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 Earths 
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 
Earths 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.

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