The lunar roving vehicle was among the more important new developments for the extended Apollo missions, since it would allow the astronauts to sample a much larger area around the landing site. When Boeing won the rover contract in November 1969, it had little time to produce the novel vehicle: at the time the schedule called for flight of the first rover on Apollo 16 in April 1971.4 Many details of design were still to be settled, and much of 1970 was spent in ironing them out.
What evolved from the program was a unique four-wheeled vehicle remarkable for its versatility and compactness. Smaller than a subcompact car, the rover had a 2.3-meter (7.5-foot) wheelbase and measured 3.1 meters long, 1.8 meters wide, and 1.14 meters high (10 x 6 x 3.75 feet). For its trip to the moon, all four wheels folded inward and the rover folded double for stowage in the descent stage of the lunar module. It was powered by two 36-volt silver-zinc batteries with sufficient power for a range of 65 kilometers (40 miles) at speeds up to 17 kilometers per hour (11 miles per hour). If either battery failed the other could carry the entire load. Four separate motors, one at each wheel, drove the vehicle; any wheel could be cut out of the circuit and allowed to "free-wheel" if its drive mechanism developed problems. Tires of spring-steel wire mesh carried treads of titanium-alloy chevrons for traction; "bump stops" inside the wire mesh prevented collapse of a tire in case of severe shock. Two collapsible seats were mounted on the chassis, along with racks for equipment, tools, and sample bags.
All the rover's driving functions - forward and reverse speed, braking, and steering - were controlled by a T-handle mounted between the seats. Besides fourwheel drive, the rover featured redundant four-wheel steering. Either front or rear wheels could be turned while the other pair was locked straight, or both could be used simultaneously, allowing the rover to turn completely around within its own length. It could clamber over obstacles 30 centimeters (1 foot) high, climb and descend slopes of 25 degrees, and park on slopes as steep as 35 degrees.
The rover navigated by a dead-reckoning system. At the start of a traverse the astronauts oriented the system's navigational gyroscope with reference to the sun. During the trip, odometers recorded the distance traveled and the system continuously computed and displayed the direction and distance to the lunar module.
Communications from the rover were relayed to earth through the lunar module, but could be sent directly to earth when the lunar terrain blocked the line of sight between the two vehicles. Mounted on the front of the rover were a television camera and a high-gain antenna. At each stop the astronauts would activate the camera and orient its antenna toward earth. For the first time, scientists at Mission Control would be able to look over the astronauts' shoulders during surface exploration. Unlike the rover itself, the camera could be controlled from earth, allowing scientists to direct the lunar activity, if necessary, on the basis of what they could see. Alternatively, they could use the camera to survey the area for interesting features while the astronauts carried out their preplanned activities.
Fully equipped and ready for flight, the lunar rover weighed just over 200 kilograms (440 pounds) and could carry about 490 kilograms (1,080 pounds), including the astronauts, their life-support systems, their tools and equipment, and 27 kilograms (60 pounds) of lunar samples that could be brought back to the lunar module on each trip. Models to be flown on missions were designed to support this weight on the moon; in all prelaunch tests they had to be supported on special racks, since if anyone inadvertently sat down on one it could collapse.5
Development of the rover was not without its problems. Although the project got some schedule relief with the postponement of the first flight from April to July 1971, at one point it was estimated to be two months behind schedule.6 The deficit was soon made up, however. The one-g training vehicle, a structurally strengthened version equipped with conventional fires for use on earth, was delivered on November 18, 1970, and crews immediately began training with it.7 The first vehicle to be flown to the moon was delivered to Kennedy Space Center the following March for prelaunch testing. Eight weeks later the rover was stowed in the lunar module and both were loaded into the Saturn V stack.8
In January 1971 Apollo 15's scientific instruments began arriving at Kennedy Space Center, where they were subjected to two months of extensive preflight testing. KSC engineers had more than a few problems with the instruments, as they usually did when a new component was added to the spacecraft. Some arrived late; principal investigators or contractor representatives often wanted to make small changes or conduct last-minute tests. Mechanical problems complicated the process as well. Two of the instruments had to be extended from the service module on long booms to avoid interference from spacecraft systems. The booms, designed for zero-g operation, would not support the instruments in earth gravity, so on-the-spot fixes had to be improvised, with less than completely satisfactory results. But calibrations were finally completed and the SIM was returned to North American's California plant for rework. When retesting was completed in late April, the package was installed in the service module. The lunar subsatellite arrived in May and after checkout was loaded into the space craft on June 9.9
4. OMSF, "Manned Space Flight Management Council, October 15, 1969, Status Highlights."
5. MSC, "Apollo 15 Press Kit," July 15, 1971; S. F . Morea, "Lunar Rover Briefing, Kennedy Space Center, July 23, 1971," transcript.
6. Morea, "Lunar Rover Briefing"; Dale D. Myers to Administrator, "Manned Space Flight Weekly Report," Feb. 2, 1970; ibid., Sept. 8, 1970.
7. Myers to Adm., "Manned Space Flight Weekly Report, Nov. 23, 1970.
8. Charles D. Benson and William Barnaby Faherty, Moonport: A History of Apollo Launch Facilities and Operations , NASA SP-4204 (Washington, 1978), pp. 508-14.
9. Ibid., pp. 507-508.