HARP 7 & 5 in probes

The Harp 7-2 vehicle was an optimized version of the 7-1 vehicle. The 7-2 had a body diameter of 76 mm a length of 1410 mm a flight weight of 18.2 kg and a payload volume of 2048 cc. The 7-2 prove was designed with a much-improved streamlined shape and exhibited far cleaner aerodynamics. The smaller 7-2 probe was capable of reaching altitudes of 105 km which allowed it to carry payloads through the D-layer and into the lower E-layer of the ionosphere - the very edge of space itself.

The 7-2 probe was used for a multitude of payloads including the standard ejectable chaff flown in the 5-1 probes. Of note was the 7-2 probe's ability to carry chemical payloads such as cesium nitrate, which was used to create artificial electron clouds, and to carry Langmuir probes with associated radio telemetry.

The 7 inch HARP gun system proved to be a valuable atmospheric research tool with some 60 operational flights over a 3 year period. Perhaps the least recognized gun system of the HARP program, the 7 inch HARP guns were poised to prove just how versatile and valuable a research tool they could have been when, in 1967, the HARP project abruptly ended leaving their true potential unfulfilled.

by Richard K Graf

Typical orbit: 105 km altitude. Length: 1.41 m (4.62 ft). Maximum Diameter: 0.0760 m (0.2490 ft). Span: 0.18 m (0.58 ft). Mass: 18 kg (40 lb). Associated Launch Vehicle: 7 inch HARP Gun.