Night Walker Probe

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Instead of complaining about the difficult conditions of vacuum and temperature extremes on Luna, we should take advantage of them. In this instance a probe is described that is to sit in one spot gathering solar electric energy during the day and move during the night.

The thermal condition of Luna during the local 354 hour night is not intractably difficult. Insulation can be very effective in a vacuum, as it is for satellites in free space. The thermal situation of probe on the night-time surface of Luna is very similar to that of an orbiting satellite in the shadow of a planet. The feet of the robot probe would be the only parts to usually lose heat to the lunar surface directly by conduction. They can be made of materials resistant to cold temperatures. Little heat will be lost through six long slender legs if a little care is taken to reduce this path of heat conduction. Ordinary electrical operation of the probe should provide sufficient heat to maintain operating temperatures. When local daytime approaches the probe should unpack and deploy a 160 centimeter high aluminum foil wall to block infrared radiation between a three meter diameter camp site and the surrounding terrain. Also it should deploy a 4.3 meter diameter umbrella on a 15 meter boom toward the sunrise to shade the campsite. The umbrella is a flat disk with solar cells on the sunward side to gather electricity and shiny aluminum on the underside. Also the probe should deploy counter weights on booms held away from the sunrise on the north and south sides of the probe. The counter weights are baskets of regolith to balance the torque on the robot produced by the 15 meter umbrella boom. The counter weights should hang outside the camp site wall. As the sun moves through the lunar sky the umbrella boom is rotated to always block the sun. The counter weight booms are rotated from the sunset direction to the sunrise direction to balance the torque on the probe produced by the umbrella boom. As the umbrella boom is rotated, the angle of the umbrella to the boom that holds it is tilted so that, from the viewpoint of the probe, the shiny under side of the umbrella reflects the cold black sky. The probe gathers electrical energy during the day and uses it to electrolyze water and liquefy and store the resulting hydrogen and oxygen. At sunset the probe stows the umbrella boom, gathers up and stows the aluminum foil wall using electricity from hydrogen/oxygen fuel cells. It then moves about actively exploring Luna during the Lunar night.

Since the Night Walker Probe is always shaded from sunlight and intense infrared radiation, its situation is always similar to an orbiting satellite in the shade of a planet. While it is shaded by the umbrella and wall during the day, it is still exposed to most of the cold black lunar sky. Its internal temperature should be reasonably controllable to remain within a narrow operating range.

This probe would be optimized for making observations and moving about during the night. It would carry out observations and other activities from its stationary position during the day. The probe should be designed to be active for several years. Leg bearings can be covered by a gas tight accordion type envelope to maintain a slight gas pressure to prevent evaporation of lubricant. Wheel bearings cannot be so covered, so legs might be used instead of wheels as a means of locomotion.

Nuclear Version

With a plutonium 238 powered themionic power source, there would be no need for solar cells on the sunward side of the disk umbrella, so the umbrella could be lighter. There would also be no need for fuel cells, electrolyzing water, liquifying hydrogen and oxygen and storing them. The nuclear powered probe is simpler and definitely preferable if it is politically possible.

See Also