The United States Air Force, the "Bundeswehr's" Luftwaffe, and the Soviets' VVS all conducted experiments in zero-length launching. The first manned aircraft to be ZELL-launched was an F-84G in 1955. The Soviets' main interest in ZELL was for point defense-format protection of airfields and critical targets using MiG-19s. The American tests with the F-84s started with using the Martin MGM-1 Matador solid-fuel boost motor of some 240 kilonewton (52,000 lbf) thrust output, which burned out seconds after ignition and dropped away from the manned fighter a second or two later. Tests of the larger F-100 Super Sabre and SM-30 (MiG-19) (with the SM-30 using the Soviet-design PRD-22R booster unit) used similar short-burn solid fueled boost motors, albeit of a much more powerful 600 kN (135,000 lbf) thrust-class output levels.