reactor, would beam laser power to a lunar rover on the surface where the beam would be converted into electricity. The orbiting laser transmitter infrastructure would certainly be used for other purposes when not powering the lunar rover. Thus, power could be beamed to diverse lunar locations for varying periods of time. We will discuss in some detail the laser diode array transmitter in lunar orbit, the orbital mechanics needed to provide continuous laser power to the rover, the laser-to-electric photovoltaic converter on the rover, and finally the thermal control system needed to reject waste heat on the rover. A conceptual picture of the lunar rover is shown in figure 1. The power system should be a small fraction of the total rover mass, giving greater emphasis to mission objectives. The power system resupply requirements are minor, allowing long-duration missions to be accomplished without regard for recharging batteries or fuel cells. We will concentrate our analysis on the power system, leaving the details of the other rover subsystems and shielding requirements to future studies. Previous rover studies have focused on advanced rovers powered by nuclear reactors [2] and fuel cells [3]. The most detailed study to date was done by Eagle Engineering, Inc. [4]. There, the long-duration rover was made up of eight vehicles linked together having a total mass of 17,560 kg. The train configuration consisted of a primary control vehicle, a habitation trailer unit, five auxiliary power carts providing 25 kW and 7000 kW-h of energy to the train, and finally an experiment and sample trailer. Power was supplied by fuel cells which made up one third (5900 kg) of the total system mass. This rover could accomplish a 3000-km round trip, 42-day mission with a crew of four at a maximum speed of 15 km/hr. No provision was made in this study for the mass of equipment needed to generate the H2 and O2 reactants for the fuel cells. This additional mass component could significantly increase the "total" system mass. Rovers powered by nuclear reactors capable of providing 25 kW of electric power have large masses due to the required nuclear shielding of the reactor. Also, since the total reactor usually is not shielded, that area behind the reactor is not accessible to rover personnel. Rovers powered by solar photovoltaics at 25 kW of electricity would require 81 m2 of solar array. Such an array would be much larger than the rover and have high mass. This rover would not be able to operate at lunar night unless there was a large storage capability on board. Laser-power-beaming studies have shown that significant payoff can be achieved by decoupling the prime power source from the user [5], More flexible power infrastructures are achieved for a variety of space missions, from powering of low power robotic rovers to high power, lunar laser propulsion.
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