A scramjets special design allows it to obtain oxygen from the air that flows through the engine.And it does so without letting the fast-moving air put out the combustion(燃烧) flames.However,a scramjet engine works properly only at speeds greater than five times the speed of sound.
A booster rocket(助推火箭)carried the Hyper-X to an altitude of about l00,000 feet for its test flight.The aircrafts record-beating flight lasted just 11 seconds;That brief journey on March 27 makes a major milestone on the way to a new breed of very fast airplanes, says Werner J.A.Dahm of the University of Michigan in Ann Arbor.In the future,engineers Predict,airplanes equipped with scramjet engines could transport cargo quickly and cheaply to the brink(边缘)of space.Such hypersonic jets could carry passengers anywhere in the world in just a few hours.
Out of the three experimental Hyper.X aircrafts built for NASA, only one is now left.The agency has plans for another 11-second hypersonic flight, this time at 10 times the speed of sound.
31 The Hyper-X broke the record because
A it was the first air-breathing jet plane.
B it flew along the equator.
C it traveled at the speed of sound.
D it reached a speed of about 5, 000 miles per hour,
32 What kind of engine did the Hyper-X use?
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