NASA has postponed this week’s launch of its HESSI solar flare probe while
experts work out why an experimental hypersonic aircraft launched on a similar
Pegasus rocket failed last weekend.
NASA had to destroy what could have been the world’s fastest jet aircraft,
the X-43a, just minutes before it was due to attempt a Mach 7 flight. The X-43a
is powered by an air-breathing jet engine called a supersonic combustion ramjet,
or “scramjet”. Instead of using compressor blades, a ramjet uses its speed to
compress oxygen from the atmosphere. A scramjet does this at supersonic speeds
and burns hydrogen fuel. But to reach such speeds, the X-43a has to sit on the
nose-cone of a modified Pegasus rocket, which is itself carried aloft by a B-52
bomber.
But the Pegasus careered off course after separating from the B-52, tumbling
end over end. NASA is now “working to determine if there are any associated
technical issues” between the X-43a failure and the Pegasus—from Orbital
Sciences of Dulles, Virginia—that will launch HESSI. Prior to the X-43a
incident, three larger Pegasus rockets have failed in the last 12 years.
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