Stealth technology

From TheBestLinks.com

(Redirected from Stealth)

Stealth technology covers a range of techniques, used mostly on stealth aircraft and ships, in order to make them less visible (ideally invisible) to radar. This was most notably used during the Gulf War (1991) although it has since become less effective due to developments in the algorithms used to process the data received by radars, such as Bayesian particle filter methods. Nevertheless, both the United States and Russia continue to develop stealth vehicles.

Stealth itself is not new. Special operations infantry have always used stealth. Even aircraft have used stealth, through mission unpredictability, secrecy, manuever, terrain following, electronic countermeasures, fake sorties, and other trickery. But "stealth technology", above and beyond electronic countermeasures, redesigns the aircraft itself to dramatically reduce the observability of the aircraft itself.

A mission using stealth will obviously become common knowledge eventually, such as when the target is destroyed. But if the attacking force maximizes stealth and speed, it uses the element of surprise. Attacking with surprise gives the attacker more time before the defending force can begin concentrating force to counter the attack. Conversely, the defender cannot bring as much force to bear to counter the attack. With stealth technology, the defender might not be able to respond at all.

Table of contents

Stealth Principles

Stealth technology is not a single technology but a combination of technologies, specifically:

a) Aircraft shape It has been known since at least the 1960s that aircraft shape makes a huge difference to how well an aircraft appears on radar. The BAC Vulcan, a British nuclear bomber of the 1960s, had a remarkably small appearance on radar despite its large size, and occasionally disappeared entirely. We now know that it had a fortuitously stealthy shape apart from the vertical element of the tail. On the other hand, the Tupolev 95 Russian long range bomber (NATO Reporting Name 'Bear') appeared especially well on radar. We now know that propellers (and even jet turbine blades) give a bright radar image. The Bear had 4 pairs of large (2.4 metre) contra-rotating propellers.

The most efficient way to reflect radar waves back to the transmitting radar is with two metal plates at right angles to one another, perpendicular to the incident radar wave. This configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. A stealth aircraft must use a different arrangement. Often, a stealth design has the vertical element of the tail tipped at an angle, as in the F-117. The most radical approach is to eliminate the tail completely, as in the B-2 Spirit. As well as altering the tail, stealth design must bury the engines within the wing or fuselage so that the turbine blades are not visible. The shape of the aircraft must have no bumps or protuberances of any kind if it is to be stealthy. This means that all weapons, fuel tanks, and other stores may not be carried on underwing pylons but must be stored internally. Furthermore, a stealth aircraft becomes unstealthy when it extends its mid-air refuelling probe.

Stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. The YF-23 has such serrations on the exhaust ports.

b) Use of non-metallic materials called composites for the airframe. Composites are transparent to radar, whereas metals reflect it back to the transmitting radar if the metal happens to be perpendicular to the radar, or else the metal is involved in an unstealthy shape.

c) Radar absorbing paint, especially on the edges of metal surfaces.

d) Technologies to reduce other signatures such as infra-red, sound, etc. Stealth aircraft need to stay subsonic to avoid being tracked by sonic boom and they need to reduce their infra-red signature. This is generally done by having a non-circular tail pipe (a slit shape) and mixing ambient air with the exhaust. The stealth aircraft must not radiate any energy which can be detected by the enemy. The F-117 uses a passive infra-red system to navigate and the F-22 has an advanced Low Probability of Interception (LPI) radar which can illuminate enemy aircraft without triggering a radar warning receiver response.

The size of a plane's image on radar is measured by the Radar Cross Section or RCS. Imagine a metal plate of area A square metres held perpendicular to the beam of radar transmitter. It reflects most of the radar energy back to the source, and thus is easily detected. It is said to have an RCS of A square metres. Modern stealth aircraft are said to have an RCS comparable with small birds or large insects, though this varies widely depending on aircraft and radar parameters.

Stealth tactics

Stealthy strike aircraft such as the F-117 are usually used against heavily defended enemy sites such as Command and Control centres or surface-to-air (SAM) batteries. Enemy radars will cover the entire airspace around these sites, with overlapping coverage, making undetected entry by conventional aircraft impossible. Stealthy aircraft can also be detected, but only at very short ranges around the radars, so that for a stealthy aircraft there are substantial gaps in the radar coverage. Thus a stealthy aircraft flying an appropriate route can remain undetected and attack the radars. Once the enemy radars are destroyed conventional strike aircraft can be deployed against all targets.

The first true stealth fighter is the F-22, complemented by the F-35. Assuming it can carry the appropriate weaponry, there is nothing preventing a stealth fighter from carrying out strike attacks similarly to the F-117. However, a fighter role entails somewhat different tactics, though many are simply airborne analogs of those of strike aircraft. A stealth fighter could approach an aerial target much more closely before being detected, allowing it a better position from which to launch guided weapons. Such weapons are also more easily evaded by stealth aircraft. With a datalink capability (common in most stealth fighters), coupled with an LPI AESA radar a stealth fighter can act as a stealth AWACS for other nearby aircraft. Stealthy fighters would also be ideal for escorting stealth strike aircraft.

References

Sequential Monte Carlo Methods in Practice, by A Doucet, N de Freitas and N Gordon. Published by Springer.

de:Stealth ja:ステルス (軍事) nl:Stealth es:Tecnolog�as de invisibilidad

Discussion

Last posted 0 of 0 messages

[no messages posted yet]

>> post message >>

Watch

You can add this article to your own "watchlist" and receive e-mail notification about all changes in this page.

Retrieved from "http://www.thebestlinks.com/Stealth_technology.html"