#90 November 1995
Section 184.108.40.206.090.of the Artemis Data Book
by Bryce Walden
[response to a screenwriter's question on America OnLine, reprinted in MMM with permission]
General contractor for the Lunar Roving Vehicle (LRV) was Boeing; GM Delco made the electronics. The LRV was first used on Apollo 15 at Hadley Rille, and in all subsequent missions. The chassis was aluminum. The essential "buggy" massed 400-600 lbsm (pounds-mass) (180-270 kilograms) depending on equipment. It could carry equipment, astronauts, and payload up to 1100 lbsm (499 kilograms), more than twice its own weight. Yet it was not strong enough to hold the astronauts on Earth.
Top speed mentioned by my source was 14 kph (8.7 mph); the speedometer was calibrated 0-20 kph (0-12.4 mph). Average speed on all three missions using the LRV was 5.17 mph (9.1 kph). Average for Apollo 17 was 5.0 mph (8.0 kph), total distance travelled was 22.3 miles (35.9 kilometers), and total time driving was 4:26 hours.
Power was supplied by 2 silver-zinc batteries, each 36v, 121 amp-hours per battery, encased in magnesium, then enclosed by thermal blankets and dust covers. Each battery had a relief valve for protection against excessive internal pressure. Thermal control was critical: the batteries had to be maintained between 40° F (4° Celsius) and 125° F (52° Celsius). The only practical method of heat rejection in the vacuum was by thermal radiation. Unfortunatly, the slightest amount of lunar dust on the radiators (essentially mirrors) would "effectively destroy" their ability to perform. For this reason the radiators were kept closed during activities, to be opened manually by astronauts after "parking" for the "night." "During operation, heat generated was stored in heat sinks consisting of two LRV batteries and tanks containing wax-like phase change material." According to Gene Cernan and Jack Schmitt, "If you take a couple more batteries up there, that thing would just keep going...."
However, these guys aren't Moon Buggy Mechanics. Other astronauts have been known to say the buggy had used up all warrantees by the end of the mission (5 days or 250,000 miles....). Besides the batteries, the flexible spline inside each wheel hub, part of the kinetic power transmission system, may have degraded. Countless thermal cycles of the vehicle between lunar day (+250° F, 121° Celsius) and lunar night (-250° F, -157° Celsius) will take their toll on structural elements, electronics, and other system parts. There is also the possibility of radiation damage to the control electronics. Of course, it might work, for a little while -- perhaps a heroic last gasp. With fresh batteries, of course. That overpressure release probably let vital elements escape as the batteries heated to lunar daytime temperatures.
One other interesting note is that the LRV had an inertial navigation device that always pointed toward the LEM (bearing and distance), so the astronauts would not have to guess, in the austere and misleading lunar environment (ever taken a walk in the desert?), the quickest way back to the base. They also did not have to stay in sight of the LEM.
Lunar rover data and quotes are from "The Lunar Roving Vehicle: A Historical Perspective" by Saverio F. Morea, Director, Research and Technology Office, NASA Marshall Space Flight Center, Alabama, where the LRV was tested. The paper was presented at the second Lunar Bases and Space Activities of the 21st Century conference, April 5-7 1988, Houston TX. Contribution No. LBS-88-203.
That being said, I don't think we should depend on or plan to use any of the one-shot equipment sent up with Apollo. I prefer the idea of fencing it off and preserving these first explorations as well as possible. We should be sensitive to other sites of interest, as well.
Contents of this issue of Moon Miners' Manifesto