am
Marvelous!

But what about that fire after landing?

It was dismissed on the SpaceX feed but I wonder if it isn't a potential issue, especially with the methane potentially venting?

Of course it's a potential issue.  It hasn't blown up yet.  Whether it does or doesn't, they will iterate and fix it.

meta-remark:   Welcome.  But discussion is supposed to be conduction in Discussion threads (or general threads), if a Thread is Titled "UPDATES", discussion is not to be conducted there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/06/2021 12:39 am
Marvelous!

But what about that fire after landing?

It was dismissed on the SpaceX feed but I wonder if it isn't a potential issue, especially with the methane potentially venting?

Welcome to NSF! Please be sure to post all questions and commentary in a Discussion thread, not the Update thread.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kabloona on 05/06/2021 12:43 am

[snip]

It's also possible that they decided that lighting all three engines was actually exacerbating the header tank problem just by drawing the fuel out that much faster.

Seems to me that makes the most sense. Light two engines high enough that you have the timing margin to relight the 3rd if one of the first two fails. This is the staggered sequence suggested upthread by netavatar.

But if the first two engines are stable, you're golden. I think that's what we saw today.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alphacentauri on 05/06/2021 12:54 am
The arstechnica coverage of the flight says the landing flip occurred at a higher altitude than previous flights, giving more time to reach the vertical position and land straight. Hard to verify the flip details given the cloud cover and intermittent video. Maybe we'll see more after SpaceX can retrieve video stored on the vehicle.

https://arstechnica.com/science/2021/05/spacex-successfully-lands-a-starship-test-flight/
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kabloona on 05/06/2021 12:59 am
The arstechnica coverage of the flight says the landing flip occurred at a higher altitude than previous flights, giving more time to reach the vertical position and land straight. Hard to verify the flip details given the cloud cover and intermittent video. Maybe we'll see more after SpaceX can retrieve video stored on the vehicle.

https://arstechnica.com/science/2021/05/spacex-successfully-lands-a-starship-test-flight/

That would seem to fit with the 2-engine relight logic of my previous post. The earlier/higher relight gives more time for a 3rd engine relight if needed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/06/2021 12:59 am
Marvelous!

But what about that fire after landing?

It was dismissed on the SpaceX feed but I wonder if it isn't a potential issue, especially with the methane potentially venting?

Of course it's a potential issue.  It hasn't blown up yet.  Whether it does or doesn't, they will iterate and fix it.

meta-remark:   Welcome.  But discussion is supposed to be conduction in Discussion threads (or general threads), if a Thread is Titled "UPDATES", discussion is not to be conducted there.

It may be unavoidable.  There's a decent bit of fuel (several liters at least) left in the pipes downstream of the valves after engine shutoff, and something has to happen to it.  So it makes its way out through the nozzle and catches fire.

Also, since methane vaporizes so easily, even a relatively small amount can make a large flame.  But this means that you're combusting a small amount of fuel in a large volume of air, and thus it's not a very hot fire.  Keep in mind that this section of the vehicle has to survive being thoroughly roasted by the proximity of incredibly hot, rapidly burning rocket exhaust.  It would take a substantial fire to match this.

Note that on Falcon 9 landings, we also tend to see fires under the booster after it lands.  The difference is that kerosene doesn't vaporize off as easily, and so remains in a puddle on the ground.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sanman on 05/06/2021 01:07 am
Such a great touchdown! Congrats to SpaceX! Now Elon can host SNL triumphantly, as a victory lap.

Only nitpick is that I wish mother nature had cooperated by putting up less cloud cover to obscure our view of the moment of glory. Would have been great to see the entire descent in a cloudless sky, given how impressive skydiver bellyflop looks while in motion.

I liked how clean the engines looked in the underskirt view during launch -- none of the gassy flaminess that plagued previous launches.

Some fire on the ground at the end, which made for some post-landing anxiety during what seemed like a long de-tanking. With Robo-dog Zeus inspecting the underskirt area post-landing, it makes me wonder whether this will become standard procedure for landings on Moon and Mars.

How long before SN16 gets rolled out? Or will nosecone stress test come first?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 05/06/2021 01:07 am
Marvelous!

But what about that fire after landing?

It was dismissed on the SpaceX feed but I wonder if it isn't a potential issue, especially with the methane potentially venting?

Of course it's a potential issue.  It hasn't blown up yet.  Whether it does or doesn't, they will iterate and fix it.

meta-remark:   Welcome.  But discussion is supposed to be conduction in Discussion threads (or general threads), if a Thread is Titled "UPDATES", discussion is not to be conducted there.

It may be unavoidable.  There's a decent bit of fuel (several liters at least) left in the pipes downstream of the valves after engine shutoff, and something has to happen to it.  So it makes its way out through the nozzle and catches fire.

Also, since methane vaporizes so easily, even a relatively small amount can make a large flame.  But this means that you're combusting a small amount of fuel in a large volume of air, and thus it's not a very hot fire.  Keep in mind that this section of the vehicle has to survive being thoroughly roasted by the proximity of incredibly hot, rapidly burning rocket exhaust.  It would take a substantial fire to match this.

Note that on Falcon 9 landings, we also tend to see fires under the booster after it lands.  The difference is that kerosene doesn't vaporize off as easily, and so remains in a puddle on the ground.


Would it not be more likely to be residual LOX reacting to 'fuel' source present?


Also from the last frame of the engine bay from the SpaceX stream after the landing the fire looked to come from the side away from the engines.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Andro on 05/06/2021 01:09 am
First time poster, long time watcher (Since CRS-4)

As people have said, the two engines that relit were not the two ideal engines for a long 2 engine landing, even if the landing started at a higher altitude than previous flights.

I could be very wrong but my gut feeling is the back left engine's TVC failed as I don't think it quite manoeuvred into the exact same position/level as the back right engine, meaning no start up would occur and the contingency plan for the other 2 engines to take over the landing would come into effect. Then when relight occurs, the engine not in-use tries to gimbal as much as it can to get out of the way. (So the problem would be to do with the other direction of gimbal?)

Watch the engines gimbal very slightly differently. (GIF is at 0.5x speed)

Anyone know which Raptor SN is the one that did not relight?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 05/06/2021 01:19 am
  Speculation on next flight:
  The Integration Tower is going to require 'Big Red', the LR 11350, in a configuration that can't be easily moved from the launch/land test site. Once they assemble the main boom/jib boom combo that crane is committed to finishing the tower before being down sized to a transportable configuration.
  SN15 is back after a successful (so far) hop, and SN16 is close to being ready for a trip to a pad. If a test flight is deemed a priority before 'Big Red' becomes really big, then there could be two possible campaigns.
 
  1) If SN15 passes it's post flight physical, throw it back up on a pad and send it skyward pronto.
  2) If SN15 needs more post flight recovery time, expedite SN16. When SN16 is transported to the pad it seems that a couple of weeks is a fair amount of time for getting it flight ready.

  The teams doing tower construction at the gas well site can continue to be busy beavers since there are 4 (maybe 5) tower jigs there. With these sections finished, they can be quickly transported to the launch site when 'Big Red' is ready.
  Whatever is decided, I don't see any test flight happening once 'Big Red' returns to the launch/land site.
 
  Also, very interested to see the large transport frame that is integrated with the SPMTs go into action moving SN15.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: frogamazog on 05/06/2021 01:19 am
Ars Technica is reporting that they started the burn from higher up, but I don't see any substantiation of that claim. It would make sense for them to do this, if only to have a prototype that they can actually dissect down to its last detail after flight. However, I'm not sure if this impression might just come from the low cloud layer.

I see that the main thread here is about the engines, but anyone want to weight in on the relight altitude?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/06/2021 01:24 am
https://twitter.com/larsblackmore/status/1390114456986918917

Quote
Amazing to see “congrats SpaceX” trending 😀 The whole team has been unbelievable up to and through this flight. Thanks to all of you!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Navier–Stokes on 05/06/2021 01:30 am
Ars Technica is reporting that they started the burn from higher up, but I don't see any substantiation of that claim. It would make sense for them to do this, if only to have a prototype that they can actually dissect down to its last detail after flight. However, I'm not sure if this impression might just come from the low cloud layer.

I see that the main thread here is about the engines, but anyone want to weight in on the relight altitude?
Onespeed's analysis suggests the burn started ~50m higher.

Here is a comparison of the landings of SN10 and SN15 using pixel counting of the webcast video frames.

Some points to note are:

1. The much smoother and more continuous change in velocity of SN15.
2. That lack of a roughly 9g peak in acceleration at the landing of SN15.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Khadgars on 05/06/2021 01:44 am
Congrats SpaceX!  Amazing to watch that thing land  :D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Johnnyhinbos on 05/06/2021 01:46 am
Starship SN15 liftoff and nailed the landing.
Mary!

(Yes, I know this is not an update - but Mary deserves it, x15)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/06/2021 01:49 am
Does anyone know any details about what caused or contributed to the SN15 fire?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Starblazer on 05/06/2021 01:50 am
Transporter heading to pad!

Did this thing ever get a name like all the other SpaceX vehicles? My vote is the SSPMT, or the Super Self-Propelled Modular Transporter.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kabloona on 05/06/2021 01:58 am
Ars Technica is reporting that they started the burn from higher up, but I don't see any substantiation of that claim. It would make sense for them to do this, if only to have a prototype that they can actually dissect down to its last detail after flight. However, I'm not sure if this impression might just come from the low cloud layer.

I see that the main thread here is about the engines, but anyone want to weight in on the relight altitude?
Onespeed's analysis suggests the burn started ~50m higher.


It may not be that clear. OneSpeed's plots show #15 coming in higher and faster over the 14 second interval before touchdown, but it's not obvious to me in either plot where ignition actually occurs.

Watching the videos of both, #10 ignition occurs about 21 seconds before touchdown, while #15 occurs about 16 seconds before touchdown. So OneSpeed's plots don't even begin until 7 seconds after #10 ignition, and 2 seconds after #15 ignition.

I can draw plausible extrapolations of the altitude plots back in time, but the 5 second difference in ignition points along the X-axis means that, depending on how I do the extrapolation, #15 ignition can occur higher, lower, or at the same altitude as #10.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raketa on 05/06/2021 02:10 am
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad. Presumably the deorbit timing would need to be precise enough to get them close to the right touchdown spot, and then the reentry flap movements would need to further navigate Starship to the appropriate vertical point where the pad can be attained during the skydive. I wonder if a future 10km test flight could put some "lateral crossrange" into the top of the flight so that SS needs to navigate during skydive to the pad? A SN16 flight, or SN15 reflight, might be able to do a bit of testing in this realm.
Wings has more maneuverability than grid fins, I think they have no problem reach target position accurately.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/06/2021 02:20 am
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad. Presumably the deorbit timing would need to be precise enough to get them close to the right touchdown spot, and then the reentry flap movements would need to further navigate Starship to the appropriate vertical point where the pad can be attained during the skydive. I wonder if a future 10km test flight could put some "lateral crossrange" into the top of the flight so that SS needs to navigate during skydive to the pad? A SN16 flight, or SN15 reflight, might be able to do a bit of testing in this realm.
Wings has more maneuverability than grid fins, I think they have no problem reach target position accurately.
Maybe so, but these aren't wings in any conventional sense, so the comparison is not relevant.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/06/2021 02:46 am
Does anyone know any details about what caused or contributed to the SN15 fire?

Raptor shutdown does appear to be a bit "leaky" at this development stage - it seems let out a bit of methane as it shuts down. (This can be seen during other flights as engines shut down during ascent)

That was probably what was burning.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: yg1968 on 05/06/2021 02:54 am
See below:

Video of the flip maneuver:

https://twitter.com/considercosmos/status/1390135292183695362

https://twitter.com/Erdayastronaut/status/1390125636417642496
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: frogamazog on 05/06/2021 03:02 am
That everyday astronaut landing footage wins best video of this launch, in my book. Just. Incredible.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/06/2021 03:02 am
See below:

Why?  If you're going to do this (cross-post your own UPDATE to DISCUSSION), at least explain why or contextualize it by quoting the person you're directing this to.  Otherwise it's sort of unseemly.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: yg1968 on 05/06/2021 03:05 am
See below:

Why?  If you're going to do this (cross-post your own UPDATE to DISCUSSION), at least explain why or contextualize it by quoting the person you're directing this to.  Otherwise it's sort of unseemly.

Because I have posted updates like that before that have gotten deleted. The discussion thread seems to be less strict.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/06/2021 03:10 am
Huge congrats to SpaceX for the amazing flight today!

A few remarks:

- I hope that the vehicle cameras were recording locally and we will be able to see a montage from footage stored on the cameras. This would be awesome given that the cameras on the others SNs were presumably destroyed in RUDs.
- It seems like the heatshield tiles did pretty well, particularly the large patch!
- The Raptor plumes looked really clean, and the lack of external fires in the engine bay was great to see
- Still not sure what exactly happened with the 2 engine landing burn or what to make of it. In any case, if three engines were supposed to have been ignited and only two did, this was a great demonstration of engine out capability on landing
- The success today probably helped to put another nail in the coffin on the HLS protest debacle. I hope so anyway!
- SN15 was approached by people much sooner than SN5 and SN6
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JaimeZX on 05/06/2021 03:20 am
Is it me or was there some really orange exhaust?  At first I thought maybe it was just the clouds reflecting the glow of the Raptors, but it was too localized as the flight progressed.  (Ref: SpaceX stream at about T+50s)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: 50_Caliber on 05/06/2021 03:21 am
The excitement will just continue to ramp up. What's next for SN15 and SN16? Higher, faster, to the Karman line? What do they do with them when they come back intact? A fleet is beginning to take shape.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: M.E.T. on 05/06/2021 03:23 am
Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/06/2021 03:32 am
Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/06/2021 03:35 am
Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

In a pure CO2 environment, you won't even see a flame.  It won't even catch fire.  In fact a 1% Oxygen environment wouldn't support much of a fire either.  It would likely take a lot longer to burn out but at a lower intensity.

They need to find a way to direct and vent the methane.  No one wants to ride vehicle that catches fire when it lands.  They'll get that sorted soon.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sdub on 05/06/2021 03:44 am
Is it me or was there some really orange exhaust?  At first I thought maybe it was just the clouds reflecting the glow of the Raptors, but it was too localized as the flight progressed.  (Ref: SpaceX stream at about T+50s)

It did leave a somewhat unattractive brownish orange region of exhaust below on lift off against the thick grey white cloud cover. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 05/06/2021 03:48 am
First time poster, long time watcher (Since CRS-4)

As people have said, the two engines that relit were not the two ideal engines for a long 2 engine landing, even if the landing started at a higher altitude than previous flights.

I could be very wrong but my gut feeling is the back left engine's TVC failed as I don't think it quite manoeuvred into the exact same position/level as the back right engine, meaning no start up would occur and the contingency plan for the other 2 engines to take over the landing would come into effect. Then when relight occurs, the engine not in-use tries to gimbal as much as it can to get out of the way. (So the problem would be to do with the other direction of gimbal?)

Watch the engines gimbal very slightly differently. (GIF is at 0.5x speed)

Anyone know which Raptor SN is the one that did not relight?

Welcome!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/06/2021 04:02 am
Is that something that is expected for a FFSC engine with a cryogenic fuel?

How would you vent or burn off the methane down stream of a shutoff valve?  Maybe it needs to be ducted/vented away.

Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.

I suspect the fairly large volume of liquid Methane contained in the cooling channels of the engine bells is the source of the steady stream of combustible gas we are seeing after various engine shutdown scenarios.

Residual heat would cause this to boil off rapidly and it would need to be vented somewhere or otherwise cause something in the Raptor to rupture...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/06/2021 04:13 am
Transporter heading to pad!

Did this thing ever get a name like all the other SpaceX vehicles? My vote is the SSPMT, or the Super Self-Propelled Modular Transporter.

Given the crazy construction formed from multiple smaller ones, I’d go with “Voltron”.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VoodooForce on 05/06/2021 04:15 am
Is it me or was there some really orange exhaust?  At first I thought maybe it was just the clouds reflecting the glow of the Raptors, but it was too localized as the flight progressed.  (Ref: SpaceX stream at about T+50s)

It did leave a somewhat unattractive brownish orange region of exhaust below on lift off against the thick grey white cloud cover.

I think that is dust
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/06/2021 04:19 am
Is it me or was there some really orange exhaust?  At first I thought maybe it was just the clouds reflecting the glow of the Raptors, but it was too localized as the flight progressed.  (Ref: SpaceX stream at about T+50s)

It did leave a somewhat unattractive brownish orange region of exhaust below on lift off against the thick grey white cloud cover.

I think that is dust

More likely Nitrogen Dioxide, often a by-product of combustion in air.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ppb on 05/06/2021 04:24 am
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad. Presumably the deorbit timing would need to be precise enough to get them close to the right touchdown spot, and then the reentry flap movements would need to further navigate Starship to the appropriate vertical point where the pad can be attained during the skydive. I wonder if a future 10km test flight could put some "lateral crossrange" into the top of the flight so that SS needs to navigate during skydive to the pad? A SN16 flight, or SN15 reflight, might be able to do a bit of testing in this realm.
Wings has more maneuverability than grid fins, I think they have no problem reach target position accurately.
Maybe so, but these aren't wings in any conventional sense, so the comparison is not relevant.
Actually, it is very relevant. Both vehicles use body lift to guide the vehicle to the target. F9 uses the grid fins to modulate small angles of attack with respect to the body long axis and create lift normal to the body. SS uses the body flaps to modulate a large angle of attack perpendicular to the body long axis and to create lift parallel to that axis.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KilroySmith on 05/06/2021 05:08 am
I noticed something in the runup to launch.

No Frost.  No Frost on the header tank, on the LOX Tank, on the Methane tank.  Pretty unusual - any guesses?.  BUT, there was a thin ring of heavy frost about one ring above the vents.  What's there that would be cold enough to create frost when the rest of the tankage wasn't?

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sanman on 05/06/2021 05:41 am
I noticed something in the runup to launch.

No Frost.  No Frost on the header tank, on the LOX Tank, on the Methane tank.  Pretty unusual - any guesses?.  BUT, there was a thin ring of heavy frost about one ring above the vents.  What's there that would be cold enough to create frost when the rest of the tankage wasn't?

There seemed to be frost after landing. Is it possible that the higher winds today kept frost from showing, at least on the camera side?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sanman on 05/06/2021 05:42 am
What will the flight of SN16 look like? Will it be the same as SN15, or will it fly farther/higher/faster?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/06/2021 06:03 am
What will the flight of SN16 look like? Will it be the same as SN15, or will it fly farther/higher/faster?
Since SN15 is successful the higher altitudes should become one of the options
Quote from: NSF article
Should SN15 complete all the required high altitude test objectives, SpaceX may repeat the test or push to a higher altitude. Elon Musk could even opt to switch to the involvement of Super Heavy, which may involve a booster-only flight, or the previously reported BN3 and SN20 orbital flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JET777 on 05/06/2021 06:54 am

at least they have a surviving prototype to see firsthand what went wrong (fire upskirt)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ppb on 05/06/2021 06:56 am
Anybody have information (or make some good educated guesses) on the improvements in SN15 compared to 8-11 that made the critical difference? Obviously the Raptors were much better: this is the only SN that didn’t have to swap any out after a static fire, if memory serves. Big changes in the tank baffling, plumbing or pressurization systems? Can anybody provide details here, or are these simply too closely guarded secrets?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Science on 05/06/2021 07:03 am
DC-X says "congratulations kid you graduated!" 8)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Yggdrasill on 05/06/2021 07:32 am
DC-X says "congratulations kid you graduated!" 8)
DC-X is more equivalent to Hoppy, though. DC-X didn't go horizontal or relight the engines during flight. SN15 went over three times higher and flew almost three times longer than the highest/longest flight of DC-X.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ocisly on 05/06/2021 07:45 am
DC-X says "congratulations kid you graduated!" 8)
DC-X is more equivalent to Hoppy, though. DC-X didn't go horizontal or relight the engines during flight. SN15 went over three times higher and flew almost three times longer than the highest/longest flight of DC-X.

The DC-X definitely when horizontal. Maybe not completely though. I don't know about relights though.

1:36

https://www.youtube.com/watch?v=yW2w2EH8lr8

EDIT: Here's a better example

0:57

https://www.youtube.com/watch?v=JzXcTFfV3Ls



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rossco on 05/06/2021 07:54 am
Congrats to the SpaceX team!

Wouldn't they just put SN15 back on the stand for inspection/re-flight rather than transporting it back to the production site for inspection?
Bring SN16 out to the 2nd stand and then move the big red crane down to the tower whilst SN16 undergoes its pre-flight tests.
Also it looked like SpaceX switched to some engineering camera's during the flight? I wonder if they have a more stable feed available for their own internal use.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacexplorer on 05/06/2021 08:04 am
I'm very happy to see the rocket didn't explode again during/after landing, but my vote for this landing is C; checklist of things to remove/improve:
- bouncing after landing
- fire on pad after landing
- near-miss of the landing pad
- landing close to to other rockets yet to be launched

Look at  dark footprints of legs and near-miss of the landing pad:
(https://forum.nasaspaceflight.com/assets/53509.0/2031871.jpg)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rlhamil on 05/06/2021 08:12 am
Also it looked like SpaceX switched to some engineering camera's during the flight? I wonder if they have a more stable feed available for their own internal use.

I heard a report that they had Starlink antenna on SN15. If so, it's reasonable that they would have put less critical data (like video) on that.

Since it's back intact, any stored video will still be available. Give it a few days, maybe they'll release something more polished.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StefsEngineering on 05/06/2021 08:47 am
Like they did with SN8? That video also included not before seen angles like the one from the launchpad looking up at the raptors during launch. Lets hope so!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/06/2021 09:05 am
https://twitter.com/jinsprucker/status/1390146081577603077

Quote
A few of my favorite phrases from sci-fi suddenly have new meaning. Fighting through landing-"Never give up, never surrender!" "Oh! My God! It's real," when we've done it.  And of course "These are the voyages of the Starship(s)..." Cue the music. Now to work on video and clouds.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 05/06/2021 09:20 am
Also it looked like SpaceX switched to some engineering camera's during the flight? I wonder if they have a more stable feed available for their own internal use.

I heard a report that they had Starlink antenna on SN15. If so, it's reasonable that they would have put less critical data (like video) on that.

Since it's back intact, any stored video will still be available. Give it a few days, maybe they'll release something more polished.
They’ll be some external recordings that they didn’t put on the live feed (the one from the bottom looking up). It’ll be in their interest to get a recap video up ASAP as we probably haven’t seen all of the flip n burn in its glory.

Anyone with doubt still, this is an experimental project now coming into a more mature phase now (seems like the 300+ improvements has given them a great bloc to work with) and feed any new data into SN20+ designs. I’m not so worried about the video feeds or to what we saw as that’s far down the priority list. It’ll be nice to see this again on SN16 with a clear day like we go on SN8-10.

The flap cam was probably the coolest thing to see. Even if choppy to see the work it’s doing.

Looking at the landing again; it was clearly back to an SN8 style landing trajectory with the smooth curve. We were just unlucky with the engine eat-out that caused the RUD.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Noto on 05/06/2021 09:40 am
Is it possible the post-landing fire was intentional? (or at least a CH4 dump at the bottom, and not purely relying on the tank vents at the top?) I remember from SN5/6 it took several days before SpaceX deemed it safe to approach the vehicle, but now personal was at the pad several hours after landing. Also the fire seem to originate at the leeward side in proximity of the quick-disconnect interfaces, and not leaking from any Raptor (like F9 dripping kerosene post landing). Just speculating here...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ylnj on 05/06/2021 09:45 am
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad.
...

I know they plan on catching the booster. Do they also plan to catch Starship? There are no “landing tower” on the Moon or Mars.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: niwax on 05/06/2021 09:50 am
Current NSF view

Edit to add:

https://twitter.com/nasaspaceflight/status/1390073490536075269

I really like this view with the ice only on one side of the vehicle where the propellant pooled after the flop. You can probably get some appreciable cooling effect from the evaporating methane as well in a pinch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: electric on 05/06/2021 10:00 am
I noticed something in the runup to launch.

No Frost.  No Frost on the header tank, on the LOX Tank, on the Methane tank.  Pretty unusual - any guesses?.  BUT, there was a thin ring of heavy frost about one ring above the vents.  What's there that would be cold enough to create frost when the rest of the tankage wasn't?

There seemed to be frost after landing. Is it possible that the higher winds today kept frost from showing, at least on the camera side?
Before the launch, most of the fuel is in the bulkheads and has no contact with the outer hull which means that no frost will form. But during the descent phase, the fuel will be on the side of the vehicle with direct contact to the hull, which means that there will be frost on that side after the landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: erv on 05/06/2021 10:47 am
Where the "no frost" thing comes from? There was well visible frost lines at least 5 minutes before liftoff.
After the flight when NSF guys (thanks for the stream!) run the replays I also noticed that on the danger cam (? - the one that shows the close-up) it was nicely seen that on liftoff much of that frost fell off, before being obscured by smoke.
Attached a crop from SpaceX feed with some arrows added.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/06/2021 10:56 am
twitter.com/js2tango/status/1390075015006130184?s=21

Quote
@torybruno Thoughts on the #SN15 flight and successful landing?

https://twitter.com/torybruno/status/1390258547599020032

Quote
Congratulations to Gwynne and the team. Hard work to get here.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RobLynn on 05/06/2021 12:15 pm
Good flight.
Seems likely there was a Raptor reliability issue again on relight for flip, but otherwise good show from engines.
Were the explosions heard after landing a result of underskirt COPV exploding due to fire heat?
On the wish list: more comprehensive fire suppression system for pad, perhaps a drone fire truck or two to be able to maneuver nozzles under skirt and spray some water or maybe liquid nitrogen on fire source (or would shock chilling like that be bad for engines?)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 05/06/2021 12:18 pm
twitter.com/js2tango/status/1390075015006130184?s=21

Quote
@torybruno Thoughts on the #SN15 flight and successful landing?

https://twitter.com/torybruno/status/1390258547599020032

Quote
Congratulations to Gwynne and the team. Hard work to get here.

Sounds like Elon is ‘You-know-who’ at ULA.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/06/2021 12:22 pm
Good flight.
Seems likely there was a Raptor reliability issue again on relight for flip, but otherwise good show from engines.
Were the explosions heard after landing a result of underskirt COPV exploding due to fire heat?
On the wish list: more comprehensive fire suppression system for pad, perhaps a drone fire truck or two to be able to maneuver nozzles under skirt and spray some water or maybe liquid nitrogen on fire source (or would shock chilling like that be bad for engines?)

First, the 2 v. 3 engine flip is still being debated. Could very well be a change in the plan to 2-engine flip and landing and John I’s notes were just not updated in time. Second, as for the post-landing “explosions,” I believe those were puddles of liquid CH4 left in the plumbing from engine shutdown spilling out, flashing to vapor in the heat of the local environment and then detonating or conflagrating quickly. The sound was probably amplified by the enclosed area under the skirt and the various berms and vertical tank surfaces around.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben the Space Brit on 05/06/2021 12:24 pm
On the wish list: more comprehensive fire suppression system for pad, perhaps a drone fire truck or two to be able to maneuver nozzles under skirt and spray some water or maybe liquid nitrogen on fire source (or would shock chilling like that be bad for engines?)

Shock chilling is bad, very bad, for anything. As in 'high-tensile alloys shattering like glass' bad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/06/2021 12:25 pm
twitter.com/js2tango/status/1390075015006130184?s=21

Quote
@torybruno Thoughts on the #SN15 flight and successful landing?

https://twitter.com/torybruno/status/1390258547599020032

Quote
Congratulations to Gwynne and the team. Hard work to get here.

Sounds like Elon is ‘You-know-who’ at ULA.

Nah, Gwynne really is his counterpart in SpaceX. Tory is actually a pretty good sport. He is watching SpaceX eating his company’s lunch, but deep down, he’s a space fan too, the reason he’s where he is. I bet he is watching this as close as we are. Not just as a competitor, but as a space fan as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Elmar Moelzer on 05/06/2021 12:34 pm
Nah, Gwynne really is his counterpart in SpaceX. Tory is actually a pretty good sport. He is watching SpaceX eating his company’s lunch, but deep down, he’s a space fan too, the reason he’s where he is. I bet he is watching this as close as we are. Not just as a competitor, but as a space fan as well.
Tory wants to tackle reusability at ULA as well, but the bean counters at Boeing and Lockmart don't want it. I think he is secretly hoping that SpaceX's success will open that door for him and ULA as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 05/06/2021 12:38 pm
twitter.com/js2tango/status/1390075015006130184?s=21

Quote
@torybruno Thoughts on the #SN15 flight and successful landing?

https://twitter.com/torybruno/status/1390258547599020032

Quote
Congratulations to Gwynne and the team. Hard work to get here.

Sounds like Elon is ‘You-know-who’ at ULA.

Nah, Gwynne really is his counterpart in SpaceX. Tory is actually a pretty good sport. He is watching SpaceX eating his company’s lunch, but deep down, he’s a space fan too, the reason he’s where he is. I bet he is watching this as close as we are. Not just as a competitor, but as a space fan as well.

I don’t think there is any evidence that Gwynne has significant input to Starship engineering decisions (nor would you expect her to as she runs operations), whereas Elon is Chief Engineer and has his fingerprints all over it. Congratulating Gwynne, not Elon for a test flight is odd to say the least. I don’t think it’s likely that Tory accidentally forgot who’s rocket it is.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/06/2021 12:39 pm
I don't see why get why ULA would be opposed to reusable rockets. It's drastically cheaper in the long run.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/06/2021 12:39 pm
Nah, Gwynne really is his counterpart in SpaceX. Tory is actually a pretty good sport. He is watching SpaceX eating his company’s lunch, but deep down, he’s a space fan too, the reason he’s where he is. I bet he is watching this as close as we are. Not just as a competitor, but as a space fan as well.
Tory wants to tackle reusability at ULA as well, but the bean counters at Boeing and Lockmart don't want it. I think he is secretly hoping that SpaceX's success will open that door for him and ULA as well.

I think LockMart and BA will eventually sell or set ULA free. 

The natural fit to me seems to be Blue and ULA.  One has rockets and experience the other wants a working rocket. 

Edit: meanwhile SpaceX will just keep going.  They could be on the moon by the time any other provider really does much to catch up. 

Seems to me that in 10 or 20 years we may look back at several different giant rockets and spacecraft and realize that rockets always needed to be big, really big.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hyperborealis on 05/06/2021 12:44 pm
Tory probably thinks Elon gets too much attention, for what is a team effort. Hell, Elon wouldn't disagree on that count. But he's got the attention, and is using it to help SpaceX, as he should. Working with what you have.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/06/2021 12:45 pm
I don't see why get why ULA would be opposed to reusable rockets. It's drastically cheaper in the long run.

It's the R&D costs involved, when a competitor has such a long head start. ULA didn't even want to spend the money to develop rocket engines either so they are buying them from Blue Origin.

This is the same problem legacy car makers are facing with Tesla. When you have an older company that is expected to provide quarterly results, it can be real hard to plow a ton of money into R&D to compete with a disruptor. Happens all the time with mature companies.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/06/2021 12:49 pm
Guys, the ULA plans and discussions about Boeing and Lockheed Martin’s corporate interests don’t belong in this thread. Tory said what he said about SN15’s successful test, so good for him. But the rest is off-topic.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/06/2021 12:50 pm
I don't see why get why ULA would be opposed to reusable rockets. It's drastically cheaper in the long run.

It's the R&D costs involved, when a competitor has such a long head start. ULA didn't even want to spend the money to develop rocket engines either so they are buying them from Blue Origin.

This is the same problem legacy car makers are facing with Tesla. When you have an older company that is expected to provide quarterly results, it can be real hard to plow a ton of money into R&D to compete with a disruptor. Happens all the time with mature companies.

Got it. Although I do feel that as commercial spaceflight gets bigger technology might start getting shared around.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/06/2021 02:05 pm
Nah, Gwynne really is his counterpart in SpaceX. Tory is actually a pretty good sport. He is watching SpaceX eating his company’s lunch, but deep down, he’s a space fan too, the reason he’s where he is. I bet he is watching this as close as we are. Not just as a competitor, but as a space fan as well.
Tory wants to tackle reusability at ULA as well, but the bean counters at Boeing and Lockmart don't want it. I think he is secretly hoping that SpaceX's success will open that door for him and ULA as well.

I think LockMart and BA will eventually sell or set ULA free. 

The natural fit to me seems to be Blue and ULA.  One has rockets and experience the other wants a working rocket. 

Edit: meanwhile SpaceX will just keep going.  They could be on the moon by the time any other provider really does much to catch up. 

Seems to me that in 10 or 20 years we may look back at several different giant rockets and spacecraft and realize that rockets always needed to be big, really big.
First, Bruno's shade is childish, but he's not in a position to do any harm so who cares.

Second, that dynamic where ULA is supposedly a suppressed agile aerospace company and where all the bad decisions are made by the clueless parents is equally childish.

ULA couldn't build anything but Vulcan. They've never built a rocket.  For 20 years or so, all they've done is operate two rockets given to them by the pre-merger organizations.

After all these years of doing mostly operations, even the step they took: making a similar EELV-like rocket and using someone else's engines, even that taxed them to the limit and is still not finished.

Bruno is frustrated I'm sure, but blaming the parents won't help.

EDIT: reverse thread contamination detected!  Yeah this is about ULA, mot SpaceX...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sanman on 05/06/2021 02:41 pm
What are the reasons for the fire burning at the base of the rocket after landing?

Is it just residual methane trapped under the skirt of the rocket?

Or are fuel valves somehow continuing to leak?

What are the possible remedies for this?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Prae_ on 05/06/2021 02:43 pm
What are the reasons for the fire burning at the base of the rocket after landing?

Is it just residual methane trapped under the skirt of the rocket?

Or are fuel valves somehow continuing to leak?

What are the possible remedies for this?

Probably all of the above. Remedies? Who knows, but they have the booster to study and they'll find solutions much easier this way.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CrazySpace on 05/06/2021 02:51 pm
And after SN15 landing succefull, what is the next spacex goal/step? Anybody knows?? Thx
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/06/2021 02:55 pm
And after SN15 landing succefull, what is the next spacex goal/step? Anybody knows?? Thx

Flight envelope expansion for Starship
SuperHeavy flight
Full stack orbital flight
SuperHeavy landings
In orbit refueling
Long term life support in space
Lunar lander engine development

This list could go for a bit. Still lots to do. Can’t wait to watch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Spindog on 05/06/2021 02:58 pm
It would seem to me that they will try faster speeds/higher altitudes needed to verify aerodynamic controls and structure prior to launching atop a superheavy. Possible that will include supersonic aerodynamics. In any case, I'd think we are done with the slow hover and flip profile.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rocket Surgeon on 05/06/2021 02:58 pm
And after SN15 landing succefull, what is the next spacex goal/step? Anybody knows?? Thx

Do it again to prove it wasn't a fluke :D
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/06/2021 02:59 pm
sanman and Prae_, you posted in the UPDATES thread. Please post comments here instead.

I want to push back a little on the fire being "nominal". I don't know how serious it was, but I think there's pretty good evidence that it's NOT supposed to happen (at least the way it did) based on the way the SpaceX crowd reacted in the video linked from Stargate. The guy said "the most important thing in the world is not being on fire".

Also, is it just me or did SN15 ascend more quickly than its predecessors? It seemed like it jumped off the launch mount.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Spindog on 05/06/2021 03:13 pm
And I'm sure they'd like to prove that the fins can handle high speeds without ripping off. It will be interesting to see how high they'll go and what speeds they can reach on ascent and descent without a full heat shield. But clearly the current profiles they've flown have been much slower than possible profiles that don't shutdown engines. I dont know how the switch to the header tanks prior to shutdown will work with a high speed shutdown of all 3 engines nearly simultaneously.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Chris Bergin on 05/06/2021 03:18 pm
Thread 21 will start in the next few days, per this being long already and SN16 :)

Meanwhile!

https://twitter.com/NASASpaceflight/status/1390322736640233480

https://www.youtube.com/watch?v=Yx2q1WPdAtA

Give him some love as he's doing great work!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/06/2021 03:24 pm
It would seem to me that they will try faster speeds/higher altitudes needed to verify aerodynamic controls and structure prior to launching atop a superheavy. Possible that will include supersonic aerodynamics. In any case, I'd think we are done with the slow hover and flip profile.

Real-world flight testing is not just about verifying your vehicle works, it also is about validating your computer models with real-world data. Things like Computational Fluid Dynamics or aerothermodynamic models use computer simulations to predict what will happen, so you use those tools to design your vehicle and its control system. But there is always error or approximation in those models. Even using a scale model of a vehicle in a wind tunnel involves some error as different factors scale at different rates. So when you fly a real vehicle in the real world at full scale, you can compare your actual behavior to the predicted behavior. From there, you can see where your model is good at predicting and where it's not. This means you can further refine your model and do even more simulation work at higher fidelity before you cut more metal, write more code, forge more alloy.

Long way of saying data from these flights aren't just to make sure this design of StarShip works, but to inform their models to make other simulations more accurate.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Redclaws on 05/06/2021 03:25 pm
And I'm sure they'd like to prove that the fins can handle high speeds without ripping off. It will be interesting to see how high they'll go and what speeds they can reach on ascent and descent without a full heat shield. But clearly the current profiles they've flown have been much slower than possible profiles that don't shutdown engines. I dont know how the switch to the header tanks prior to shutdown will work with a high speed shutdown of all 3 engines nearly simultaneously.

Yes, it feels to me like there’s a lot of problem space left to explore here.  SpaceX may move pretty quickly on to adding Super Heavy, but between proving it wasn’t a fluke and a lot of other stuff I think they’ve definitely got stuff left they can learn with just starship.  And it’s stuff they absolutely need to learn at some point...  so just a question of how much they do or don’t mix that learning with SH testing, I guess.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: flexbuffchest on 05/06/2021 03:31 pm
What are the reasons for the fire burning at the base of the rocket after landing?

Is it just residual methane trapped under the skirt of the rocket?

Or are fuel valves somehow continuing to leak?

What are the possible remedies for this?

Maybe just some thermal insulation? Idk how long that could burn for but right at about 12:35 in this video you can see what look like some fabric swinging about and on fire in the skirt.

(https://i.imgur.com/Mbz1A0j.png)
https://www.youtube.com/watch?v=z9eoubnO-pE&t=755s
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 05/06/2021 03:40 pm
  Seeing truck carrying the wooden pads take a hard right upon entering launch site, I would suggest that crane is going to unload and head toward pad. The beefy transporter is designed to load a starship without the need of a crane, and it looks like it is ready to go.
  SN15 will be transported and lifted back onto a pad today.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/06/2021 03:43 pm
What are the reasons for the fire burning at the base of the rocket after landing?

Is it just residual methane trapped under the skirt of the rocket?

Or are fuel valves somehow continuing to leak?

What are the possible remedies for this?

Maybe just some thermal insulation? Idk how long that could burn for but right at about 12:35 in this video you can see what look like some fabric swinging about and on fire in the skirt.

(https://i.imgur.com/Mbz1A0j.png)
https://www.youtube.com/watch?v=z9eoubnO-pE&t=755s

My personal theory is that this is a thermal blanket on one of the COPV’s that came off from landing impact.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/06/2021 03:49 pm
What are the reasons for the fire burning at the base of the rocket after landing?

Is it just residual methane trapped under the skirt of the rocket?

Or are fuel valves somehow continuing to leak?

What are the possible remedies for this?

Maybe just some thermal insulation? Idk how long that could burn for but right at about 12:35 in this video you can see what look like some fabric swinging about and on fire in the skirt.

(https://i.imgur.com/Mbz1A0j.png)
https://www.youtube.com/watch?v=z9eoubnO-pE&t=755s

My personal theory is that this is a thermal blanket on one of the COPV’s that came off from landing impact.

I'm thinking it was either the thermal blanket or something to do with how it looked like the landing legs bounced.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 05/06/2021 04:01 pm
My guess is that the pops were from the small COPVs powering the landing leg deploy, which I'm pretty sure I've seen in pictures under the skirt.  Especially if some of the insulation was damaged, the fire and boiloff could have raised the pressure enough to cause a pop.  Once the legs are down they are locked mechanically I believe, so losing the deploy system at that point wouldn't have any effect, as long as the pop didn't release too much energy and damage something else.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/06/2021 04:42 pm
Good flight.
Seems likely there was a Raptor reliability issue again on relight for flip, but otherwise good show from engines.
Were the explosions heard after landing a result of underskirt COPV exploding due to fire heat?
On the wish list: more comprehensive fire suppression system for pad, perhaps a drone fire truck or two to be able to maneuver nozzles under skirt and spray some water or maybe liquid nitrogen on fire source (or would shock chilling like that be bad for engines?)
The pops sounded more like stainless sheet popping, maybe from thermal issues. IMO. Didn't sound concussive or dangerous. We haven't heard it before but we've got new structure.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/06/2021 04:45 pm
Is that something that is expected for a FFSC engine with a cryogenic fuel?

How would you vent or burn off the methane down stream of a shutoff valve?  Maybe it needs to be ducted/vented away.

Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.

I suspect the fairly large volume of liquid Methane contained in the cooling channels of the engine bells is the source of the steady stream of combustible gas we are seeing after various engine shutdown scenarios.

Residual heat would cause this to boil off rapidly and it would need to be vented somewhere or otherwise cause something in the Raptor to rupture...

Does anyone know how they dealed with that on the Shuttle? Or they didn't need to deal with it because only H2 was released?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 05/06/2021 04:46 pm
Is that something that is expected for a FFSC engine with a cryogenic fuel?

How would you vent or burn off the methane down stream of a shutoff valve?  Maybe it needs to be ducted/vented away.

Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.

I suspect the fairly large volume of liquid Methane contained in the cooling channels of the engine bells is the source of the steady stream of combustible gas we are seeing after various engine shutdown scenarios.

Residual heat would cause this to boil off rapidly and it would need to be vented somewhere or otherwise cause something in the Raptor to rupture...

Does anyone know how they dealed with that on the Shuttle? Or they didn't need to deal with it because only H2 was released?

In the shuttle the rs25 engines shutdown in space. So not a big deal there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/06/2021 04:47 pm
Good flight.
Seems likely there was a Raptor reliability issue again on relight for flip, but otherwise good show from engines.
Were the explosions heard after landing a result of underskirt COPV exploding due to fire heat?
On the wish list: more comprehensive fire suppression system for pad, perhaps a drone fire truck or two to be able to maneuver nozzles under skirt and spray some water or maybe liquid nitrogen on fire source (or would shock chilling like that be bad for engines?)

First, the 2 v. 3 engine flip is still being debated. Could very well be a change in the plan to 2-engine flip and landing and John I’s notes were just not updated in time. Second, as for the post-landing “explosions,” I believe those were puddles of liquid CH4 left in the plumbing from engine shutdown spilling out, flashing to vapor in the heat of the local environment and then detonating or conflagrating quickly. The sound was probably amplified by the enclosed area under the skirt and the various berms and vertical tank surfaces around.
The whole SS structure is kind of a boom box. When the workers wail on it with a hammer (what a concept for a rocket) the sound carries quite well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/06/2021 04:51 pm
Nah, Gwynne really is his counterpart in SpaceX. Tory is actually a pretty good sport. He is watching SpaceX eating his company’s lunch, but deep down, he’s a space fan too, the reason he’s where he is. I bet he is watching this as close as we are. Not just as a competitor, but as a space fan as well.
Tory wants to tackle reusability at ULA as well, but the bean counters at Boeing and Lockmart don't want it. I think he is secretly hoping that SpaceX's success will open that door for him and ULA as well.
We had a bean counter as SecDef a while back. It didn't work out so well. Bean counters do best when informing policy, not making it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/06/2021 04:56 pm
I don't see why get why ULA would be opposed to reusable rockets. It's drastically cheaper in the long run.
It runs in the red before it hits the black. Gratification delayed longer than one annual report leaves bean counters grumpy.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/06/2021 04:56 pm
Is that something that is expected for a FFSC engine with a cryogenic fuel?

How would you vent or burn off the methane down stream of a shutoff valve?  Maybe it needs to be ducted/vented away.

Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.

I suspect the fairly large volume of liquid Methane contained in the cooling channels of the engine bells is the source of the steady stream of combustible gas we are seeing after various engine shutdown scenarios.

Residual heat would cause this to boil off rapidly and it would need to be vented somewhere or otherwise cause something in the Raptor to rupture...

Does anyone know how they dealed with that on the Shuttle? Or they didn't need to deal with it because only H2 was released?

In the shuttle the rs25 engines shutdown in space. So not a big deal there.

What about the SLS Core Stage static fires? Space Shuttle too performed some static  fires on the pad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WormPicker959 on 05/06/2021 05:03 pm
Is that something that is expected for a FFSC engine with a cryogenic fuel?

How would you vent or burn off the methane down stream of a shutoff valve?  Maybe it needs to be ducted/vented away.

Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.

I suspect the fairly large volume of liquid Methane contained in the cooling channels of the engine bells is the source of the steady stream of combustible gas we are seeing after various engine shutdown scenarios.

Residual heat would cause this to boil off rapidly and it would need to be vented somewhere or otherwise cause something in the Raptor to rupture...

Does anyone know how they dealed with that on the Shuttle? Or they didn't need to deal with it because only H2 was released?

In the shuttle the rs25 engines shutdown in space. So not a big deal there.

What about the SLS Core Stage static fires? Space Shuttle too performed some static  fires on the pad.

Isn't this what all the sparks are for during shuttle ignition? To burn the H2 before it gathers in too big a cloud?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/06/2021 05:41 pm
Is that something that is expected for a FFSC engine with a cryogenic fuel?

How would you vent or burn off the methane down stream of a shutoff valve?  Maybe it needs to be ducted/vented away.

Will the thin, CO2 based atmosphere on Mars have a suppression effect on any post landing fires on Mars, or is that fire we saw today largely burning off oxygen supplied by the vehicle itself?

Just thinking that if water suppression is used to kill the fire on the landing pad here on Earth, then presumably the CO2 on Mars will naturally duplicate some of that suppression effect.

I think the fire was mostly liquid methane burning off, methane burped out by the engines. If there had been a LOX leak down there I think we would likely have seen a much more intense fire and a SN-10 style explosion.

Mars is a lot closer to vacuum and has only trace amounts of oxygen, so yes, there should be very little (if any) fire.

I suspect the fairly large volume of liquid Methane contained in the cooling channels of the engine bells is the source of the steady stream of combustible gas we are seeing after various engine shutdown scenarios.

Residual heat would cause this to boil off rapidly and it would need to be vented somewhere or otherwise cause something in the Raptor to rupture...

Does anyone know how they dealed with that on the Shuttle? Or they didn't need to deal with it because only H2 was released?

In the shuttle the rs25 engines shutdown in space. So not a big deal there.

What about the SLS Core Stage static fires? Space Shuttle too performed some static  fires on the pad.

Isn't this what all the sparks are for during shuttle ignition? To burn the H2 before it gathers in too big a cloud?

Yes. I completely forgot of that.

Is the skirt a too close space to implement such a system?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 05/06/2021 05:57 pm
On landing?  For SF and engine testing, maybe, although water seems to work as well.  But you'd have to carry the system to use it on landing (weight, power, room, etc.) to keep it in the correct proximity.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: The_Sea_City on 05/06/2021 06:22 pm
I'm very happy to see the rocket didn't explode again during/after landing, but my vote for this landing is C; checklist of things to remove/improve:
- bouncing after landing
- fire on pad after landing
- near-miss of the landing pad
- landing close to to other rockets yet to be launched

Look at  dark footprints of legs and near-miss of the landing pad:
(https://forum.nasaspaceflight.com/assets/53509.0/2031871.jpg)

Feel free to correct if any of this is misleading.

   - bouncing after landing
As Starship neared the landing pad the engine plume was directed out sideways. The black marks are likely form the pads on the bottom of the legs getting blow torched form this. The legs (metal crush types) can only give and not take, like suspension can, so unless the landing burn was perfect bouncing was the only option. As Starship had some horizontal velocity at landing and engine shutdown is not instantanious, it seems reasonable for it to touch and skip (about 3 or 4 feet) in that direction before finally setting down (I say skip but some of the marks seem to be drags, so colour me impressed).

   - fire on pad after landing
Shutting down the engine means cutting the LOX and CH4 to it. If this is done with too much LOX in the mix the LOX will find its own fuel, the metal in the engine, so not good. To avoid this you need to make sure there is an excess of CH4. Given the flow rates for the engines even a small percentage increase of CH4 in the mix would cause a worringly large ammount (for a person standing nearby) of unburnt CH4 to be ejected onto the landing pad. At this point given the temperature in the skirt and the new supply of O2 in the air a fire is going to start. So yes it is expected from this type of engine, and now they have nailed a landing it will be looked at.

   From Herb Schaltegger's post:    « Reply #1368 on: Today at 12:22 pm »
"Second, as for the post-landing “explosions,” I believe those were puddles of liquid CH4 left in the plumbing from engine shutdown spilling out, flashing to vapor in the heat of the local environment and then detonating or conflagrating quickly. The sound was probably amplified by the enclosed area under the skirt and the various berms and vertical tank surfaces around."

   - near-miss of the landing pad
You can't improve your landings until you have managed a landing  :) . While they will want to get nearer to the middle of the landing pad they will also want to focus on removing the horizontal velocity too. This will allow the safe use of legs with
suspension (probably only short term) to remove unintended landing stress for when they test re-use of Starship.

   - landing close to to other rockets yet to be launched
No pain, no gain.  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/06/2021 06:29 pm

Does anyone know how they dealed with that on the Shuttle? Or they didn't need to deal with it because only H2 was released?

While SSME used LH2 and LOX, the RCS and OMS used hypergolic propellants. One of the first jobs after an orbiter landed was to approach it in what looked like biohazard suits (SCAPE suits) with a device that would sense if any of this hypergolic prop was in the air around the vehicle. Only after you confirmed nothing was leaking could others approach without PPE and then the crew could egress
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/06/2021 06:29 pm
Best footage of the flip I've seen:

https://www.reddit.com/r/StarshipDevelopment/comments/n68g32/sn15s_flip_maneuver_during_flight_footage_by/
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 05/06/2021 07:00 pm
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad.
...

I know they plan on catching the booster. Do they also plan to catch Starship? There are no “landing tower” on the Moon or Mars.

I thought Musk tweeted a preference for catching both SS and SH.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dfp21 on 05/06/2021 07:27 pm
We know that F9 lands extremely precisely due to grid fin navigation.
Do we know that reentry to skydive to flip and land can achieve similar performance? Obviously needed if it would be "caught" someday, but still needs to be quite good to hit the pad.
...

I know they plan on catching the booster. Do they also plan to catch Starship? There are no “landing tower” on the Moon or Mars.

I thought Musk tweeted a preference for catching both SS and SH.
Yes Musk recently said, for terrestrial transportation with fast turnaround times he wants to catch the SH 2nd-stage and, with the catcher, place it directly on a previously-caught booster. I guess that's the whole point of the catcher.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GMArnoldi on 05/06/2021 07:33 pm
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/06/2021 07:51 pm
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)

I don’t believe that’s correct. Jack’s photo here shows the feet still firmly on the ground. Looks to me like they are using the trailer as a ground anchor of sorts.

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/06/2021 07:53 pm
https://youtu.be/7IDMM63InLY
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GMArnoldi on 05/06/2021 08:04 pm
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)

I don’t believe that’s correct. Jack’s photo here shows the feet still firmly on the ground. Looks to me like they are using the trailer as a ground anchor of sorts.

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781

The Transporter can rise vertically by at least 50 centimeters allowing the transport of SN15 even with the legs extended. Furthermore, the black beams you see are part of that equipment that has been ready for months for this specific operation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/06/2021 08:07 pm
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)

I don’t believe that’s correct. Jack’s photo here shows the feet still firmly on the ground. Looks to me like they are using the trailer as a ground anchor of sorts.

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781

The Transporter can rise vertically by at least 50 centimeters allowing the transport of SN15 even with the legs extended. Furthermore, the black beams you see are part of that equipment that has been ready for months for this specific operation.

As may be. But the feet in Jack’s phot are still securely pressed to the ground. It’s not going anywhere until the road is closed and the transporter lifts it up, which is not evident from photos yet seen.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/06/2021 08:23 pm
My thoughts regarding the post landing fire:

1. I think source came from the inner side of the skirt, just out of view of the skirt camera. So, it probably wasn't related to a Raptor engine (which is a nice improvement!).

2. Historically, rockets with LOX have vented it. Simple approach that works. Rockets that also have a cryogenic fuel (historically hydrogen, but now methane is coming in), have piped it away to a torch or something similar. That only works on a pad with umbilicals. Starship represents a new development: after a landing, how to vent both without them mixing and causing a big bang. Remember, we've seen what a detonation can do with a previous prototype. How did they deal with this on the DC-X? How has SpaceX dealt with this so far? A windy day and vents far separated might be safer than a calm day and both fuel and oxidizer in close proximity.

3. Assuming the fire was liquid methane, what do you do? I think the use of the water cannons showed that they were trying keep things cool and somewhat contained, but NOT put out the fire (remember: they had more information about the leak). Letting it burn might have bean safer than leaving the fuel to vaporize and then explode.

What do you think?
 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 05/06/2021 08:33 pm
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)

I don’t believe that’s correct. Jack’s photo here shows the feet still firmly on the ground. Looks to me like they are using the trailer as a ground anchor of sorts.

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781 (https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781)


I wonder if the SMPT's have enough room left to lift SN15 up enough so they can fold the legs closed. The wheels look close to full extension but there might be some room left to increase the height.


If they plan on lifting SN15 with crane - we know if it starts crawling closer.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/06/2021 08:35 pm
If in fact liquid methane had come out, I think using water to disperse it would help to boil it off to vapor quickly.  But each CH4 molecule is going to likely burn.

I think there could be a vent out the dorsal side of starship and put an ignition flare on the end.  A controlled burn is preferred of course.

Whether that is the problem, I dunno, never seen a reusable FFSC engine before.

But I do recall they had some fires on the early F9 landings and they were able to get that sorted out.

Now that they were able to land they can start moving on to the next problems on the list.

I curious as to what people think the level of difficulty is for SpaceX to fly and land Superheavy?  Is it a straight forward adaption of their F9 experience?

Venting excess methane post landing is an issue that needs to be sorted for Superheavy as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wheedude on 05/06/2021 08:37 pm
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)

I don’t believe that’s correct. Jack’s photo here shows the feet still firmly on the ground. Looks to me like they are using the trailer as a ground anchor of sorts.

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781

Octagrabber's Big Brother would be my guess
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WindyCity on 05/06/2021 08:58 pm
My thoughts regarding the post landing fire:

1. I think source came from the inner side of the skirt, just out of view of the skirt camera. So, it probably wasn't related to a Raptor engine (which is a nice improvement!).

2. Historically, rockets with LOX have vented it. Simple approach that works. Rockets that also have a cryogenic fuel (historically hydrogen, but now methane is coming in), have piped it away to a torch or something similar. That only works on a pad with umbilicals. Starship represents a new development: after a landing, how to vent both without them mixing and causing a big bang. Remember, we've seen what a detonation can do with a previous prototype. How did they deal with this on the DC-X? How has SpaceX dealt with this so far? A windy day and vents far separated might be safer than a calm day and both fuel and oxidizer in close proximity.

3. Assuming the fire was liquid methane, what do you do? I think the use of the water cannons showed that they were trying keep things cool and somewhat contained, but NOT put out the fire (remember: they had more information about the leak). Letting it burn might have bean safer than leaving the fuel to vaporize and then explode.

What do you think?
 
Could an onboard argon fire suppressant system be employed to put out methane post-shutdown fires? Or would that cause a destructive chilling effect on the hot engines?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/06/2021 09:32 pm
My thoughts regarding the post landing fire:

1. I think source came from the inner side of the skirt, just out of view of the skirt camera. So, it probably wasn't related to a Raptor engine (which is a nice improvement!).

2. Historically, rockets with LOX have vented it. Simple approach that works. Rockets that also have a cryogenic fuel (historically hydrogen, but now methane is coming in), have piped it away to a torch or something similar. That only works on a pad with umbilicals. Starship represents a new development: after a landing, how to vent both without them mixing and causing a big bang. Remember, we've seen what a detonation can do with a previous prototype. How did they deal with this on the DC-X? How has SpaceX dealt with this so far? A windy day and vents far separated might be safer than a calm day and both fuel and oxidizer in close proximity.

3. Assuming the fire was liquid methane, what do you do? I think the use of the water cannons showed that they were trying keep things cool and somewhat contained, but NOT put out the fire (remember: they had more information about the leak). Letting it burn might have bean safer than leaving the fuel to vaporize and then explode.

What do you think?
 
Could an onboard argon fire suppressant system be employed to put out methane post-shutdown fires? Or would that cause a destructive chilling effect on the hot engines?

Why the heck use argon? The thing's already got a decent quantity of cold N2 aboard for its ACS system. They could arrange a series of manifolded vent nozzles under the skirt to purge the area of ambient air and reduce ppO2 for a few minutes at least. It may not prevent combustion of vented methane entirely, but it would definitely keep the flame temps low and help dissipate the methane.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Genial Precis on 05/06/2021 09:53 pm
I think the stopgap for post-landing firefighting is a simple problem--they just need more of it. Plan to completely cover the pad with water and/or liquid nitrogen spray (to displace oxygen) for a few minutes. Eventually they should land on a surface that can drain any liquid methane that should fall out the bottom, and/or catch the Starship (which also provides drainage to keep the fire away from the vehicle).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/06/2021 10:39 pm
Mary got the clearest shot yet of the SH graphic used to label the rings. It appears to have Falcon-style landing legs now. Seems a bit shorter, too.
 
photo credit: bocachicagal

Yes. Some think those legs aren't real, but I fully expect the first few BN's to fly with legs until they can demonstrate sufficient control authority to be caught.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/06/2021 11:23 pm
Now that they were able to land they can start moving on to the next problems on the list.

True, but there's still plenty of space to improve landings.  They can work on getting more centered on the pad, settling out the horizontal velocity to stop/lessen the skidding, and sorting out the flip envelope a little more.  I saw earlier, in some post here, that it's a ~9g flip - don't know how true that is, but that seems a bit excessive for human cargo.  Maybe it's a moot point, anyway, if there are no plans to land a crewed Starship on Earth (what is dearMoon doing)?

Can't wait to see how all of these issues get resolved now that the big hurdle - landing safely - has been cleared.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/06/2021 11:30 pm
I saw earlier, in some post here, that it's a ~9g flip - don't know how true that is, but that seems a bit excessive for human cargo.

I think you misunderstood the 9g, there is no way the flip is a 9g maneuver. (and certainly not for the cargo or crew, since the Starship rotates around the crew/cargo axis)

The only place I've seen 9g mentioned was for the SN10 ground impact.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/07/2021 12:28 am
I saw earlier, in some post here, that it's a ~9g flip - don't know how true that is, but that seems a bit excessive for human cargo.

I think you misunderstood the 9g, there is no way the flip is a 9g maneuver. (and certainly not for the cargo or crew, since the Starship rotates around the crew/cargo axis)

The only place I've seen 9g mentioned was for the SN10 ground impact.

Well, this makes more sense, and makes me feel better about it!  Thanks for the clarification...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Confusador on 05/07/2021 12:50 am
Mary got the clearest shot yet of the SH graphic used to label the rings. It appears to have Falcon-style landing legs now. Seems a bit shorter, too.
 
photo credit: bocachicagal

Yes. Some think those legs aren't real, but I fully expect the first few BN's to fly with legs until they can demonstrate sufficient control authority to be caught.

I agree with you, but I still don't think that *those* legs are anything close to the final design.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/07/2021 03:09 am
My thoughts regarding the post landing fire:

1. I think source came from the inner side of the skirt, just out of view of the skirt camera. So, it probably wasn't related to a Raptor engine (which is a nice improvement!).

2. Historically, rockets with LOX have vented it. Simple approach that works. Rockets that also have a cryogenic fuel (historically hydrogen, but now methane is coming in), have piped it away to a torch or something similar. That only works on a pad with umbilicals. Starship represents a new development: after a landing, how to vent both without them mixing and causing a big bang. Remember, we've seen what a detonation can do with a previous prototype. How did they deal with this on the DC-X? How has SpaceX dealt with this so far? A windy day and vents far separated might be safer than a calm day and both fuel and oxidizer in close proximity.

3. Assuming the fire was liquid methane, what do you do? I think the use of the water cannons showed that they were trying keep things cool and somewhat contained, but NOT put out the fire (remember: they had more information about the leak). Letting it burn might have bean safer than leaving the fuel to vaporize and then explode.

What do you think?
 

Well, when you have hot rocket engines, it would be hard to prevent any venting methane from catching fire.  The vehicle just has to deal with that.  But unless it's a pretty major fire, the heat in that area fust from running the raptors at all will probably be worse.

I suspect a lot of what we're seeing burning is residual fuel left inside the plumbing between the turbopumps and the preburners.  They can't exactly pump it back up the pipes into the fuel tank, and it's a boiling cryogenic liquid and so it has to go *somewhere*.  It could also be hard to get get it down through the preburner and out through the regenerative cooling pipes to the combustion chamber in the context of a shut down engine, so maybe just opening a release valve and letting it drain out (and catch fire) is the simplest thing to do.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sdub on 05/07/2021 03:47 am
The landing fires may only be an issue when landing on Earth at ground level due to the enclosed space under the skirt.  It could potentially be solved by vents and fans in the skirt, presumably on the far side of any O2 venting.  However, if they are going to catch Starship at any kind of elevation then the methane could just disperse in the air.  On the moon and Mars it is probably a non issue due to the low atmospheric pressure and lack of oxidizer. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Ben Baley on 05/07/2021 04:33 am
SN15 anchored to the Transporter and ready for transport.

(Credit RGV AERIAL PHOTOGRAPHY)

I don’t believe that’s correct. Jack’s photo here shows the feet still firmly on the ground. Looks to me like they are using the trailer as a ground anchor of sorts.

https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781 (https://forum.nasaspaceflight.com/index.php?topic=53509.msg2233781#msg2233781)


I wonder if the SMPT's have enough room left to lift SN15 up enough so they can fold the legs closed. The wheels look close to full extension but there might be some room left to increase the height.


If they plan on lifting SN15 with crane - we know if it starts crawling closer.

They built this thing months ago, though some people thought it was for booster transport :o,  and I'm sure they took into account how high they need to lift to stow the legs.

I expect that the crane will be set up at one of the launch stands to lift SN15 onto it so the Raptors can be removed for examination and for easy access to the rest of the vehicle.

Depending on how well SN15 held up it may be relaunched. But if it survives it may be destined for one of those display stands I recall Nomad mentioning.  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sanman on 05/07/2021 04:51 am
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GMArnoldi on 05/07/2021 08:08 am
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?

I wanted to post it a few hours ago but it seemed a bit ridiculous nerdy idea, but I see that I was not the only one to think of it.
I don't know the Octo-grabber mobile fire extinguisher for F9 but on one side of the platform I would see a small armored bunker with a small remote-controlled robot inside equipped with rubber tracks. When a StarShip lands, it starts very fast and as it approaches the ship it unrolls two 3" firefighter-type tubes. It slips under the skirt or slips under two arms and through two or more nozzles pointing upwards it continuously shoots nitrogen at high flow rate and low pressure.
Considering the closed volume in question (relatively small) in a few tens of seconds it would suffocate any non-destructive fire and dilute any methane leakage into the atmosphere.
In this phase of experimentation it would be a huge advantage in the desire to recover the prototypes.
The only drawback I could see is in terms of image. It would suggest that StarShip needs such a system for its survival.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Framryk on 05/07/2021 08:13 am
https://twitter.com/elonmusk/status/1390569345361883136?s=21

How high can they go with a SN15 reflight, taking into account FAA permissions (“suborbital”?), risk analyses, etc? Worth testing beyond 10 km, or just nailing the landing again to prove rapid reusability?  8)

Edit: corrected post night shift spelling  ::)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/07/2021 12:29 pm
https://twitter.com/elonmusk/status/1390569345361883136?s=21

How high can they go with a SN15 reflight, taking into account FAA permissions (“suborbital”?), risk analyses, etc? Worth testing beyond 10 km, or just nailing the landing again to prove rapid reusability?  8)

Edit: corrected post night shift spelling  ::)

They could potentially test supersonic flight. As Elon said, they are barely using the Raptors to lift it to 10km as they could easily blow through the 10km altitude. Testing them at higher power levels and then testing Starship at supersonic speeds can give them valuable data.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Crispy on 05/07/2021 12:44 pm
The in-place FAA approvals are only for this flight plan though, are they not?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: haywoodfloyd on 05/07/2021 12:47 pm
When I first saw the SpaceX video feed I noticed that immediately after touchdown there was something flapping in the engine compartment that looked like a burning blanket of some sort.
You can see it in their feed from roughly the 12:35 point.

https://youtu.be/z9eoubnO-pE

I have no idea what that could be but it seems fairly obvious that that was the source of the fire.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: spacenut on 05/07/2021 12:54 pm
If they can't get the fire problem sorted out, they could have compressed nitrogen or CO2 under the skirt that can spray inside the skirt to force out oxygen and let the residual methane vent without burning.  The small bottles could release their compressed gas immediately upon touchdown if they need it or not.  Like special fire extinguishers mounted inside the skirt. 

Like someone said, they wouldn't need this on the moon or Mars due to either no atmosphere or CO2 atmosphere. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/07/2021 01:00 pm
twitter.com/starshipgazer/status/1390480757890637826 (http://twitter.com/starshipgazer/status/1390480757890637826)
Is it just me, or do the legs look a little crumpled from the landing?  Seems like you can see some creases near the bottom pads. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: haywoodfloyd on 05/07/2021 01:05 pm
twitter.com/starshipgazer/status/1390480757890637826 (http://twitter.com/starshipgazer/status/1390480757890637826)
Is it just me, or do the legs look a little crumpled from the landing?  Seems like you can see some creases near the bottom pads. 

The legs are designed to crumple to absorb landing shock. That's why they have all those holes in them.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: webdan on 05/07/2021 01:06 pm
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?

After reading your post, the first thing that came to mind was a scene from “The Seven Year Itch”.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/07/2021 01:29 pm
Elon thinking SN15 could fly again is really interesting to think about. I think IF it were to happen, we would see it head back to the build site for inspections. Sn16 fly before it, then it would roll back out and do some testing to verify its able, then they might do a Supersonic test of some sort, or just push it to the limits for data.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nebster on 05/07/2021 01:42 pm
Elon thinking SN15 could fly again is really interesting to think about. I think IF it were to happen, we would see it head back to the build site for inspections. Sn16 fly before it, then it would roll back out and do some testing to verify its able, then they might do a Supersonic test of some sort, or just push it to the limits for data.

Not to mention replacement of legs and insulation that burnt up.  But i think you're right.  SN16 flies before SN15 flies again.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SeaRaven on 05/07/2021 02:04 pm
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?

After reading your post, the first thing that came to mind was a scene from “The Seven Year Itch”.


Unfortunately water does not put out gas fires.  The hosing was likely to keep the skirt relatively cool.  You'd need a C02 or  N2 extinguisher for that.  Plenty of N2 around, so a remote guided fire truck with a big tank of nice cool liquid N2 might do the trick.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 05/07/2021 02:07 pm
The legs are designed to crumple to absorb landing shock. That's why they have all those holes in them.

And note how the hole size decreases, so you get more and more resistance to crumpling as the leg gets shorter.  It's designed for smooth deceleration.

It is really impressive how little of that crush margin they used: only the first hole on both segments.  That was a very soft landing.

FWIW, the F9 landing legs use a similar crush system to absorb landing shock. I believe F9 legs contain a crushable honeycomb, rather than the "beam with holes" design here, but the basic idea is the same.  The crushable part is replaceable when the crush margin is "used up" -- these SS legs look they could easily have another landing left in them, but I bet they'll be replaced if SN15 reflies.  I think the F9 honeycombs are replaced for every flight as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SeaRaven on 05/07/2021 02:13 pm
Elon thinking SN15 could fly again is really interesting to think about. I think IF it were to happen, we would see it head back to the build site for inspections. Sn16 fly before it, then it would roll back out and do some testing to verify its able, then they might do a Supersonic test of some sort, or just push it to the limits for data.

Not to mention replacement of legs and insulation that burnt up.  But i think you're right.  SN16 flies before SN15 flies again.

I'm surprised they don't use Nomex blankets instead of what seems to be Reynolds Wrap.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/07/2021 02:33 pm
Scott Manley, in his last video, said that "sources that are NOT public said him " that sn16 will fly in a couple of weeks, so we  can expect that they rollout it ASAP.

BTW, is the SN15 the first rollback of a full scale Starship with aerodinamics controls?


edit: corrected misspelled Scott's name
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Moritz Kibler on 05/07/2021 02:40 pm
Scott Manly, in his last video, said that "sources that are NOT public said him " that sn16 will fly in a couple of weeks, so we  can expect that they rollout it ASAP.

BTW, is the SN15 the first rollback of a full scale Starship with aerodinamics controls?

SN16 will roll out pretty soon I think. It now has both aft flaps and they seem to be finishing up work in the High Bay.

And yes SN15 is the first recovered full scale Starship prototye.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SkyRate on 05/07/2021 03:20 pm
Elon thinking SN15 could fly again is really interesting to think about. I think IF it were to happen, we would see it head back to the build site for inspections. Sn16 fly before it, then it would roll back out and do some testing to verify its able, then they might do a Supersonic test of some sort, or just push it to the limits for data.
They must be really interested to see how welds and the rest of the structure handled the landing. I expect a throrough round of PT+RT tests and then pressure tests before any reflight attempt.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/07/2021 03:46 pm
Well, I’ll just leave this here.

https://twitter.com/octagrabber/status/1390076462997377024

Said this about 30 minutes after landing
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/07/2021 07:46 pm
Elon thinking SN15 could fly again is really interesting to think about. I think IF it were to happen, we would see it head back to the build site for inspections. Sn16 fly before it, then it would roll back out and do some testing to verify its able, then they might do a Supersonic test of some sort, or just push it to the limits for data.
They must be really interested to see how welds and the rest of the structure handled the landing. I expect a throrough round of PT+RT tests and then pressure tests before any reflight attempt.

If the quick look at the pad doesn’t look too bad, I wouldn’t be surprised if they took it back to a launch stand for inspections. They can do lots of testing there including pressure tests, and remove raptors easily if needed. That would also save another move. Not sure they’d worry about weld tests. They can always do pressure tests and see how those go.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rock1 on 05/07/2021 08:25 pm

What's the intention with now placing SN15 in the center of the landing pad? Would have thought moving it to pad A or B or back to production site would be much more likely. Was it really in the way where it landed, it was actually ON the landing pad.. :o
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/07/2021 08:52 pm

What's the intention with now placing SN15 in the center of the landing pad? Would have thought moving it to pad A or B or back to production site would be much more likely. Was it really in the way where it landed, it was actually ON the landing pad.. :o
I don't think it's been "placed" there, they've just stopped for now.  I expect them to either continue to a crane's reach from one of the suborbital pads, or to take it for a drive to the build site.  I'd guess the former, but the latter wouldn't surprise me either.  If it is going back on the pad, I could see them swapping out the legs while its still on the transporter - seems like it'd be easier to do closer to the ground.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StevenOBrien on 05/07/2021 09:23 pm

What's the intention with now placing SN15 in the center of the landing pad? Would have thought moving it to pad A or B or back to production site would be much more likely. Was it really in the way where it landed, it was actually ON the landing pad.. :o
It landed right at the edge of the landing pad, so it might have made it easier for them to work with it if it was in a more central location, with the SPMTs/equipment out of the dirt, etc.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BT52 on 05/07/2021 09:35 pm

What's the intention with now placing SN15 in the center of the landing pad? Would have thought moving it to pad A or B or back to production site would be much more likely. Was it really in the way where it landed, it was actually ON the landing pad.. :o

Maybe is Starship sentient being. Like u put toddler on right place "sit there".  :P Machine learning for landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/07/2021 09:56 pm
And they've removed the legs ... if we see them bring out replacements, I'd say that's a slam dunk they're going to try to re-fly, otherwise, they'd just head back to the build site.

https://twitter.com/bottinphilip/status/1390774482445475841

Quote
Looks like all the legs have been removed from #SN15
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/07/2021 10:58 pm
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?

I wanted to post it a few hours ago but it seemed a bit ridiculous nerdy idea, but I see that I was not the only one to think of it.
I don't know the Octo-grabber mobile fire extinguisher for F9 but on one side of the platform I would see a small armored bunker with a small remote-controlled robot inside equipped with rubber tracks. When a StarShip lands, it starts very fast and as it approaches the ship it unrolls two 3" firefighter-type tubes. It slips under the skirt or slips under two arms and through two or more nozzles pointing upwards it continuously shoots nitrogen at high flow rate and low pressure.
Considering the closed volume in question (relatively small) in a few tens of seconds it would suffocate any non-destructive fire and dilute any methane leakage into the atmosphere.
In this phase of experimentation it would be a huge advantage in the desire to recover the prototypes.
The only drawback I could see is in terms of image. It would suggest that StarShip needs such a system for its survival.

False economy.   No need for it.   SX is iterating too fast.

SS Prototypes have proven they can withstand plenty of fire.  If it's not going to survive a leak-generated fire, it's probably not going to be put out by a Robot Fireman.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alastairmayer on 05/08/2021 12:22 am
And they've removed the legs ... if we see them bring out replacements, I'd say that's a slam dunk they're going to try to re-fly, otherwise, they'd just head back to the build site.

https://twitter.com/bottinphilip/status/1390774482445475841

Quote
Looks like all the legs have been removed from #SN15

They almost certainly need to remove the legs for transport -- they're a bit too bent to fold back up.

If they do bring out fresh legs, well then....
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: 50_Caliber on 05/08/2021 02:52 am
After watching several SS flights, I have noticed the distinctive note that those Raptors make while firing under the starship. Many of us have probably put a firecracker under a metallic can and then you hear that ring sound from the explosion. That's kind of what it sounds like -except it's continuous. It makes a distinctive noise-in-a-can sound as it flies, I don't think I've heard any rocket with such a unique sound when it is firing it's engines.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 05/08/2021 03:43 am
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?

I wanted to post it a few hours ago but it seemed a bit ridiculous nerdy idea, but I see that I was not the only one to think of it.
I don't know the Octo-grabber mobile fire extinguisher for F9 but on one side of the platform I would see a small armored bunker with a small remote-controlled robot inside equipped with rubber tracks. When a StarShip lands, it starts very fast and as it approaches the ship it unrolls two 3" firefighter-type tubes. It slips under the skirt or slips under two arms and through two or more nozzles pointing upwards it continuously shoots nitrogen at high flow rate and low pressure.
Considering the closed volume in question (relatively small) in a few tens of seconds it would suffocate any non-destructive fire and dilute any methane leakage into the atmosphere.
In this phase of experimentation it would be a huge advantage in the desire to recover the prototypes.
The only drawback I could see is in terms of image. It would suggest that StarShip needs such a system for its survival.

False economy.   No need for it.   SX is iterating too fast.

SS Prototypes have proven they can withstand plenty of fire.  If it's not going to survive a leak-generated fire, it's probably not going to be put out by a Robot Fireman.
Whilst I agree with the reasons as to why not, if you did have such a machine I would have a few tweaks… metal (fireproof) wheels as it will be operating purely on a smooth concrete surface, and small enough to go under the skirt (simpler).

Drive under, open nitrogen/whatever gas valve, wait.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aip on 05/08/2021 07:39 am
Unfortunately water does not put out gas fires.  The hosing was likely to keep the skirt relatively cool.  You'd need a C02 or  N2 extinguisher for that.  Plenty of N2 around, so a remote guided fire truck with a big tank of nice cool liquid N2 might do the trick.
Unfortunately a high-volume liquid N2 robot would more appropriate in the Terminator franchise. One accidental discharge during testing and the tech is, um, very cold toast. It would need lock-out and arming procedures, as well as training for everyone that works nearby, similar to halon training (also an oxygen displacer used for fire suppression).

I'll go out on a (very stout) limb and guess that before moving on to complicated new solutions, SpaceX will start simple and try to just not drop anything flammable on the ground after landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/08/2021 08:03 am
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: V96 on 05/08/2021 08:30 am
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/08/2021 11:08 am
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Starship doesn’t have solar panels on its outer surface like Dragon. If it can’t deploy solar panels, no way to make more power so you’re limited to time by the charge in the batteries you’ve got.

Shuttle had huge delta wings to give it the cross range to land back at the (never used) polar launch site after only one orbit, and Starships flaps are nowhere near as big compared to vehicle size, so my guess is it’s cross range is not as large.

So this tells me they won’t be able to land back at the launch site with these early prototypes unless solar power is implemented. They have to wait for their orbit’s ground track to get close to Boca Chica but don’t have the power to wait that long. Plus landing around populated areas....

So I don’t think SN20 will land at Boca Chica. Maybe deorbit it somewhere in the ocean before power runs out and you’d lose control. Lots of hand waving to say a few orbits, maybe not even a full one.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jpo234 on 05/08/2021 11:17 am
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.
There is no way they get FAA approval to reenter over the US mainland (if they even wanted to do that) with an early prototype. And they won't get approval to launch retrograde for the same reason.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 05/08/2021 11:21 am
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jpo234 on 05/08/2021 11:24 am
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.
That wouldn't test anything. There is a reason New Shepard doesn't need thermal protection.

Orbit means going really fast sideways relative to the earth surface. This is the kinetic energy that a vehicle has to shed during EDL and this is what they have to test.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: lykos on 05/08/2021 11:28 am
They have no solar panels because they don't need them (now).
When they will need them, they will have them, no big deal.
Besides there is surely enough cargo space for plenty of batteries.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 05/08/2021 11:33 am
That wouldn't test anything. There is a reason New Shepard doesn't need thermal protection.

Orbit means going really fast sideways relative to the earth surface. This is the kinetic energy that a vehicle has to shed during EDL and this is what they have to test.

NS barely gets above 100 km.  I'm talking about flying out essentially vertically several thousand miles, turning around, and re-entering at whatever entry speed you want.  The profile wouldn't be perfect due to the angle of entry, but you could still get a lot of data and the chance to test the "DL" part of EDL as well.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tesh90 on 05/08/2021 12:06 pm
Apologies if this has been asked up-thread but is there any need to finish building SN17?
   1. (If) SN15 re-flies
   2. Either way, SN16 is there to finish off the "SN15-19" test regime

They could just wait till there's a need before stacking....

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rock1 on 05/08/2021 12:28 pm

Concerning the upcoming orbital tests with the combined booster and Starship, why are SpaceX buying up oil-platforms? Are they only meant for launches, they could be used as landing platforms in the ocean for Starship during the testing with SN20+ ? As long as  SX have developed enough confidence from the pre SN20 landings that they can make successful landings on them. The landing platform at Boca Chica is square and about the same size, coincidence or not?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/08/2021 12:33 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.

I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy; second, to demonstrate orbital flight for NASA HLS folks, perhaps even tick off some technical milestones required by the contract; third, to rub the fact that while BO still hasn’t orbited an ounce of payload, SpaceX has well over a hundred successful Falcon missions plus have developed a brand new, giant launch system entirely without government funding into the eye of the GAO as they evaluate Blue’s absurd HLS contract challenge. You’ll note that that HLS Lunar Starship does not have to survive Earth orbit EDL. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ugordan on 05/08/2021 12:54 pm
I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy;

This has probably been discussed somewhere already so apologies for not keeping tabs on every single Starship thread, but how does one weigh the benefits of a fully orbital injection (as opposed to very slightly suborbital one, like Shuttle ET) vs. the risk of leaving a huge, stainless steel object in LEO waiting for an uncontrolled entry if the deorbit burn fails for whatever reason?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/08/2021 01:01 pm

I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy; second, to demonstrate orbital flight for NASA HLS folks....


While I agree getting SuperHeavy data is important, you don’t need an orbit-capable StarShip on top to get that. A nose cone with the right weight and outer mold line would get them the same information, but we all know that isn’t the way this company works. Why spend the time and effort to develop a one-time nosecone when you could just put a vehicle on top

So if you’re going to put a real vehicle on top of superheavy, what is the most useful way to spend your time and money? You retire the largest risks and gain information that is necessary for future development. Two places they don’t have good information so far are on performance of their thermal protection system and aero dynamic control during hyper sonic flight of this vehicle. What are the minimum requirements of a vehicle that demonstrates these features and that gives them information to validate their models

There’s also one other reason they want to put a vehicle on top and get it into orbit quickly, they just want to get [expletive] done
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 05/08/2021 01:06 pm
I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy;

This has probably been discussed somewhere already so apologies for not keeping tabs on every single Starship thread, but how does one weigh the benefits of a fully orbital injection (as opposed to very slightly suborbital one, like Shuttle ET) vs. the risk of leaving a huge, stainless steel object in LEO waiting for an uncontrolled entry if the deorbit burn fails for whatever reason?

A very timely question given the probable Chinese space station booster uncontrolled reentry thus weekend
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 05/08/2021 01:42 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Starship doesn’t have solar panels on its outer surface like Dragon. If it can’t deploy solar panels, no way to make more power so you’re limited to time by the charge in the batteries you’ve got.

Shuttle had huge delta wings to give it the cross range to land back at the (never used) polar launch site after only one orbit, and Starships flaps are nowhere near as big compared to vehicle size, so my guess is it’s cross range is not as large.

So this tells me they won’t be able to land back at the launch site with these early prototypes unless solar power is implemented. They have to wait for their orbit’s ground track to get close to Boca Chica but don’t have the power to wait that long. Plus landing around populated areas....

So I don’t think SN20 will land at Boca Chica. Maybe deorbit it somewhere in the ocean before power runs out and you’d lose control. Lots of hand waving to say a few orbits, maybe not even a full one.
In an emergency, Starship can probably land in a large level car park or similar area. 

So whilst this would be (put mildly) undesirable, it does suggest that cross range capability is not too important when compared to Shuttle.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/08/2021 01:48 pm
Apologies if this has been asked up-thread but is there any need to finish building SN17?
   1. (If) SN15 re-flies
   2. Either way, SN16 is there to finish off the "SN15-19" test regime

They could just wait till there's a need before stacking....
1) Gain more build experience.
2) Provide a chance to implement and test minor tweaks prior to the jump to SN20
2a) While we assume these vehicles to be roughly identical, nobody here actually knows that, or if they do, they're not talking.  They could all be subtly different testing slightly different ways of doing things.

I had a couple more in mind as I was writing this, but they got away.  I need coffee.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 05/08/2021 02:05 pm
I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy;

This has probably been discussed somewhere already so apologies for not keeping tabs on every single Starship thread, but how does one weigh the benefits of a fully orbital injection (as opposed to very slightly suborbital one, like Shuttle ET) vs. the risk of leaving a huge, stainless steel object in LEO waiting for an uncontrolled entry if the deorbit burn fails for whatever reason?

Discussed in the thread Uncontrolled reentry considerations with early Starship orbital test flights (https://forum.nasaspaceflight.com/index.php?topic=53388.0)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 05/08/2021 02:14 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.

I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy; second, to demonstrate orbital flight for NASA HLS folks, perhaps even tick off some technical milestones required by the contract; third, to rub the fact that while BO still hasn’t orbited an ounce of payload, SpaceX has well over a hundred successful Falcon missions plus have developed a brand new, giant launch system entirely without government funding into the eye of the GAO as they evaluate Blue’s absurd HLS contract challenge. You’ll note that that HLS Lunar Starship does not have to survive Earth orbit EDL.

I doubt HLS protest is a major consideration in terms of Starship schedule, I think the reasons for early orbital flights are:
1. Milestone payment: Besides HLS, there may also be milestone payment from MZ/DearMoon contract
2. Make Starship more real: HLS award kind of already did this but I think SpaceX's ambition for Starship goes well beyond HLS, there're other potential government and commercial contracts to go after, and a successful orbital flight would help a lot with the credibility of their other proposals.
3. Make Starship pay for itself: They can start launching Starlink and rideshares once Starship can reach orbit, this would allow them to get some money back while testing EDL.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 05/08/2021 02:29 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.

I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy; second, to demonstrate orbital flight for NASA HLS folks, perhaps even tick off some technical milestones required by the contract; third, to rub the fact that while BO still hasn’t orbited an ounce of payload, SpaceX has well over a hundred successful Falcon missions plus have developed a brand new, giant launch system entirely without government funding into the eye of the GAO as they evaluate Blue’s absurd HLS contract challenge. You’ll note that that HLS Lunar Starship does not have to survive Earth orbit EDL.

I doubt HLS protest is a major consideration in terms of Starship schedule, I think the reasons for early orbital flights are:
1. Milestone payment: Besides HLS, there may also be milestone payment from MZ/DearMoon contract
2. Make Starship more real: HLS award kind of already did this but I think SpaceX's ambition for Starship goes well beyond HLS, there're other potential government and commercial contracts to go after, and a successful orbital flight would help a lot with the credibility of their other proposals.
3. Make Starship pay for itself: They can start launching Starlink and rideshares once Starship can reach orbit, this would allow them to get some money back while testing EDL.

For me orbital is needed as soon as possible.
Suddenly all the remaining tech testing can be done in parallel.
1. Heat shield testing
2. Orbital reentry with flaps and angle of attach testing.
3. In space refueling
4. Chomper for payload deploy
5. Survival in space to perform the above. Batteries, Solar.
6. Current legs or better legs for landing
7. Booster testing in real world use. Return and catch.
8. etc
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/08/2021 02:34 pm
Apologies if this has been asked up-thread but is there any need to finish building SN17?
   1. (If) SN15 re-flies
   2. Either way, SN16 is there to finish off the "SN15-19" test regime

They could just wait till there's a need before stacking....

Because sn17 will probably have a full TPS.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/08/2021 02:45 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.

I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy; second, to demonstrate orbital flight for NASA HLS folks, perhaps even tick off some technical milestones required by the contract; third, to rub the fact that while BO still hasn’t orbited an ounce of payload, SpaceX has well over a hundred successful Falcon missions plus have developed a brand new, giant launch system entirely without government funding into the eye of the GAO as they evaluate Blue’s absurd HLS contract challenge. You’ll note that that HLS Lunar Starship does not have to survive Earth orbit EDL.

3. Make Starship pay for itself: They can start launching Starlink and rideshares once Starship can reach orbit, this would allow them to get some money back while testing EDL.

The cargo bay is an important part, and IMO it isn't so easy to design. So IMO they won't fly payload for the first flights. In the nosecone tent IIRC nothing like a prototype of the cargo bay doors has been seen.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/08/2021 02:50 pm
SN17 mid-LOX section ready to be stacked.

In the post there is an image of the big patch of tiles on sn17. There are in the lower part some tiles that are already broken. Did I see correctly?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kazioo on 05/08/2021 03:21 pm
TPS tiles are brittle, so theoretically they should be attached after the vehicle is fully stacked and welded.
This however slows down the production, because they can put TPS more efficiently in a modular manner. It's probably more effective to just ignore the problem and replace those damaged ones later.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/08/2021 03:22 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Starship doesn’t have solar panels on its outer surface like Dragon. If it can’t deploy solar panels, no way to make more power so you’re limited to time by the charge in the batteries you’ve got.

Shuttle had huge delta wings to give it the cross range to land back at the (never used) polar launch site after only one orbit, and Starships flaps are nowhere near as big compared to vehicle size, so my guess is it’s cross range is not as large.

So this tells me they won’t be able to land back at the launch site with these early prototypes unless solar power is implemented. They have to wait for their orbit’s ground track to get close to Boca Chica but don’t have the power to wait that long. Plus landing around populated areas....

So I don’t think SN20 will land at Boca Chica. Maybe deorbit it somewhere in the ocean before power runs out and you’d lose control. Lots of hand waving to say a few orbits, maybe not even a full one.
How much battery do you really need to coast in orbit?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/08/2021 03:45 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Starship doesn’t have solar panels on its outer surface like Dragon. If it can’t deploy solar panels, no way to make more power so you’re limited to time by the charge in the batteries you’ve got.

Shuttle had huge delta wings to give it the cross range to land back at the (never used) polar launch site after only one orbit, and Starships flaps are nowhere near as big compared to vehicle size, so my guess is it’s cross range is not as large.

So this tells me they won’t be able to land back at the launch site with these early prototypes unless solar power is implemented. They have to wait for their orbit’s ground track to get close to Boca Chica but don’t have the power to wait that long. Plus landing around populated areas....

So I don’t think SN20 will land at Boca Chica. Maybe deorbit it somewhere in the ocean before power runs out and you’d lose control. Lots of hand waving to say a few orbits, maybe not even a full one.
I think your right about not landing at BC, but for the wrong reason. Batteries are a resource SX has good access to and a large cargo bay to put them in.


A traditional EDL has SS overflying populated areas. Unless, unless...


There is that question of cross range. This is beyond a long shot but SX has a habit of pulling rabbits out of hats. If SS were to overshoot as if landing in the Gulf, is there any way it could kill off enough horizontal V high enough up that it could work it's way back?


Maybe by doing reentry as shallow as possible and killing off more horizontal and less vertical V. What does hypersonic do to glide ratios?


This is offered up from a deep well of "I barely know what I'm talking about."



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/08/2021 03:50 pm
That wouldn't test anything. There is a reason New Shepard doesn't need thermal protection.

Orbit means going really fast sideways relative to the earth surface. This is the kinetic energy that a vehicle has to shed during EDL and this is what they have to test.

NS barely gets above 100 km.  I'm talking about flying out essentially vertically several thousand miles, turning around, and re-entering at whatever entry speed you want.  The profile wouldn't be perfect due to the angle of entry, but you could still get a lot of data and the chance to test the "DL" part of EDL as well.
The calcs that some NSF'ers have run say they can get reentry temps this way but not duration. Or they can get the duration, but not the temps. Sounds testwothy to me.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/08/2021 04:10 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Why do the first "orbital" flights have to really achieve orbit?  I would expect the early flights are going to be testing EDL parts of the operating envelope, so why couldn't they do that on a sub-orbital flight?  Fly up, RTLS back over the gulf in case things go wrong, land back at BC if everything goes right.

I think the reasons they are pushing for an early orbital test flight are first, to get meaningful some flight experience with the Super Heavy; second, to demonstrate orbital flight for NASA HLS folks, perhaps even tick off some technical milestones required by the contract; third, to rub the fact that while BO still hasn’t orbited an ounce of payload, SpaceX has well over a hundred successful Falcon missions plus have developed a brand new, giant launch system entirely without government funding into the eye of the GAO as they evaluate Blue’s absurd HLS contract challenge. You’ll note that that HLS Lunar Starship does not have to survive Earth orbit EDL.

3. Make Starship pay for itself: They can start launching Starlink and rideshares once Starship can reach orbit, this would allow them to get some money back while testing EDL.

The cargo bay is an important part, and IMO it isn't so easy to design. So IMO they won't fly payload for the first flights. In the nosecone tent IIRC nothing like a prototype of the cargo bay doors has been seen.
The nosecone torture rack might be a hint.  Characterizing a plain nosecone before designing something that opens seems reasonable. And I'm still not convinced the chomper is the best design.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 05/08/2021 04:44 pm
3. Make Starship pay for itself: They can start launching Starlink and rideshares once Starship can reach orbit, this would allow them to get some money back while testing EDL.

The cargo bay is an important part, and IMO it isn't so easy to design. So IMO they won't fly payload for the first flights. In the nosecone tent IIRC nothing like a prototype of the cargo bay doors has been seen.

If they limit payload to smallsat and cubesat, they don't need a gigantic cargo bay door, just a small door maybe a meter across would be sufficient. If they can figure out a way to eject Starlink sideways one by one, it doesn't need a big opening either, sideways the satellite is only about 2m wide and a few tens of centimeters high.

If there's one thing we learned from watching these prototypes, it's that SpaceX is not aiming at the perfect design from the get go, they're happy to use temporary solutions such as the single use crashable legs as long as it moves the program forward.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 05/08/2021 04:50 pm
Just like Octo-grabber for F9, why can't they just have some mobile fire extinguisher robot that will scoot in following touchdown and immediately start hosing down the interior under the skirt?

I wanted to post it a few hours ago but it seemed a bit ridiculous nerdy idea, but I see that I was not the only one to think of it.
I don't know the Octo-grabber mobile fire extinguisher for F9 but on one side of the platform I would see a small armored bunker with a small remote-controlled robot inside equipped with rubber tracks. When a StarShip lands, it starts very fast and as it approaches the ship it unrolls two 3" firefighter-type tubes. It slips under the skirt or slips under two arms and through two or more nozzles pointing upwards it continuously shoots nitrogen at high flow rate and low pressure.
Considering the closed volume in question (relatively small) in a few tens of seconds it would suffocate any non-destructive fire and dilute any methane leakage into the atmosphere.
In this phase of experimentation it would be a huge advantage in the desire to recover the prototypes.
The only drawback I could see is in terms of image. It would suggest that StarShip needs such a system for its survival.

False economy.   No need for it.   SX is iterating too fast.

SS Prototypes have proven they can withstand plenty of fire.  If it's not going to survive a leak-generated fire, it's probably not going to be put out by a Robot Fireman.
Whilst I agree with the reasons as to why not, if you did have such a machine I would have a few tweaks… metal (fireproof) wheels as it will be operating purely on a smooth concrete surface, and small enough to go under the skirt (simpler).

Drive under, open nitrogen/whatever gas valve, wait.

At that point you could just outfit the pad with a grid of embedded N2 nozzles and pipe in the nitrogen whereever the bird landed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 05/08/2021 04:52 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Starship doesn’t have solar panels on its outer surface like Dragon. If it can’t deploy solar panels, no way to make more power so you’re limited to time by the charge in the batteries you’ve got.

Shuttle had huge delta wings to give it the cross range to land back at the (never used) polar launch site after only one orbit, and Starships flaps are nowhere near as big compared to vehicle size, so my guess is it’s cross range is not as large.

So this tells me they won’t be able to land back at the launch site with these early prototypes unless solar power is implemented. They have to wait for their orbit’s ground track to get close to Boca Chica but don’t have the power to wait that long. Plus landing around populated areas....

So I don’t think SN20 will land at Boca Chica. Maybe deorbit it somewhere in the ocean before power runs out and you’d lose control. Lots of hand waving to say a few orbits, maybe not even a full one.
How much battery do you really need to coast in orbit?

Shouldn't need much battery, Falcon 9 S2 can already coast for 6 hours at least, Centaur can coast for one to three days with additional battery. And they should be able to add solar array fairly easily, either use Dragon 2's conformal array or Starlink's extendable solar array, the arrays do not need to be reusable, it can be single use (either allowed to burn/melt or just eject before re-entry) like the current legs.

But FAA safety considerations probably wouldn't allow landing back at Boca Chica initially, ocean landing on the west coast droneship is more likely.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/08/2021 05:00 pm
With sn20 and the integration tower getting built the otìrbital flightd feels closer every day.

How long do you expect the orbital flight to be? How much time spent in orbit could demostrate well starship's capabilities?

Takes a few orbits to get back to Starbase. Some small multiple of 90 minutes.

Starship doesn’t have solar panels on its outer surface like Dragon. If it can’t deploy solar panels, no way to make more power so you’re limited to time by the charge in the batteries you’ve got.

Shuttle had huge delta wings to give it the cross range to land back at the (never used) polar launch site after only one orbit, and Starships flaps are nowhere near as big compared to vehicle size, so my guess is it’s cross range is not as large.

So this tells me they won’t be able to land back at the launch site with these early prototypes unless solar power is implemented. They have to wait for their orbit’s ground track to get close to Boca Chica but don’t have the power to wait that long. Plus landing around populated areas....

So I don’t think SN20 will land at Boca Chica. Maybe deorbit it somewhere in the ocean before power runs out and you’d lose control. Lots of hand waving to say a few orbits, maybe not even a full one.
How much battery do you really need to coast in orbit?

Shouldn't need much battery, Falcon 9 S2 can already coast for 6 hours at least, Centaur can coast for one to three days with additional battery. And they should be able to add solar array fairly easily, either use Dragon 2's conformal array or Starlink's extendable solar array, the arrays do not need to be reusable, it can be single use (either allowed to burn/melt or just eject before re-entry) like the current legs.

But FAA safety considerations probably wouldn't allow landing back at Boca Chica initially, ocean landing on the west coast droneship is more likely.
Yeah that was my point.

Agreed that overflight permission is the main hurdle.

Longevity of upper stages is a red herring, it was salient with old EELV stages, it's a non-issue for Starship.

And FWIW, STS return to land wasn't in order to save battery mass either.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mclumber1 on 05/08/2021 05:20 pm
Another option to land SN20 (or whichever is the first SN to make it to orbit) would the be the west coast landing facility at Vandenberg.  The landing pad appears to be about 250 feet in diameter, which is quite a bit more generous than any of the ASDSs in service (or being built). 

Punching a hole in the landing pad is probably cheaper than punching a hole through one of the landing barges as well.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Surfdaddy on 05/08/2021 05:24 pm
There is no way you are really going to test the heat shield or reentry profile properly unless you get up to orbital velocities. Suborbital won't do it.

I would assume that a deorbit burn is a pretty low risk operation given that we've been doing that on stages for a long time. For EDL, Boca seems too risky for a while until a design is proven. This opens an interesting problem: Huge Starships, either dumped into ocean with lots of Raptors, or stuck on a barge and they are not that easy to move around. Can't exactly see a Starship on Interstate 10 from Long Beach to Texas...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/08/2021 05:34 pm

Shouldn't need much battery, Falcon 9 S2 can already coast for 6 hours at least, Centaur can coast for one to three days with additional battery.

Do they need to a actively chill the prop while on orbit? If you’re up there for a few days waiting for your ground track to intersect a landing site, that’s different than using a hypergolic RCS for deorbit
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mclumber1 on 05/08/2021 05:38 pm

Shouldn't need much battery, Falcon 9 S2 can already coast for 6 hours at least, Centaur can coast for one to three days with additional battery.

Do they need to a actively chill the prop while on orbit? If you’re up there for a few days waiting for your ground track to intersect a landing site, that’s different than using a hypergolic RCS for deorbit

Starship should have some cross-range capability I would think.  Maybe not as good as the shuttle, but probably better than a capsule design.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ugordan on 05/08/2021 05:45 pm
There is no way you are really going to test the heat shield or reentry profile properly unless you get up to orbital velocities. Suborbital won't do it.

Something like 50-100 m/s short of orbital velocity doesn't exactly qualitatively change the reentry profile. In fact, it probably precisely mimics it once the deorbit burn is done. Shuttle ETs didn't go orbital, but they were barely short of orbital and were guaranteed to splash down into a safe area.

I would assume that a deorbit burn is a pretty low risk operation given that we've been doing that on stages for a long time.

Kind of a weird assumption, considering how every new piece of hardware developed has its own quirks and issues. That's sort of like saying F9 reentry and landing burns have not failed for a long time so Raptor relight should be low risk, too. Except Raptor restarts, sort of... didn't always work and not reliably. And no, don't throw the upgraded Raptor argument in here, there may yet be more lessons to be learned and uncertainties to close.
Considering we have no info on methalox thruster development, it only stands to reason to expect a deorbit burn to be done by the main propulsion system - in the near future at least.

The question of a safe deorbit should not be swept away as a non-issue, IMHO.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nomadd on 05/08/2021 06:22 pm
How much battery do you really need to coast in orbit?
Probably negligible compared to power needed for flaps and gimble pumps.
 Old pre-nose SNs had a 85kwh or so battery on top. New SNs might have more since they have flap motors to drive.
 One ton batteries are up to something like 300kwh now. (cell weight)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: bstrong on 05/08/2021 06:35 pm
The question of a safe deorbit should not be swept away as a non-issue, IMHO.

Strongly agree with this. Starship has roughly the same mass as Mir. It's probably actually more including landing prop, so it will likely be the most massive man-made object to reenter EVER, and if something goes wrong, it would definitely be the largest uncontrolled reentry by a large margin.

Considering the current international uproar over the uncontrolled reentry of an object 25% the mass of Starship, I'm expecting this to get a ton of scrutiny. A Shuttle external tank trajectory seems like a no-brainer for test flights.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/08/2021 06:56 pm
Having read the lastest post I propose an orbital trajector thet seems to me safe enough to be appruved.

1) inject SS in a suborbital slightly suborbital trajectory, like the E.T. of the Shuttle, that in case of no action will bring starship to crash/land (depending if the landing is attempted) over a large unhabitated area, such as Pacific.
2) at apogee, if everything works, do a burn to inject starship in orbit, at a safe altitude to not reenter if not in a lot of years, enough to send another ship to dispose of it  in case something  goes wrong.

3) after a couple of orbit deorbit the SS, targeting ashore of Vandemberg.
4) after reentry land it in LZ-4
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/08/2021 08:47 pm
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Noise may be a particular issue. 
When NASA ordered an environmental assessment for Starship landing at LC-39A (link here (https://netspublic.grc.nasa.gov/main/20190919_Final_EA_SpaceX_Starship.pdf)), the predicted sonic boom map showed a significant amount of sonic boom noise up to ~30 miles West of the landing site, as shown by the yellow line in the first image below. Specifically, the sonic boom assessment states:
Quote
In general, booms in the 0.2 to 0.3 psf range could be heard by someone who is expecting it and listening for it, but usually would not be noticed. Booms of 0.5 psf are more likely to be noticed, and booms of 1.0 psf are certain to be noticed. Therefore, people west of KSC are likely to notice booms from Starship landings and people located at CCAFS or KSC, within the 3.0 psf and 4.5 psf region, could possibly be startled.
The yellow line on the map corresponds to 3.0 psf.

The second image below moves this sonic boom map to the Boca Chica landing site.
Note that the yellow area covers all of Brownsville, Matamoros, South Padre Island, Harlingen, etc.
More than 1 million people live and work in this area (link here (https://en.wikipedia.org/wiki/Brownsville%E2%80%93Matamoros)).
I suspect this is why SpaceX has already started converting an offshore oil rig into to a launch/landing pad (link here (https://forum.nasaspaceflight.com/index.php?topic=52841.580)).

Note that sonic booms are not really an issue for Starship sub-orbital landings, or for Super-Heavy landings.
Both of these will come in from the opposite direction, so the noise will be mostly over the Gulf.
Also, since these vehicles will be traveling slower, the sonic booms won't be as loud.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JimOnMars on 05/08/2021 09:32 pm
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wes_wilson on 05/08/2021 09:48 pm
IANARS  But, assume for a moment, that Starship reaches a level of reliability where flight over populated areas is not a safety concern.  How much performance would be given up by launching Starship retrograde over the populated areas and therefore reversing the direction of the sonic boom on landing.  I ask because itsm that reliability is likely to improve substantially over time while the boom remains the boom; perhaps the solution is to reorient the boom. 

 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/08/2021 09:53 pm
IANARS  But, assume for a moment, that Starship reaches a level of reliability where flight over populated areas is not a safety concern.  How much performance would be given up by launching Starship retrograde over the populated areas and therefore reversing the direction of the sonic boom on landing.  I ask because itsm that reliability is likely to improve substantially over time while the boom remains the boom; perhaps the solution is to reorient the boom.

It makes booms on the way up too.  You just don't hear them when the vehicle is going away from you, and the rocket engines may well be louder anyway.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/08/2021 10:13 pm
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?

No.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mihai78 on 05/08/2021 10:31 pm
[…] How much performance would be given up by launching Starship retrograde over the populated areas and therefore reversing the direction of the sonic boom on landing. […]

You lose about 2*400 m/s by not using earth’s rotation and instead having to overcome it when launching west instead of east, right?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: I14R10 on 05/08/2021 11:04 pm
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?

I'm not american, but I remember reading somewhere that US companies answer to FAA no matter from which country they launch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/08/2021 11:08 pm
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?

I'm not american, but I remember reading somewhere that US companies answer to FAA no matter from which country they launch.

Yes. See RocketLab
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 05/09/2021 12:59 am
Apologies if this has been asked up-thread but is there any need to finish building SN17?
   1. (If) SN15 re-flies
   2. Either way, SN16 is there to finish off the "SN15-19" test regime

They could just wait till there's a need before stacking....

Because sn17 will probably have a full TPS.

Unfortunately it won't.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AU1.52 on 05/09/2021 01:23 am
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?


The noise booms here were for landing Starship, not launching it. Boom's would not be the issue. Also as SN20 will unlikely have any payload BN3 would not need a full compliment of engines, so the noise would not be that bad.


How much different would the noise levels be comparing FH (which was cleared to launch from Boca) and a limit SH with say 12 - 18 engines? Similar?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: TripD on 05/09/2021 07:07 am
I didn't see an SN15 specific discussion thread. It appears that SN15 did a quick roll maneuver directly after launch. Is there a reason for this other than just testing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/09/2021 08:22 am
I didn't see an SN15 specific discussion thread. It appears that SN15 did a quick roll maneuver directly after launch. Is there a reason for this other than just testing?
It's just an aerodynamic effect from the smoke, flaps stays in the same position. They're indeed rolling it though (shown from SN8), but not that quickly
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/09/2021 10:10 am
The noise booms here were for landing Starship, not launching it. Boom's would not be the issue. Also as SN20 will unlikely have any payload BN3 would not need a full compliment of engines, so the noise would not be that bad.

How much different would the noise levels be comparing FH (which was cleared to launch from Boca) and a limit SH with say 12 - 18 engines? Similar?

I agree.  I don't think launch noise will be an issue for SN20 / BN3.  As you say, FH was already approved.

The issue is landing noise, specifically sonic booms for SN20 returning from orbit.
The map predicts very loud sonic booms up to 30 miles West of the landing site.

It will be interesting to see if the FAA allows SN20 orbital flights to land at Boca Chica, or if they force them to land offshore.
With the rapid progress SpaceX is making on Phobos (https://twitter.com/GoBamaRollTide), landing SN20 offshore seems like an option.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/09/2021 11:21 am
So, IIUC, there is no way that faa will allow spacex to land starshipat Boca Chica ever, bacause of booms?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 05/09/2021 11:39 am

It will be interesting to see if the FAA allows SN20 orbital flights to land at Boca Chica, or if they force them to land offshore.
With the rapid progress SpaceX is making on Phobos (https://twitter.com/GoBamaRollTide), landing SN20 offshore seems like an option.

Looks like it’s still being stripped with a very long way to go in that process. What are you seeing that makes you say it’s anywhere rapid enough to support 2021 launches or returns?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Super08 on 05/09/2021 11:43 am
There was also a pretty good wind from that direction at the time of the launch.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/09/2021 01:20 pm
So, IIUC, there is no way that faa will allow spacex to land starship at Boca Chica ever, because of booms?
That's not clear yet. The FAA could make an exception for test flights, perhaps if they're not frequent.
They may also need permission from Mexico, since Matamoros is within the yellow line, and a half million people live there.
Or it may end up not being a problem at all. I'm not a sonic boom expert.
I'm just looking at what the experts said in the NASA environmental assessment for LC-39A, and applying that to Boca Chica.
Also, to be clear, sonic booms are only a potential issue for orbital Starship landings.
Sonic boom noise for suborbital Starship and Super Heavy landings don't appear to be an issue.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/09/2021 01:48 pm
It will be interesting to see if the FAA allows SN20 orbital flights to land at Boca Chica, or if they force them to land offshore.
With the rapid progress SpaceX is making on Phobos (https://twitter.com/GoBamaRollTide), landing SN20 offshore seems like an option.
Looks like it’s still being stripped with a very long way to go in that process. What are you seeing that makes you say it’s anywhere rapid enough to support 2021 launches or returns?
I believe they started stripping down Phobos around 3 months ago, shortly after they moved it to Pascagoula, Mississippi.
To my eyes, it appears they've removed around half the structures since then, but your mileage may vary.

Note that the latest renders from SpaceX (link here (https://forum.nasaspaceflight.com/index.php?topic=52841.msg2234837#msg2234837)) appear to show an offshore site with 2 separate refurbished oil rigs,
one for the launch pad, and a separate refurbished oil rig for landing. The landing rig appears to be just a flat surface.
The landing rig part may be all they need for initial test landings and short hops back to Boca Chica.

Anyway, as I said above, this is just a potential issue that may, or may not end up being a problem.
I'm just interested in how these types of issues will play out...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KBK on 05/09/2021 03:30 pm
There was also a pretty good wind from that direction at the time of the launch.

And the quick and obvious associated guess of why the vehicle ended up on the edge of the landing pad. Compensation was working it's self into the landing equation and wind is notoriously unpredictable. Especially on a first landing. Etc.

A possible check on that available to the people here, might involve looking at the leg crush cores, the levels and orientation of such as shared among individual feet, and the given bounce/slide orientation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ETurner on 05/09/2021 03:47 pm
The issue is landing noise, specifically sonic booms for SN20 returning from orbit.
The map predicts very loud sonic booms up to 30 miles West of the landing site.
To what extent could the sonic boom problem be mitigated by overshooting, descending east of Boca Chica, then using the minimal “glide” capabilities of SS to return westward?
In other words, in a world with a deep, thick atmosphere and a low mass/area Starship with an ample glide ratio, SS could descend through max-boom tens of kilometers offshore and still return to launch site. How close are we to that world? Enough to make a significant difference in the overpressure footprint?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/09/2021 04:09 pm
The issue is landing noise, specifically sonic booms for SN20 returning from orbit.
The map predicts very loud sonic booms up to 30 miles West of the landing site.
To what extent could the sonic boom problem be mitigated by overshooting, descending east of Boca Chica, then using the minimal “glide” capabilities of SS to return westward?
In other words, in a world with a deep, thick atmosphere and a low mass/area Starship with an ample glide ratio, SS could descend through max-boom tens of kilometers offshore and still return to launch site. How close are we to that world? Enough to make a significant difference in the overpressure footprint?
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 05/09/2021 04:15 pm
The issue is landing noise, specifically sonic booms for SN20 returning from orbit.
The map predicts very loud sonic booms up to 30 miles West of the landing site.
To what extent could the sonic boom problem be mitigated by overshooting, descending east of Boca Chica, then using the minimal “glide” capabilities of SS to return westward?
In other words, in a world with a deep, thick atmosphere and a low mass/area Starship with an ample glide ratio, SS could descend through max-boom tens of kilometers offshore and still return to launch site. How close are we to that world? Enough to make a significant difference in the overpressure footprint?
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.

This site says 2.5 to 1 for a human skydiver.
Given the similar shapes and similar terminal velocities I don't see why it wouldn't be close to the same.

https://www.facebook.com/Paws-n-Tails-USA-110375394477161/

EDIT: whoops. thats the parachute drift.
Now add the Freefall Drift of 2200 feet to 10,718 feet
So 1 to 5 instead of 2.5 to 1!

EDIT: EDIT:
https://en.wikipedia.org/wiki/Tracking_(skydiving)#Glide_ratio

Quote
Glide ratio
Good trackers can cover nearly as much ground as the distance they fall, approaching a glide ratio of 1:1. The fall rate of a skydiver in an efficient track is significantly lower than that of one falling in a traditional face-to-earth position; the former reaching speeds as low as 90 mph, the latter averaging around the 120 mph mark.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ETurner on 05/09/2021 05:00 pm
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.
Yes, I recall a plausible-looking estimate of subsonic L/D that was not much over 1.

Where sonic booms are concerned, the supersonic part of the trajectory is the problem (depending on altitude, speed, distance, AoA...), while the length of the subsonic ground track is important to keeping overpressure offshore. Not a simple question. Also, at what altitude does the atmosphere become thick enough that one can think in terms of a (sort-of!) glide?


With an approach from the east, it would help that Brownsville is inland by 20 km or so. Overpressure maps with approach from the west may or may not tell us much about prospects for orbital prototype flights returning to BC.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 05/09/2021 08:02 pm
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.
Yes, I recall a plausible-looking estimate of subsonic L/D that was not much over 1.

Where sonic booms are concerned, the supersonic part of the trajectory is the problem (depending on altitude, speed, distance, AoA...), while the length of the subsonic ground track is important to keeping overpressure offshore. Not a simple question. Also, at what altitude does the atmosphere become thick enough that one can think in terms of a (sort-of!) glide?


With an approach from the east, it would help that Brownsville is inland by 20 km or so. Overpressure maps with approach from the west may or may not tell us much about prospects for orbital prototype flights returning to BC.

4:5 is looking like a more realistic glide slope for the booster at subsonic.  :o
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: rsdavis9 on 05/09/2021 08:36 pm
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.
Yes, I recall a plausible-looking estimate of subsonic L/D that was not much over 1.

Where sonic booms are concerned, the supersonic part of the trajectory is the problem (depending on altitude, speed, distance, AoA...), while the length of the subsonic ground track is important to keeping overpressure offshore. Not a simple question. Also, at what altitude does the atmosphere become thick enough that one can think in terms of a (sort-of!) glide?


With an approach from the east, it would help that Brownsville is inland by 20 km or so. Overpressure maps with approach from the west may or may not tell us much about prospects for orbital prototype flights returning to BC.

4:5 is looking like a more realistic glide slope for the booster at subsonic.  :o

And the big question is at what altitude can you get what glide ratio?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 05/09/2021 08:51 pm
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.
Yes, I recall a plausible-looking estimate of subsonic L/D that was not much over 1.

Where sonic booms are concerned, the supersonic part of the trajectory is the problem (depending on altitude, speed, distance, AoA...), while the length of the subsonic ground track is important to keeping overpressure offshore. Not a simple question. Also, at what altitude does the atmosphere become thick enough that one can think in terms of a (sort-of!) glide?


With an approach from the east, it would help that Brownsville is inland by 20 km or so. Overpressure maps with approach from the west may or may not tell us much about prospects for orbital prototype flights returning to BC.

4:5 is looking like a more realistic glide slope for the booster at subsonic.  :o

And the big question is at what altitude can you get what glide ratio?

Glide slope ratio discussion in Engineering thread:   https://forum.nasaspaceflight.com/index.php?topic=49622.msg2232780#msg2232780

TL;DR - it requires a numerical simulation to figure out what it is, and the best ratio is at supersonic.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ETurner on 05/09/2021 10:07 pm
There isn’t much glide capability to do that. People have (wishfully) speculated a glide ratio of 2, but I suspect it is far less when subsonic.

This is not a glider aircraft, this is a cylinder that is “falling with style”.
Yes, I recall a plausible-looking estimate of subsonic L/D that was not much over 1.

Where sonic booms are concerned, the supersonic part of the trajectory is the problem (depending on altitude, speed, distance, AoA...), while the length of the subsonic ground track is important to keeping overpressure offshore. Not a simple question. Also, at what altitude does the atmosphere become thick enough that one can think in terms of a (sort-of!) glide?


With an approach from the east, it would help that Brownsville is inland by 20 km or so. Overpressure maps with approach from the west may or may not tell us much about prospects for orbital prototype flights returning to BC.

4:5 is looking like a more realistic glide slope for the booster at subsonic.

And the big question is at what altitude can you get what glide ratio?

A very rough estimate (g * vehicle mass/area = air density * velocity^2)) suggests supersonic flight and L/D down to about 30 km altitude. That would give a subsonic ground track ~30 km long, if L/D ~ 1.
At what altitude could SS shed enough eastward velocity to turn around and glide (= stylishly fall) westward? Inquiring minds want to know are somewhat curious.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kiwi53 on 05/10/2021 05:08 am
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?

Absolutely not.

Firstly it doesn't make the FAA restrictions go away.

Secondly, and much more importantly, there's ITAR and the Missile Technology Transfer treaty (or similar name)
Consider the Nazi German V2, and how much devastation it caused delivering a 1 tonne payload to southern England. Now think in the same context about Spaceship delivering 100 tonnes of commercial blasting explosive plus an equal amount of LOX and LCH4 anywhere within several thousand kilometres of a launch site.
Scary,isn't it?
And that's why Spaceship launches are always going to be under strict US government scrutiny and (possibly indirect) control.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/10/2021 07:00 am
Okay here's a thought on a first SH/SS launch to orbit this year. It assumes several nuggets of information that we've seen and is intended only for the first flight or two to orbit:

1. Elon has said that occasional launches of SH from Boca Chica are okay, but not frequent launches. That makes sense. The distance from the launch site to the hotels on South Padre Island is such that frequent launches, especially at night, might be a bit much, but a once-in-a-while daytime launch might bring in a lot of tourists to that park at the south end.

2. SH returning back to the launch site will be a similar profile to that of Falcon 9's first stage. If they can convince the FAA that the vehicle is capable of similar behavior, then it should be okay. The sonic boom will be a certain amount larger in intensity. It will have to be safe for South Padre, again. South Padre is going to be like Playalinda is for KSC!

3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG). Tow it back to the Brownsville Ship Channel, and transport over road back to Boca Chica. This requires a few assumptions (ahem):

A. ASOG finished by summer. Pretty safe. They're building it anyway, so it doesn't add anything to the budget.

B. SS must be able to hit the target. While the SN15 flight didn't (possibly because of the one engine not re-lighting), I don't see why, from a hardware standpoint, it couldn't be done. I realize that SS is bigger, but that doesn't mean it needs a larger landing error area. They have to put better legs on, but they really need to do that soon anyway. These are test flights that will only be done under good conditions, so SS doesn't need as wide a leg-span or an Octograbber to deal with rougher sea-states. I seriously doubt the size and weight of a SS will affect a ballasted-down Marmac 300. A barge and tug of this size is a whole magnitude smaller, cheaper, and handier than the converted oil platforms

C: The connector road being built from the Ship Channel south must be complete enough to allow the passage of the SPMTs and the clearance for the vertical SS from SpaceX's property on the Channel to Boca Chica.

If the higher parts of the re-entry trajectory are still a sensitive issue, the landing could be moved all the way over to the other side of the Gulf of Mexico. The barge could be towed into a Florida port, SS secured for the passage, and then towed back across to Brownsville, just like other oversized cargo. Or, they could just do it at sea, if conditions look good.

Again, this is ONLY for the first, or first few flights, until better infrastructure is built, and assumes that they really want to launch this thing this year.

Watcha think?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/10/2021 07:03 am
For a Starship orbital missions from Boca Chica, there may be some issues.

The latest FAA re-evaluation dated December 2020 (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)) only discusses SS altitudes up to 30 kilometers.
Anything higher than that will probably require new EIS, or at least a new environmental assessment.
Note that the term "environmental" covers a lot more than just the local ecology.
It also covers human safety, potential property damage, noise, and any other public concerns.

Couldn't Elon just pick up the whole kit and caboodle and move 2km south?

Absolutely not.

Firstly it doesn't make the FAA restrictions go away.

Secondly, and much more importantly, there's ITAR and the Missile Technology Transfer treaty (or similar name)
Consider the Nazi German V2, and how much devastation it caused delivering a 1 tonne payload to southern England. Now think in the same context about Spaceship delivering 100 tonnes of commercial blasting explosive plus an equal amount of LOX and LCH4 anywhere within several thousand kilometres of a launch site.
Scary,isn't it?
And that's why Spaceship launches are always going to be under strict US government scrutiny and (possibly indirect) control.
Starship would make an incredibly shitty weapons delivery system, but ITAR is like the honey badger when it comes to arguments like this.

Starship doesn't have to literally be weaponizable..  It just has to fall into the category of technologies and know-how that ITAR cares about (i.e. rocketry) and that's the end of that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RobLynn on 05/10/2021 01:10 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG). Tow it back to the Brownsville Ship Channel, and transport over road back to Boca Chica. This requires a few assumptions (ahem):
Watcha think?

Operations a long way off shore are horribly expensive in terms of worker transport and logistics.  But it's hard to see how they can be avoided long term given huge reentry noise footprint.  Maybe the coming age of cheap VTOL electric air taxis will help - but only out to about 60-70 miles offshore.

I personally don't think that you could beat a small fleet of large fast catamaran or SWATH drone ships as launch and landing base - can pull into dock or shipyard for cheap accessible workforce modifications or repairs (and at a major population centre on the gulf coast like Houston) but be far enough offshore for launch and minimally noisy re-entry profiles in a few hours.

Ships are relatively cheap to build compared to everything else.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 05/10/2021 01:19 pm
https://twitter.com/NASASpaceflight/status/1391281917140639745

Why are they faking the graphic with unrelated info on the bottom?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: schuttle89 on 05/10/2021 01:21 pm
https://twitter.com/NASASpaceflight/status/1391281917140639745

Why are they faking the graphic with unrelated info on the bottom?
The graphic is for the starlink launch that this clip was played during
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Frogstar_Robot on 05/10/2021 01:23 pm

Why are they faking the graphic with unrelated info on the bottom?

It's not fake, it is data from the Starlink mission that the video happened to be shown in.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 05/10/2021 01:28 pm

Why are they faking the graphic with unrelated info on the bottom?

It's not fake, it is data from the Starlink mission that the video happened to be shown in.

that makes more sense.  :-X
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: su27k on 05/10/2021 01:30 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Bananas_on_Mars on 05/10/2021 02:01 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

And if they‘re landing near the Bahamas, they don‘t have to return to the Port of Brownsville but could transport that Starship to KSC instead.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jpo234 on 05/10/2021 02:06 pm
Starship doesn't have to literally be weaponizable..  It just has to fall into the category of technologies and know-how that ITAR cares about (i.e. rocketry) and that's the end of that.
This is covered by ITAR if used to open the control box of a missile system (not the actual thing).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sebk on 05/10/2021 04:27 pm
The issue is landing noise, specifically sonic booms for SN20 returning from orbit.
The map predicts very loud sonic booms up to 30 miles West of the landing site.
To what extent could the sonic boom problem be mitigated by overshooting, descending east of Boca Chica, then using the minimal “glide” capabilities of SS to return westward?
In other words, in a world with a deep, thick atmosphere and a low mass/area Starship with an ample glide ratio, SS could descend through max-boom tens of kilometers offshore and still return to launch site. How close are we to that world? Enough to make a significant difference in the overpressure footprint?

You could maybe move the yellow area 20km eastwards. It would still likely cover Port Isabel and South Pader Island.

Maybe it would help more if they moved their supersonic approach path ~15-20km south and instead of 180° turnaround they would do reverse 120° dogleg towards NW. They would still need approval from Mexico, but at least the area is mostly empty.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 05/10/2021 04:27 pm
Starship doesn't have to literally be weaponizable..  It just has to fall into the category of technologies and know-how that ITAR cares about (i.e. rocketry) and that's the end of that.
This is covered by ITAR if used to open the control box of a missile system (not the actual thing).

The kinetic energy of 100,000 kg of Starship payload  moving at orbital velocity of 7.8 km/sec is 3x10^12 joules or 0.7 ktons of TNT equivalent.

Yeah, ITAR applies.   Starship is the first launch system that makes the Rods from the Gods feasible
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/10/2021 04:47 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/10/2021 05:00 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.

Never say never... I wouldn't rule it out for some test flights. (not operational use) They are just big enough, assuming future SN's can demonstrate improved landing accuracy.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mader Levap on 05/10/2021 05:06 pm
The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.

Never say never... I wouldn't rule it out for some test flights. (not operational use) They are just big enough, assuming future SN's can demonstrate improved landing accuracy.
If droneships could be used for landings of starship, they would not bother with oil rigs. No, you do not get to handwave it away as "test flights". In fact, I expect test flight to require larger footprint, not smaller.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/10/2021 05:08 pm
The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.

Never say never... I wouldn't rule it out for some test flights. (not operational use) They are just big enough, assuming future SN's can demonstrate improved landing accuracy.
If droneships could be used for landings of starship, they would not bother with oil rigs. No, you do not get to handwave it away as "test flights". In fact, I expect test flight to require larger footprint, not smaller.

Why so confrontational? I'm not hand-waving away anything. These hypothetical test flights would only happen if they want to go higher/further and land down-range before the oil rigs are ready.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 05:20 pm
The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.

Never say never... I wouldn't rule it out for some test flights. (not operational use) They are just big enough, assuming future SN's can demonstrate improved landing accuracy.
If droneships could be used for landings of starship, they would not bother with oil rigs. No, you do not get to handwave it away as "test flights". In fact, I expect test flight to require larger footprint, not smaller.

The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mader Levap on 05/10/2021 05:27 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/10/2021 05:43 pm
The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.


Never say never... I wouldn't rule it out for some test flights. (not operational use) They are just big enough, assuming future SN's can demonstrate improved landing accuracy.
If droneships could be used for landings of starship, they would not bother with oil rigs. No, you do not get to handwave it away as "test flights". In fact, I expect test flight to require larger footprint, not smaller.

The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.


Great point

IMO an important thing if they feel comfortable to risk ASOG or any other drownship to land SS. Even if SpaceX showed to not care a lot about risk, but with F9 in the latest times they take the minimum risk, so risking the wanted-for-a-lot-of-time droneship is a chiche they won't take easily IMO.
 Remembre f9 first stage is 25 tons, and SS 120 tons.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: eriblo on 05/10/2021 05:48 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
The landable area on the ASDSs is 52 m by ~70 m and the total deck area of the platforms (i.e. if they clear everything away) is 73 m by 76 m. The original barges had a max cargo capacity of 12000 t while the platforms had a "variable deck load" of 8000 t (or possibly short tons). Neither will notice a landing Starship at ~150 t.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/10/2021 05:54 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
They picked this size of a drone ship for F9 because they didn't know how accurate they could make F9 landings, and this was the largest practical barge size for a small investment.

As far as it being large enough for Starship. It is certainly large enough. Look at the attached image - The yellow circle alone is ~22 meters across. While Starship has an almost 3x greater diameter than F9, its leg stance is actually narrower (~10m with the current prototype legs)

And as far as weight capacity, these barges usually have capacities in the multiple 1000 ton range.

The only issue would be if the deck is strong enough to handle the landing impact from 6 legs.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/10/2021 05:54 pm
I think that if sn16 and sn17 fly and re fly, demonstrating that they can land reliably they could seriously use an ASDS, but they will need to land the SS nearly perfect on target, unlike sn15.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/10/2021 05:57 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
They picked this size of a drone ship for F9 because they didn't know how accurate they could make F9 landings, and this was the largest practical barge size for a small investment.

As far as it being large enough for Starship. It is certainly large enough. Look at the attached image - The yellow circle alone is ~22 meters across. While Starship has an almost 3x greater diameter than F9, its leg stance is actually narrower (~10m with the current prototype legs)

And as far as weight capacity, these barges usually have capacities in the multiple 1000 ton range.

The only issue would be if the deck is strong enough to handle the landing impact from 6 legs.

If the flip is worked out reliably in the aspect of landing precision we can aspect an even biffer accuracy than f9, due to lower t/w ratio and a very more gentle final descent.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 05/10/2021 06:11 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jaxon9182 on 05/10/2021 06:22 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...

It won't have a payload, the nosecone will likely resemble what they are currently using on Starship. Wasting the time will cost them way more than "wasting" the launch. The only payload might be something silly and small the engineers stick in it, or an outline of the mannequin cowboy flown on grasshopper that they outlined on Starhopper
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: waveney on 05/10/2021 06:47 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...

I think the chomper would be a shark, not an elephant.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 06:53 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
They picked this size of a drone ship for F9 because they didn't know how accurate they could make F9 landings, and this was the largest practical barge size for a small investment.

As far as it being large enough for Starship. It is certainly large enough. Look at the attached image - The yellow circle alone is ~22 meters across. While Starship has an almost 3x greater diameter than F9, its leg stance is actually narrower (~10m with the current prototype legs)

And as far as weight capacity, these barges usually have capacities in the multiple 1000 ton range.

The only issue would be if the deck is strong enough to handle the landing impact from 6 legs.

If the flip is worked out reliably in the aspect of landing precision we can aspect an even biffer accuracy than f9, due to lower t/w ratio and a very more gentle final descent.

The main issue with the current drone ships would be keeping Starship from falling over after landing. With F9, the octograbber locks F9 down soon after landing. With Starship, they would need to modify or use a different robot, or even worse, manually secure Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: deMangler on 05/10/2021 06:54 pm
Given the biggest financial loss of soft landing at sea is the raptors, and they need to test orbital landing soon.

Also given that SpaceX testing philosophy seems to be, if it is physically possible to do something we would like to do, lets give it a good shot and see what we need to do to succeed., then...

Seeing as it is physically possible to land one on a drone ship, it seems like it would be really unlikely that they do not try to land an SS on a drone ship at some point soon.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: racevedo88 on 05/10/2021 06:56 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...

IMHO this will probably be farther down the road in the program. As it is not needed for Mars, HLS, or refueling. I expect them to tackle launch reentry and landing, then Orbital refueling, HLS demo, Mars demo, ECLSS, Crew rating, elevator and cargo loading and unloading those thing needed for HLS and Mars program that either Elon or NASA have committed dates for.  Cargo starship can be delayed as SpaceX still has the capability to serve most of its cargo costumers on F9 and FH.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ach1000 on 05/10/2021 07:01 pm
The main issue with the current drone ships would be keeping Starship from falling over after landing. With F9, the octograbber locks F9 down soon after landing. With Starship, they would need to modify or use a different robot, or even worse, manually secure Starship.

The Octograbber is relatively recent; previously they manually secured F9 after landing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 07:01 pm
Given the biggest financial loss of soft landing at sea is the raptors, and they need to test orbital landing soon.

Also given that SpaceX testing philosophy seems to be, if it is physically possible to do something we would like to do, lets give it a good shot and see what we need to do to succeed., then...

Seeing as it is physically possible to land one on a drone ship, it seems like it would be really unlikely that they do not try to land an SS on a drone ship at some point soon.

This would be a high probably in the case that they can't land back at Boca Chica or one of the other landing zones they own. I don't think those oil rigs will be ready in time for early orbital flights. They may not use them anyway, since they would really want to use production vehicles since transporting test vehicles from them would be much more difficult.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 07:03 pm
The main issue with the current drone ships would be keeping Starship from falling over after landing. With F9, the octograbber locks F9 down soon after landing. With Starship, they would need to modify or use a different robot, or even worse, manually secure Starship.

The Octograbber is relatively recent; previously they manually secured F9 after landing.

I was remembering the recent loss of a FH center booster because Octograbber wasn't able to secure it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 05/10/2021 07:07 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...

IMHO this will probably be farther down the road in the program. As it is not needed for Mars, HLS, or refueling. I expect them to tackle launch reentry and landing, then Orbital refueling, HLS demo, Mars demo, ECLSS, Crew rating, elevator and cargo loading and unloading those thing needed for HLS and Mars program that either Elon or NASA have committed dates for.  Cargo starship can be delayed as SpaceX still has the capability to serve most of its cargo costumers on F9 and FH.
Starlink is also a very high priority for the company. It would be kind of cool though to see a deployment method that spits out Starlinks one at a time like dealing cards.  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: racevedo88 on 05/10/2021 07:10 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...

IMHO this will probably be farther down the road in the program. As it is not needed for Mars, HLS, or refueling. I expect them to tackle launch reentry and landing, then Orbital refueling, HLS demo, Mars demo, ECLSS, Crew rating, elevator and cargo loading and unloading those thing needed for HLS and Mars program that either Elon or NASA have committed dates for.  Cargo starship can be delayed as SpaceX still has the capability to serve most of its cargo costumers on F9 and FH.
Starlink is also a very high priority for the company. It would be kind of cool though to see a deployment method that spits out Starlinks one at a time like dealing cards.  :)
don’t disagree that star link is high priority, but they can still be launched by F9, it is all a question of where Chomper falls in critical path
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CyclicVoltmanatee on 05/10/2021 07:18 pm
It won't have a payload, the nosecone will likely resemble what they are currently using on Starship. Wasting the time will cost them way more than "wasting" the launch. The only payload might be something silly and small the engineers stick in it, or an outline of the mannequin cowboy flown on grasshopper that they outlined on Starhopper

I don't know about having no payload! They like to fly cars after all! I wouldn't put it past them to try and orbit a car and return it to Earth (no need to take it out of Starship so no need for a functioning chomper design) ... then use that same car to drive astronauts up to a Dragon launch.

It's fun, gets people's attention, and also serves as a demonstrator of Starship actually landing cargo. Probably won't happen but I think it would be cool (and if an idiot like me has thought it up, I'm sure someone at SpaceX has had the thought too).

I'd put money on them at least having talked stuff like that over. :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/10/2021 07:39 pm
It won't have a payload, the nosecone will likely resemble what they are currently using on Starship. Wasting the time will cost them way more than "wasting" the launch. The only payload might be something silly and small the engineers stick in it, or an outline of the mannequin cowboy flown on grasshopper that they outlined on Starhopper

I don't know about having no payload! They like to fly cars after all! I wouldn't put it past them to try and orbit a car and return it to Earth (no need to take it out of Starship so no need for a functioning chomper design) ... then use that same car to drive astronauts up to a Dragon launch.

It's fun, gets people's attention, and also serves as a demonstrator of Starship actually landing cargo. Probably won't happen but I think it would be cool (and if an idiot like me has thought it up, I'm sure someone at SpaceX has had the thought too).

I'd put money on them at least having talked stuff like that over. :)
I dont' expect sn20 having any payload different than a mass simulator (and probably it won't have even this), because there isn't time. Integrating the roadster in falcon heavy , because the technology of the payload fairing was proved and well developed. But I expect the cargo deployment mechanism to be developed ASAP, because the sooner it is developed the sooner they can deploy starlink satelites, starting to make profit  (even if not directly)from the program.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 07:45 pm
It won't have a payload, the nosecone will likely resemble what they are currently using on Starship. Wasting the time will cost them way more than "wasting" the launch. The only payload might be something silly and small the engineers stick in it, or an outline of the mannequin cowboy flown on grasshopper that they outlined on Starhopper

I don't know about having no payload! They like to fly cars after all! I wouldn't put it past them to try and orbit a car and return it to Earth (no need to take it out of Starship so no need for a functioning chomper design) ... then use that same car to drive astronauts up to a Dragon launch.

It's fun, gets people's attention, and also serves as a demonstrator of Starship actually landing cargo. Probably won't happen but I think it would be cool (and if an idiot like me has thought it up, I'm sure someone at SpaceX has had the thought too).

I'd put money on them at least having talked stuff like that over. :)
I dont' expect sn20 having any payload different than a mass simulator (and probably it won't have even this), because there isn't time. Integrating the roadster in falcon heavy , because the technology of the payload fairing was proved and well developed. But I expect the cargo deployment mechanism to be developed ASAP, because the sooner it is developed the sooner they can deploy starlink satelites, starting to make profit  (even if not directly)from the program.

Not only that, but I don't think early SH will have a full compliment of engines. Early flights will likely have few Raptors and not a lot of fuel. They'll just want to get to orbit, return of booster, test heatshield and recover Starship if it survives. I don't think payloads will be a priority on the first flights.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CyclicVoltmanatee on 05/10/2021 08:13 pm
I dont' expect sn20 having any payload different than a mass simulator (and probably it won't have even this), because there isn't time. Integrating the roadster in falcon heavy , because the technology of the payload fairing was proved and well developed. But I expect the cargo deployment mechanism to be developed ASAP, because the sooner it is developed the sooner they can deploy starlink satelites, starting to make profit  (even if not directly)from the program.

I mean, I agree the most likely payload will be none-at-all.

But, the ultimate goal of these ships is not to put stuff in orbit around Earth, but to land stuff on other planets. They've been pretty open about that. Just recently Musk was tweeting about landing unmanned on Mars within a few years. At some point the flip maneuver will need to be tested with substantial cargo onboard (if only to verify their simulations), so why not do it sooner than later.

I too want to see them throw starlinks with starship (mainly because that means I get my space internet faster!) but let's be honest, Starlink (the company) will be absolutely printing money even without starship to put the satellites up.

Like you, I have no doubt it will be built, but is it really more important than demonstrating the flip maneuver with cargo, which is critical for Mars. And what about orbital refueling? Is chomper (or something like it) even needed for stuff like orbital refueling, Mars, or the Moon, I didn't think it was?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CyclicVoltmanatee on 05/10/2021 08:17 pm
IMHO this will probably be farther down the road in the program. As it is not needed for Mars, HLS, or refueling. I expect them to tackle launch reentry and landing, then Orbital refueling, HLS demo, Mars demo, ECLSS, Crew rating, elevator and cargo loading and unloading those thing needed for HLS and Mars program that either Elon or NASA have committed dates for.  Cargo starship can be delayed as SpaceX still has the capability to serve most of its cargo costumers on F9 and FH.

Didn't see this before I posted! I totally concur with this potential timeline.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 08:18 pm
I dont' expect sn20 having any payload different than a mass simulator (and probably it won't have even this), because there isn't time. Integrating the roadster in falcon heavy , because the technology of the payload fairing was proved and well developed. But I expect the cargo deployment mechanism to be developed ASAP, because the sooner it is developed the sooner they can deploy starlink satelites, starting to make profit  (even if not directly)from the program.

I mean, I agree the most likely payload will be none-at-all.

But, the ultimate goal of these ships is not to put stuff in orbit around Earth, but to land stuff on other planets. They've been pretty open about that. Just recently Musk was tweeting about landing unmanned on Mars within a few years. At some point the flip maneuver will need to be tested with substantial cargo onboard (if only to verify their simulations), so why not do it sooner than later.

I too want to see them throw starlinks with starship (mainly because that means I get my space internet faster!) but let's be honest, Starlink (the company) will be absolutely printing money even without starship to put the satellites up.

Like you, I have no doubt it will be built, but is it really more important than demonstrating the flip maneuver with cargo, which is critical for Mars. And what about orbital refueling? Is chomper (or something like it) even needed for stuff like orbital refueling, Mars, or the Moon, I didn't think it was?

The current Starship bottleneck from all indications is Raptor right now. They may not want to risk 28+6 engines on an early flight that is really about heatshield and recovery.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CyclicVoltmanatee on 05/10/2021 08:24 pm
Not only that, but I don't think early SH will have a full compliment of engines. Early flights will likely have few Raptors and not a lot of fuel. They'll just want to get to orbit, return of booster, test heatshield and recover Starship if it survives. I don't think payloads will be a priority on the first flights.

For sure not a priority! I just don't get why people think they won't give it a try. It seems they can cover their priorities just fine and still do other things (sometimes fun and unusual things!). There is a bar being built right now on top of their main integration site and they literally write memes on their rocket engines!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/10/2021 08:44 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

And if they‘re landing near the Bahamas, they don‘t have to return to the Port of Brownsville but could transport that Starship to KSC instead.

I'm not sure if that's possible. The combination of the wings on the ASDSs (can it go through the locks at Port Canaveral?), and the height of the SS (which is not designed for horizontal transport, so can it go vertical from the Port through the Space Force part of the Cape?) might make that difficult. Sooner or later, they will have to figure out how to transfer Starships and Superheavies between launch sites, but that has been discussed in other threads.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/10/2021 08:47 pm
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.

SpaceX wants to launch this summer. This idea (which is just that) , is a temporary solution and is only for the LANDING of the first flight or two, until the rigs are ready.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/10/2021 08:52 pm
The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.

Never say never... I wouldn't rule it out for some test flights. (not operational use) They are just big enough, assuming future SN's can demonstrate improved landing accuracy.
If droneships could be used for landings of starship, they would not bother with oil rigs. No, you do not get to handwave it away as "test flights". In fact, I expect test flight to require larger footprint, not smaller.

They don't need all the capabilities of the the oil rigs because this would JUST be for a landing. Only SpaceX can answer the question of what sort of accuracy they will have this summer. They have more operational experience than anyone in the world for this sort of thing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/10/2021 08:58 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?

Landing footprint is set by the size of the landing gear, not the diameter of the rocket. The weight of Starship is negligible compared to the weight of the barge, which is not only of an extremely stable shape, but can ballast down as far as necessary to ensure stability. A Marmac 300 (the one used for the first ASDS), has even been submerged for salvage operations (and then lifted a ship about the size of Shelia Bordelon).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: darkenfast on 05/10/2021 09:06 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
They picked this size of a drone ship for F9 because they didn't know how accurate they could make F9 landings, and this was the largest practical barge size for a small investment.

As far as it being large enough for Starship. It is certainly large enough. Look at the attached image - The yellow circle alone is ~22 meters across. While Starship has an almost 3x greater diameter than F9, its leg stance is actually narrower (~10m with the current prototype legs)

And as far as weight capacity, these barges usually have capacities in the multiple 1000 ton range.

The only issue would be if the deck is strong enough to handle the landing impact from 6 legs.

If the flip is worked out reliably in the aspect of landing precision we can aspect an even biffer accuracy than f9, due to lower t/w ratio and a very more gentle final descent.

The main issue with the current drone ships would be keeping Starship from falling over after landing. With F9, the octograbber locks F9 down soon after landing. With Starship, they would need to modify or use a different robot, or even worse, manually secure Starship.

Correct, to a point. This is for the first test flight or two and is an idea to enable a flight this summer or shortly after. I don't believe they would fly these unless the weather and sea state is good at both launch and landing sites. In these tests, the SS can be secured with chains, the same way as early Falcon flights were. The Octograbber was necessary to expand the conditions under which Falcon 9 could be recovered once the tempo picked up. That role will be taken by the oil rig launch and landing ships.

Edit for typo.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/10/2021 09:10 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...

IMHO this will probably be farther down the road in the program. As it is not needed for Mars, HLS, or refueling. I expect them to tackle launch reentry and landing, then Orbital refueling, HLS demo, Mars demo, ECLSS, Crew rating, elevator and cargo loading and unloading those thing needed for HLS and Mars program that either Elon or NASA have committed dates for.  Cargo starship can be delayed as SpaceX still has the capability to serve most of its cargo costumers on F9 and FH.
Starlink is also a very high priority for the company. It would be kind of cool though to see a deployment method that spits out Starlinks one at a time like dealing cards.  :)
Sounds cool, but I can't imagine such a think working well.  Why raise, and then lower the orbit of a whole starship full of sats to move between the various orbital points needed when you can do it only once for each sat.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 05/10/2021 09:12 pm
I don’t think there’s any particular rush to sort out ASDS or the platforms or anywhere for landing of the first few orbital flights, as (according to Elon) it will take a while before the prototypes make it through EDL intact and there is anything left that is capable of landing. Btw, this is the wrong thread to be discussing ASDS or landing platforms, so kindly take it somewhere else and keep this thread for discussion of the actual prototypes being built...

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matthewkantar on 05/10/2021 09:14 pm
With Starhoppers, Starship, Booster, Test rig, GSE tanks, tank hoppers, etc, it's starting to look like they are building a chess set. Shiny moves first, then tiles.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/10/2021 09:31 pm
With Starhoppers, Starship, Booster, Test rig, GSE tanks, tank hoppers, etc, it's starting to look like they are building a chess set. Shiny moves first, then tiles.

Pawn -> Starhopper
Rooks -> GSE1/GSE2
Bishop -> SN15
Knight -> Test rig
King -> Kong
Queen -> Bluezilla
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 09:54 pm
I don’t think there’s any particular rush to sort out ASDS or the platforms or anywhere for landing of the first few orbital flights, as (according to Elon) it will take a while before the prototypes make it through EDL intact and there is anything left that is capable of landing. Btw, this is the wrong thread to be discussing ASDS or landing platforms, so kindly take it somewhere else and keep this thread for discussion of the actual prototypes being built...

SN20 and BN3 are in build progress. The testing regime for these is definitely on topic. Whether they land on a landing pad or a drone ship during this testing is definitely on topic here as a result.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Scintillant on 05/10/2021 09:55 pm
They have moved the nosecone test rig to the....landing pad?
Speculation: if they're done with nosecone tests (as the removal of flap simulators could indicate), they might just be getting it out of the way to free up space at the build site. Since they likely aren't launching again for at least 2-3 weeks, might as well use the landing pad for storage for now.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/10/2021 10:21 pm
They have moved the nosecone test rig to the....landing pad?
Speculation: if they're done with nosecone tests (as the removal of flap simulators could indicate), they might just be getting it out of the way to free up space at the build site. Since they likely aren't launching again for at least 2-3 weeks, might as well use the landing pad for storage for now.

Or they plan to place SN15 on Pad B, and the nosecone testing rig was in the way, so it was just moved temporarily. Could be the simplest explanation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 05/10/2021 10:21 pm
I don’t think there’s any particular rush to sort out ASDS or the platforms or anywhere for landing of the first few orbital flights, as (according to Elon) it will take a while before the prototypes make it through EDL intact and there is anything left that is capable of landing. Btw, this is the wrong thread to be discussing ASDS or landing platforms, so kindly take it somewhere else and keep this thread for discussion of the actual prototypes being built...

SN20 and BN3 are in build progress. The testing regime for these is definitely on topic. Whether they land on a landing pad or a drone ship during this testing is definitely on topic here as a result.

Nope, there is a thread for Starship Landing Discussions, cluttering this thread up with idle speculation really increases the noise/signal ratio...

If you want to discuss the building process of SM20 or BN3 you‘re in the right thread. You‘ve been on this site long enough to know better, Capoman 🤔
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/10/2021 10:28 pm
I don’t think there’s any particular rush to sort out ASDS or the platforms or anywhere for landing of the first few orbital flights, as (according to Elon) it will take a while before the prototypes make it through EDL intact and there is anything left that is capable of landing. Btw, this is the wrong thread to be discussing ASDS or landing platforms, so kindly take it somewhere else and keep this thread for discussion of the actual prototypes being built...

SN20 and BN3 are in build progress. The testing regime for these is definitely on topic. Whether they land on a landing pad or a drone ship during this testing is definitely on topic here as a result.

Nope, there is a thread for Starship Landing Discussions, cluttering this thread up with idle speculation really increases the noise/signal ratio...

If you want to discuss the building process of SM20 or BN3 you‘re in the right thread. You‘ve been on this site long enough to know better, Capoman 🤔

Beyond, SN20 and BN3 in progress, I’d agree with you. For those in progress, no. Most discussion here is speculation, not statement of observation. If speculation was considered off topic, 90% of discussion here would be off topic.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/10/2021 11:52 pm
Most discussion here is speculation, not statement of observation. If speculation was considered off topic, 90% of discussion here would be off topic.

If it's speculation ABOUT THE PROTOTYPES, it's on-topic. But if it's more arm-chair engineer/hand-waving mumblety-mumblety-ELON!!! talk, it's not. There are specific threads for all kinds of those rabbit-hole topics: general engineering, facilities and fleets, landing discussion, trajectory planning and brainstorming, landing legs/feet, repurposed oil rig platforms, ASDS's ...

Every single one of those above - and dozens more - have specific topics. The fact that people are too lazy to actually go find them and use them doesn't make talking about them HERE in this thread "on-topic" by any stretch of imagination.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 02:15 am
Most discussion here is speculation, not statement of observation. If speculation was considered off topic, 90% of discussion here would be off topic.

If it's speculation ABOUT THE PROTOTYPES, it's on-topic. But if it's more arm-chair engineer/hand-waving mumblety-mumblety-ELON!!! talk, it's not. There are specific threads for all kinds of those rabbit-hole topics: general engineering, facilities and fleets, landing discussion, trajectory planning and brainstorming, landing legs/feet, repurposed oil rig platforms, ASDS's ...

Every single one of those above - and dozens more - have specific topics. The fact that people are too lazy to actually go find them and use them doesn't make talking about them HERE in this thread "on-topic" by any stretch of imagination.

If we are speculating about potential test scenarios for currently being built prototypes, including where they are going to have to land, it is on topic about the current prototypes. That is the only point I was making.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/11/2021 02:25 am
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.
On this forum, "period" means "maybe", based on track record.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 05/11/2021 04:36 am
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.
On this forum, "period" means "maybe", based on track record.
While the ASDS appear comfortably large enough to land a Starship, they are a little busy with the current F9 launch cadence. 

I would assume that ASOG will be used to either increase that rate or maintain the same rate while allowing the other ships to be serviced.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SeaRaven on 05/11/2021 08:49 am
3. That leaves the tricky bit: Re-entry and landing for Starship. All the problems have been laid out above and in other threads. The mobile platforms, Phobos and Deimos, are a long way from being operational, and are pretty big ships that will require crews and operational training. My idea is a bit simpler: Move the landing far out enough to sea to address the problems and land Starship on "A Shortfall of Gravitas" (ASOG).

There's some unconfirmed rumor on reddit saying the same thing, Starship reenter over the gulf, target landing on ASOG which will be parked near the Bahamas.

The ASDS’, will never be used for starship, period. That’s why the rigs exist, to do what the drone ships do plus more.
On this forum, "period" means "maybe", based on track record.
While the ASDS appear comfortably large enough to land a Starship, they are a little busy with the current F9 launch cadence. 

I would assume that ASOG will be used to either increase that rate or maintain the same rate while allowing the other ships to be serviced.

I would hazard a guess that JRTI will be heading back to Vandy for the Starlink polar launches, and OCISLY and ASOG team tagging with launches.  ASOG may want to be within reach of an engineering shipyard familiar with servicing the ASDS's.  ASOG's shakedown may turn up a few issues which may need addressing.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/11/2021 11:10 am

I would hazard a guess that JRTI will be heading back to Vandy for the Starlink polar launches, and OCISLY and ASOG team tagging with launches. 

They can do polar launches out of Florida with the southern corridor. No need to launch from Vandenberg.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 05/11/2021 11:32 am
Nosecone in tent 3.

Is it just me or does this nosecone appear to have a split where a payload door would be? Picture of course Mary (@BocaChicaGal)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: electricdawn on 05/11/2021 11:37 am
Nope, just looks like it. Zoom in and you will see that weld lines appear to be pretty close together, but not really that close.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Thunderscreech on 05/11/2021 12:18 pm

I would hazard a guess that JRTI will be heading back to Vandy for the Starlink polar launches, and OCISLY and ASOG team tagging with launches. 

They can do polar launches out of Florida with the southern corridor. No need to launch from Vandenberg.
It is true that there are polar launches they can do from Florida now with the new corridor, but they're recently been hiring west coast drone ship recovery personnel.  Example:

https://twitter.com/SpaceCareers/status/1367822234979549186

Watching what jobs they hire for and where they're hiring them can be productive.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/11/2021 01:46 pm

I would hazard a guess that JRTI will be heading back to Vandy for the Starlink polar launches, and OCISLY and ASOG team tagging with launches. 

They can do polar launches out of Florida with the southern corridor. No need to launch from Vandenberg.

Yes, they can fly polar out of FL.  However, with only 2 pads and a busy manifest launching from CA provides a useful third pad and facilities to launch from, it’s a capacity increase.
 
I don’t know the math to know if they can launch more mass from the West Coast, but that seems probable as well.

SS and SH getting into polar orbits from Boca Chica maybe possible, but that mass penalty would be pretty high.

Seems that SS will need to use that East Coast corridor for polar orbits.


Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 02:07 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: HOLLOW on 05/11/2021 02:09 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?
All of the above, except they're probably not going to go faster or higher.

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Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Prae_ on 05/11/2021 02:11 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?

SpaceX has likely done their best to model expected fatigues and changes that will occur over multiple launch cycles, furthermore SN15.2 presents a chance to run a very aggressive test regime that gives them a solid reference point for working out kinks in the launch process as they prepare for rapid re-usability.

The most likely outcome is a replica 10km flight campaign to establish a control, then compare results.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 02:14 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?

SpaceX has likely done their best to model expected fatigues and changes that will occur over multiple launch cycles, furthermore SN15.2 presents a chance to run a very aggressive test regime that gives them a solid reference point for working out kinks in the launch process as they prepare for rapid re-usability.

The most likely outcome is a replica 10km flight campaign to establish a control, then compare results.

What would you consider more aggressive? To me that means using Raptors at higher power settings implying higher speeds/altitude, and maybe doing the landing flip at a lower altitude.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Prae_ on 05/11/2021 02:21 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?

SpaceX has likely done their best to model expected fatigues and changes that will occur over multiple launch cycles, furthermore SN15.2 presents a chance to run a very aggressive test regime that gives them a solid reference point for working out kinks in the launch process as they prepare for rapid re-usability.

The most likely outcome is a replica 10km flight campaign to establish a control, then compare results.

What would you consider more aggressive? To me that means using Raptors at higher power settings implying higher speeds/altitude, and maybe doing the landing flip at a lower altitude.

Aggressive would be a timeline change. Running hardware beyond rated limits is not good field testing for a program that is seeking to replicate success.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 03:11 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?

SpaceX has likely done their best to model expected fatigues and changes that will occur over multiple launch cycles, furthermore SN15.2 presents a chance to run a very aggressive test regime that gives them a solid reference point for working out kinks in the launch process as they prepare for rapid re-usability.

The most likely outcome is a replica 10km flight campaign to establish a control, then compare results.

What would you consider more aggressive? To me that means using Raptors at higher power settings implying higher speeds/altitude, and maybe doing the landing flip at a lower altitude.

Aggressive would be a timeline change. Running hardware beyond rated limits is not good field testing for a program that is seeking to replicate success.

Not sure if you are referring to Raptors running at higher power, but my understanding is that Raptors so far have not been using their full capability to avoid blowing through 10kms. Not only were they being shut down to avoid overshoot, my understanding is that all of them were being throttled the entire flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: volker2020 on 05/11/2021 03:15 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?

I think there are some rather obvious targets:
  - Verify the last result.
  - Improve landing accuracy (the current one, would have been a disaster for a ship landing or even a catching tower).
  - Keep the legs alive (I am personally looking forward to see, if they use the same model again).
  - Keep the telemetries working during the test.

I am quite sure they would love to expand the flight envelop too. Question is, whether there license does allow that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vettedrmr on 05/11/2021 03:21 pm
The legs worked just fine: they're designed to crush, and had a lot more energy absorption available.  They're one-shot legs, so they'll be swapped out for replacements of the same design.

AFAIK, TM worked great throughout the test.  Video, no, but it's not really part of the TM dataset.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cuddihy on 05/11/2021 03:22 pm
How about just doing it in clear weather for a cool video and more telemetry for analysis?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 03:23 pm
How about just doing it in clear weather for a cool video and more telemetry for analysis?

How many scrubs are you willing to endure for that?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 03:34 pm
One thing I'm curious about is whether they will bother removing the Raptors for inspection before reflight?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/11/2021 03:42 pm
One thing I'm curious about is whether they will bother removing the Raptors for inspection before reflight?

I would assume so to check them for any damage. Of course I'm not completely sure of SpaceX's plans for relaunch though.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/11/2021 03:46 pm
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?

One thing they can get from reflying is a treasure of data. I would expect a higher flight if it does indeed fly, maybe around 20kmor so, and faster as well. I think it’s going to be a much more streamlined campaign leading to launch than the first flight.

Right now things to look for will be replacement legs heading to the launch site, and any raptor swaps that occur. Personally I think the raptor that didn’t light on the way down will be swapped, but that’s just speculation on my part.

All in all, if they even get it off the ground, they are proving something huge. If it lands, let’s just say mars is really close  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/11/2021 03:50 pm
One thing I'm curious about is whether they will bother removing the Raptors for inspection before reflight?

I would assume so to check them for any damage. Of course I'm not completely sure of SpaceX's plans for relaunch though.

While visual inspection is important, they have a lot of data on how the engines were working past when the legs of SN15 hit the ground. Take a look at the SSME shutdown sequence for comparison https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39674.0;attach=1448257 (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39674.0;attach=1448257) and you see that things continue for several seconds after the shutdown command is given. Comparing these shutdowns to what occurred during testing at McGregor and during static fires tells you a lot about how the engine was working.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/11/2021 03:56 pm
One thing I'm curious about is whether they will bother removing the Raptors for inspection before reflight?

I would assume so to check them for any damage. Of course I'm not completely sure of SpaceX's plans for relaunch though.

While visual inspection is important, they have a lot of data on how the engines were working past when the legs of SN15 hit the ground. Take a look at the SSME shutdown sequence for comparison https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39674.0;attach=1448257 (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39674.0;attach=1448257) and you see that things continue for several seconds after the shutdown command is given. Comparing these shutdowns to what occurred during testing at McGregor and during static fires tells you a lot about how the engine was working.

Fair point. Flight data is probably the more important prize here given that you can find fixes to problems that inspection may not reveal.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/11/2021 03:59 pm
I don’t think there’s any particular rush to sort out ASDS or the platforms or anywhere for landing of the first few orbital flights, as (according to Elon) it will take a while before the prototypes make it through EDL intact and there is anything left that is capable of landing. Btw, this is the wrong thread to be discussing ASDS or landing platforms, so kindly take it somewhere else and keep this thread for discussion of the actual prototypes being built...
I don't agree bacause also sn8 was expected to do less more than what it did.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: space_snap828 on 05/11/2021 04:08 pm
One thing I'm curious about is whether they will bother removing the Raptors for inspection before reflight?

I would assume so to check them for any damage. Of course I'm not completely sure of SpaceX's plans for relaunch though.

While visual inspection is important, they have a lot of data on how the engines were working past when the legs of SN15 hit the ground. Take a look at the SSME shutdown sequence for comparison https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39674.0;attach=1448257 (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39674.0;attach=1448257) and you see that things continue for several seconds after the shutdown command is given. Comparing these shutdowns to what occurred during testing at McGregor and during static fires tells you a lot about how the engine was working.

Fair point. Flight data is probably the more important prize here given that you can find fixes to problems that inspection may not reveal.
Don't get me wrong, flight data has it's place, but physical inspection is nothing to be scoffed at. One of the things that has likely made Falcon 9 so reliable is that SpaceX can physically see what parts are wearing down so that they can be strengthened or otherwise enhanced. Some issues might not show in the data until it's too late.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/11/2021 04:12 pm

Some issues might not show in the data until it's too late.

Then you’re not looking at the right data.

I understand your point, you don’t know what to  monitor at this point in development, so all kinds of inspections are important . At some point they will get to where they know what is critical, what can only be inspected every tenth flight, and what can be inferred from performance data. But not today.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/11/2021 05:42 pm


IMO the fact that they are lifting sn15 on the pad should not be assumed as a sure reflight. recovering the engines would be exceptionally good or them, so for an  easy process of getting the engines of they are placing it on the pad. Since sn16 is ready there is no reason to expect that sn16 flight preparations wouild take longer than sn15's for a second flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/11/2021 05:55 pm


IMO the fact that they are lifting sn15 on the pad should not be assumed as a sure reflight. recovering the engines would be exceptionally good or them, so for an  easy process of getting the engines of they are placing it on the pad. Since sn16 is ready there is no reason to expect that sn16 flight preparations wouild take longer than sn15's for a second flight.
The thing to look for is new legs.  If new legs get delivered (or if they snuck new legs out and installed them when no one was looking), then (IMO - no insider info!) they're re-flying, as there is no reason to replace the legs otherwise.  Try to keep an eye up the skirt when they do the lift.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Danirode on 05/11/2021 06:19 pm
At the launch pad they have connection for power and telemetry, and plumping, so they can test a bunch of stuff again. Plus, they have room to inspect under the skirt to access the Raptors, and since there was a fire post landing, something got toasted for sure, so they can inspect that.
So IMO putting SN15 on a launch stand doesn't mean automatically that it would fly again (anytime soon anyway).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WindyCity on 05/11/2021 06:24 pm
Another possible objective of a reflight would be an effort to correct whatever caused the post-landing methane fire. Was it expected, a faulty design, or an anomaly?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/11/2021 06:54 pm
Another possible objective of a reflight would be an effort to correct whatever caused the post-landing methane fire. Was it expected, a faulty design, or an anomaly?

There was a discussion about this a few days ago. The most probable thing is that it was expected and caused by the methane still in the plumbing downstream of the valves.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tgr9898 on 05/11/2021 08:10 pm
At the launch pad they have connection for power and telemetry, and plumping, so they can test a bunch of stuff again. Plus, they have room to inspect under the skirt to access the Raptors, and since there was a fire post landing, something got toasted for sure, so they can inspect that.
So IMO putting SN15 on a launch stand doesn't mean automatically that it would fly again (anytime soon anyway).

I'll go with an even simpler idea -

Pad B is the only place to store SN15 with hold-down clamps.  If they take it back to the build site, it's probably going to have to sit outside for a while until SN16 and BNX clears the Highbay.  That means it's exposed to any wind or storm activity on a simple stand.  The sub-oribital pads are a more secure outdoor stand....

Plus they'll need two road closures to move it there & eventually back.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 05/11/2021 08:44 pm
At the launch pad they have connection for power and telemetry, and plumping, so they can test a bunch of stuff again. Plus, they have room to inspect under the skirt to access the Raptors, and since there was a fire post landing, something got toasted for sure, so they can inspect that.
So IMO putting SN15 on a launch stand doesn't mean automatically that it would fly again (anytime soon anyway).

I'll go with an even simpler idea -

Pad B is the only place to store SN15 with hold-down clamps.  If they take it back to the build site, it's probably going to have to sit outside for a while until SN16 and BNX clears the Highbay.  That means it's exposed to any wind or storm activity on a simple stand.  The sub-oribital pads are a more secure outdoor stand....

Plus they'll need two road closures to move it there & eventually back.
Unless they have a definitive plan and they need to actually do something to make that plan come to fruition, its probably best to do nothing as plans seem change on a regular basis. No point moving it unless your sure in case you have to move it back.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: TRS717 on 05/11/2021 09:24 pm
At the launch pad they have connection for power and telemetry, and plumping, so they can test a bunch of stuff again. Plus, they have room to inspect under the skirt to access the Raptors, and since there was a fire post landing, something got toasted for sure, so they can inspect that.
So IMO putting SN15 on a launch stand doesn't mean automatically that it would fly again (anytime soon anyway).
Whether or not there's a notion to fly SN15 again, once mounted on Pad B, I'd imagine we might see her undergoing, at minimum, a cryo test, as a quick & dirty leak check. I'm sure she's fitted with an abundance of strain gauges, but there's really no way to begin determining her fitness for further flight without first investigating whether or not she's still "watertight."
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oersted on 05/11/2021 09:27 pm
It really is quite a testament to the robustness SpaceX wants to achieve that they happily launch test flights through overcast weather.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WindyCity on 05/11/2021 09:30 pm
Another possible objective of a reflight would be an effort to correct whatever caused the post-landing methane fire. Was it expected, a faulty design, or an anomaly?

There was a discussion about this a few days ago. The most probable thing is that it was expected and caused by the methane still in the plumbing downstream of the valves.
Yes, I read that. My opinion is that if such a substantial residual fuel burn-off is expected, then it's a design flaw. I can't understand how a fire burning to such an extent in the engine skirt could have negligible consequences, especially considering rapid reusability.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/11/2021 09:36 pm
Another possible objective of a reflight would be an effort to correct whatever caused the post-landing methane fire. Was it expected, a faulty design, or an anomaly?

There was a discussion about this a few days ago. The most probable thing is that it was expected and caused by the methane still in the plumbing downstream of the valves.
Yes, I read that. My opinion is that if such a substantial residual fuel burn-off is expected, then it's a design flaw. I can't understand how a fire burning to such an extent in the engine skirt could have negligible consequences, especially considering rapid reusability.

The engine bell itself would store quite a bit of methane I would think. Part of the issue was flammable materials as well. They may have to switch to a more fire resistant insulation. It sure looked like it was acting like a wick to any any stray methane, but not sure how much of a difference that made with all the hot engine parts when gas was released.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/11/2021 09:42 pm

Some issues might not show in the data until it's too late.

Then you’re not looking at the right data.

I understand your point, you don’t know what to  monitor at this point in development, so all kinds of inspections are important . At some point they will get to where they know what is critical, what can only be inspected every tenth flight, and what can be inferred from performance data. But not today.

There is quite a bit of data which is pretty much impossible to gather without physical inspection.  For instance, how did the inside of the combustion chamber fare?  All good, or are there spots that are a hair's breadth away from wearing through and causing disaster?  This might be different in flight from the test stand, since the motion of the vehicle will influence things.

There are all sorts of other things that can't be checked without physical inspection, and can't be properly tested on the ground.  What about unexpected wear on the fin actuators?  Cracks in the heat shield tiles that didn't quite result in the tile failing entirely (yet)?  How did all the welds hold up?  The list goes on and on.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Okie_Steve on 05/11/2021 09:45 pm
Each design/build iteration of SS gets closer to the operational version, but only to the point useful for what that version can demonstrate/teach. Early versions had loose cables, now they are in armoured conduits etc. SpaceX Engineers may occasionally make a mistake but they are not idiots. Do not assume that the residual fuel dump seen is a "design flaw", it may just have been good enough for nailing the landing and the hardware to address it "better" will get installed in a later iteration such as SN20. Prior to that it would have just been a waste of time, money and mass.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/11/2021 10:15 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
They picked this size of a drone ship for F9 because they didn't know how accurate they could make F9 landings, and this was the largest practical barge size for a small investment.

As far as it being large enough for Starship. It is certainly large enough. Look at the attached image - The yellow circle alone is ~22 meters across. While Starship has an almost 3x greater diameter than F9, its leg stance is actually narrower (~10m with the current prototype legs)

And as far as weight capacity, these barges usually have capacities in the multiple 1000 ton range.

The only issue would be if the deck is strong enough to handle the landing impact from 6 legs.
There might be some thermal problems too, but nothing insurmountable. Biggest argument against that I can come up with is CoG of the bigger ship in conjunction with going back to manual lash down. They might come out with the new legs before trying for a drone ship landing to spread the load a bit.


If they decide to go for a drone ship landing they would probably have tighter limits on sea state than for F9, especially if they keep the stumpy legs.



Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/11/2021 10:27 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.


With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/11/2021 10:39 pm
Each design/build iteration of SS gets closer to the operational version, but only to the point useful for what that version can demonstrate/teach. Early versions had loose cables, now they are in armoured conduits etc. SpaceX Engineers may occasionally make a mistake but they are not idiots. Do not assume that the residual fuel dump seen is a "design flaw", it may just have been good enough for nailing the landing and the hardware to address it "better" will get installed in a later iteration such as SN20. Prior to that it would have just been a waste of time, money and mass.

I'm not sure where the residual fuel could possibly be removed by any method except dumping it out and letting it burn.  It's cryogenic, so you can't just leave it in the pipes to drain later, and you can't very well suck it back up into the tank.

But we also need to remember just where this fire was.  We're talking about the bottom of a rocket.  It might be best to compare the operating conditions there to the area around the nozzle of an oxyacetelene torch that burns 1,000 liters of fuel per second.  It has to be able to take a little fire.

Concerning the SN10 fire that eventually ended with the tank rupturing, I rather suspect that the hard landing cracked something around the bottom of the tank, and fuel was trickling down into the fire for the entire time.  The tank could not depressurize through this hole because the liquid layer was in the way, and since the heat was gradually boiling it, pressure continued to build up.  As for why they didn't vent the tank, perhaps the impact from the hard landing also rendered the valve inoperational?  I can imagine the fitting being squeezed very hard for an instant as the shock of landing propogated up the walls of the vehicle, and if this warped it, it could have become well and truely jammed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/11/2021 10:50 pm
Given the biggest financial loss of soft landing at sea is the raptors, and they need to test orbital landing soon.

Also given that SpaceX testing philosophy seems to be, if it is physically possible to do something we would like to do, lets give it a good shot and see what we need to do to succeed., then...

Seeing as it is physically possible to land one on a drone ship, it seems like it would be really unlikely that they do not try to land an SS on a drone ship at some point soon.

This would be a high probably in the case that they can't land back at Boca Chica or one of the other landing zones they own. I don't think those oil rigs will be ready in time for early orbital flights. They may not use them anyway, since they would really want to use production vehicles since transporting test vehicles from them would be much more difficult.
A fast SN15 reflight will be interesting. If they can work down to a relatively short turnaround (1-10 days?) it's not impossible that they would hop SS back to BC. Turnaround for a hop seems like it would be less rigorous than for orbital. 


The advantage of this is short term only. It clears the rig for another launch. Hmmm. That gets me thinking.


Long term thinking. If the heart of the concept is rapid turnaround and orbital launch and recovery has to be off shore, it starts to make sense to find a way to snatch SS out of the air. I don't think there's enough room on a rig to handle both SS and SH at the same time any other way. Unless the rigs they're working on are just teeny little PoC units with bigger ones to come.


A long time ago I got govt surplus circulars. I think it had aircraft carriers on it.  ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: WindyCity on 05/11/2021 11:55 pm
Each design/build iteration of SS gets closer to the operational version, but only to the point useful for what that version can demonstrate/teach. Early versions had loose cables, now they are in armoured conduits etc. SpaceX Engineers may occasionally make a mistake but they are not idiots. Do not assume that the residual fuel dump seen is a "design flaw", it may just have been good enough for nailing the landing and the hardware to address it "better" will get installed in a later iteration such as SN20. Prior to that it would have just been a waste of time, money and mass.

I'm not sure where the residual fuel could possibly be removed by any method except dumping it out and letting it burn.  It's cryogenic, so you can't just leave it in the pipes to drain later, and you can't very well suck it back up into the tank.

But we also need to remember just where this fire was.  We're talking about the bottom of a rocket.  It might be best to compare the operating conditions there to the area around the nozzle of an oxyacetelene torch that burns 1,000 liters of fuel per second.  It has to be able to take a little fire.
Might they be able to minimize the amount of residual fuel somehow? Or divert it from the hot engines upon shutdown? Imagine the size of a methane residual fuel fire burning at the bottom of a 28+ Raptor-outifitted SH. Of course if it's caught on the launch tower, they'd probably have a nifty fire suppression system installed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 12:01 am
Most discussion here is speculation, not statement of observation. If speculation was considered off topic, 90% of discussion here would be off topic.

If it's speculation ABOUT THE PROTOTYPES, it's on-topic. But if it's more arm-chair engineer/hand-waving mumblety-mumblety-ELON!!! talk, it's not. There are specific threads for all kinds of those rabbit-hole topics: general engineering, facilities and fleets, landing discussion, trajectory planning and brainstorming, landing legs/feet, repurposed oil rig platforms, ASDS's ...

Every single one of those above - and dozens more - have specific topics. The fact that people are too lazy to actually go find them and use them doesn't make talking about them HERE in this thread "on-topic" by any stretch of imagination.
As the builds progress the 'next step' options narrow and slide into on topic. The edges are edges of convenience and move with circumstances. Pluto is a great example of this.


If BN3 and SN20 were getting ready for flight, BN3 had different legs and an ASDS were repositioning to the Gulf, would it be OT here? The edge moves. We (all of us) have different takes on where it is.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 12:08 am

I would hazard a guess that JRTI will be heading back to Vandy for the Starlink polar launches, and OCISLY and ASOG team tagging with launches. 

They can do polar launches out of Florida with the southern corridor. No need to launch from Vandenberg.
I think there's a payload penalty for that. They've got a lot of launches ahead of them and using Vandy takes some of the pad scheduling pressure off.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 12:13 am
From SN15 update, it looks like it's heading back to pad B for relaunch. I wonder what the test objectives will be?

Improving landing targeting? Higher or supersonic flight? Prove out reuse? Optimizing launch sequencing?
Speed up turnaround?  Already got safing down a lot quicker.


And everything you say.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 12:22 am


IMO the fact that they are lifting sn15 on the pad should not be assumed as a sure reflight. recovering the engines would be exceptionally good or them, so for an  easy process of getting the engines of they are placing it on the pad. Since sn16 is ready there is no reason to expect that sn16 flight preparations wouild take longer than sn15's for a second flight.
We know that 16 looks complete but do we know all the internals are done? 16 will need a pressure test to catch up to 15. There is pad A and they had 5 & 6 mounted up at the same time. Conclusion: Insufficient Data.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 05/12/2021 02:14 am
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.

With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.
There is a large "nose-shaped" CNC in the windbreak which is setup for either chomper and/or a nosecone redesign.  The nosecone structural test stand is obviously a path towards testing nosecone designs.  It seems clear that they are in fact working towards chomper (or its replacement) even though we haven't seen any prototypes yet.

As others have pointed out, initial tests of maneuvers for orbital refueling can be carried out after satellites have been launched.  It is not either or.

Starship is an important part of the Starlink program which has hard deadlines from the FCC for minimum satellites launched.  They cannot let Starlink slide and the cost of using more frequent Falcon launches in place of Starship seems like something they would prefer to avoid.  Also, it seems it would be hard to get commercial contracts is you are unwilling to launch your own satellites in Starship.

All signs point to Starlink cargo launches on Starship as soon as possible and I assume they are willing to lose a certain number of their relatively cheap satellites in order to switch over to Starship sooner rather than later.

EDIT:  They also have a limited number of orbital launches per year (10-12?) initially, so they will obviously want to maximize the value of each one.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rix4 on 05/12/2021 05:44 am
Do we know what was tested with nosecone test rig?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Rossco on 05/12/2021 07:33 am
I've read quite a bit about how Starship 'only just made the pad' and 'missed its target' etc, however I wonder if this was possibly intentional to try and mitigate any damage to the various hardware around the pad - including the nose torture chamber - should of SN15 experienced a RUD?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kazioo on 05/12/2021 10:59 am
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.

With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.
There is a large "nose-shaped" CNC in the windbreak which is setup for either chomper and/or a nosecone redesign.  The nosecone structural test stand is obviously a path towards testing nosecone designs.  It seems clear that they are in fact working towards chomper (or its replacement) even though we haven't seen any prototypes yet.

As others have pointed out, initial tests of maneuvers for orbital refueling can be carried out after satellites have been launched.  It is not either or.

Starship is an important part of the Starlink program which has hard deadlines from the FCC for minimum satellites launched.  They cannot let Starlink slide and the cost of using more frequent Falcon launches in place of Starship seems like something they would prefer to avoid.  Also, it seems it would be hard to get commercial contracts is you are unwilling to launch your own satellites in Starship.

All signs point to Starlink cargo launches on Starship as soon as possible and I assume they are willing to lose a certain number of their relatively cheap satellites in order to switch over to Starship sooner rather than later.

EDIT:  They also have a limited number of orbital launches per year (10-12?) initially, so they will obviously want to maximize the value of each one.

These satellites are relatively cheap per unit compared to traditional GEO satellites, but they are not that cheap when you have up to 400 of them in the fairing.

The first Falcon Heavy flight had significant risk of RUD, but the first orbital SH flight will be muuuch more rushed, so I assume the risk factor of not making the orbit will be quite big. It may not be worth risking hundreds of satellites in a launch of a prototype quickly made in a few months.

Another factor is that empty Starship without cargo + no RTLS + lower orbit may allow them to use less fuel and fewer Raptors, so there is more to it than just giving up on "free" opportunity.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hkultala on 05/12/2021 11:29 am
Another possible objective of a reflight would be an effort to correct whatever caused the post-landing methane fire. Was it expected, a faulty design, or an anomaly?

There was a discussion about this a few days ago. The most probable thing is that it was expected and caused by the methane still in the plumbing downstream of the valves.
Yes, I read that. My opinion is that if such a substantial residual fuel burn-off is expected, then it's a design flaw. I can't understand how a fire burning to such an extent in the engine skirt could have negligible consequences, especially considering rapid reusability.

Have you made any calcualtions to support your point?

Each Raptor engine can burn over hundred kilograms of methane per second.

That fire in the videos burned maybe few of kilograms of methane, so maybe something like the fuel needed for 1/100th of a second.

Claiming that leaving this kind or propellant margin is a design flaw is quite clueless.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/12/2021 12:34 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.

With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.
There is a large "nose-shaped" CNC in the windbreak which is setup for either chomper and/or a nosecone redesign.  The nosecone structural test stand is obviously a path towards testing nosecone designs.  It seems clear that they are in fact working towards chomper (or its replacement) even though we haven't seen any prototypes yet.

As others have pointed out, initial tests of maneuvers for orbital refueling can be carried out after satellites have been launched.  It is not either or.

Starship is an important part of the Starlink program which has hard deadlines from the FCC for minimum satellites launched.  They cannot let Starlink slide and the cost of using more frequent Falcon launches in place of Starship seems like something they would prefer to avoid.  Also, it seems it would be hard to get commercial contracts is you are unwilling to launch your own satellites in Starship.

All signs point to Starlink cargo launches on Starship as soon as possible and I assume they are willing to lose a certain number of their relatively cheap satellites in order to switch over to Starship sooner rather than later.

EDIT:  They also have a limited number of orbital launches per year (10-12?) initially, so they will obviously want to maximize the value of each one.

These satellites are relatively cheap per unit compared to traditional GEO satellites, but they are not that cheap when you have up to 400 of them in the fairing.

The first Falcon Heavy flight had significant risk of RUD, but the first orbital SH flight will be muuuch more rushed, so I assume the risk factor of not making the orbit will be quite big. It may not be worth risking hundreds of satellites in a launch of a prototype quickly made in a few months.

Another factor is that empty Starship without cargo + no RTLS + lower orbit may allow them to use less fuel and fewer Raptors, so there is more to it than just giving up on "free" opportunity.
The fact that early orbital flights will have less than full compliment of engines & propellant pretty much render impossible for them to load 400 sats, maybe even 60

Even in a full operational mode (all 28 engines & full propellant), I doubt that they will put 400 per launch. It need to spread out over multiple inclinations
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KBK on 05/12/2021 01:19 pm
The oil rigs main purpose is for orbital launch. They would not likely take off from a droneship, especially a booster, but may be used for landing and bring to port. Also, as far as I know, we haven't seen ASOG which may be bigger than current drone ships.
Droneship is too small (both size and acceptable weight -wise).
Why do you think they land F9 stage on it, even though stage's footprint is so small compared to size of barge?
They picked this size of a drone ship for F9 because they didn't know how accurate they could make F9 landings, and this was the largest practical barge size for a small investment.

As far as it being large enough for Starship. It is certainly large enough. Look at the attached image - The yellow circle alone is ~22 meters across. While Starship has an almost 3x greater diameter than F9, its leg stance is actually narrower (~10m with the current prototype legs)

And as far as weight capacity, these barges usually have capacities in the multiple 1000 ton range.

The only issue would be if the deck is strong enough to handle the landing impact from 6 legs.
There might be some thermal problems too, but nothing insurmountable. Biggest argument against that I can come up with is CoG of the bigger ship in conjunction with going back to manual lash down. They might come out with the new legs before trying for a drone ship landing to spread the load a bit.


If they decide to go for a drone ship landing they would probably have tighter limits on sea state than for F9, especially if they keep the stumpy legs.

Possibly with electrically driven damped outriggers for stability and motion control. However, there is something to be said for using a bigger boat. Inertial mass, for one. A combination, possibly. The biggest problem, as usual, is the initial transient of contact and deceleration. Second..probably the load stability in wind and sea conditions.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StefsEngineering on 05/12/2021 04:14 pm
Impressive crane, I assume it will get a similar configuration to this crane. This is the same one and is used in Rotterdam to assemble the largest windturibne in the world (rotor diameter 220 meter) Its generator housing is 150m off the ground so similar height to the top of the OLIT.

(https://images-global.nhst.tech/image/Wms0M1VtY2oycjlOd1N5d2RoUTM5K2laQnFGOVNBWS81bFFjeHVML3hLQT0=/nhst/binary/7e4531fe37e60f9d67fe233d9cc40053)

The nacelle that they had to lift is quite a beast as well:

(https://cleantechnica.com/files/2019/07/ge_haliade-x_nacelle_4_0.jpg)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StefsEngineering on 05/12/2021 04:27 pm
oh nevermind the nacelle was lifted in a different configuration.

(https://ponderaconsult.com/uk/wp-content/uploads/sites/3/2019/09/Nacelle-2.jpg)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/12/2021 04:35 pm
oh nevermind the nacelle was lifted in a different configuration.

(https://ponderaconsult.com/uk/wp-content/uploads/sites/3/2019/09/Nacelle-2.jpg)

Interesting...  That would require some pretty close coordination.  I wonder if the two cranes are synced together and software controlled, so operated by only one person?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 05/12/2021 05:08 pm
Hello space enthusiasts!
With the kind permission of Chris B. I may present you from today also here my 3D construction progress updates of the starbase in Boca Chica.
Thank you very much.
I am happy to be a small part of this great community.
Here is my update for today:
https://youtu.be/ZBewupM613U

Great first post! Looking forward to seeing more of your renderings!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lobo on 05/12/2021 05:39 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.


With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.

I would guess this too.  "Chomper", if that's still the way they want to go, would be down the road.  That configuration would really be to replace F9 missions, and F9 is their cash cow right now and they have a lot of investment into it's current infrastructure . They have a ways to go and other priorities before they get to that point where it's needed.

Quote
I'm guessing the nosecone torture rack is a lead up to a cargo nose
.

Cargo?  You mean like in support of a lunar mission?  What sort of cargo and to where?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: robot_enthusiast on 05/12/2021 05:43 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.


With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.

I would guess this too.  "Chomper", if that's still the way they want to go, would be down the road.  That configuration would really be to replace F9 missions, and F9 is their cash cow right now and they have a lot of investment into it's current infrastructure . They have a ways to go and other priorities before they get to that point where it's needed.

Quote
I'm guessing the nosecone torture rack is a lead up to a cargo nose
.

Cargo?  You mean like in support of a lunar mission?  What sort of cargo and to where?
The cargo is obviously to space, meaning the version with a payload door (AKA "chomper").
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/12/2021 05:44 pm
I agree that a chomper nose should be coming out soon and going into the cage.

Now that they have the test rig, they have some test data (baseline) and can torment the crap out of future nose options.  Especially chomper.

I think a chomper nose is also going to get a lift test simulated a fully weighted SS, since they pick it up by the nose.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lobo on 05/12/2021 06:01 pm

The cargo is obviously to space, meaning the version with a payload door (AKA "chomper").

I guess what I mean is the nosecone in the rig is contiguous, so it's obviously not a "chomper".  So I wasn't sure what OTV meant by "cargo".  If it's not a chomper then there would be no way to deploy cargo in space, so maybe he meant for a cargo LSS or something.  I was confused so I asked.

Chomper by it's nature would need to be structurally very different than the standard nosecone, as it would have a very large cargo door in it.
So, they may be just testing the test rig on a standard nosecone to make sure it's working as designed, and then they'll build a chomper nosecone and put in there for testing.
Or it's just to test the first standard nosecones to make sure they won't warp or deform during reentry which would cause misalignment of the heat tiles, and thus likely a catastrophic failure.  It's not just about keeping the nosecone from completely bucking (although that's important to test for too), but not even deforming to create tile alignment issues.  As the nosecone is hollow and not supported by pressurized tanks like the barrel of Starship is.  So it's both the point of highest structural forces during reentry, and also the weakest part of Starship.  So they need to make sure it's adequately rigid and supported.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/12/2021 06:49 pm

The cargo is obviously to space, meaning the version with a payload door (AKA "chomper").

I guess what I mean is the nosecone in the rig is contiguous, so it's obviously not a "chomper".  So I wasn't sure what OTV meant by "cargo".  If it's not a chomper then there would be no way to deploy cargo in space, so maybe he meant for a cargo LSS or something.  I was confused so I asked.

Chomper by it's nature would need to be structurally very different than the standard nosecone, as it would have a very large cargo door in it.
So, they may be just testing the test rig on a standard nosecone to make sure it's working as designed, and then they'll build a chomper nosecone and put in there for testing.
Or it's just to test the first standard nosecones to make sure they won't warp or deform during reentry which would cause misalignment of the heat tiles, and thus likely a catastrophic failure.  It's not just about keeping the nosecone from completely bucking (although that's important to test for too), but not even deforming to create tile alignment issues.  As the nosecone is hollow and not supported by pressurized tanks like the barrel of Starship is.  So it's both the point of highest structural forces during reentry, and also the weakest part of Starship.  So they need to make sure it's adequately rigid and supported.

I agree.

The cargo door will probably also add weakness to the nosecone. It isn't a complicated part, but simple-looking  thing may become quite difficult.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/12/2021 06:53 pm
Speaking about the fire, as pointed out it isn't a big deal for the skirt.

I think that it will be worked out, making it at least shorter. On Moon and Mars it won't happen, and on Earth they have plenty of GSE to cool the skirt. Moreover, the fire isn't a problem, because it burned full duration, since water doesn't do anything to gas fires, but it only cools down.

Someone said that superheavy will have a problem of landing fires ith its 28 engines, but on the landing it will use only three  (or a couple more)IIUC.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StuffOfInterest on 05/12/2021 06:56 pm
Impressive crane, I assume it will get a similar configuration to this crane. This is the same one and is used in Rotterdam to assemble the largest windturibne in the world (rotor diameter 220 meter) Its generator housing is 150m off the ground so similar height to the top of the OLIT.
Great example of what we will likely see on site.  Only thing is that this really belongs over on the launch site (https://forum.nasaspaceflight.com/index.php?topic=49086.0) thread rather than the prototype's discussion thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 07:43 pm
oh nevermind the nacelle was lifted in a different configuration.

(https://ponderaconsult.com/uk/wp-content/uploads/sites/3/2019/09/Nacelle-2.jpg)

Interesting...  That would require some pretty close coordination.  I wonder if the two cranes are synced together and software controlled, so operated by only one person?
Good crane operators are like gold. Two top notch operators, a top notch operator spotting on the ground and a radio link should do it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 07:47 pm
Is there any new info on the elephant in the room - the "chomper" nose cone? With an orbital flight so close, that seems like a major thing to work out, unless they're not planning to deploy a payload on the first flight, which would seem like a wasted opportunity to put some Starlinks up.

Unless they're just going to cut a slit in the side of a nose cone and shoot the sats out like an electronic card shuffler...
I'm guessing the nosecone torture rack is a lead up to a cargo nose. And I don't think we've seen anything about the chomper lately. As fast as things change at SX, they may be looking at something different.


With lunar missions on their plate they may be giving refueling a higher priority than cargo. Stay tuned.

I would guess this too.  "Chomper", if that's still the way they want to go, would be down the road.  That configuration would really be to replace F9 missions, and F9 is their cash cow right now and they have a lot of investment into it's current infrastructure . They have a ways to go and other priorities before they get to that point where it's needed.

Quote
I'm guessing the nosecone torture rack is a lead up to a cargo nose
.

Cargo?  You mean like in support of a lunar mission?  What sort of cargo and to where?
Cargo as in StarLink tomorrow and anything else that needs deployment further down the road. There is already interest in SS for outsized science missions.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/12/2021 07:52 pm
Speaking about the fire, as pointed out it isn't a big deal for the skirt.

I think that it will be worked out, making it at least shorter. On Moon and Mars it won't happen, and on Earth they have plenty of GSE to cool the skirt. Moreover, the fire isn't a problem, because it burned full duration, since water doesn't do anything to gas fires, but it only cools down.

Someone said that superheavy will have a problem of landing fires ith its 28 engines, but on the landing it will use only three  (or a couple more)IIUC.
It's a problem simply because people won't want to get on board a craft that goes on fire every time it lands.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/12/2021 07:57 pm
Speaking about the fire, as pointed out it isn't a big deal for the skirt.

I think that it will be worked out, making it at least shorter. On Moon and Mars it won't happen, and on Earth they have plenty of GSE to cool the skirt. Moreover, the fire isn't a problem, because it burned full duration, since water doesn't do anything to gas fires, but it only cools down.

Someone said that superheavy will have a problem of landing fires ith its 28 engines, but on the landing it will use only three  (or a couple more)IIUC.
It's a problem simply because people won't want to get on board a craft that goes on fire every time it lands.
speak for yourself!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 05/12/2021 07:58 pm
Speaking about the fire, as pointed out it isn't a big deal for the skirt.

I think that it will be worked out, making it at least shorter. On Moon and Mars it won't happen, and on Earth they have plenty of GSE to cool the skirt. Moreover, the fire isn't a problem, because it burned full duration, since water doesn't do anything to gas fires, but it only cools down.

Someone said that superheavy will have a problem of landing fires ith its 28 engines, but on the landing it will use only three  (or a couple more)IIUC.
It's a problem simply because people won't want to get on board a craft that goes on fire every time it lands.
It won’t exist by the time the final article appears. It was indicated in the SN15 live stream via John that improvements to starship will be made to avoid fires. They’ll know it’s an item to work on, but whilst making this things reliable; it’s a less priority thing to fix.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 05/12/2021 08:06 pm
Speaking about the fire, as pointed out it isn't a big deal for the skirt.

I think that it will be worked out, making it at least shorter. On Moon and Mars it won't happen, and on Earth they have plenty of GSE to cool the skirt. Moreover, the fire isn't a problem, because it burned full duration, since water doesn't do anything to gas fires, but it only cools down.

Someone said that superheavy will have a problem of landing fires ith its 28 engines, but on the landing it will use only three  (or a couple more)IIUC.
It's a problem simply because people won't want to get on board a craft that goes on fire every time it lands.
Well its going to go on fire when it takes off.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/12/2021 08:14 pm

The cargo is obviously to space, meaning the version with a payload door (AKA "chomper").

I guess what I mean is the nosecone in the rig is contiguous, so it's obviously not a "chomper".  So I wasn't sure what OTV meant by "cargo".  If it's not a chomper then there would be no way to deploy cargo in space, so maybe he meant for a cargo LSS or something.  I was confused so I asked.

Chomper by it's nature would need to be structurally very different than the standard nosecone, as it would have a very large cargo door in it.
So, they may be just testing the test rig on a standard nosecone to make sure it's working as designed, and then they'll build a chomper nosecone and put in there for testing.
Or it's just to test the first standard nosecones to make sure they won't warp or deform during reentry which would cause misalignment of the heat tiles, and thus likely a catastrophic failure.  It's not just about keeping the nosecone from completely bucking (although that's important to test for too), but not even deforming to create tile alignment issues.  As the nosecone is hollow and not supported by pressurized tanks like the barrel of Starship is.  So it's both the point of highest structural forces during reentry, and also the weakest part of Starship.  So they need to make sure it's adequately rigid and supported.
All the above. Using a 'standard' nosecone gives a baseline. Modeling gives an approximation of the impact a hatch would have. Then twisting the crap out of a hatched prototype validates the model.


A hatched version (chomper or other design) might not be that different a build. There will be obvious differences but any internal reinforcement can be carried over a hatch intrusion with proper latching. Tricky and difficult but not something that's never been done. The hardest part is thermal causing excessive misalignment when relatching. Solution: wait until in night side shadow or orient for even thermal/cold soak.


The latches on a truck trailer door can live with quite a bit of misalignment and will draw everything back into alignment with enough preload (right word?) to make a strong structure. Example only. Not necessarily the best solution.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Coopman0 on 05/12/2021 09:34 pm
Possibly a SN15 relaunch?  ::)  Fingers crossed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sdub on 05/13/2021 02:28 am
Speaking about the fire, as pointed out it isn't a big deal for the skirt.

I think that it will be worked out, making it at least shorter. On Moon and Mars it won't happen, and on Earth they have plenty of GSE to cool the skirt. Moreover, the fire isn't a problem, because it burned full duration, since water doesn't do anything to gas fires, but it only cools down.

Someone said that superheavy will have a problem of landing fires ith its 28 engines, but on the landing it will use only three  (or a couple more)IIUC.
It's a problem simply because people won't want to get on board a craft that goes on fire every time it lands.

If they plan on catching Starship rather than landing it at ground level, as has been suggested, then the methane would not accumulate between the skirt and the ground and it may just dissipate into the air.  Sure, it's not ideal being a greenhouse gas, but it sure wouldn't cause a fire.  Of course, on Mars or the moon there is no oxidizer available and with the low atmospheric pressure it likely escapes more quickly anyway.

Best part is no part....
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 05/13/2021 12:26 pm
Or they could just put some vent holes/doors in the skirt.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/13/2021 06:07 pm
Or they could just put some vent holes/doors in the skirt.

Why should that solve the issue? Th skirt is already open in the bottom.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nadir on 05/13/2021 06:29 pm
Or they could just put some vent holes/doors in the skirt.

Why should that solve the issue? Th skirt is already open in the bottom.

Methane gas is lighter  than air and it will rise in the skirt out the holes
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/13/2021 06:44 pm
Or they could just put some vent holes/doors in the skirt.

Why should that solve the issue? Th skirt is already open in the bottom.

Methane gas is lighter  than air and it will rise in the skirt out the holes

Yes, but it would still catch fire, even if it exits, expecially if exiting it passes next the raptors.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/13/2021 08:46 pm
Not surprisingly the exciting new Starship news (details of first orbital flight) is being discussed in multiple places.

The topic deserves a dedicated thread:  https://forum.nasaspaceflight.com/index.php?topic=53846.0

It’s in the SpaceX missions section of the forum.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: oldAtlas_Eguy on 05/13/2021 09:00 pm
I did a quick run through the numbers to see what a possible min set of engines could be and the one that fits is a minimum number of 23 engines. In the case of 18, 23, or 28 (max). These numbers are due to the engine arrangements of 20 engines in 2 outer rings. Such that for thrust balancing at liftoff you would need 5 engine at least in a particular ring. It will fit the numbers and get  the SS into orbit. The SS at staging will be moving at ~1.5km/s. Much slower than an F9 S1. So reentry of the SH will not be that rough. SS will provide over 7km/s of DV since it will not likely be carrying payload of any significance.

A 23 engined SH is 10 to 11Mlbf liftoff. depending on just how high the thrust fixed gimbal engine has managed to achieve.

A side NOTE: a Tesla vehicle is only a few of tons. So they have a Tesla inside and it would still not make much of an impact on the DV.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 05/13/2021 10:06 pm
SpaceX posts compilation video of SN15 flight:

https://www.youtube.com/watch?v=7CZTLogln34

Alas, no video from on-board memory systems, just cuts from what was received over the air.

It appears the early part of flip has another half seconds of good video that I hadn't seen elsewhere.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: daavery on 05/13/2021 10:57 pm
I did a quick run through the numbers to see what a possible min set of engines could be and the one that fits is a minimum number of 23 engines. In the case of 18, 23, or 28 (max). These numbers are due to the engine arrangements of 20 engines in 2 outer rings. Such that for thrust balancing at liftoff you would need 5 engine at least in a particular ring. It will fit the numbers and get  the SS into orbit. The SS at staging will be moving at ~1.5km/s. Much slower than an F9 S1. So reentry of the SH will not be that rough. SS will provide over 7km/s of DV since it will not likely be carrying payload of any significance.

A 23 engined SH is 10 to 11Mlbf liftoff. depending on just how high the thrust fixed gimbal engine has managed to achieve.

A side NOTE: a Tesla vehicle is only a few of tons. So they have a Tesla inside and it would still not make much of an impact on the DV.

everything i have seen, including the BN1 outer thrust ring shows 1 ring of 20 engines not 2 staggered rows
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/14/2021 04:38 am
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?

The background music was refreshing.  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Cheapchips on 05/14/2021 07:49 am
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?


Until we get a that better look, we don't know where the plumping goes.  Maybe something to do with routing pipes and wiring? 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CMac on 05/14/2021 08:46 am
On twitter (via Scott Manley) SH test flight paths are shown. One just out over sea at Boca with parabolic return to land in sea off coast. The 2nd to go (nearly?) orbital and reenter just north of Hawaii.
If the launch early morning in Boca, the reentry over Hawaii would still be dark - great for viewing reentry but not so good to observe the decent to splashdown. I suppose they'll aim for delight splashdown.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CMac on 05/14/2021 09:58 am
On twitter (via Scott Manley) SH test flight paths are shown. One just out over sea at Boca with parabolic return to land in sea off coast. The 2nd to go (nearly?) orbital and reenter just north of Hawaii.
If the launch early morning in Boca, the reentry over Hawaii would still be dark - great for viewing reentry but not so good to observe the decent to splashdown. I suppose they'll aim for delight splashdown.
I misunderstood: it's one launch with SH return to Boca and SS reentry at Hawaii
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/14/2021 10:03 am
On twitter (via Scott Manley) SH test flight paths are shown. One just out over sea at Boca with parabolic return to land in sea off coast. The 2nd to go (nearly?) orbital and reenter just north of Hawaii.
If the launch early morning in Boca, the reentry over Hawaii would still be dark - great for viewing reentry but not so good to observe the decent to splashdown. I suppose they'll aim for delight splashdown.

There is this thread to comment about this orbital test flight in "SpaceX Missions Section "

https://forum.nasaspaceflight.com/index.php?topic=53846.100

So today there are road closures. SN16 rollout?. We'll see.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 05/14/2021 10:34 am
Or they could just put some vent holes/doors in the skirt.

Why should that solve the issue? Th skirt is already open in the bottom.

Methane gas is lighter  than air and it will rise in the skirt out the holes

Yes, but it would still catch fire, even if it exits, expecially if exiting it passes next the raptors.


You mean like it does now?  Right now it can accumulate in the engine compartment, and is contained by the skirt, just waiting to burn.  Add vent holes toward the top of the skirt so it can go up and out, AWAY from the nozzles.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 05/14/2021 10:38 am
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU (https://youtu.be/VkA7Rja2sAU)
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?

The background music was refreshing.  :)


I am surprised at the kink in the legs.  Isn't that a natural weak spot?   ???
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: uhuznaa on 05/14/2021 10:43 am

The cargo is obviously to space, meaning the version with a payload door (AKA "chomper").

I guess what I mean is the nosecone in the rig is contiguous, so it's obviously not a "chomper".  So I wasn't sure what OTV meant by "cargo".  If it's not a chomper then there would be no way to deploy cargo in space, so maybe he meant for a cargo LSS or something.  I was confused so I asked.

Chomper by it's nature would need to be structurally very different than the standard nosecone, as it would have a very large cargo door in it.
So, they may be just testing the test rig on a standard nosecone to make sure it's working as designed, and then they'll build a chomper nosecone and put in there for testing.
Or it's just to test the first standard nosecones to make sure they won't warp or deform during reentry which would cause misalignment of the heat tiles, and thus likely a catastrophic failure.  It's not just about keeping the nosecone from completely bucking (although that's important to test for too), but not even deforming to create tile alignment issues.  As the nosecone is hollow and not supported by pressurized tanks like the barrel of Starship is.  So it's both the point of highest structural forces during reentry, and also the weakest part of Starship.  So they need to make sure it's adequately rigid and supported.

I'm wondering if they will want to build an "universal" cargo version right away or if they will build a custom Starlink launcher first. Because there're really not that many (if any) potential huge monolithic payloads to LEO right now that would require a full-on chomper. For Starlink something like two rows of smaller payload doors would be sufficient and much, much simpler from a structural POV.


Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 05/14/2021 02:44 pm
I'm wondering if they will want to build an "universal" cargo version right away or if they will build a custom Starlink launcher first. Because there're really not that many (if any) potential huge monolithic payloads to LEO right now that would require a full-on chomper. For Starlink something like two rows of smaller payload doors would be sufficient and much, much simpler from a structural POV.
Interesting.  They have been planning on the ability to rotate the payload adapter "to allow each satellite to  separate with maximum clearance."  So maybe a single smaller door large enough to separate one stack of Starlink and then rotate the adapter for the next stack.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Crispy on 05/14/2021 03:00 pm
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU (https://youtu.be/VkA7Rja2sAU)
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?

The background music was refreshing.  :)


I am surprised at the kink in the legs.  Isn't that a natural weak spot?   ???
My thought is that the original tilted legs were ordered built before the design was frozen. For some sort of schedule or cost reason, they went ahead based on their best information at the time. Since then, they've decided they need an extra 4m or so of height, hence these extension pieces. We'll know for sure when pad B comes along...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/14/2021 03:01 pm
I’m calling it. We’re now at the point where people paying attention who consider Starship not a real thing that will happen are being clearly self-delusional. Right now is that point.

The whole “neener neener it hasn’t launched to orbit yet, any event in the future can be considered impossible and/or extremely unlikely until it happens and then I’ll never admit I was being unreasonable” argument needs a fancy Latin name because it’s super common on the Internet and really annoying.

(We had passed that point for SLS sometime before or after the green run... it’s clear SLS is gonna launch and will probably work, and someone suggesting otherwise is self-delusional.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 05/14/2021 03:08 pm
  Upcoming road closure seems like a good opportunity to move the beefy SPMT transporter now that SN15 has been offloaded. Will this transporter be used to transport SN16 to launch pad? Or is it primarily for post landing tasks?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/14/2021 03:09 pm
I’m calling it. We’re now at the point where people paying attention who consider Starship not a real thing that will happen are being clearly self-delusional. Right now is that point.

The whole “neener neener it hasn’t launched to orbit yet, any event in the future can be considered impossible and/or extremely unlikely until it happens and then I’ll never admit I was being unreasonable” argument needs a fancy Latin name because it’s super common on the Internet and really annoying.

(We had passed that point for SLS sometime before or after the green run... it’s clear SLS is gonna launch and will probably work, and someone suggesting otherwise is self-delusional.)
Hey I have a phone call here from 2019, it wants to chat with you.

But I also have a call on the other line from 2022 it is saying nothing has changed.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/14/2021 03:11 pm
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU (https://youtu.be/VkA7Rja2sAU)
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?

The background music was refreshing.  :)


I am surprised at the kink in the legs.  Isn't that a natural weak spot?   ???
My thought is that the original tilted legs were ordered built before the design was frozen. For some sort of schedule or cost reason, they went ahead based on their best information at the time. Since then, they've decided they need an extra 4m or so of height, hence these extension pieces. We'll know for sure when pad B comes along...
Hey what it some crazy how the straight segments go inside the launch table?  (As if there are holes on the bottom).

Except of course in that case why not put those tube inside the table already..

Do the heights match even?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 05/14/2021 03:27 pm
oh nevermind the nacelle was lifted in a different configuration.

(https://ponderaconsult.com/uk/wp-content/uploads/sites/3/2019/09/Nacelle-2.jpg)

Interesting...  That would require some pretty close coordination.  I wonder if the two cranes are synced together and software controlled, so operated by only one person?
Good crane operators are like gold. Two top notch operators, a top notch operator spotting on the ground and a radio link should do it.

It's actually more complicated than that when balancing a dual lift.  Sometimes they have remote telemetry on angle of the spreader bar, sometimes they have a remote spotter far enough away to see the angle and help one of the operators slow down or speed up, and they *always* have someone up-tower controlling the lift via radio when the nacelle gets to the tower height.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/14/2021 06:12 pm
From one of Mary’s latest pics. I believe we have a landing leg there! Hard to see on all the other sides if they are there, but is for sure there where I circled.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KilroySmith on 05/14/2021 06:29 pm
I think that’s just the forked Mount that the leg attaches to.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/15/2021 12:04 am
I think that’s just the forked Mount that the leg attaches to.

C'mon, the landing wasn't hard, the mount shouldn't be forked...  :P
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Bob Shaw on 05/15/2021 12:11 am
I think that’s just the forked Mount that the leg attaches to.

C'mon, the landing wasn't hard, the mount shouldn't be forked...  :P



Dare I say 'Icehole'?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 05/15/2021 09:27 am
  Recent pictures from Bocachicagal in the 'Boca Chica Master Update' thread show the extent of some of the testing the nose cone article went through. While it was in the 'halo' test device the nose cone looked relatively unscathed, but that was deceiving with bright overhead sunshine and the halo distracting the eye. Out of the cage and with some indirect lighting shows a much different story. It looks like the loads from the internal hydraulic ram and the fin structures did a number on the steel. As best as I can tell, those areas would be between the fins on the leeward side during re-entry. Seeing this kind of abuse would indicate that the design/test teams got some important data from the campaign.

  The dents, folds, and creases can be seen in earlier pictures of the nose cone while it was in the testing rig, but one has to know just where to look and the indications are subtle with bright outdoor lighting. Review pictures on page 75, post #1490 of the 'Boca Chica Production Update thread' to test your eye for details.

  Below are two pics, one is a slight enlargement to help see the deformation that occurred, and the other is a copy of the Bocachicagal original (_DSC4709 (2).JPG) so that folks can see all the gory details up close. The damage is not seen easily until you zoom into the original.

  Really important photo to show results of the testing process. Many thanks to Bocachicagal for capturing this one!

  Off topic final thought - with the protest filed by Blue Origin and Dynetics regarding the HLS award, seeing test articles being put through the ringer says a lot about where the different programs are in regards to hardware. Yes, the HLS article will not have fins or need this kind of stress test, but the results can still inform design decisions about an HLS article. The more data the better.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 05/15/2021 01:23 pm
As best as I can tell, those areas would be between the fins on the leeward side during re-entry.
Exactly where the clamshell door would be.  The problem with destructive tests is we don't know if they pushed it beyond their design constraints, but if they decide they need more strength in that area, we may see a smaller door for the first cargo missions.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 05/15/2021 01:48 pm
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?

The background music was refreshing.  :)
It doesn't look remotely likely to me. Perhaps the newly arrived cylindrical pieces won't go under the launch platform but on top of it?  Perhaps something to do with the deluge system or GSE protection?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StefsEngineering on 05/15/2021 02:08 pm
Sections at the front of the tents.
Pad A.
New crane parts arrived.

That front tire of the trailer doesn't look too healthy..
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/15/2021 02:43 pm
Sections at the front of the tents.
Pad A.
New crane parts arrived.

That front tire of the trailer doesn't look too healthy..
It's a new feature. It allows air to circulate to avoid overheating.  :o   Can I interest you in a bridge?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nicom26 on 05/15/2021 02:50 pm
The upper cone on top of this dome looks like it has a flat-ish top. The vertical pipe behind it makes me thing it's an upper methane dome as opposed to the bottom dome + thrust puck. Could this be a payload adapter for Starship (or at least a test article)?

Edit: Apparently it's from the nosecone structural test article, but it still could be a mock-up or test article adapter

Image credit: Bocachicagal
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/15/2021 02:54 pm
The upper cone on top of this dome looks like it has a flat-ish top. The vertical pipe behind it makes me thing it's an upper methane dome as opposed to the bottom dome + thrust puck. Could this be a payload adapter for Starship (or at least a test article)?

Image credit: Bocachicagal

Are we even sure this is for Starship and not GSE?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/15/2021 02:59 pm
The upper cone on top of this dome looks like it has a flat-ish top. The vertical pipe behind it makes me thing it's an upper methane dome as opposed to the bottom dome + thrust puck. Could this be a payload adapter for Starship (or at least a test article)?

Image credit: Bocachicagal

Are we even sure this is for Starship and not GSE?
It's the inside of the "maxQ" test nosecone that was in the structural test stand until recently.  So no, not GSE.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/15/2021 03:02 pm
The upper cone on top of this dome looks like it has a flat-ish top. The vertical pipe behind it makes me thing it's an upper methane dome as opposed to the bottom dome + thrust puck. Could this be a payload adapter for Starship (or at least a test article)?

Image credit: Bocachicagal

Are we even sure this is for Starship and not GSE?
It's the inside of the "maxQ" test nosecone that was in the structural test stand until recently.  So no, not GSE.

Ah, I didn't realize it was part of the tortured nose.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/15/2021 03:06 pm
As best as I can tell, those areas would be between the fins on the leeward side during re-entry.
Exactly where the clamshell door would be.  The problem with destructive tests is we don't know if they pushed it beyond their design constraints, but if they decide they need more strength in that area, we may see a smaller door for the first cargo missions.
Smaller door or maybe different doors. Or different smaller doors?


Move the hinge on your drawing (nice, btw) towards the bow to shorten the door by 30%. Put the payload on a light weight track and as it moves forward cam the nose end up and out. It would look like a gun in a casement.  Spin and release.


Alternatively, two shorter doors like the Shuttle doors and the same deployment technique.


Mass of reinforcement vs mass of track, cam and actuator. I got no idea where it goes.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/15/2021 03:08 pm
SpaceX Boca Chica Launch Site! daily 3D UPDATE!
https://youtu.be/VkA7Rja2sAU
The variable gap between fins is a head scratcher, I didn't notice or was aware of it before

We don't have a good enough view of the launch table to figure it out either, right?

The background music was refreshing.  :)
It doesn't look remotely likely to me. Perhaps the newly arrived cylindrical pieces won't go under the launch platform but on top of it?  Perhaps something to do with the deluge system or GSE protection?

Replied over in the launch site thread: https://forum.nasaspaceflight.com/index.php?topic=49086.msg2238337#msg2238337
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alphacentauri on 05/15/2021 03:46 pm
https://twitter.com/bocachicagal/status/1393588366856364033

Quote
With the B being brought out of the truck I think it’s safe to say it’s STARBASE. 🤩
@NASASpaceflight
Or maybe they're getting a Starbucks! ⭐☕🚀
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 05/15/2021 05:27 pm
The upper cone on top of this dome looks like it has a flat-ish top. The vertical pipe behind it makes me thing it's an upper methane dome as opposed to the bottom dome + thrust puck. Could this be a payload adapter for Starship (or at least a test article)?

Edit: Apparently it's from the nosecone structural test article, but it still could be a mock-up or test article adapter

Image credit: Bocachicagal

As they appear to be removing the axial loading hydraulic ram from the top of it I’d suspect it’s a bespoke adapter for this test.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/15/2021 07:46 pm
I would not worry much about the test nosecone crunpling. SpaceX is known to test destructibvely their test prototypes. The nosecone not breaking, but only crumpling, is instead a good sign IMO.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: nameUnavailabl on 05/15/2021 07:59 pm
SN17 is gone?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/15/2021 08:08 pm
SN17 is gone?
We don't have sure news, but it is likely.

Marcus House, in his today video suggest that they could skip also sn16, to avoi to much  stops to the construction of the orbital launch site.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/15/2021 09:06 pm
SN17 is gone?
We don't have sure news, but it is likely.

Marcus House, in his today video suggest that they could skip also sn16, to avoi to much  stops to the construction of the orbital launch site.

But I want flights!!!!  They can't fly and build at the same time??  What a second rate company...

/s
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 05/15/2021 09:34 pm
As best as I can tell, those areas would be between the fins on the leeward side during re-entry.
Exactly where the clamshell door would be.  The problem with destructive tests is we don't know if they pushed it beyond their design constraints, but if they decide they need more strength in that area, we may see a smaller door for the first cargo missions.
Move the hinge on your drawing (nice, btw) towards the bow to shorten the door by 30%. Put the payload on a light weight track and as it moves forward cam the nose end up and out. It would look like a gun in a casement.  Spin and release.
Not my drawing.  It's from SpaceX's Starship Users Guide.  My concern was with a potential weakness near the front which might not be easily fixable with reinforcement.  I was thinking a shorter door (or two side doors instead of one opening from the bottom) but just as far back.   As you say, they can still get a cargo advantage by rotating the adapter and launching multiple stacks, just maybe not as large as anticipated at first.  They have already planned for a rotating adapter as the Users Guide says.

One advantage of Starlink stacks is they can probably make them fit the size of the door, not the other way around.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Vikranth on 05/16/2021 05:12 am
SN17 is gone?
We don't have sure news, but it is likely.

Marcus House, in his today video suggest that they could skip also sn16, to avoi to much  stops to the construction of the orbital launch site.

But I want flights!!!!  They can't fly and build at the same time??  What a second rate company...

/s

Well , repeated tests and launches from the Launch Site slows the Construction Work down there. If SpaceX believes that it has acheived all the objectives with a potential SN15 Reflight , it will not want to fly SN16 and slow the progress at the Launch Site for the Orbital Test in Summer. But yes , if SN15 has a leak or is incapable doing a reflight , they "may" move SN16 to pad for a flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/16/2021 07:41 am
Are some parts of the starship picture on the label darker to mean that the part is thst or is the heat shield? Because the part is sn20 mid lox, but on the label both the mid lox and the skirt are darker.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/16/2021 07:47 am
Are some parts of the starship picture on the label darker to mean that the part is thst or is the heat shield? Because the part is sn20 mid lox, but on the label both the mid lox and the skirt are darker.
It's very likely a part of the barrel with stringers. SN20 will surely have full heatshield cause it's going orbital
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/16/2021 07:50 am
Are some parts of the starship picture on the label darker to mean that the part is thst or is the heat shield? Because the part is sn20 mid lox, but on the label both the mid lox and the skirt are darker.
It's very likely a part of the barrel with stringers. SN20 will surely have full heatshield cause it's going orbital

Thanks!

In fact a non full heat shield would seemed strange.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Low87 on 05/16/2021 08:46 am
There is also a possibility that they launch SN20 together with a booster before they practice landing again with SN15/16.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/16/2021 09:30 am
There is also a possibility that they launch SN20 together with a booster before they practice landing again with SN15/16.

Nothing would block them doing this, but since the currentorbital test is NET July, and a starsjip preparetion for orbital test flight takes about a month I don't see reason to do that.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 05/16/2021 09:43 am
There is also a possibility that they launch SN20 together with a booster before they practice landing again with SN15/16.

Nothing would block them doing this, but since the currentorbital test is NET July, and a starsjip preparetion for orbital test flight takes about a month I don't see reason to do that.
Any tests between now and the orbital test would delay orbital because of the launch stand construction being suspended around the preparation for SN15/16 and potential risk of RUD forcing a tidy up of the site. Or damage.

I guess ticking off a full orbital launch would then really test Starship capability and the current block design SN20 has. As soon as SN20 launches, there’s no reason to go back to  SN15/16 as they’ll want to move forward aggressively to get it ready for commercial ops.

Landing SS is a cherry on the top that they’ll need to refine over next 2-3 years ready for Lunar SS and beyond. We’ve seen that now quite comprehensively; they have the data and a test article they’ve probably been assessing on the state of all the parts. Considering what’s going on RE: Lunar HLS contract demonstrations from the other bidders; why not ignore it and not let it impact the company’s wider objectives?


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 05/16/2021 12:27 pm
There is also a possibility that they launch SN20 together with a booster before they practice landing again with SN15/16.

Nothing would block them doing this, but since the currentorbital test is NET July, and a starsjip preparetion for orbital test flight takes about a month I don't see reason to do that.
Any tests between now and the orbital test would delay orbital because of the launch stand construction being suspended around the preparation for SN15/16 and potential risk of RUD forcing a tidy up of the site. Or damage.
...
Possibly, but the bottle neck may well be the FAA authorising the full stack launch. So they might have plenty of time. SpaceX might or might not have a better handle on the approximate FAA timing. We will probably get an indirect confirmation of this if SN15 flies again.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: tunster on 05/16/2021 12:58 pm
There is also a possibility that they launch SN20 together with a booster before they practice landing again with SN15/16.

Nothing would block them doing this, but since the currentorbital test is NET July, and a starsjip preparetion for orbital test flight takes about a month I don't see reason to do that.
Any tests between now and the orbital test would delay orbital because of the launch stand construction being suspended around the preparation for SN15/16 and potential risk of RUD forcing a tidy up of the site. Or damage.
...
Possibly, but the bottle neck may well be the FAA authorising the full stack launch. So they might have plenty of time. SpaceX might or might not have a better handle on the approximate FAA timing. We will probably get an indirect confirmation of this if SN15 flies again.
That’s true. There was clearance for SN15-17 to go (assuming SpaceX kept to the same tech specs with only very minor changes). I think the scope here was to get this batch to land within 3 attempts. They clearly did that on first go!

So who knows. The announcement from SpaceX on the orbital will be huge (and unlike the SN flight tests on the day - assuming we didn’t have the indies out at Boca filming history ).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jak Kennedy on 05/16/2021 01:16 pm
Perhaps SpaceX could fly SN15 with more fuel and higher thrust with a landing in the Gulf. Perhaps even after an orbital launch to apply any lessons learned.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/16/2021 01:27 pm


https://twitter.com/bocachicagal/status/1393743783242706944

Quote
Welcome to STARBASE!
@NASASpaceflight

https://twitter.com/bocachicagal/status/1393758375637405696

Quote
The moment the STARBASE sign was lit up for the first time. Another special moment with special people.
@NASASpaceflight

My wife looks at it and sighs.  "The road to Mars is paved with bad kerning, I guess"

Yes, she's a perfectionist...

Me, I just love how it came on one letter at a time..  How delightfully retro!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/16/2021 01:28 pm
That’s hilarious! 😂
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/16/2021 02:38 pm
Perhaps SpaceX could fly SN15 with more fuel and higher thrust with a landing in the Gulf. Perhaps even after an orbital launch to apply any lessons learned.

What would they gain landing sn15  agter its second flight in the Gulf?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 05/16/2021 03:50 pm
I'm hoping for a higher hop, faster speeds.... But with the MaxQ stand I doubt it, probably just another 10km hop identical flight to compare data between the two, and prove reuse.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RoadWithoutEnd on 05/16/2021 04:14 pm
My wife looks at it and sighs.  "The road to Mars is paved with bad kerning, I guess"

Yes, she's a perfectionist...

Me, I just love how it came on one letter at a time..  How delightfully retro!

I love the font, whatever it is.  Like some ghostly 3D manifestation of typewriter characters.  Like if the LAX sign had been done right.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/16/2021 04:55 pm
As best as I can tell, those areas would be between the fins on the leeward side during re-entry.
Exactly where the clamshell door would be.  The problem with destructive tests is we don't know if they pushed it beyond their design constraints, but if they decide they need more strength in that area, we may see a smaller door for the first cargo missions.
Move the hinge on your drawing (nice, btw) towards the bow to shorten the door by 30%. Put the payload on a light weight track and as it moves forward cam the nose end up and out. It would look like a gun in a casement.  Spin and release.
Not my drawing.  It's from SpaceX's Starship Users Guide.  My concern was with a potential weakness near the front which might not be easily fixable with reinforcement.  I was thinking a shorter door (or two side doors instead of one opening from the bottom) but just as far back.   As you say, they can still get a cargo advantage by rotating the adapter and launching multiple stacks, just maybe not as large as anticipated at first.  They have already planned for a rotating adapter as the Users Guide says.

One advantage of Starlink stacks is they can probably make them fit the size of the door, not the other way around.
In the interest of full disclosure, by spin, I meant spin the ship so the sats fling out. So the users guide says a rotating dispenser. A revolver, not a pepper pot.


Edit to add: I can't envision any type of hatch without stiffening reinforcement on the door and the jam. It could be the thinnest of stainless formed into a slightly bulged frame. I've got an image in my head but I'm not sure where the image comes from. Probably aircraft.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Keldor on 05/16/2021 05:00 pm


https://twitter.com/bocachicagal/status/1393743783242706944

Quote
Welcome to STARBASE!
@NASASpaceflight

https://twitter.com/bocachicagal/status/1393758375637405696

Quote
The moment the STARBASE sign was lit up for the first time. Another special moment with special people.
@NASASpaceflight

My wife looks at it and sighs.  "The road to Mars is paved with bad kerning, I guess"

Yes, she's a perfectionist...

Me, I just love how it came on one letter at a time..  How delightfully retro!

Actually, I think the kerning is correct.  It's just distortion from the wide angle lens that makes the inner letters look closer together than the outer ones.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/16/2021 05:01 pm


https://twitter.com/bocachicagal/status/1393743783242706944

Quote
Welcome to STARBASE!
@NASASpaceflight

https://twitter.com/bocachicagal/status/1393758375637405696

Quote
The moment the STARBASE sign was lit up for the first time. Another special moment with special people.
@NASASpaceflight

My wife looks at it and sighs.  "The road to Mars is paved with bad kerning, I guess"

Yes, she's a perfectionist...

Me, I just love how it came on one letter at a time..  How delightfully retro!

Actually, I think the kerning is correct.  It's just distortion from the very wide angle lens that makes the inner letters look closer together than the outer ones.
That may be true!

Much relief.

Still when I'm there next I'll try to take a long distance shot.  With lens info, it may even be possible to un-distort this one
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/16/2021 05:10 pm
Are some parts of the starship picture on the label darker to mean that the part is thst or is the heat shield? Because the part is sn20 mid lox, but on the label both the mid lox and the skirt are darker.
It's very likely a part of the barrel with stringers. SN20 will surely have full heatshield cause it's going orbital

Thanks!

In fact a non full heat shield would seemed strange.
We've seen nothing but cylinder tiles. The chases, hinges, fins and ogive are the hard part. SX might throw something on just to see how it works but not with any great confidence that it'll work. If my logic holds, 20 is a throwaway.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: electricdawn on 05/16/2021 05:21 pm
Quote
If my logic holds, 20 is a throwaway.

It most likely is. I don't think even Elon believes that it will make it back safe and sound.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RotoSequence on 05/16/2021 05:53 pm
My wife looks at it and sighs.  "The road to Mars is paved with bad kerning, I guess"

Yes, she's a perfectionist...

Me, I just love how it came on one letter at a time..  How delightfully retro!

I love the font, whatever it is.  Like some ghostly 3D manifestation of typewriter characters.  Like if the LAX sign had been done right.

Roboto Bold is probably the best candidate. It almost looks like OCR-B, but the B itself doesn't look quite right.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/16/2021 06:08 pm
My wife looks at it and sighs.  "The road to Mars is paved with bad kerning, I guess"

Yes, she's a perfectionist...

Me, I just love how it came on one letter at a time..  How delightfully retro!

I love the font, whatever it is.  Like some ghostly 3D manifestation of typewriter characters.  Like if the LAX sign had been done right.
Agreed :) it's so future retro.

And this is a sign of utmost import, I'm so happy it came out the way it did.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slarty1080 on 05/16/2021 09:24 pm
Are some parts of the starship picture on the label darker to mean that the part is thst or is the heat shield? Because the part is sn20 mid lox, but on the label both the mid lox and the skirt are darker.
It's very likely a part of the barrel with stringers. SN20 will surely have full heatshield cause it's going orbital

Thanks!

In fact a non full heat shield would seemed strange.
We've seen nothing but cylinder tiles. The chases, hinges, fins and ogive are the hard part. SX might throw something on just to see how it works but not with any great confidence that it'll work. If my logic holds, 20 is a throwaway.
Presumably if they still haven't sorted out all of these specialist tiles they could still fly with some ablative coating temporary measure in some places?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/16/2021 10:03 pm
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/16/2021 10:46 pm
That’s hilarious! 😂
She's so delighted that people are talking fonts. I've been yammering on and on about Starships and SN this and SN that (I'm sure you know what I mean), took a couple of trips to check out the digs, and suddenly - we have a connection!  Whatever it takes...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/16/2021 11:56 pm
Quote
If my logic holds, 20 is a throwaway.

It most likely is. I don't think even Elon believes that it will make it back safe and sound.
Scott Manley has a video today on what is disclosed by SpaceX in their FCC filing for the SN 20 launch.  They’re expecting to launch, stage Separate, have the booster do a boost back burn and attempt a “landing” about 20 miles off the coast from Boca Chica.  The Starship will then continue not quite to orbit.  It will reenter above the Pacific, and is expected to make it back down to the ground.

I say expected, in that that’s what their document says they’re planning, but maybe that’s a hope more than an expectation.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: philw1776 on 05/17/2021 12:07 am
Quote
If my logic holds, 20 is a throwaway.

It most likely is. I don't think even Elon believes that it will make it back safe and sound.
Scott Manley has a video today on what is disclosed by SpaceX in their FCC filing for the SN 20 launch.  They’re expecting to launch, stage Separate, have the booster do a boost back burn and attempt a “landing” about 20 miles off the coast from Boca Chica.  The Starship will then continue not quite to orbit.  It will reenter above the Pacific, and is expected to make it back down to the ground.

I say expected, in that that’s what their document says they’re planning, but maybe that’s a hope more than an expectation.

That mission scenario covered in detail in this thread

https://forum.nasaspaceflight.com/index.php?topic=53846.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Cheapchips on 05/17/2021 08:36 am

Should we take yesterday's LOX delivery as an encouraging sign that they're going to fly either SN15 or SN16 within some soonish timeframe?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Hamish.Student on 05/17/2021 09:55 am

Should we take yesterday's LOX delivery as an encouraging sign that they're going to fly either SN15 or SN16 within some soonish timeframe?
 
 
On this note, what is the SOP for long term tankage? Do they vent them and keep them empty until needed, or do they store some nominal amount of the gas/liquid inside for the weeks/months between tests?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: erv on 05/17/2021 12:02 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Johnnyhinbos on 05/17/2021 12:33 pm
Do they remove or just lock again the Flight Termination System after each flight?

They remove it - as can been seen in the photo prior to your post in the UPDATES thread.

As an aside, questions shouldn't be posted in UPDATES threads, hence my quoting and replying to your questions on the Discussion thread...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/17/2021 01:17 pm

Should we take yesterday's LOX delivery as an encouraging sign that they're going to fly either SN15 or SN16 within some soonish timeframe?
 
 
On this note, what is the SOP for long term tankage? Do they vent them and keep them empty until needed, or do they store some nominal amount of the gas/liquid inside for the weeks/months between tests?

No, I don’t think it’s a sign of anything except periodic replenishment. If you read Eric Berger’s recent book, Elon threatened to fire the launch team for the first Falcon 1 static fire campaign because they ran out of LOX.

From an engineering perspective, it’s generally easier to keep the average bulk temperature of a commodity stable if the tanks are full or very close, so there’s minimal free surface area to lose or gain heat by convection with the gas above the liquid surface. I have no idea of the average boil-off rate but there are pretty regular cryo deliveries at the site all the time. I’m sure that’s the incentive to build their own cryo plant on site.

But that said, I think there’s a lot of discussion about all this in the Texas Launch Site thread.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/17/2021 06:46 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

We'll see.

I agree that with the big cranes around we won't see lots of testing. I expect them to take off the raptors, but I have nothing to prove that, but it makes sense to me. But they could also re-launch sn15 without raptor swaps or cheks. I will be riskier, but SpaceX showed to sometimes take big risks.

Have sn5 or sn6 been  lifted onto the pad  after their flight this summer? If not sn15 being on the pad could be a good sign to a reflight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: RocketLover0119 on 05/17/2021 07:12 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

Very likely 16 doesn’t fly. If 15 flies, that will be it prior to Orbital IMO.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/17/2021 07:53 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

Very likely 16 doesn’t fly. If 15 flies, that will be it prior to Orbital IMO.

I agree with a potential sn15 reflight before the orbital flight. If the orbital flight proves another time the landing sequence (assuming sn20 survives the reentry) I see no reason to keep testing suborbital.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: r8ix on 05/18/2021 12:20 am
Booster dome.
Delivery.

I don't think that's a booster dome, looks like a SS thrust dome...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/18/2021 12:22 am
Booster dome.
Delivery.

I don't think that's a booster dome, looks like a SS thrust dome...

It's actually a practice dome, they've got all sorts of trial ports for different engine mounts.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jose m on 05/18/2021 01:57 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/18/2021 02:26 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.
That's possible, but the "unzipping" effect didn't happen on SN15 when it lost a tile.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StarshipTrooper on 05/18/2021 02:46 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.
That's possible, but the "unzipping" effect didn't happen on SN15 when it lost a tile.

That tile came loose at about 300 mph. The starship will reenter at 17,000 mph!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/18/2021 02:50 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.
That's possible, but the "unzipping" effect didn't happen on SN15 when it lost a tile.

That tile came loose at about 300 mph. The starship will reenter at 17,000 mph!
Dynamic pressure would be similar at 17000mph at high altitude and 300mph at low altitude. So forces would be roughly the same. Although material strength may be lower because of the higher heat.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CruddyCuber on 05/18/2021 03:04 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.
That's possible, but the "unzipping" effect didn't happen on SN15 when it lost a tile.

That tile came loose at about 300 mph. The starship will reenter at 17,000 mph!

That particular tile appears to have been lost on touchdown:

Just a small and quick observation

Per the latest SN15 video by SpaceX, the missing heat shield tile on the big patch around the methane tank only came off on touchdown! Unclear about the other broken tiles down near the skirt however...

Also, the best place for further Starship heat shield discussion is the Starship heat shield thread.
https://forum.nasaspaceflight.com/index.php?topic=50748.0 (https://forum.nasaspaceflight.com/index.php?topic=50748.0)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: PreferToLurk on 05/18/2021 03:12 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.

First off, welcome to the forum.  But secondly, kindly locate the caps lock button and make sure it is not engaged.

Most of the temperature is NOT generated by friction, but rather by the air in front being pressurized.  Shuttle came home with missing tiles quite frequently, and I do not believe any unzipping of tiles was ever witnessed on the shuttle.  Further, this is exactly the kind of potential problem that will be studied extensively by SpaceX's CFD modeling teams.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: GHogan on 05/18/2021 03:42 am
As far as I know, the vacuum Raptors have not been static fired in a full up Starship setting. So will there be a 6 engine static fire on a Starship launch pad before SN20 is stacked on BN3? And will this first test be done with a different SNx before risking SN20?

Reason for a test: Because 6 engines have have not be tried before.
Reason against: Most likely failure means an engine has to be turned off early. SN20 can reach orbit with one missing engine, so just go for it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 05/18/2021 04:16 am
RGV's latest tweet shows they are pouring fresh concrete at the base of Pad B so I wouldn't expect a static fire or rehop anytime soon.  Pad B could just be a convenient spot to stash SN15 while they do post-flight inspections. Of course, Elon has said he wanted to do rapid reflights, but that was before all the construction really took off.

SN16 is a question mark.  Do they move it to Pad A to make room in the mid-bay for SN20, or do they scrap it so SN20 can go to Pad A for preorbital static fires.  Maybe SN15 goes to a display stand to make room.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: eeergo on 05/18/2021 08:03 am
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.

First off, welcome to the forum.  But secondly, kindly locate the caps lock button and make sure it is not engaged.

Most of the temperature is NOT generated by friction, but rather by the air in front being pressurized.  Shuttle came home with missing tiles quite frequently, and I do not believe any unzipping of tiles was ever witnessed on the shuttle.  Further, this is exactly the kind of potential problem that will be studied extensively by SpaceX's CFD modeling teams.

Missing full tiles were very seldom seen during Shuttle (as opposed to chipped or cosmetically scratched, which were more frequent yet excruciatingly analyzed the hell out of during OBSS ops upon orbital insertion), at least post-Columbia.

The few times entire tiles did come off (most infamously STS-27, even if that instance had the huge luck of having an enormous hefty heat sink lying just underneath the missing tile, otherwise it would probably have been catastrophic), "unzipping" of downstream tiles didn't happen as such, although attachments were very different to what's being used in the Starship prototypes (individually glued vs mechanically attached), so that experience may well not apply any longer, especially concerning potential voids under/around the tiles catalyzing the effect.

However, the downstream tiles did get heavily damaged even with only relatively shallow gouges, having their leading edges melted away. For this effect in a well-analyzed, extensively documented recent mission, see STS-118 (this very site has a trove of information and open-access IFA presentations in L2 and elsewhere, including a dedicated thread for the damage and repair options being weighed at the time: https://forum.nasaspaceflight.com/index.php?topic=9388.0), which also featured legacy analysis of in-family effects from STS-103: http://www.collectspace.com//ubb/Forum30/HTML/000588.html

There were even experiments on real, live STS heatshields with "bumps" built into the tiles to study downstream heating and damage effects: BLT. https://core.ac.uk/download/pdf/10551931.pdf (in STS-119, -128, -131, -134 and -135). Of course, in-orbit servicing of the heatshield was available through putty, plug and other types of repairs, including the actually-performed neat-up/stapling of AFRSI blankets.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: raivo45 on 05/18/2021 10:02 am
RGV's latest tweet shows they are pouring fresh concrete at the base of Pad B so I wouldn't expect a static fire or rehop anytime soon.  Pad B could just be a convenient spot to stash SN15 while they do post-flight inspections. Of course, Elon has said he wanted to do rapid reflights, but that was before all the construction really took off.

SN16 is a question mark.  Do they move it to Pad A to make room in the mid-bay for SN20, or do they scrap it so SN20 can go to Pad A for preorbital static fires.  Maybe SN15 goes to a display stand to make room.

So far they've been flying from Pad A, then B, A, B...(fly from one pad, repair the other). I wouldn't be suprised if pad A also needs some refurbishment so there might not be another test flight for a while.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/18/2021 10:55 am
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

Very likely 16 doesn’t fly. If 15 flies, that will be it prior to Orbital IMO.

I agree with a potential sn15 reflight before the orbital flight. If the orbital flight proves another time the landing sequence (assuming sn20 survives the reentry) I see no reason to keep testing suborbital.

If they continue to test orbital, where will Starship land?

It's possible the FAA hasn't allowed orbital Starship flights to land at Boca Chica due to sonic boom noise. Over 1 million people live and work within yellow line on the map below (details here (https://forum.nasaspaceflight.com/index.php?topic=53471.msg2234826#msg2234826)). This includes Matamoros, Mexico, with a population of 520,367. So in addition to FAA approval, SpaceX may also need approval from Mexico in order to land SS at BC.

It's not clear if ASDS barges can support Starship landings. It's also not clear when Phobos will be ready for SS landings.

So it's possible that SpaceX will continue SS suborbital test flights until their offshore platform is ready.
Note that this document (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf) from the FAA seems to imply that suborbital SS flights up to 30 kilometers can land at BC.
Perhaps this higher altitude will allow SpaceX to gather additional test data from suborbital flights.

Or not. It's also possible the FAA and Mexico will allow occasional SS orbital test flights to land at BC.
I'm just pointing out potential issues SpaceX may face. It will be interesting to see how this all works out.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jbrian31 on 05/18/2021 12:38 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

Very likely 16 doesn’t fly. If 15 flies, that will be it prior to Orbital IMO.

So in addition to FAA approval, SpaceX may also need approval from Mexico in order to land SS at BC.



I highly doubt Space X needs approval from Mexico to land or launch anything from Boca Chica.  They would not have built up this entire launch complex there to only be denied operations at the whim of Mexico.  Sure there will be cooporation to notify Mexico of operations and address any concerns that Mexico might have, but no, there is not likely any approval needed from Mexico.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sferrin on 05/18/2021 01:05 pm
RGV's latest tweet shows they are pouring fresh concrete at the base of Pad B so I wouldn't expect a static fire or rehop anytime soon.  Pad B could just be a convenient spot to stash SN15 while they do post-flight inspections. Of course, Elon has said he wanted to do rapid reflights, but that was before all the construction really took off.

SN16 is a question mark.  Do they move it to Pad A to make room in the mid-bay for SN20, or do they scrap it so SN20 can go to Pad A for preorbital static fires.  Maybe SN15 goes to a display stand to make room.


Not to mention the 11000 crane going up nearby.  Weeks at best before a second flight, if there is one, would be my guess.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/18/2021 01:06 pm
Agree. No point in building the launch tower if they weren't planning on return to launch site. If the site was just used to launch only, than a crane could be used to stack Starship on SH.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Kazioo on 05/18/2021 01:20 pm
If the site was just used to launch only, than a crane could be used to stack Starship on SH.

https://twitter.com/elonmusk/status/1372697001633136646
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/18/2021 01:45 pm
If the site was just used to launch only, than a crane could be used to stack Starship on SH.

https://twitter.com/elonmusk/status/1372697001633136646

Thanks for that. I totally forgot about that... was thinking if cranes were big enough to build tower with those massive sections, they'd be big enough to lift Starship.... I suspect the stabilization mentioned above is the difference.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/18/2021 02:01 pm
https://twitter.com/considercosmos/status/1394644964601208835

Quote
The beginning of a new era

#Starship @elonmusk @SpaceX

All this technology sending rockets to space, and they need someone to run to each letter and turn it on.  LMAO!!!  But credit to the runner, though - he hit each letter with some pretty good timing...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: wannamoonbase on 05/18/2021 02:20 pm
If the site was just used to launch only, than a crane could be used to stack Starship on SH.

https://twitter.com/elonmusk/status/1372697001633136646

Thanks for that. I totally forgot about that... was thinking if cranes were big enough to build tower with those massive sections, they'd be big enough to lift Starship.... I suspect the stabilization mentioned above is the difference.

This is a reason why I've never bought into the arm free renders of the Starship stack.  The renders have looked great, but the final real world reality was always going to be less clean.

I still expect SS to get fueled through the Super Heavy interstage. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: alphacentauri on 05/18/2021 02:52 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/18/2021 02:59 pm
If the site was just used to launch only, than a crane could be used to stack Starship on SH.

https://twitter.com/elonmusk/status/1372697001633136646

To be clear, the potential issue of sonic boom noise being over the legal limit up to 30 miles West of the landing site only applies to orbital Starship missions.  According to the sonic boom expert that did the environmental assessment, this area would have sonic booms loud enough to startle people.

But there are no such sonic boom issues for suborbital flights of Starship or Super Heavy. These come in from the opposite direction, over the Gulf, so they're not over populated areas.  Suborbital flights also tend to be slower, so the sonic booms aren't as loud.

So it's possible that Starship could land offshore and then hop back to Boca Chica for the next launch.

Or not.  Again, we're all just making educated guesses based on the information we have at the moment. Things change.

In any case, it will be interesting to see how this issue plays out. 
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/18/2021 03:12 pm
At what altitude should Starship become subsonic while in belly flop free fall?

If terminal velocity is ~200mph at sea level, then air density must be a factor of ~15 times less to break the sound barrier. I calculate that’s at about 60,000ft (~18km). About 90,000ft for Mach 2 (like Concorde).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: dante2308 on 05/18/2021 03:21 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

Very likely 16 doesn’t fly. If 15 flies, that will be it prior to Orbital IMO.

I agree with a potential sn15 reflight before the orbital flight. If the orbital flight proves another time the landing sequence (assuming sn20 survives the reentry) I see no reason to keep testing suborbital.

These orbital test flights are likely to be expensive. I think it might make sense to test major Starship changes or sequences that do not require Super Heavy separately in some cases. I'm surprised they don't plan to test SH separately before orbit, but I imagine they feel like reaching orbit is a valuable test regardless of reentry.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/18/2021 03:22 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?

I was thinking about this as well, and what I think might happen is that SN20 will be mounted on the suborbital launch mount for a cryo test and static fire of the sea level engines. A preburner test might be done on the vacuum engines as well, but I don't expect a static fire from those. After the checks are complete, SN20 would be stacked on BN3.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/18/2021 03:25 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?
I don;t know what other manufacturers do, but to the best of my "knowledge", I believe SpaceX hot-fires all F9 second stages and all new F9 boosters at McGregor during acceptance testing.  Once Starship enters production, I could see something similar happening to, as you say, verify engines and plumbing, etc. are A-OK.

As for pre-launch static fire, again I don't know what anyone else is doing, but SpaceX used to pre-launch static fire the first stage every time, but has been getting away from this as they gain more experience with the booster.  At some point the benefit is presumably offset by the cost of extra engine start cycles.  I believe if a customer really wants a static fire prior to launch, they can request this as an add-on service.

So will they do a pre-launch static fire of Starship right before stacking?  Initially, your guess is as good as mine, but once this whole system gets rolling, almost certainly not as they'd never make their desired launch cadence by doing this.  It will (IMO) end up getting handled just like any other second stage ... hot fired for acceptance testing, or perhaps after major service, but otherwise it's just expected to work.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/18/2021 03:36 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?

I was thinking about this as well, and what I think might happen is that SN20 will be mounted on the suborbital launch mount for a cryo test and static fire of the sea level engines. A preburner test might be done on the vacuum engines as well, but I don't expect a static fire from those. After the checks are complete, SN20 would be stacked on BN3.
If you're going to static fire, you may as well test all the engines.  The bells on the current iteration of VacRaptors are a bit over-expanded for sea-level firing, but there a far cry from an optimized vacuum nozzle, and they seem to be capable of sea-level firing.  They're test firing them at McGregor, so a quick static fire shouldn't be a problem.  SpaceX seems to have traded a few ISP points for an engine that could also fire at sea-level.  I suppose geometric constraints (i.e., bells that would fit in a 9m Starship skirt) could have also been a factor, but now I'm speculating.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/18/2021 03:43 pm
Starship may be relatively resilient to loss of a tile or two as it’s empty (skin can radiate in two directions) and made of stainless (high melting point). If they also have decent strength margin, they can handle a pretty high stainless temperature without getting a hole.

I DOUBT IT, THE FRICTION IS SO HIGH, THAT IT PRODUCES THE HEAT, IF A TILE COMES OFF, FORCES WILL BE GENERATED THAT WILL RELEASE THE TILES AROUND THE HOLE.
The shockwave stands off from the rocket forming a stagnation area along the centerline. There is outward flow in the stagnation area but it is lower velocity than the reentry speed. The standoff is thickest along the centerline and thinnest 90 degrees to either side. It is also relatively insensitive to minor surface irregularities. Loosing a patch of tiles could lead to further loss of tiles. Loosening a single tile, assuming robust attachment, should not start a chain reaction.

The real danger of loosing a single tile is radiative heating from the plasma. Presumably, one of the jobs of the underlayment pad is to mitigate this heating.


Edit: And welcome to the forum. Hint: using all caps is shouting. Save it for when you need it.  ;) [size=78%]  [/size]
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/18/2021 03:43 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?

I was thinking about this as well, and what I think might happen is that SN20 will be mounted on the suborbital launch mount for a cryo test and static fire of the sea level engines. A preburner test might be done on the vacuum engines as well, but I don't expect a static fire from those. After the checks are complete, SN20 would be stacked on BN3.
If you're going to static fire, you may as well test all the engines.  The bells on the current iteration of VacRaptors are a bit underexpanded for sea-level firing, but there a far cry from an optimized vacuum nozzle, and they seem to be capable of sea-level firing.  They're test firing them at McGregor, so a quick static fire shouldn't be a problem.  SpaceX seems to have traded a few ISP points for an engine that could also fire at sea-level.  I suppose geometric constraints (i.e., bells that would fit in a 9m Starship skirt) could have also been a factor, but now I'm speculating.

I doubt they will static fire the vacuum engines. There is flow separation visible on the static fire tests at McGregor, but keep in mind that they have a pretty heavy duty ground side reinforcement on the nozzle so it can be fired at sea level. Once the engines are mounted on the vehicle, they would have to fire the engines without the extra support, AND since the plume is way underexpanded, the plume will impinge more harshly with the ground. Hence my doubts on them attempting a static fire on the vacuum engines. With that said, you never know - they could just go for it too. I doubt it though.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: chopsticks on 05/18/2021 03:48 pm
Also F9 second stage static fires are performed without the vacuum nozzle. This won't be possible with Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/18/2021 03:52 pm
Also F9 second stage static fires are performed without the vacuum nozzle. This won't be possible with Starship.
I leaned something today - thank you!  I know they static fired them, but now that I think about it, of course they couldn't use the vacuum nozzles for the static fire.  Those are way to big for sea level firing.  As to whether or not they will static fire the VacRaptors, you could be right.  I truly know just as much as most of the other residents here, which is to say not very much.  Either way, its fun to watch!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/18/2021 03:58 pm
Maybe a static fire(s) for SN15 (and/or SN16 if it moves to the pad soon)?
With all those monster cranes around, I do not think anything is going to fly in the next week or few. Unless unintentionally.  ;)

Very likely 16 doesn’t fly. If 15 flies, that will be it prior to Orbital IMO.

So in addition to FAA approval, SpaceX may also need approval from Mexico in order to land SS at BC.



I highly doubt Space X needs approval from Mexico to land or launch anything from Boca Chica.  They would not have built up this entire launch complex there to only be denied operations at the whim of Mexico.  Sure there will be cooporation to notify Mexico of operations and address any concerns that Mexico might have, but no, there is not likely any approval needed from Mexico.

You may be correct from a strictly legal point of view (or maybe not), but what would be the impact of a formal Mexican diplomatic complaint of 10,000 broken windows and associated carnage?  It's always good policy to not poop on your neighbor.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/18/2021 04:06 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?

Like others said I expect SpaceX to static fire the starship before the integration. IMO when starship is proven and reliable, after years, they will be able to stop doing many static fires, because they accelerate the degradation of the engines (that depends more on the  number of cycles of chilling and warming than on the number of total seconds fired, like airplains ). IIRC they are currently reducing the number of Static fires done with f9, but they still do at least one befor the flight, on the pad.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/18/2021 04:07 pm
One thing puzzling me lately is the static fire testing prior to launch. The Starship prototypes have all performed static fires before launch to prove the engines and plumbing are working properly. Falcons, Space Shuttles and other liquid fueled rockets also have static fire tests on the launch pad before production launches, although I've never paid close enough to note whether it's done before *every* production launch with every rocket (is it?).

So, when SpaceX is ready for the first orbital launch of the prototype SS/SH stack, I expect there will be a static fire test on the launch pad to test the SH and its 20+ Raptors, but what about SS and its 6 Raptors? Will SS be static fired on a test stand prior to stacking, or will only SH be static fired and fingers crossed at stage separation that the SS Raptors ignite? Assuming SH and SS will have separate static fire tests, is this level of testing only for the prototype phase, or will it carry through to production launches for moon and Mars missions?

Like others said I expect SpaceX to static fire the starship before the integration. IMO when starship is proven and reliable, after years, they will be able to stop doing many static fires, because they accelerate the degradation of the engines (that depends more on the  number of cycles of chilling and warming than on the number of total seconds fired, like airplains ). IIRC they are currently reducing the number of Static fires done with f9, but they still do at least one befor the flight, on the pad.
More specifically, static fire isn't needed for flight-proven stages (unless they're changing something major/needed something)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Doom2pro on 05/18/2021 05:25 pm
No launch until very least Pad B concrete cures...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/18/2021 05:29 pm
No launch until very least Pad B concrete cures...

Anyway they will need to perform testing such as pressure testing and static fire(s).

Are these blocked by the concrete curing?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cscott on 05/18/2021 05:35 pm
IIRC they are currently reducing the number of Static fires done with f9, but they still do at least one befor the flight, on the pad.

Only before the first flight of a new booster.  Not necessarily on reflight.  And f9 2nd stage is never static fired on the pad, obviously.

See https://forum.nasaspaceflight.com/index.php?topic=51340.0
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/18/2021 05:49 pm
No launch until very least Pad B concrete cures...

Anyway they will need to perform testing such as pressure testing and static fire(s).

Are these blocked by the concrete curing?

Probably not an issue for pressure testing. We have also seen them fire on new concrete that wasn't very old, but not sure of exact time. Was a lot quicker than some anticipated.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/18/2021 06:09 pm
is also relatively insensitive to minor surface irregularities. Loosing a patch of tiles could lead to further loss of tiles. Loosening a single tile, assuming robust attachment, should not start a chain reaction.

The real danger of loosing a single tile is radiative heating from the plasma. Presumably, one of the jobs of the underlayment pad is to mitigate this heating.


A smooth vehicle surface allows for a laminar flow of air around the vehicle. If the bumps on the surface are too large, you can trip the boundary layer from laminar to turbulent downstream from that location. This turbulent airflow creates a smaller separation between the vehicle and the hot plasma layer, meaning more heat transfer. So downstream from an irregularity, you can get significantly more heating. Sometimes, enough heating to burn through that next tile and continue the process until you have a bigger problem.

There were some shuttle DTO that looked at this by intentionally introducing irregularities along the surface of the orbiter underside. The data collected was then compared to computational models to help make these models of boundary layer conditions in hypersonic airflow more accurate. https://www.nasaspaceflight.com/2010/06/blt-height-increase-addition-to-sts-134-cleared/ (https://www.nasaspaceflight.com/2010/06/blt-height-increase-addition-to-sts-134-cleared/)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/18/2021 06:56 pm
is also relatively insensitive to minor surface irregularities. Loosing a patch of tiles could lead to further loss of tiles. Loosening a single tile, assuming robust attachment, should not start a chain reaction.

The real danger of loosing a single tile is radiative heating from the plasma. Presumably, one of the jobs of the underlayment pad is to mitigate this heating.


A smooth vehicle surface allows for a laminar flow of air around the vehicle. If the bumps on the surface are too large, you can trip the boundary layer from laminar to turbulent downstream from that location. This turbulent airflow creates a smaller separation between the vehicle and the hot plasma layer, meaning more heat transfer. So downstream from an irregularity, you can get significantly more heating. Sometimes, enough heating to burn through that next tile and continue the process until you have a bigger problem.

There were some shuttle DTO that looked at this by intentionally introducing irregularities along the surface of the orbiter underside. The data collected was then compared to computational models to help make these models of boundary layer conditions in hypersonic airflow more accurate. https://www.nasaspaceflight.com/2010/06/blt-height-increase-addition-to-sts-134-cleared/ (https://www.nasaspaceflight.com/2010/06/blt-height-increase-addition-to-sts-134-cleared/)
You have to be *very* careful about statements like this.  You can also cause more laminar flow to occur by disturbing the boundary layer.  That's what golf balls are doing with the dimples.  Aerodynamics isn't as simple as "rough surface bad".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/18/2021 07:02 pm
https://twitter.com/considercosmos/status/1394644964601208835

Quote
The beginning of a new era

#Starship @elonmusk @SpaceX

All this technology sending rockets to space, and they need someone to run to each letter and turn it on.  LMAO!!!  But credit to the runner, though - he hit each letter with some pretty good timing...

A LampLighter!    An ode to Antoine de Saint-Exupéry and to John Le Carré  :)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 05/18/2021 07:02 pm
You have to be *very* careful about statements like this.  You can also cause more laminar flow to occur by disturbing the boundary layer.  That's what golf balls are doing with the dimples.  Aerodynamics isn't as simple as "rough surface bad".

No.

Dimples on golf balls trip the boundary layer from laminar to turbulent.  This allows the flow to "stick" to the ball longer (it moves the separation point aft), thus reducing drag by delaying separation, not by causing more laminar flow.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/18/2021 07:08 pm
You can actually suck down the boundary layer artificially with actual suction through holes,  increasing laminar flow. But that’s obviously not happening here.

Whether tripping from laminar to turbulent flow increases or reduces drag depends on the details.

For a Reynolds number of 10^5, rough spheres have lower drag than smooth ones. At Re = 10^6, the opposite is true.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Mike_1179 on 05/18/2021 07:26 pm
Can I just say I’m so excited to see a discussion of fluid dynamics.

Some of the things that occur in exotic regimes like reentry vehicles don’t make intuitive sense compared to our every day intuitions.

I guess I’m trying to say our ideas as to what might or might not happen on the heat shield are mainly arm waving absent clear information
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 05/18/2021 07:50 pm
You can actually suck down the boundary layer artificially with actual suction through holes,  increasing laminar flow. But that’s obviously not happening here.

Whether tripping from laminar to turbulent flow increases or reduces drag depends on the details.

For a Reynolds number of 10^5, rough spheres have lower drag than smooth ones. At Re = 10^6, the opposite is true.

That's true, but 10^6 for a golf ball is about Mach 1, which is a bit beyond the capabilities of your average weekend duffer.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zodiacchris on 05/18/2021 08:30 pm
Guys, as exited as I am to see a discussion of fluid dynamics and the impact on heat shields in Texas Prototypes, this is the wrong thread! Kindly take it to the Starship Heat Shield thread next door...

Thank you!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: InterestedEngineer on 05/18/2021 08:45 pm
No launch until very least Pad B concrete cures...

I think I've counted at least 10 posts in the last 6 months of something to the effect of "curing time is a function of how much you pay for it".

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Slothman on 05/18/2021 08:49 pm
No launch until very least Pad B concrete cures...

I think I've counted at least 10 posts in the last 6 months of something to the effect of "curing time is a function of how much you pay for it".
Abd how long you need it to stay intact before redoing it
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: JCopernicus on 05/18/2021 09:06 pm
Why isn't the landing pad made of steel?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/18/2021 09:57 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x style pathfinder test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship dome as it is 3 RSL and 3 RVac mounts shown. The orbital iteration still needs to be proof and structural tested.

EDIT: added clarification to my post.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Nevyn72 on 05/18/2021 10:37 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship "orbital" version dome as it is 3 RSL and 3 RVac mounts shown. This iteration still needs to be proof and structural tested.

It's scrap, the thrust puck is the previous generation, the RVac mounts are all different, there's a large plasma cutout on the sleeve wall.... There's even a sticker that says scrap!

I think this is just sleeving practice for a newbie.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aip on 05/18/2021 11:57 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship "orbital" version dome as it is 3 RSL and 3 RVac mounts shown. This iteration still needs to be proof and structural tested.
My thoughts too, assuming you meant SN17.x not SN7.x. With at least two months until the orbital attempt, it seems prudent to retire some risk due to the increase from 3 engines to 6.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/19/2021 01:17 am
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship "orbital" version dome as it is 3 RSL and 3 RVac mounts shown. This iteration still needs to be proof and structural tested.
My thoughts too, assuming you meant SN17.x not SN7.x. With at least two months until the orbital attempt, it seems prudent to retire some risk due to the increase from 3 engines to 6.
SN7.x is the current ground test article tank series after the SN2 GTA test tank series was retired. SN17 is a flight article in a limbo state and may or may not proceed with further construction. This one happens to be a scrap tagged article. The thrust puck doesn't need to be the current design to be a pathfinder test article.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 05/19/2021 01:20 am
First, that is NOT a booster dome. Second, it is SCRAP.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/19/2021 01:24 am
First, that is NOT a booster dome. Second, it is SCRAP.
FIRST tell Mary that and SECOND we already know that from earlier posters.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aip on 05/19/2021 02:27 am
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship "orbital" version dome as it is 3 RSL and 3 RVac mounts shown. This iteration still needs to be proof and structural tested.
My thoughts too, assuming you meant SN17.x not SN7.x. With at least two months until the orbital attempt, it seems prudent to retire some risk due to the increase from 3 engines to 6.
SN7.x is the current ground test article tank series after the SN2 GTA test tank series was retired. SN17 is a flight article in a limbo state and may or may not proceed with further construction. This one happens to be a scrap tagged article. The thrust puck doesn't need to be the current design to be a pathfinder test article.
Ah, I was thinking that the original SN17 thrust puck was being scrapped and replaced by a new six engine thrust puck, with the new thrust puck presumably designated SN17.2. But you're saying SpaceX would make a new thrust dome a member of the 7.x test series instead, like 7.1. and 7.2 before it. Thanks for the correction.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/19/2021 06:24 am
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship "orbital" version dome as it is 3 RSL and 3 RVac mounts shown. This iteration still needs to be proof and structural tested.
My thoughts too, assuming you meant SN17.x not SN7.x. With at least two months until the orbital attempt, it seems prudent to retire some risk due to the increase from 3 engines to 6.
SN7.x is the current ground test article tank series after the SN2 GTA test tank series was retired. SN17 is a flight article in a limbo state and may or may not proceed with further construction. This one happens to be a scrap tagged article. The thrust puck doesn't need to be the current design to be a pathfinder test article.
Ah, I was thinking that the original SN17 thrust puck was being scrapped and replaced by a new six engine thrust puck, with the new thrust puck presumably designated SN17.2. But you're saying SpaceX would make a new thrust dome a member of the 7.x test series instead, like 7.1. and 7.2 before it. Thanks for the correction.
Scrap tagged rings were sleeved on the test dome which AFAIU was originally apart of the cancelled SN12-14 group and was up for reassignment. A new SN test series may debut at any time however this far along in the programme there is little point in doing so.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Interro on 05/19/2021 08:00 am
Just released a full re-cap of all the testing that happened during 2020.

The majority of this data was either collected or verified using this forum, so I'd like to say thank you so much to everyone who helps to make this forum so useful!

https://twitter.com/BocaCharts/status/1394917558730514433?s=20 (https://twitter.com/BocaCharts/status/1394917558730514433?s=20)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: BananaForScale on 05/19/2021 01:15 pm
An aft dome used for Raptor Vacuum mount testing was sleeved with a scrap barrel section. The LR 11000 crane lifted its boom as work at the orbital tank farm continued.

Video + Photos by Mary (@BocaChicaGal) for @NASASpaceflight. Edited by me.

https://www.youtube.com/watch?v=dW_JyGq2pGo

The mystery delivery at 8:00 really looks like the back of some kind of seat.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Robotbeat on 05/19/2021 01:54 pm
An aft dome used for Raptor Vacuum mount testing was sleeved with a scrap barrel section. The LR 11000 crane lifted its boom as work at the orbital tank farm continued.

Video + Photos by Mary (@BocaChicaGal) for @NASASpaceflight. Edited by me.

https://www.youtube.com/watch?v=dW_JyGq2pGo

The mystery delivery at 8:00 really looks like the back of some kind of seat.
You're right! Looks like some kind of bucket seat with a net pocket on the back. There's a textured metal plate that looks like it's for feet to stand on and/or rest on.

But I can't put my finger on what it's for. It looks like it might be used. I doubt it's for the actual Starship or even a mockup. The rear pocket seems out of place for a crane seat, but that could be what it is.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/19/2021 04:54 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x style pathfinder test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship dome as it is 3 RSL and 3 RVac mounts shown. The orbital iteration still needs to be proof and structural tested.

EDIT: added clarification to my post.
Yup. A starship dome. But why sleeve it? With all those holes cut into it no chance it'll be for pressure tests. All I can come up with is fit checks. Have we seen a raptor vac at BC?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: gaballard on 05/19/2021 05:16 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x style pathfinder test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship dome as it is 3 RSL and 3 RVac mounts shown. The orbital iteration still needs to be proof and structural tested.

EDIT: added clarification to my post.
Yup. A starship dome. But why sleeve it? With all those holes cut into it no chance it'll be for pressure tests. All I can come up with is fit checks. Have we seen a raptor vac at BC?

Practice for new hires?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/19/2021 06:47 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/19/2021 06:49 pm
An aft dome used for Raptor Vacuum mount testing was sleeved with a scrap barrel section. The LR 11000 crane lifted its boom as work at the orbital tank farm continued.

Video + Photos by Mary (@BocaChicaGal) for @NASASpaceflight. Edited by me.

https://www.youtube.com/watch?v=dW_JyGq2pGo

The mystery delivery at 8:00 really looks like the back of some kind of seat.
I’m wondering about whether it’s a new leg design?  Presumably, even if they intend to catch the two parts, they’ll still need legs of some kind in case of failure.  These could be lightened, less hacked together legs (but not full on fancy reusable ones like they originally planned).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/19/2021 07:00 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)
Correct that it is the distribution manifold surrounded by the still in assembly octaweb inner thrust frame with blast panels for engine out capabilities. The outer thrust frame would provide enough deep gimbal clearance for the octaweb. Some of this has been seen in sections at the other SpaceX sites. I would expect the first completed one to become part of a BN2.x test tank but anything is possible.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/19/2021 07:05 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x style pathfinder test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship dome as it is 3 RSL and 3 RVac mounts shown. The orbital iteration still needs to be proof and structural tested.

EDIT: added clarification to my post.
Yup. A starship dome. But why sleeve it? With all those holes cut into it no chance it'll be for pressure tests. All I can come up with is fit checks. Have we seen a raptor vac at BC?
None reported AFAIK. AFAIU it cannot be transported vertically or horizontal on the normal raptor trailer. A dedicated transport container or specialized trailer would be required.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/19/2021 07:44 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)
Correct that it is the distribution manifold surrounded by the still in assembly octaweb inner thrust frame with blast panels for engine out capabilities. The outer thrust frame would provide enough deep gimbal clearance for the octaweb. Some of this has been seen in sections at the other SpaceX sites. I would expect the first completed one to become part of a BN2.x test tank but anything is possible.

I too expect a pathfinder thrust puck. They could skip this, but IMO they will do that. Additional data on smaller scales is good, but the time spent testing it needs to be considered. Maybe just building BN3, testing it and if it doesn't work without any pathfinder is better for them, maybe they are very sure of their design. Building BN3, even if the scrapped, would be usefull because it would be the first full SH with the new desing (different from BN1). But, building an entire boosteravoiding to test the thrust puck exceeds even the iterative design phylosophy.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lars-J on 05/19/2021 08:06 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

Good catch. There there appears to be pipes made for 28 engines exactly. Perhaps they are moving to a full 28 engines on SuperHeavy quicker than assumed?

This could also just be a test article... Or they could also cap off some of the pipes later.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: livingjw on 05/19/2021 08:13 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

- Pretty sure the aluminum frame is a manufacturing jig.

John
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/19/2021 08:20 pm
Curious why the outlets are of smaller diameter than the outer diameter of the pipes that already routed? Is it because the pipes to be attached are insulated?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 05/19/2021 08:28 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)
Correct that it is the distribution manifold surrounded by the still in assembly octaweb inner thrust frame with blast panels for engine out capabilities. The outer thrust frame would provide enough deep gimbal clearance for the octaweb. Some of this has been seen in sections at the other SpaceX sites. I would expect the first completed one to become part of a BN2.x test tank but anything is possible.

Those panels look more like a support and handling structure than blast panels to me.

Edit: note they are 6061 aluminium sheet, not stainless.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: equiserre on 05/19/2021 08:39 pm
Curious why the outlets are of smaller diameter than the outer diameter of the pipes that already routed? Is it because the pipes to be attached are insulated?

I had the same question. Even more considering that outer raptors, being non-throttlable higher thrust, should have higher flow than the 8 inner ones.  So, inner pipes are shorter, bigger section and lower flow? all that points to lower pressure drop than the outer ones.

But the inner Raptors will have to operate at a low head pressure and startup in the lowest g loading. Maybe that is why they need to be relatively low pressure drop?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: KilroySmith on 05/19/2021 10:53 pm
Curious why the outlets are of smaller diameter than the outer diameter of the pipes that already routed? Is it because the pipes to be attached are insulated?

To my eye, the inner ring and outer ring of pipes are the same diameter.  Note that on the outer pipes there's a large diameter pipe that necks down to a smaller diameter pipe.  The large diameter appears to be the same as the diameter of the inner ring of pipes.  Looking into the smaller diameter pipes, it's unclear if it continues at the same small diameter, or swells to match the larger diameter.  If it stays the same, it's a dual-wall pipe which might suggest that the inner ring is the same.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/19/2021 11:24 pm
Gonna need another dolly
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/19/2021 11:56 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

I don't think it's the "downcomer distribution manifold", just the "distribution manifold".  Like you I forget whether the LOX or the CH4 enters the Raptor 90 degrees to vertical.  I think it's the LOX that enters that way.

So what I'm seeing is 10 large down pipes that would split into a pair of 90 degree elbows feeding LOX and the 20 narrower pipes higher up feed CH4 straight down into the Raptors.


And of course it could be a practice piece instead of a flight article.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/20/2021 01:02 am
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

I don't think it's the "downcomer distribution manifold", just the "distribution manifold".  Like you I forget whether the LOX or the CH4 enters the Raptor 90 degrees to vertical.  I think it's the LOX that enters that way.

So what I'm seeing is 10 large down pipes that would split into a pair of 90 degree elbows feeding LOX and the 20 narrower pipes higher up feed CH4 straight down into the Raptors.


And of course it could be a practice piece instead of a flight article.
I see it a wee bit differently (of course its hard to see the whole thing clearly while its sitting on that aluminum jig - is it really too much to ask that they hang it free from a cable so Mary can get a decent picture?).  To my eye it looks like there are 8 lower pipes feeding the inner ring, and 20 uppers - one each for each of the outer ring Raptors.  This implies Superheavy plumbing is actually quite a bit simpler than some of the schemes being floated once upon a time here.  It looks to me like the down comer will just feed into in one big 1-to-28 manifold, while the lower tank will just feed directly into each engine at its mount, not unlike the current LOX plumbing in Starship (ignoring the LOX header plumbing, of course).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AC in NC on 05/20/2021 01:26 am
To my eye it looks like there are 8 lower pipes feeding the inner ring, and 20 uppers - one each for each of the outer ring Raptors.

This label suggests you're right.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/20/2021 01:57 am
To my eye it looks like there are 8 lower pipes feeding the inner ring, and 20 uppers - one each for each of the outer ring Raptors.

This label suggests you're right.
Good eye!  I hadn't even noticed that label, much less tried to read it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ThatOldJanxSpirit on 05/20/2021 04:26 am
To my eye it looks like there are 8 lower pipes feeding the inner ring, and 20 uppers - one each for each of the outer ring Raptors.

This label suggests you're right.
Good eye!  I hadn't even noticed that label, much less tried to read it.

There are also sharpie marks on the outlets. It’s a bit confusing because some are clearly weld markups, but I see three pipes labeled, from top to bottom, 2, 12, and 21. This is more consistent with two outer rings of ten rather than a ring of twenty.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: EnricoR on 05/20/2021 09:13 am
Goodmorning everyone.

To my incompetent opinion it seems the eight central tubes are larger in diameter because the gimballing system of the central engines will throttle the flow of methane by default.

Sorry ... translated into English with Google.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: 7ginger7 on 05/20/2021 12:16 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: waveney on 05/20/2021 12:43 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts

Icosioctapus?   

(Icosioctagon is the name of 28 sided polygon)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: r8ix on 05/20/2021 12:44 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts

In the Raptor Engine thread, someone used the term Loxtopus, then switched it to Methdusa, which poses the question: do we have a "final" determination of which tank is on top in SH? Recently, we were all leaning towards reverse of SS (i.e. methane on bottom).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: 7ginger7 on 05/20/2021 12:50 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts

In the Raptor Engine thread, someone used the term Loxtopus, then switched it to Methdusa, which poses the question: do we have a "final" determination of which tank is on top in SH? Recently, we were all leaning towards reverse of SS (i.e. methane on bottom).

They're both very creative - I withdraw my motion.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: t3kboi on 05/20/2021 02:01 pm
Crop of the RGV aerial flyover from 5/17 - anyone know what these similar/identical scaffolding setups are/were to be used for?

They are right next to the integration tower assembly.

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: VaBlue on 05/20/2021 02:08 pm
Crop of the RGV aerial flyover from 5/17 - anyone know what these similar/identical scaffolding setups are/were to be used for?

They are right next to the integration tower assembly.

Looks like they might fit inside the tower structure.  This could be a safer way to give the workers a platform to join sections and build out the floors.  Possibly even becoming part of a subfloor?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/20/2021 02:22 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts

In the Raptor Engine thread, someone used the term Loxtopus, then switched it to Methdusa, which poses the question: do we have a "final" determination of which tank is on top in SH? Recently, we were all leaning towards reverse of SS (i.e. methane on bottom).

They're both very creative - I withdraw my motion.
It's clearly the meth head.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/20/2021 02:29 pm
Booster dome on the stand.
Booster dome has been sleeved.
Scrap label on the sleeve.
Potentially a SN7.x style pathfinder test article. I'm not sure where the idea that this is a booster dome came from as it is clearly a Starship dome as it is 3 RSL and 3 RVac mounts shown. The orbital iteration still needs to be proof and structural tested.

EDIT: added clarification to my post.
Yup. A starship dome. But why sleeve it? With all those holes cut into it no chance it'll be for pressure tests. All I can come up with is fit checks. Have we seen a raptor vac at BC?
None reported AFAIK. AFAIU it cannot be transported vertically or horizontal on the normal raptor trailer. A dedicated transport container or specialized trailer would be required.
An over dimensional issue? Source of transport info?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/20/2021 02:44 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

I don't think it's the "downcomer distribution manifold", just the "distribution manifold".  Like you I forget whether the LOX or the CH4 enters the Raptor 90 degrees to vertical.  I think it's the LOX that enters that way.

So what I'm seeing is 10 large down pipes that would split into a pair of 90 degree elbows feeding LOX and the 20 narrower pipes higher up feed CH4 straight down into the Raptors.


And of course it could be a practice piece instead of a flight article.
FWIW, LOX comes into the raptor from straight above. CH4 turbo pump is on the side with the inlet facing up. The feed line has flex sections and elbows to get everything hooked up. Since we haven't seen one of the new raptors installed (um, uh?) the new CH4 hookup will be a bit different in unknown ways. LOX probably unchanged.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SpaceXOrbit on 05/20/2021 02:50 pm
Is SpaceX planning to add more TPS on SN15? I heard that SN17 was to have full TPS and 16 was to have partial. Did the success of SN15 change anything? Is SN16 going to have full TPS now and 15 will get more?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/20/2021 02:50 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts
Calamari Assembly?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: SpaceXOrbit on 05/20/2021 02:52 pm
I heard that SN17 will be scrapped after SN15s success. Will SpaceX now put more TPS on SN15 and completely cover SN16?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/20/2021 02:54 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts

In the Raptor Engine thread, someone used the term Loxtopus, then switched it to Methdusa, which poses the question: do we have a "final" determination of which tank is on top in SH? Recently, we were all leaning towards reverse of SS (i.e. methane on bottom).

They're both very creative - I withdraw my motion.
It's clearly the meth head.
lol. You win
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: StarshipSLS on 05/20/2021 03:00 pm
I heard that SN17 will be scrapped after SN15s success. Will SpaceX now put more TPS on SN15 and completely cover SN16?
No, the first Starship with a full TPS will be SN20. (SN17-19 will be scrapped and SN16 is now just a backup Starship if they can't refly SN15.)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/20/2021 03:01 pm
Crop of the RGV aerial flyover from 5/17 - anyone know what these similar/identical scaffolding setups are/were to be used for?

They are right next to the integration tower assembly.

Looks entrance ramps for an elevator. Should be discussed in facilities though.

Edit, incorrect guess. Correct info https://forum.nasaspaceflight.com/index.php?topic=49086.msg2240977#msg2240977
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: DavP on 05/20/2021 03:05 pm
Crop of the RGV aerial flyover from 5/17 - anyone know what these similar/identical scaffolding setups are/were to be used for?

They are right next to the integration tower assembly.

Look at this message in other thread

https://forum.nasaspaceflight.com/index.php?topic=52398.msg2240928#msg2240928
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: sebk on 05/20/2021 03:30 pm
Booster part?
Orbital launch table progress.
Could this be anything but the downcomer (LOX? LCH4? I lost track) distribution manifold for BN3?

Image credit: Mary (obviously!)

If it doesn't have a nickname yet, I think we need to see some 'New Cthulhu assembly for BN6 spotted' type posts

Stealing from reddit:

Methusa (as Methane Medusa)
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Tangilinear Interjar on 05/20/2021 03:31 pm
Crop of the RGV aerial flyover from 5/17 - anyone know what these similar/identical scaffolding setups are/were to be used for?

They are right next to the integration tower assembly.
Those are scaffold platforms that will probably be mounted at the top of each tower column so welding and concrete work can be done at each section integration point.

BTW, there's another thread for this but don't know how to point at it.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/20/2021 04:47 pm
Crop of the RGV aerial flyover from 5/17 - anyone know what these similar/identical scaffolding setups are/were to be used for?

They are right next to the integration tower assembly.
Those are scaffold platforms that will probably be mounted at the top of each tower column so welding and concrete work can be done at each section integration point.

BTW, there's another thread for this but don't know how to point at it.

Looks like you are correct. Here is the link:

https://forum.nasaspaceflight.com/index.php?topic=49086.msg2240977#msg2240977
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: FutureSpaceTourist on 05/20/2021 06:31 pm
Fingers crossed

twitter.com/austinbarnard45/status/1395412146691969027

Quote
Hey @elonmusk, is there a possibility for a StarShip presentation this year? A lot has happened since Mk1 and I’m sure the community would love to hear you speak about the direction the program is headed. Especially since the team has flew and landed a full scale prototype.

https://twitter.com/elonmusk/status/1395433890806845443

Quote
Sure

Edit to add:

twitter.com/austinbarnard45/status/1395412147493122049

Quote
Would be cool for you to speak in front of SN15, since it is the first StarShip out of the thousands to come to have landed. (After it survives its next flight😉)

https://twitter.com/elonmusk/status/1395433944510734337

Quote
Good idea
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/20/2021 06:59 pm
I heard that SN17 will be scrapped after SN15s success. Will SpaceX now put more TPS on SN15 and completely cover SN16?
No, the first Starship with a full TPS will be SN20. (SN17-19 will be scrapped and SN16 is now just a backup Starship if they can't refly SN15.)

How much solid information do we have about sn17 been scrapped an sn16 been a bakup for sn15 reflight?

I agree with sn17 been scrapped, but I'd like to note that it is an opinion supported by a few facts, not a undisputable fact.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jlv on 05/20/2021 09:01 pm
sn17 been scrapped, but I'd like to note that it is an opinion supported by a few facts, not a undisputable fact.
I think it's ok to say there is L2 information backing this up.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: mandrewa on 05/20/2021 10:12 pm
I heard that SN17 will be scrapped after SN15s success. Will SpaceX now put more TPS on SN15 and completely cover SN16?
No, the first Starship with a full TPS will be SN20. (SN17-19 will be scrapped and SN16 is now just a backup Starship if they can't refly SN15.)

How much solid information do we have about sn17 been scrapped an sn16 been a bakup for sn15 reflight?

I agree with sn17 been scrapped, but I'd like to note that it is an opinion supported by a few facts, not a undisputable fact.

I don't think anything is indisputable until it actually happens.  Suppose SpaceX has already made the decision to scrap SN17.  That doesn't mean it will actually happen because they could change their mind.  Why might they change their mind?  Well so much is in flux.

Right now the big push is to get the orbital launch site completed.  I don't expect to see SN15 relaunched, if it is relaunched, until after the integration tower has been assembled and the launch table has been put in place -- because that's the point where they will no longer need at least two of the really big cranes they have onsite now and which are very expensive to keep around.

Once that happens they will probably ask themselves whether the orbital launch site construction schedule is the biggest barrier to doing the first orbital launch in July.  If it isn't, then they will probably take time out to do another 10 km hop.

And then they will be back to building the orbital launch site, and building the BN3 SuperHeavy and the SN20 Starship.

But if by that point it has become clear that all three of these efforts are going well and that something else is the real barrier to doing an orbital launch in July or August, say for instance, the FAA's permission, then quite possibly they will decide to do more Starship suborbital launches with either the SN15 or SN16, because why not?  They learn something from every one of these launches and really they are spending the money regardless since their main cost is their workforce.

And thus if other things are continuing to delay the first orbital launch it's conceivable they might discover that they want to launch SN17.  Or it could be that they really know that they don't want to launch SN17 because they already know enough now to know its design is obsolete and therefore not interesting.  And in that case they might launch SN20, or one of it's siblings, 20 km up instead.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jose m on 05/21/2021 03:15 am
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h.

If in a second jump of the SN15 the pending issues for these tests are resolved, the next thing is to go to the SN20 with BN3, where they must go from 3 raptors to 34 and
from 270 Ton of fuel to 4600 Ton, from 250k / h current maximum speed to 30,000 K / h, really tremendous leap that they have to give to be orbital  :-[
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baltrum on 05/21/2021 09:17 am
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h.

If in a second jump of the SN15 the pending issues for these tests are resolved, the next thing is to go to the SN20 with BN3, where they must go from 3 raptors to 34 and
from 270 Ton of fuel to 4600 Ton, from 250k / h current maximum speed to 30,000 K / h, really tremendous leap that they have to give to be orbital  :-[

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edzieba on 05/21/2021 10:41 am
Nosecone outside tent 3.
New nose has yet another attachment hardpoint setup: pin is now inserted vertically rather than horizontally, dogbones free to rotate sideways but not vertically (previously constrained sideways but free to rotate vertically).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/21/2021 10:50 am
And in that case they might launch SN20, or one of it's siblings, 20 km up instead.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall...

Where does this number 20 km come from?

The FAA seems to have evaluated Starship test hops up to 30 km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf), page 3), and that was back in 2019.
So it seems highly likely the FAA would approve SS to land at Boca Chica from 30 kilometers.

Also, it seems like lower atmospheric density would affect the speed that Starship falls.
So maybe it would fall faster at first and then slow down as atmospheric density increases.
With this in mind, it seems to me that at altitude of 30km would be an interesting test flight.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: hkultala on 05/21/2021 01:36 pm
Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h.

450 km/h = 125 m/s.

Assuming no drag, it would take about 12.5 second to accelerate to that velocity at earth gravity. 12.5 is quite much more than "few".

But, because of drag, it takes much longer as drag starts to make the acceleration slower.

And, the terminal velocity is much faster the higher the vehicle is, as there is less drag and air is much thinner at higher altitudes.

So higher altitude practically always means considerably higher velocity.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: capoman on 05/21/2021 01:57 pm
I think a 20km flight would be useful in that they could work the Raptors a bit harder. My understanding is they were throttling Raptors to avoid blowing past 10kms, not just in sequencing alone.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 05/21/2021 02:04 pm
Nosecone outside tent 3.
New nose has yet another attachment hardpoint setup: pin is now inserted vertically rather than horizontally, dogbones free to rotate sideways but not vertically (previously constrained sideways but free to rotate vertically).

  Not seeing a major difference with what has been in place on most recent starships. Including a bocachicagal picture of SN16 in highbay that seems to show similar set up to new nose cone at construction tent (second picture). Looks like there are some different style connectors that get attached to the core unit inside starship, but core unit looks the same (to my eye). 

Link to full size photos in daily update thread:
SN16 in the high bay.
Boot prints on aft flap.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: quagmire on 05/21/2021 04:11 pm
https://twitter.com/considercosmos/status/1395772869909508096

Quote
Raptor drop in progress on #sn15

https://twitter.com/starshipgazer/status/1395773062465867780

Quote
Raptor 54 coming out:

Was 54 the one that didn't relight? 61 was the one facing the camera from the views we saw.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baking on 05/21/2021 04:47 pm
Nosecone outside tent 3.
New nose has yet another attachment hardpoint setup: pin is now inserted vertically rather than horizontally, dogbones free to rotate sideways but not vertically (previously constrained sideways but free to rotate vertically).
Not seeing a major difference with what has been in place on most recent starships.
Maybe I'm missing something, but the significance of the connection type may be a sign of a different lifting/release mechanism for SN20 which will almost certainly need to be detached from the crane without manual intervention after stacking on the booster.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: AstroDave on 05/21/2021 05:45 pm
Nosecone outside tent 3.
New nose has yet another attachment hardpoint setup: pin is now inserted vertically rather than horizontally, dogbones free to rotate sideways but not vertically (previously constrained sideways but free to rotate vertically).
Not seeing a major difference with what has been in place on most recent starships.
Maybe I'm missing something, but the significance of the connection type may be a sign of a different lifting/release mechanism for SN20 which will almost certainly need to be detached from the crane without manual intervention after stacking on the booster.

  Agreed that a convenient release device would be advantageous. Additionally, future hard points will need to be retracted/isolated beneath TPS tiles in some manner. Whatever process that the SpaceX team uses, it has to entail the ability to easily hook back up as well. Having a tower nearby offers many more design possibilities for expediting the hook/unhook process.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/21/2021 06:16 pm
Nosecone outside tent 3.
New nose has yet another attachment hardpoint setup: pin is now inserted vertically rather than horizontally, dogbones free to rotate sideways but not vertically (previously constrained sideways but free to rotate vertically).
Not seeing a major difference with what has been in place on most recent starships.
Maybe I'm missing something, but the significance of the connection type may be a sign of a different lifting/release mechanism for SN20 which will almost certainly need to be detached from the crane without manual intervention after stacking on the booster.

  Agreed that a convenient release device would be advantageous. Additionally, future hard points will need to be retracted/isolated beneath TPS tiles in some manner. Whatever process that the SpaceX team uses, it has to entail the ability to easily hook back up as well. Having a tower nearby offers many more design possibilities for expediting the hook/unhook process.

Yes, I agree too.

But they might make an exception for sn20.  I'm not an expert of labour regulation, is somewhat illegal/very expensive due to compensation making workers work at those heights?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/21/2021 06:59 pm
Yes, I agree too.

But they might make an exception for sn20.  I'm not an expert of labour regulation, is somewhat illegal/very expensive due to compensation making workers work at those heights?
Nope - any height above 3 meters is likely to kill you if you fall.  An extra 100m on top of that isn't going to make much odds if you fall.  The requirements for working at height are pretty well known and understood by SpaceX (they do it all the time).
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Yggdrasill on 05/21/2021 07:11 pm
Nope - any height above 3 meters is likely to kill you if you fall.  An extra 100m on top of that isn't going to make much odds if you fall.
That is really not true. Most people survive a fall of 3 meters or 10 feet. I would think most survive such a fall without breaking anything. It *can* kill you, but so can falling from 2 meters.

At something like 300 meters you will reach terminal velocity, so there's basically no difference in falling 300 meters or 10,000 meters. From 100 meters you'll be at close to terminal velocity when you hit the ground, but it's still entirely possible to survive if something breaks your fall or you hit a soft surface.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Lee Jay on 05/21/2021 07:24 pm
Nope - any height above 3 meters is likely to kill you if you fall.  An extra 100m on top of that isn't going to make much odds if you fall.
That is really not true. Most people survive a fall of 3 meters or 10 feet. I would think most survive such a fall without breaking anything. It *can* kill you, but so can falling from 2 meters.

Most people survive a *jump* from 10 feet with a controlled landing.  A fall from that height, where you land at a random orientation, is very likely to cause significant injury or death.  In fact, OSHA reduced the platform height requiring a rail from 6 feet to 4 feet because falls from 6 feet were seriously hurting and/or killing people.  I know someone, who was middle-aged, athletic and healthy, who fell from standing (feet on the ground) and was in the hospital for 2 weeks with a spiral fracture of the femur.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: aero on 05/21/2021 07:47 pm
Quote
At something like 300 meters you will reach terminal velocity, so there's basically no difference in falling 300 meters or 10,000 meters.

Oh yes there is. At 300 meters you only have 12 seconds to worry before the smash. A fall from 10,000 meters gives you like 200 seconds,  plenty of time to worry, s**t your pants and even write a note if you have pencil and paper with you.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: matt_ellis on 05/21/2021 08:16 pm
Quote
At something like 300 meters you will reach terminal velocity, so there's basically no difference in falling 300 meters or 10,000 meters.

Oh yes there is. At 300 meters you only have 12 seconds to worry before the smash. A fall from 10,000 meters gives you like 200 seconds,  plenty of time to worry, s**t your pants and even write a note if you have pencil and paper with you.
Slightly ot, but it appears a flight attendant (Vesna Vulovi) has survived a fall from 10,000m
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Oersted on 05/21/2021 08:40 pm
She was inside the fuselage remnants of the plane that fell, so not in free fall all by herself.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Yggdrasill on 05/21/2021 09:16 pm
There are people who have survived falling from a plane when their parachutes didn't deploy. But they hit a tree or something that broke their fall. And then there's this, of course:

https://youtu.be/aPC_h9Vmlxw
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Yggdrasill on 05/21/2021 09:27 pm
Most people survive a *jump* from 10 feet with a controlled landing.  A fall from that height, where you land at a random orientation, is very likely to cause significant injury or death.  In fact, OSHA reduced the platform height requiring a rail from 6 feet to 4 feet because falls from 6 feet were seriously hurting and/or killing people.  I know someone, who was middle-aged, athletic and healthy, who fell from standing (feet on the ground) and was in the hospital for 2 weeks with a spiral fracture of the femur.
There's definitely a non-negligible chance of death if you fall from 3 meters, but it's still a stretch to say it's very likely to result in death.

I'm pretty sure the chance of death is under 1%. It's understandable that there are strict OSHA regulations, because such falls are fairly common, and there would be lot of deaths without safety regulations, but again, it's quite a stretch to say death is very likely.

Personally, I've fallen head first from roughly 3 meters  in my childhood. I was fine. I've also had several falls at around 2 meters, but that was usually feet first.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: smndk on 05/21/2021 09:37 pm
Stop
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: beelsebob on 05/21/2021 09:41 pm
Most people survive a *jump* from 10 feet with a controlled landing.  A fall from that height, where you land at a random orientation, is very likely to cause significant injury or death.  In fact, OSHA reduced the platform height requiring a rail from 6 feet to 4 feet because falls from 6 feet were seriously hurting and/or killing people.  I know someone, who was middle-aged, athletic and healthy, who fell from standing (feet on the ground) and was in the hospital for 2 weeks with a spiral fracture of the femur.
There's definitely a non-negligible chance of death if you fall from 3 meters, but it's still a stretch to say it's very likely to result in death.

I'm pretty sure the chance of death is under 1%. It's understandable that there are strict OSHA regulations, because such falls are fairly common, and there would be lot of deaths without safety regulations, but again, it's quite a stretch to say death is very likely.

Personally, I've fallen head first from roughly 3 meters  in my childhood. I was fine. I've also had several falls at around 2 meters, but that was usually feet first.

Okay, so I looked it up, and you lot are right - the death rates from 1 floor are lower than I thought. 

https://link.springer.com/article/10.1007/s00068-017-0799-1

Either way, as it stands, SpaceX is having people work at somewhere around 30m to fit the FTS.  30m is well into the range where OSHA is gonna be interested in having people clip on etc.  They require fall protection for anyone working above 5 feet in a shipyard (technically true?), or 6 feet for construction.  They don't require *additional* fall protection anywhere up to 100m or beyond.

So long story short - there are no additional issues with having people working that high up.  They already have to have safety equipment in place for even small elevations.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: zubenelgenubi on 05/21/2021 10:15 pm
Moderator:
Rates of death or injury, falling from this or that height, are off-topic.

OSHA regulations could be on-topic, as specifically relating to prototype work.

Otherwise, stop.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: jose m on 05/22/2021 03:09 am
Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h.

450 km/h = 125 m/s.

Assuming no drag, it would take about 12.5 second to accelerate to that velocity at earth gravity. 12.5 is quite much more than "few".

But, because of drag, it takes much longer as drag starts to make the acceleration slower.

And, the terminal velocity is much faster the higher the vehicle is, as there is less drag and air is much thinner at higher altitudes.

So higher altitude practically always means considerably higher velocity.

The aerodynamics of the vehicle limits the maximum speed of fall to 125 m / s, I saw videos with telemetry that show it, if it falls from higher, starting from zero speed, the same must happen.
But if it falls from orbit it changes, because the initial speed would be 30,000 k / h approx.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/22/2021 04:25 am
Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h.

450 km/h = 125 m/s.

Assuming no drag, it would take about 12.5 second to accelerate to that velocity at earth gravity. 12.5 is quite much more than "few".

But, because of drag, it takes much longer as drag starts to make the acceleration slower.

And, the terminal velocity is much faster the higher the vehicle is, as there is less drag and air is much thinner at higher altitudes.

So higher altitude practically always means considerably higher velocity.

The aerodynamics of the vehicle limits the maximum speed of fall to 125 m / s, I saw videos with telemetry that show it, if it falls from higher, starting from zero speed, the same must happen.
But if it falls from orbit it changes, because the initial speed would be 30,000 k / h approx.
No.  At higher altitude, the reduced atmospheric pressure results in lower drag forces at a given velocity.  Terminal velocity of a dropped object therefore increases continuously with the altitude from which the object is released.  Once an object falling from high altitude reaches terminal velocity, its rate of fall will then progressively decrease as it experiences progressively higher atmospheric pressure and thus higher drag forces.   This is independent of any lateral velocity an object may have, e.g., orbital velocity.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: waveney on 05/22/2021 07:19 am
Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h.

450 km/h = 125 m/s.

Assuming no drag, it would take about 12.5 second to accelerate to that velocity at earth gravity. 12.5 is quite much more than "few".

But, because of drag, it takes much longer as drag starts to make the acceleration slower.

And, the terminal velocity is much faster the higher the vehicle is, as there is less drag and air is much thinner at higher altitudes.

So higher altitude practically always means considerably higher velocity.

The aerodynamics of the vehicle limits the maximum speed of fall to 125 m / s, I saw videos with telemetry that show it, if it falls from higher, starting from zero speed, the same must happen.
But if it falls from orbit it changes, because the initial speed would be 30,000 k / h approx.

I think they will use this configuration for 4 or 5 tower sections, then it will grow.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: vaporcobra on 05/22/2021 07:49 am
A new dome outside the front of the tents.

Sneaky little "B2 FWD" on that booster forward dome. Or B2something FsomethingD, at least...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/22/2021 12:10 pm
In the Master update production thread there is a picture (from bocachicagal) of sn21 common dome, but in the description in the post by bocachicagal is written that it is not sn21 dome, but rather a gse dome.
What happened? Why it is labeled sn21 if it is for gse 5?


https://forum.nasaspaceflight.com/index.php?topic=52398.1580
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alvian@IDN on 05/22/2021 12:26 pm
In the Master update production thread there is a picture (from bocachicagal) of sn21 common dome, but in the description in the post by bocachicagal is written that it is not sn21 dome, but rather a gse dome.
What happened? Why it is labeled sn21 if it is for gse 5?


https://forum.nasaspaceflight.com/index.php?topic=52398.1580
Because if you look closely they have relabelled it
Title: Re: Starship SN15 Test Launch Campaign - UPDATES
Post by: CorvusCorax on 05/22/2021 02:53 pm
Sorry, I’ve removed the picture of SN15 Raptors after landing, which has been circulating the web for a while.

NSF has good relationships with companies across the industry, including SpaceX. To maintain those relationships we only post pictures that are either released / approved by them or are obtained from publicly accessible areas. Photos / videos obtained either through trespass or unapproved employee / contractor leaks are not for this site.

Apologies if I’ve missed any official release / approval of the image. I’ll reinstate the post if I have.

Which image was this? this here?

Quote
https://twitter.com/PPathole/status/1395932262764400643

Because if so, Elon answering to it kinda gives sort-of-implicit approval. He wouldn't answer to a post if SpaceX legal team were simultaneous trying to take it down.

Quote
https://twitter.com/elonmusk/status/1396049958000685060

Or is this an older/different image of raptor?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/22/2021 03:06 pm
In the Master update production thread there is a picture (from bocachicagal) of sn21 common dome, but in the description in the post by bocachicagal is written that it is not sn21 dome, but rather a gse dome.
What happened? Why it is labeled sn21 if it is for gse 5?


https://forum.nasaspaceflight.com/index.php?topic=52398.1580
Because if you look closely they have relabelled it
Even without the label, this was clearly not a SNx common dome.  Common domes have a very large opening in the middle where they stuff the methane header tank, whereas this one has a complete dome cap, a feature of both forward domes and GSE domes.  The welded-in fittings identify this one as a GSE upper dome.

I didn't catch the label at first.  It looks like they relabeled it with a marker that washed off in the rain or something, but on closer inspection, you can see the printed label is faintly crossed off and there is a faint "GSE5 FWD" written below.

Photo credit: Mary
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: ugordan on 05/22/2021 03:07 pm
Or is this an older/different image of raptor?

It's the SN15 one. The fact it's sitting on the ground with the legs deployed and is still in one piece kind of gives that away.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/22/2021 03:25 pm
In the Master update production thread there is a picture (from bocachicagal) of sn21 common dome, but in the description in the post by bocachicagal is written that it is not sn21 dome, but rather a gse dome.
What happened? Why it is labeled sn21 if it is for gse 5?


https://forum.nasaspaceflight.com/index.php?topic=52398.1580
Because if you look closely they have relabelled it



Even without the label, this was clearly not a SNx common dome.  Common domes have a very large opening in the middle where they stuff the methane header tank, whereas this one has a complete dome cap, a feature of both forward domes and GSE domes.  The welded-in fittings identify this one as a GSE upper dome.

I didn't catch the label at first.  It looks like they relabeled it with a marker that washed off in the rain or something, but on closer inspection, you can see the printed label is faintly crossed off and there is a faint "GSE5 FWD" written below.

Photo credit: Mary

Thanks! Now I see it. My brain was apparently too focused on the label to note the thinner "gs5" label written.

As you say it could not be an snX common dome, brcause there wasn't place for a methane header.
Probably someone simply mislabelled the dome in the first place with "sn21", but even if it is not part of sn21 since the label was printed, we known that the first section of (IIRC)sn21 is coming! Another starship is being concived!

BTW, it is always impressing how a paper is small compared to SS
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/22/2021 03:32 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.
Title: Re: Starship SN15 Test Launch Campaign - UPDATES
Post by: su27k on 05/22/2021 03:57 pm
Sorry, I’ve removed the picture of SN15 Raptors after landing, which has been circulating the web for a while.

NSF has good relationships with companies across the industry, including SpaceX. To maintain those relationships we only post pictures that are either released / approved by them or are obtained from publicly accessible areas. Photos / videos obtained either through trespass or unapproved employee / contractor leaks are not for this site.

Apologies if I’ve missed any official release / approval of the image. I’ll reinstate the post if I have.

Which image was this? this here?

Quote
https://twitter.com/PPathole/status/1395932262764400643

Because if so, Elon answering to it kinda gives sort-of-implicit approval. He wouldn't answer to a post if SpaceX legal team were simultaneous trying to take it down.

Quote
https://twitter.com/elonmusk/status/1396049958000685060

Or is this an older/different image of raptor?

The image Elon answered to is the same one that was taken down from NSF.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Paul_G on 05/22/2021 04:33 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.

If its not a leg skirt, could it be the cutouts and necessary reinforcements for grid fin mounts at the top of the booster?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/22/2021 04:41 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.

If its not a leg skirt, could it be the cutouts and necessary reinforcements for grid fin mounts at the top of the booster?
Sure - why not?  That's probably just as likely as landing leg cutouts.  Hopefully some of the locals can get better pictures.  Better yet, it'll get rolled outside and someone can get a clear shot ... preferably with a label!
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: russianhalo117 on 05/22/2021 04:42 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.

If its not a leg skirt, could it be the cutouts and necessary reinforcements for grid fin mounts at the top of the booster?
If it was BN related I was thinking either the Tail Service Mast Umbilical Arm/Hold down arms if it was the skirt. The holes at the top do not seem large enough for the grid fins. Could be the catchment hook mechanism connection. To early to tell.

SN I would not know.
Title: Re: Starship SN15 Test Launch Campaign - UPDATES
Post by: VaBlue on 05/22/2021 04:45 pm
Sorry, I’ve removed the picture of SN15 Raptors after landing, which has been circulating the web for a while.

NSF has good relationships with companies across the industry, including SpaceX. To maintain those relationships we only post pictures that are either released / approved by them or are obtained from publicly accessible areas. Photos / videos obtained either through trespass or unapproved employee / contractor leaks are not for this site.

Apologies if I’ve missed any official release / approval of the image. I’ll reinstate the post if I have.

Which image was this? this here?

Because if so, Elon answering to it kinda gives sort-of-implicit approval. He wouldn't answer to a post if SpaceX legal team were simultaneous trying to take it down.

Nobody said SpaceX was legally trying to take it down, all the mods did was remove an image that may have been taken and publicized without SpaceX's tacit approval.  Why is there any problem with NSF landing on the side of preserving its relationship with one of its primary corporate focuses?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/22/2021 04:51 pm
In the Master update production thread there is a picture (from bocachicagal) of sn21 common dome, but in the description in the post by bocachicagal is written that it is not sn21 dome, but rather a gse dome.
What happened? Why it is labeled sn21 if it is for gse 5?


https://forum.nasaspaceflight.com/index.php?topic=52398.1580
Because if you look closely they have relabelled it



Even without the label, this was clearly not a SNx common dome.  Common domes have a very large opening in the middle where they stuff the methane header tank, whereas this one has a complete dome cap, a feature of both forward domes and GSE domes.  The welded-in fittings identify this one as a GSE upper dome.

I didn't catch the label at first.  It looks like they relabeled it with a marker that washed off in the rain or something, but on closer inspection, you can see the printed label is faintly crossed off and there is a faint "GSE5 FWD" written below.

Photo credit: Mary

Thanks! Now I see it. My brain was apparently too focused on the label to note the thinner "gs5" label written.

As you say it could not be an snX common dome, brcause there wasn't place for a methane header.
Probably someone simply mislabelled the dome in the first place with "sn21", but even if it is not part of sn21 since the label was printed, we known that the first section of (IIRC)sn21 is coming! Another starship is being concived!

BTW, it is always impressing how a paper is small compared to SS
I hear ya.  I was confused by the labeling as well, which appeared to be clearly wrong.  Even after I read Alvian@IDN's comment that it had been relabeled, I still didn't see it.  But it was clearly a GSE FWD dome, and I didn't pay much more attention.  It was only after about the 5th inspection of the image that I finally saw the re-labeling.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 05/22/2021 05:09 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.

Where was this posted first? Thank you.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/22/2021 05:21 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.

Where was this posted first? Thank you.
Third picture of this - Re: SpaceX Boca Chica - Production Updates - MASTER Thread (4) « Reply #1596 on: 05/21/2021 08:32 pm » https://forum.nasaspaceflight.com/index.php?topic=52398.msg2241778#msg2241778
Title: Re: Starship SN15 Test Launch Campaign - UPDATES
Post by: Alpha Lima on 05/22/2021 09:06 pm

Because if so, Elon answering to it kinda gives sort-of-implicit approval. He wouldn't answer to a post if SpaceX legal team were simultaneous trying to take it down.


Lol, you must be new here. Elon doing something at complete cross-purposes to what the legal team is doing would be 100% on-brand for him.


Edit: I received a message about "you must be new here" coming across as insulting, and I'd like to retract that, which I did not at all mean literally.  I am the one who is new here, and as part of that newness I was confusing this place with other forums where "you must be new here" is a well-worn good-natured idiom.  On those forums, I've followed the litigation over the last few years involving Elon Musk, Tesla, SolarCity, the SEC, labor unions, a Musk-described "pedo guy", and sundry other characters. The details are off-topic here, but the overarching theme has been that Elon Musk is just not a person about whom it makes sense to reason "Well, this can't be right, because that would mean he's not on the same page as his company's lawyers".
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: CamiloPasin on 05/22/2021 10:49 pm
Anyone have any thoughts on the weird cutout and reinforcing on this section Mary spotted in tent 1?  I don't think we've seen anything quite like this before.  The only idea I can come up with is that its somehow related to upgraded landing legs, but I'm basically stumped.

Edit: forgot to attache the picture!  Photo credit: Mary.

Where was this posted first? Thank you.

Third picture of this - Re: SpaceX Boca Chica - Production Updates - MASTER Thread (4) « Reply #1596 on: 05/21/2021 08:32 pm » https://forum.nasaspaceflight.com/index.php?topic=52398.msg2241778#msg2241778

Thank you, I totally missed that one.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Dave G on 05/23/2021 09:34 am
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: edzieba on 05/23/2021 12:16 pm
The GSE 5 forward dome has been sleeved.
Pic of the section inside tent 1.
Cropped version of the new 'cutout' with the image levels raised inside. Looks like there is an identical cutout opposite or near opposite.
With the beefy framing and further reinforced corners, I would expect these are permanent 'holes' rather than frames for something load-bearing to be installed in the centre. Grid-fins for Super Heavy would be a good bet, if there was just the one aperture I'd have gone with an exterior hatch for Starship.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baltrum on 05/23/2021 12:41 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/23/2021 12:53 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere

It’s substantially easier to maintain attitude and attitude control without atmosphere. Current prototype  Starship is peppered with N2 jets fore and aft for exactly this purpose already; the fact that they can control attitude for the initial flip swan dive maneuver at lower altitude, despite the higher atmospheric density and upper-level winds, retires most or all of the basic risk there.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baltrum on 05/23/2021 12:59 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere

It’s substantially easier to maintain attitude and attitude control without atmosphere. Current prototype  Starship is peppered with N2 jets fore and aft for exactly this purpose already; the fact that they can control attitude for the initial flip swan dive maneuver at lower altitude, despite the higher atmospheric density and upper-level winds, retires most or all of the basic risk there.

The RCS system has been untested so far
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Herb Schaltegger on 05/23/2021 02:20 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere

It’s substantially easier to maintain attitude and attitude control without atmosphere. Current prototype  Starship is peppered with N2 jets fore and aft for exactly this purpose already; the fact that they can control attitude for the initial flip swan dive maneuver at lower altitude, despite the higher atmospheric density and upper-level winds, retires most or all of the basic risk there.

The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: billh on 05/23/2021 02:54 pm
The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.
Last I heard, the cold gas thrusters are just for the prototype. If that's true, then the methane/oxygen thrusters have yet to be flown. I think the main challenges there will be managing the high pressure gas supply in connection with the autogenous pressurization system.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Alberto-Girardi on 05/23/2021 03:05 pm
The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.
Last I heard, the cold gas thrusters are just for the prototype. If that's true, then the methane/oxygen thrusters have yet to be flown. I think the main challenges there will be managing the high pressure gas supply in connection with the autogenous pressurization system.
I agree. IMO the methox RCS aren't the most important thing right now, the N2 ones might be fine for the first orbital flight, since it is only one orbit long, and there are at least a few tons of spare payload for addded "propellant*"(most probably the 1st orbital flight won't have the vehicle fully fueled to use less raptors fot the SH, so the payload to orbit won't be the ~100 tons of the operative configuration)

* is the N2 used by the RCS considerable their propellant?
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/23/2021 03:12 pm
The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.
Last I heard, the cold gas thrusters are just for the prototype. If that's true, then the methane/oxygen thrusters have yet to be flown. I think the main challenges there will be managing the high pressure gas supply in connection with the autogenous pressurization system.
I think what Herb was getting at is that RCS in general are a very well understood problem.  True the particular hot gas methox thrusters they end up with are untested in flight (if they even exist yet), but basic pressure fed engines are so simple that those are also essentially a solved, or at least readily solvable, problem.  As for gas management, every chemically fueled RCS is fuel-limited at some point, so size your initial COPVs to do the whole job. I suspect the autogeneous pressurization system is capable of producing gas at several hundred bar, in which case, every time you run the raptors you have an opportunity to recharge the RCS, but you can sort that out after initial operation capacity has been achieved.  If there is ever a need to recharge RCS without wanting to start the Raptors, an electric compressor and solar power should be able to do it from the main tanks or header tank boil off - not fast or efficient, but I only see this being an issue during situations like interplanetary cruise or long holds on orbit, so that should also be a non-issue.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Barry Brisco on 05/23/2021 03:18 pm
The RCS system has been untested so far
Check the streams of the Starship test flights, I think that RCS firings are visible, or is this a pressure adjust meant release from the LOX header tank? Here is SN8:

Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/23/2021 03:20 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere

It’s substantially easier to maintain attitude and attitude control without atmosphere. Current prototype  Starship is peppered with N2 jets fore and aft for exactly this purpose already; the fact that they can control attitude for the initial flip swan dive maneuver at lower altitude, despite the higher atmospheric density and upper-level winds, retires most or all of the basic risk there.
Opinion: yes and no. At 12km and some undetermined velocity aero surfaces have more influence than cold gas thrusters. At 30km it's the reverse and aero surfaces give a degree of trim that might be more subtle than cold gas. The relationship changes with altitude and velocity and has surely been modeled. Testing this would validate the model. As I said, opinion.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/23/2021 03:32 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere

It’s substantially easier to maintain attitude and attitude control without atmosphere. Current prototype  Starship is peppered with N2 jets fore and aft for exactly this purpose already; the fact that they can control attitude for the initial flip swan dive maneuver at lower altitude, despite the higher atmospheric density and upper-level winds, retires most or all of the basic risk there.

The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.
ISTM not so much a challenge as something to be explored, especially if there is an opportunity that does not unduly interfere with other operations. F9 has cold gas history but no history of anything remotely like the fins. It's not only the two systems but the interaction of the systems in a regime that SS has yet to encounter. Probably not worth testing if it ties up the program, but if program impact is minimal...
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: cdebuhr on 05/23/2021 03:38 pm
The RCS system has been untested so far
Check the streams of the Starship test flights, I think that RCS firings are visible, or is this a pressure adjust meant release from the LOX header tank? Here is SN8:
That screen grab looks like it came from the SN8 highlights video.  You get a much better look at RCS firings from the archived version of the whole SN8 livestream:
https://youtu.be/ap-BkkrRg-o?t=6780
There was lots of nose RCS activity starting at about T+4m49s.  Most of the video is a pre-launch hold, but if you go to about 1h53m, you'll be in the right spot.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: OTV Booster on 05/23/2021 03:43 pm
The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.
Last I heard, the cold gas thrusters are just for the prototype. If that's true, then the methane/oxygen thrusters have yet to be flown. I think the main challenges there will be managing the high pressure gas supply in connection with the autogenous pressurization system.
I agree. IMO the methox RCS aren't the most important thing right now, the N2 ones might be fine for the first orbital flight, since it is only one orbit long, and there are at least a few tons of spare payload for addded "propellant*"(most probably the 1st orbital flight won't have the vehicle fully fueled to use less raptors fot the SH, so the payload to orbit won't be the ~100 tons of the operative configuration)

* is the N2 used by the RCS considerable their propellant?
Yup, N2 is considered propellant. There is speculation that hot gas thrusters could be used in a cold gas mode for fine control, during refueling for example.


We have near zero information on hot gas thruster development. Behind this wall of ignorance could be anything from no current development to ready for install.


Have we seen a nosecone for SN20 with RCS? Have we seen the traditional RCS near the engine bay? So many pics it's hard to keep track.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: meekGee on 05/23/2021 05:16 pm
https://youtu.be/OmYXyQjxM_s

Owe - your videos are the best.
Just saying.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: baltrum on 05/23/2021 05:48 pm
Relaunch the SN15, test the recycled raptors, solve the fire issue on landing, which occurred on the SN10 as well, and fine-tune the landing to reach an exact point, much needed to use the capture system they propose to use.

Increasing the height to 20 km does not see much use, since the maximum fall speed is reached a few seconds from the free fall, which is like 450Km / h, which is not at all when it is orbital, where it will have to fall with an initial speed of 30,000 km / h...

It wouldn't be about speed, but atmospheric density (10 times lower) and control authority in those conditions during descent

I made this simple chart of Atmospheric Density in percent using data I found online (link here (http://www.braeunig.us/space/atmos.htm)).

Looking at this, it seems to me like higher hop test altitudes would significantly change the speed at which SN15 drops.
Note: Since the FAA has evaluated SS hops up to 30km (link here (https://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/launch/spacex_texas_launch_site_environmental_impact_statement/media/WR_for_Increased_Closure_Hours_508.pdf)), it seems likely this would be approved.

Yes, but not significantly higher, which would be something of the order of orbital speeds. What would be significantly different and untested is how to keep attitude control without atmosphere

It’s substantially easier to maintain attitude and attitude control without atmosphere. Current prototype  Starship is peppered with N2 jets fore and aft for exactly this purpose already; the fact that they can control attitude for the initial flip swan dive maneuver at lower altitude, despite the higher atmospheric density and upper-level winds, retires most or all of the basic risk there.

The RCS system has been untested so far

You’re very mistaken. Go back and watch the replays of all the test flights. Further, implementation on Starship is basic aerospace engineering and a (very) straightforward extension of the same exo-atmospheric ACS used very successfully for literally many dozens of F9 post-boost entries and landings.

The fact that you see this as a some big challenge that requires further testing makes additional conversation on the point moot.

Please, don't put words in my mouth. I never said it was a challenge, just that rather than a slightly higher velocity, a 20 km flight would allow testing attitude control, as others have just pointed out.
Title: Re: SpaceX Starship : Texas Prototype(s) Thread 20 : Discussion
Post by: Chris Bergin on 05/23/2021 06:36 pm
Time for a new thread me thinks!
Thread 21:
https://forum.nasaspaceflight.com/index.php?topic=53935.0