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Image of the X-43A awaiting take-off of its carrier jet
According to the comic books, Superman could fly "faster than a speeding bullet." That's nothing. The SR-71 Blackbird set a jet speed record of Mach 3.2. That's more than three times faster than the speed of sound. The X-15 rocket plane set a record for winged vehicles with a speed of Mach 6.7. They're both slowpokes.

Image to right: The X-43A is also called the Hyper-X. Credit: NASA

NASA beat both of those records earlier this year with a new airplane called the X-43A. This plane is also known as the Hyper-X. In March 2004, the Hyper-X set a new record for air-breathing aircraft of about 5,000 miles per hour (mph). This is almost seven times the speed of sound. But, now, even that record has been left in the dust. In fact, the new record holder reached a speed almost as great as the records of the Blackbird and the X-15 put together. Now, that's fast.

In November 2004, the X-43A flew for the final time. It set a new speed record almost 10 times faster than the speed of sound. Early data showed the 12-foot-long unmanned plane reached about 7,000 mph. This is almost Mach 9.8. It reached an altitude of about 110,000 feet.

Image of the X-43A being accelerated by the Pegasus booster
Image to left: The X-43A is much faster than the speed of sound. Credit: NASA

The X-43A is the world's first hypersonic jet airplane. This means that it went faster than Mach 5. The X-43A uses a new technology called the scramjet engine. The term scramjet is short for supersonic-combustion ramjet. This means that the plane uses supersonic air from the atmosphere mixed with fuel to propel itself. Until now, the fastest planes have reached those advanced speeds with the help of rockets. Hyper-X planes, though, are air-breathing jets.

In normal turbojet engines, the compressor section (the fan blades) compresses the air to speed it through the engine at great speeds. That's what makes the plane move forward. In rockets, fuel and oxygen are combined and burned to create the blast of energy. In air-breathing vehicles, though, vent inlets on the outside of the plane scoop the air from outside. Because the X-43A is going so fast, the air is "rammed" into the engine. This gives the engine the name "ramjet."

Ramjet engines use a subsonic stream of air through the engine to push the aircraft at supersonic (above the speed of sound) speeds. When the air flowing through the engine stays at supersonic speeds, it's called a scramjet. Scramjets and ramjets need no moving parts in their engines. The thrust is created by rapidly forcing airflow through the engine. Since they don't have to carry oxygen for fuel (like rockets do), they weigh less. Another plus is that scramjets can be throttled back and flown more like an airplane. Rockets have a harder time of reducing the amount of thrust they create.

Image of the X-43A's carrier jet taking off
Image to right: A launch aircraft takes off with the X-43A. Credit: NASA

During the recent test flight, the X-43A was carried aloft by a B-52B launch aircraft. The X-43A was attached to a Pegasus booster rocket. This rocket was attached under one of the B-52B's wings. Once the B-52B reached the right height, it released the Pegasus rocket. This rocket then boosted the Hyper-X to its test speed. The X-43A then separated from the Pegasus, and used its scramjet engine for about 10 seconds of powered flight. When the engine shut down, the aircraft glided into the Pacific Ocean, according to plan. The Hyper-X is not reusable.

The November 16 flight was the third test of the X-43A. A June 2001 test ended in failure. The aircraft had to be destroyed when it began to fly off course. Scientists found that the problem was caused by the control system of the booster rocket.

Artist's rendition of the X-43A in flight
Image to left: The success of the X-43A has opened a door into the future of transportation. Credit: NASA

The Hyper-X was a great success. At the speed at which the X-43A flew, it could go from New York to Tokyo in under an hour. By not needing to carry an onboard supply of oxygen, a scramjet engine could help carry large payloads into space more efficiently. By turning theory into reality, NASA has opened a door into the future of transportation on this world and beyond.


Mach -- a number representing the ratio of the speed of a body (as an aircraft) to the speed of sound in a surrounding medium (as air)

subsonic -- of, relating to, or being a speed less than that of sound in air

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Published by NASAexplores