A test model of the Surveyor lunar soft-landing spacecraft successfully performed a radar-controlled landing at Holloman AFB May 11.
The test marked the first time a test vehicle has been flown to an actual soft landing on the desert.
Two radar dishes on the craft provided continuous information on altitude and rate of descent. An electronic flight control subsystem translated the information into signals to throttle three small liquid fuel rocket engines to slow the test spacecraft to a landing speed of about 3 ½ miles per hour.
Surveyor will approach the moon at a speed of about 6000 miles per hour and will be slowed to about 240 miles per hour by the firing of a large, solid fuel retro-motor. It will then be slowed to about 3 ½ miles by the three liquid engines.
For last week’s test, the vehicle was raised to an altitude of 1000 feet by a balloon; then its engines, radar, and electronics were warmed up and tested before the test vehicle was released. With both engines at a low thrust, the test vehicle fell toward the desert floor until it reached a speed of about 45 miles per hour at an altitude of 625 feet, approximating the speed of a Surveyor at the same lunar altitude. The engines then were throttled by the flight control subsystem, acting on radar information, to slow the test craft.