<P> During World War II, a tremendous amount of time and effort were put into researching high - speed jet - and rocket - powered aircraft, predominantly by the Germans . After the war, the US and UK took in several German scientists and acquired various military technologies through Operation Paperclip, including technology surrounding jet engines . The Bell X-1 attained supersonic flight in 1947 and, by the early 1960s, rapid progress towards faster aircraft suggested that operational aircraft would be flying at "hypersonic" speeds within a few years . Except for specialized rocket research vehicles like the North American X-15 and other rocket - powered spacecraft, aircraft top speeds have remained level, generally in the range of Mach 1 to Mach 3 . </P> <P> In the 1950s and 1960s a variety of experimental scramjet engines were built and ground tested in the US and the UK . In 1958, an analytical paper discussed the merits and disadvantages of supersonic combustion ramjets . In 1964, Drs . Frederick S. Billig and Gordon L. Dugger submitted a patent application for a supersonic combustion ramjet based on Billig's Ph. D. thesis . This patent was issued in 1981 following the removal of an order of secrecy . </P> <P> In 1981 tests were made in Australia under the guidance of Professor Ray Stalker in the T3 ground test facility at ANU . </P> <P> The first successful flight test of a Scramjet was performed by the Soviet Union in 1991 . It was an axisymmetric hydrogen - fueled dual - mode scramjet developed by Central Institute of Aviation Motors (CIAM), Moscow in the late 1970s . The scramjet flight was flown captive - carry atop the SA - 5 surface - to - air missile that included an experiment flight support unit known as the "Hypersonic Flying Laboratory" (HFL), "Kholod". </P>

Supersonic combustion in air-breathing propulsion systems for hypersonic flight