Long Endurance Rovers
long endurance robotic lunar rovers and manipulators
On most of Luna a roving robot explorer must either be made to endure 354 hour days followed by 354 hour nights or be considered a disposable rover. If we can not build things to continue operating a few years at a stretch on Luna, we might as well forget about a lunar base.
The Apollo astronauts used liquid oxygen evaporative cooling for thermal management. We do not want to use up oxygen at that rate for years for robot explorers. Especially we do not want to waste oxygen before an oxygen extraction plant is operational. There is another way. At the equatorial region a wall could be set up running east and west and inclined away from the nearest pole by an angle equal to the latitude. The top of such a wall can be covered with reflective aluminum and that is the only part of the wall that the sun strikes. A trough shaped aluminum parabolic reflector can be built to shield the wall from the surrounding hot lunar landscape such that in cross section the reflector would have the shape of the curve that graphically represents x=y^2 over the range of x=0.7, y=0.49 to x=-0.7, y=0.49 while the cross section of the wall would be represented by the line segment from x=0, y=0 to x=0 y=0.2. Sunlight that strikes the inside of such a trough will be focused above the wall and return to space. The wall can house a radiator shaped and coated for high emissivity. This radiator would be effectively shaded from sun and hot lunar terrain and radiate to the cold of space. By circulating a solution of water and ethylene glycol through this radiator cooling can be provided for sensitive equipment without throwing out any mass of evaporated liquid. Shrink this concept so that it can be carried by a rover and the rover should survive the day.
Staying All Night
At night an insulative cover can be pulled over the radiator. Sintered brick shelters can be built for spending the night and pumped storage of high pressure oxygen can run electric generators at night. Until these things can be available a radio thermal generator can provide heat and power during the night.
Costs and Benefits
These design considerations certainly complicate the making of a lunar vehicle, but producing a device that will operate five or more years and potentially be repairable should be about 130 times as valuable as one that only works two weeks before turning into a piece of scrap.