The Early Lunar Shelter: Stay Just a Little Bit Longer

Garrett AiResearch Lunar Shelter

The Garrett Early Lunar Shelter, showing its roots in the LM Truck and, in turn, the LM that actually landed on the Moon. The tanks draped around it are hydrogen and oxygen for the fuel cells, shelter pressurization, and recharging the astronauts’ suits after EVA. Public Domain image via NASA from Early Lunar Shelter Design and Comparison Study, Volume IV. Click for a larger view.

What it was: A two-astronaut shelter/living quarters for use with the Apollo program once it had progressed to needing 30-day stays on the surface, studied in 1966-67 by Garrett AiResearch at NASA’s request. Variants for three astronauts and for a mobile version that could be hitched to a lunar rover were also examined.

Details: Certain big names show up repeatedly in conjunction with the American space program: North American Rockwell, Grumman, Boeing, Lockheed, and so on. Around the fringes, though are less familiar names such as Bendix and TRW. Another one of the latter was Garrett AiResearch, a mid-sized aerospace pioneer best known (at least as far as the space program goes) for designing and building the atmosphere controls for Mercury, Gemini, and Apollo.

In 1966, NASA commissioned Garrett to move beyond what they’d done to that point, and work on a  full-fledged, if tiny, Moon base. Dubbed the “Early Lunar Shelter” (ELS), the intention was to build it following the J-Class missions—what turned out to be Apollo 15 through 17. Having progressed from short surface stays like Apollo 11 to longer ones that had a lunar rover to work with, like Apollo 17, the next step was to be month-long stays and that required more than a single LM.

From the beginning, the Moon landings had been quite restricted in mass, as much of an LM was taken up with astronauts, the consumables they needed, and the fuel and engines needed to get them back to the CSM for the flight home to Earth. If you could forgo all of that with an automated lander, you could haul a lot more equipment to the Moon—to wit, 4.67 tonnes of it.

The fruit of this thinking was the LM/T, or Lunar Module Truck, which was for all intents and purposes a rocket-powered mule that would head to the Moon some time before its associated astronauts would start their journey in their own LM (called the LM Taxi in this context). Landing close to the LM/T, the astronauts could walk over, unload everything, and enjoy a huge quantity of equipment as compared to Aldrin and Armstrong.

There were any number of configurations for the LM/T, constrained only by the volume an LM occupied on top of a Saturn V and the limit to the mass it could safely land, but the Early Lunar Shelter was the answer to one particular question: “Suppose we devote the Truck’s volume entirely to living quarters for two astronauts and the scientific equipment they’d use. What would that be like?”

What Garrett came up with was a stubby cylinder, 8.1 feet in diameter and 16 feet long (2.5 meters by 4.9 meters) which rested on its side above the LM/T’s descent stage, looking not unlike contemporary bathyscaphes. It would be launched atop a Saturn V along with a crewed CSM, which would dock to a hatch on its upper side, then ferry it to the Moon after the usual Saturn IV-B trans-lunar injection. After reaching their destination, the CSM would disengage and return its crew to Earth, while the ELS would land automatically.

The shelter could sit on the Moon for as much as six months before its astronaut-dwellers arrived (thanks to another Saturn V/CSM combination), with a minimum seven days prior to their launch for checkout of the shelter. A SNAP-27 radiothermal generator would power the ELS until activation. Once aboard, the minimum time the astronauts would use it was assumed to be 14 days, with 50 days being the upper end of possibility. The first day days of the mission would be devoted to the astronauts activating the shelter for their use, unloading it, switching the shelter to running off fuel cells (which would also supply water) and transferring the RTG to their LM Taxi so their ride home could be deactivated but kept “alive” until it was needed at the end of the mission.

Interior layout of the Early Lunar Shelter

The interior layout of the ELS, same source as previous. One presumes the outer hatch was closed when the toilet was in use. Click for a larger view.

The interior of the shelter was to be divided into two main areas. One was a lunar EVA airlock taking up one end, the CSM hatch on top being used solely for docking with a CSM. It would have been big enough for two astronauts at the same time as well as storage of two hard space suits. The bulk of the shelter was 628 cubic feet (17.8 m3) of living space. Though about half of this would be taken up with supplies, bunks, and spacesuit storage, its shirt-sleeve environment compared well with a regular LM’s 4.5 cubic meters of habitable volume. Alternatively, as the Moon does supply gravity, the ELS can be sized another way: it would have had 68 square feet of floor space (6.3 square meters).

The arrangement of bunks/radiation refuge quarters in the ELS.

The spartan arrangement of bunks/radiation refuge quarters in the ELS. No Apollo astronaut was taller than 71 inches. Same source as previous. Click for a larger view.

The shelter was double-walled aluminum and fiberglass (the latter in the inside), with 58 mils (0.058 inches, or 0.15 cm) between them for meteoroid protection—the usual tactic, as invented by Fred Whipple. The other major danger entertained was radiation, and the aluminum walls couldn’t be made thick enough to sustain 500 rads (a hypothetical solar flare) without weight close to a half ton more than was otherwise necessary. Accordingly the study suggested putting the necessarily numerous  PLSS recharging canisters (for the life-support backpack worn while on the surface) stored in water filled sleeves around the bunk area located at the opposite end from the airlock. Altogether, they, the walls, and the bunk material made an acceptable, if awfully cramped, radiation refuge for everyone on-board.

One final, intriguing safety touch was the dual-purpose boom attached near the airlock. While primarily intended for unloading instruments or a rover, it would also have been used to get an incapacitated astronaut up next to the entrance to the shelter.

Arranged around and behind the shelter were four tanks: one compressed gaseous oxygen, one liquid oxygen, and two liquid hydrogen. These weren’t intended for use with the Truck’s landing engine—it had its own tankage—but rather for use by the astronauts and the fuel cells (and so, accordingly, their water). Garrett pinpointed the storage of LOX and LH2 for up to six months before the astronauts arrived as the main technical challenge facing the ELS.

Another issue was what atmosphere they would breathe: pure oxygen at 5.0 psia, or nitrogen/oxygen mix comparable to Earth. The former was desirable for mass reasons, and to keep the ELS as close in technology to the rest of the Apollo program as possible, but Garrett were concerned that there were no medical studies of a pure oxygen atmosphere for a long period of time; the 30-day maximum they note was apparently just an educated guess. They ended up punting the problem down the road as essentially an issue of how much they could keep the ELS from leaking; if that could be minimized, the problem was moot. Safety concerns weren’t mentioned at all, and in fact the final filing of Garrett’s study was on February 8th, 1967, not even two weeks after the Apollo 1 fire. After that the CSM would switch to a oxy-nitrogen atmosphere for launch, though the LM would stay with the low-pressure pure oxygen.

Mobile ELS variant, hitched to a notional rover.

The Mobile ELS variant, hitched to a notional rover. Same source as previous. Click for a larger view.

As well as being a shelter, the ELS would have been a miniature scientific outpost. It would be equipped with a drill capable of getting 100 feet down into the Moon’s crust, carry explosive charges for seismic readings, and had three remote instrument stations that would be deployed far from the landing site thanks to the extended EVA capability the shelter would provide. All told, the shelter would come with 3470 pounds (1.57 tonnes) of science gear, while the shelter itself was a remarkably light 985 pounds (447 kg). Add in the expendables and altogether it could be successfully landed on the Moon by the LM/T with a mere pound and a half to spare. Let it not be said that they didn’t squeeze all the juice out of this one.

If the project had gone ahead, Garrett anticipated that the ELS would be operational in 1972. The study is silent on cost, apparently because the construction work was to be handed off to Grumman, and so it was their problem.

What happened to make it fail: It got caught up in the rapid ramping down of the Apollo program that started in 1968, not least the fact that Saturn V production was shut down and the rockets they had were all they were going to get.

By scrimping and saving (and cutting a couple of Moon landings) NASA managed to save Skylab, and eventually the detente-driven Apollo-Soyuz Test Project, but that was it. As any mission involving the Early Lunar Shelter was going to require two Saturn V launches it was an obvious target for a cut, taking up as it would two slots that could be used by two different, separate Moon missions. It was one of the first things to go, and did not make it out of 1968.

What was necessary for it to succeed: It’s interesting to compare the Early Lunar Shelter to the other Moon bases we’ve examined so far, Barmingrad and Project Horizon. Both were hugely ambitious and nowhere near happening in reality, while for this project the key word was early. A lot of people tend to conflate Moon bases with lunar colonies, or at least the next rank down of permanently inhabiting the Moon even if the personnel are swapped out periodically. What NASA put its finger on was that we’re not likely to make that big a leap all in one go. The first lunar bases are probably going to be temporary, just like the first space stations were before we worked our way up to Mir and the ISS.

On that basis it’s easy to get the ELS to fly, as it was a big part of the logical next step in lunar exploration (ignoring the elephant in the room that was automated exploration, mind you). With probably no more than some minor redesigning there could have been one on the Moon just a few years after when Garrett AiResearch pictured it: 1972.

As ugly as the post-1969 picture was for NASA’s funding, it’s not too much of stretch to see the three or four more necessary missions past Apollo 17 making it through the budget grinder and “Apollo ELS” flying sometime around late 1974 or early 1975. It’s a lot likelier than much of what NASA proposed post-Apollo 11, at least, if only because one mission like that would be as much or more of a punctuation mark at the end of the program as any other mission bar Apollo 11 itself.

Sources

Early Lunar Shelter Design and Comparison Study, Volume I and Volume IV, W.L. Burriss, N.E. Wood, and M.L. Hamilton. Garrett AiResearch. Los Angeles, California. 1967.

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The Martin 410: Apollo of Santa Ana

martin-410-cutaway-diagram

A cutaway view of the Martin 410 as it would have been configured en route to the Moon (excepting the escape tower, at left, which would be ejected after launch). Note the lifting body shape of the crew compartment, and the stubby cylinder of the habitation module enclosed in the larger toroidal equipment and propulsion module. Image from Glenn L. Martin Company’s “Apollo Final Report: Configuration” delivered to NASA in 1961. Click for a larger view.

What it was: One of several formal proposals made to NASA in 1961 as part of the design competition for the Apollo spacecraft. It had certain similarities to the one that was actually built (as did all of the proposals, as they had to meet criteria set by NASA) but was primarily different in two ways. As Apollo was still pictured as a direct descent mission at the time, it didn’t use the Lunar Orbit Rendezvous technique that was used for the real missions, and the re-entry vehicle was a lifting body instead of a ballistic capsule.

Details: On October 9, 1960, fourteen different companies answered NASA RFP-302, which asked them for feasibility studies on advanced manned spacecraft for the upcoming Project Apollo. Among them were Lockheed, Boeing, General Electric, and Grumman, as well as the subject of this post: the Glenn L. Martin Company of Santa Ana, California.

Within two weeks the contest was down to three: GE, Convair, and Martin with what they called their Model 410. Up against the contractors was an internal design by NASA’s Langley Research Center, specifically their Space Task Group, which had designed the Mercury capsule. Time passed and with the agency buoyed by the first successful American manned spaceflight on May 5, 1961—Alan Shepard’s Freedom 7—May 17 saw the final proposals for all four on NASA desks and the process of evaluating and deciding between them underway.

Eight days later John F. Kennedy challenged Congress to achieve “the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth”, and things changed—the White House had had its interest piqued back in October when the study contracts were awarded and had been working behind the scenes with NASA. The Langley group rapidly metamorphosed into the much-larger Manned Spacecraft Center—now the Johnson Space Center—and by September started the move to land in Texas donated by Rice University (which is why Kennedy’s second famous space speech, the “We choose to go to the moon” one, was made there).

langley-apollo-design

The suggested layout of the Apollo spacecraft for the second phase of the competition. Note the considerable similarity to what actually got built. From Chariots for Apollo: A History of Manned Lunar Spacecraft. Click for a larger view.

Even before then, the Langley group had swung into action. Their chief engineer was Maxime Faget, an American of Belizean birth, had designed the Mercury capsule, and his head of engineering (Canadian Jim Chamberlin, formerly of Avro) was in the middle of designing the Gemini. Their job was to synthesize what the contractors had developed with their own design and use it to develop a new set of specifications—in actuality, a nearly complete design of its own—that could meet Kennedy’s challenge. While the three previous contractor proposals had been paid for by NASA to the tune of US$250,000 apiece (though all of them took a loss, spending in excess of $1 million apiece), the other contractors had been encouraged to carry on with their work on their own. This attitude now paid off: a new competition was begun for a final design, open to all groups who’d tried back in October not just the three previous winners. On July 28 twelve contractors (two had dropped out back during the first phase, Cornell and Republic Aviation) were asked to submit again based on the new prerequisites. Several of the contractors teamed up with each other, reducing the number of replies to five, but Martin once again went with the M-410 on their own.

Not counting the rocket adapter ring (which all the proposals had so they could mate to the upper stage of a Saturn), the M-410 was made up of three parts: a command module for use any time an engine was burning and for re-entry, a mission module in which the crew would live at other times, and a composite equipment and propulsion module.

The command module was the most interestingly divergent component compared to the Apollo spacecraft that actually got built. All three contractors evaluated ballistic, winged, and lifting body re-entry vehicles. The latter was a particular one NASA called an M-1, and Martin went above and beyond by evaluating a number of other shapes in all three categories before settling on a variation of the M-1. Their solution made the M-410’s re-entry moderately controllable, especially as it would have had four control flaps; Martin considered this a big improvement on Mercury or the Soviet Vostok. It would have been built out of aluminum alloy, and had a composite heat shield made out of ablative material and a superalloy (undecided at the time, but something like René 41 or an Inconel). The version of the M-410 submitted post-Kennedy’s speech was also unusual because of the four rectangular flaps that would deploy from its underside, which would expose solar panels to power the craft. During launch the command module had an emergency escape tower perched on top of it, though this would be jettisoned on reaching 90 kilometers in height.

The three crew would live for the majority of their mission in the mission module. This supplied a little over eleven cubic meters on top of roughly the same for the command module (contrast this with the 12.9 cubic meters of the combined Apollo Command Module and LM).

These two were then mated to the equipment and propulsion module. As well as the usual electronics for a Moon-bound manned spacecraft, it packed a single LR-115 engine (a design which later evolved into the R-10 and derivatives used for the Saturn I and the Centaur) and 4740 kilograms of liquid oxygen and liquid hydrogen.

Having launched in an unspecified way (NASA was still trying to decide if they were going to use multiple smaller rockets to establish a fuel depot in orbit, or go as they actually did with a larger rocket like the Saturn V), Martin suggested that the M-410 be sent on its way to the Moon using a lower stage attached to the rocket adapter ring. This stage would have contained roughly 13 tonnes of LH2 and LOX and been pushed by three LR-115s.

This was powerful enough to get it down to the Moon, because the entire thing was designed to land there. Exactly how this was to be accomplished remained to be seen, as NASA was then in the middle stages of its most historic argument: land directly via an Earth Orbit Rendezvous profile, or send a separable landing module and rendezvous above the Moon. Going in to the proposal period it was assumed that the former was likeliest, though the contractors were asked to consider what they would have to do if the latter won (as, of course, it did).

artificial-gravity-on-the-martin-410

One of the ideas studied, but explicitly rejected, for giving the M-410 artificial gravity: spin it up using the booster stage as a counterweight. From “Apollo Final Report: Configuration“. Click for a larger view.

Assuming it did land directly, though, the lower stage would be left behind as the propulsion module had sufficient thrust to lift itself back off the Moon and home to Earth. One thing the lower stage would not be used for was the generation of artificial gravity—Martin took the time to figure out if it were possible to generate a bit of it during the mission, including putting the lower stage out on a tether and using it as a counterweight to spin up the rest of the craft. They decided that for a trip as short as one to the Moon it wasn’t worth the extra weight needed for systems that could pull the trick off.

At the end of the mission, the command module would separate from the rest of the craft and re-enter. The M-410’s CM lifting body was designed to touchdown on water or land, with a combination of parachutes and retrorockets slowing it to just one meter per second as it touched the ground.

What happened to make it fail: On October 9, 1961 the new proposals were received, and two days later the five competing contractors gave presentations on their work. The evaluations began immediately thereafter, and were completed on October 28th. At the end of the competition, the M-410 was first with an average score of 6.9 points in each of the categories that NASA had outlined. Next came General Dynamics and North American Aviation, tied for second with 6.6 points; the GE-led and McDonnell-led contractor coalitions were the also-rans.

Despite the win Martin lost the contract to North American on November 28, 1961; NAA would go on to build the actual Apollo CSM. NASA administrator James Webb and his deputy Robert Seamans justified their decision on the basis of an external factor: NAA’s experience building the X-15.

The real reason is widely believed to be that North American had made the conscious decision to stick as closely as possible to Max Faget’s post-synthesis Langley design, and that NASA wanted that regardless of the merits of any other approach. Faget reportedly had been annoyed by the fact that none of the three initial designs had gone for a blunt-body re-entry vehicle, which was why he had come up with the Langley design in the first place and then convinced the agency to re-open the competition. He then had enough influence to disqualify any bid that didn’t follow his lead, including the Martin 410.

From this point onwards (and most noticeably in the proposals for the Space Shuttle a decade later, excepting the oddball SERV) NASA contractors understood that the implicit rule in any spacecraft design competition was “What Max Faget wants, Max Faget gets”. Despite the obvious possibilities for disaster with this approach giving him a veto turned out to be a pretty good idea: history has proven Maxime Faget was a talented spacecraft designer, arguably the best ever.

What was necessary for it to succeed: Not an awful lot more than what actually happened—the M-410 is one of the likeliest “what-ifs?” of the Apollo program.  It won the Apollo design competition, and if a small number of people (Faget, Webb, and Seamans) hadn’t been able to shift the results arbitrarily, it would have gone ahead. There would have been changes made, as happened in the real world to NAA’s design between 1961 and the first completed Block II Apollo craft flown in October 1968, but otherwise this design could have gone to the Moon.