What it was: The culmination of the US Army’s Project Horizon proposal of 1959: sending a direct descent/ascent spaceship to the Moon, then building and populating a twelve-man Moon base shortly thereafter.
Details: Having taken off from Christmas Island Launch Facility in the Pacific aboard a Saturn I to the Minimum Orbital Station (MOS), two Army astronauts would receive further fuel launches and then finally an unloaded Moon craft perched on top of a Saturn with a specialized third stage. The third stage has already burned through its fuel to get the heavy direct descent ship into orbit, so after matching orbits with the MOS the Moon crew and the other men living longer-term on the station refuel it. Then the two men bound for points further afield climb aboard and use the stage to burn for their trans-lunar trip.
As well as the TLI stage, the proposed Horizon lunar craft consisted of two more stages. One soft-landed the spaceship on the Moon, and the other would detach from that one (leaving it behind) and return its astronauts to Earth directly. It in turn would separate from a crew return capsule used for re-entry into the atmosphere and splashdown into the ocean. Altogether this two-stage vehicle would have been some 16 meters long and weighed 64 tonnes. This is huge: the Apollo CSM/LM combination was 45 tonnes, and even at that carried three men instead of two. Even a Saturn V (which was still in its early development during the times of Project Horizon, and is only roughly spec’ed out as a “Saturn II” here) wouldn’t be able to lift that off of Earth, and so the need for refueling in orbit.
To make up for this, there were actually two different types of landers suggested, one of which could be launched directly from Christmas Island on a Saturn I. To meet that requirement, this second type would have been relatively small: 12 tonnes with a payload to the Moon of 2.5 tonnes, a figure made possible only by the fact that they didn’t have to return to the Earth. One would be sent before the first two astronauts started on their journey to the Moon, carrying construction materials for the base. By the end of 1966, there would be four in all sent on their way.
The first manned lunar landing, of two men, would be in April 1965, guided into the site where the base is to be built. In the 1959 report, the Army even had three possible sites picked out: “the northern part of Sinus Aestuum, near Eratosthenes, in the southern part of Sinus Aestuum near the Sinus Medii, and on the southwest coast of the Mare Imbrium, just north of the Appennies”; the last of these is actually not far from where Apollo 15 landed. The Army astronauts’ job would be to explore the immediate area and make sure that the site was acceptable for building a base. They would live in their landing craft until the construction crew arrived in July 1965 (ninety days or so, as compared to Apollo 11’s 21 hours and 34 minutes) at which point they would head home.
This construction crew would consist of nine men, and they would get to work using explosives and tools to dig a deep trench in which they would build their own quarters within fifteen days (or at least no more than thirty) and then cover them with lunar material for protection; a ramp at either end would allow entry and exit from their quarters’ airlock. These accomodations would necessarily be Spartan, but when done the crew would have a small underground base with a cylindrical cross-section (double-walled with vacuum between for insulation), while leftover cargo pods and the like would be buried nearby to hold LOX/nitrogen tanks and waste. The crew would also set up two nuclear reactors to power the base and erect communications equipment so they could stay in permanent contact with Earth.
Now enhanced to twelve men by another landing, the construction crew would get down to building a second, larger cylindrical section at a right angle to the first. When completed the living quarters would be moved here, and it would also contain an office and a sickbay. The original cylinder would be fitted out as two labs, one for biological studies (the proposal charmingly suggests it could be used to check for life on the Moon) and one for physical experiments. The sections of the base wouldn’t link up, but the ramps on one end of each would touch for relatively easy access between them, or as easy as having to put a spacesuit on to walk a few feet can be. A diagram of a remarkably odd-looking spacesuit is included for reference in the report; it has mechanical hands (the astronauts’ real hands were to be cocooned inside the sleeves), and large plates attached to his feet to support him if the lunar dust turned out to be thick.
By the end of 1968 there would have been ten manned missions in all to the Moon, and eight returns, meaning that the Horizon base would still be inhabited into the indefinite future after that.
What happened to make it fail: The first part of Horizon that we discussed, the launch facility, was perfectly well laid out and not overly different from what ended up being built at Cape Canaveral (though it was bigger and had more pads). The second part is more speculative and is fairly different from what actually happened, but this is mostly because of the change to a Lunar Orbit Rendezvous mission by NASA a couple of years after Horizon was proposed. Still, in retrospect it looks as if they didn’t quite think their station through.
When we get to this third part, though, the speculative nature of what the Army wants to do is front and center. The ways they propose to build and maintain a Moon base are bizarre to modern eyes, mostly because they literally didn’t know the extent of the problems they would face. A close read of the relevant documents reveals a large number of weasel words embedded in every attempt to describe the way things would be done on the Moon if Horizon got the go-ahead. Even Horizon’s summary report admits that the Army wanted another eight months and US$5.4 million dollars just to nail things down before moving on to starting the hardware development for the program.
Having a Moon base was a possible ultimate goal for an American space program, but planning one down to the point of having dates and proposed sites was very premature. Ultimately Project Horizon didn’t fool enough people into thinking that the Army knew what they were doing. Even looking past the previously-discussed antipathy that President Eisenhower had for the military in space, he was known to have used the words “Buck Rogers” more than once to describe the nebulous plans he got from the Army and others, and he was justified in saying so.
What was necessary for it to succeed: The Project Horizon proposal wasn’t actually about how to get to the Moon. It was an attempt by the US Army to establish precedence over the other armed services and, later, the upstart NASA. With Horizon filed away in various Washington bureaucracies, they could point at their long-standing work on manned space travel and plausibly say “Why give money to these newcomers? They’d be starting from scratch and you’d have to pay for that! Give it to us; it’s the wise course to take”.
Then, if anybody bought what they were selling, the way they actually went about it would conform to Horizon only incidentally as they got around to determining how to build this part of their empire. They could always go back and get more money and more time if they needed it, once the US committed to doing it through them.
So Horizon Base was never going to get built. It’s not an appropriate way for housing 12 men on the Moon because when it was designed the proper ways to do it were literally unknown, and would remain unknown for some time. But all it needed to succeed at its actual goal was to fend off Eisenhower long enough for someone in Congress to step up for them and ram through a bill giving the Army control of manned space exploration. It was a decent bet, just one that didn’t pay off.