Author Topic: F9 Second Stage Reusability  (Read 137465 times)

Online AncientU

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Re: F9 Second Stage Reusability
« Reply #240 on: 04/08/2017 12:00 PM »
Wow.  Crazy news.  What a difference a week makes.
I will throw in my guess for S2 reuse.  Re-entry and descent will be handled by picaX on top, down one, a flap to protect the nozzle, and some grid fins for control.  "Landing" will be handled by a chopper catching the chute and returning it to land near the launch site.  I think legs, thrusters, tankage, and propellant will add too much dry mass.
Payload adaptors will sit on top of the dome heat shield, and will probably have to be jettisoned, but the CommX deployer might be able to be designed to fold back to the side opposite the PicaX to stay out of the re-entry plasma stream.
I think a non-reusable version will be available as well and will be such that it can be easily be converted to reusable and vise versa.
I think the changes can be light enough where it can work for both heavy and F9, LEO and GTO.
Raptor will eventually be used to up the payload capacity, but probably won't be ready for the first reused S2.

Not sure this is true.

SpaceX proposed to Air Force to build a Raptor prototype for F9/FH second stage... by end of 2018.  Despite protestations to the contrary* on this forum, maybe they intend to use the Raptor for exactly that. 
Stranger things have happened.

* Many based on the statement by EM that they won't build a reusable second stage...   ;) ;) ;)
« Last Edit: 04/08/2017 12:02 PM by AncientU »
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Online guckyfan

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Re: F9 Second Stage Reusability
« Reply #241 on: 04/08/2017 12:27 PM »
The Merlin main engine can not use all of the propellant. There is always an unusable residue left. How about SpaceX develops a small pressure fed kerolox engine for course adjustment and landing, maybe 2 or 3 are needed. They are not afraid of engine development. During the coasting phase they collect remaining propellant in 2 pressure tanks, separating any He bubbles and use that. Fully powered landing without any extra propellant, especially not hypergols.

I was taking a nap. During that time I had this idea. Tell me if it is completely off. I just don't believe in helicopter air recovery.

Offline envy887

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Re: F9 Second Stage Reusability
« Reply #242 on: 04/08/2017 12:36 PM »
The Merlin main engine can not use all of the propellant. There is always an unusable residue left. How about SpaceX develops a small pressure fed kerolox engine for course adjustment and landing, maybe 2 or 3 are needed. They are not afraid of engine development. During the coasting phase they collect remaining propellant in 2 pressure tanks, separating any He bubbles and use that. Fully powered landing without any extra propellant, especially not hypergols.

I was taking a nap. During that time I had this idea. Tell me if it is completely off. I just don't believe in helicopter air recovery.

SpaceX already has a small pressure fed kerolox engine with flight history... Kestrel. Without the vac nozzle it would have about 5 kN of thrust, perfect size for 2 or 3 of them to land the upper stage. And they weigh under 50 kg without the big nozzle

Online speedevil

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Re: F9 Second Stage Reusability
« Reply #243 on: 04/08/2017 12:42 PM »
The Merlin main engine can not use all of the propellant. There is always an unusable residue left.
The unusable residue claimed is startlingly small for F9 first stage reuse.
A couple of hundred kilos from memory, or ~1s of thrust time on merlin.

It seems unlikely that the second stage has substantially more dead volume.

I question if you can get meaningful pressure fed engines, a pump, tank to hold the propellant in the meantime, and ... in a weight at all comparable to the remaining fuel.

Online guckyfan

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Re: F9 Second Stage Reusability
« Reply #244 on: 04/08/2017 01:26 PM »
The Merlin main engine can not use all of the propellant. There is always an unusable residue left.
The unusable residue claimed is startlingly small for F9 first stage reuse.
A couple of hundred kilos from memory, or ~1s of thrust time on merlin.

It seems unlikely that the second stage has substantially more dead volume.

I question if you can get meaningful pressure fed engines, a pump, tank to hold the propellant in the meantime, and ... in a weight at all comparable to the remaining fuel.

From all the discussion I was under the impression that it would amount to maybe 1t for the upper stage. That would be enough to brake the slow terminal velocity. If it is really that low it would not be worth the effort.

Offline MikeAtkinson

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Re: F9 Second Stage Reusability
« Reply #245 on: 04/08/2017 02:05 PM »
The Merlin main engine can not use all of the propellant. There is always an unusable residue left. How about SpaceX develops a small pressure fed kerolox engine for course adjustment and landing, maybe 2 or 3 are needed. They are not afraid of engine development. During the coasting phase they collect remaining propellant in 2 pressure tanks, separating any He bubbles and use that. Fully powered landing without any extra propellant, especially not hypergols.

I was taking a nap. During that time I had this idea. Tell me if it is completely off. I just don't believe in helicopter air recovery.

This is what I think they will do for the ITS ship, but that has autogenous presurant, so scavenging that + left over liquid propellant is more important, then it can be stored in smaller tanks that are easier to insulate and cool.

My feeling is that scavenging propellant for the F9 second stage is only marginally worth it at best and is probably a net loss when considering the extra complexity involved.

Online GORDAP

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Re: F9 Second Stage Reusability
« Reply #246 on: 04/08/2017 03:26 PM »
Wow.  Crazy news.  What a difference a week makes.
I will throw in my guess for S2 reuse.  Re-entry and descent will be handled by picaX on top, down one, a flap to protect the nozzle, and some grid fins for control.  "Landing" will be handled by a chopper catching the chute and returning it to land near the launch site.  I think legs, thrusters, tankage, and propellant will add too much dry mass.
Payload adaptors will sit on top of the dome heat shield, and will probably have to be jettisoned, but the CommX deployer might be able to be designed to fold back to the side opposite the PicaX to stay out of the re-entry plasma stream.
I think a non-reusable version will be available as well and will be such that it can be easily be converted to reusable and vise versa.
I think the changes can be light enough where it can work for both heavy and F9, LEO and GTO.
Raptor will eventually be used to up the payload capacity, but probably won't be ready for the first reused S2.

Not sure this is true.

SpaceX proposed to Air Force to build a Raptor prototype for F9/FH second stage... by end of 2018.  Despite protestations to the contrary* on this forum, maybe they intend to use the Raptor for exactly that. 
Stranger things have happened.

* Many based on the statement by EM that they won't build a reusable second stage...   ;) ;) ;)


I suspect you may be right. 

Back when EM threw cold water on a reusable 2nd stage, he said (a) it would take time away from designing the ITS and (b) a higher ISP stage was needed to make up for the added 'reuse' mass.

It may be that he's changed his mind on (a) (perhaps realizing that he needs higher profits from CommX to get to ITS) but the math probably didn't change on (b).  If so, that means a Raptor reusable US sooner rather than later.

I'm wondering then if SpaceX will use the FH on the demo flight, plus a few others, to test out some technologies as 'bolt ons' to the existing US.  Things like TPS, grid fins and a parachute.  Then snag it with a helicopter and/or lay it on a bouncy castle.  All with no intention to actually incorporate these features onto the Merlin US (or indeed to ever reuse that stage), but rather to gather data for the design of the Raptor US.

Then the Raptor US will forgo the parachute, helicopter and bouncy castle in favor of propulsive landing and legs, in line with SpaceX's original vision.

Offline Robotbeat

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Re: F9 Second Stage Reusability
« Reply #247 on: 04/08/2017 03:50 PM »
Elon Musk saying reusable upper stage too heavy without Raptor or whatever was referring to the 2-stage Falcon 9 and to GTO. Same logic doesn't apply to Falcon Heavy or to LEO, and definitely not both together.
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Online GORDAP

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Re: F9 Second Stage Reusability
« Reply #248 on: 04/08/2017 04:59 PM »
Elon Musk saying reusable upper stage too heavy without Raptor or whatever was referring to the 2-stage Falcon 9 and to GTO. Same logic doesn't apply to Falcon Heavy or to LEO, and definitely not both together.

Robo, I don't think that's right.  At Elon's talk at MIT in '14, he said "I don't expect the Falcon line (emphasis mine) to have a reusable upper stage, just because the...with a kerosene based system the specific impulse isn't really high enough to do that."  And he says the later system will be fully reusable.  But he clarifies what he means by specifying that the 'later' system is Methane based.  So he's clearly talking about ITS/Raptor.  So by 'Falcon line' he's clearly talking about both F9 and FH.

Do you have a source where he indicates or hints that re-usability might be possible with a Merlin base US for the FH?

Online guckyfan

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Re: F9 Second Stage Reusability
« Reply #249 on: 04/08/2017 05:09 PM »
I am sure at one point he said FH has enough lift to make the second stage reusable but they want instead to concentrate on the Mars vehicle.

With the present increased capabilities F9 to LEO is also quite feasible with a reusable upper stage and they will have plenty of launches through the satellite constellation.

There is no indication that they are planning the reusable upper stage to be methane/raptor.

Offline adrianwyard

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Re: F9 Second Stage Reusability
« Reply #250 on: 04/08/2017 05:35 PM »
What makes this so fascinating is Musk saying they may try to bring the FH demo S2 back this summer! No-one expected that. Presumably that rules out anything but the simplest modifications. And definitely not a Raptor.

My guess is this is simply data gathering, and not a prototype reusable stage. Similar to trying to return the Falcon 1 on parachutes, or 'landing' F9 S1 at sea; why not give it a go? Perhaps simply a propulsive entry and inevitable destruction: the capacity of FH lobs an S2 into LEO leaving it with an unprecedented quantity of propellant. Absent a heat shield, once it nears the atmosphere, it lights the MVac and keep it pointed into the airstream until it runs out of fuel. See how low you get. Then splash.

The only thing this really achieves is more supersonic retropulsion time. But Earth's atmosphere at ~130,000 ft is about as dense as Mars so maybe that's sufficiently interesting?

But for S2 reusability it seems less helpful. As others have pointed out firing rockets in the direction of travel is probably not the best idea for Earth entry as it actually makes the craft more streamlined. Blunt heat shields are likely more efficient at braking pound-for-pound. Plus the MVac plumbing is not protected from the heat of entry so who knows how long that would last. It's all quite mysterious.

Offline meekGee

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Re: F9 Second Stage Reusability
« Reply #251 on: 04/08/2017 07:32 PM »
Elon Musk saying reusable upper stage too heavy without Raptor or whatever was referring to the 2-stage Falcon 9 and to GTO. Same logic doesn't apply to Falcon Heavy or to LEO, and definitely not both together.

Robo, I don't think that's right.  At Elon's talk at MIT in '14, he said "I don't expect the Falcon line (emphasis mine) to have a reusable upper stage, just because the...with a kerosene based system the specific impulse isn't really high enough to do that."  And he says the later system will be fully reusable.  But he clarifies what he means by specifying that the 'later' system is Methane based.  So he's clearly talking about ITS/Raptor.  So by 'Falcon line' he's clearly talking about both F9 and FH.

Do you have a source where he indicates or hints that re-usability might be possible with a Merlin base US for the FH?

It's not just the interpretation of what "line" means.

It's the basic numbers.

The second stage weighs 5 tons, empty.  Payload is 22 tons expendable, let's call it 15 tons reusable RTLS. (though straight through down-range barge recovery has less penalty, so somewhere in between)

There is little doubt that you can return the second stage with a "huge" penalty of, say, 100%.  (Highly conservative, I'd say the correct number is 50%)

So now the second stage weighs up  to 10 tons, empty, and payload is reduced to ~10 tons worst case.

Except that this was the payload 2 iterations ago, and everyone thought it's fine...

The only question is - is this good enough?

I think if you achieve rapid turn-around and >10 flights per core, it becomes a no-brainer, even if you go from 2 launches per orbital plane to 3.

(I don't think the constellation will use FH, since barge turn-around times are too long)
« Last Edit: 04/08/2017 09:02 PM by meekGee »
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Online AncientU

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Re: F9 Second Stage Reusability
« Reply #252 on: 04/08/2017 09:01 PM »
What makes this so fascinating is Musk saying they may try to bring the FH demo S2 back this summer! No-one expected that. Presumably that rules out anything but the simplest modifications. And definitely not a Raptor.

...

This line of reasoning is flawed; you are assuming that EM didn't decide to bring back the second stage until that event 1-2 weeks ago.  Us not knowing about his plan (and it is likely much more mature than he is letting on) doesn't have any bearing on him having a plan. 

His time constraints as you've outlined them don't exist... FH has been on drawing boards without a paying customer for years.  IIRC, five years ago, he asked -- if you could launch anything into space, what would it be -- he was referring to the FH demo launch.  The 'silly' payload and the hardware to return the second stage was probably ready last year when AMOS disrupted all plans.
« Last Edit: 04/08/2017 09:02 PM by AncientU »
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Offline adrianwyard

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Re: F9 Second Stage Reusability
« Reply #253 on: 04/08/2017 10:00 PM »
I'd be happy to be proven wrong. I think most of us took Elon at his word when he said plans to re-use Falcon S2 were on hold. And the experts believed him because it's very, very hard to pull off.

SpaceX typically hint at progress on projects years before flight, so if a reusable S2 is ready to test soon this will have involved uncharacteristic secrecy. Hopefully more will be revealed soon.

Offline The Amazing Catstronaut

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Re: F9 Second Stage Reusability
« Reply #254 on: 04/08/2017 10:35 PM »
Reusable upper stage work is essentially subscale ITS spaceship testing.

Do you mean 'essentially the role a subscale ITS would have', or 'testing for a subscale ITS'?

Because I would love to knock this conjecture-darling subscale ITS concept on its head since it seems to be coming out the woodwork without any proof other than that the idea is popular. People bring it up all the time like it's anything more than some concept we dreamed up on Nasaspaceflight without any bearing on any info that has come out of SpaceX. It's a fiction rocket. It's like falcon 5 to me - irrelevant; a stop-gap which doesn't fulfil the endgoal and only has a reason for creation because of worries the endgoal might be too challenging.

Reusable stage 2 on F9 -massively reduces- the need for subscale ITS from my perception.

That's not how SpaceX approaches problem resolution. They don't half-arse it because they think they need a tech demo, they go big, then iterate.
« Last Edit: 04/08/2017 10:37 PM by The Amazing Catstronaut »
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Offline Space Ghost 1962

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Re: F9 Second Stage Reusability
« Reply #255 on: 04/08/2017 11:03 PM »
The point of the FH Demo mission is for the AF to see a "stock" FH in action. No configuration changes allowed for three flights.

They will not have any major changes.

And perhaps you don't need any major things to make this work. That it has been overthought too much.

Perhaps the answer is in subtlety. Where both this board and aerospace in general often fail miserably.

BTW, many of the aspects of Centaur that I enjoyed understanding for decades ... are subtle ones ... FWIW.

Online AncientU

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Re: F9 Second Stage Reusability
« Reply #256 on: 04/08/2017 11:26 PM »
Reusable upper stage work is essentially subscale ITS spaceship testing.

Do you mean 'essentially the role a subscale ITS would have', or 'testing for a subscale ITS'?

Because I would love to knock this conjecture-darling subscale ITS concept on its head since it seems to be coming out the woodwork without any proof other than that the idea is popular. People bring it up all the time like it's anything more than some concept we dreamed up on Nasaspaceflight without any bearing on any info that has come out of SpaceX. It's a fiction rocket. It's like falcon 5 to me - irrelevant; a stop-gap which doesn't fulfil the endgoal and only has a reason for creation because of worries the endgoal might be too challenging.

Reusable stage 2 on F9 -massively reduces- the need for subscale ITS from my perception.

That's not how SpaceX approaches problem resolution. They don't half-arse it because they think they need a tech demo, they go big, then iterate.

The track record proves otherwise...

When proving all the pieces of the booster reuse strategy, they totally used tech demos (e.g., Grasshopper, F9 v1.1, ..., soft landing on the ocean, ...).  Going big then iterating would have been to launch the first F9 booster toward a fully kitted out (like they are today) ASDS, then iterate (after repairs). (Kinda like what people think JB will do with NG. He won't.)  Dragon 2 had Dragon 1, launch abort using a tech demo Dragon 1, tether testing SuperDraco hovering, and tech demos still in progress...  They'll land a few cargo Dragon 2s on land before crewed land landings.

When EM discussed the 'updated strategy' making 'a lot more sense' -- at the same presser that he used to reveal the second stage 'Hail Mary' -- it was game-on for speculating what the more sensible strategy involved.

Quote
Robin... Robinson Manuel, with the New York Observer, Could you give us an update on the development of the Interplanetary Transport System, and what's next in terms of - what's the next component to be tested following the carbon fuel tank and the Raptor engine, what's next?

E: So, I think we'll provide an update on the design of the Interplanetary Transport System - Interplanetary Transport System also includes the propellant depot on Mars - that's why it's sort of - I actually usually don't like the word 'system', but we can't call it a rocket if it includes a propellant depot. So the Mars planetary transporter or Mars Transporter, or Interplanetary Transporter - We've come up with a number of design refinements, and I think we'll probably be ready to put that on the Website within a month or so.

RM: Just one follow-up, The time frame has kind of shifted since Guadalajara, I was wondering if if you guys had any updated time frame of when you think that first mission will be launched - If I'm correct, the first one is uncrewed, correct?

E: Yeah the first ones will be uncrewed. I don't want to steal thunder from that announcement. I'm pretty excited about the updated strategy since Guadalajara, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt.
https://www.reddit.com/r/spacex/comments/62i6m1/recap_of_the_elon_musk_and_martin_halliwell_press/dfmw95b/

Good news: We'll know more 'within a month or so'
Bad News: EM time
« Last Edit: 04/08/2017 11:36 PM by AncientU »
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Offline meekGee

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Re: F9 Second Stage Reusability
« Reply #257 on: 04/08/2017 11:31 PM »
I'd be happy to be proven wrong. I think most of us took Elon at his word when he said plans to re-use Falcon S2 were on hold. And the experts believed him because it's very, very hard to pull off.

SpaceX typically hint at progress on projects years before flight, so if a reusable S2 is ready to test soon this will have involved uncharacteristic secrecy. Hopefully more will be revealed soon.

I think that's a common misconception.

S1 reuse is much harder.

S2 reuse is not hard - it is similar to Dragon re-entry and reuse.  It's just that it imposes a certain penalty that was considered prohibitive.

So it's a matter of economics, and with higher S1 performance, it has become non-prohibitive.

Consider what S1 reuse entails:  Re-entry with a very awkward and fragile vehicle, with no real heat shield, doing everything propulsively, and coming to a soft landing on a tiny target.

S2 on the other hand can use a real heat-shield, Dragon style.  No need for propulsive landing since the empty mass is small, and the stage can come down right off-shore, where it's a lot easier to operate a helicopter.  Or, for what it's worth - bouncy castles and all that.  Once past re-entry, it's easier than catching a fairing.
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Offline adrianwyard

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Re: F9 Second Stage Reusability
« Reply #258 on: 04/09/2017 01:00 AM »
Returning S2 will be 'similar to Dragon' in that it comes in from orbital velocity and will involve the use of Pica-X heat-shield material, but there are also many differences. The shape and mass characteristics are totally different.

Are you thinking S2 comes down nose first ~vertically? The stock S2 is tail (engine) heavy but I suppose a big parafoil stored in the nose will weigh something, perhaps enough to make it fly nose first. Would it be a lifting-entry a la Dragon for steering?

Or... the ITS fans would be happy if it had TPS on the side and it came in ITS/shuttle-style! But then you'd need a flap or something to protect the MVac - as recent posts have suggested.

Looks like guesstimate of S2 dry mass is <5mT before re-use hardware is added. At what mass does helicopter capture become too hairy, I wonder.

Edit to add:

A couple of years ago I threw out the possibility of landing something S2-like (ESA's IXV) at very high speed on a runway. FWIW: http://forum.nasaspaceflight.com/index.php?topic=36856.msg1335557#msg1335557
« Last Edit: 04/09/2017 01:05 AM by adrianwyard »

Offline Robotbeat

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Re: F9 Second Stage Reusability
« Reply #259 on: 04/09/2017 01:23 AM »
Reusable upper stage work is essentially subscale ITS spaceship testing.

Do you mean 'essentially the role a subscale ITS would have', or 'testing for a subscale ITS'?

Because I would love to knock this conjecture-darling subscale ITS concept on its head since it seems to be coming out the woodwork without any proof other than that the idea is popular. People bring it up all the time like it's anything more than some concept we dreamed up on Nasaspaceflight without any bearing on any info that has come out of SpaceX. It's a fiction rocket. It's like falcon 5 to me - irrelevant; a stop-gap which doesn't fulfil the endgoal and only has a reason for creation because of worries the endgoal might be too challenging.

Reusable stage 2 on F9 -massively reduces- the need for subscale ITS from my perception.

That's not how SpaceX approaches problem resolution. They don't half-arse it because they think they need a tech demo, they go big, then iterate.

The track record proves otherwise...

When proving all the pieces of the booster reuse strategy, they totally used tech demos (e.g., Grasshopper, F9 v1.1, ..., soft landing on the ocean, ...).  Going big then iterating would have been to launch the first F9 booster toward a fully kitted out (like they are today) ASDS, then iterate (after repairs). (Kinda like what people think JB will do with NG. He won't.)  Dragon 2 had Dragon 1, launch abort using a tech demo Dragon 1, tether testing SuperDraco hovering, and tech demos still in progress...  They'll land a few cargo Dragon 2s on land before crewed land landings.

When EM discussed the 'updated strategy' making 'a lot more sense' -- at the same presser that he used to reveal the second stage 'Hail Mary' -- it was game-on for speculating what the more sensible strategy involved.

Quote
Robin... Robinson Manuel, with the New York Observer, Could you give us an update on the development of the Interplanetary Transport System, and what's next in terms of - what's the next component to be tested following the carbon fuel tank and the Raptor engine, what's next?

E: So, I think we'll provide an update on the design of the Interplanetary Transport System - Interplanetary Transport System also includes the propellant depot on Mars - that's why it's sort of - I actually usually don't like the word 'system', but we can't call it a rocket if it includes a propellant depot. So the Mars planetary transporter or Mars Transporter, or Interplanetary Transporter - We've come up with a number of design refinements, and I think we'll probably be ready to put that on the Website within a month or so.

RM: Just one follow-up, The time frame has kind of shifted since Guadalajara, I was wondering if if you guys had any updated time frame of when you think that first mission will be launched - If I'm correct, the first one is uncrewed, correct?

E: Yeah the first ones will be uncrewed. I don't want to steal thunder from that announcement. I'm pretty excited about the updated strategy since Guadalajara, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt.
https://www.reddit.com/r/spacex/comments/62i6m1/recap_of_the_elon_musk_and_martin_halliwell_press/dfmw95b/

Good news: We'll know more 'within a month or so'
Bad News: EM time
Hmmm....

Very interesting quotes. Makes me think there's going to be less "steal underpants then ???" and more of a straightforward development plan.

Possible plan:
1) Reusable upper stage demo on FH. Could just test ITS-like side reentry with body flaps, followed by parachute and splashdown (ala Dragon) or it could mean a full simulation of ITS using propulsive landing with Superdracos (ala the old reuse video) plus the previously mentioned body flaps. Or it could even mean a Raptor-based upper stage* as an even closer analogue to ITS, but I doubt that. In any case, they get experience with the rest of the hard parts of ITS before fabricating it and needing a big launch site.

2) They could even use this upper stage reuse concept operationally on flights they have a lot of margin on.

3) F9 testing of the launch cradle idea on paid flights.

4) Develop a smaller version of ITS (could still be Saturn V level of thrust!) that's still at least big enough to put Falcon Heavy out of a job. This can take over constellation work with full and rapid reuse. It could also be designed with room to barrel-stretch and upgrade to the full envisioned ITS over time. Once this works, they can retire Falcon Heavy and move any customers that signed up for Falcon Heavy over to this new, cheaper-to-operate rocket (just like they moved people who signed up for F1, F5 and the early F9 to the new F9 v1.1 and full thrust). By being lower thrust, it's much easier to convince folks to let them launch it from LC-39A and/or Brownsville. It also would be significantly cheaper up-front, partly because they could operate with fewer Raptors (9 to 20?) and also because Raptor could be lower thrust as well, which reduces its development risk a LOT.

At every step, they can reduce risk and pay for development using their existing business or the constellation's business, not requiring a big $10B bolus of money. It also directly enhances their competitiveness at every step, making it harder for upstart competitors (like New Glenn) to steal away marketshare. It also may be faster if they don't need a totally new launch site (as might be required if they pushed for full-thrust ITS right away). And by developing upper stage reuse earlier, they can get relevant reentry experience faster as well, which might help them avoid some really expensive mistakes once they bite the bullet on the (possibly smallish) initial ITS. They can also do so primarily by being funded by paying payloads, just like they did for first stage reuse.

And I don't think they'd lose anything by first pursuing a smaller ITS. Every SpaceX rocket has significantly improved its performance over time. F9 v1.0 block I (which we have only little information on, since their first User's Guide was for F9 v1.0 block II, which never flew) got about 8-10 tons of payload to LEO. F9 full thrust block 5 is 22.8t, about 2.5x as much payload plus twice as much thrust even with the same number of engines.


*Optionally, they could develop a Raptor-based upper stage for F9 and Falcon Heavy as an intermediate step before the smallish ITS version, though I don't know if that's required. If they do develop it, they can test refueling and perhaps even Mars landing and early crewed missions this way. But I doubt this is the plan.
« Last Edit: 04/09/2017 01:32 AM 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

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