Stealth aircraft

From Wikipedia, the free encyclopedia

A stealth aircraft is an aircraft which has been designed to absorb and deflect radar (via stealth technology); these are not completely "invisible" to radar, they are simply harder to detect than conventional technology. In general the goal is to allow a stealth aircraft to execute its attack while still outside the ability of the opposing system's detection. Stealth aircraft were most notably used during the Gulf War (1991). Although stealth technology has since become less effective, the United States, Russia, China, India, and several other nations continue to develop stealth aircraft.

Contents 1 Benefits of stealth aircraft designs 2 Drawbacks of stealth aircraft designs 3 How stealth aircraft could potentially be detected 4 Use of stealth aircraft 5 List of stealth aircraft 5.1 Manned 5.2 Unmanned (full stealth) 5.3 Fictional

[edit] Benefits of stealth aircraft designs

• A smaller number of stealth aircraft may replace a large fleet of conventional attack jets with the same or increased combat efficiency, possibly resulting in longer term savings in the military budget.
• A stealth aircraft strike capability may deter potential opponents from taking action and keep them in constant fear of strikes, since they can never know if the attack planes are already underway. This may make them more willing to accept a diplomatic solution, although the moral reasoning behind this is disputed.
• Raids on important point targets, while maintaining a cover of plausible denial. Since no-one could detect the attackers or at least identify them, the stealth operator would simply refuse to comment and hope to avoid war.
• The production and fielding of a stealth combat aircraft design may force an opponent to pursue the same aim, possibly resulting in significant weakening of the economically inferior party. The 1980s American Strategic Defense Initiative ("Star Wars") program served a similar purpose against the USSR.
• Stationing stealth aircraft in a friendly country is a powerful diplomatic gesture. It emphasizes close relations between the allies and expresses high confidence in their governments and competence of security services, as stealth planes incorporate high technology and military secrets. The USA has stationed squadrons of F-117 Nighthawks in Britain.

[edit] Drawbacks of stealth aircraft designs

• Stealth aircraft are designed with a focus on minimal RCS (radar cross section) rather than aerodynamic perfection. Highly stealth aircraft (the F-117 and B-2) are aerodynamically unstable on all three axis and require constant flight corrections from the fly-by-wire system to stay airborne. Most modern non-stealth fighter aircraft (F-16, Su-27, Rafale) are unstable on one or two axis only. Stealth aircraft need to have highly redundant fly-by-wire systems for safety, which adds extra cost and weight to the design. In case of a strong electromagnetic pulse (e.g. atmospheric nuclear explosion), loss of flight control computers would affect stealth aircraft more seriously, possibly causing them to crash, but this is highly unlikely due to electronic hardening that is implemented by the United States Air Force.
• Stealth aircraft are seriously handicapped in combat once located by the enemy. Existing fully stealth designs (namely the F-117 and B-2) lack afterburners, whose hot exhaust would increase the RCS and infrared footprint of the plane. Stealth aircraft are thus unable to exceed the speed of sound and flee rapidly. This makes them vulnerable to fighter interceptors, which can reach Mach 2 or higher speeds using afterburners. The peculiar shape of stealth aircraft reduces their agility in a dogfight, thus they may be destroyed by autocannon fire from a traditional jetfighter, even if their low RCS and effective infrared shielding prevents a successful missile lock. Neither the F-117 nor the B-2 Spirit carry any anti-aircraft armament for self-defense.
• The high level of computerization and large amount of electronic equipment found inside stealth aircraft makes them vulnerable to passive detection. The Czech-developed, field-mobile Tamara system snoops on very weak electromagnetic "leaks" emanating even from the most shielded aircraft. Tamara detectors provide general range / distance information to active air defence radars, which would then lock onto targets using highly focused scanning.
• Stealth aircraft are high-maintenance equipment. The condition of the aircraft's skin determines stealth efficiency, either by diverting radar impulses due to specific geometry of the airframe and/or absorbing electromagnetic waves in a graphite-ferrite microspheres based surface paint layer. The cockpit windows are shielded with delicate gold and indium foil layers. If the plane's skin is punctured by a pebble thrown from the runway or heavy rain damages the paint layers, the RCS could be dramatically increased. Stealth planes are preferably operated from homeland bases, where air conditioned shelters provide optimal maintenance and storage conditions. Although airframe maintainability and availability progressed dramatically during the late 1990s, the cost of aircraft procurement, establishment of high- standard home base facilities, and the complex, long range sorties conducted from the homeland against overseas targets still places a serious economic burden on stealth aircraft operators.
• Stealth aircraft are still vulnerable to detection immediately before, during and after using their weaponry. Since stealth payload (reduced RCS bombs and cruise missiles) are not yet generally available, all armament must be carried internally to avoid increasing the radar cross section. As soon as the bomb bay doors are opened, the plane's RCS will be multiplied and even older generation radar systems will be able to locate them. Stealth aircraft pilots receive special training to minimize weapon dispatch intervals to 15-25 seconds. In case of 4th and 5th generation "reduced RCS" (semi-stealth) fighter-bomber designs, air-to-ground armament is mainly carried on external pylons, accepting the higher risk of detection. The internal weapon bays are reserved for various anti-aircraft missiles.
• Since fully stealth aircraft carry all armament internally, the available military payload is limited. The F-117 carried only two laser-guided bombs onboard, requiring highly reliable intelligence for a successful attack. Outside the scope of traditional war, it may be desirable to inject special forces troops on the ground, who would infiltrate the enemy territory and identify / illuminate the high-value point target for a successful laser-guided bomb raid by stealth aircraft.
• The B-2 Spirit carries a large bomb load, but it has relatively slow (transonic) speed, resulting in 18 to 24 hour long missions when it flies half-way around the globe to attack overseas targets. Therefore advance planning and receiving intelligence in a timely manner is of paramount importance for a successful sortie. In case mobile targets will be attacked, the Spirit will need to rely on satellite data or forward placed observers to guarantee a successful engagement. In July 1999 two days prior to the Royal International Air Tattoo at RAF Fairford UK, a single B2A Spirit penetrated UK airspace at 01.30 hours. Passing overhead reporting point Whisky Delta 2 at approx. 250 feet it was traveling at just above stalling speed and was completely silent. The anterior half of the aircraft structure was covered in a green-white condensation cloud.
• Stealth aircraft are an air traffic hazard unless flying in restricted training airspaces or fitted by externally mounted radar reflectors and light beacons to avoid collisions. Due to the great size of continental USA and general availability of sparsely populated areas this is not a significant training problem in practice.
• Stealth aircraft have a limited operational envelope. While the B-2 Spirit can put ordinance on any square foot of the planet within 12 hours it is operationally crippled by the following factors: Its exorbitant replacement cost exceeds the GDP of some countries, resulting in a challenging risk/benefit analysis when considering its deployment. It is still vulnerable to the mark 1 eyeball, making its deployment dependent on weather and time of day. Long range missions and the avoidance of radar facilities make its approach and departure vectors more predictable. While the aircraft may be stealthy, the ordinance delivered will more than adequately advertise its existence.

[edit] How stealth aircraft could potentially be detected

A number of methods to detect stealth aircraft at long range have been developed. Both Australia and Russia have announced that they have developed processing techniques that allow them to detect the turbulence of aircraft at reasonably long ranges (possibly negating the stealth technology).

Passive (multistatic) radar and bistatic radar systems are believed to detect stealth aircraft better than conventional monostatic radars, since stealth technology reflects energy away from the transmitter's line of sight, effectively increasing the radar cross section (RCS) in other directions, which the passive radars monitor. In addition, it has been suggested that use of low frequency broadcast TV and FM radio signals as the illuminating source produces a much higher RCS than high frequency monostatic radars as the long wavelengths cause whole structural portions of the targets to resonate. Target detection, even at very low signal-to-noise ratios is theoretically possible. Target tracking, in three-dimensional position and velocity should be more accurate with a multistatic system than with a monostatic system, using either triangulation or hyperbolic (or both) target location strategies. Wide usage of such broadcast signals (esp. in inhabited regions) means a continuous and reliable coverage and source of energy, that cannot easily be neutralized by an attacker. Researchers at the University of Illinois at Urbana-Champaign with support of DARPA, have shown that it is possible to build a synthetic aperture radar image of an aircraft target using passive multistatic radar, possibly detailed enough to enable Automatic Target Recognition (ATR).

Roke Manor Research in the United Kingdom announced an experimental system that uses the signals broadcast from cellular telephone towers to track aircraft, although it is not clear if this method is actually practical or offers any significant counter-stealth advantage. A general feature of these systems is that they use a large number of low-accuracy radar systems (or signal sources) combined with heavy computer processing to generate tracking information. For this reason they tend to be useful only in the early warning role, and have limited applicability to guidance radars for missile systems, and are rarely portable. The problem of successfully countering stealth aircraft on the battlefield remains essentially unsolved.

Stealth aircraft could also be passively detected from their electromagnetic emissions (terrain-following radar, radio communications, missile guidance communications etc.) if they broadcast such emissions. Stealth aircraft typically attempt to minimize these emissions (using low probability of intercept radars, satellite communications etc.).

To this date, the only systems that have been shown to successfully detect stealth aircraft are very old, and use long wave radar systems that have a low resolution. The shooting down of an F-117 over Yugoslavia in the 1999 Kosovo conflict Operation Allied Force, was attributed to the tracking of the vortices produced by the poor aerodynamic shape of stealth aircraft. It was also reported that the F-117 was downed due to the use of an "electro-optical" (TV) tracking system used in conjunction with the missile battery. The aircraft may be hard to detect using radar, but it is still visible to the naked eye.

An F-117 was also detected by a British ship during the first Gulf War, in this case because the wavelength of the radar was twice the length of the aircraft. This caused the entire aircraft to act as a dipole, leading to a very strong radar return.^{[citation needed]}

The Dutch company Thales Nederland, the former company Holland Signaal, developed a Stealth detection radar called SMART-L. So far the company has been unable to test it on a Stealth vehicle. The only chance was an airshow in Leeuwarden (the Netherlands) where an USAF B-2 would attend, but at the last moment the Boeing aircraft was withdrawn from the show. So, instead of testing the radar on a B-2, they used tennis balls instead. Four Dutch and three German frigates are equipped with this type of radar.

[edit] Use of stealth aircraft

To date, stealth aircraft have been used in several low- and moderate-intensity conflicts, including Operation Desert Storm, Operation Allied Force and the 2003 invasion of Iraq. In each case they were employed to strike high-value targets which were either out of range of conventional aircraft in the theater or which were too heavily defended for conventional aircraft to strike without a high risk of loss. In addition, because the stealth aircraft aren't going to be dodging surface-to-air missiles and anti-aircraft artillery over the target they can aim more carefully and thus are more likely to hit the target and not cause as much collateral damage. In many cases they were used to hit the high value targets early in the campaign (or even before it), before other aircraft had the opportunity to degrade the opposing air defense to the point where other aircraft had a good chance of reaching those critical targets.

Stealth aircraft in future low- and moderate-intensity conflicts are likely to have similar roles. However, given the increasing prevalence of excellent Russian-built surface-to-air missile systems on the open market (such as the SA-10, SA-12 and SA-20 (S-300P/V/PMU) and SA-15 (9K331/332)), stealth aircraft are likely to be very important in a high-intensity conflict in order to gain and maintain air supremacy, especially to the United States who is likely to face these types of systems. It is possible to cover one's airspace with so many air defences with such long range and capability that conventional aircraft would find it very difficult "clearing the way" for deeper strikes. For example, China license-builds all of the previously mentioned SAM systems in quantity and would be able to heavily defend important strategic and tactical targets in the event of some kind of conflict. Even if anti-radiation weapons are used in an attempt to destroy the SAM radars of such systems, or stand-off weapons are launched against them, these modern surface-to-air missile batteries are capable of shooting down weapons fired against them. The surprise of a stealth attack, and the ability to penetrate the air defences and survive, may become the only reasonable way of making a safe corridor through which conventional bombers and other aircraft can enter the enemy's airspace. Once stealth attacks from the smaller stealth force have neutralised the most serious of the SAM systems, the larger conventional or simply less-stealthy force should be able to suppress the remaining systems and gain air superiority.

[edit] List of stealth aircraft

[edit] Manned

Fully stealth designs:

• Have Blue - Lockheed (developed into F-117)
• Tacit Blue - Northrop (technology demonstrator reconnaissance plane)
• F-117 Nighthawk - Lockheed - fighter-bomber (in service)
• B-2 Spirit - Northrop-Grumman - strategic bomber (in service)
• A-12 Avenger II - McDonnell-Douglas / General Dynamics (cancelled)
• MBB Lampyridae - West German stealth fighter prototype (cancelled during wind tunnel tests in 1988)
• Bird of Prey - Boeing (technology demonstrator)

Reduced RCS designs:

• Horten Ho 229 - a German design of 1944, and perhaps the first basic stealth design
• Northrop YB-49 - like the Ho 229, this USAF bomber's stealthy characteristics were not the result of intentional design
• De Havilland Mosquito - British light bomber and ground attack plane of wooden construction, low RCS against early radars.
• Antonov An-2 - Wooden propellor and canvas wings give it a minimal radar signature.
• SR-71 Blackbird - Lockheed Advanced Development Projects High-speed reconnaissance aircraft. RCS equal to or better than the B-1B
• Eurofighter - EADS (in service)
• F-22 Raptor - Lockheed-Martin / Boeing (in service)
• YF-23 Black Widow II - Northrop / MDD (prototype built, lost competition to YF-22, almost full stealth, may resurrect as a fast bomber)
• F-35 Joint Strike Fighter - Lockheed-Martin (under development)
• Dassault Rafale - French air force and naval fighter bomber
• Medium Combat Aircraft - Hindustan Aeronautics Limited (under development) Indian Air Force stealthy 5th generation combat aircraft optimised for strike missions.
• MiG Project 1.44 "Flatpack" - Mikoyan-Gurevich (prototype), possibly full stealth with plasma shield
• J-10 - Chengdu Aircraft Industry Corporation (projected twin engine design for stealth missions)
• T-50 / PAK-FA - Sukhoi (under development, Russian-Indian counterpart of US F-22 Raptor, possibly plasma shielded)
• F-16 C/D and E/F - from Block 30 has got reduced RCS to about 1 m2
• F/A-18 C/D and E/F - both have reduced RCS, believed be to similar to F-16C's, but F/A-18 E/F is believed to have more advanced technology, but the aircraft is larger so the aircraft might (and might not) have the same RCS as F/A-18C/D
• MiG-29 SMT - has got similar to F-16C/D reduced RCS

[edit] Unmanned (full stealth)

• Boeing X-45 - Boeing - based on the manned Boeing Bird of Prey demonstrator (technology demonstrator)
• RQ-3 Dark Star - Lockheed / Skunk Works (cancelled)
• Dassault AVE-D Petit Duc - Dassault Aviation (tactical UAV)
• Dassault nEUROn - Dassault / Saab / EAB / Alenia / EADS CASA / RUAG / Thales (technology demonstrator)
• Future and current work into UAVs and UCAVs feature great focus into stealth technology.

[edit] Fictional

• Blackbird — X-Men
• General Galaxy YF-21 — Macross Plus
• F-19 Ghostrider — Testors
• F/A-37 Talon — Stealth
• Mikoyan MiG-31 — Firefox
• Mikoyan MiG-37 — Testors