Stealth Technology
 
 
The F-117 reduces radar cross-section a number of ways.  One
method is by the extensive application of radar absorbent
material (RAM).  These plates of varying thickness are attached
to the F-117's conventional aluminum structure by epoxy adhesive,
not sprayed on as is often alleged.  RAM absorbs rather than
reflects incoming radar beams. 
 
The F-117's exterior paneling also makes it less observable. 
Flat or faceted surfaces are installed at angles greater than 30
degrees.  Computer simulations determined that such angles
reflect the radar's energy away from the source, instead of back
toward it, thus creating the minimum radar return. 
 
To further reduce the F-117's observability, the cockpit canopy
is coated with a gold film that lowers radar reflection.  All of
the Nighthawk's antennae and other protuberances are either
retractable or removable.  The aircraft's stealth qualities are
further enhanced by reductions in its infrared signature, noise
level, and visibility.  The F-117A is so hard to detect that
special reflectors are sometimes mounted on each engine
compartment to make tracking easier during peacetime.