August 06, 2012

Hypersonic Engines - Reaction Sabre and Airbus Continuous Detonation Wave Engines

New Scientist - Reaction Engines UK is developing the Sabre hydrogen-and-air-burning engine. It is designed to reach orbit in a future satellite-launching spaceplane called Skylon, and may be used suborbitally in a point-to-point Mach 5 passenger aircraft.

These hypersonic planes for commercial aviation would be about 25-40 years away. They could appear earlier for unmanned, space and military purposes. It would be easier (less certification and testing) to make them work for missiles. Missiles are one time use. Next would be hypersonic (but reusable) UAVs.

There is also a continuous detonation wave engine (16 pages) that is being developed in a joint venture between MBDA Missile Systems, the aerospace firm EADS, which owns Airbus, and the Lavrentyev Institute of Hydrodynamics in Novosibirsk, Russia.

Detonation wave engines, thanks to their more efficient thermodynamic properties, are expected to exhibit a higher level of performance than more conventional propulsion system that rely on constant-pressure combustion processes. Nevertheless, it still has to be proved that this advantage is not superseded by the difficulties which could be encountered to practically define a real engine and to implement it in an operational flying system. In that respect, continuous detonation wave principle appears less challenging than the pulsed detonation process and should lead to the development of more efficient propulsion systems, even if such radical adaptation of the overall engine concept and of the vehicle architecture would be necessary. During past years, MBDA performed some theoretical and experimental works, mainly in cooperation with the Lavrentyev Institute of Hydrodynamics in Novosibirsk. These studies aimed at obtaining a preliminary demonstration of the feasibility of a Continuous Detonation Wave Engine for air-breathing and rocket application. Compared to a Pulsed Detonation Engine,this design allows an easier operation in reduced-pressure environment and an increase in engine mass flow rate and thrust-to weight ratio.

The collaborators are attempting to advance that still further into the hypersonic realm with what they are calling a "continuous detonation wave" engine. In this, they modify the fuel injection pressure several thousand times per second, rather than in slower pulses, to create ignition in the form of a continuous series of shock waves which combust the fuel more fully and can generate thrust levels up to Mach 5 speeds.

Such blisteringly fast suborbital flights for ordinary passengers are still some way off, of course, but these recent engine-test successes have prompted the UK's science minister David Willetts to urge the European Aviation Safety Agency to look into certifying European Union airports for use by spaceplanes. "It's not that EASA has been hostile to spaceplanes," Willetts told New Scientist. "It's just that it has no regulatory regime."

Meanwhile, Virgin Galactic, which already has plans for spaceplane-based suborbital tourism, also has ambitions for high speed point-to-point travel that actually involves entering orbit. "Point-to-point travel would be the most amazing thing," says Julia Tizard, deputy vice president of operations at Virgin Galactic in Mojave, California. "An orbit takes 90 minutes, so you could leave the UK and have lunch in Australia in 45 minutes."

Continuous Wave Engine Status

Since a few years, MBDA France leads R and T works in cooperation with the Lavrentyev Institute of Hydrodynamics on the Continuous Detonation Wave Engine. The mixtures used in the different experiments were mainly GH2 – LO2 or LHC – GO2. The goals of those experiments were to address some key technology points in order to be able to evaluate the global interest of an engine using TDW for the combustion process.

It was found that such engine could deliver impressive thrust in a very small package (275 daN for a 50 mm (internal diameter) and 100 mm long, kerosene – oxygen engine) and that could be increased with the use of a diverging nozzle. Due to the geometry of the combustion chamber, a plug or aerospike nozzle seems to be the best design, the thrust vectoring capability of this engine (with the local change of the mass flow rate) being a way to solve the problem of attitude control. The heat fluxes are very high but located mostly near the injection wall. This point will help the gasification of the liquid component injected inside the combustion chamber. The transverse flow velocity could also help the mixing of the fresh products, but also the mixing of the fresh mixture with the detonation products. Some preliminary tests have been performed to evaluate the capability of C/SiC composite materials to sustain the very severe mechanical environment generated by the rotating detonation waves.

Beyond these first steps, a full scale demonstrator has been designed and should be tested within the next years.

Reaction Engines Lapcat A2

REL's SABRE engine and lightweight heat exchanger technology can enable to Mach 5 cruise. REL is presently engaged on an EU 50% funded project as part of Framework 6. This study is to examine the propulsion concepts and technologies required

" reduce long-distance flights, e.g. From Brussels to Sydney, to less than 2 to 4 hours. Achieving this goal intrinsically requires a new flight regime for commercial transport with Mach numbers ranging from 4 to 8."

Wikipedia no the Reaction Engines A2

General characteristics

Capacity: 300 passengers
Length: 143 metres (469 ft)
Wingspan: 41 m
Wing area: 900 m2
Max. takeoff weight: 400,000 kg
*Fuel capacity:198 tonnes liquid hydrogen


Cruise speed: Mach 5.2 (6,400 km/h)
Range: 12,430 miles (20,000 km)
Specific fuel consumption: 0.86 lbf/lb·h at Mach 5 (40,900 m/s - 4,170 seconds), 0.375 lbf/lb·h at Mach 0.9 (96,000 m/s - 9,600 seconds)
Lift to drag ratio: 11.0 at 5.9 km, Mach 0.9, 5.9 at 25 km Mach 5
Noise: 101 dBa at 450m lateral

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