In forty-five years of spaceflight and exploration, there have only been six rovers: three Apollo mission lunar rovers, two Russian Lunokhods, and one Sojourner rover on Mars. Under current conditions, the need has been for small robotic vehicles rather than a vehicle to transport humans.
Original Use and Purpose
The primary purpose of the Apollo lunar rovers was to transport the astronauts, saving their energy and oxygen supplies for collecting rock samples to bring back to Earth. These rovers were built by the Boeing Company and NASA's Marshall Space Flight Center. Rovers were sent on Apollo 15, 16, and 17. Each one weighed about 204 kilograms (450 pounds) and could carry about 454 kilograms (1,000 pounds). The frames were made of aluminum alloy tubing, and the chassis was hinged in the middle so that the rover could be folded up and fit in the lunar module. There were two foldable aluminum seats with nylon webbing. Adjustable footrests, Velcro seat belts, and an armrest between the seats were important features. Communications were aided by a large metal dish antenna mounted on the back. The suspension consisted of a double horizontal wishbone torsion bar.
The wheels were a woven mesh about 23 centimeters (9 inches) wide that was made of zinc-coated steel strands with aluminum rims and disks. The chevron-shaped treads were made of titanium. An important feature was the dust guard for each wheel. The Moon's fine dusty regolith covered everything. The rover kicked up the regolith and would not have been operable without the dust guards. At one point a spare guard had to be fashioned out of a notebook cover because the original had been damaged. Each wheel had its own 0.25-horsepower motor.
Power was supplied by a 36-volt silver zinc potassium hydroxide battery that could not be recharged but would run for 121 amp hours. A 36-volt outlet for communications or a television camera was mounted up front.
The original cost estimate was $19 million for each unit, but the final cost was $38 million. Four were built for use on the Moon, one of which was used for parts when the last mission was dropped. Several prototypes were made as well.
Each rover had a 48-kilometer (30-mile) range and could theoretically go about 13 kilometers (8 miles) per hour. For the three missions the total mileage traveled was around 95 kilometers (60 miles). All three rovers remain on the Moon and have only a minimal number of plastic parts that might deteriorate.
There are two Lunokhod rovers from the Soviet Union on the Moon. The Lunokhod 2 had a mass of 838 kilograms (1,848 pounds) and was about 1.5 meters (5 feet) long and 1.5 meters (5 feet) wide. It had eight wheels, each with its own suspension, motor, and brake. Because it carried its four cameras, it could go 1 or 2 kilometers per hour (0.6 to 1.2 miles per hour), receiving directions for movement from controllers on Earth.
Power was supplied by solar panels. The rover was designed to work during the two-week long lunar day, periodically charging its batteries. At night it would shut down, retaining warmth from a radioactive heat source. The rover was equipped with many scientific instruments. Lunokhod 2 operated for 4 months and covered around 35 kilometers (22 miles) of lunar terrain.
For several years there was a lunar rover initiative to promote new designs for lunar rovers sponsored by Carnegie Mellon University and Luna-Corp. Radio Shack has bought sponsorship rights to the Icebreaker rover, which is earmarked to explore a crater at the polar region of the Moon that is thought to harbor ice in an area where sunlight never reaches. Another design being tested is the Nomad, a 544-kilogram (1,200 pounds) rover.
Future Uses of Rovers
Rovers will be important to any future lunar colonies because they will increase the amount of ground that can be explored safely and efficiently. Locating water as well as other mineral resources will require the extensive use of new-generation rovers equipped with high-technology electronics. The race to land a human on the Moon may be over, but the race to discover and tap its resources is just beginning. Plans call for the use of a variety of rovers in plans involving the exploration of Mars over the next decade. Rovers will collect rock and soil samples and search for subsurface water in their landing site area.
see also Apollo (volume 3); Apollo Lunar Landing Sites (volume 3); Mars Missions (volume 4); Moon (volume 2); Robotic Exploration of Space (volume 2); Robotics Technology (volume 2).
Gatland, Keith. The Illustrated Encyclopedia of Space Technology, 2nd ed., Philip de Ste. Croix, ed. New York: Orion Books, 1989.
"Luna 21/Lunokhod 2." National Space Science Data Center. National Aeronautics and Space Administration. <http://.www.gsfc.nasa.gov/nmc/tmp/1973-001A.html>.