Ranger 4

Launch data: Designation 00280 / 1962 Mu 1 / 62012A Launch date 23 Apr 1962 - 20:50 UT  Launch site CC-LC12 Launch vehicle Atlas-LV3 Agena-B (#133D-AA4) Mission Luner lander Payload code  NASA P-35 Maximum distance from Earth 400.000 km All-burnt velocity 11,0 km/sec Lunar impact 26 Apr 1962 - 12:49:53 UT

Specifications: Prime contractor  JPL Operator  NASA Mass at launch 331 kg Dry Mass   kg Dimension 1,52 dia - 2,51 long Basic shape hexagonal cylinder

Technicians prepare the Ranger 4 spacecraft for launch.

Mission details:

• Second Block II spacecraft to land a sphere relatively softly on the moon. This time the launch vehicle worked well and Ranger-4 was put on the right course for moon impact, but soon after the on-board timer failed to operate and the first thing that this prevented was the solar panels deploying shortly after 2 hours into the mission. The batteries had run down completely by 10 hours and the craft with its 10.5 kg capsule slammed into the moon after 64 hours at 9600 km/h at 15°30' S, 130°42' W being the US first lunar impact.
• An impact absorbing sphere made of balsa wood sits atop the spacecraft, painted with a saw-tooth pattern to maintain thermal balance during its mission to the Moon. The sphere contained a lunar seismometer, which was to rough land just south of the equator on the rim of the Ocean of Storms and measure "lunarquakes."
• The master clock in Ranger 4's computer failed during flight and the spacecraft did not respond to commands. It crashed into the far side of the Moon on April 26, 1962. Despite the failure to return information, the use of balsa wood was an important precursor in the design of other rough landings on extraterrestrial bodies, particularly Mars. Aerobraking, gliding, impact absorption, parachuting, and retro rockets have all been considered.