Author Topic: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion  (Read 492506 times)

Offline AstroWare

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1120 on: 01/30/2021 04:44 pm »
Are those heat shield tiles on the inside of the flap?

Welcome to the forum - Moving discussion to the Discussion thread.

If those are heat shield tiles, I wonder why they'd be on the top surface of the flaps?  I understand why they'd be on the other side (where they will face the wind on descent).  Maybe they expect or know that the airflow will wrap around to the top of the flaps, and so need heat tiles there, too?

Maybe, I thought it was weird though. Here's the picture again for this forum.
Maybe they wanted to test the attachment method to the flaps, and see how well they withstand the launch enviorment - but didnt want to disrupt the airflow. When the whole flap is covered it's fine, but a patch of test tiles may affect the airflow over the flap.

Offline Slarty1080

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1121 on: 01/30/2021 04:51 pm »
After reading incognito here for 1/4 year, this is my first question.  If already dealt with, please post a link, I haven't been able to find the answer yet.  Without Super Heavy, what would be the maximum height Starship could reach when taking off from Earth?

I don't think height is the question, it's more speed that would be the concern. You could send a rocket on a ballistic trajectory way above the orbital height of the ISS while still being far too slow to make orbit.

In terms of the performance of single-stage Starship, I guess it'd depend on the flight trajectory and time spend in atmosphere, but someone could probably crunch some basic numbers about the sort of velocity that it could get up to burning X amount of fuel with the current rSea specific impulse stats.

Edit: Can we go back to rocket discussion and have less spin re: Musk vs the FAA? Should only be relevant with respect to the impact on testing and timelines, speculation about agendas and politics is neither here nor there.

I'm here for the work done by SpaceX's engineers, and the less focus on Musk and the culture of cult personality around him the better, please.

Single-Stage Starship with no payload gets somewhere in the region of 7000+ m/s of dV, and requires 6 SL Raptors (or those VacRaps being tested at McGregor that can fire at SL) to have sufficient thrust to lift off the pad. Exact numbers depend on the dry weight quite significantly as well as the orbit achieved, but doesn't account for gravity and air resistance losses. Elon has tweeted (in 2019) that a stripped-down Starship could make it to orbit, but what's the point if it can't do anything once there?
I think that uhrflieger (like me) was just interested to know out of idle curiosity the following: If (say) SN10 with 3 engines were to be loaded with as much propellant as possible, whilst still allowing an acceptable thrust to weight ratio for launch, and if it's powered trajectory were to be entirely perpendicular to Earths surface, how high would it go before it stopped and started to fall back to Earth? Me thinks several thousand miles, but that's just a guess based on Elon's statement that if they hadn't carefully throttled the raptors that SN8 would have gone "crazy high" and it wasn't even fully tanked.
Then the Kármán line would be easy to manage.  Perhaps an inexpensive alternative to New Shepard - competition is good for business!  I'm starting to save ...
Yes Karman line should be easy. I decided to do the calculation as best I could myself using this source:
https://en.wikiversity.org/wiki/PlanetPhysics/Single_Stage_Rocket_Burnout_Height
and reasonable assumptions from wikipedia and this site re Raptor
result max altitude = 631km without taking into account aerodynamic drag so I will revise my statement to hundreds of miles up. There are too many variables to be much more exact than that.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline Spindog

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1122 on: 01/30/2021 04:54 pm »
The impact of an SN8 rules violation is likely in effect what Elon is complaining about. Its not possible to be flexible and fast while filing precise flight test profiles months in advance with the FAA. This is especially true when you have dynamic flight software that can change the profile as needed based in actual performance.

Its easy to see that you can't properly file a flight profile until you see what happened in the previous test. And when you're trying to test fly every week or two or even faster there's no way this entire process can work. FAA needs to give them blanket permission to fly within a large and flexible range as long as they implement reasonable FTS and area clearing procedures.
« Last Edit: 01/30/2021 05:05 pm by Spindog »

Offline TRS717

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1123 on: 01/30/2021 05:08 pm »
https://www.reuters.com/article/us-space-exploration-starship/musks-spacex-violated-its-launch-license-in-explosive-starship-test-the-verge-idUSKBN29Z06R
For all the speculation about possible FTS issues, I can't help but wonder if the landing attempt itself violated the license, and if perhaps the FAA was led to believe that SN8's flight would conclude, as did early Falcon 9 flights, with simulated landing maneuvers and burns, out over the water?
« Last Edit: 01/30/2021 05:10 pm by TRS717 »

Offline Rocket Science

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1124 on: 01/30/2021 05:16 pm »
Even Model Rocketry is subject to tight regulations. You can't just do what you want in the airspace...
https://www.faa.gov/air_traffic/publications/atpubs/pham_html/chap31_section_2.html
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline RedLineTrain

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1125 on: 01/30/2021 05:29 pm »
I was as eager as the next person to see that baby fly.  One thing disturbed me:  Elon's rant against the FAA.  The aircraft section of the agency was good by the spacecraft section wasn't.  Isn't the aircraft section the group that routinely rubber stamps Boeing's decisions, such as the MAX, without legitimate oversight?  That's the kind of oversight Elon would like to see.  However, with the MAX, we see the danger of an abdication from governmental oversight responsibility.  No one, not even Elon, is infallible.  It might not be a bad idea to have bureaucrats who aren't afraid to say no conducting the oversight, even if they might be a tad bit overcautious.  Look what happened to Boeing when the FAA subserviently removed the stop signs.  A few days or even weeks delay won't matter in the long run.  Patience.
Not getting into the politics of it, but whilst a few days or weeks for SN9 won't matter a few days or weeks for every SN from here on out will add up to a tremendous delay.
Musk's "rant" was aimed at the FAA rule system and not the FAA or safety and was hardly that controversial given that even the FAA acknowledge that its rules are in need of update (and is in the process of updating them, due to be in force on 10th March IIRC).

Yes, Musk is putting in a marker for rule changes in the new administration.  They have new rules being implemented in February (assuming the new administration didn't put them on hold pending a review) and Musk is trying to influence that or subsequent rules in some fashion.

It's important to keep in mind that by law the FAA is tasked with encouraging commercial space launch. Right now, a big chunk of that is helping SpaceX test Starship prototypes safely.  They are required to be helpful, no matter what is tweeted.
« Last Edit: 01/30/2021 05:30 pm by RedLineTrain »

Offline AC in NC

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1126 on: 01/30/2021 05:30 pm »
https://www.reuters.com/article/us-space-exploration-starship/musks-spacex-violated-its-launch-license-in-explosive-starship-test-the-verge-idUSKBN29Z06R
For all the speculation about possible FTS issues, I can't help but wonder if the landing attempt itself violated the license, and if perhaps the FAA was led to believe that SN8's flight would conclude, as did early Falcon 9 flights, with simulated landing maneuvers and burns, out over the water?

It would be unimaginable to me that landing details wouldn't be part of the paperwork.  The issued TFR's language about "launch and recovery" strongly implies they understand.


Online Robotbeat

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1127 on: 01/30/2021 05:34 pm »
Yeah, the Verge article claims a violation occurred but provided ZERO detail.

For all we know, the Verge heard incorrectly.

https://twitter.com/joroulette/status/1355289694888718347
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Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1128 on: 01/30/2021 05:34 pm »
The FAA takes the procedural view: "you said you'd activate FTS on engine failure and you didn't, so how can we trust you to do what you say in future?"

Based on a lot of personal experience with the FAA in the past, this would not surprise me one bit.  They have a "the Rules are the Rules" attitude and they will absolutely priortize the letter of the law over the spirit and intent, even when it goes into absurd levels.  See my prior comment; "we agree it doesn't make sense... but we're not going to change it"
...except there's nothing to indicate that FTS has to activate on engine failure..   It activates based on IIP of the whole vehicle leaving some prescribed zone.

If the vehicle is close to landing and moving towards the landing zone, why would anyone activate an FTS?

Engine failure as a criterion doesn't make sense since it can be a partial failure (like we saw)  and maybe a transient one..  if there's no danger, why set up an FTS activation rule for that?
The actual criteria is the rate and direction the IIP is moving such that is it rapidly approaching the edge of allowable. This is the actual criteria that Range Safety Officers use to make their decisions as to be quick and "blow it" or to ride it and watch closely as it slowly moves along but not toward the edge. The IIP area is a prior to flight analysis about explosive fragments and their inclusive footprint with considerations for all possible wind speeds, directions and altitude at time of explosion. Maybe the FAA discovered they screwed up the previous analysis and are still in the process of validating the new analysis. In which case the SN8 licence was itself what was in violation not what the SN8 actual flight did.

There is also another item here and that is the FAA's workload. 2021 can likely be from 50% to 100% more launches and licences than 2020 which was also an increase from 2019 itself. The FAA is face for this year as much as 2X the work and hardly any extra funds for more assets to do the work. Expect other launches to possibly suffer launch delays during the year as well for launch licenses just not approved because of the FAA staff not having the analysis finished yet.

A NOTE is that SpaceX gives the FAA an analysis report and proposed IIP plot based on proposed flight path.  With which the FAA does the analysis to determine if the analysis report for FTS criteria is sufficient or not. Also note is that SpaceX is likely to be more conservative than even the FAA because they, SpaceX are the ones liable for damages etc.
When you talk, I listen. It seems to pay off.


Do you know how the launch license is funded? Are there fees and are they enough to fund the process? If not, it would literally take an act of Congress to change it. 
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

Offline Rocket Science

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1129 on: 01/30/2021 05:37 pm »
Some advice from this "old pilot", you don't want to piss-off the FAA...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Online Robotbeat

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1130 on: 01/30/2021 05:41 pm »
I want confirmation of what the Verge is claiming. Way too vague of an accusation. And nothing seems out of order from what we can tell. 
https://twitter.com/joroulette/status/1355289694888718347
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline DigitalMan

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1131 on: 01/30/2021 05:43 pm »
Do you know how the launch license is funded? Are there fees and are they enough to fund the process? If not, it would literally take an act of Congress to change it. 

The FAA has a trust fund that finances its operations (I think there is a change to that because of Covid) it is logical that launch licenses fit into the hierarchy somewhere.

The trust fund comes from fees the FAA charges.
« Last Edit: 01/30/2021 05:44 pm by DigitalMan »

Online Robotbeat

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1132 on: 01/30/2021 05:48 pm »
This is third hand information, by the way. The “2 people familiar with the incident” are not named, but it’s implied they aren’t actually the FAA.

For all we know it’s someone with an ax to grind that is putting their own spin on the FAA investigation of the explosion. Since ZERO details are given, we should take the whole thing with a massive grain of salt.

So the FAA is having an investigation, those 2 people “familiar” with the incident got wind of it, and alerted Joey at the Verge but provided zero details.

I’d consider this an accusation, not a certainty that SpaceX violated the terms until the FAA actually makes clear.
« Last Edit: 01/30/2021 05:50 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline DigitalMan

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1133 on: 01/30/2021 05:55 pm »
Here's the more likely scenario and others have reported on this prevoiusly:

SN8 swapped an engine before launch and they didn't go through an FAA review. FAA considered that a violation and threw the book at them even though the engine was identical.

It's possible. I give it a low probability due to there being a 21 day gap between engine swap and TFR issuance. Plenty of time to file paperwork.

Offline zubenelgenubi

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Re: SpaceX Starship : Texas Prototype(s) Thread 16 : Discussion
« Reply #1134 on: 01/30/2021 06:42 pm »
Moderator:
We performed thread trims in this thread this morning EST.

Multiple moderators have done so in recent days.

Several moderator warnings have been posted in thread.

I know that the Elon vs. FAA story is quite exciting.  However, that does not excuse members from the NSF forum rules of the road.

I am locking the thread for a time period TBD. I am also performing yet another thread trim.

Do not use other, off-topic threads to continue arguments from here.

Thank you.
« Last Edit: 01/30/2021 06:54 pm by Chris Bergin »
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Actually, I'll start a new thread, we're due one. The problem is the hot mess (it really is) of the Verge's attempt to get a slice of the clickbait action. And a lot of you are proving the value in that by clicking on it, discussing it and linking it everywhere.

I'd suggest not referencing that if we want to have an accurate conversation here.

New thread link:
https://forum.nasaspaceflight.com/index.php?topic=52940.0
« Last Edit: 01/30/2021 07:01 pm by Chris Bergin »
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