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"Mach Number" was named after the Austrian physicist Ernst Mach. Mach 1 is the speed of sound, which is approximately 760 miles per hour at sea level. An airplane flying less than Mach 1 is traveling at subsonic speeds, faster than Mach 1 would be supersonic speeds and Mach 2 would be twice the speed of sound.

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X-43AScramjet Technology banner

NASA's X-43A is a hypersonic, scramjet-powered research aircraft.
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 NASA's X-43A scramjet Pegasus booster rocket ignites to send the X-43A on its record setting flight on Nov. 16, 2004. NASA photo

It's Official. X-43A Raises the Bar to Mach 9.6
Guinness World Records recognized NASA's X-43A scramjet with a new world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7,000 mph. The X-43A set the new mark and broke its own world record on its third and final flight on Nov. 16, 2004.

In March 2004, the X-43A set the previous record of Mach 6.8 (nearly 5,000 mph). The fastest air-breathing, manned vehicle, the U.S. Air Force SR-71, achieved slightly more than Mach 3.2. The X-43A more than doubled, then tripled, the top speed of the jet-powered SR-71.

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View QuickTime Movies:
X-43A/Pegasus Launch: 2.6 Mb | 5 Mb | 7.3 Mb | 12 Mb
B-52B Takeoff: 1.6 Mb | 3.1 Mb | 4.6 Mb | 7.5 Mb
Getting Ready for Mach 10: 3.2 Mb | 6 Mb | 8.9 Mb | 14.5 Mb

 X-43A title graphic
X-43A News Release
NASA's X-43A Scramjet Breaks Speed Record
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 B-52B mothership
X-43A Scramjet Readied for Mach 10 Flight
NASA's Hyper-X Program is ready for its greatest challenge - flying the "scramjet"-powered X-43A at nearly 10 times the speed of sound.
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 Infrared image of Mach 6.8 X-43A flight.
Mach 10 Meteor
X-43A scramjet flight is risky business.
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 X-43A engineer Randy Vorland
X-43A Engineer Randy Voland
Enthusiasm for flight propels researcher's interest in X-43A
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 Laurie Marshall, at work as NASA Dryden's chief engineer for the third flight of the hypersonic X-43A research vehicle.
X-43A Engineer
NASA Dryden's Laurie Marshall explores hypersonic flight.
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 X-43A research Zane Pinckney
From the Start
NASA Researcher Involved in X-43A Flight Program Since its Beginning
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 B-52 launch aircraft carrys the X-43A
Final X-43A Vehicle Checks Out in Flight
NASA's third and last X-43A hypersonic scramjet research vehicle took to the skies today for a captive-carry flight.
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 Artist's drawing of X-43 in flight
NASA Hits the Mach
X-43A makes hypersonic history.
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X-43A Grabs Record
NASA receives official recognition from Guinness World Records.
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 X-43A Fact Sheet cover
X-43A Fact Sheet
X-43A flight makes aviation history.
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 X-43A's Pegasus booster rocket ignites.
Pegasus Ignition
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 X-43A carried by B-52B
B-52 in Flight with Stack
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 X-43A on the wing of the B-52B.
B-52B Takes Off
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