Stealth

Stealth is the common name for not any specific system, but a collective term for a range of military low observability techniques. These techniques focus on reducing the signature of "stealthy" platforms — aircraft, missiles, ships, and ground vehicles — as detected, or not detected, by hostile sensors. While it is sometimes the case that a stealthy platform is not detected, that is not always achievable. Realistic goals, however, include making the platform hard to locate, and especially hard to "lock up" in the fire control systems of weapons that could be used against it.

For example, recent U.S. Navy ships, such as the Burke-class destroyers, have reduced observability compared to earlier classes. It is not seriously expected that an enemy would not know the ship was present, but its radar signature is sufficiently reduced to make it very hard for the final guidance radar of an anti-shipping missile to discriminate the ship from decoys and electronic self-protection signals intended to confuse the missile.

Radar signature reduction is the best-known aspect of low observability. By no means, however, is radar the only technology that the stealth technologies try to defeat. Low-observability aircraft also reduce their infrared signatures and reduce their measurement and signature intelligence#Acoustic MASINT#acoustic signatures if operating on or close to the ground. They prefer to operate in the darkest of night, and are painted black or a very dark gray even harder to see.

Indeed, while the first "stealthy" weapons system was the F-117 Nighthawk light bomber, this claim is met, with some amusement, by the submarine services of any advanced navy. The U.S. Navy submarine force calls itself the "silent service".

There is little question that submarines were the first low observability platforms. Early modern submarines, in the First World War, were primitive by today's standards — but they struck without warning, for the simple reason that humans do not see deep underwater. Understanding submarine quieting technologies is important to getting a full understanding of stealth.

Reducing radar signatures

Some might say that the "Black Jet", or F-117 Nighthawk stealth attack bomber, was an icon of the Gulf War, striking critical targets. Others might argue that an invisible icon is a contradiction in terms. Nevertheless, stealth aircraft with precision-guided munitions were the only manned aircraft that went "downtown" to Baghdad, and hit a high proportion of the key targets.

Somewhat ironically to the West, the fundamental principle of low radar observability came from an unclassified Soviet publication.

• Diffraction
• Radar absorption
• traveling waves; surface propagation and re-radiation
• multiple scattering and diffusion

Complements to reduced radar signatures

There is a perception that stealth aircraft such as the F-117 Nighthawk move in electronic and infrared silence, but, in complex strikes, that is not the case. If a stealthy aircraft is hard to find on radar when there are no other targets in the sky, imagine how much it is harder to find if there are radar jammers, blasting away at one's radar systems. The problem is rather like hearing the squeak of a timid mouse during a very noisy celebration.

Countermeasures to radar signature reduction

Radar signature reduction is, to a significant extent, dependent on the wavelength of the radar. The reflection and diffraction techniques are optimized first against the most likely weapons control frequencies, and second against the most likely search radar frequencies.