Author Topic: F9 Second Stage Reusability  (Read 99408 times)

Offline mme

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Re: F9 Second Stage Reusability
« Reply #220 on: 04/07/2017 11:57 PM »
Elon's latest on twitter:
Quote
Fairing is ~$5M, but that should be reusable this year. Am fairly confident we can reuse upper stage too by late next year to get to 100%.

I'm floored.
1) Does this mean that the Block 5 design freeze slated for this year is NOT a design freeze?
2) What are the implications for NASA and the AF who want one design "Block 5" certified and flown again and again?
3) What is the implication for ITS schedule if finite # of SpaceX engineers are working on fairing and S2 re-usability and not ITS through "late next year" at least?
4) Obviously unknown but the S2 mechanisms for recovery and payload penalty will be "interesting".
I'm still a fan of the "reusability option" (if it could be made to work).  Bolts on top of a standard-ish S2 for head first reentry.

No idea if it can be made to work.
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Online AncientU

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Re: F9 Second Stage Reusability
« Reply #221 on: 04/07/2017 11:58 PM »
Am I the only one who thinks this may be bad news? Seems they scale down work on ITS and have more time to work on reusable S2. They may have to do that and scale up ITS again when money comes in from the satellite constellation.

Edit: Or the positive view. They have come to the conclusion that reuse is so easy and cheap that they can fly FH a lot and so can afford the payload loss through second stage reuse.
I think it's more likely that more work was already done on S2 than elon was aware of last week.

"Alright team, we've got Stage 1 ironed out, and it looks like fairings are well on their way with just some debugging. That leaves stage 2. We didnt design stage 2 for recovery, but lets hear some proposals."

"Sir, here's a detailed proposal I worked up in my free time, and a 1 page summary why my approach is better than the others."

I would think assuming Elon was somehow "unaware" of the state of stage 2 recovery work is a very bad assumption. Just because he hasn't talked about it publicly does not mean it was 1. abandoned or 2. he is not apprised of what his company is spending money and manpower on. It appears they always have many irons in the fire simultaneously and only choose to use them when the time is right.

The most viable approach to second stage reuse should include the following elements:
1. Don't bother on GTO launches with F9 (you are already making a bundle on these flights)
2. Don't bother on USG 'certified' flights (ditto)
3. Be very worried about the cost of lofting a 12,000 sat constellation (this is an out-of-pocket Capex)
4. Think globally about 'second stage' which traditionally was booster + fairing + adaptor/dispenser, and find solution that gets the job done and returns everything in rapid reusable mode
5. Use whatever propulsion and configuration needed to get the job done (don't be constrained by 6 year old animations)
6. Don't tell anyone what you are up to because it is for a heavily contested market
7. Don't dare touch the Block 5 core (Hands-off... this means you, Elon! --GS)
« Last Edit: 04/08/2017 12:01 AM by AncientU »
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Offline meekGee

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Re: F9 Second Stage Reusability
« Reply #222 on: 04/08/2017 12:18 AM »
Am I the only one who thinks this may be bad news? Seems they scale down work on ITS and have more time to work on reusable S2. They may have to do that and scale up ITS again when money comes in from the satellite constellation.

Edit: Or the positive view. They have come to the conclusion that reuse is so easy and cheap that they can fly FH a lot and so can afford the payload loss through second stage reuse.
I think it's more likely that more work was already done on S2 than elon was aware of last week.

"Alright team, we've got Stage 1 ironed out, and it looks like fairings are well on their way with just some debugging. That leaves stage 2. We didnt design stage 2 for recovery, but lets hear some proposals."

"Sir, here's a detailed proposal I worked up in my free time, and a 1 page summary why my approach is better than the others."

I would think assuming Elon was somehow "unaware" of the state of stage 2 recovery work is a very bad assumption. Just because he hasn't talked about it publicly does not mean it was 1. abandoned or 2. he is not apprised of what his company is spending money and manpower on. It appears they always have many irons in the fire simultaneously and only choose to use them when the time is right.
Exactly.

There was simply never any way that a company that is contemplating several LEO launches per week won't reuse S2.

It was true with the LEO constellation, and twice as true now with the vLEO one.
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Online AncientU

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Re: F9 Second Stage Reusability
« Reply #223 on: 04/08/2017 12:29 AM »
Am I the only one who thinks this may be bad news? Seems they scale down work on ITS and have more time to work on reusable S2. They may have to do that and scale up ITS again when money comes in from the satellite constellation.

Edit: Or the positive view. They have come to the conclusion that reuse is so easy and cheap that they can fly FH a lot and so can afford the payload loss through second stage reuse.

How is flying an orbital vehicle (not an inherently stable capsule) through the atmosphere and landing not still working on ITS?  This is probably the second toughest technical challenge.  (making sufficient fuel on Mars is the toughest by far)
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Offline meekGee

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Re: F9 Second Stage Reusability
« Reply #224 on: 04/08/2017 01:51 AM »
Am I the only one who thinks this may be bad news? Seems they scale down work on ITS and have more time to work on reusable S2. They may have to do that and scale up ITS again when money comes in from the satellite constellation.

Edit: Or the positive view. They have come to the conclusion that reuse is so easy and cheap that they can fly FH a lot and so can afford the payload loss through second stage reuse.

... and, there isn't a single person in the world who wasn't floored by ITS's schedule.

But the road to Mars appears go to through the constellation, and the constellation is much more viable with a reusable second stage, so I think it's ok.

And I'm also sure that work on ITS is nowhere near stopped.  Just maybe slowed down a bit since some people will also be engaged on S2 recovery.

Meanwhile S2 recovery is not holding up day-to-day launches, so it's not a "critical" item that stops all other work.

In other words, it's all good.
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Offline rakaydos

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Re: F9 Second Stage Reusability
« Reply #225 on: 04/08/2017 01:55 AM »
Am I the only one who thinks this may be bad news? Seems they scale down work on ITS and have more time to work on reusable S2. They may have to do that and scale up ITS again when money comes in from the satellite constellation.

Edit: Or the positive view. They have come to the conclusion that reuse is so easy and cheap that they can fly FH a lot and so can afford the payload loss through second stage reuse.
I think it's more likely that more work was already done on S2 than elon was aware of last week.

"Alright team, we've got Stage 1 ironed out, and it looks like fairings are well on their way with just some debugging. That leaves stage 2. We didnt design stage 2 for recovery, but lets hear some proposals."

"Sir, here's a detailed proposal I worked up in my free time, and a 1 page summary why my approach is better than the others."

I would think assuming Elon was somehow "unaware" of the state of stage 2 recovery work is a very bad assumption. Just because he hasn't talked about it publicly does not mean it was 1. abandoned or 2. he is not apprised of what his company is spending money and manpower on. It appears they always have many irons in the fire simultaneously and only choose to use them when the time is right.
You assume company money/official manpower were used for the development.
I'm talking about bored engineers doodling off the clock.

Offline CyclerPilot

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Re: F9 Second Stage Reusability
« Reply #226 on: 04/08/2017 01:58 AM »
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.

Offline su27k

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Re: F9 Second Stage Reusability
« Reply #227 on: 04/08/2017 04:05 AM »
Elon's latest on twitter:
Quote
Fairing is ~$5M, but that should be reusable this year. Am fairly confident we can reuse upper stage too by late next year to get to 100%.

Just to be pedantic, he is saying they have this ability, not that they will actually do it...

Offline adrianwyard

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Re: F9 Second Stage Reusability
« Reply #228 on: 04/08/2017 05:00 AM »
I'll put in a vote for an Stage 2 EDL kit that can optionally be added on top of the stage. This has a great deal in common with a Crew Dragon, minus the crew module.

The interstage can stay with the S1 (as usual) for expendable missions, or now optionally stay with S2 if the stage is to be returned. After the re-entry burn by the MVac, the EDL kit detaches and flies to the bottom of S2 and attaches there.

Assumptions made: 1] re-using Dragon propulsion, heat shield, RCS, and navigation is a good idea. 2] relocating the kit is not a big deal in 2017 using flight-proven hardware and software, 3] the mass of the MVac means engine first entry is favored/required, 4] loads from the payload can be passed through or by the EDL kit.
« Last Edit: 04/08/2017 05:21 AM by adrianwyard »

Offline shooter6947

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Re: F9 Second Stage Reusability
« Reply #229 on: 04/08/2017 05:39 AM »

The interstage can stay with the S1 (as usual) for expendable missions, or now optionally stay with S2 if the stage is to be returned.



Isn't the MVac bell radiatively cooled?  It would overheat with the interstate surrounding it.

Offline adrianwyard

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Re: F9 Second Stage Reusability
« Reply #230 on: 04/08/2017 06:43 AM »
The nozzle extension is indeed radiatively cooled, but I'm not sure if the entire engine needs to be exposed. I'd always assumed interstages were left behind mainly to shed mass, but you could be right and what I show would cause overheating.

This needn't be fatal to the idea, however; you could shorten the interstage by x feet to expose the nozzle extension, and then bring x feet of additional enclosure with the EDL-kit.

Offline WBY1984

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Re: F9 Second Stage Reusability
« Reply #231 on: 04/08/2017 07:20 AM »
What about a cone shaped ballute that deploys from the base of the second stage? Kind if shuttlecock shaped, so that the Centre of Pressure is moved closer to that massive MVac?

An even wackier idea I had was to have the thing land on lengthy inflatable tubular 'legs' which are angled slightly outwards, so they splay outwards on landing. A series of elastic connecting straps between the legs would dampen the splaying movement, the first if which would be very elastic, and the last being the least elastic.

Probably unfeasible and I should go back to playing KSP...

Online FutureSpaceTourist

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Re: F9 Second Stage Reusability
« Reply #232 on: 04/08/2017 07:27 AM »
So Elon has a new bone to play with :D

I was thinking that this must surely only be for FH, where there's more likely to be plenty of margin to cope with S2 additions for re-use. But then I wondered - doesn't F9 S1 use a lot of fuel on a boost back burn for RTLS? So what if you took an F9 RTLS flight (e.g. CRS) and instead of doing S1 RTLS did a ballistic trajectory ASDS landing (like SES-10).

Would that give much more S2 mass budget? (obviously allowing for the much greater proportionate impact on payload mass that S2 additions have vs S1 additions)

Online FutureSpaceTourist

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Re: F9 Second Stage Reusability
« Reply #233 on: 04/08/2017 07:34 AM »
As it's been mentioned a few times, here's the 2011 SpaceX re-use animation showing the original S2 re-use concept (with S1 RTLS as well ...)


Offline MikeAtkinson

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Re: F9 Second Stage Reusability
« Reply #234 on: 04/08/2017 09:07 AM »
So Elon has a new bone to play with :D

I was thinking that this must surely only be for FH, where there's more likely to be plenty of margin to cope with S2 additions for re-use. But then I wondered - doesn't F9 S1 use a lot of fuel on a boost back burn for RTLS? So what if you took an F9 RTLS flight (e.g. CRS) and instead of doing S1 RTLS did a ballistic trajectory ASDS landing (like SES-10).

Would that give much more S2 mass budget? (obviously allowing for the much greater proportionate impact on payload mass that S2 additions have vs S1 additions)

Block 5 payload expendable is about 22 tonnes to LEO, 18.5 tonnes ASDS landing (15% reduction) and 15.5 RTLS (30% reduction).

So assuming reusability kit is 2 tonnes, F9 is probably still capable of cargo & crew Dragon missions and  half plane (25 satellite) with a RTLS landing. With ASDS landing it might just be possible to launch a whole plane (50 satellite) but I doubt it, given the figures we know.

Online AncientU

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Re: F9 Second Stage Reusability
« Reply #235 on: 04/08/2017 10:48 AM »
...
You assume company money/official manpower were used for the development.
I'm talking about bored engineers doodling off the clock.

Bored engineers at SpaceX?
Yes, that's it.  ::)
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Online FutureSpaceTourist

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Re: F9 Second Stage Reusability
« Reply #236 on: 04/08/2017 11:07 AM »
...
You assume company money/official manpower were used for the development.
I'm talking about bored engineers doodling off the clock.

Bored engineers at SpaceX?
Yes, that's it.  ::)

Yes, bored engineers about as likely as SpaceX engineers with free time ...

Online AncientU

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Re: F9 Second Stage Reusability
« Reply #237 on: 04/08/2017 11:12 AM »
For this reusability to have max financial impact on the Constellation capital expense, the dispenser will also need to be retrieved.  EM said 100%...

As discussed by many, an integral second stage with dispenser and cargo bay doors that returns as a unit would be a good investment in ConnX and a pathfinder for ITS EDL.  The rough outline of the BFS could serve as the outer mold line.  At 5-6m wide and approximately as long as current fairing plus second stage, it would be a one third scale model of BFS.

The animation shows a retractable Merlin Vac... a possibility.  ITS animation shows a section of interstage retained for an tail heat shield, which must also be workable in their hydro simulations.  With all BFS modeling done to date, they probably have a good handle on the viable parameter space for reentry configurations.

Note: Refueling is another approach to increasing the capability of second stage. Also needed for ITS operations.  And carbon composite construction.
« Last Edit: 04/08/2017 11:28 AM by AncientU »
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Online AncientU

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Re: F9 Second Stage Reusability
« Reply #238 on: 04/08/2017 11:15 AM »
...
You assume company money/official manpower were used for the development.
I'm talking about bored engineers doodling off the clock.

Bored engineers at SpaceX?
Yes, that's it.  ::)

Yes, bored engineers about as likely as SpaceX engineers with free time ...

Agree. 
This will 'divert' some talent for sure, but not a sidetrack from Mars. 
Similar to booster RTLS 'practice' they've been doing... or Red Dragon.
« Last Edit: 04/08/2017 11:24 AM by AncientU »
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Offline Robotbeat

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Re: F9 Second Stage Reusability
« Reply #239 on: 04/08/2017 11:26 AM »
Reusable upper stage work is essentially subscale ITS spaceship testing.
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