Stealth aircraft
Stealth aircraft are designed to avoid detection using a variety of technologies that reduce reflection/emission of
.While no aircraft is completely invisible to radar, stealth aircraft make it more difficult for conventional radar to detect or track the aircraft effectively, increasing the odds of an aircraft avoiding detection by enemy radar and/or avoiding being successfully targeted by
Full-size stealth combat aircraft demonstrators have been flown by the United States (in 1977), Russia (in 2000) and China (in 2011).[11] As of December 2020[update], the only combat-ready stealth aircraft in service are the Northrop Grumman B-2 Spirit (1997), the Lockheed Martin F-22 Raptor (2005), the Lockheed Martin F-35 Lightning II (2015),[12][13] the Chengdu J-20 (2017),[14] and the Sukhoi Su-57 (2020),[15] with a number of other countries developing their own designs. There are also various aircraft with reduced detectability, either unintentionally or as a secondary feature.
In the
Design principles
Besides all the usual demands of flight, the design of a stealth or low-observability aircraft aims to reduce radar and infrared (thermal) detection, including:
- Reduce thermal infra-red emission from the engine and its exhaust wake
- Reduce radar reflection back to a hostile receiver by shaping the airframe
- Reduce radar reflections from the airframe by the use of radar-absorbent materials (RAM) or radar-transparent materials such as plastics.
- Reduce radar detection from exposed internal surfaces such as the cockpit, weapons bay and engine intake ducting.
- Reduce infra-red and radar detection during adverse weather conditions[clarification needed]
Rotorcraft introduce a particular design challenge, due not only to their multiple wing surfaces and articulated joints, but also to the constantly-changing relationship of these to the main airframe surfaces. The Boeing–Sikorsky RAH-66 Comanche was one of the first attempts at a stealth helicopter.
Limitations
Instability of design
Early stealth aircraft were designed with a focus on minimal radar cross section (RCS) rather than aerodynamic performance. Highly stealthy aircraft like the F-117 Nighthawk are aerodynamically unstable in all three axes and require constant flight corrections from a fly-by-wire (FBW) flight system to maintain controlled flight.[16] As for the B-2 Spirit, which was based on the development of the flying wing aircraft[17] by Jack Northrop in 1940, this design allowed for a stable aircraft with sufficient yaw control, even without vertical surfaces such as rudders.
Aerodynamic limitations
Earlier stealth aircraft (such as the F-117 and B-2) lack
Electromagnetic emissions
The high level of computerization and large amount of electronic equipment found inside stealth aircraft are often claimed to make them vulnerable to passive detection. This is highly unlikely and certainly systems such as Tamara and Kolchuga, which are often described as counter-stealth radars, are not designed to detect stray electromagnetic fields of this type. Such systems are designed to detect intentional, higher power emissions such as radar and communication signals. Stealth aircraft are deliberately operated to avoid or reduce such emissions.[citation needed]
Current
Vulnerable modes of flight
Stealth aircraft are still vulnerable to detection while and immediately after using their weaponry. Since stealth payload (reduced RCS bombs and cruise missiles) is not yet generally available, and ordnance mount points create a significant radar return, stealth aircraft carry all armaments internally. As soon as weapons bay doors are opened, the plane's RCS will be multiplied and even older generation radar systems will be able to locate the stealth aircraft. While the aircraft will reacquire its stealth as soon as the bay doors are closed, a fast response defensive weapons system has a short opportunity to engage the aircraft.
This vulnerability is addressed by operating in a manner that reduces the risk and consequences of temporary acquisition. The B-2's operational altitude imposes a flight time for defensive weapons that makes it virtually impossible to engage the aircraft during its weapons deployment.[citation needed] New stealth aircraft designs such as the F-22 and F-35 can open their bays, release munitions and return to stealthy flight in less than a second.[citation needed]
Some weapons[specify] require that the weapon's guidance system acquire the target while the weapon is still attached to the aircraft. This forces relatively extended operations with the bay doors open.
Such aircraft as the F-22 Raptor and F-35 Lightning II Joint Strike Fighter can also carry additional weapons and fuel on hardpoints below their wings. When operating in this mode the planes will not be nearly as stealthy, as the hardpoints and the weapons mounted on those hardpoints will show up on radar systems. This option therefore represents a trade off between stealth or range and payload. External stores allow those aircraft to attack more targets further away, but will not allow for stealth during that mission as compared to a shorter range mission flying on just internal fuel and using only the more limited space of the internal weapon bays for armaments.
Reduced payload
Fully stealth aircraft carry all fuel and armament internally, which limits the payload. By way of comparison, the F-117 carries only two laser- or GPS-guided bombs, while a non-stealth attack aircraft can carry several times more. This requires the deployment of additional aircraft to engage targets that would normally require a single non-stealth attack aircraft. This apparent disadvantage however is offset by the reduction in fewer supporting aircraft that are required to provide air cover, air-defense suppression and electronic counter measures, making stealth aircraft "
Sensitive skin
Stealth aircraft often have skins made with
Cost of operations
Stealth aircraft are typically more expensive to develop and manufacture. An example is the B-2 Spirit that is many times more expensive to manufacture and support than conventional bomber aircraft. The B-2 program cost the U.S. Air Force almost $45 billion.[21]
Countermeasures
Reflected waves
Researchers at the
In December 2007, SAAB researchers revealed details for a system called Associative Aperture Synthesis Radar (AASR) that would employ a large array of inexpensive and redundant transmitters and receivers that could detect targets when they directly pass between the receivers/transmitters and create a shadow.[24] The system was originally designed to detect stealthy cruise missiles and should be just as effective against low-flying stealth aircraft. That the array could contain a large amount of inexpensive equipment could potentially offer some "protection" against attacks by expensive anti-radar (or anti-radiation) missiles.
Infrared (heat)
Some analysts claim
In air combat, the optronic suite allows:
- Detection of non-afterburning targets at 45 kilometres (28 mi) range and more;
- Identification of those targets at 8-to-10-kilometre (5.0 to 6.2 mi) range; and
- Estimates of aerial target range at up to 15 kilometres (9.3 mi).
For ground targets, the suite allows:
- A tank-effective detection range up to 15 kilometres (9.3 mi), and aircraft carrier detection at 60 to 80 kilometres (37 to 50 mi);
- Identification of the tank type on the 8-to-10-kilometre (5.0 to 6.2 mi) range, and of an aircraft carrier at 40 to 60 kilometres (25 to 37 mi); and
- Estimates of ground target range of up to 20 kilometres (12 mi).
Longer wavelength radar
VHF radar systems have wavelengths comparable to aircraft feature sizes and should exhibit scattering in the resonance region rather than the optical region, allowing most stealth aircraft to be detected. This has prompted Nizhny Novgorod Research Institute of Radio Engineering (NNIIRT) to develop VHF AESAs such as the NEBO SVU, which is capable of performing target acquisition for Surface-to-air missile batteries. Despite the advantages offered by VHF radar, their longer wavelengths result in poor resolution compared to comparably sized X band radar array. As a result, these systems must be very large before they can have the resolution for an engagement radar. An example of a ground-based VHF radar with counter-stealth capability is the P-18 radar.
The Dutch company
OTH radar (over-the-horizon radar)
Over-the-horizon radar is a concept increasing radar's effective range over conventional radar. The Australian JORN Jindalee Operational Radar Network can overcome certain stealth characteristics.[27] It is claimed that the HF frequency used and the method of bouncing radar from ionosphere overcomes the stealth characteristics of the F-117A. In other words, stealth aircraft are optimized for defeating much higher-frequency radar from front-on rather than low-frequency radars from above.
History
World War I and World War II
During World War I, the Germans experimented with the use of Cellon (Cellulose acetate), a transparent covering material, in an attempt to reduce the visibility of military aircraft. Single examples of the Fokker E.III Eindecker fighter monoplane, the Albatros C.I two-seat observation biplane, and the Linke-Hofmann R.I prototype heavy bomber were covered with Cellon. However, it proved ineffective, and even counterproductive, as sunlight glinting from the covering made the aircraft even more visible. The material was also found to be quickly degraded both by sunlight and in-flight temperature changes, so the attempt to make transparent aircraft was not proceeded with.[28]
In 1916, the British modified a small SS class airship for the purpose of night-time aerial reconnaissance over German lines on the Western Front. Fitted with a silenced engine and a black gas bag, the craft was both invisible and inaudible from the ground, but several night-time flights over German-held territory produced little useful intelligence, and the idea was dropped.[29]
Nearly three decades later, the
Modern origins
Modern stealth aircraft first became possible when Denys Overholser, a mathematician working for
Reduced radar cross section is only one of five factors the designers addressed to create a truly stealthy design such as the F-22. The F-22 has also been designed to disguise its infrared emissions to make it harder to detect by infrared homing ("heat seeking") surface-to-air or air-to-air missiles. Designers also addressed making the aircraft less visible to the naked eye, controlling radio transmissions, and noise abatement.[3]
Modern operations
The first combat use of purpose-designed stealth aircraft was in December 1989 during
The U.S, UK, and Israel are the only countries to have used stealth aircraft in combat.
In 1990 the F-117 Nighthawk was used in the First Gulf War, where F-117s flew 1,300 sorties and scored direct hits on 1,600 high-value targets in Iraq[39] while accumulating 6,905 flight hours.[40] Only 2.5% of the American aircraft in Iraq were F-117s, yet they struck 40% of the strategic targets, dropping 2,000 tons of precision-guided munitions and striking their targets with an 80% success rate.[40][41]
In the
In the 2003 invasion of Iraq, F-117 Nighthawks and B-2 Spirits were used, and this was the last time the F-117 would see combat. F-117s dropped satellite-guided strike munitions on selected targets, with high success. B-2 Spirits conducted 49 sorties in the invasion, releasing 1.5 million pounds of munitions.[42]
During the May 2011
Stealth aircraft were used in the 2011 military intervention in Libya, where B-2 Spirits dropped 40 bombs on a Libyan airfield with concentrated air defenses in support of the UN no-fly zone.[43]
Stealth aircraft will continue to play a valuable role in air combat with the United States using the F-22 Raptor, B-2 Spirit, and the F-35 Lightning II to perform a variety of operations. The F-22 made its combat debut over Syria in September 2014 as part of the US-led coalition to defeat ISIS.
From February 2018, Su-57s performed the first international flight as they were spotted landing at the Russian Khmeimim Air Base in Syria. These Su-57s were deployed along with four Sukhoi Su-35 fighters, four Sukhoi Su-25s, and one Beriev A-50 AEW&C aircraft.[44] It is believed that at least 4 Su-57 are deployed in Syria[45] and that they have likely been armed with cruise missiles in combat.[46]
In 2018, a report surfaced noting that Israeli F-35I stealth fighters conducted a number of missions in Syria and even infiltrated Iranian airspace without detection.[36] In May 2018, Major General Amikam Norkin of IAF reported that Israeli Air Force F-35I stealth fighters carried out the first-ever F-35 strike in combat over Syria.[37]
The
List of stealth aircraft
Type | Country | Class | Role | Date | Status | No. | Notes |
---|---|---|---|---|---|---|---|
Airbus Sagitta | Germany | UAV | Experimental | 2017 | Prototype | 1 | |
BAE Systems Corax | UK | UAV | Experimental | 2004 | Prototype | ||
BAE Systems Replica | UK | 1999 | Project | ||||
BAE Systems Taranis | UK | UAV | Attack | 2013 | Prototype | ||
BAE Systems Tempest | UK | Supersonic | Fighter | Project | UK contribution to the Global Combat Air Programme (qv). | ||
Baykar Bayraktar Kızılelma |
Turkey | UAV | 2022 | Prototype | 2 | [51] | |
Boeing Bird of Prey | US | Subsonic | Experimental | 1996 | Prototype | ||
Boeing Model 853-21 Quiet Bird | US | Subsonic | Reconnaissance | Project | Developed from Model 853. | ||
Boeing MQ-25 Stingray | US | UAV | Experimental | 2019 | Prototype | [52] | |
Boeing MQ-28 Ghost Bat | Australia | UAV | Loyal wingman | Prototype | [53] | ||
Boeing X-32 | US | Supersonic | Fighter | 2000 | Prototype | 2 | |
Boeing X-45 | US | UAV | Experimental | 2002 | Prototype | ||
Boeing–Sikorsky RAH-66 Comanche | US | Rotorcraft | Attack | 1996 | Prototype | 2 | |
Chengdu J-20 | China | Supersonic | Fighter | 2011 | Production | 210+ | |
Chengdu WZ-10 | China | UAV | 2014 | Production | |||
Dassault nEUROn | France | UAV | Attack | 2012 | Prototype | ||
DRDO Ghatak | India | UAV | Project | ||||
DRDO SWiFT | India | UAV | Experimental | 2022 | Prototype | ||
EADS Mako/HEAT | International | Supersonic | Attack | Project | |||
FCAS (New Generation Fighter) | International | Supersonic | Fighter | Project | France, Germany & Spain (within FCAS) | ||
Flygsystem 2020 | Sweden | Supersonic | Fighter | Project | |||
Global Combat Air Programme | International | Supersonic | Fighter | Project | Merger of UK (BAE Systems Tempest), Japan (Mitsubishi F-X) & Italy | ||
HAL AMCA | India | Supersonic | Fighter | Project | |||
Hongdu GJ-11 | China | UAV | |||||
KAI KF-21 Boramae | International | Supersonic | Fighter | 2022 | Prototype | South Korea and Indonesia | |
Kratos XQ-58 Valkyrie | US | UAV | Experimental | [54] | |||
Lockheed F-117 Nighthawk | US | Subsonic | Attack | 1981 | Production | 64 | |
Lockheed Have Blue | US | Subsonic | Experimental | Prototype | |||
Lockheed SR-71 |
US | Supersonic | Reconnaissance | 1964 | Production | 32 | |
Lockheed Martin F-22 Raptor | US | Supersonic | Fighter | 1996 | Production | 195 | |
Lockheed Martin F-35 Lightning II | US | Supersonic | Fighter | 2006 | Production | 1000+ | A-variant CTOL, B-variant V/STOL, C-variant CATOBAR |
Lockheed Martin RQ-170 Sentinel | US | UAV | Production | 20-30 | |||
Lockheed Martin X-35 | US | Supersonic | Fighter | 2000 | Prototype | 2 | |
Lockheed Martin X-44 MANTA | US | Jet | Fighter | 2000 | Project | ||
MBB Lampyridae MRMF | Germany | Jet | Fighter | 1987 | Project | [55] | |
McDonnell Douglas X-36 | US | Subsonic | Experimental | 1997 | Prototype | 1 | No vertical tail. |
McDonnell Douglas A-12 Avenger II | US | Subsonic | Bomber | Project | |||
Mikoyan Skat | Russia | UAV | Attack | Project | |||
Mikoyan Project 1.44 | Russia | Supersonic | Fighter | 2000 | Prototype | 1 | Initially developt for the MFI project. |
Mikoyan LMFS | Russia | Supersonic | Fighter | Cancelled | |||
Mikoyan PAK DP | Russia | Supersonic | Fighter | Project | |||
Mitsubishi X-2 Shinshin | Japan | Supersonic | Experimental | 2016 | Prototype | 1 | |
NGAD (F/A-XX) | US | Supersonic | Fighter | Project | Navy´s NGAD programme. To replace Navy´s F/A 18 Super Hornets. | ||
NGAD (Penetrating Counter-Air (PCA)) | US | Supersonic | Fighter | Project | To replace USAF´s F-22 Raptors. | ||
Northrop Tacit Blue | US | Subsonic | Experimental | 1982 | Prototype | 1 | |
Northrop YF-23 | US | Supersonic | Fighter | 1990 | Prototype | 2 | |
Northrop Grumman B-2 Spirit | US | Subsonic | Bomber | 1989 | Production | 21 | |
Northrop Grumman B-21 Raider | US | Subsonic | Bomber | 2023 | Prototype | 1 | |
Northrop Grumman RQ-180 | US | UAV | Production | ||||
Northrop Grumman X-47A Pegasus | US | UAV | Experimental | 2003 | Prototype | ||
Northrop Grumman X-47B | US | UAV | Experimental | 2003 | Prototype | 2 | |
Ryan AQM-91 Firefly | US | UAV | Experimental | ||||
Shenyang FC-31 | China | Supersonic | Fighter | 2012 | Prototype | ||
Sukhoi Okhotnik |
Russia | UAV | Prototype | [56] | |||
Sukhoi Su-57 | Russia | Supersonic | Fighter | 2010 | Production | 21+ | |
Sukhoi Su-75 Checkmate | Russia | Supersonic | Stealth Multirole Fighter | 2024 | Project | ||
TAI Anka-3 | Turkey | UAV | 2023 | Prototype | 1 | [57] | |
TAI Kaan |
Turkey | Supersonic | Fighter | 2024 | Prototype | 1 | |
Tupolev PAK DA | Russia | Subsonic | Bomber | Project | |||
Windecker YE-5 | US | Tractor | Experimental | 1973 | Prototype | 1 | Stealth research, not fully stealthy. |
Xian H-20 |
China | Subsonic | Bomber | Project | |||
Yakovlev Yak-201 | Russia | Supersonic | Fighter | Project | VTOL[58] |
See also
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