Scramjet

A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion (hence ramjet), but whereas a ramjet decelerates the air to subsonic velocities before combustion using shock cones, a scramjet has no shock cone and slows the airflow using shockwaves produced by its ignition source in place of a shock cone. This allows the scramjet to operate efficiently at extremely high speeds. The Bell X-1 attained supersonic flight in 1947 and, by the early 1960s, rapid progress toward 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. During the US aerospaceplane program, between the 1950s and 1960s, Alexander Kartveli and Antonio Ferri were proponents of the scramjet approach. In the 1950s and 1960s, a variety of experimental scramjet engines were built and ground tested in the US and the UK. Antonio Ferri successfully demonstrated a scramjet producing net thrust in November 1964, eventually producing 517 pounds-force (2.30 kN), about 80% of his goal. In 1958, an analytical paper discussed the merits and disadvantages of supersonic combustion ramjets. In 1964, Frederick S. Billig and Gordon L. Dugger submitted a patent application for a supersonic combustion ramjet based on Billig's PhD thesis. This patent was issued in 1981 following the removal of an order of secrecy. In 1981, tests were made in Australia under the guidance of Professor Ray Stalker in the T3 ground test facility at ANU. The first successful flight test of a scramjet was performed as a joint effort with NASA, over the Soviet Union in 1991.