Moonlab IV sat on the launch pad in Florida longer than originally planned. The second supply mission was slated for a late May launch in 1975, but technical delays and a serious threat of a leak in the Saturn Vb booster delayed the launch until June 20, 1975. None of the Saturn V family of rockets had ever exploded, and NASA intended to keep that perfect record. If one were to explode after launch, Moonlab might see a premature ending, and if even one were to explode on the ground, it would bring the American manned space program to a halt.No leaks were found and it was later decided that a faulty sensor was to blame after all the other Saturn Vb boosters underwent inspection. Further tests on sensors bumped the entire project schedule back a month, forcing Moonlab V to wait until August.
The Moonlab IV supply LM made a perfect landing, almost exactly 1.6 kilometers (one mile) north of the HM. On board were enough supplies to last nine months. With the success of Moonlab III, mission planners debated expanding the original mission length of six months. Moonlab V’s mission was stretched to eight months, and after the delay of Moonlab IV would run from August 1975 to March 1976. There was some concern over the extended length voiced by NASA doctors. It was not a matter of if the crew could handle eight months on the moon but rather the running health of one crewman in particular.
Before his scheduled flight in the Mercury Program, Donald “Deke” Slayton was struck from active duty due to an irregular heartbeat. It was a condition he lived with his whole life and one that never affected his performance during WWII or as a test pilot. It also would have played no role in his scheduled mission, but NASA doctors worried over every irregularity and the NASA’s management feared a public relations disaster if they lost an astronaut in orbit. At the time, no doctor could say for absolute certain that weightlessness would not aggravate his condition, and that non-zero probability grounded Slayton.
In 1972, after years of lobbying NASA physicians and long periods between fibulations, Slayton was finally cleared for flight. The only flights planned for the remained of the decade were the Moonlab missions, and the doctors soon tried to backslide one their assessment when it became clear that Slayton would be going to the moon. They worried enough about astronaut health when they were in Houston. The issue was finally settled by management, when Krantz, Christopher Craft and NASA administrator James Fletcher stood by the original assessment; Slayton was go for Moonlab. However, they were forced to grant the doctors an emergence veto. In the event they came to a consensus that Slayton’s health was in ‘serious jeopardy’, then the mission would abort and the crew would return to Earth. At age 51, Deke Slayton earned the distinction of being the oldest rookie astronaut.
Moonlab V’s mission commander was another veteran of Apollo, though he never actually touched the surface. Thomas Stafford flew on Gemini III and XI, as well as commanded Apollo X, the mission that tested the LM in lunar orbit. He and Gene Cernan flew within 47,000 feet of the lunar surface. The ascent module of the LM lacked sufficient fuel to return from the surface. Officially it was to reduce weight for the launch, though it has been suggested it was insurance to prevent Stafford and Cernan from leaping ahead of Apollo XI. One can only imagine the frustration caused by being so close, yet never able to reach the goal line. On Moonlab V, Stafford would finally reach that line.
Mission Specialists for Moonlab V would be astrophysicist Edward Gibson, and his mission would be astronomical observations from the surface of the moon, as well as physics experiments conducted in the lunar environment. Unfortunately for Gibson, mission planners failed to take into account that a full Earth was far brighter than a full moon, rendering a good portion of the lunar night useless for observation. Instead, he turned his instruments on Earth during that period, studying the homeworld from afar. One photograph taken during the mission was almost as famous as Earthrise. The picture was of a half-Earth; one side blue and white, the other black except for a scattering of lights. The picture showed a detailed layout of cities in the western United States and Canada during the Terran night.
Moonlab V launched on August 12, 1975, after a brief delay caused by a faulty sensor in mission control. Slayton later voiced his annoyance on how a faulty indicator a thousand miles away nearly scrubbed his mission. If not for the quick work of technicians in discovering the fault was in the sensors and not the Saturn Vb, the mission might have faced a severe setback. A few hours later than originally planned, Moonlab V was off the ground and headed towards the moon. The crew touched down less than a kilometer from the Habitat Module on August 15. It was closer to the HM than mission planners liked, but not close enough that debris kicked up by the descent engine, or the engine itself, would cause damage to their living quarters.
The new crew began their stay by inspecting experiments left running by Moonlab III. The small garden within the HM, which consisted a grand total of four pots, gave promising results for a future of growing plants in a lunar base with local resources. A small tomato plant left behind survived the long day-night cycle and bloomed with several flowers. One problem the astronauts would be unable to solve was how exactly they were supposed to pollinate what was grown on the moon. There was no way NASA would allow honeybees to be kept in Moonlab. Biologists were not even certain bees could function properly on a world with no magnetic field.
NASA did permit the transportation of several mice to the moon during Moonlab V. The purpose was not to have rodents take a toehold on another world, but rather a long-term study on how life could adapt to low gravity. The mice born on Earth were of the least amount of interest; it was how their offspring would develop in lunar gravity that could give clues on how humans could develop and grow from conception to death off Earth. Sooner or later, humanity would leave Earth and it was not feasible for every woman to return to Earth gravity for the duration of pregnancy.
Would the mice grow to giant size in the low gravity? It was a common belief at the time, but as it turned out the mice born in Moonlab were not much bigger than those immigrants from Earth. Diet played a bigger role in determining size. Autopsies on the lunar-born mice showed that bone development would be a great concern to colonists in the far future. Each lunar mouse’s skeleton grew slighter and more brittle than their robust Earth cousins. Attempts to return live mice born on the moon failed when these lunar mice were killed by the force of re-entry. Structural tests on the bones indicated mammals born on the moon could function in Earth’s gravity, though a gentler means of transitioning from a trans-Earth injection to splashdown would be required to prove the hypothesis for certain.
Protests over Moonlab picked up again just after New Years’ 1976. Moonlab VI, the third supply run, sat poised to launch from the Cape. Ordinarily, a supply mission would not garner such recognition by anybody outside of NASA. The public was hardly excited about the flight of water, oxygen and free-dried food. However, Moonlab VI was to be different. In addition to nine months’ worth of supplies, it carried the moon dozer. The moon dozer would be the heaviest off-world vehicle launched during the 20th Century. Though it was smaller in volume than the buggy, and lacked a pressurized compartment, it made up for all this with its reinforced construction.
The moon dozer was developed as a construction vehicle in the early days of Moonlab. The HM would not last forever, and just one solid strike from an eraser-sized meteor could puncture its hull. The odds of being struck on any one mission were slim, less so than being struck by lightning on Earth, but over the years the risk would add up. What NASA wanted was a secure habitat, something built into the moon. That was where moon dozer came in. It would not bury the HM, but it would dig out and prepare a trench for the arrival of the Inflatable Habitat Module. The IHM would expand to greater volume than the HM and would be completely buried save for the airlock.
Construction on the moon did not drive the protestors either. The moon dozer was designed to operate during both day and night, and thus required something stronger than solar power to operate. Like the HM, a RTG powered the ‘dozer, and the protestors hated anything nuclear. When the protests on the nightly news were viewed from Moonlab, Stafford commented that the environmentalists would probably protest the ignition of the first, clean fusion reactor just because it was nuclear fusion. Experiments in extracting Helium-3 from the lunar regolith did not attract the attention of anyone save some scientists and engineers back on Earth, even though it would be the fusion fuel of choice. Continued lack of scientific knowledge back home led the majority of Americans to see helium as nothing more than something one puts in a balloon.
Despite the protests, Moonlab VI arrived on the revised schedule. Unloading and assembling the moon dozer required a great effort, even in reduced gravity. Like the moon buggy, it sat on top of the supply module and road down to the surface on a ramp. Unlike the ‘buggy, the ‘dozer was labeled ‘some assembly required’. Three days passed before the moon dozer was declared operational, and Stafford wasted no time in driving it to the HM. Fifty meters away from the HM, he dug the first scoop of regolith out of a hole that would measure 25 x 25 x 10 meters, wide, long and deep. The IHM would take up most of that space, giving the astronauts greater room to maneuver than the HM. The first IHM would be small compared to future designs.
Since the moon dozer was designed to operate in light and dark, when the lunar night passed overhead, the machine’s operation went indoors. A remote control unit came with the ‘dozer and was installed in the already cramp HM. Remote operations were far slower than manual as the astronauts had only a pair of cameras on the moon dozer from which to see their progress. Lighting was also a problem, but only for part of the lunar night. When the moon’s orbit took it into the gibbous and full stages of Earth, sunlight reflected from Earth sufficiently illuminated the landscape. Three weeks were required to excavate a pit that a trained construction crew could have managed in less than a day. With the pit complete, the moon dozer slipped into stand-by mode.
Moonlab V left the moon on December 15, with more than enough time to arrive home by Christmas. The mission returned to Earth with 120 kilograms of moon rocks as well as samples from experiments ran on the moon, including all of the mice. A second batch of rodents would return to the moon with the third manned Moonlab mission in the following year. The Moonlab CM splashed down in the Pacific new Kiribati on December 18. As with the previous return, the crewmen were subjected to rigorous medical tests upon returning to Houston. Slayton underwent the most thorough inspection. Aside from suffering the same rate of bone loss as the other two astronauts, the lengthy stay on the moon had no ill effect on his health.