TIME: Almanac 1990/1990 Time Magazine Compact Almanac, The (1991)(Time).iso/time/110689/p83

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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."