快猫短视频

AS IT returns to Earth, the space shuttle flies with all the grace of a
winged brick. But the spaceplanes of tomorrow should be a pilot鈥檚 dream, now
that NASA鈥檚 advisers are urging the agency to step up its research into a new
class of heat-tolerant materials. The materials should also bring dramatic
reductions in fuel costs.

The shuttle isn鈥檛 terribly aerodynamic because its nose and wing tips must be
thick鈥攕o that a shock wave forms in front of the craft, protecting it from
some of the friction of re-entry. Any thinner, and the shuttle would get
dangerously hot.

But a team at NASA鈥檚 Ames Research Center in Moffett Field, California, has
created a new class of ceramics based on the metals hafnium and zirconium that
can withstand repeated exposures to 2400 掳C
(see 鈥淏reaking the heat barrier鈥�, 快猫短视频,
30 August 1997, p 28).
The shuttle鈥檚 protective tiles begin to burn at 1400 掳C.

The new materials should allow the leading edges of future spaceplanes鈥� wings
and noses to be built with radii of just a few millimetres. 鈥淵ou can make space
vehicles look like supersonic aircraft,鈥� says Dan Rasky, a member of the Ames
team.

This will bring real improvements in handling and efficiency: spacecraft
could fly like planes on both ascent and descent, instead of blasting up like
rockets and falling down like inefficient gliders. This would greatly reduce
fuel costs.

Spacecraft designers are thrilled. 鈥淚 can鈥檛 say good enough things about it,鈥�
says Preston Carter of the Lawrence Livermore National Laboratory in California.
He has incorporated the materials into his designs for the Hypersoar, a
spaceplane planned to skip across the top of the atmosphere at ten times the
speed of sound.

NASA鈥檚 Advisory Council shares Carter鈥檚 enthusiasm, and has urged the agency
to make research into the new materials a high priority.