President George H. W. Bush's Space Exploration Initiative (SEI) was for many a process of rediscovery. In the November 1989 90-Day Study report, their first major statement on how to carry out SEI, NASA planners described an elaborate and costly scheme to construct a lunar base using modules and equipment delivered atop unmanned landers. Construction gangs of astronauts would use a high-tech bulldozer or grader to prepare the ground and an "unloader" to lift the modules off the landers and position them on the surface. After assembly, a high-tech end-loader or "snow-blower" would bury the modules under lunar dirt to provide radiation shielding.
SEI's high estimated cost and consequent chilly reception in Congress, combined with NASA's growing realization that an excessively large number of spacewalks would be needed to assemble and maintain its modular, Space Shuttle-launched Space Station Freedom (SSF) in low-Earth orbit (LEO), drove SEI planners to seek a new lunar outpost concept that would cost less and require as little lunar surface assembly as feasible. They hoped that such an outpost might serve as a stepping stone between early brief lunar sorties and the 90-Day Study's vision of a complex constructed base. The outpost concept they found was, however, not new; it was, in fact, a generation old.
Boeing's 1991 Lunar Campsite concept resembled the company's own 1964 Lunar Exploration Systems for Apollo (LESA) concept. In both plans, a one-way Habitat Lander would set down at a target lunar site sans crew, then a round-trip Crew Lander would land nearby. The astronauts would transfer to the Habitat for an extended stay. The Habitat module would remain attached to its lander - no deployment or assembly would be necessary - and the astronauts would rely for radiation protection on a small internal shelter, not Habitat burial. Extended lunar surface stay completed, the crew would either abandon the Habitat Lander or mothball it for the next crew, then would return to Earth in the Crew Lander.
Boeing's LESA assumed the existence of the Saturn V rocket, which was under development at the time of its study; Boeing's Lunar Campsite plan assumed the existence of a man-rated heavy-lift rocket capable of launching about 95 metric tons into LEO, which was not. The first Lunar Campsite payload launched into LEO, the unmanned 90-metric-ton Campsite Vehicle. would include a 9.5-meter-diameter Lunar Transfer Vehicle (LTV) with four chemical-propellant rocket engines, four landing legs, and a 4.4-meter-diameter, 28.7-metric-ton Habitat Module with an attached Airlock Module. The cylindrical crew modules, derived from SSF module designs, would be mounted among the engines at the bottom of the LTV. This would place them close to the surface after landing, enabling easy egress and ingress for moonwalking astronauts.
A second LTV, the unmanned 92.7-metric-ton "booster," would be joined to the top of the Campsite Vehicle in LEO, creating a 27-meter-long vehicle "stack." The booster LTV would fire its engines until it depleted all of its propellants, placing the Campsite Vehicle into a high elliptical Earth orbit. The Campsite Vehicle would then separate from the booster and fire its engines at perigee (the low point in its orbit) to place itself on course for the moon.
A few days later, the Campsite Vehicle would pass behind the moon and ignite its engines a second time to capture into a "fractional" lunar orbit; that is, one that would intersect the lunar surface. This approach was a compromise between a direct descent to the lunar surface from an Earth-moon trajectory and insertion into lunar orbit followed by a deorbit maneuver and descent.
As the Campsite Vehicle fell toward its target landing zone, it would again ignite its engines, tip upright, and lower to a gentle touchdown. It would then automatically level itself, eliminating any need for graders or bulldozers. Boeing explained that the Campsite Vehicle could stand up straight on a slope of up to 12° by extending or retracting individual landing legs. It would also automatically deploy radio antennas, shadow shields that would enable its thermal radiators to operate efficiently while in full sunlight, and electricity-generating solar arrays.
Controllers on Earth would check out the Campsite Vehicle remotely and, if it passed muster, would give the go-ahead for the 94.3-metric-ton manned Crew Vehicle to depart for the moon. The Crew Vehicle would resemble the Campsite Vehicle; however, an eight-metric-ton conical Earth-reentry crew capsule, 3.7 metric tons of supplies, and twin unpressurized rovers and science equipment with a combined mass of 3.2 metric tons would replace the latter's Habitat and Airlock. The Crew Vehicle capsule would provide life support for four astronauts for 10 days.
The Crew Vehicle would follow the same mission profile as the Campsite Vehicle until it landed on the moon. After landing close to the Campsite Vehicle (image at top of post), the astronauts would mothball the crew capsule and use the rovers to transfer 600 kilograms of food, two spare space suits, 540 kilograms of space suit spare parts, 425 kilograms of oxygen for moonwalks, and other supplies to the Campsite Vehicle.
The astronauts would live in the Campsite Vehicle Habitat for 45 days. If a flare erupted on the Sun, the crew would lift a floor panel and climb down into a radiation shelter, the floor and walls of which would be lined with drinking water tanks. Space suits, spare parts, and emergency supplies would be stored in the radiation shelter when it was not in use. The crew would be able to abort to Earth in the Crew Vehicle at any time in the event of major Campsite Vehicle malfunction, serious crew illness or injury, or other difficulties.
The Lunar Campsite crew would conduct one two-person moonwalk per day. Each moonwalk would employ one rover and 150 kilograms of science gear. In the event of rover breakdown, the two astronauts left behind in the Campsite Vehicle Habitat would suit up and use the second rover to retrieve the first.
As their extended stay on the moon neared its end, the crew would mothball or abandon the Campsite Vehicle and transfer back to the Crew Vehicle with up to 500 kilograms of lunar and biomedical samples. They would ignite the Crew Vehicle's four engines to put themselves onto a direct course back to Earth. Near Earth, they would cast off the LTV and reenter Earth's atmosphere in the crew capsule.
Boeing engineers found in 1991, as they had in 1964, that the Lunar Campsite concept could have diverse applications. With Campsite Vehicle resupply, multiple missions could be dispatched to a single Lunar Campsite. Alternately, a series of Campsite Vehicles, each inhabited by a single crew, could land at scientifically interesting sites all over the moon. The company also suggested that, after a site had been thoroughly explored, a Campsite Vehicle might ignite its rocket engines to fly to a fresh exploration site.
A Campsite Vehicle could also help to end the Lunar Campsite era by serving as a "construction shack" for workers constructing a permanent lunar base. Even after the permanent base reached full operational status, however, Campsite Vehicles might still be useful: one might, for example, be dispatched from Earth to serve as an outpost in a remote lunar location, or could be used to simulate and rehearse Mars landing missions on the moon.
The Lunar Campsite concept inspired the SEI Synthesis Group, led by ex-Gemini and Apollo astronaut Thomas Stafford, to adopt a similar proposal in its May 1991 report America at the Threshold. The report, prepared for the White House, was meant to collate diverse innovative concepts for accomplishing SEI that had been gathered through an "outreach program." The LESA/Lunar Campsite concept's inclusion in the Stafford Report led to NASA's last major SEI-related lunar study, which Congress only grudgingly agreed to fund. Called First Lunar Outpost (FLO), it made use of an unmanned one-way Habitat Lander and a piloted round-trip Crew Lander, each launched on a massive booster rocket. FLO study work began in late 1991 and concluded as SEI and Bush's single term in office ended in early 1993.
Reference:
Lunar Campsite Concept, Carl M. Case, Boeing, presentation materials, February 1991.
