Zero Emission Hyper Sonic Transport
ZEHST stands for Zero Emission High Speed Transport ( German: Zero-emission high-speed aircraft ). It refers to a 18 June 2011 presented by EADS at the Paris Airshow study for a four- supersonic fast passenger aircraft, which will operate without negative greenhouse gas balance from the 2050s years. The transport capacity is given as 50 to 100 passengers, the range should be at least 9600 km (London- Tokyo).
Propulsion system and flight profile
Special feature of the design is the design of the aircraft with three different drive systems: are two jet engines for the start and the climb to 5 km altitude are used; then two hydrogen-powered and entrained liquid oxygen rocket engines were ignited that would bring the aircraft to an altitude of 23 km and a flight speed of Mach 2.5, so that the two ramjet engines can be ignited as the main drive, which inherently require a very high inflow.
The rocket engines so close the gap between the optimal operating range of the jet engines and the minimum speed of the main drive. This will enable the use of space-saving and efficient jet engines for takeoff and landing, while the ramjet engines can still be designed for efficient operation at high speeds.
The ramjet engines also use hydrogen as a fuel, but burn it (as opposed to the rocket engines ) with the atmospheric oxygen. The main engines are to bring ZEHST then to its final cruising speed of Mach 4.0 ( 4,100 km / h in the corresponding height ) and cruise altitude of 32 km.
To end the trip flight, ramjet engines to be shut down and unpowered glide ZEHST to an altitude of 10 km, so that it reduced its speed back into the subsonic range. In order to ensure a safe landing, the jet engines would then be re-started.
Claim of zero emissions
ZEHST is to use three different fuels: bio-kerosene for the operation of jet engines, liquid hydrogen for the operation of rocket engines and ramjet engines, and to a lesser extent liquid oxygen for rocket engines. Hydrogen and oxygen burn to pure water and can be recovered electrolytically from water, which requires electrical energy. The study aims that the drive would be CO2 neutral when the power would be gained from renewable sources.
The bio-kerosene is to be obtained from renewable raw materials, and only as much carbon dioxide ( CO2) release, as it has bound at its birth before. The balance sheet is therefore also CO2 neutral, as long as the time spent on the production of energy was also obtained from renewable sources.
Disregards the fact that emissions do not only relate to CO2, but any kind of transmission of disturbances in the environment - for example, this can also noise or that be during the combustion at high altitude water released.
Further studies are already underway to operate and conventional jet aircraft with bio-kerosene, what the unique selling point " zero emissions " further into question.