TIME: Almanac 1993/TIME Almanac 1993.iso/time/110689/p83

Text File | 1992-09-23 | 5.7 KB | 113 lines

                                                                                TECHNOLOGY, Page 83

Threats to the Old Magic


Will new stealth weapons make radar obsolete?

By Bruce Van Voorst


    Of all the weapons of modern warfare, none is more
venerable than radar. The seemingly magical technology that
enables planes, ships and artillery units to spot the enemy from
afar has made the difference between defeat and victory in many
a battle. In a Nova TV episode called Echoes of War, which was
shown on the Public Broadcasting System last week, radar was
hailed as the military's unsung hero of World War II. As
physicist I.I. Rabi once recalled, "Maybe we could have won it
without the atomic bomb . . . but without radar we could have
lost it."

    Yet for all its past glory, radar is facing its most
perilous assault ever. All the major military powers are working
on stealth technologies designed to defeat radar. The U.S. Air
Force's new B-2 Stealth bomber, for example, is supposedly
almost invisible to radar because its sleek shape and special
composite construction tend to absorb rather than reflect
electronic signals. The same techniques will soon be used to
introduce stealth missiles, ships, satellites and tanks.
Moreover, military designers have developed missiles and other
weapons that can zero in on electronic signals and thus destroy
the ships and planes carrying radar. Faced with these trends,
some Pentagon experts have raised a disturbing question: Is
radar becoming obsolete?

    The issue is of utmost importance to the U.S. armed forces.
Virtually all American warplanes use radar, and many costly
weapons systems, from the Navy's Aegis system to the Army's
Patriot missile, are heavily reliant on the technology. By one
estimate, about a quarter of U.S. military investment is radar
related. If heavy use of radar becomes questionable, the
Pentagon will have to rethink its whole strategy and allocation
of resources.

    The development of radar (short for radio detection and
ranging) applications in the U.S. stemmed from the accidental
discovery in 1922 that a ship moving between a radio
transmitter and receiver interfered with the signals. The
technology came into its own in World War II, when it progressed
rapidly from a crude early-warning system barely able to locate
ships and aircraft to a sophisticated electronic eye that can
spot the periscope of a submerged submarine. Radar works because
electronic signals bounce off objects, just as a voice is
reflected by walls or buildings. Radar transmits radio waves and
"listens" for an echo. The direction of the echo and the elapsed
time from transmission determine an object's location. Unlike
relatively slow sound waves, radio signals travel at the speed
of light and can circle the globe 7 1/2 times a second.
Therefore, radar can almost instantly spot targets at great
distances. Because it can see through clouds and at night, radar
is superior to all other sensors, including optical, infrared,
acoustic and magnetic.

    But radar has a serious drawback: its signal is a blazing
electronic beacon that can make the transmitter as much the
hunted as the hunter. "Like a flash light in a dark forest,
radar can spotlight certain trees," says Theodore Postol, an
electronics expert at the Massachusetts Institute of Technology.
"But everybody in the woods can see it."

    Many countries, including the Soviet Union, have an array
of antiradiation missiles that can home in on radar-equipped
ships or planes and destroy them. It was just such a missile,
fired by an Iraqi warplane, that nearly sank the U.S.S. Stark
in the Persian Gulf two years ago, killing 37 sailors. A study
by the General Accounting Office points out that the Pentagon
"has 15 radar (systems), costing over $10 billion, which are
vulnerable to ARMs." Says Thomas Amlie, a Defense Department
official: "Navy's Aegis wouldn't last a half hour in a real
war." No one is more aware of radar's vulnerability than the
troops. "Turn radar on," goes the saying on the front lines,
"and you're dead."

    But radar designers are working to overcome its inherent
weaknesses. Many systems try to avoid detection by transmitting
intermittently or changing the frequency of their signals
thousands of times a second. Another approach is "bistatic"
radar, in which the transmitter is separated from the receiving
"ears." For example, a land-based missile launcher may rely on
a radar receiver, but the transmitter may be some distance away.
Thus even if an enemy plane detects and destroys the
transmitter, the receiver and the missile launcher are not
knocked out.

    Radar experts also think they can get the better of stealth
technology. They maintain that no plane can be completely
invisible, since radar always sees some thing, if only the
atmospheric turbulence created by the aircraft. But the radar
designers admit that the signals bouncing back from stealth
planes will be very weak and hard to distinguish from background
noise. The solution, they say, is to improve the computer
software used to process the signals. One advanced system,
developed by the French and known as "multistatic" radar, uses
several different receivers to collect weak signals. Such a
system may be able to spot stealth aircraft.

    In short, it is too soon to write radar's epitaph. Military
history teaches that every technological breakthrough provokes
a technical response. Observes Congressman Dave McCurdy, an
Oklahoma Democrat who sits on the House Armed Services
Committee: "There's a lot of room for radar to evolve,
particularly in software and signal processing. Military
technology is like a continuing chess game, with no final move."