The space brainstorm continues! In particular, I turn to the question of “what happens with the next lunar landing mission?” and the human spaceflight effort in general; in my alternate-historical science-fiction universe, as I depict in my story “Wings of Fire”, the first manned lunar landing suffers an Apollo 13-style disaster, but in this case, it forces the crew on the surface to rough it for two months with improvised periodic resupply, until the second rocket is ready and the mission that carries (lander, command-service module, and all) is repurposed into a rescue mission. I’ve already explored ideas for what happens after Wings of Fire.
It’s an interesting period, because the immediate aftermath, the alternate-historical 1950s, is sort of a golden age for Apollo-style chemical rocketry. Nuclear pulse propulsion is nowhere near ready, and even nuclear thermal rockets based on reactors are perhaps not quite ready.
The obvious next move is to lean on “lunar surface rendezvous” techniques as well as the (then) new discoveries of lunar ice, and the knowledge of peaks of eternal light, to send the next mission to establish a permanent base near the lunar poles, where solar power is abundant on the mountainsides, greenhouse-based agricultural experiments can be conducted, and in-situ resource utilization with ice and regolith can be prototyped. Not to mention scientific research into the secrets this ice might contain (Antarctica and Greenland’s cores already reveal so much; imagine what’s preserved in lunar ice…). All of that will of course take a while. And in the meantime the default space program (German-led) uses a very Saturn-Apollo-style architecture, expendable rockets and capsules and all, albeit somewhat bigger in proportion than our Apollo program (larger crews are sent to the Moon with more supplies).
Needless to say this architecture is expensive and has certain drawbacks. How long would they want to just keep it flying as-is? And what sort of advancements might we see? One obvious avenue of evolution is the capsules: capsules are space- and mass-efficient, and have a straightforward profile for re-entry…but they tend to fall into the Earth’s atmosphere with high g-force and their trajectory is like a brick. They just fall down to splashdown passively; the only reason the crew aren’t killed on impact is because parachutes slow them down. What if the vehicle could re-enter more gently and could be steered around independently? Perhaps even come down to earth on a runway with landing gear? This, of course, is the fundamental idea behind spaceplanes, such as the Space Shuttle, but there is an intriguing intermediate possibility: lifting bodies, which I’ve written about before. Lifting bodies use their fuselage to generate lift and lack wings; more mass- and space-efficient than a winged spaceplane, yet it has crossrange and a gentler re-entry profile, unlike a capsule.
Reusability can be accomplished with any variety of architecture (as SpaceX has demonstrated), but a lifting body that can actually land horizontally on its own power and isn’t put through as much hell on re-entry is just going to be easier to re-use for another mission. This would be especially true for a spacecraft designed for lunar missions, ironically enough. A spacecraft returning from the Moon is going to be re-entering at a distinctly higher velocity than a low-Earth-orbit craft, so the reduction of thermal and g-force stress matters more in this case. The penalty you pay with a lifting body design is more mass, because more structural weight is needed (that big fuselage…). But if you already are using a super-heavy-lift rocket it doesn’t matter too much; it can be worked around, because you have the margin to take away a gram here to put there. “Every gram counts”, but life is a lot easier when you have more grams you can lift…
Crossrange perhaps was the most overrated property of the Space Shuttle, since a capsule can just loiter in Earth orbit (or around the Moon, as the case may be) until an appropriate window of descent appears. But there is one architecture for which croossrange would be genuinely useful, and it comes from an unexpected place: a lunar cycler.
The question of what the first space station is has bedeviled me for a while for my alternate timeline, since in a space-race environment an ISS- or Mir-style low-Earth-orbit station just doesn’t seem very useful. When you can just send big modules to the Moon directly, the idea of using a station as an intermediary sorta loses appeal…unless it’s big. Think Skylab-sized or bigger.
I’m considering that Skylab was launched with the same rocket that can take a small payload to the Moon; the Saturn V, for example, was capable of 43 tons lifted to trans-lunar injection, but a whooping 140 tons to low Earth orbit. That’s a decent-sized habitat module. Loft something like that to low Earth orbit, and you have your station…but then add 3 kilometers per second of delta-V (change in velocity) to it, and suddenly you can send it on a trajectory that takes you around the Moon…and back again to the vicinity of low Earth orbit. Time it right and your station can make a repeating loop between Earth and Moon. A variety of cycler orbits are possible, but the simplest repeats about once a month. The elegance of the “cycler” approach is you can use a large habitat for transit without having to lift the entire mass up every time. All you need is a crew vehicle with enough speed to reach it.
Which is an issue: even swinging close by Earth, a cycler is not in a low orbit. The delta-V needed to reach it from Earth’s surface is on the order of 11 kilometers per second, not the 8 required to reach a LEO station like the ISS. By the same token, when your crew vehicle detaches from the cycler on the way back, you’ll enter Earth’s atmosphere at that 11 kilometers per second. Which sounds fine…until you realize that a cycler’s trajectory is fixed. It only comes around once a month. And it cannot be altered just so you land in a certain area. So the area the Earth presents for you to land at is going to be where you end up: it’ll be essentially random. But if you have even modest crossrange ability, you can glide in and choose your exact destination across a wide region, instead of the narrow keyhole a capsule has to fall into.
The fact lunar transit is in high demand with the ongoing Moon program might make it attractive for a competing power to place a space station in orbit and then turn it into a cycler; with a much more capable spacegoing vehicle than what’s on hand with the capsules, how could our cosmonauts resist hitching a ride on it? Capsules can manage, for the time being, but after a while, a next-generation crew vehicle will be engineered, and with a lunar cycler architecture baked in, lifting bodies and even spaceplanes all of a sudden look very practical, not quixotic.
So the logical next step is lifting bodies, perhaps designed to be reusable, at least in part. The re-entry profile is harsh, and materials science even in a more advanced 1950s is not exactly advanced…even if it is perfectly adequate for the thermal demands of atmospheric entry. Even a material as “low-tech” as balsa wood has been used successfully in real life, and materials like fiberglass were already known in the 1930s (“reinforced carbon-carbon” was known in the 1950s in real life and was originally developed for high-performance rocket vehicles, so my timeline’s people might have it available).
The fundamental approach to entry here, as with Apollo, is “ablative” heat shields — material is designed to melt off and is thick enough for the amount of melt-off to not damage the actual spacecraft. This is different from the Shuttle’s approach of primarily using ceramic tiles to keep heat out, which can be reused and reflown on the next mission instead of being thrown away. But this is complex, cutting-edge, and maintenance-intensive. Instead these alternate 1950s lifting bodies might have a disposable module consisting of something like fiberglass armor with a balsa wood core, which is designed to be detached from the spacecraft and expended after each mission. The rest of the craft could be reusable.
Already this is a distinct, though technically very plausible, sequence of events, but it gets even fancier, I suspect. I’m considering that in real life we have runways and airstrips everywhere…but this was mostly because World War II inspired an enormous build-out of runways for military reasons. There are no world wars in this timeline, so runways are much scarcer; instead “seaplanes” designed to land on water remain much more dominant for much longer. In a world like this, the idea of using the water as a runway would occur to spaceplane/lifting-body designers. Saltwater doesn’t play well with sensitive spacecraft parts, and the requirements for hypersonic entry and hydrodynamics conflict, and more importantly add even more weight to the vehicle…but would we see enough concessions to the seaplane concept to at least make a water landing technically doable, even if not preferable? Probably yes. Which would lead to subtle differences in hull shape and features compared to any lifting-body design offered in real life.
Another difference might be color and texture. Almost every spaceplane and lifting body proposed in recent decades has this whale-like coloration of black on the bottom side, white on the top side. The reasons for black on the bottom are simple: charring on entry tends to make any material you’d use black anyway, and a lot of materials you’d want to use just happen to be black in color even before they’re subjected to blinding plasma. So that makes sense. But why white? White is good for thermal management, since it reflects more sunlight than darker shades. That’s really the reason. It also tends to show cracks, damage, and defects well (black, famously, is forgiving as far as covering up damage is concerned…), but the same applies to the shiny metallic silver-y color and texture seen with Apollo-era capsules. A lot of it also comes down to choice of materials: without paint a lot of composites look white-ish anyway, whereas metal looks…well, metallic. Metal is also fairly good at reflecting sunlight (hence why chrome trim in cars, for example, is blindingly brilliant in desert sunlight…).
Anyway, there seem to be a certain range of options…and engineering practicality might not win the day here, as it has in real life. In a world obsessed with the space race, where competition is fierce and multiple powers are trying to grab attention, theater and spectacle matter at least as much as the nuts and bolts of engineering. A lifting-body design might be pursued early on as much because it looks more “advanced” and “futuristic” as for any technical reason.
So would basic white paint really be on the dorsal side? A brilliant metallic finish that reflects sunlight like a chrome car’s accent pieces might be favored. Perhaps silvery, but a gold-colored metallic finish would also be a serious contender (gold foil is used in certain space contexts in real life already, just not for the skin of manned vehicles). More reddish colorations evoking copper are also a possibility, and different lineages of vehicles from different programs might even “brand” themselves with distinct finishes on their spacecraft. Silly? Perhaps, in a world where the only competition was the Soviet Union, but in this world? It would seem an obvious and easy win for publicity (while staying well within realistic design constraints).
The drive for “reusable” “advanced” craft might even extend beyond the crew capsule. Consider that after a conventional rocket lifts the stack to low Earth orbit in two stages (a la the Saturn V) an additional stage is needed to deliver that last 3 kilometers per second of delta-V. “Earth Departure Stage” (from the Constellation Program) is my favorite name for such a component, but the first of its kind that flew was the S-IVB of Apollo. The purpose of these stages is to kick the payload above low Earth orbit, to the Moon or in this case to a lunar cycler. And afterward they’re…discarded. The S-IVB stages that pushed Apollo capsules to the Moon ended up in heliocentric orbits, or were crashed into the Moon (yes, on purpose, in order to seismically probe the Moon’s internal structure).
What if they could be brought back down to Earth and reused again? SpaceX in real life has demonstrated the viability of the basic idea, though it would be a bold move indeed to fling a spent stage around the Moon and then have it re-enter and touch down. Obviously something like the S-IVB is not designed to enter the atmosphere, but what if it was redesigned for the rigors of re-entry? Assuming it’s flung on a free-return trajectory, it too would have a similar problem: needing crossrange…which it could well get if it were a lifting-body craft as well.
Obviously this adds mass and complexity to the vehicle, but experimenting with reusability while also being able to (conservatively!) keep the same rocket-launch stack you’re already churning out of the production line is an attractive prospect. Plus it leads to the visual wow factor of a craft in orbit that consists of a big lifting body (the fuel tank, with aerodynamic elements serving as the hull) tugging another lifting-body craft to the Moon, both of them with a shiny metallic finish.
After it’s flung around the Moon, the Earth Departure Stage could re-enter the atmosphere, and control its own trajectory so it comes in for a landing just like any other aircraft, only unlike most aircraft its arrival would be an event. My world is one where airship technology was pushed to maturity and in the 1950s there are surely large cruise zeppelins in recreational use. Why wouldn’t a rocket company in charge of such an Earth Departure Stage fly zeppelins with spectators out to appropriate vantage points to where they can see that glistening Earth Departure Stage return from flying around the Moon, on its way to touching down with its landing gear on a runway (or the sea, as the case may be).
The vehicles could even put out airshow-style smoke (though given their flight profile the exact techniques used might be rather different from a normal air show, but the concept carries over) to announce their presence, or to send some symbolic message (different colors of smoke being associated with company colors, or perhaps even tracing out Morse Code messages in the sky).
The fixed nature of cycler trajectories also means that if there’s more than one launch using it to get to the Moon, the re-entries of multiple vehicles will occur at the same time, and could easily use similar trajectories. Net effect: the possibility of double re-entries of lifting bodies being observed from these zeppelin decks.
Very “Sky Captain and the World of Tomorrow”, yet it’s technologically and economically plausible if the will and mindset was there. Even before the advent of nuclear power plants (another upper-stage upgrade which we could contemplate, a la NERVA!), once you get imaginative with aesthetics and theatrics and public involvement, there’s almost no limit to the pure space-age vibes that could be created. And that idea — a window into what a real space age would have been like — is almost too much for me to resist writing a story about. Not in a writer’s mood for the time being, but one of these days…one of these days…