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17 November 2004

NASA Scramjet Breaks Speed Record

Flight a major step toward reducing spaceflight payload costs

By Cheryl Pellerin
Washington File Staff Writer

Washington -- NASA's X-43A scramjet-powered research vehicle broke the air speed record November 16 and showed that an "air-breathing" engine can fly at nearly 10 times the speed of sound.

Preliminary data indicate that the revolutionary supersonic combustion ramjet (scramjet) engine worked successfully at about Mach 10 -- more than 11,000 kilometers per hour -- as it flew at an altitude of nearly 34,000 meters.

The flight took place in restricted airspace over the Pacific Ocean northwest of Los Angeles. It was the fastest of three unpiloted tests in NASA's Hyper-X Program to explore an alternative to rocket power for space-access vehicles.

"This flight is a key milestone and a major step toward the future possibilities for producing boosters for sending large and critical payloads into space in a reliable, safe, inexpensive manner," said NASA Administrator Sean O'Keefe.

After the launch of the Pegasus booster rocket from NASA's B-52B launch aircraft at 12,192 meters, the X-43A separated from the booster and accelerated on scramjet power to its intended speed. The mission originated from NASA's Dryden Flight Research Center at Edwards Air Force Base in California.

Researchers believe these technologies may someday offer more airplane-like operations and other benefits for space travel compared to traditional rocket systems. Rockets provide limited throttle control and must carry heavy tanks filled with liquid oxygen needed for fuel combustion.

Air-breathing engines like the X-43A scoop oxygen from the air as they fly rather than carrying oxygen. This weight saving could be used to increase payload capacity, increase range or reduce vehicle size for the same payload.

Researchers have worked for decades to demonstrate scramjet technologies, first in wind tunnels and computer simulations, and now in an airplane in flight. Ultimate applications include future hypersonic missiles, hypersonic airplanes, the first stage of two-stage-to-orbit reusable launch vehicles and single-stage-to-orbit reusable launch vehicles.

The first X-43A flight attempt in June 2001 failed when the booster rocket went out of control and the "full stack" -- the booster rocket and X-43A combination -- was destroyed by ground controllers.

The second attempt at Mach 7 in March 2004 succeeded and made aviation history with the first flight of a scramjet-powered airplane at hypersonic speeds -- speeds greater than Mach 5 or five times the speed of sound.

The eight-year, $230 million NASA Hyper-X program is a high-risk, high-payoff research program. NASA's Langley Research Center in Hampton, Virginia, and the Dryden Flight Research Center, jointly conduct the program.

In a NASA television interview immediately after the successful flight, NASA Research Missions Director J. Victor Lebacqz discussed the next steps in supersonic flight.

"We've got a lot of data to look at now," Lebacqz said. "We've had two successful flights and a lot of tunnel data that led up to them. We'll get together with our industry partners, who also were critical to this, work our way through what we think we've learned, see what the next steps might be, and talk about some foundational technologies we might want to do," he added.

Hyper-X research began with conceptual design and wind tunnel work in 1996. Three unpiloted X- 43A research aircraft were built. Each 3.6-meter-long, 1.5-meter-wide lifting body vehicle was designed to fly once. The vehicles were identical in appearance but engineered with slight differences to simulate variable engine geometry based on the speed at which individual vehicles were designed to fly.

Mach numbers, named for Austrian physicist Ernst Mach, describe the speed of a body relative to the speed of sound. Mach 1, the speed of sound, is about 1,223 kilometers per hour at sea level. An airplane flying less than Mach 1 is traveling at subsonic speeds, faster than Mach 1 is traveling at supersonic speeds. Mach 2 is twice the speed of sound at sea level.

The first and second vehicles were designed to fly at Mach 7 and the third at Mach 10. At these speeds, the shape of the vehicle forebody serves the same purpose as pistons in a car by compressing the air as fuel is injected for combustion. Gaseous hydrogen fuels the X-43A.

The third X-43A vehicle also had added thermal protection for the Mach 10 flight because it experienced heating roughly twice that of the Mach 7 vehicle. Reinforced carbon-carbon composite material was added to the leading edges of the vehicle's vertical fins to handle the higher temperatures.

In March, at Mach 7, the X-43A traveled nearly 8,000 kilometers per hour. Guinness World Records has recognized the accomplishment and is listing the flight on its Web site and in its next book of records.

A ramjet-powered missile that achieved slightly over Mach 5 held the previous record. The highest speed attained by a rocket-powered airplane, NASA's X-15 aircraft, was Mach 6.7. The fastest air-breathing crewed vehicle, the SR-71, achieved slightly over Mach 3. The X-43A more than doubled the top speed of the jet-powered SR-71.

Information about the Hyper-X Program is available at http://www.nasa.gov/missions/research/x43-main.html

(The Washington File is a product of the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)

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