Hypersonic
Hypersonic is an aerodynamics term referring to speeds that are highly supersonic. At first the term had no strict definition, but in the 1970s it generally came to refer to speeds of Mach 5 and above.
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2 Recent progress 3 See also 4 External links |
History
During and after World War II, tremendous amounts of time and effort were put into researching high-speed jet- and rocket-powered aircraft. Fast planes had proven their usefulness in that conflict, and development continued afterward. Supersonic flight was attained in 1947 by the Bell X-1, and by the early 1960s, the 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 American X-15 and other rocket-powered spacecraft, the speeds of operational aircraft have remained level since that time, generally in the range of Mach 1 to Mach 2.
In the realm of civilian air transport, the primary goal has been to move large numbers of passengers point-to-point cheaply rather than quickly. Because supersonic flight requires significant amounts of fuel, airlines have favored subsonic jumbo jets rather than supersonic transports. The Concorde, which carried about 100 people at Mach 2, had always cost more to operate than the airlines charged fliers. In the military arena, the goal was to create aircraft that would be maneuverable with low radar or infrared signatures, which weighed against hypersonic aircraft as they are less maneuverable and have a high infrared signature.
Hypersonic flight concepts haven't gone away, however, and low-level investigations have continued over the past few decades. At the present time, the US military and the National Aeronautics & Space Administration (NASA) have formulated a "National Hypersonics Strategy" to investigate a range of options for hypersonic flight. Other organizations around the world from places such as Australia, France, and Russia have also gone forward with significant research.
In the US, the different organizations have different agendas, but they have all realized they need to coordinate their activities to make progress. The Army, for example, wants to develop hypersonic missiles that can attack mobile missile launchers before they leave their launch site and disappear. NASA wants to develop new, economical, reusable launch vehicles. The Air Force is interested in a wide range of hypersonic systems, from hypersonic air-launched cruise missiles to orbital spaceplanes, that the service believes could transform it into a true "aerospace force".
In recent years, significant progress has been made in the development of hypersonic technology, particularly in the field of supersonic-combustion ramjet, or scramjet, engines. While American efforts are probably the best funded, the first to demonstrate a scramjet working in an atmospheric test was a shoestring project by an Australian team at the University of Queensland. The University's HyShot project demonstrated scramjet combustion in 2002. This demonstration was somewhat limited, however; while the scramjet engine "worked", the engine was not designed to provide thrust to propel a craft.
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. NASA's Marshall Space Propulsion Center has introduced an Integrated Systems Test Of An Air-Breathing Rocket (ISTAR) program, prompting Pratt & Whitney, Aerojet, and Rocketdyne to join forces for development.
To coordinate hypersonic technology development, the various factions interested in hypersonic research have formed two integrated product teams (IPTs): one to consolidate Army, Air Force, and Navy hypersonic weapons research, the other to consolidate Air Force and NASA space transportation and hypersonic aircraft work. Current funding levels are relatively low, no more than US$8585 million per year in total, but are expected to rise.
At present, the most advanced US hypersonics program is the US$250 million NASA Langley Hyper-X X-43A effort, which will fly small test vehicles to demonstrate hydrogen-fueled scramjet engines. NASA is working with contractors Boeing, Microcraft, and the General Applied Science Laboratory (GASL) on the project.
Each X-43A test vehicle will be carried to operational speed and altitude on the nose of an Orbital Sciences Pegasus air-launched booster, to be dropped from a B-52 airplane.
The first flight in June 2001 failed when the vehicle and rocket spun out of control about 11 seconds after the drop from the B-52. The vehicle was destroyed by the range safety officer, and it crashed into the Pacific Ocean. NASA attributed the crash to several inaccuracies in data modeling for this test, which led to a deficient design for the control system of the particular Pegasus that was utilized.
The second X-43A test was successfully carried out on March 27, 2004, attaining Mach 7 speeds. A third planned flight is meant to reach Mach 10.
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:
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.
Several scramjet designs are now under investigation with Russian assistance. One of these options or a combination of them will be selected by ONERA, the French aerospace research agency, with the EADS conglomerate providing technical backup. The notional immediate goal of the study is to produce a hypersonic air-to-surface missile named "Promethee", which would be about 6 meters (10 feet) long and weigh 1,700 kilograms (3,750 pounds).Recent progress
Hypersonic development efforts are also in progress in other nations. The French are now considering their own scramjet test vehicle and are in discussions with the Russians for boosters that would carry it to launch speeds. The approach is very similar to that used with the current NASA X-43A demonstrator.