Orbiting Primate Spacecraft: The Cape Flying Monkeys (Apollo Applications Program, Part IV)


An unfortunately cluttered schematic diagram of the Orbiting Primate Spacecraft, which was studied in 1967 as a way of learning about the long-term effect of microgravity on living things prior to sending astronauts on long missions to space stations or other planets. Public domain image from Orbiting Experiment for Study of Extended Weightlessness, Volume I. Click for larger view.

What it was: A tentative plan to explore the long-term biological effects of free fall on primates before sending human beings into space for extended periods. It was in essence a tiny, automated space station inhabited solely by monkeys.

Details: By December 1967 the longest manned flights in space had still fallen far short of what would be necessary for long-term habitation of space stations, let alone trips to Mars or Venus. The record holder, Gemini 7, had lasted for 13 days and 18 hours and only three other missions had stayed in orbit even as long as four days.

Accordingly while there were hints that there were biological consequences to being in microgravity for extended periods of time their exact nature was a mystery. As part of one approach to solving the problem NASA’s Langley Research Center gave a contract to Northrop Corporation (and to Lockheed, which developed a similar alternative) to study ways of conducting automated and teleoperated animal experiments over a year-long period in orbit.

The result was an Apollo Applications Program proposal, the Orbiting Primate Spacecraft (OPS). The plan was to build a small pressurized compartment big enough for two rhesus monkeys and their perishable supplies, and attach it to an unpressurized section based on the LM&SS truss; this would carry life support equipment such as a water tank and a lithium hydroxide CO2 scrubber.


An Apollo CSM injecting the OPS into its higher orbit. The solar panels would actually only have been deployed once the station had been undocked from the main spacecraft. Image from Orbiting Experiment for Study Extended Weightlessness. Click for a larger view.

If the mission had gone ahead the OPS would have been put in the upper stage of a Saturn IB, in the spot normally reserved for the LEM. An Apollo CSM carrying either two or three astronauts would have been placed above it as per usual and then the rocket launched from Cape Canaveral. The upper stage, the OPS, and the CSM would end up in a 185 kilometer, 28.5° orbit, at which point the CSM would undock, turn around, and then re-dock nose-first with the exposed OPS—again, much like an LM would be treated. The CSM would then fire its engine and boost itself and its scientific payload to a more long-lasting 460 kilometer orbit where the OPS would be released and the astronauts could get on with the rest of their mission.

Inside it, the two monkeys would be in individual pods sealed off from the rest of the craft and each other, to prevent fighting, with a small opening for some social contact. This design prevented stray waste or food from gumming up the instruments during a year-long mission with no humans on board. Northrop decided to further solve the latter problem by by conditioning each monkey to respond to a food light flicking on by going to its feeder and placing its lips over its outlet—a pellet of their usual monkey chow would then be put into its mouth so that food wouldn’t fly off in zero-g. The proposal does discuss feeding them with pastes or other more tractable foods, but that approach was rejected over worries that the subjects would be sufficiently unhappy with the change from their usual Earth diet that it would affect the results of the experiments.

“Monkey waste” was noted as the much more difficult issue. Without gravity or a human to keep the life pods clean, Northrop had to spend considerable thought on their design and still felt their solution needed more work. One wall of the pod was made into an open wire grid (which not incidentally gave the monkeys a “floor” to hang on to if they wanted one) over a storage receptacle; a forced airflow would have been passed through the pod and pushing waste toward it whenever needed—the monkeys were to be under observation by television camera anyway. If something stuck, another wall was movable and Ground Control could command it to scrape the compartment.

The movable wall was primarily for another purpose, though: forcing the monkey into a recovery capsule attached to the bottom of the OPS once the mission was over. As the capsules could be sealed off from the rest of the spacecraft one could also have also been used to store and isolate a monkey that had died for whatever reason prior to the end of the mission.


The entire OPS wouldn’t have returned to Earth. Instead a second mission would have astronauts in a CSM retrieve two small lifepods containing the experimental monkeys. Image from Orbiting Experiment for Study of Extended Weightlessness.

Approximately one year after the Orbiting Primate Spacecraft was set floating on its own, a second Apollo CSM would be sent up to retrieve the its simian inhabitants. Once again the ship would dock nose-first with the station, and the monkeys (or the mortal remains of one or both of them) would be retrieved by a spacewalking astronaut. After a short capsule-enclosed spacewalk of their own the two subjects would be stowed aboard the CSM and returned to Earth, while the OPS would be deactivated and left in orbit. The monkeys would then provide a wealth of data to supplement what they had already given—the plan was to test them onboard using a lights panel they had been conditioned to obey prior to the mission, as well as possibly surgically attaching various wireless telemetry probes to them (though that technology was quite advanced for the time). One part of getting this data actually turned out to be the other major problem past monkey waste that Northrop couldn’t crack: how to weigh—or technically, mass—the monkeys in zero-gravity without a human on board to do it.

Though the Orbital Primate Spacecraft never made it past a fairly speculative stage, it was positioned quite clearly in NASA’s schedule as it existed in December 1967. Northrop examined the various Apollo missions that weren’t headed to the Moon (primarily Apollo astronaut training and the building and supplying of Skylab at its subsidiary stations as it was then conceived) and settled on Saturn/Apollo Applications flight 218, then scheduled for late 1970. Retrieval was more nebulously scheduled beyond the basic parameter of keeping the experiment running for six to twelve months, and was relegated to any one of the resupply missions SAA 221 to 228.


Northrop’s other suggested uses for an OPS module. Description of all of these take up less than a page, so it’s not clear how seriously these should be taken. Image from Orbiting Experiment for Study of Extended Weightlessness. Click for larger view.

While the Orbiting Primate Spacecraft weightlessness experiment was the primary mission described, Northrop also briefly described a few other possible uses for a variant OPS, such as mounting it on an LM landing stage and studying the biology of the rhesus monkeys under lunar conditions, or putting one at the far end of a tether attached to a (presumably unmanned) CSM acting as a counterweight for spinning up the arrangement and running artificial gravity experiments. They also somewhat bizarrely tout it as a possible habitation module extension for a spacecraft built around the Gemini B being developed for the Air Force’s Manned Orbiting Laboratory, and even joining two of them in sequence as an emergency shelter in orbit.

What happened to make it fail: The Apollo schedule was very much in flux by the time Northrop submitted their study to NASA in December 1967. The Apollo 1 fire in February of that year had suddenly made it that much harder to reach the goal of landing a man on the Moon by the end of 1969 and NASA refocused their efforts much to the detriment of anything that didn’t directly lead up to Apollo 11. The Apollo Applications Program suffered accordingly.

By the time the AAP got back on track, budget was a problem. Several AAP proposals were cancelled because there were no more Saturn Vs available no matter what money could be thrown at them, but this wasn’t one of them. Had the money been there, there wouldn’t have been much difficulty coming up with a Saturn IB, a CSM, and the OPS. But this project was going to have to wait until after Skylab no matter what, and considering that that didn’t get going until May 1973—five years after the flight date assumed for the proto-Skylab in the proposal—this mission would have flown during the absolute nadir of NASA funding. By then the Space Shuttle program was absorbing everything they had.

The author also has a suspicion that the mission never went very far because it lacked dignity—while intellectually the OPS is a reasonable experiment, it’s hard to not react to it emotionally as “monkeys in a can”. Shepherding a mission from conception to flight is a political process, and what ex-military man or sober scientist is going to champion it and expose himself to ridicule (unfair or not) when there are so many other impressive or even heroic space missions to choose from?

As it was, it never advanced beyond the Phase A stage, which is to say simply determining how the mission would work in general and not serious design work, and NASA settled on getting their biological data by gradually extending the length of human missions. Skylab 2 lasted 28 days; Skylab 3 lasted 59. The longest American stay in space to date is still only 215 days (Michael López-Alegría, on ISS in 2006-2007), while only two human beings (Valeri Polyakov and Sergei Avdeyev) have exceeded the year that this experiment would have lasted.

What was necessary for it to succeed: The Apollo 1 fire was obviously a major problem, but simply eliminating it probably doesn’t help—it was a symptom of a wider problem at NASA and something else would have come along to disrupt the AAP schedule (and delay the OPS) instead.

The best bet would have been some greater commitment to space stations in the 1970s than NASA actually had. After Skylab the American record for consecutive time in space languished for a very long time until the ISS was up and running. Under those circumstances there was no need to push forward long-term microgravity knowledge. By the time it became necessary, the US even had some access to Russian data, as the USSR had had several long manned missions to the Salyut stations and Mir and the two countries were co-operating to an extent after the end of the Cold War.

Having the US follow the same path as the Soviets wouldn’t have been too hard. The Integrated Program Plan of 1969-70 had several components and the Space Shuttle and a space station were the two likeliest to go forward once it became clear that the entire IPP was a political impossibility. NASA chose the Shuttle, but that was a somewhat surprising decision at the time. Get them to pick a station as their primary goal instead and suddenly the Orbiting Primate Spacecraft starts to look a lot more attractive.

Apollo LM&SS: Mapping the Moon and the Earth (Apollo Applications Program, Part III)


The later design of the LS&MM. Unlike the earlier, larger module based on the KH-7 satellite, this one’s mapping module (right) was designed by Martin Marietta. As well as the crew compartment shown, an open truss containing the mapping cameras and sensors would be attached where the “End Airlock S016″ can be seen—retrieving the film from the cameras would require depressurizing the compartment and a suited astronaut reaching into space to get it. The section on the left is the usual Apollo CM. Public domain image from NASA document Technical Data AAP Mission 1A 60-Day Study. Click for a larger view.

What it was:  A tiny space station consisting of a photo reconnaissance module docked with an Apollo CSM in place of a regular LM. In return for being unable to land on the Moon, the LM&SS would become the first lunar-orbit space station, its mission to take high-quality photographs as the CSM was orbiting, and do it in a variety ways such as in regular light or infrared. It was originally targeted at the Moon, at first to survey Apollo landing sites and later for a more comprehensive scientific mapping mission. After cancellation and rebirth it turned into an Earth observation mission, partly for scientific study of the globe and partly to test the equipment for what had become a more hypothetical mid-to-distant-future Apollo lunar mapping mission.

Details: One of NASA’s earliest goals was to survey the Moon; there’s not much point in sending out a manned Moon lander if you don’t even know where they can put down safely. This goal was met by five very successful unmanned probes, Lunar Orbiter 1 through Lunar Orbiter 5, launched between August 1966 and August 1967. The first three of these specifically surveyed potential Apollo landing sites, while Lunar Orbiter 4 mapped almost the entire near side and Lunar Orbiter 5 almost the entire far side. Altogether they covered 99% of the Moon’s surface, and the last of the probes even photographed some of the surface down to a 2-meter resolution.

Before they were launched, though, NASA was worried that they might not accomplish what they were built to do—and rightfully so: the Lunar Orbiter’s predecessor, the Ranger program, had become a laughing stock after the first six attempts to get a probe to the Moon had failed. Even though the Rangers had the comparatively simpler goal of crash-landing (and photographing the impact region on the way down), from August 1961 to January 1964 they had done nothing but produce a sorry list of launch failures, camera failures, and outright misses of a target 3475 kilometers in diameter. Ranger 7 finally pulled off the trick on July 28, 1964, smacking into the Moon 69 kilometers from the eventual Apollo 11 landing site on the Sea of Tranquility, but NASA was still nervous about getting the quantity and quality of images they would need to keep an LM from accidentally landing on a boulder or on a steep slope.

So while they pinned their hopes on the Lunar Orbiter program, they also developed a backup plan they could use if they needed it: the Apollo Lunar Mapping and Survey System (LM&SS). At the time the new National Reconnaissance Office, after several years of teething problems themselves, had been building and flying the KH-7 spy satellite successfully since 1963. In the same year the Department of Defense, NASA, and the NRO agreed to share their technology and Kodak, Lockheed, and General Electric were contracted to build a variant of the KH-7 which had its station-keeping engines and film re-entry vehicle deleted but a small docking port added. So modified, one could be lofted into orbit in the part of a Saturn V that would normally house an LM.


The camera of a KH-7 satellite, and so a close analog of the original LM&SS. The re-entry vehicle for the film (left) would have been removed and replaced with a docking adapter. Public domain image from the NRO. Click for a larger view.

As with the regular Apollo missions, this one would have been sent on its way to the Moon by the upper stage of the Saturn V and then a short way into that journey the CSM would have undocked, moved away a short distance, rotated 180°, and then returned to dock nose-first—the difference being that it would be docking with the LM&SS, not a more-usual LM.

Upon arrival at the Moon, the LM&SS (which was also the name used for the entire craft) would enter a polar orbit, slicing the Moon up photographically as it rotated beneath. The entire mission would take 35 days, 28 of them in lunar orbit so that the Moon could make one complete turn on its axis and the LM&SS cover the entire surface; this would have required a change to the CSM’s life support systems so it could handle a journey that long.

The film in the camera would be retrieved periodically and then once all the photographs were taken the LM&SS would have been ejected to crash into the Moon (as it would do sooner rather than later because of the way lunar mascons wreak havoc on stable lunar orbits) and the CSM would return to Earth following the usual Apollo mission profile.

This variant KH-7 would have been about five meters long and enclosed entirely in a near-featureless cylinder about a meter and a half in diameter. When docked to the CSM it would have looked, appropriately enough, as if the CSM was sporting an enormous telephoto lens on its nose.

By 1967 an internal battle at NASA between those who felt that the Lunar Orbiter survey was sufficient and those who wanted the higher-resolution LM&SS pictures ended with the former in the ascendant. Four LM&SS modules were at various stages of completion by then, but this particular version of the lunar mapping mission was cancelled.

Among the factors contributing to this was the fact that the mission would have needed a precious Saturn V launch just at the time when NASA were discovering that Congress wouldn’t pay for as many of those rockets as they would have liked. That explains in part the second variant of the LM&SS program, the Apollo Applications Program launch that was designated AAP-1A.

As the name suggests, this would have been an early Apollo Applications Program mission—the third, confusingly enough, after AAP-1 and AAP-2 which would have launched the proto-Skylab Orbital Workshop space station and its first crew. AAP-1A would have originally brought the LM&SS equipment to the OWS, but after the OWS’ mission planners became concerned that the first crew already had too much to do they decided not to go ahead with installing the LM&SS on the station. AAP-1A became a standalone mission more like the LM&SS’ original conception: a CSM and the LM&SS docked to one another to make a miniature space station of its own.

Whether attached to the OWS or the LM&SS, AAP-1A’s goal was Earth observation, but also to put the LM&SS through its paces for a nebulously planned Lunar observation mission that would get back on the schedule as a pure science mission sometime in the future. The basic problem this mission looked to address was interpreting the photographs of that hypothetical lunar mission. Observation missions during wartime had shown that it was actually quite hard to figure out what an aerial photo was trying to tell you if the enemy wasn’t about to let you look at what you were photographing with a later visit on the ground. With the Moon there was no enemy other than distance and cost, but establishing the “ground truth” was equally difficult. It was entirely possible that the LM&SS photos would be misinterpreted in critical ways because there was no way to cross-check those interpretations.

So somebody came up with the idea of launching the LM&SS on top of a Saturn IB. It couldn’t go to the Moon that way, but it could stay in Earth orbit and image parts of the United States that could be reached easily. Follow-up field trips on the ground would then go and look at what was imaged and learn how what was on film compared with the view on terra firma.

Somewhere along the way (and for reasons we’ll examine shortly) NASA decided not to use the full KH-7 module. Instead they commissioned Martin Marietta to develop a stripped-down version consisting of a small manned module with a small airlock to the film compartment; the astronaut using it would have to suit up, depressurize the LM&SS manned compartment, and then reach out through the lock into space to retrieve the reels. In return for the smaller size of the main camera arrangement, it was now possible to add a large suite of other sensors and cameras to the LM&SS as well as a few unrelated experiments. Martin Marietta designed an open tetrahedral truss made of aluminum, and wrapped it around the module to support the instruments. The module in turn was then docked to the CSM. While the truss-supported instruments were open to space and so generally intended to be self-sustaining, the LM&SS did have a second man-sized airlock so that an astronaut could go on a spacewalk to fix or retrieve one.

AAP-1A was planned out quite thoroughly and aimed to launch in either late 1968 or early 1969, just prior to Apollo 11 and as the Earth-orbiting mainstream CSM/LM tests Apollo 7 and 9 were underway.

What happened to make it fail: The Lunar Orbiter program was a roaring success: five out of five launches did what they were supposed to do, in contrast with the poor, benighted Rangers. The complementary Surveyor probes worked well too: seven landers and seven landings, though two did crash rather than coming down softly as designed. Apollo 12 even visited Surveyor 3 thirty-one months after it had proved its target to be a suitable landing site. Even so, as mentioned previously some NASA personnel thought that the Lunar Orbiter photos weren’t enough, and that something higher resolution would be needed. Nevertheless, the consensus emerged that what they’d got from the Orbiters was good enough, and that the LM&SS didn’t need to fly.

What may have tipped the balance that way was another pressure on the LM&SS mission. For many years it was believed that the LM&SS module was a modified LM, not a KH-7; only a little information about the program leaked out from industry insiders. Why? The KH-7 may have been obsolete (it was being replaced with the KH-8 just as NASA starting working on theirs), but it was still classified and it stayed classified until September 2011. While the NRO as a whole was willing to supply NASA with the equipment they needed, they  were nervous about even officially disclosing the existence of American spy satellites. If Apollo had absolutely needed it, they were would go along with putting one of their birds in the halogen-lamp glare of the Space Race in the hopes that no-one would look at it too closely and believe the cover story that it was a piece of NASA equipment.

So the first iteration LM&SS was cancelled because of the clandestine nature of the equipment they would have had to use. The radically less-open culture of the NRO that was supplying that equipment made it certain that it wouldn’t move forward once the primary goal of protecting the astronauts (or, more to the point, preventing American propaganda disaster) could reasonably have been said to be reached.

This is what morphed the LM&SS module into its new shape. Even though it was using the same camera, the module was heavily redesigned so as to make it less obvious where the camera came from. Even then the NRO was also apparently unhappy even to reveal that the US had the capability to image the Earth at high resolution, as would become obvious once AAP-1A’s photos were made available to the public; a document declassified in December 2011 named presidential science advisor Donald Hornig as the higher-up who pushed the issue. With their budget shrinking quickly NASA probably would have cancelled AAP-1A anyway, but certainly the concerns of the NRO were another straw on that particular camel’s back

What was necessary for it to succeed: Each of the variants of the LM&SS program failed for different reasons, so let’s take them in order.

For the initial one, using the KH7 to examine the Moon for Apollo sites, there’s the obvious possibility that Orbiters would have proven to be a second run of the Rangers. Alternatively, the faction of NASA that felt the images from the Orbiters still weren’t good enough and that the LM&SS module should fly might have come out on top. Having a rocket they could have used would have helped there. While the Saturn V wasn’t formally put aside until 1968, NASA had to have seen the writing on the wall, as they had been requesting funding for the sixteenth and seventeenth Saturns since 1966, and never could get it. If one or more of those had come through, the Lunar mapping program would have been right near the top of the list to be perched on one.


Apollo 15’s Endeavor with its scientific instrument bay open, photographing the Moon. Its camera was located at to the right of the white rectangle that can be seen near the centre of the bay. Public domain image from NASA.

The second proposal for lunar mapping, the scientifically oriented one that was to follow at an indeterminate point after the Earth Sciences test, fell by the wayside with the decision to do lunar mapping from CSMs of the regular Apollo missions. People often don’t realize that while two astronauts from each Apollo did their work down on the lunar surface, the third astronaut wasn’t idle while in orbit in the CSM above. Among the things he’d do while circling the Moon, at least during the J-class Apollo 15, 16, and 17, was photograph it using a 24-inch panoramic camera based on those used by the KH-7’s predecessors in the CORONA spy satellite program.

The difference that made flying one of those easier than an using an entire LM&SS was the nature of the camera. It wasn’t very hard to cover it up as a bespoke piece of equipment made for NASA, since in essence that was what it was, and its presence wasn’t as obvious because it was small enough that it could be stuck in the section of the Service Module (the SM being subdivided internally into six radial compartments) that was reserved for scientific equipment. Contrast that with the KH-7 module, which was obviously a piece of surveillance equipment, and one that massed 2000 kilograms and had to be docked to the front end of a CSM for the lack of anyplace else it would fit. There was no hiding that. The CORONA cameras may not have been as capable, but they were a lot more politically palatable. NASA’s willingness to take the CORONA cameras as “good enough” would have had to change before they would have pushed back against the NRO and tried for the full KH-7 LM&SS on this mission.

The Earth Sciences version of the LM&SS fell to several nibbling problems. By 1969 NASA’s budget was shrinking rapidly, so being able to shrink down to a cheaper Saturn IB was now not good enough—it was no longer even clear that the money to build the extra CSM and then support the mission would be there. On top of this the NRO continued to have concerns about what the capability of the LS&MM’s cameras would reveal to the world about their spy satellites, and weren’t keen to waste that secrecy on something as trivial as better maps of the world’s resources.

Next, by the time AAP-1A was planned to go in mid-1969, it had become clear that unmanned satellites were close to being able to map the Earth to the same level of fidelity (and in fact would start doing so with Landsat 1, which launched in 1972). And finally, even NASA had to accept that “testing Moon mapping systems” was putting the cart before the horse; it was far from obvious that they were going back to the Moon at all once the main line of Apollo missions had ended, as of course they haven’t in the years since. So what was the point of that? As there were so many things running against it, this is the version of LM&SS that was least likely to ever fly.

As a final aside it’s worth mentioned that NASA once again has their hands on some high-quality spy satellite cameras. In June 2012, the NRO donated two surplus telescopes to them, with media reports saying that their main mirrors were comparable in size to that of the Hubble Space Telescope. While it’s still unclear at the time of this writing what they’re going to do with them, NASA is believed to be considering plans to use them in a replacement for that aging orbital observatory sometime after 2020.

MOLAB/MOLEM/MOCOM/MOCAN: The Eagle Gets Around (Apollo Applications Program, Part II)


The MOLAB, heading away from the astronauts’ LEM on a 14-day mission. As well as this purpose-built version of the rover shown here, NASA considered three other versions that re-used other equipment being built for Apollo. Image from Lunar Mobility Systems Comparison and Evolution Study (MOBEV): Final Presentation Report. Click for a larger view.

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 LEM, repurposed as the crew cabin for a MOLAB. Image from Lunar Surface Mobility System Comparison and Evolution (MOBEV): Final Report. Click for a larger view.

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.


An Apollo CM as the MOLAB. Image from same source as previous. Click for a larger view.

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.


A Boeing CAN — intended for a variety of uses on the lunar surface, but primarily a cargo container for the LM Truck — converted for use as a MOLAB. Image from same source as previous. Click for a larger view.

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 seating issue that took the LEM variant of the MOLAB out of the running. Image source same as previous. Click for a larger view.

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.

Manned Venus Flyby: Apollo’s Hail Mary Pass (Apollo Applications Program, Part I)

MVF Cutaway

A cutaway view of the Manned Venus Flyby spacecraft. Based on Apollo hardware, this remarkable proposal would have sent three astronauts on a year-long mission to Venus and back. Public domain image from the 1967 NASA document Manned Venus Flyby, via Wikimedia Commons. Click for a larger version.

What it was: A proposed post-Moon landing manned mission using Apollo hardware. It would have launched during a good alignment of Earth and Venus in November 1973 and taken three astronauts on a flyby of the planet Venus, returning to the Earth 13 months after launch.

A later variation of the mission ambitiously suggested using a better conjunction in 1977 to visit Venus and Mars on an outbound leg and Venus again on the Earth-return leg, however most of the work done considered the shorter Venus flyby.

Details: By the mid-1960s NASA was well aware that if they successfully completed the Apollo moon landings they would probably face a severe decline in budget for the manned space program. In the hopes of proving their ongoing worth they developed a few different post-Apollo proposals using evolutionary versions of the Apollo hardware, including plans for a manned lunar base, space stations, and planetary exploration. The latter two of these goals were at first grouped under the name Apollo X, and then became the Apollo Applications Program (AAP).

By far the most ambitious of the AAP missions was a manned flyby of the planet Venus. After two preliminary missions in Earth orbit to test the technology, a Saturn V launch would lift an Apollo Command Module into orbit. As in a typical mission, the first two stages of the rocket would be jettisoned. However the uppermost stage, the Saturn IVB, would be kept and drained of any remaining propellant. Using gear stored where the Lunar Landing Module would have been placed in a Moon mission, the astronauts would then rig it as a habitation module.

The resulting 33-meter-long spacecraft would leave Earth orbit on October 31, 1973 and travel towards Venus for 123 days. There would be a flyby on March 3, 1974. The craft would have been aimed to pass Venus as close as 6200 kilometers above the surface (one planet radius) very quickly—orbital mechanics would have it moving relative to Venus at a clip of 16,500 kilometers per hour—crossing the lit side of the planet. A sidescan radar would map the portion of the planet they could see as they flew by, and the astronauts would perform spectroscopic and photographic studies.

A series of probes was to be dropped by the spacecraft, and they were specifically enumerated in the proposal for the Triple Flyby variant of this mission that was mentioned earlier. Near closest approach the MVF would launch an orbiter and fourteen planetary probes; the probes would communicate with the orbiter, which would then beam the results back to Earth. Altogether the probes were:

  • Six atmospheric probes, which would enter the atmosphere at six locations: the planet’s solar and anti-solar points, its terminator and equator, and the middle of the light and dark sides. They would drop in ballistically and try to determine how Venus’ atmosphere increased in density the closer one got to the surface.
  • Four meteorological balloon probes. They would float in the atmosphere and try to learn how the Venusian atmosphere circulated as well as study smaller-scale winds.
  • Two “crash-landing” probes that would try to photograph the surface on the way down, much like Rangers 7, 8, and 9 did with the Moon.
  • Two soft-landers that would take surface photographs, examine the soil, and measure Venusian weather.

As well as acting as a communications hub, the orbiter would use X-band radar to map the planet.

MVF Mission Trajectory

The MVF’s trajectory. Detail from Manned Venus Flyby. Click for a larger view.

After that burst of activity the MVF craft would then return home, taking 273 days more to loop out to 1.24 AU from the Sun on a hyperbolic trajectory and eventually swing back to Earth. The astronauts’ landing on Earth would happen on December 1, 1974—total mission time would be 396 days. The Triple Flyby variant would have taken more than 800 days starting in 1977.

When not at Venus, the MVF astronauts would have studied the Sun and solar wind as well as making observations of Mercury, which would be only 0.3 AU away two weeks after the Venus flyby. To keep them occupied otherwise their habitation capsule would have been outfitted with a small movie screen (to show 2 kilograms of movies allowed), and a “viscous damper exercycle/g-conditioner”. The crew would also be allowed 1.5 kilograms of recorded music, 1 kilogram of games, and 9 kilograms of reading material. Hopefully they would choose wisely.

What happened to make it fail: The MVF was part of the Apollo Applications Program, and the AAP was killed dead on August 16, 1968 when the House of Representatives voted to cut its funding from US$455 million to US$122 million. President Johnson accepted this as part of a larger budget deal that kept NASA’s near-term goals safe, though even at that the agency’s entire budget dropped by 18% between 1968 and 1969. The only AAP mission to survive was Skylab.

What was necessary for it to succeed: It’s tough to get this one to work as it’s difficult to see any advantage to sending people on this mission. Mariner 5 had already flown by Venus in 1967 and NASA was able to send a robotic orbiter as part of the Pioneer 12 mission in 1978, just a few years after MVF would have flown.

Even the many probes that the MVF would leave behind at Venus had no obvious connection to the manned part of the mission; it would have been easier to send an unmanned bus of similar size and drop the probes that way. There would be no need then for heavy food, water, or air, or the space for people to move around. And unlike the manned mission there would be no need to bring the bus back, greatly reducing the mission’s difficulty. About all the manned mission had going for it was an opportunity to see what kind of effect a year in microgravity would have on humans, and that could just as easily be determined using a space station in low Earth orbit.

On that basis we also need to be aware that Congress asked hard questions about the purpose of NASA’s manned Mars mission plans in the late 1960s and were hostile to all of them. If Mars wasn’t going to get any money, it’s hard to see what could influence them to fund a mission to Venus.

Finally it needs to be pointed out that no matter even if the MVF launched, nature itself probably had this mission’s number. We didn’t have a very good understanding of the Sun at that time, having only observed one solar cycle from above the atmosphere when the flyby was proposed in 1967. While the launch window was deliberately chosen to be near a solar minimum, and the flyby craft was to have a radiation lifeboat in the equipment module, the mission would have run into an unforeseen natural event on the way back to Earth.

On July 5-6, 1974 the Earth was hit by a big coronal mass ejection (CME), a storm of electrons and protons thrown off of the Sun. People down on Earth were protected by the planet’s magnetic field, as usual, but the astronauts coming back from Venus wouldn’t have been so lucky. Their line to the Sun was several degrees off from the Earth’s (at the time they would have actually looped out past Earth as their trajectory slowly took them back home), but CMEs can cover quite a bit of space. Had the mission actually flown, the astronauts on-board may well have died of radiation sickness after being hit with more (and more energetic) solar protons than their spacecraft was built to handle.

The saving grace here is that coronal mass ejections were discovered in 1971, so the initial plan probably would have been called off rather than risk casualties, or at least be reconfigured to give the astronauts the protection the 1967 plan failed to give them.

An interesting simulation (using the program Orbiter) of how the MVF mission would have run can be seen on YouTube.