B-2 bomber, commonly known as the stealth bomber, was an
ambitious project, to say the least. In the 1970s, the U.S.
military wanted a replacement for the aging B-52
bomber. They needed a plane that could carry nuclear
bombs across the globe, to the Soviet Union, in only a few
hours. And they wanted it to be nearly invisible to enemy
As you might expect, hiding a giant plane is no easy task.
Grumman, the defense firm that won the bomber contract,
spent billions of dollars and nearly 10 years developing the
top secret project. The finished product is a revolutionary
machine -- a 172-foot wide flying wing that looks like
an insect to radar scanners! The craft is also revolutionary
from an aeronautics perspective: It doesn't have any of the
standard stabilizing systems you find on a conventional airplane,
but pilots say it flies as smoothly as a fighter jet.
In this edition of HowStuffWorks,
we'll find out how the B-2 flies and how it "vanishes." We'll
also look at the plane's major weapons systems and learn a
little about its history.
A Flying Wing An ordinary airplane consists
of a fuselage (the main body), two wings and
three rear stabilizers attached to the tail. The wings
generate lift, hoisting the fuselage into the air. The pilot
steers the plane by adjusting flaps on the wings and the
stabilizers. Moving the flaps changes how the air flows around
the plane, causing the plane to ascend, descend and turn. The
stabilizers also keep the plane level. (See How Airplanes
Work to find out how these components work together.)
The B-2 bomber has a completely different design: It's one
big wing, like a boomerang.
This flying wing design is much more efficient than
a conventional plane. Instead of separate wings supporting all
the weight of the fuselage, the entire craft works to generate
lift. Eliminating the tail and fuselage also reduces drag --
the total force of air resistance acting on the plane.
Greater efficiency helps the B-2 travel long distances in a
short period of time. It's not the fastest craft around -- the
military says it's high subsonic, meaning its top speed
is just under the speed of sound (around 1,000 ft/sec or 305
m/s) -- but it can go 6,900 miles (11,000 km) without
refueling and 11,500 miles (18,500 km) with one in-flight
refueling. It can get anywhere on Earth on short notice.
The B-2 has four General Electric F-118-GE-100 jet
engines, each of which generates 17,300 pounds of thrust.
Just as in an ordinary plane, the pilot steers the B-2 by
moving various flaps on the wings. As you can see in the
diagram below, the B-2 has elevons and rudders
along the trailing edge of the plane. Just like the elevator
and aileron flaps on a conventional plane, the elevons change
the plane's pitch (up and down movement) and
roll (rotation along the horizontal axis). The elevons
and rudders also control the plane's yaw (rotation
along the vertical axis).
Flying wings have been around for a long time, but in the
past, they suffered from major stability problems. Without the
rear stabilizers, the plane tends to rotate around its yaw
axis unexpectedly. The U.S. military didn't go for Northrop
Grumman's earlier flying wing designs from the 1940s mainly
because of these concerns.
By the 1980s, advancements in computer technology made the
flying wing a more viable option. Northrup Grumman built the
B-2 with a sophisticated fly-by-wire system. Instead of
adjusting the flaps through mechanical means, the pilot passes
commands on to a computer, which adjusts the flaps. In other
words, the pilot controls the computer and the computer
controls the steering system.
The computer also does a lot of work independent of the
pilot's input. It constantly monitors gyroscopic
sensors to keep track of the plane's attitude -- its
position relative to the airflow. If the plane starts to turn
unexpectedly, the computer automatically moves the rudders to
counteract the turning force. The corrections are so precise
that the pilot usually won't feel any shift at all. The B-2
also has a small wedge-shaped flap in the middle of the
trailing edge. The computer adjusts this flap, called the
gust load alleviation system (GLAS), to counteract air
The B-2 bomber needs only a two-person
crew -- a pilot and a mission commander who sit in a
cockpit at the front of the plane. By comparison, the
B-52 bomber has a five-person crew, and the B-1B has a
The original idea of the B-2 was that it wouldn't
need any support aircraft. Because of its stealth
capabilities, it should be able to penetrate enemy
airspace without fire support, doing the work of dozens
of planes. In practice, the B-2 usually flies with some
fighter jet protection. The risk of losing such an
expensive aircraft is too great to send it into battle
Out of Sight Northrop Grumman's primary goal
for the B-2 was stealth, or low observability.
Simply put, stealth is the ability to fly undetected through
enemy airspace. Ideally, a stealth aircraft will be able to
reach and destroy desired targets without ever engaging the
enemy in combat.
Photo courtesy U.S. Department of
Defense The B-2 is a huge
plane, but its advanced stealth capabilities make it
seem smaller than a sparrow on
To do this, the aircraft needs to be nearly invisible in a
number of different ways. Obviously, it needs to blend in with
the background visually, and it needs to be very quiet. More
importantly, it needs to hide from enemy radar as
well as infrared sensors. It also needs to conceal its
own electromagnetic energy.
The B-2's flat, narrow shape and black coloration help it
fade into the night. Even in the daytime, when the B-2 stands
out against blue sky, it can be hard to figure out which way
the plane is going. The B-2 emits minimal exhaust, so it
doesn't leave a visible trail behind it.
As with most planes, the B-2's noisiest component is its
engine system. But unlike a passenger jet or B-52, the B-2's
engines are buried inside the plane. This helps muffle the
noise. The efficient aerodynamic design helps keep the B-2
quiet as well, because the engines can operate at lower power
The engine system also works to minimize the plane's
infrared (heat) signature. Infrared sensors, including those
missiles, typically pick up on hot engine exhaust. In the
B-2, all of the exhaust passes through cooling vents before
flowing out of the rear ports. Putting the exhaust ports on
the top of the plane further reduces the infrared signature,
since enemy sensors would most likely scan below the plane.
The B-2 has two major defenses against radar detection. The
first element is the plane's radar-absorbent surface.
The radio waves used in radar are electromagnetic energy, just
waves. In the same way that certain materials absorb light
very well (black paint, for example), some materials are
particularly good at absorbing radio waves.
The B-2's body is mainly composed of composite
material -- combinations of various lightweight
substances. The composite material used in the B-2 bomber is
specifically designed to absorb radio energy with optimum
efficiency. Parts of the B-2, such as the leading edge, are
also covered in advanced radio-absorbent paint and tape. These
materials are very expensive, and the Air Force has to reapply
them regularly. After every flight, repair crews have to spend
many hours examining the B-2 to make sure it's fit for stealth
Highly reflective metal components, such as the plane's
engines, are all housed inside the composite body. Air flows
into the intake ports, though an S-shaped duct and down to the
engines. The bombs are also mounted inside the plane, and the
landing gear fully retracts after take-off.
The second element in radar invisibility is the plane's
shape. Radio waves bounce off planes in the same way light
bounces off a mirror. A flat, vertical mirror will bounce your
image straight back to you -- you'll see yourself. But if you
tilt the mirror 45 degrees, it will reflect your image
straight upward. You won't see yourself; you'll see an image
of the ceiling. A curved mirror also deflects light at an
angle. If you were to aim a laser pointer at a curved mirror,
beam would never bounce straight back to the pointer, no
matter how you positioned it.
The stealth bomber's peculiar shape deflects radio beams in
both ways. The large flat areas on the top and bottom of the
plane are just like tilted mirrors. These flat areas will
deflect most radio beams away from the station, presuming the
station isn't directly beneath the plane.
The plane itself also works like a curved mirror,
particularly in the front section. The entire plane has no
sharp, angled edges -- every surface is curved in order
to deflect radio waves. The curves are designed to bounce
almost all radio waves away at an angle.
The B-2 is designed to contain its own radio signals, the
electromagnetic energy generated by onboard electronics. The
plane does emit radio energy when using its radar scanner or
communicating with ground forces and other aircraft, but the
radar signal is small and highly focused, making it less
susceptible to detection.
When the B-2 project
began, the U.S. Air Force planned to buy 132 planes at a
total cost of $22 billion. By the time the aircraft was
unveiled in 1988, the price tag had jumped to more than
$70 billion. Many members of congress weren't pleased
with the expenditure, or with the more than $20 billion
the Pentagon had already spent developing the plane.
By the time the Soviet Union collapsed in 1991, the
price had jumped even higher and the need for a huge
fleet of B-2s had decreased. In 1993, Congress
authorized the Pentagon to buy 20 B-2s at around $2
billion a piece. A few years later, President Clinton
authorized the military to upgrade the original
prototype B-2 to a working weapon, bringing the total to
21. Many feel the plane isn't worth the high price tag
and maintenance costs, especially since the older,
cheaper B-52 and B-1 bombers can carry more bombs at
faster speeds. There are no plans to add more B-2s to
the fleet at this
Weapons Originally, the B-2's primary
purpose was to carry nuclear
bombs into the Soviet Union in the event of war. With the
collapse of the Soviet Union in 1991, the military redefined
the B-2's role somewhat. It is now classified as a
multi-role bomber -- it is designed to carry
conventional bombs in addition to nuclear munitions.
The B-2 packs two rotary launchers, housed in the
center of the craft. When the mission commander is ready to
fire, he or she sends a signal to the onboard computer. The
computer opens the bomb bay doors, rotates the launcher to
position the correct bomb and then releases that bomb.
The launchers carry conventional gravity bombs -- "dumb"
bombs that simply fall on their target -- as well as
precision guided bombs that seek out their target. The
plane can carry about 40,000 pounds of munitions.
Photo courtesy U.S. Department of
Defense A munitions
specialist guides an erector to mount a rotary launcher,
carrying nuclear bombs, into a
The B-2's precision guided bombs are actually "dumb"
munitions with a separate guidance system attached. This
guidance kit, known as Joint
Direct Attack Munition (JDAM), includes adjustable tail
fins, an inertial guidance system (a collection of
sensors and a microcontroller)
and a GPS
receiver. The B-2 uses its own GPS receiver to pinpoint
targets. Once the crew has located its target, they feed the
target's GPS coordinates to the JDAM and release the bomb.
designed the B-2 bomber almost entirely on computers --
a radical departure from the traditional drafting
methods. In the 1980s, this was a huge leap in
technology. Engineers could build precise models of the
aircraft, down to the smallest screw, and test out their
stealth and efficiency in a virtual simulator.
The manufacturing process was also computerized. The
computer guided extremely precise assembly robots
to make sure every piece was in exactly the right
position. It was crucial to prevent any errors because
they could compromise the plane's stealth shape.
In the air, the
JDAM's GPS receiver processes signals from GPS satellites to
keep track of its own position. The inertial guidance system
adjusts the JDAM's flight fins to guide the bomb to the
intended target. This precise targeting system allows the B-2
to drop its bombs and make a quick escape. The bomb works fine
even in bad weather, because the JDAM only needs to receive satellite
signals to find its target. It doesn't have to see anything on
the ground at all.
Because of its high cost and relative inexperience in the
field, the B-2 is a fairly controversial weapon. While some
analysts hold it up as the pinnacle of military aircraft,
others say the plane has severe limitations, such as its
stealth capabilities' high sensitivity to bad weather. But
just about everybody agrees it is a pivotal development in the
evolution of aeronautic technology. It is certainly an amazing
For much more information about the B-2, including the
fascinating story of its invention, check out the links on the