EADS has further detailed a concept for a ramjet-powered high-speed aircraft which would cruise at Mach 4 and cut the Tokyo-Los Angeles journey to as little as 2h 20min.

It is undertaking a feasibility study into the zero-emission high-speed transport (ZEHST) concept, an aircraft which would sequentially use three different engines in order to make the transition to and from the near-hypersonic regime.

The manufacturer maintains that a demonstrator would be possible post-2020, although EADS chief Louis Gallois stressed at a seminar ahead of the Paris air show that the company was emphasising its technological capabilities rather than launching a project.

EADS ZEHEST hypersonic concept

EADS showed a concept design with delta wings, twin vertical fins, twin underwing ramjets and rear-mounted cryogenic rockets and turbofans. It also featured helium, hydrogen and oxygen tanks running the rear two-thirds of the fuselage.

Using the turbofans the aircraft would depart from a regular runway, then accelerate into the supersonic regime with rocket engines before the ramjets took over.

EADS chief technical officer Jean Botti said the use of the rockets was necessary to bridge the void between subsonic cruise at Mach 0.8 and the ramjet ignition zone at around Mach 2.

"You can't do that directly," he said. "But you don't need big rocket engines."

He stressed that the ramjet engines were also relatively simple to manufacture. "We're not saying it's cheap," Botti said, but he did point out that the necessary components were not "oversized".

The aircraft would fly at an optimum cruise speed at or above Mach 4, at an altitude of 105,000ft (32,000m).

It would then enter a glide descent until it reached a height at which subsonic engine control was again required, at which point the turbofans would re-ignite. Loiter, approach and touchdown phases would be conventional.

Botti said the aircraft would probably function as a large business transport. EADS indicated that it would accommodate around 60 passengers.

EADS said the study, which has attracted Japanese interest, is sponsored by the French civil aviation administration DGAC, and added that it formed part of its Flightpath 2050 initiative to explore potential future aviation concepts.

Among the other futuristic proposals put forward by EADS at the seminar was an all-electric transport, designated Voltair, which would use a lightweight, low-drag airframe fitted with lithium air batteries as the "most promising possibility" for energy storage.

It would carry liquid nitrogen tanks for coolant and use a superconducting rear-mounted engine. Botti said a definition study was at an "early stage".

EADS and partners carried out the maiden flight of a Diamond Aircraft HK36 Dimona fitted with a serial hybrid propulsion system - backed by a battery motor - on 8 June, at Wiener Neustadt in Austria, and performed several circuits of 30-40min duration.

Source: Flight Daily News