Scramjet programs

Scramjet programs refers to research and testing programs for the development of supersonic combustion ramjets, known as scramjets. This list provides a short overview of national and international collaborations, and civilian and military programs. The USA, Russia, India, and China (2014), have succeeded at developing scramjet technologies.

When the second X-15 aircraft (piloted by Jack McKay) crashed on flight 74, it was damaged but survived well enough to be rebuilt. North American Aviation rebuilt it as the X-15-A2. Among other things, one of the changes was provisions for a dummy scramjet to test if wind tunnel testing was correct. Unfortunately, on the final flight of the X-15-A2 (flight 188), the shock waves sent out by the scramjet at Mach 6.7 caused extremely intense heating of over 2,700 °F (1,480 °C). This then drilled into the ventral fin and melted large holes. The plane survived but never flew again. Test data were limited due to the limited flights of the scramjet before the X-15-A2 and the X-15 project on the whole were cancelled.

From 1962–1978, the Johns Hopkins Applied Physics Laboratory (APL) undertook a classified program (declassified in 1993) to develop a family of missiles called SCRAM (Supersonic Combustion RAmjet Missile). They were intended to fit on to the Talos MK12 launcher system or the Terrier MK10 launcher. Testing of engine modules in a direct-connect, and a free-jet, facility took place at a variety of Mach numbers and pressures (altitudes). These included Mach 4 (24,000 ft), Mach 5.3 (46,000 ft), Mach 7.8 (67,000 ft) and Mach 10 (88,000 ft). Tests showed that acceptable combustion efficiency was only achieved with over 20% pentaborane (B5H9) in MCPD (C12H16). Tests with pure pentaborane (HiCal) showed that a net thrust could be achieved at Mach 7. An accelerative capability equivalent to 11g was observed for Mach 5 flight at sea level.

In 1986 United States president Ronald Reagan announced the National Aerospace Plane (NASP) program, intended to develop two X-30 aircraft capable of single stage to orbit (SSTO), as well as horizontal takeoff and landing from conventional runways. The aircraft was to be a hydrogen fuelled air-breathing space plane, with a low speed accelerator system to bring the aircraft up to Mach 3, where the main dual-mode scramjet engines (ramjet/scramjet) would take over. At the edge of the atmosphere, a rocket was to take over and provide the final energy for orbital insertion. It was based on a classified DARPA research program called Copper Canyon. This research program suggested that Mach 25 might be possible. As the program proceeded it became clear that Mach 17 was probably the limit, whilst the weight penalty and complexity of the skin heat exchanger and other propulsion systems was going to be substantial. The program was established by the secretary of defence in 1985, and was funded to the end of FY1994, when the decision was made that the 15 billion dollars required to build the two X-30 test craft were excessive.

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