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It is 1996. For reasons best left to Worldbuilding SE, it has become a matter of civilizational life and death to send humans to the moon and bring them back to earth as soon as possible. Everybody is on board for a WWII-level economic commitment, and all the world's aerospace engineers are told to drop what they're doing and focus on this.

As a point of comparison, RAF Bomber Command suffered a 46% death rate during WWII, and that level of risk is acceptable in this scenario. I'm assuming it's not just about prestige.

So the question is, what is the winning mission profile, and what is the soonest it can be accomplished? (Surely there would be multiple parallel efforts, if this is as important as I am proposing.)

The bare minimum requirements I am imagining is that at least one person walks around on the moon and does something useful, and doesn't have to bring back any more than about 25 kg of stuff. If more ambitious missions could come a year or so later, points for imagining how they might look, too.

I had imagined you could use the Shuttle to ferry various Apollo-style components to LEO, and then do a kind of combo EOR/LOR mission. But the S-IVB (the Saturn third stage) is way too heavy for the Shuttle, I think by a factor of almost three. (Note that I am just using it as a stand in for the size of rocket you would need for trans-lunar injection. Also, of course, post-Challenger mission rules prohibiting rockets in the payload bay would surely be waived.) So how might it be done?

Some might argue this whole question should be in Worldbuilding, but I think an answer could be very informative about the principles of mission design.

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  • $\begingroup$ so the mission requirement is to be able to send one person who can land, pick up Buzz Aldrin's Planet-Saving Poop or whatever, then immediately return to LEO and re-rendezvous with the shuttle they departed from? $\endgroup$
    – Erin Anne
    Dec 6, 2023 at 0:07
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    $\begingroup$ I should expand that comment: I believe that the mission profile will be pinned to the following things: the landing weight, the landing site selection, and the ascent weight. Everything else has to flow from that. $\endgroup$
    – Erin Anne
    Dec 6, 2023 at 0:41
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    $\begingroup$ Added the fourth paragraph in response to this. So the Planet-Saving Poop Return Mission as described is indeed enough, at least for starters. But we're of course assuming that a robot can't handle it. $\endgroup$ Dec 6, 2023 at 1:10
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    $\begingroup$ I don't think the post-Challenger rules about the Shuttle payloads would be relevant...trying to do the series of launches needed on a deadline with the Shuttle would be inviting failure. You'd either end up with issues of some kind grounding them and destroying your schedule, or you'd ignore those issues and run out of Shuttles...you only had 4 to work with at that point. The Russians showed you didn't need something like the Shuttle to assemble things in orbit. You're probably better off with the Titan IV...or Soyuz and Proton rockets. $\endgroup$ Dec 6, 2023 at 1:11
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    $\begingroup$ I'm seeing a lot of answers here in the comments. But maybe that means it's a bad question. Also I think there would be some development time for another Saturn V since the same chain of contractors was no longer present, etc. $\endgroup$ Dec 6, 2023 at 3:51

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Warning: this answer is a bit more worldbuildy than rigorous.

I can see two immediately plausible routes to a lunar return mission.

Option A: This is the lower risk option (both in development schedule and execution of the mission). Simply make another Saturn V/Apollo stack (or refurbish museum pieces): With all the world's aerospace engineers and an enormous budget available, this should be straightforward, and possibly even cheaper than Option B to execute. There will be missing links in the supply/production chain, but they should be straightforward to replace; all the problems have been solved once.

Option B: Three-shuttle EOR+LOR. In this mission design, two shuttles are launched with Centaur-G-Prime stages, while a third shuttle is launched with a new, purpose built lunar spacecraft: Orpheus/Melite. Orpheus is effectively an Apollo CSM scaled down to a 2-person crew; Melite is an Apollo LM scaled down to a single crewperson. Timing will be tricky; the lunar spacecraft needs to go up first, uncrewed, and the two Shuttle-Centaurs need to launch close together in time to minimize hydrogen fuel boiloff during assembly and departure prep.

Assume the Orpheus/Melite stack masses no more than 27.5 tons, the limit for a shuttle payload to 200km LEO. A pair of Centaur-G-Primes, staged sequentially, can impart about 3500 m/s of ∆V to such a payload, which is sufficient for trans-lunar injection (about 3300 m/s).

Orpheus CSM is 8 tons dry (compared to Apollo CSM at about 12 tons), uses 6 tons of propellant for lunar orbit insertion and 2.5 tons of fuel for the return trans-Earth injection (these maneuvers are symmetrical in terms of ∆V, but the return is performed without the additional mass of the LM). The CSM uses hypergolic propellants at specific impulse of 310 seconds -- it could use the same engine as the Apollo SPS for simplicity, though that engine was oversized even for Apollo.

Melite LM is a two-stage machine like the Apollo LM. The descent stage is 1.8 tons dry + 5.5 tons propellant for a descent ∆V budget of 2200 m/s -- a bit more than the Apollos had. The ascent stage is also 1.8 tons dry, with 1.5 tons of propellant for the ascent. Again, hypergolic propellants at 310 seconds, and you could probably re-use the Apollo LMDE and LMAE.

That comes to 27.1 tons for the CSM+LM, so you have 400kg available for the mechanical connections between the Centaurs and the spacecraft.

Spreadsheet summarizing the stages of the Centaur-Centaur-Orpheus-Melite stack

I'd be inclined to skip any kind of docking tunnel between the shuttle and Orpheus, and Orpheus and Melite, in order to save mass, and board both ships via EVA. This was the strategy the Soviet LK lander would have used, and while it's a little nerve-wracking to contemplate, I don't think it's really particularly risky.

As previously noted, shuttles 2 and 3 need to launch relatively close together in time, and the assembly of the Centaurs + CSM needs to be performed rather quickly. We do have a couple of days to do it, I think -- hydrogen boil-off for a Centaur is about 4% per day, and as noted above, we have a bit of performance margin for the trans-lunar injection burn. Shuttle 2 could drop off the first stage Centaur and then deliver the lunar crew to Orpheus One, then the next day Shuttle 3 would bring the second Centaur and assembly crew to the rendezvous and get the Centaurs stacked up while the Orpheus matched orbits, then you're off to the races.

Note that both the Apollo CSM and LM were a lot bigger and more capable than you strictly need for a minimum lunar flags-and-footprints mission. Apollo was designed as a general-purpose spacecraft suitable for many kinds of missions, and could sustain a crew for more than two weeks. The LM could take the rover and hundreds of kg of experimental gear down and stay for several days. By subtracting one crew member and forgoing the docking tunnel, the command module of the Orpheus might be even more comfortable than Apollo for a one-week mission.

I don't have a confident guess for how long either of these options would take. Saturn Vs took about two years start-to-finish to build, but a lot of retooling would be necessary before that. The Orpheus option would require a lot of design, but less construction. If the stakes were truly universally understood, I think you could do option A in less than five years, and maybe attempt both options in parallel -- maybe have ESA take the lead on Orpheus while NASA focuses on Apollo 2000.

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    $\begingroup$ "what is the soonest it could be accomplished?" is hidden in the middle of the question body. My guess for 1996 NASA is a decade or, failing that, never, but that's a guess for if all of the Space Station energy was diverted to this vital moon mission. $\endgroup$
    – Erin Anne
    Dec 6, 2023 at 7:04
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    $\begingroup$ Yeah, "soonest it could be accomplished" is more opinion-y than the rest of it. I think less than five years is doable if the critically-high stakes are universally understood. It's much easier to solve hard problems when you have an existing solution to refer to -- and that applies to either of my options, in different ways! $\endgroup$ Dec 6, 2023 at 7:46
  • $\begingroup$ I usually like to wait for multiple answers before accepting one, but this one is so solid I didn't see the point. $\endgroup$ Dec 6, 2023 at 16:56
  • $\begingroup$ @ErinAnne, "All of the Space Station energy" is way less effort than I am talking about. WWII defense spending consumed 40% of US GDP at the height of the war. If you have to build more launch sites for simultaneous shuttle launches, you do it, etc. $\endgroup$ Dec 6, 2023 at 17:01
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    $\begingroup$ @MarkFoskey I think, but I'm not sure, that the calculus changes in favor of a Saturn build as available budget increases. With any new design there's always the possibility of getting into a design dead-end the requires some backtracking and redesign, and I suspect that development of Orpheus would be much more vulnerable to NASA's 1990s institutional issues than a Saturn/Apollo rebuild. With 40% of GDP in play, if I'm Emperor Of Earth, I call for a three-pronged effort: rebuild one Saturn/Apollo stack from museum pieces, build one Saturn/Apollo stack new, and develop Orpheus. $\endgroup$ Dec 6, 2023 at 20:09

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