SECOND stage recovery speculation

[malcolm]

Oh no....another tweet.

Elon Musk on Twitter

Considering trying to bring upper stage back on Falcon Heavy demo flight for full reusability. Odds of success low, but maybe worth a shot.

Also the payload for FH will be the "Silliest thing we can imagine! Secret payload of 1st Dragon flight was a giant wheel of cheese. Inspired by a friend & Monty Python."

 

[ecarfan]

This is being discussed in some other threads here, which is not to say it can't have its own thread. Extensively discussed in the SpaceX Facebook group. Very hard to do. Unclear on whether or not parachutes would be involved to help shed some velocity since the 2nd stage would be coming down from orbital velocity (meaning way faster than the 1st stage). Would require adding lots of mass to the second stage for extra fuel, maybe more small rockets for retropulsion, landing legs, heat shielding, etc.

All we can do is speculate and make relatively uneducated guesses here, unless there are some real rocket scientists who want to contribute.

 

[Nikxice]

It's good timing. Recently thought a dedicated thread pertaining to the Falcon 9's second stage would be appropriate here. This is an exciting concept that presently seems as unlikely as a first stage booster recovery did back in 2013. Eventually the thread title could be changed. Once accomplished, the "speculation" will be over.

The current focus on the second stage appears to be on recovery and reuse. I wonder if at some point consideration will be given to refueling and reuse while in orbit. It would be too inefficient to haul up more fuel from earth. If lunar or asteroid mining/processing ever works out, who knows? That idea might still seem pretty far-fetched, but we're talkin' SpaceX!

A workable solution for exploiting the value locked up in the second stage has put engineers on a quest for the Holy Grail of rocketry, complete reuse of the main components.

 

[YoungStranger]

I am guessing that the second stage would re enter the atmosphere nose first, because you could put a heat shield behind the payload., but at some point it would have to be flipped to allow main engine to slow and land.

 

[larmor]

Re capture: allow second stage to orbit on first flight. Second flight with another second stage goes into orbit, and original second stage is recaptured and comes down with booster-- this is hard, and that's why its rocket science...

 

[Doug_G]

Booster doesn't go into orbit. It's on a parabolic trajectory.

 

[larmor]

ya

Booster doesn't go into orbit. It's on a parabolic trajectory.

Correct, second second stage is directed out of orbit to meet the booster at its apogee...

 

[Grendal]

I am guessing that the second stage would re enter the atmosphere nose first, because you could put a heat shield behind the payload., but at some point it would have to be flipped to allow main engine to slow and land.

Long ago, I'm pretty sure this was how SpaceX thought to recover a second stage. A second stage can't really pull off a controlled landing like the booster does because of the lack of fuel and lack of a landing system. It's much easier to put a shield on the top and let it hit the atmosphere for slowing like a capsule. Parachutes do the final slowing and maybe they'll use chutes like the fairing and be able to direct the second stage to their desired destination. Anything else seems like they'd need to do extensive redesign on the stage which they don't really have time to pull off.

 

[malcolm]

FH payload? A Norwegian Blue?

A wafer-thin mint? (Could be blamed if the rocket blows up)

 

[Doug_G]

Correct, second second stage is directed out of orbit to meet the booster at its apogee...

Uh, yeah, that would be quite the stunt. You'd have to launch at exactly the right moment. And the orbit of the second payload would have to be similar to the first. I doubt you could pull that off even if you had everything lined up just so.

Maybe more of a Mars-style landing. Use a heat shield, then a parachute, then eject the parachute and do a powered landing.

 

[YoungStranger]

It's much easier to put a shield on the top and let Parachutes do the final slowing and maybe they'll use chutes like the fairing and be able to direct the second stage to their desired destination. Anything else seems like they'd need to do extensive redesign on the stage which they don't really have time to pull off.

Dreaming now, but the fairing could be utilised if it were hinged to the second stage and opened like a flower (strong hinges needed though) to release payload. The inside could be lined with a heat shield and the extra surface area would also slow the capsule down a little. Parachute landing I agree. The fairing could also act as legs when landing. Would have to be incredibly tough and strong to bear weight of engine to be reused though, so parhaps too much weight penalty.

 

[Uncle Paul]

Knowing Elon, his ultimate goal might be for the main booster to hover until the 2nd stage completes it's payload release, then rejoin each other for a trip back down to land in one unit. It could simply be refuled and ready to launch again in just an hour or so.

Pretty far fetched, but so is building electricity based vehicles and storage company from scratch that is now more valuable than GM or Ford.

 

[larmor]

Uh, yeah, that would be quite the stunt. You'd have to launch at exactly the right moment. And the orbit of the second payload would have to be similar to the first. I doubt you could pull that off even if you had everything lined up just so.

Maybe more of a Mars-style landing. Use a heat shield, then a parachute, then eject the parachute and do a powered landing.

Agreed... Or make parts of the rocket (1st and/or 2nd stage) out of graphene, then when both components are close, use conductivity in graphene for creating a temporary electromagnet to assist close alignment. 2nd stage would need small side engines for placement into and out or orbit...

 

[Pricee2]

Here is my speculation: Elon says the fuel cost is tiny compared to the hardware so for most LEO launches they would use the FH even thought a F9 could do the job. That way they could use the center core for most of the orbital insertion and thus not use a large percentage of the second stages fuel to get to orbit. The fuel saved could then be used for a propulsive re-entry burn to slow the second stage so no heat shielding would be needed and because the payload has been offloaded the the second stage would be much lighter. I will leave the second stage landing part for SpaceX to resolve.
I am now putting on my nomex suit.

 

[Doug_G]

Knowing Elon, his ultimate goal might be for the main booster to hover until the 2nd stage completes it's payload release, then rejoin each other for a trip back down to land in one unit. It could simply be refuled and ready to launch again in just an hour or so.

Pretty far fetched, but so is building electricity based vehicles and storage company from scratch that is now more valuable than GM or Ford.

Far fetched? You're in "perpetual motion machine" territory here. Rockets cannot hover more than a matter of minutes (or seconds). They have to expel reaction mass to propel themselves.

 

[Doug_G]

Here is my speculation: Elon says the fuel cost is tiny compared to the hardware so for most LEO launches they would use the FH even thought a F9 could do the job. That way they could use the center core for most of the orbital insertion and thus not use a large percentage of the second stages fuel to get to orbit. The fuel saved could then be used for a propulsive re-entry burn to slow the second stage so no heat shielding would be needed and because the payload has been offloaded the the second stage would be much lighter. I will leave the second stage landing part for SpaceX to resolve.
I am now putting on my nomex suit.

Nomex will only save you for a few seconds!

 

[Pricee2]

I guess I will have to use a heat shield then.

 

[Grendal]

Here is a throwback to the early days (2011!) and it includes their idea (at that time) for second stage reusability:

Amazing reminder of what they have accomplished in just six years!

 

[Brovane]

Here is my speculation: Elon says the fuel cost is tiny compared to the hardware so for most LEO launches they would use the FH even thought a F9 could do the job. That way they could use the center core for most of the orbital insertion and thus not use a large percentage of the second stages fuel to get to orbit. The fuel saved could then be used for a propulsive re-entry burn to slow the second stage so no heat shielding would be needed and because the payload has been offloaded the the second stage would be much lighter. I will leave the second stage landing part for SpaceX to resolve.
I am now putting on my nomex suit.

Keep in mind that the faster the center stage is traveling at staging, the more heat it is exposed to during re-entry.

SpaceX already has excellent TPS with PICA-X that is used on the Dragon. It would be more mass efficient to use the TPS to slow down the 2nd stage from orbital velocities than try to use fuel.

 

[adiggs]

Here is a throwback to the early days (2011!) and it includes their idea (at that time) for second stage reusability:

...

Amazing reminder of what they have accomplished in just six years!

That is a mighty fine example of imagining the future, and then willing it into existence. Considering how well step 1 of 3 has worked and is in the books, I'm not betting against them.