North America and Europe combined have fewer square kilometers of surface area than the moon: 36.8 million for the two continents versus 37.8 million for Earth's natural satellite. In August-September 1992, at the 43rd Congress of the International Astronautical Federation (IAF) in Washington, DC, Madhu Thangavelu, a research associate at the University of Southern California's Institute of Aerospace Systems Architecture and Technology, argued that explorers operating from a fixed surface base - the traditional advanced lunar exploration scenario - could hope to survey only a small fraction of the moon's surface. Moreover, only after several costly manned lunar landing missions had investigated candidate sites could a fixed base site be selected.
At the time Thangavelu presented his paper, the Space Exploration Initiative (SEI), launched by President George H. W. Bush on the 20th anniversary of the first manned moon landing (20 July 1989), was nearing its conclusion. Though at SEI's start NASA had proposed a traditional fixed-site lunar base concept, by the time of the 1992 Washington IAF meeting it had turned its attention to a temporary lunar outpost concept called First Lunar Outpost (FLO). NASA made the change based on recommendations in the May 1991 report of the SEI Synthesis Group (the Stafford Committee).
Thangavelu did not mention FLO in his paper, though he might have noted that it had many of the limitations of a fixed-site base. In its most basic form, FLO would see a series of 45-day piloted missions, each employing one Habitat Lander and one Crew Lander. FLO astronauts would have at their disposal roving vehicles not too different from the jeep-like Apollo rovers. These would permit traverses of at most a few tens of kilometers.
Thangavelu proposed that NASA replace the fixed-site lunar base approach with a "roving base" that would, in a single ambitious piloted mission, explore multiple candidate base sites and the terrain between them along an 11,000-kilometer traverse route. His roving base, the 35-ton Very Long Traverse Vehicle (VLTV), would measure 16 meters long, 4.5 meters wide, and 10 meters high. It would roll on four large wheels, each powered independently by a 120-horsepower electric motor. The complex wheels would change shape automatically to accommodate obstacles and ensure a smooth ride. Typically, the VLTV would rove at about 20 kilometers per hour, though it could travel at up to 30 kilometers per hour if necessary.
The VLTV would contain 600 cubic meters of pressurized volume for its three-person crew, including a control cockpit, individual crew cabins, a meeting room/galley, an airlock, and a hygiene facility. Life support water tanks and stacked bags containing lunar dirt on the vehicle's roof would shield against radiation. A periscope-like assemblage of mirrors and baffles providing radiation protection and an elevated view of the surface would augment a more conventional "windshield," as would cameras and powerful floodlights.
The mobile base would actually comprise two vehicles. An automated "power cart" bearing a nuclear reactor would follow about a kilometer behind the VLTV. It would supply 50 kilowatts of electricity to the piloted rover either through a long durable cable or through intermittent microwave beaming. An auxiliary fuel cell/solar cell system on the VLTV would provide 10 kilowatts of backup electricity.
The most novel feature of Thangavelu's VLTV design was its EVA Bell, an accordion-like structure that would extend down from its underside. Thangavelu meant for the 48-cubic-meter EVA Bell to eliminate what he considered to be the worst feature of moonwalks: that is, the need for bulky space suits. Space suits, he explained, decreased astronaut mobility and dexterity, caused fatigue, and required time for donning. The EVA Bell would also protect the astronauts from abrasive lunar dust.
The roving base would include two robot arms that could stand in for or assist space-suited astronauts. These would ride on tracks on the VLTV's exterior, enabling them to extend from the rover in any direction.
The VLTV would, of course, require a supporting infrastructure. Thangavelu envisioned a revived Saturn V rocket which he called the "Saturn V-B." This would launch Autonomous Modular Common Landers (AMCLs) configured for either automated or piloted operation. Though he did not mention it, NASA's proposed FLO launch vehicle, informally called the "Saturn VI," could have stood in for the Saturn V-B with modest uprating or if used in an Earth-Orbit Rendezvous architecture. Uprated, modified FLO Crew and Habitat Landers could have replaced the AMCLs.
An automated AMCL would land the VLTV at the start of its planned traverse route. Others would land supplies and experiment payloads no more than 3000 kilometers apart along the route. A one-way piloted AMCL would deposit the VLTV crew near the roving base at the starting point of the long traverse, and an automated AMCL bearing a crew Earth-return vehicle would land at the end of the traverse route.
The astronauts would then begin their six-month journey across the moon's rolling, dusty terrain. Upon reaching the first resupply AMCL, they would use the VLTV's robot arms to transfer supplies it carried to a special port on the VLTV, then would put the EVA Bell into action. First, they would use the VLTV's robot arms to spread a "mat" on the lunar surface. The crew would then use the arms to transfer a site-specific scientific payload from the AMCL to the center of the mat.
Next, the astronauts would position the VLTV so that it straddled the payload. They would extend the EVA Bell, which would lock onto the mat, forming an air-tight seal. The astronauts would fill the EVA Bell with air at a pressure of eight pounds per square inch, then would climb down into it to deploy the payload. After they completed their tasks, they would exit the EVA Bell, pump out its air, and raise it off the mat, exposing the payload to lunar surface conditions.
In addition to scientific instruments, the astronauts would deploy a telecommunications network for future operations as they moved over the lunar surface. Upon reaching the end of their traverse, they would place the VLTV in "hibernation." They would then board the pre-landed Earth-return vehicle and blast off for home.
Reference:
"The Nomad Explorer Assembly Assist Vehicle: An Architecture for Rapid Global Lunar Infrastructure Establishment," IAF-92-0743, Madhu Thangavelu; paper presented at the 43rd Congress of the International Astronautical Federation, 28 August-5 September 1992, Washington, DC.
