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Berlin

A HYDROGEN-powered aeroplane could take to the air by the end of the century.
The plane, which is being developed by engineers at Daimler-Benz Aerospace
Airbus (DASA), will eliminate carbon dioxide emissions and produce less
pollution from nitrogen oxides than conventional aircraft.

Aircraft manufacturers have experimented with hydrogen, which is lighter than
conventional fuel, in the past. In 1956, the US military successfully flew a
Canberra bomber on hydrogen, although the plane needed conventional fuel to take
off. And in the 1980s, Russian researchers converted a Tupolev 155 to run on
natural gas or hydrogen.

The German project, however, is the first to redesign the combustion chamber
of the engine in order to reduce emissions of nitrogen oxides. Engineers at the
University of Aachen created a “micro-mixing” system to replace the standard
fuel nozzles. Hydrogen enters the combustion chamber through tiny pores,
creating thousands of “flamelets”, says Friedemann Suttrop, a professor of
aeronautics at Aachen. Suttrop says the system achieves a more complete mixing
of air and fuel, resulting in lower combustion temperatures and lower emissions
of nitrogen oxides.

Suttrop and his colleagues have installed the new combustion chambers in a
small turbine engine, the auxiliary power unit from an Airbus 320. In tests
carried out over the past few months, emissions of nitrogen oxides were cut by
up to 70 per cent compared with conventional fuel.

The next step, says Suttrop, will be to convert the engines of a Dornier 328
aircraft. This is planned as a joint project with Tupolev, Pratt & Whitney
and Dornier, and is supposed to fly by the year 2000. DASA has already carried
out wind tunnel tests with a model, but the project is awaiting funding from the
German government.

Ian Poll, head of Britain’s College of Aeronautics at Cranfield University
near Milton Keynes, says the German project still does not solve the two biggest
problems of hydrogen use. “The volume of hydrogen is ridiculously large, and it
presents horrendous safety problems,” he says.

Liquid hydrogen fuel requires four times as much storage space as
conventional fuel. If the Dornier 328 is converted to hydrogen, additional fuel
tanks will have to be hung from its wings. These must be insulated with vacuum
chambers to keep the fuel cool. But DASA engineers say that hydrogen weighs less
than conventional fuel, allowing converted aircraft to carry up to 25 per cent
more payload.