Defenses Against Detection

Defenses Against Detection

A B-2's landing gear

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 like light 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 missions.
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, the laser 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.

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.
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, a control computer, an inertial guidance system, 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.
In the air, the JDAM's GPS receiver processes signals from GPS satellites to keep track of its own position, while the inertial guidance system tracks the bomb's change in position. The control computer 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.

A munitions specialist guides an erector to mount a rotary launcher, carrying nuclear bombs, into a B-2.

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 machine.

Computer Design

Northrop Grumman 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.