INVISIBLE BOMBER - SECRETS OF THE PLANE THAT RADAR CAN'T SEE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP85T00153R000100030020-6
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 5
• Document Creation Date: December 20, 2016
• Document Release Date: January 14, 2008
• Sequence Number: 20
• Publication Date: February 1, 1983
• Content Type: OPEN SOURCE

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Invisible
bomber
-secrets of the plane
that radar cant see
Airmen call them "stealth"
planes. To enemy radar, they
can look like hummingbirds
By JIM SCHEFTER
ILLUSTRATION BY DEAN ELLIS
Shaped like a broad, flat wing with only a smoothly blend-
ed windscreen revealing its cockpit, the bomber skimmed
across barren polar terrain at nearly 600 mph. Barely 400
feet below, ice floes vibrated to the roar of its concealed jet
engines. The early-warning radar fence lay behind, its
operators unaware that the first line of defense had al-
ready been penetrated.
More radar waited ahead. Hugging the terrain to take
full advantage of hills and valleys, the flying wing crossed
Continued
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SR-71 Blackbird spy plane (left) is one of the earliest
designs with anti-radar stealth concepts. A blue-black
coating is thought to have radar-absorbing properties.
The engines blend smoothly with the wings, and
slanted tail fins minimize radar reflections. British Vul-
can bomber (above) also has stealth features: Engines
are concealed within its triangular wing, unlike engines
on B-52s, which capture and reflect radar signals.
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Lear Fan 2100 prototype, made largely with graphite composites, is a commercial aircraft design that's almost invisible to radar.
out of the tundra. Despite its size and speed, it created just
a flicker on glowing scopes. It was no more than a hum-
mingbird darting south.
But this bird, still a paper airplane that won't fly before
1987, will be no harmless little avian. The popular word
used to describe it masks the most secret U.S. technology
program in four decades:
Stealth.
This multi-billion-dollar development, already under
way in a classified and guarded Northrup Corp. facility
midway between two major Los Angeles freeways, is
aimed at producing a new bomber that is virtually unde-
tectable by radar. A secondary effort to produce a modified
B-1 bomber with a low radar profile is under way at a
Rockwell International plant in nearby Palmdale.
And a third project, by the Lockheed Corp., already has
produced at least three prototype stealth fighters. Flying
from a secret field near Groom Lake, Nev., and from Eiel-
son AFB, Alaska, since 1979, two of these triangular-
shape craft have crashed, but for reasons not connected to
their strange design. The third reportedly continues to fly
test missions in both extreme heat and cold.
Taken together, the Pentagon expects these futuristic
aircraft to alter the balance of military power into the next
century.
How will a bomber-size aircraft deceive radar that is
itself state of the art? What new technology is on the draw-
ing board to create a machine that will penetrate enemy
airspace with impunity?
Some answers are emerging from this highly classified
program. Others undoubtedly will remain among the na-
tion's most tightly kept secrets. Briefings on stealth tech-
nology, when authorized by the Air Force, are sketchy.
Even individuals allowed to talk insist that their names be
concealed.
Even so, it was possible to put together a filtered look at
how the best aeronautical engineers in the world are de-
signing stealth-type aircraft. Some of the picture, neces-
sarily, is informed speculation by experts. But much al-
ready is known.
Low-flying attack
The bomber, for instance, is being designed to fly inter-
continental distances at low altitudes at about Mach 0.85.
"High-altitude attack is not a wise idea because it gives
the enemy a longer time to look at you on the way in," one
observer said.
The Air Force itself discourages the word "stealth." It
prefers the term "low observable" and calls Northrup's
project the ATB, or advanced-technology bomber.
62 I POPULAR SCIENCE
"When you talk about stealth," a high-ranking Air
Force officer told me, "you're talking about the ability to
offset the enemy threat to your penetration."
To do that takes an aircraft with a unique shape, built
with materials and coatings that both absorb and deflect
radar signals. It takes innovative designs to conceal jet
engines within the aircraft body. And it takes a host of
new electronics gear aboard the craft to isolate and confuse
enemy radar.
But the first step is designing the aircraft itself. Air
Force and industry officials stress that reducing radar
cross section-the reflecting surface actually seen by ra-
dar-is the major factor in playing aerial hide-and-seek.
Cross section is measured in square meters, as seen head-
on by defense radars.
For instance, the ancient B-52 that remains our primary
intercontinental bomber has a massive radar cross section
of about 100 square meters. Its tall, vertical stabilizer and
heavy body make it an ideal radar target. Even worse, its
large wing-slung engine pods concentrate radar signals
and echo them back with brilliant clarity.
A shrinking target
Rockwell's original B-1, which Jimmy Carter refused to
build, produced a radar image of just 1.0 square meters.
And the B-1B, now being reworked in a stealth version
that will fly in 1985, echoes a cross section of just a single
square meter.
That's a flashing alarm compared with the stealthy
bomber on Northrup's drawing boards. It reportedly will
have a radar cross section of one-millionth of a square me-
ter. A hummingbird is bigger.
Designers will achieve this strikingly small radar cross
section with a number of design innovations. For example,
sharp edges and abrupt angles, often seen on aircraft
wings and control surfaces, produce strong radar echoes.
So there will be none on the new planes. Northrup's bomb-
er will be a low-profile flying wing. (Significantly, Nor-
thrup also built the original B-49 Flying Wing, which first
flew in 1947.) Tomorrow's stealth bomber will take the
concept even further, expanding on the so-called blended-
body concept provided by Rockwell's B-1 [PS, May '77]. Its
wing-body leading edge will be smoothly rounded, and its
delta shape will integrate fuselage, cockpit, and wing into
a single flowing wedge. Engines will be buried inside the
body, not hung out as tempting radar targets.
Northrup engineers also are wrestling with designs for
the vertical stabilizer. Their first choice is to eliminate it
completely. If computer analyses point up handling prob-
lems with that concept, Northrup may decide to use small
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twin stabilizers. They would be canted inward to deflect
radar rather than echo it.
No information is available about overall size of this fly-
ing wing. But it is certain to be low-slung and squat, al-
most like a Frisbee or boomerang in proportions. All that
will make radar sighting more difficult. Yet more is
needed.
One solution is to eliminate metal wherever possible.
Early versions of radar-absorbing materials, primarily
carbon-and-fiberglass composites, were developed by
Rockwell for the Hound Dog missile. That technology is
being adapted for the stealth bomber.
Recent advances by a number of laboratories, including
the Air Force Materials Laboratory at Wright Patterson
AFB, Ohio, have led to composite materials that are stron-
ger and lighter than steel or titanium yet do not reflect
radar waves. A black fiber-reinforced graphite skin is
reported to be the leading contender for Northrup's
bomber.
With current technology, materials that absorb some
electromagnetic radiation are bonded to stronger titani-
um. But Lockheed's super-secret stealth fighter is believed
to be made largely of Fibaloy, a composite developed by
Dow Chemical Co. Fibaloy includes glass fibers embedded
in plastic and is said to be strong enough without metal
backing to form both the fighter's skin and its main struc-
tural members.
The result is a 20,000-pound fighter not only stealthy,
but small and light enough to be carried inside a C-5A
transport.
And the Air Force is heavily committed to developing
even better carbon composites. That leaves the stealth-
With front-facing air intakes,
that metal echoes radar like a
beacon. But the new bomber will
have concealed intakes, mounted
flush beneath the flying wing 15
bomber designers to consider their jet engines, which can't
eliminate metal.
"Jet-engine intakes are high-visibility items for radar,"
one aeronautical expert told me. "To get enough air into an
engine, you need big compressor sections up front. They're
very balanced, built to close tolerances, and made of heavy
metal."
With front-facing air intakes, that metal echoes radar
like a beacon. But the new bomber will have concealed
intakes, mounted flush beneath the flying wing. It also
may employ a version of a new intake-tunnel configura-
tion being developed for Rockwell's B-1B.
Called the zigzag tunnel, this innovation eliminates the
straight-line air flow that also lets radar flash directly into
the engine compressor. The new tunnel has twin channels
with a series of carefully designed curves that minimizes
radar reflections.
The expandable throat needed to reduce incoming air
speed and prevent a compressor stall in a high-flying su-
personic aircraft is gone. The result is a radar fooler. Sig-
nals entering the zigzag tunnel reflect back and forth at
the curves, instead of echoing a bright reflection to a
radarscope.
"We can do it because the B-1B is now a subsonic, low-
altitude penetrator," an Air Force officer said. "There's no
problem with stalls."
The new flying wing will add another innovation. Its
jet-engine exhaust will be cooled and masked, exiting from
smoothly faired thrust vents at the trailing edge. That
won't affect radar but will help protect the stealth bomb-
er from heat-seeking missiles or detection by infrared
sensors.
Northrup's stealth aircraft also will benefit from radar-
absorbing coatings first developed for Lockheed's legend-
ary SR-71 Blackbird. That plane got its -name from the
inky-black coating that reduces its radar signature and
camouflages it against the dark sky.
Details on newer coatings are highly classified. But Nor-
thrup is said to be including that technology in its flying
wing.
B-1 B accessories
Avionics will make up the rest of the fighter's approach
to radar invisibility. While declining to discuss the elec-
tronics that will go into the flying wing, the Air Force pro-
vided some details on equipment for the low-observable
B-1B.
First, the dish-type radar antenna in the nose of the
craft is gone, replaced by a phased-array antenna that re-
sembles a flat, oval plate. "The dish became a radar target
itself in some instances," an Air Force official said.
The phased-array antenna never moves. It is angled
generally forward, but its radiation is aimed electronical-
ly, and it doesn't reflect enemy signals. The system was
adapted off the shelf from a radar employed in the F-16
fighter.
The Air Force and Rockwell also eliminated an antenna
that ran down the B-1's back like a visible spine. That
spine provided angles just made to echo radar. The anten-
na, part of a programmable defensive-avionics system,
will be built directly into the aircraft.
The system is computer controlled and on-board pro-
grammable to seek and identify enemy radar or missiles.
"These avionics are the current state of the art," the officer
said. "They've been tested against surrogate Soviet sys-
tems and will defeat anything currently in their radar-
antenna inventory and any upcoming threats," he confi-
dently asserted.
The system being developed for Northrup's stealth plane
is presumably even better.
"Radar cross section is only one aspect that's going to
make a super-penetrator," the officer said. "The other half
is the avionics. When you get the radar visibility down
very small, you can start manipulating the radar signals
so the enemy doesn't see you."
That means stealth-type aircraft will carry new elec-
tronic-countermeasure gear to identify a radar station,
then transmit just the right signal to erase even the hum-
mingbird speck from its scope. The kind of countermea-
sure equipment now in use must be powerful enough to
obliterate the large radar signatures current aircraft
produce. Still, radar operators frequently know something
is happening, though maybe not what, when their scopes
are jammed.
"If you can use just enough energy to foil each radar set,
they won't even know you're there," the officer ex-
plained.
If current funding levels continue, the B-1B will be op-
erational in 1986, with 100 of them flying by 1988. To pro-
tect against it, the Russians will have to spend five times
as much on defenses as the aircraft cost the U.S., according
to an Air Force source. And that's just the start. The Nor-
thrup stealth plane now is scheduled to be in the military
inventory by 1992. "That will take another five-fold ex-
penditure if they want to even think about stopping it,"
the officer said. CID
FEBRUARY 1983 163
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