Aerospace giant EADS this week said it is looking to develop and ambitious commercial transport aircraft that can fly at speeds of about Mach 4 while having a limited impact on the environment.
The aircraft, called ZEHST (Zero Emission High Supersonic Transport), would be targeted at long-haul routes - like Tokyo-Paris or Tokyo-Los Angeles where it could make the flight in less than 2 hrs 30 min, EADS said.
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The company says the initial ZEHST propulsion system concept is based on using liquid hydrogen as the fuel and the first ZEHST demonstration aircraft could appear by 2020 though the company says any real airliners wouldn't fly till about 2040.
And you can see why. The ZEHST propulsion system itself sounds complicated as EADs says it involves "three types of engines are operated in sequence for the various flight phases of a long-range flight at hypersonic cruise speed."
The thrust required for the ZEHST's initial flight phase - beginning with the normal takeoff from a standard runway through to the initial cruise, the climb to 5km altitude and acceleration to Mach 0.8 - will be provided by two high-power, low-bypass turbojet engines without afterburners (reheat), that operate on biofuel.
Ignition and operation of two small liquid hydrogen / liquid oxygen-powered booster rocket engines followed by the ignition of a larger enable the aircraft's continued steep climb towards the cruising altitude and the acceleration through the transonic speed regime up to a speed of Mach 2.5. Once sufficient speed has been reached and an altitude of 23km attained, two airbreathing hydrogen-fuelled ramjets are employed for the aircraft's cruise flight at beyond Mach 4, the optimum Mach number in terms of fuel consumption, and at an altitude of up to about 32km, EADs stated.
For a short period of time during the steep rocket engine-powered climb and acceleration, ZEHST passengers would feel mild acceleration forces, not exceeding 1.2g, EADS noted. When landing, a gliding descent and deceleration to subsonic speed will be performed, followed by the re-ignition of the aircraft's turbojets at an altitude of 10km for the approach to a normal landing - with sufficient thrust output to allow the possibility of a runway go-around or diversion to another airport should it be necessary, EADs stated.
The company said it was basing most of the current research on the aircraft on tests with the Astrium spaceplane over the past five years. Astrium is a subsidiary of EADS that has been developing a business jet-like aircraft that could take off, fly into space and land conventionally from a standard airport runway.
"Such a new vehicle able to operate at altitudes between those of conventional aircraft (20km) and those of satellites (200km) could be used for various other applications and is a precursor for rapid 'point-to-point' transport vehicles or quick access to space - opening up previously unexplored territory," Astrium says on its Web site.
EADS presented its concept at the Paris Air Show this week.
NASA too has been at work on concept aircraft that have little environmental impact. The agency in April said four research teams would split $16.5 million to develop quieter, cleaner, and more fuel-efficient jets.
NASA said the money was awarded after an 18-month study of all manner of advanced technologies from alloys, ceramic or fiber composites, carbon nanotube and fiber optic cabling to self-healing skin, hybrid electric engines, folding wings, double fuselages and virtual reality windows to come up with a series of aircraft designs that could end up taking you on a business trip by about 2030.
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