Jim Cast Headquarters, Washington, DC May 29, 1997 (Phone: 202/358-1779) David Morse Ames Research Center, Mountain View, CA (Phone: 415/604-4724) RELEASE: 97-113 THERMAL MATERIAL PERFORMS WELL DURING FIRST FLIGHT TEST A new thermal protection material designed to prevent spacecraft from burning up during reentry into EarthÕs atmosphere performed extremely well during its first flight test. The ultra-high temperature ceramic material may someday revolutionize the approach that engineers take to the design and protection of aerospace vehicles. A large amount of data on the thermal performance of the new material was collected on May 21 when a Mk 12A reentry vehicle blasted off from Vandenberg Air Force Base, near Lompoc, CA, at 4:27 a.m. EDT aboard a U.S. Air Force Minuteman III missile. The reentry vehicle, equipped with a 0.141-inch radius nose tip made from the new ceramic material, took an approximately 30-minute, 4,200-mile ride. Once out in space, the reentry vehicle was released, returning through Earth's atmosphere at blistering speed to a watery impact in the Kwajalein missile range of the Pacific Ocean. The sharp nose tip was instrumented with five heat sensing devices designed to provide information on how well the new ceramic material stood up to the burning temperatures of reentry. NASA engineers report that data was collected right up to the moment of splashdown. "This was just the first data-gathering flight test for this new material," said Joan Salute, project manager for the mission located at NASA's Ames Research Center, Mountain View, CA. "However, initial results suggest that it was a complete success. After extensive data analysis, we should have good information on the potential of this ultra-high temperature ceramic material to support a radical new concept in aerospace vehicle design -- the use of hypersonic sharp leading edges." This first test flight -- authorized only last December -- was accomplished in less than six months at a cost to NASA of $1.1 million. Plans for additional flights currently are under discussion. The potential benefits to be derived from the use of sharp leading-edge designs for spacecraft and transatmospheric vehicles are tremendous. Sharp-body designs offer reduced drag, thereby providing substantial savings in the cost per pound expended to put objects into orbit. In addition, they provide a greatly enhanced lift-to-drag ratio, enabling what is called cross-range capability. This means that spacecraft and transatmospheric vehicles can reenter EarthÕs atmosphere from any orbit and land at any location, unlike present blunt body vehicles. Finally, sharp leading edges minimize the number of free electrons that interfere with radio frequency transmissions and cause the communications blackout associated with the reentry of blunt body vehicles. The history of leading edge design is instructive. In the 1940s, aircraft routinely featured wings with sharp leading edges since that configuration was found to reduce drag at supersonic velocities (above the speed of sound, Mach 1, approximately 740 mph at sea level). However, with the coming of hypersonic flight (Mach 5 and faster) in the 1950s, the buildup of heat on the sharp leading edges of vehicle wings was so severe that available materials tended to burn up and their leading edges became blunted. Engineers took their cue from this natural blunting process in addressing the problem. "All along, Mother Nature was trying to tell us how to deal with this situation," said Paul Kolodziej, lead engineer for the project at Ames. "Engineers realized that if they blunted the leading edge themselves in the design process, this would move the shock wave created during hypersonic flight forward and out, away from the vehicle, creating an air pocket in front of it." This air absorbs much of the heat associated with reentry, preventing the leading edge from becoming so hot and melting. "Because these new ceramic materials operate at ultra-high temperatures, we can now build sharp leading edges that don't melt during reentry along trajectories such as those flown by the Space Shuttle," Kolodziej said. Blunt body design remains the norm today. In fact, it was the blunt body concept, originally developed at Ames by the late H. Julian Allen, that enabled development of space vehicles capable of withstanding the rigors of reentry. The problem is that blunt body vehicles have high drag and are not efficient. They therefore require large and expensive propulsion systems that impose a severe penalty in terms of cost, capability and performance. Developing an approach that permits the safe use of sharp leading-edge configurations for vehicles flying at hypersonic speeds holds the promise of yielding huge benefits. The key to achieving that payoff is the development of highly efficient thermal protection materials like those currently being evaluated by NASA engineers. The ultra-high temperature ceramic material that just completed its first flight test has already proven out in ground-based testing in the arcjet facilities at Ames. In fact, the materials were shown to be very stable at temperatures in the range of 1,700 - 2,800 degrees Celsius (3,092-5,072 degrees Fahrenheit) in the presence of high- velocity dissociated air, such as is encountered during conditions of reentry. They also have been shown to be resistant to thermal shock and fatigue failure and, hence, reliable for repetitive operation and use over multi-mission lifecycles. The development and testing of the new material is part of a joint program among NASA, Sandia National Laboratories and the US Air Force called Slender Hypervelocity Aerothermodynamic Research Probes, or SHARP. Additional information about the SHARP program can be obtained at the project's Ames web site on the Internet at URL: http://kauai.arc.nasa.gov/projects/sharp/sharp.html NASA's participation in the SHARP program is funded by the Headquarters Office of Aeronautics and Space Transportation Technology. The objective of the effort is to demonstrate the viability of sharp leading edges for space vehicles and possible future transatmospheric passenger aircraft that may have the capability to fly out of Earth's atmosphere and into the fringes of space and back. The SHARP program is a key element supporting NASA's overall mission to expand the nation's frontiers and capabilities in the aeronautics and space domain. -end-