Boston
DESPITE running way over budget on the International Space Station, NASA is
pressing ahead with plans to develop technology for a third-generation space
shuttle, even though it does not yet have a second-generation craft. The reason?
The agency wants an engine that will dramatically slash the cost of getting into
orbit, so that it can save money in future.
Late last month, the agency awarded contracts totalling $16 million to
aerospace companies to begin development of a new air-breathing engine for the
yet-to-be-designed craft. By burning air for a large part of the flight, the
spacecraft will not need to carry the heavy tanks of liquid oxygen that reduce
shuttle efficiency.
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A previous attempt to build an air-breathing spaceplane in the
1980s鈥攃alled the National Aerospace Plane鈥攆oundered. According to
Frank Sietzen of the National Space Society, this was because engineers tried to
build a full-size version with immature technology. This time, however, NASA is
starting development with scale models as it attempts to cut the cost of
reaching orbit by up to 99 per cent.
NASA is investing $900 million this year on its second-generation
shuttle, which it hopes will fly by about 2012. But like today鈥檚 shuttle, this
one will use solid and liquid rocket motors, rather than burning air. The agency
hopes the air-breathing shuttles will fly by around 2025.
NASA has learned much about hypersonic aerodynamics in experiments conducted
since 1996, says Craig McArthur, a project manager at the agency鈥檚 Marshall
Space Flight Center in Huntsville, Alabama. The next logical step, he says, is
developing a test model of an air-breathing engine, but they will need to use
advanced materials in parts likely to become very hot. 鈥淲e need to keep the
engine cool so it doesn鈥檛 melt,鈥� McArthur says.
Boeing, Aerojet and Pratt & Whitney have teamed up to design a
hydrocarbon-and-air burning engine able to run at 3 to 7 times the speed of
sound. In 2006, they will complete a scaled-down engine for wind-tunnel tests.
Their design will then compete with one in development at NASA鈥檚 Glenn Research
Center in Ohio. Only one design will be chosen for test flights in 2010.