Visitors were given a possible glimpse of the future at the Paris Air Show recently, when EADS presented a concept study for a highspeed transport system that harnesses the propulsion of liquid hydrogen, liquid oxygen, and biofuels.

Named ZEHST (Zero Emission High Supersonic Transport), the dynamic looking jet concept was on show at the event at Le Bourget airport in north Paris, France.

EADS is a global leader in aerospace, defence and related services comprising Airbus, Astrium, Cassidian and Eurocopter. According to a company press release, the future commercial transport vehicle is intended to fly long-haul routes – for example Tokyo-Paris or Tokyo-Los Angeles – in less than 2 hours and 30 minutes, while having a very limited impact on the environment and being operated as a standard aircraft.

ZEHST demonstrators are planned for the end of the decade, to be followed by development towards an operational vehicle. Numerous technological challenges need to be mastered so that future high-speed commercial transport systems can achieve the required performance while also meeting tomorrow’s environmental constraints. Studies have to identify how requirements and objectives can be aligned with technical aspects.

Fuels
An initial ZEHST propulsion system concept based on liquid hydrogen as the main fuel has been conceived as the first step towards a basic reference solution.

Three types of engines are operated in sequence for the various flight phases of a long-range flight at hypersonic cruise speed. It’s thought that the thrust required for the ZEHST’s initial flight phase 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 one (derived from the types used in the Ariane commercial launch vehicle), 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.

The type of fuel to be used will eventually be selected in the light of its environmental performance, but also its production and distribution, while also addressing energy management and the concept’s acceptance by future passengers, crew, and the public.

The display at the Paris Air Show really was just a glimpse of the future, however; while demonstrators are planned for the end of the decade, it’s unlikely we’ll see the fully-fledged vehicle for a few years yet. Jean Botti, Chief Technical Officer of EADS, said in the company’s statement, “We are on a very early stage with this research programme. First series planes flying with technology resulting from this concept will not fly before 2040.”

Feasibility
EADS Innovation Works and Astrium – in partnership with the French national aerospace research laboratory ONERA – launched the ZEHST feasibility and systems study sponsored by France’s Directorate General for Aviation (Direction Générale de l’Aviation Civile – DGAC).

ZEHST draws on know-how from Astrium’s suborbital spaceplane project, and is one of the projects incorporated in EADS Innovation Works’ eCO2avia activities – which also include such efforts as demonstrating the feasibility of using biofuels and electric power for aviation.

As recently as June 2010, EADS showcased the world’s first flight of an aircraft powered by pure biofuel made from algae. Then, the Diamond DA42 New Generation aircraft demonstrated that the higher energy content of the algae biofuel enabled the fuel consumption to be 1.5 litres per hour lower when compared to conventional JET-A1 fuel – while maintaining equal performance. The company described the demonstration flights as ‘an exciting milestone’ in its research.