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.
USA
X-15 When the second X-15 aircraft (piloted by John B. 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 . 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.
SCRAM 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.
NASP 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.
Although the more visible parts of the program were cancelled, NASP provided a large amount of basic research, which flowed into following projects. For example, The NASP reaction model for hydrogen combustion in air (31 reactions, 16 species), is still extensively used where computational power is sufficient not to have to use reduced reaction models.
GASL projectile At a test facility at Arnold Air Force Base in the U.S. state of Tennessee, the General Applied Science Laboratory (GASL) fired a projectile equipped with a hydrocarbon-powered scramjet engine from a large gun. On July 26, 2001, the four inch (100 mm) wide projectile covered a distance of 260 feet (79 m) in 30 milliseconds (roughly 5,900 mph or 9,500 km/h).Hypersonic Scramjet Projectile Flys In Missile Test. SpaceDaily.com http://www.spacedaily.com/news/scramjet-01a.html The projectile is supposedly a model for a missile design. Many do not consider this to be a scramjet "flight," as the test took place near ground level. However, the test environment was described as being very realistic.
Hyper-X The $250 million NASA Langley Hyper-X X-43A effort was an outgrowth of the canceled National Aerospace Plane (NASP) program on which NASA was a collaborator. Rather than developing and flying a large, expensive spaceplane with orbital capability, Hyper-X flew small test vehicles to demonstrate hydrogen-fueled scramjet engines. NASA worked with contractors Boeing, Microcraft, and the General Applied Science Laboratory (GASL) on the project.
NASA's Hyper-X program is the successor to the National Aerospace Plane (NASP) program which was cancelled in November 1994. This program involves flight testing through the construction of the X-43 vehicles. NASA first successfully flew its X-43A scramjet test vehicle on March 27, 2004 (an earlier test, on June 2, 2001, went out of control and had to be destroyed). Unlike the University of Queensland's vehicle, it took a horizontal trajectory. After it separated from its mother craft and booster, it briefly achieved a speed of 5,000 miles per hour (8,000 km/h), the equivalent of Mach 7, easily breaking the previous speed record for level flight of an air-breathing vehicle. Its engines ran for eleven seconds, and in that time it covered a distance of 15 miles (24 km). The Guinness Book of Records certified the X-43A's flight as the current Aircraft Speed Record holder on 30 August 2004. The third X-43 flight set a new speed record of 6,600 mph (10,620 km/h), nearly Mach 10 on 16 November 2004. It was boosted by a modified Pegasus rocket which was launched from a Boeing B-52 at 13,157 meters (43,166 ft). After a free flight where the scramjet operated for about ten seconds the craft made a planned crash into the Pacific Ocean off the coast of southern California. The X-43A craft were designed to crash into the ocean without recovery. Duct geometry and performance of the X-43 are classified.
The NASA Langley, Marshall, and Glenn Centers are now all heavily engaged in hypersonic propulsion studies. The Glenn Center is taking leadership on a Mach 4 turbine engine of interest to the USAF. As for the X-43A Hyper-X, three follow-on projects are now under consideration:
X-43B: A scaled-up version of the X-43A, to be powered by the Integrated Systems Test of an Air-Breathing Rocket (ISTAR) engine. ISTAR will use a hydrocarbon-based liquid-rocket mode for initial boost, a ramjet mode for speeds above Mach 2.5, and a scramjet mode for speeds above Mach 5 to take it to maximum speeds of at least Mach 7. A version intended for space launch could then return to rocket mode for final boost into space. ISTAR is based on a proprietary Aerojet design called a "strutjet", which is currently undergoing wind-tunnel testing. NASA's Marshall Space Propulsion Center has introduced an Integrated Systems Test of the Air-Breathing Rocket (ISTAR) program, prompting Pratt & Whitney, Aerojet, and Rocketdyne to join forces for development.
X-43C: NASA is in discussions with the Air Force on development of a variant of the X-43A that would use the HyTECH hydrocarbon-fueled scramjet engine. The US Air Force and Pratt and Whitney have cooperated on the Hypersonic Technology (HyTECH) scramjet engine, which has now been demonstrated in a wind-tunnel environment.
While most scramjet designs to date have used hydrogen fuel, HyTech runs on conventional kerosene-type hydrocarbon fuels, which are much more practical for support of operational vehicles. A full-scale engine is now being built, which will use its own fuel for cooling. Using fuel for engine cooling is nothing new, but the cooling system will also act as a chemical reactor, breaking long-chain hydrocarbons down into short-chain hydrocarbons that burn more rapidly.
X-43D: A version of the X-43A with a hydrogen-powered scramjet engine with a maximum speed of Mach 15.
FASST On December 10, 2005, Alliant Techsystems (ATK) successfully flight-tested an air-breathing, liquid JP-10 (hydrocarbon) fuelled scramjet-powered free-flight vehicle from NASA's Wallops Flight Facility, Wallops Island, Virginia. The flight test was conducted under the Defense Advanced Research Projects Agency (DARPA)/ Office of Naval Research (ONR) Freeflight Atmospheric Scramjet Test Technique (FASTT) project. This latest flight was a culmination of a three-year, three-flight program to successfully demonstrate the feasibility of using ground-launched sounding rockets as a low-cost approach to hypersonic flight testing, and represents the world's first flight test of an air-breathing, scramjet-powered vehicle using hydrocarbon fuel.
Begun in late 2002, the FASTT project entailed the design and fabrication of three flight vehicles and a ground test engine rig to undergo wind tunnel testing. The first and second payloads were dubbed surrogate payload vehicles and matched closely the scramjet flight article, but lacked the internal flowpath and fuel system. They were designed as test rounds to validate vehicle subsystems, such as booster stack combination performance, fin sets, payload deployment mechanism, telemetry and trackability, and inlet shroud, before flight testing the more complicated scramjet flowpath, which was to undergo proof-of-concept testing in a wind tunnel prior to flight testing.
The first surrogate vehicle, SPV1, was launched aboard an unguided Terrier/Improved Orion two-stage solid rocket motor stack from Wallops Island on October 18, 2003, approximately 12 months after program initiation. This had the exact outer mold line of the eventual shrouded scramjet payload and contained full onboard instrumentation and telemetry suites. The vehicle was boosted to approximately and altitude, where it was deployed to free-flight, deployed its shroud at high dynamic pressure, and flew an un-powered trajectory to splashdown. All on-board subsystems worked flawlessly. The boost stage however inserted the payload at lower than desired flight speed, altitude, and flight path angle. The second surrogate vehicle, SPV2 was launched aboard the identical booster stack from Wallops Island on April 16, 2004, approximately six months after the first launch. After making slight trajectory corrections to account for launch rail effects, higher than anticipated drag, and actual booster performance, the payload was inserted nominally above and altitude. The full complement of subsystems were again proven out in flight on this successful flight test. The results of these two flight tests are summarized in a technical paper AIAA-2005-3297, presented at the 13th International Space Planes and Hypersonics Systems and Technologies Conference (see )in Capua, Italy.
The ground test engine hardware was fabricated over 18 months and underwent a four-month engine validation testing program in the ATK GASL freejet wind tunnel complex Leg 6, located in Ronkonkoma, New York. Ignition, fuel throttling, and engine operation were wrung out over a range of expected flight conditions. After a delay of two months to modify flight hardware based on ground test findings, the first powered vehicle, FFV1, was launched without incident, propelled to speeds of at altitude, roughly Mach 5.5. Over 140 inlet, combustor, and vehicle outer mold line pressure, temperatures, and vehicle accelerations as well as fuel pressure, timing feedback, and power systems monitoring were recorded. The vehicle executed the prescribed test sequences flawlessly for 15 seconds, before continuing on to splashdown into the Atlantic Ocean. Further details can be found in the technical paper AIAA-2006-8119, presented at the 14th International Space Planes and Hypersonics Systems and Technologies Conference, in Canberra, Australia.