Stealth Or Low Observability Technology

Stealth Or Low Observability Technology
Stealth or low observability (as it is scientifically known) is one of the most misunderstood and misinterpreted concepts in military aviation by the common man. Stealth aircraft are considered as invisible aircraft, which dominate the skies. With an additional boost from Hollywood action movies, stealth is today termed as the concept invincibility rather than invisibility. Though, the debate still continues on whether stealth technology can make an aircraft invincible it was found that stealth aircraft are detectable by radar. 
The motive behind incorporating stealth technology in an aircraft is not just to avoid missiles being fired at is but also to give total deniability to covert operations. This is very much useful to strike targets where it is impossible to reach. Thus we can clearly say that the job of a stealth aircraft pilot is not to let others know that he was ever there.
In simple terms, stealth technology allows an aircraft to be partially invisible to Radar or any other means of detection. This doesn't allow the aircraft to be fully invisible on radar. Stealth technology cannot make the aircraft invisible to enemy or friendly radar. All it can do is to reduce the detection range or an aircraft. This is similar to the camouflage tactics used by soldiers in jungle warfare. Unless the soldier comes near you, you can't see him. Though this gives a clear and safe striking distance for the aircraft, there is still a threat from radar systems, which can detect stealth aircraft.

     The concept behind the stealth technology is very simple. As a matter of fact it is totally the principle of reflection and absorption that makes aircraft "stealthy". Deflecting the incoming radar waves into another direction and thus reducing the number of waves does this, which returns to the radar. The Aircraft with this technology is shown in Fig.1.1. Another concept that is followed is to absorb the incoming radar waves totally and to redirect the absorbed electromagnetic energy in another direction. Whatever may be the method used, the level of stealth an aircraft can achieve depends totally on the design and the substance with which it is made of.

Radar Absorbent Surfaces
  RAS or Radar absorbent surfaces are the surfaces on the aircraft, which can deflect the incoming radar waves and reduce the detection range. RAS (Radar absorbent surfaces) works due to the angles at which the structures on the aircraft's fuselage or the fuselage itself are placed. These structures can be anything from wings to a refuelling boom on the aircraft. The extensive use of RAS (Radar absorbent surfaces) is clearly visible in the "Night Hawk". Due to the facets (as they are called) on the fuselage, most of the incoming radar waves are reflected to another direction. Due to these facets on the fuselage, the Night Hawk is a very unstable aircraft. Stealth bomber with the Radar Absorbent Material on its surface is shown in the Fig.1.2.

The concept behind the RAS (Radar absorbent surfaces) is that of reflecting a light beam from a torch with a mirror. The angle at which the reflection takes place is also more important. When we consider a mirror being rotated from 0o to 90o, the amount of light that is reflected in the direction of the light beam is more. At 90o, maximum amount of light that is reflected back to same direction as the light beam's source. On the other hand when the mirror is tilted above 90o and as it proceeds to 180o, the amount of light reflected in the same direction decreases drastically. This makes the aircraft like Night Hawk stealthy.

Radar Absorbent Material  
  Radar absorbent surfaces absorb the incoming radar waves rather than deflecting it in another direction. Radar absorbent surfaces totally depend on the material with which the surface of the aircraft is made. Though the composition of this material is a top secret. The Night Hawk extensively uses RAM (Radar Absorbent Material) to reduce its radar signature or its radar cross section. The Radar absorbent surface is believed to be silicon based inorganic compound. This is assumed by the information that the RAM coating on the Stealth bomber is not water. This is just a supposition and may not be true. What we know is that the RAM (Radar Absorbent Material) coating over the Stealth bomber is placed like wrapping a cloth over the plane. When radar sends a beam in the direction of the Stealth bomber, the radar waves are absorbed by the plane’s surface and are redirected to another direction after it is absorbed. This reduces the radar signature of the aircraft.

Another important factor that influences the stealth capability of an aircraft is the IR (Infrared) signature given out by the plane. Usually planes are visible in thermal imaging systems because of the high temperature exhaust they give out. This is a great disadvantage to stealth aircraft as missiles also have IR(Infrared)  guidance system. The IR(Infrared)  signatures of stealth aircraft are minute when compared to the signature of a conventional fighter or any other military aircraft. If reducing the radar signature of an aircraft is tough, then reducing the IR(Infrared)  signature of the aircraft is tougher. It will be like flying a plane with no engines. The reduced IR(Infrared)  signature totally depends on the engine and where the engine is placed in an aircraft. Engines for stealth aircraft are specifically built to have a very low IR(Infrared)  signature. The technology behind this is top secret like others in stealth aircraft.     

Another main aspect that reduces the IR (Infrared) signature of a stealth aircraft is to place the engines deep into the fuselage. This is done in stealth aircraft like the Stealth bomber, Stealth fighter and the JSF (Joint Strike Fighter). The IR (Infrared)   reduction scheme used in Night Hawk is very much different from the others. The engines are placed deep within the aircraft like any stealth aircraft and at the outlet; a section of the fuselage deflects the exhaust to another direction. This is useful for deflecting the hot exhaust gases in another direction.

There are some more methods by which planes can avoid detection. These methods do not need any hi-tech equipment to avoid detection. Some of them have been used for years together by pilots to avoid detection. One of the main efforts taken by designers of the stealth aircraft of today is to carry the weapons payload of the aircraft internally. This has shown that carrying weapons internally can considerably decrease the radar cross-section of the aircraft. Bombs and Missiles have a tendency to reflect the incoming radar waves to a higher extent. Providing missiles with RAM(Radar Absorbent Material)  and RAS(Radar absorbent surfaces)  is an impossible by the cost of these things. Thus the missiles are carried in internal Bombay’s which are opened only when the weapons are released. Aircraft has used another method of avoiding detection for a very long time. Radars can use the radar waves or electro-magnetic energy of planes radar and locate it. An aircraft can remain undetected just by turning the radar off.  
In case of some of the modern stealth aircraft, it uses its wingman in tandem to track its target and destroy it. It is done in the following way. The fighter, which is going to attack moves forward, the wingman (the second aircraft) on the other hand remains at a safe distance from the target which the other fighter is approaching. The wingman provides the other fighter with the radar location of the enemy aircraft by a secured IFDL (In Flight Data Link). Thus the enemy radar is only able to detect the wingman while the attacking fighter approaches the enemy without making any sharp turns. This is done not to make any sudden variations in a stealth aircraft's radar signature. Thus the fighter, who moves forward, is able to attack the enemy without being detected.

Plasma Stealth
Plasma stealth technology is what can be called as "Active stealth technology" in scientific terms. This technology was first developed by the Russians. It is a milestone in the field of stealth technology. Aircraft with this technology.The technology behind this not at all new.
The plasma thrust technology was used in the Soviet / Russian space program. Later the same engine was used to power the American Deep Space 1 probe. 
In plasma stealth, the aircraft injects a stream of plasma in front of the aircraft. The plasma will cover the entire body of the fighter and will absorb most of the electromagnetic energy of the radar waves, thus making the aircraft difficult to detect. Graph between detection range & radar cross section is shown in the Fig.2.2. The same method is used in Magneto Hydro Dynamics. Using Magneto Hydro Dynamics, an aircraft can propel itself to great speeds. Plasma stealth will be incorporated in the "Super Fulcrum / Raptor Killer". This is a fight. Initial trials have been conducted on this technology, but most of the results have proved to be fruitful.  

Detection methods for stealth aircraft
Whenever a technology is developed for military purposes, another technology is also developed to counter that technology. There are strong efforts to develop a system that can counter the low obervability of the fifth generation stealth aircraft. There are ways of detection and elimination of a low observable aircraft but this doesn't give a 100% success rage at present. On a radar screen, aircraft will have their radar cross sections with respect to their size. This helps the radar to identify that the radar contact it has made is an aircraft. Conventional aircraft are visible on the radar screen because of its relative size. On the other hand, the relative size of a stealth aircraft on the radar screen will be that of a large bird. This is how stealth aircraft are ignored by radar and thus detection is avoided. A proven method to detect and destroy stealth aircraft is to triangulate its location with a network of radar systems. This was done while the Night Hawk was shot down during the NATO(North Atlantic Treaty Organisation)  offensive over Yugoslavia. A new method of detecting low observable aircraft is just over the horizon. Scientists have found a method to detect stealth aircraft with the help of microwaves similar to the ones emitted by the cell phone towers. Nothing much is known about this technology, but the US (United States) military seems to be very keen about doing more research on this.
Advantages of Stealth Technology
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 that were either out of range of conventional aircraft in the theater or were too heavily defended for conventional aircraft to strike without a high risk of loss. In addition, because the stealth aircraft do not have to evade 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 cause less collateral damage. In many cases they were used to hit the high value targets early in the campaign, before other aircraft had the opportunity to degrade the opposing air defence to the point where other aircraft had a good chance of reaching those critical targets. 

Disadvantage of Stealth Technology
Stealth technology has its own disadvantages like other technologies. Stealth aircraft cannot fly as fast or is not manoeuvrable like conventional aircraft. The Stealth fighter and the aircraft of its category proved this wrong up to an extent. Though the Stealth fighter may be fast or manoeuvrable or fast, it can't go beyond Mach 2 and cannot make turns. Another serious disadvantage with the stealth aircraft is the reduced amount of payload it can carry. As most of the payload is carried internally in a stealth aircraft to reduce the radar signature, weapons can only occupy a less amount of space internally. On the other hand a conventional aircraft can carry much more payload than any stealth aircraft of its class. 

Whatever may be the disadvantage a stealth aircraft can have, the biggest of all disadvantages that it faces is its sheer cost. Stealth aircraft literally costs its weight in gold. Fighters in service and in development for the USAF(United States of American Force) like the Stealth Bomber ($2 billion), Night Hawk($70 million) and the Stealth fighter ($100 million) are the costliest planes in the world. After the cold war, the number of Stealth bombers was reduced sharply because of its staggering price tag and maintenance charges. There is a possible solution for this problem. In the recent past the Russian design firms Sukhoi and Mikhoyan Gurevich (MiG) have developed fighters which will have a less price. This can be a positive step to make stealth technology affordable for third world countries.

Stealth technology is clearly the future of air combat. In the future, as air defense systems grow more accurate and deadly, stealth technology can be a factor for a decisive by a country over the other.

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