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JIILY 1988
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JULY 1988
POPULAR SCIENCE
Popular
science
STEALTH!
Finally, it's official: The B2.
bomber exists. It will fly
this fall. Here's what
the Air Force revealed
and what it didn't
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Popular
science
What's News
Finally: Stealth!
So we're finally going to get a look at
a real stealth airplane. We're pleased
that it will look pretty much the way
we showed it on our September 1986
cover. We've dug up a good many new
details on the B-2, as you will find in
the piece starting on the next page.
Video ball and chain
In March POPULAR SCIENCE's cover
showed the Mitsubishi VisiTel-a new
low-cost videophone that transmits
pictures on ordinary phone lines. So I
was fascinated recently to spot the
same piece of equipment in a photo-
graph in The New York Times, espe-
cially because the accompanying piece
was about keeping jail crowding down
in Anne Arundel County, Md. It told
of a man who had been convicted of
drunk driving for a third time. He
was sentenced to two months of night-
time house arrest and was also told
not to drink. How do authorities make
sure he is at home-and sober? Twice
nightly, at random times, they call him
on the videophone. He answers with
his VisiTel. Not only can authorities
see that he's home, they can also watch
as he uses a hand-held breath ana-
lyzer, which displays blood-alcohol
levels in bright red numerals that can
be read over the VisiTel. So far seven
people under house arrest in the county
have been issued the units. For the
county it's cheaper than keeping some-
one in jail. And the customers are rea-
sonably happy. One unidentified user
complained that he was sometimes
awakened at night by the call from the
county. "I'm not happy about it," he
said, "but it sure beats going to jail.".
Pedal-powered plunge
The Da Vinci II finally got off the
ground-maybe. The pedal-powered
helicopter built by students at Califor-
nia Polytechnic State University [May]
quivered briefly as pilot Andres Eulate
pedaled furiously and may-just may
-have lost contact with Earth briefly.
Nobody is sure. Then bicycle racer Ted
Ito, fresh and burning to make history,
climbed into the pilot's seat. A few
minutes later the 140-foot rotor blade
lay on the floor, smashed beyond repair.
Scott Larwood, student director of
the project, says the problem was that
Ito weighs 15 pounds less than Eulate.'
That apparently changed the helicop-
ter's balance, so it pitched forward
when ground-crew members let go.
Now the team is evaluating whether
to rebuild the single wing or change
the design to a three-bladed rotor.
Energy roundup
. More news on the coal front: A
decade ago, a way of burning coal called
fluidized-bed combustion received con-
siderable attention, most recently in
this magazine in December 1981
["Multi-fuel Combustor"]. In such a
system coal and crushed limestone are
mixed, then fed to a furnace in which
they burn while suspended in a churn-
ing mass on a column of air. As the
coal burns, the limestone absorbs the
sulfur dioxide it produces, ending or
reducing the need for costly wet scrub-
bers. Now two major fluidized-bed
plants have come on line-a 110-mega-
watt plant at Colorado Ute Electric
Association's Nucla station and a
130-megawatt installation at Northern
State Power's Black Dog plant. The
technology could later be useful
in reducing acid rain and other air
pollution.
. The British have put another $15
million into a long-range project to
develop dry-hot-rock geothermal power.
Engineers are investigating a site in
Cornwall and hope to start building a
plant in 1991 when preliminary en-
gineering work has been completed.
They calculate that the site contains
enough heat to generate between 750
and 3,000 terawatt-hours of energy,
enough to supply power to southwest
England for the foreseeable future.
Better oil
The Society of Automotive Engineers
has recommended that car owners start
using a new type of engine oils, labeled
SG. The new oils have been compounded
to reduce engine wear. SG oils should
improve performance and durability
of car engines, the SAE says. They will
soon be available, and you can tell when
you're buying the new lubricant by
checking the doughnut-shaped symbol
on the can. What's different about SG
oils? Tom McDonnell, chairman of the
SAE fuels and lubricants division, says
SG oils have significantly more disper-
sants, detergents, oxidation inhibitors,
and anti-wear agents.
An Audi 12-banger?
BMW has one [Feb.]; Daimler-Benz is
developing one, as is Cadillac. Now
the (unofficial) word is that Audi will
have a 5.3-liter V12, or maybe a V10,
in a limited edition, four-wheel-drive,
active-suspension, high-priced super
coupe. Audi won't confirm the rumor.
Metric again?
The count is down. Now only Burma
and the United States still use English
measure. Even England has scrapped
this system. You may remember that
the Metric Conversion Act of 1975 set
up the goal of slow conversion in the
United States, and envisioned a slow
fading away of feet, pounds, and quarts.
What faded instead was the act.
Now the Defense Department is go-
ing to give metric another nudge. Any-
one bidding on a defense contract must
now use metric specifications. The
reason: simple economics, says the
Department. The move will end-
NATO's expensive dual inventory sys-
tem and make it easier for foreign
companies to get involved in joint
development programs. One Pentagon
official recalling the distinct lack of
enthusiasm with which the country-
received the general metrification
attempt in the mid-70s quipped, "We're
not trying to change the way people
live-just the way they fight."
Editor-in-Chief
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JULY 1988 | 45

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What the Air Force isn't saying-critical elements not shown
A CONTROL SURFACES
RADAR-ABSORBENT LINER
TURBINE COMPRESSOR
AIR INTAKE
SPOILERS
FLAPS
BOUNDARY-LAYER
GUTTER
S-DUCT
B ENGINE AIRFLOW
EXHAUST MIXER
-HEXAGONAL CELLS-
MAGNETIC AND
ENERGY DISSIPATING
COATING
RESISTIVE CARD
CONDUCTIVE INNER WING STRUCTURE . MULTI-LAYER ABSORBENT COVERING
INCOMING
SIGNAL
C RADAR ABSORPTION
RADAR-ABSORBENT MATERIAL
ROCKWELL INTERNATIONAL SCIENCE CENTER
ing edges of the wing (C) are constructed to minimize radar
reflection. First, they are covered with mi
multilayered mate" :;
rials that absorb radar signals. Second, the edges are con-
structed of a series of thumb size hexagonal honeycomb
tubes. Each hexagon is filled with radar-absorbing mate-"
rial, increasing in density from the outermost edge to the in-
nermost. An incoming radar signal first strikes and is partly
absorbed by the multilayered covering. The rest goes into
a hexagonal cell. As it penetrates, it continues to be pro-
gressively absorbed. The remaining signal that strikes the
angled surface at the rear is reflected in a zigzag pattern
even longer path. Such a technique might nearly eliminate
radar reflection from the wing edges. "It's a Roach Motel
for radar waves," said one observer. "They check in, but
they don't check out." Although it is not shown in the official
Air Force version, some experts think the wing-top pods:
will be faceted rather than smoothly contoured (D). When
a radar signal strikes a normal contoured surface of-the-
kind found on most aircraft, a glint is transmitted back in
almost any direction, making the target easy to see on radar.
A faceted surface, on the other hand, tends to reflect sig-
nals in directions slightly different from the direction from
which they came, so they do not return to the originating
radar. The surface, of course, would also be coated with
rection. One possible countermeasure that might be applied
against a stealth aircraft is bistatic radar, in which the trans-
The official painting of the B-2 released by the Air Force;
(above) shows a boomerang-shaped structure with a saw.
tooth trailing edge and three raised pods on the wing. Two. . back through the cell, continuing to be absorbed along this
are obviously for engines, the third is for crew and proba-
bly weapons. No control surfaces are shown. Experts guess
that in the absence of any vertical stabilizer, directional
control (A) might be achieved with elevons on the wingtips.
Spoilers raised on one wing and not the other might intro-
duce drag on one side, thus initiating a turn. Flaps might
· be mounted in the most forward parts of the serrated trail-
ing edge; because that would put them closest to the center '
of gravity, where they would have minimum effect on pitch.
Engine mounting is critical (B). Air probably flows through
the intakes on top of the wing through an S-duct to the
engines. Thus the engine compressor- a strong potential
source of radar echoes-is hidden from incoming radar sig.
nals. A yaned diffuser flattens the exhaust jet into a thin, > radar absorbent material to reduce reflections in any di-
wide plume, making it harder to spot by satellite-borne heat
sensors. A thin additional inlet called a boundary-layer gut-
ter can be seen below each main inlet. These probably serve : mitter is at one location and the receiver at another (E). The
two purposes. First, a layer of turbulent air near the top
surface of the wing can be bled off through this inlet,
smoothing the flow into the engine. Second, the additional
air is mixed with the jet exhaust, helping to cool It, further
R detection. The leading and trail-
signal transmitted by either ground or satellite transmitter
can ricochet off the target and be received by a separate
ground receiver. Another advantage of this arrangement:
The listening ground station is passive; because it is radar-si-
lent, its location cannot be determined by the attacking plane.
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48 | POPULAR SCIENCE
EXHAUST
DIFFUSER
ELEVONS

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frog the next generation of manned bombers directly into
the world of stealth. The Reagan administration later re-
instated a revised B-1 program, now the B-1B. The B-1B,
now going into operation, is scheduled to serve as a bridge
to the time when the B-2 will be brought into operation-
the 1990s.
Engineering secrets of the plane radar can't see
A daunting task-building an airliner-size flying struc-
ture that even super-sensitive.military radars can't find.
First job: reduce what engineers call the RCS- radar cross
section. The smaller the RCS, the smaller the echo re-
turned from a radar signal of a given signal strength.
A clue as to how this might be done appeared shortly
after World War II, when radar had changed the rules of
the military game. Engineers noticed that some planes
returned far larger radar images than others of essen-
tially the same size. "The problem is that an aircraft, or
parts of it, can act like an antenna, reradiating radar sig-
nals that strike it," said M. William Frasca, an expert in
radar-absorbent materials.
Some planes were better natural reradiators than oth-
ers. In particular, experts pointed to the Russian TU-95
Bear and the British Vulcan bomber. The TU-95, with
huge eight-bladed propellers, a tall vertical stabilizer, and
many sharp angles, returned a massive radar echo. The
Vulcan, by contrast, was a wedge-shape flying wing with
the engines buried inside and small vertical fins. At some
angles it virtually disappeared from radar, and at no angle
did it return an intense echo.
Over the years engineers have come up with an ever
clearer idea of why the Bear and Vulcan looked so differ-
ent to radar-and how they could design a stealth air-
craft to take advantage of these principles. For example,
the spinning compressor blades of a turbo jet inlet send
back radar echoes like a beacon. Sharp edges and abrupt
angles tend to act like antennas. So do tall vertical sta-
bilizers. "The more you make something into a smooth
blob, the better off you are from a radar point of view,"
says R. John Hansman, an aeronautical engineer from the
Massachusetts Institute of Technology.
But designers of all-out stealth aircraft are concerned
with more than just the shape. The materials used in the
structure are also selected to help with the job. Carbon ._
fiber materials; for example, are made by embedding thin
filaments of carbon in an epoxy resin. The resultant-ma-
terial is as strong as steel but does not reflect most radar
waves well. Its carbon-based molecules tend to absorb mi-
crowave energy, as food does in a microwave oven. One
plane built largely of carbon fiber was the Lear Fan
["Advanced-Design Lear Fan 2100," June '81] which had
to carry two radar transponders. That's because if a sin-
gle transponder failed, the plane was nearly invisible to
radar.
Some versions of such materials reportedly have been
composite developed for the Hound Dog missile and a black
fiber-reinforced graphite skin. Lockheed's stealth fighter
is reported to be made of Fibaloy, glass fibers embedded in
plastic, made by Dow Chemical.
considered for the B-2, including a carbon-and-fiberglass wanted radio waves. NEC had worked out a technique
Special coatings also help suppress radar reflections. The
«SR-71, for example, is said to be painted with a radar cial radars operate in the 10- to 30-gigahertz range.
ablative paint. This does not absorb radiation, but rather
conducts it over the surface of the structure, cooling off
hot spots that may develop at edges, corners, and other
such places. The substance used on the SR-71 is called
"iron-ball" paint, apparently because it contains micro-
scopic iron particles to increase conductivity.
ApprovedaFor Reteatsien'zogny ider Adolf Hitler's
Luftwaffe experimented (but not (248/08
The B-2 and B-1B might be used together in a scenario
such as this: The B-1B comes in at treetop level, becom-
Ing visible briefly as it rises above obstructions on its
approach to the target. During its approach, it releases
an intense barrage of radar jamming. With the ground
radar operators thus distracted, the B-2 sneaks in at high
altitude, a position from which it can detect mobile tar-
gets, move in close, and destroy targets without being
observed.
paints to make airplanes invisible to radar in World War
II. At the same time, German submarines had their
snorkles painted with a similar substance to keep British
radar from detecting them when they poked above the
surface.
Absorbent coverings first came to public notice in Janu-
ary 1982, when the U.S. Embassy in Tokyo called the TDK
company, a well-known manufacturer of electronic equip-
ment, with a strange request. The Embassy wanted to
buy one gallon of paint. So strange were the events sur-
rounding the request that it took until August for Japan's
Ministry of Trade and Industry to give an OK.
The paint,"it turned out, had been developed to stop'
leaks from microwave ovens. It contained ferrites iron-
containing compounds -and was apparently of interest to
U.S. researchers who were trying to design radar-absorptive
coatings for planes. Because Japan bans the export of
defense-related technology, and the ferrite paint was ap-
parently wanted for the stealth project, the Ministry took
the matter under advisement.
It turned out that another Japanese company-Nippon
Electric Co. (NEC) had also developed a similar paint that
had been used to coat towers and buildings in sensitive
locations to eliminate TV ghosts and scattering of un-
using two layers of the ferrite material separated by a
dielectric-an insulator. Such an electronic sandwich,
researchers found, could absorb much of the microwave
energy striking it over a frequency range of 3.5 to 20 giga-
hertz. And, most significantly, most military and commer-
That didn't mean the ferrite coating was right for stealth
aircraft, however. For one thing, it was too thick and heavy
to work properly on aircraft. So work continued.
About a year ago a researcher named Robert R. Birge
of Syracuse University in New York announced the dis
covery of a new class of radar-absorbing materials calle
retinyl Schiff base salts. The salts were black, resembl;
g&GA-RDP96.00789R0003008 16babyor 80 percent of
-

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in the official release.
D FACETS
RADAR ECHO
INCOMING SIGNAL
CONTOURED
SURFACE
FACETED
SURFACE
SATELLITE
TRANSMITTER
E BI-STATIC RADAR
.
GROUND
TRANSMITTER
PASSIVE
RECEIVER
picture was generally right, a defense-industry aircraft
designer told the paper that "Many times when we put
artist renderings together, we take a great deal of liberty
in disguising things we feel are important technologically.
And that's what they have done here." A Los Angeles air-
craft executive pointed out that important features such
as control surfaces had been left out, adding, "I wouldn't
bet my grandmother's diamond ring on the accuracy of
that picture."
But informed guesses as to the actual plane's details
can be made. Everyone agrees that the flying-wing shape
:. is right. That first became reliable news in 1985 when
Sen. Barry Goldwater, then chairman of the Senate
Armed Services Committee, who had seen a full-scale
mock-up of the plane, confirmed that it was a flying wing.
The picture shows that the wings are swept back about
30 degrees, which, as one expert points out, puts the
wingtips far enough behind the center of gravity so that
you could put effective control surfaces there-surfaces
that would operate with moment arms similar to those
you get by having a tail at the end of a boom. The pointy
nose suggests that there is no dish-shape radar antenna.
If the B-2 has a large radar antenna, it more likely is a
phased array radar in which the antenna is made up not
of a single dish, but numerous small elements that could
be distributed along the wing.
There is precedence as well. When the original B-1 was
modified to its present version-the B-1B-its dish-shape
antenna was replaced with a phased array, a modified ver-
sion of the APG-66 radar developed for the F-16 and used
in that fighter for terrain following and general naviga-
tion. A yet more advanced version probably appears in the
B-2.
The most surprising omission: The drawing shows no.
control surfaces at all. Some experts guess that there are
movable wing surfaces, probably placed as shown in the
drawings that accompany this article. Some also specu-
late that a technique called thrust vectoring-selectively
increasing and decreasing thrust to various engines --- could
help in steering the plane. Or it could use reaction control
-squirting jets of high-pressure air through nozzles to
change the plane's attitude-a technique used in space-
craft. It might even have wings with inner mechanisms
that could actually change shape, with trailing edges bend-
ing subtly up or down. This would avoid the radar reflec-
tions that can be generated by gaps formed by regular
hinged control surfaces.
One expert speculated that the strange sawtooth trail-
ing edge could accomplish two purposes. First, if flaps were
mounted in the notches, those flaps would be quite far
forward and near the plane's center of gravity. Thus they
would not greatly affect attitude or pitch. Second, straight
lines tend to reflect radar signals. By breaking the trail-
ing edge up into many lines-no two of them parallel
-radar reflections would be minimized. And finally, all
agree that the plane undoubtedly uses fly-by-wire tech-
niques. Like the famous wrong-way-wing X-29 [April '80]
the flying wing is a fundamentally unstable design. There-
fore a computer constantly monitors its actions, rapidly
and continuously applying small corrections to keep it
flying straight and level.
"I would bet a nice cold beer that it has four engines,"
said an engineer at a competing aircraft company. The
shape of the inlets supports this: The double-scoop design
indicates that two pairs of side-by-side engines lurk in-
side the wing.
The drawing is vague about size. Some experts say the
cockpit may be deliberately too large to disguise the true
size of the plane. Reasons Bill Sweetman: He has heard
that the plane has four GE F-101 turbofan engines-the
same power plants used on the B-1B bomber. Each gener-
ates 17,000 pounds of thrust, a total of 68,000 pounds.
Assuming a standard 0.25 to 0.28 thrust-to-weight ratio
for a large four-engine plane, the weight would fall into
the 240,000- to 275,000-pound category with a wingspan
of 130 to 140 feet. Others have predicted that it would be
bigger and heavier. Various reports have guessed that speed
would be about Mach 0.8-about the same as an airlin-
er's, and range without refueling some 5,000 miles.
An old idea
The concept of undetectable planes goes back to 1912,
when the U.S. Army built a heavily mufflered plane with
a carefully camouflaged paint job. The magazine Aerial
Age noted that the new development "opened up a won-
derful field in aviation, making it possible for a biplane
or monoplane to sail over cities unheralded and unseen,"
Stealth became compelling for military planners in 1973.
The Arab-Israeli war broke out, and 40 U.S .- built planes
were shot down by Soviet-built SA-6 radar-guided mis-
siles, despite advanced electronic-warfare equipment that
was supposed to protect them. Sweetman guesses that by
1975 the Air Force had asked Lockheed's famous "skunk
works" run by the legendary Kelly Johnson to produce a
stealth aircraft, and that several flying versions-including
the apparently now-operational, but not yet public, F-19-
have since been flown.
A short time later-probably in 1981-Northrop was
tapped to develop what was called the ATB-for advanced
technology bomber-which has since come to be called
the stealth bomber and lately the B-2. Almost immedi-
ately a battle broke out in Congress over whether the
country could afford to develop the ATB and also keep
developing the B-1-then already underway.
With budget pressures building, the Carter administra-
tion canceled the B-1 program, apparently hoping to leap-
Continued
JULY 1988 | 49
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52 | POPULAR SCIENCE
BIG RIG
DE
-HULL
Appro
Anchored 1,760 feet down on the bottom of the
Gulf of Mexico, this record-setting tension-leg plat-
form will tap oil from beneath the sea floor. Unlike
"conventional platforms that sit atop underwater
skyscrapers, this newest engineering marvel is
anchored by gigantic steel mooring lines.
By NAOMI J. FREUNDLICH
Illustrations by Linda Richards
F
rom a distance the new platform will look just like the
others in a growing city of huge underwater skyscrapers
that tap the oil-rich seabeds of the Gulf of Mexico. Clus-
tered on the continental shelf, these platforms tap reserves in
depths of water of around 1,000 feet. But next year, when tug-
kieboats haul Conoco Inc.'s platform into the Gulf, its destination
will explain its unusual design. The platform, with its four huge
hull columns churning the water, will move past the urban
sprawl to new frontiers: the Green Canyon Block 184 oil field,
about 170 miles southwest of New Orleans, where water depths
reach almost 2,100 feet. When the platform is installed in 1,760
feet, it will be the world's deepest-ever design.
This Gulf of Mexico pioneer is a radically new kind of oil-
production platform designed by Conoco to tap deeper reserves
economically. Connected to the seabed by 12 tubular steel moor-
ing lines, the platform's natural buoyancy creates an upward
force, keeping the legs under tension and allowing it to stay
in place in water up to 6,000 feet deep. The tension-leg plat-
form (TLP) is stable and cost effective: It requires far less steel
than fixed platforms; and with the help of agile remotely oper-
ated vehicles (ROVs), it's easy to maintain. But perhaps the
most important aspect of the tension-leg design is its portabil-
ity. Once a TLP's work is done in one oil field, it can be un-
For Release 2000/08/08 : CIA-RDP96-00789pb00isdaadatha and moved to another site. Achieving-
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Stealth! (Continued from page 51]
Such figures show why there has
been such a drive to produce stealth
airplanes for many years. Some, in
fact, hypothesize that more has been
spent on stealth than on the much
more highly publicized Strategic De-
fense Initiative, or "Star Wars," proj-
ect. But while a stealth bomber would
have many important advantages, it
would have to give up a lot of desir-
able features as well.
"The more stealthy you make an air-
craft, the less efficient will be its per-
formance," says Anibal Tinajero, a
defense analyst with the Congres-
sional Research Service. The experts
agree: Design a plane for maximum
stealth, and you give up performance,
range, and payload.
First, stealthy shapes have rela-
tively low inherent stability and con-
trollability. Remember Hansman's
remarks about the best stealth shape
being a blob? Unfortunately, blobs
don't have very efficient aerodynamic
shapes. For best directional control
and stability, for example, control sur-
faces are on the tail-well behind the
center of gravity. To gain stealth, the
B-2 gives up its tail entirely.
While the shape of the Lockheed
fighter has never been revealed, it is
generally agreed that several have
crashed during testing, the last of
which was on July 11, 1986, when mil-
itary authorities cordoned off vast
areas of the California mountains in
which a plane-never identified-had
gone down.
Other threats
Most speculation concerning the B-2
has involved hiding it from enemy
radar, because radar is clearly the
prime military sensor used today. Yet
the plane would be worthless if it
could be easily detected and tracked
by other methods. For example, sat-
ellites with infrared sensors have been
highly developed. They're used, among
other things, to track-test missile fir-
ings by both the United States and
the Soviet Union. If stealth put out a
hot exhaust trail, it might be tracked
by satellite infrared sensors. Three
techniques will probably be used by
stealth to mask IR. First, the exhaust
is apparently below the wing, hidden
from direct view by a satellite. Sec-
ond, it will probably use a broad
diffuser that will change the concen-
trated jet exhaust into a wide thin
wedge of gases. And third, a small
auxiliary inlet beneath the main
engine inlet-engineers call it the
boundary-layer gutter-may gather
air to mix with the exhaust, cooling
it and thus reducing the probability
of it being seen by an IR sensor.
Finally, the B-2 will be equipped
with the latest electronic countermea-
sures available. Because it will have
such a small RCS, it will be possible
to use forms of ECM spoofing not gen-
erally available. "Radar cross section
is only one aspect that's going to make
a super penetrator," said one officer
who would not speak for attribution.
"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."
Such a combination would be able
to confuse the enemy even if he picked
up a stealth echo. "With a very small
target, it's easy to spoof at a low
power," says Sweetman. "So you can
send back a doctored return. You
broadcast something that imitates the
return on the first pulse, but then you
gradually feed in an error that says
you're where you're not. The second
pulse is a little bit later than the real
pulse would be. The third is still a lit-
tle more separated, and so on. By this
time the radar's logic is locked onto
this wrong pulse train, and before you
know it, the enemy has got the wrong
range."
Although there is no evidence to re-
veal just where it may stand, there is
the possibility of an even more exotic
approach. It is a technique called ac-
94 | POPULAR SCIENCE
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