Volume 8, Number 6     November/December 2000

Materials May Allow Spacecraft Design Change

New thermal protection materials that may radically change the design and performance of future aerospace vehicles were tested recently. The materials may also overturn an age-old tenet of aerodynamics: that only blunt-body aerospace vehicles can survive the searing temperatures created as the vehicles tear through the atmosphere.

SHARP-B2 reentry vehicle before flight with two of the four UHTC strakes visible. Photo provided by NASA Ames Research Center.

"We believe these materials may lead to a radical new concept in aerospace vehicle design and performance —the use of sharp leading edges on hypersonic vehicles," said Joan Salute, project manager for the mission at NASA Ames Research Center at Moffett Field, California. "The potential increase in spacecraft maneuverability is like going from a semi-trailer to a Ferrari." Salute said the material showed exceptional performance during its first flight test in 1997 and during tests in Ames' arcjet facilities.

Sharp leading edges offer several advantages over the blunt-body design currently in use. They could allow a Space Shuttle or crew return vehicle to maneuver in space more like an airplane and potentially allow astronauts to return to Earth from anywhere in orbit. They also might eliminate the electromagnetic interference that causes the communications blackouts that plague reentering blunt-body space vehicles. Reducing the amount of drag could lead to a reduction in propulsion requirements. In addition, planetary probes could make use of sharp-body technology for aerobraking and to maximize their maneuvering capability.

This research is part of the SHARP (Slender Hypervelocity Aerothermodynamic Research Probes) program, a joint effort among NASA, Sandia National Laboratories and the U.S. Air Force. It is funded by the Pathfinder Program at Marshall.

"Our goal is ultimately to transfer this technology to the aerospace industry for use in next-generation reentry vehicles," said Jeff Bull, chief engineer for the project at Ames. "SHARP-B2 should prove to be a key step in enabling future sharp body aerospace vehicles."

"Sharp leading edge technology is one of several technologies NASA is developing to help achieve its aerospace goals," said Michael Phipps, project manager of the Pathfinder Experiments Project at NASA Marshall Space Flight Center in Huntsville, Alabama. Phipps cited several areas that may benefit from this new technology, including safer and more reliable aerospace vehicles. In the long term, the technology also may reduce the cost of putting payloads into space, from thousands of dollars per pound to a few hundred dollars per pound, making access to space more affordable to a variety of markets.

The test was conducted by launching an Mk12A reentry vehicle (RV) equipped with four 5.1-inch-long strakes, or sharp leading edges. Each contained three Ultra High Temperature Ceramics (UHTCs), materials designed to prevent spacecraft from burning up during reentry into Earth's atmosphere.

After reaching an altitude of about 400 nautical miles, the RV was returning through Earth's atmosphere at blistering speed. It was slowed by a parachute and landed in the Pacific Ocean. Sensors in the strakes measured how closely performance matched pre-flight calculations, and at what temperature the materials began to melt.

One pair of strakes was retracted just before reaching temperatures high enough to cause the material to begin ablating, or burning off. The other pair was retracted shortly after ablation began, at a temperature of nearly 5,100 degrees Fahrenheit. NASA engineers collected data throughout the 23-minute flight, up to the moment of splashdown.

For more information, contact June E. Malone at Marshall Space Flight Center. Call: 256/544-7061, E-mail: june.malone@msfc.nasa.gov Please mention you read about it in Innovation.

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