New Look at Stealth

"Stealth" aircraft are designed to confuse radar. The aircraft's shape and special paint absorb radio waves, reducing the radar signature to levels indistinguishable from that of a bird in flight.
Multiplicity is central to U.S. military plans for future generations of unmanned air vehicles (UAVs). A large number of low-cost UAVs will be used in wartime and surveillance operations, with any individual aircraft in this fleet being replaceable. If one aircraft malfunctions or is brought down by hostile fire, the network of other UAVs must be able to "self-heal" by altering the path of inter-craft communication, and continuing to send uninterrupted transmissions.
To make fleets of such small unmanned aircraft feasible, however, the cost of replacement for any one UAV must be as small as possible. This means conventional stealth technology is cost-prohibitive for these craft. Designers are working on new methods of masking the radar trail, thermal signature, and sound emitted by small aircraft.
Data must be transmitted between the UAV and back to a command base. To make data interception by an enemy more difficult, these UAVs must have the ability to precisely control and rapidly change the power, direction, and frequency of signals being transmitted.
The Army's Unmanned Combat Armed Rotorcraft (UCAR) program is considering these design elements for helicopters, which must be able to hover at relatively low altitudes over a battlefield or surveillance area without being detected. The distinctive sound from rotor blades can be reduced by half with a design eliminating the smaller tail rotor, but the sound must be reduced further to make these craft feasible in practice.
Plans for future ground vehicles must meet similar goals. A new design for much quieter hybrid electric engines is expected to make tanks and other wheeled or tracked vehicles more stealthy.