Top speed 4,640 km/h Length 9.98 m | Wingspan 3.66 m Retired 1960 | |
The Lockheed X-7 (dubbed the "Flying Stove Pipe") was an American unmanned test bed of the 1950s for ramjet engines and missile guidance technology. It was the basis for the later Lockheed AQM-60 Kingfisher, a system used to test American air defenses against nuclear missile attack.
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The aircraft is one of the lesser known designs by Kelly Johnson, who went on to become the creator of the SR-71 family of aircraft.

Design and development

The X-7 was carried aloft by a B-29 or B-50 Superfortress carrier aircraft. A booster ignited after launch and propelled the vehicle to a speed of 1,000 mph (1,625 km/h). The booster was then jettisoned, and the underslung ramjet took over from that point. The X-7 eventually returned to Earth, its descent slowed by multistage parachute. It descended in a vertical nose-down attitude. The nose was a long spike which penetrated the ground upon impact preventing damage to the rest of the airframe.

A maximum speed of 2,881 miles per hour (4,637 km/h), or Mach 4.31, was attained, setting a record for fastest air-breathing aircraft at the time. A total of 130 X-7 flights were conducted from April 1951 to July 1960.
The X-7 was unique in that it was constructed of steel, as opposed to the titanium used on later ramjets such as the more well known SR-71, and its predecessors, the A-12 and YF-12. The X-2 test aircraft preceded the X-7 by having Stainless steel wings, but its fuselage was composed of Nickel alloy. Steel was not widely used in aircraft until the later Mig-25 Foxbat.
The X-7 was also used to test HEF-2 and Hi Cal-3 zip fuel, which has a superior heating value of 26,500 Btu/lb. compared to hydrocarbon fuel with 18,400 Btu/lb.
Specifications (X-7A-1)
General characteristics
Performance
The A-3 variant was longer and narrower.