What it was: Four proposals to deal with the same issue: once the lunar lander touched down, it was stuck there and its crew had to suit up and walk to anywhere they wanted to study. As the Apollo lunar base was getting up and running, one of these four ideas would be used to give astronauts a mobile laboratory with a “shirtsleeve” environment in which they could trundle around the surface of the Moon on jaunts to various interesting locations.
Details: We’ve previously discussed one suggestion for using Apollo hardware beyond its base purpose of getting people to the Moon and bringing them back. The Manned Venus Flyby was by far the most extreme option considered, but there were many other possibilities: NASA and its contractors put a lot of work into figuring out what else the various bits of Apollo hardware (with modification) could do.
The MOLAB was, as its name suggests, a mobile laboratory. The first Apollo missions relied entirely on legwork for getting around, and while Apollos 15 through 17 had the benefit of the lunar rover (LRV), it was far from perfect. If nothing else, mission duration was restricted by the fact that it had no life support—its passengers relied on their spacesuits for air and the like, and so missions could be no more than a few hours long.
Before budget pressures forced NASA to cut back to one Saturn V per mission, the plan was to support extended Apollo missions by sending a second lander (the LM Truck) carrying support equipment. Accordingly NASA was generous with weight—potentially up to 3860 kilograms was allowed—and came up with a plan for an entirely new piece of equipment, the MOLAB proper. After delivery to the Moon it would then be offloaded from the truck, set up, and then boarded by the astronauts and used while their LEM was put into hibernation. But aware of the eye of Congress on them even before the budget cuts started to hit, though, they also asked Bendix Corporation (builders of scientific packages for Apollo, and a company that had been studying lunar rovers and fliers for NASA since 1961) to look at three other possibilities for enclosed vehicles that the Truck could bring.
The first was the MOLEM. The basic idea here was that the Lunar Excursion Module (LEM) was primarily designed to give astronauts someplace to live while on the surface of the Moon, so why not just keep going with that idea? Though some redesign would be necessary even beyond the deletion of its ascent rocket and the addition of wheels, it would be cheaper than starting from scratch with a full MOLAB.
Carrying a crew of two, the MOLEM would have been able to drive for 400 kilometers and go up a 35° incline. This meant it would be going around craters and other rough terrain rather than over it, so Bendix felt this translated to an 80 kilometer radius for missions. With a roaring top speed of 16.7 kilometers per hour these travels could be spread out across two weeks, with another week in emergency supplies if they were needed. The air inside was to have been 100% oxygen at 0.34 atmospheres, a choice that at first places the Bendix report prior to the Apollo 1 fire (and it is, having been completed in November 1966) until one realizes that the real-world lunar modules used pure oxygen as well. It’s hard not to think that, given the extra payload capability supplied by the LM Truck, this would nevertheless have changed if any of the MOLABs had gone ahead.
Altogether the MOLEM would have rung in at 3516 kilograms, which was a point in its favour. Not only could the LM Truck carry it, there was even leftover room for other equipment.
The next option was the MOCOM. This was a less-obvious possibility, being an Apollo Command Module (CM) with wheels attached. Unlike the LEM this piece of equipment was never designed to go anywhere other than orbit, but the thinking was it was also designed to support its own weight while on Earth, so in all it should be able to handle the lunar environment. The lack of air on the surface was the same as conditions in orbit, and the Moon’s 0.16 gravities would be a snap compared to Earth’s hefty pull.
This CM’s heat shield would be scrapped as useless, as would the various bits of instrumentation and attitude control rockets needed for flight. As the regular CM hatch proved to be badly placed for a lunar vehicle, an airlock would be added along with the wheels, drive train, and transmission. As it would use essentially the same powertrain as the MOLEM, it would have the same duration and trip length, while also carrying the same amount of cargo (320 kilograms). The major difference between the two would be in the amount of space the astronauts would have to move around in during their excursion: the MOLEM was smaller at 4.2 cubic meters in volume (compared to the MOCOM’s 6.2 cubic meters), and had less floor space (2.4 square meters as opposed to 4.1)—which meant that the MOLEM wouldn’t let the astronauts sit down while driving. Finally, while the MOCOM was slightly heavier at 3743 kilograms, it too would fit on the LM Truck.
The final possibility was to use a CAN, a proposed piece of hardware—the Multipurpose Mission Module—from Boeing. Unlike the LEM and CM this wasn’t already developed when the Bendix report dropped, but it was considered a strong contender for a variety of uses in the future Apollo lunar base. As the base was still a going concern at the end of 1966, NASA clearly felt that it would be worth seeing what good a CAN could serve as a MOLAB if they were already going to be building them anyway. The CAN was specifically designed to be as large as something could be while still fitting on top of the LM Truck, which meant that it was considerably more roomy—38.2 cubic meters and 7.9 square meters of floor—than the LEM and the CM: a major plus if you’re planning on sticking two people in it for two weeks, and a size that even allowed a crew of up to four. Unfortunately, as it was already as big as what the LM Truck was supposed to handle, and didn’t really have anything that could be stripped out, it rang in at 4326 kilograms if given the same capabilities as the other two vehicles. To get it down to fighting weight it had to be reduced to 200 kilometers of travel and eight days of life support (not counting the emergency extension supplies).
All this can be compared to the real MOLAB. It, again, had the same basic trip characteristics as the MOLEM and MOCOM, but being specifically designed for its purpose was able to do so with the lowest weight of all, 3221 kilograms, and so had the associated advantage of letting the LM Truck carrying other things besides just it. It also had more interior space than anything except a CAN, at 7.7 cubic meters.
The final decision of the Bendix report was that the need to make the driver stand while using the MOLEM took it out of the running, while the MOCAN’s restricted duration and range did the same for it. The MOCOM was “just right” but at the cost of being slightly less comfortable for the astronauts while also using up over 500 kilograms more of the LM Truck’s payload capacity. At that point they then threw the problem back at NASA, essentially telling them to pick based on what was more important to them: saving money by re-using a CM, or maybe not having a useful piece of equipment on the Moon because of those 500 wasted kilograms.
What happened to make it fail: Like much of Apollo, even the last few planned missions up to Apollo 20, budget cuts prevented any version of the MOLAB from reaching the Moon.
The Apollo Lunar Base was cancelled outright in 1968, but MOLAB’s death came about more particularly because of the cancellation of the Saturn V past the original production run of 15 rockets. MOLAB depended entirely on the LM Truck, and the LM Truck depended on there being two Saturn V’s available for each mission—one to launch the astronauts as per the usual Apollo mission, and one to launch the Truck with the cargo the astronauts would be using. Once that became impossible, any rover weighing 3800 kilograms was a no go. The actual lunar rovers that were sent to the Moon could be loaded up with the astronauts’ LEM, as they massed a mere 210 kilograms.
What was necessary for it to succeed: The best bet might have been for someone other than Thomas Paine to follow James Webb as NASA administrator in 1969 (or for the Democrat Webb to carry on somehow even as the White House changed from Johnson to Nixon). Paine was very much committed to a technically feasible but politically impossible agenda for NASA based on advancing the state of space technology and moving on to Mars. Someone more realistic might have committed to the Apollo Application Program’s goal of sticking with Apollo-era hardware and improving it incrementally as technology got better over time—an approach quite similar to what the USSR and Russia have done with Soyuz and the R-7 rocket family down to the present day, though to be fair they’ve never had to maintain a lunar launch capability. It may have taken a lot longer than they thought it would in 1966, but something similar to the MOLAB might have hit the lunar dust eventually.
The sticking point here was the Saturn V. It was already shut down in August 1968, with NASA just living on the ones already built until 1973, and the ability to get the production lines running again disappeared over the next few years. Knowledge of the Saturn V’s powerful F-1 engine lasted longer and might have been used for something similar to a Saturn V (without necessarily being a Saturn V) for a few more years after that, but ultimately the clock was ticking just as NASA’s budget was reaching its nadir in the mid-1970s.