# 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. This article suggest sample solutions to show that solutions exist. Better sollutions than these will be developed.

### Thermal Management

The Apollo astronauts used expendables for thermal management and recycled nothing. We can not use up expendables at that rate for years for robot explorers. Thermal management for lunar rovers is possible with radiators that do not use up expendables. One scheme is related to the simpler thermal management of a stationary base. 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 and reject incident sunlight to space. Such a trough would have a cross section in the shape of the curve that graphically represents y=x^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. The rover using such a radiator would best have six or more legs, so it could walk any direction without changing its heading.

### 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.

### Dust

There is no need for dust to be a bogeyman that prevents plans for long term operation of devices on Luna. The lunar dust is certainly nasty stuff, but it can be dealt with. Consider how dust gets stuck to devices on Luna. 1) DIRECT CONTACT: The area of devices that contact Luna must be limited to nonsensitive areas. The wheels of a rover can contact Luna and come into thermal equilibrium with the surface. The wheels would be locked to the axles and the rotary bearing would be within the rover allowing each axle to turn as one with its wheel. Dust picked up by the wheel would fall only on a protruding section of axle. 2) BALLISTIC TRANSFER: The speed of the rover would be limited to prevent dust being thrown in detrimental ballistic trajectories. 3) WIND: There are neither air currents nor wind on Luna. 4) ELECTROSTATIC FORCE: Static charges in dust particles cause the positively charged particles to move toward negative potentials and negatively charged particles to move toward positive potentials. Most of a rover would be covered with aluminum foil maintained at one potential. Antennae of the proper shape and charge can dissipate overall excess charge. Electronic grid elements of various shapes and potentials will either draw dust particles to disposal and so remove them from sensitive spots or simply repel dust particles from those spots. Simulated lunar dust in vacuum chambers on Earth can be treated in various ways to produce charged dust particles. So rover designs can be tested on Earth to be reasonably sure that dust will not settle in sensitive spots. What other way can dust move? It must obey physical laws.

### 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. The least necessary of these design features are the micrometeoroid protective shields. The cost of these features includes the cost of a somewhat larger radiator. The cost must be balanced against the risk. Merely isolating damaged radiator sections may be most cost effective.