Recovering upper stages - in orbit?

[Codraroll]

May I ask a silly question about upper rocket stage reuse? ... oh shoot, gonna do it anyway.

Would it be possible to recover upper stages in orbit instead of on the ground?

As far as I've understood, reusability of rocket first stages is possible because the first stage neither goes particularly high up, not particularly fast - relatively speaking, of course. Reusing the second stages would be harder since they go a lot faster and a lot higher - meaning that they would have to go through almost a complete orbital reentry and somehow survive intact, as their secondary function. Their primary function, of course, is pushing a payload from the high-and-fast-but-not-too-high-and-fast position of first stage separation, and (almost?) to the desired payload orbit (unless a third stage takes care of that).

But say that the second stage is given extra orbital capabilities instead of re-entry/landing capabilities. Enough to enter stable LEO, and do some basic maneuvering. The same as what they do today, basically, but a little more.

Then the second part of the plan, where the thread tags begin to come into play. It would involve a... let's call it a "butterfly net". A spacious but empty cargo spacecraft launched in advance, which does a rendezvous with the upper stage in orbit, loads it up and straps it in. This craft would be on a fairly long mission, loading up multiple upper stages from different launches, then re-entering and landing in a fashion similar to a space shuttle once it's full. Not necessarily on a runway, but smooth enough to allow its cargo to be reused.

It would eliminate the requirement for the upper stage to be able to re-enter and land. It would "only" need to have orbital maneuverability instead. However, it's not very hard to see all the other problems it would introduce. Most prominently, the act of snagging, stowing, and securing a spacecraft inside another. And landing the damn thing while full of cargo, I presume.

One might need human astronauts to do these tasks, which means craft with crew and EVA capabilities would have to operate alongside it. Maybe the upper stages could be stored temporarily on the "butterfly net"'s exterior and then properly stowed and secured in a single manned operation once it has reached capacity (say, 4-6 upper stages). Not sure if the landing could be done remotely, but that would be preferable, that way you wouldn't have to have crew compartments on the "butterfly net" itself. It would just have to be a big box that can be launched, maneuver in orbit, reenter, and land.

I can't imagine it would be a profitable venture, since the development costs of such a program would probably be vastly more expensive than the dozens (let's say hundreds in the best case - still not enough) of upper stages it would allow the reuse of. Orbital maneuvering with a few upper rocket stages in its belly is probably not cheap when it comes to fuel either, and adding a rendezvous to every mission profile probably wouldn't be less expensive than just throwing the second stage away. Maybe second-order effects would recoup some of the costs, though.

But would it be feasible, if not economically profitable? It would require the crew and EVA capabilities of the Space Shuttle, also roughly the same landing capability, albeit split into two different craft. Orbital rendezvouz would, optimistically, be on the same order of magnitude of complexity as docking with the ISS.

 

Alternately, the "butterfly net" could instead be swapped for a manned orbital warehouse/workshop where upper stages would be collected, outfitted with heat shields, parachutes, legs, and/or what-have-you, then sent on their merry way back to the ground. Or just disassembled for parts, I suppose. Takes away the need to be able to land the big craft, at the cost of a permanent manned space operation, which we all of course know is not expensive at all.

I feel like I'm not getting any closer to a viable/economically feasible solution here, so might as well hand the microphone over to you guys. What do you think of the concept?

[DerekL1963]

2 hours ago, Codraroll said:

Would it be possible to recover upper stages in orbit instead of on the ground?

So, you've got an empty dead stage...  what are you going to do with an empty dead stage that justifies spending any money on a recovery system for empty dead stages?

[SargeRho]

2 hours ago, DerekL1963 said:

So, you've got an empty dead stage...  what are you going to do with an empty dead stage that justifies spending any money on a recovery system for empty dead stages?

Now you have a transfer stage, potential fuel depot, or potential habitat in orbit essentially for free.

[tater]

The biggest problem is probably that all these stages are in different orbits, which would require a lot of energy to police up.

In special cases, this might be useful if the stages were designed for this use. Transfers to station are the obvious choice, it's a destination with many flights, and if there were a tug to wrangle them, then they might be used for something.

[Scotius]

It would be more useful, if we'd have a facility in orbit capable of disassembling and repurposing space junk. Such spent stage delivered to this facility would turn into a nice chunk of raw materials and\or parts to be turned into something useful - a new satellite, module for a space station or spare parts. But we have a long way to go before we start building space factories

[kerbiloid]

We can start small. This but in orbit.

Spoiler

50 years later people will say thanks for it.

A nuclear-powered orbital scavenger should gather the upper stages and move them to the orbital scrapyard.

(Btw, the same theme with interplanetay ships fueling.
Instead of taxiing huge tanks up and down inside a shuttle, make them single-use and collect in the same way.)

Edited September 23, 2017 by kerbiloid

[DDE]

It's a rather dubious plan. You're simply delegating the need for reusability to an even larger spacecraft, which will be transporting mostly vacuum.

It's probably less efficient than the failure that the Space Shuttle was.

[Steel]

Isn't this argument a bit cyclical? 

For this to be worthwhile, the recovery spacecraft and it's launcher must be fully reusable (otherwise you need a recovery spacecraft to recover the second stage of the recovery spacecraftcraft and so on forever). Surely though, if we have the capability to create a fully reusable recovery craft, then you could just made slight changes to it and turn it into a fully recoverable launcher and then eliminate the need for a recovery craft in the first place? 

[Codraroll]

52 minutes ago, Steel said:

Isn't this argument a bit cyclical? 

For this to be worthwhile, the recovery spacecraft and it's launcher must be fully reusable (otherwise you need a recovery spacecraft to recover the second stage of the recovery spacecraftcraft and so on forever). Surely though, if we have the capability to create a fully reusable recovery craft, then you could just made slight changes to it and turn it into a fully recoverable launcher and then eliminate the need for a recovery craft in the first place? 

Yes, maybe.

I guess the "innovation" would be that the recovery spacecraft is launched with less payload than it lands with. Therefore, its launcher wouldn't have to be as powerful. It's launched mostly empty (save for some orbital maneuvering system and its fuel - which admittedly would weigh quite a bit), which could make it light enough to be able to push itself into orbit after first stage separation. Deorbiting wouldn't require that much fuel.

And even if it had to be launched on its own expendable second stage, it would still be able to collect and reuse a half-dozen or so upper stages for each one discarded. That's almost close to resemble economics.

Maybe it would be more useful as an orbital junkyard, as @kerbiloid suggested. Go up, collect upper stages or discarded satellites, retain them in orbit until some space shuttle-like spacecraft is developed so they can be brought down to Earth or dismantled or something. Basically a "waste bin" for potential space junk, keeping it all in a few boxes instead of floating all over the place. It would technically mean reusability, in a distant future where space travel is cheap and convenient enough to send somebody to pick them up. I'd like to see the economist who'd recommend this approach, though.

[Pand5461]

Hmm... This poses a lot of questions.

a) Not every rocket goes to one and the same orbit, and inclination changes aren't cheap

b) The "spacious bu empty" spacecraft must be very spacious to hold entire stages. Space Shuttle cargo bay was 18×4.5 meterr, roughly the size of Falcon 9 second stage, and that made the orbiter weigh more than 60 tons.

c) The stages will experience higher-than-usual transverse loads at reentry, so they must be reinforced to withstand them. Probably, they also need to maintain pressurization.

d) Most of the upper stages either don't make all the way to orbit or do not stay at LEO anyways.

e) The whole system just resembles the Space Shuttle too much. In fact, with the number of recovered stages being 1, it is exactly the Space Shuttle.

It may be somewhat viable if the collected upper stages have easily detachable engines and control units. Then astronauts can unbolt them, secure in the cargo bay and send the rest to burn in the atmosphere.

[DDE]

4 hours ago, Pand5461 said:

It may be somewhat viable if the collected upper stages have easily detachable engines and control units. Then astronauts can unbolt them, secure in the cargo bay and send the rest to burn in the atmosphere.

At which point the question is, why don't themselves do it themselves, Vulcan-style?

[Pand5461]

@DDE Vulcan is meant to have recoverable first stage, not upper stage.

[DDE]

54 minutes ago, Pand5461 said:

@DDE Vulcan is meant to have recoverable first stage, not upper stage.

For a small, dense package, as opposed to a massive rocket stage, the difference is much more miniscule, and you get to pick an arbitrary LZ.

[YNM]

So you have turned a single bulky TSTO into a less bulky TSTO and a bulky SSTO.

That's like comparing "should I get a train or a load of busses". The first one is always going to be more efficient.

Edited September 23, 2017 by YNM

[regex]

I'll bet most second stages just burn up in the atmosphere over time. Most of them aren't intended to put payload anywhere past LEO, and even if they put things into GTO they still have quite a low periapsis and so atmospheric drag will eventually take care of them.

[DerekL1963]

13 hours ago, SargeRho said:

Now you have a transfer stage, potential fuel depot, or potential habitat in orbit essentially for free.

Um, no.  You spend a great deal of money for those things.  You have the infrastructure cost of the recovery system, which is going to be expensive and which must be amortized.  For a transfer stage or a fuel depot, the fuel has to come from somewhere - and the only place that makes sense is ISRU, which brings us back to expensive infrastructure.  For a habitat, you have the man-hours to convert the stage - and the infrastructure to support your conversion crew (again, expensive infrastructure).  Etc... Etc...

Not to mention you have to convince the rocket builders to make the (expensive) modifications to their stages to enable all of these things.  Modifications such as making the batteries accessible for replacement.  Ordinance and toxic systems will also have to be redesigned to allow for safing on orbit.  Etc... etc...  Who pays for that?  Folks purchasing launches for their own use sure as heck aren't going to.

(Rant:  Once again, space cadets understand neither accounting nor economics.)

[Pand5461]

14 minutes ago, regex said:

I'll bet most second stages just burn up in the atmosphere over time. Most of them aren't intended to put payload anywhere past LEO, and even if they put things into GTO they still have quite a low periapsis and so atmospheric drag will eventually take care of them.

Not the GTO ones, no http://stuffin.space/?intldes=1971-116B&search=centaur

[regex]

28 minutes ago, Pand5461 said:

Not the GTO ones, no http://stuffin.space/?intldes=1971-116B&search=centaur

They will eventually, especially those with a lower periapsis. Using them meaningfully would require another GTO launch to recover them followed by a boost in one direction or another to bring them to a useful orbit. Better to let them decay naturally; the energy required to use them is very expensive for what you're getting.

[wumpus]

27 minutes ago, DerekL1963 said:

Um, no.  You spend a great deal of money for those things.  You have the infrastructure cost of the recovery system, which is going to be expensive and which must be amortized.  For a transfer stage or a fuel depot, the fuel has to come from somewhere - and the only place that makes sense is ISRU, which brings us back to expensive infrastructure.  For a habitat, you have the man-hours to convert the stage - and the infrastructure to support your conversion crew (again, expensive infrastructure).  Etc... Etc...

Not to mention you have to convince the rocket builders to make the (expensive) modifications to their stages to enable all of these things.  Modifications such as making the batteries accessible for replacement.  Ordinance and toxic systems will also have to be redesigned to allow for safing on orbit.  Etc... etc...  Who pays for that?  Folks purchasing launches for their own use sure as heck aren't going to.

(Rant:  Once again, space cadets understand neither accounting nor economics.)

As far as I know, it would have certainly been possible to take the shuttle's fuel tank into orbit.  I suspect this decision had to be made back at design time, and as the rest of the STS program was being canceled, there was no reason for this capability (and less reason to do it with a nuclear tug).  Once the ISS and CanadARM were in place, grabbing the tank and draining what's left would have been possible (without exhorbinant costs).  There's still a useful amount of oxygen, but even that would be hard to keep in a closed-cycle system (storing the fuel was likely beyond our capacities).  Presumably the point would be for fueling shuttle delivered spacecraft for escape trajectories.

It looks like all the big pieces were in place, and it might have been tried had there been RP1 in  the fuel tank (you would likely lose the LH2 before the next shuttle launch).  I have no idea how much fuel was left in the thing (most suggestions wanted to use the fuel tank more as structure/storage on the ISS), nor how hard fueling a probe brought up on the shuttle would be.

I have to admit that having an upper stage in space sounds cool, but only works at the KSP level.  The complexity of trying to transform a rocket (which has next to no "fudge factor" and needs to be extremely purpose built) into something else is almost certainly harder than recovering the upper stage in the first place (and I'm not too optimistic on that in general).

[Pand5461]

@wumpus managing a huge half-empty tank in microgravity is... complicated. The CoM just won't stay  in place relative to the control thrusters. IIRC they even vented all remaining hydrogen before tank jettison. This, I guess, was the reason why its possible use was as structure, not as a tank.

[Racescort666]

Essentially ACES is supposed to be like this, i.e. still usable after payload deployment. ULA has talked about adding the ability to refuel ACES on orbit but I think the biggest advantage that ACES would have is a more reliable disposal burn. ULA has also mentioned a 1 up/1 down launch strategy that a long duration upper stage like ACES would be able to help accomplish. For GTO, everything is in a very similar orbit so it's not too big of a stretch to do something like this.

[SargeRho]

1 hour ago, DerekL1963 said:

Um, no.  You spend a great deal of money for those things.  You have the infrastructure cost of the recovery system, which is going to be expensive and which must be amortized.  For a transfer stage or a fuel depot, the fuel has to come from somewhere - and the only place that makes sense is ISRU, which brings us back to expensive infrastructure.  For a habitat, you have the man-hours to convert the stage - and the infrastructure to support your conversion crew (again, expensive infrastructure).  Etc... Etc...

Not to mention you have to convince the rocket builders to make the (expensive) modifications to their stages to enable all of these things.  Modifications such as making the batteries accessible for replacement.  Ordinance and toxic systems will also have to be redesigned to allow for safing on orbit.  Etc... etc...  Who pays for that?  Folks purchasing launches for their own use sure as heck aren't going to.

(Rant:  Once again, space cadets understand neither accounting nor economics.)

And that changes nothing about the fact that the stage is already in orbit. You didn't pay extra to get that stage there, it's basically junk. Someone can now come along, and recycle that stage. Or a new launcher could have a stage already developed with in-orbit reusability in mind.

Either way, you ranted about something I didn't even begin to get into.

[mikegarrison]

There were many, many proposals to do exactly this with the Space Shuttle external tank. Not so much to return them to the ground, but to use them for orbital habitats or storage tanks or some kind of orbital infrastructure.

It never made it past the science fiction stage.

First of all, as noted, these stages would all be in different orbits, so it wouldn't be completely free to gather them in one place. But a large number of shuttle flights did go to the same place (the ISS), and we could have gathered a bunch of shuttle tanks there.

But what would we do with them? They aren't designed to do anything except hold hydrogen and oxygen. The tanks would have had to be redesigned from the start in order to be easily converted to something else. Not cheap or easy.

There was a proposal back in the Apollo days to make a space station out of a Saturn IIb stage. https://en.wikipedia.org/wiki/Wet_workshop But in the end, the US decided to make Skylab a "dry workshop", in other words a space station purpose-built on the ground rather than assembled out of the hulk of a lifting stage.

[DerekL1963]

3 hours ago, wumpus said:

As far as I know, it would have certainly been possible to take the shuttle's fuel tank into orbit.  I suspect this decision had to be made back at design time, and as the rest of the STS program was being canceled, there was no reason for this capability (and less reason to do it with a nuclear tug).  Once the ISS and CanadARM were in place, grabbing the tank and draining what's left would have been possible (without exhorbinant costs).

It was only possible if the tank was essentially the only cargo carried to orbit.  (And really only if the orbit was fairly low inclination, not to ISS at all.)  The Shuttle had no capability of significantly maneuvering with it still attached due it's weight.  The CanadARM couldn't do anything with it either, as the tank VASTLY exceeded the weight it was designed to handle.

 

2 hours ago, SargeRho said:

Either way, you ranted about something I didn't even begin to get into.

I ranted against the claim you made that they were "essentially free" (they aren't), and against the uses you claimed they could be put to.

[SargeRho]

22 minutes ago, DerekL1963 said:

I ranted against the claim you made that they were "essentially free" (they aren't), and against the uses you claimed they could be put to.

But I did not claim that they are free. I said they are *in orbit* essentially for free. Did anyone pay extra money to get that stage there? No, they did not. It's waste. Scrap. Something that would re-enter the atmosphere in a few years and put on a nice fireworks display in the night sky.

With adequate recycling tech, you can grab them, and repurpose them. I didn't even go that far. My claim starts and ends at SECO. The DEXTRE arm extension for example, or a descendent thereof, can refuel satellites that were never built to be refueled. Are you telling me it's physically impossible to cut bolts and cables in space?

Edited September 23, 2017 by SargeRho