The stealth feature in the fighters comes at a huge, often unaffordable, cost
Girish Linganna
With booming technological brilliance, modern warfare is becoming more and more complex. Nations are now investing heavily in R&D in the defence sector, particularly in military airborne platforms. This is focused around multiple aspects such as electronic warfare (EW) suite, speed, weapons integration, etc. One such important aspect of modern aircraft is radar detection-defying stealth.
Stealth or low observable (LO) technology aims to render personnel, equipment, and vehicles less visible to detection methods such as infrared, sonar, radars etc. By extension, stealth aircraft are planes, helicopters etc. that are designed to use stealth technology to avoid detection. The US-based aerospace firm Lockheed Martin developed the first ever operational aircraft designed specifically with stealth technology—the F-117 Nighthawk. We have come a long way since then, with the development of various stealth aircraft such as the Sukhoi Su-57, Shenyang FC-31, Chengdu J-20, B-2 Spirit, F-22 Raptor, and F-35 Lightning II.
Basics of a stealth aircraft
The most important principle in building a stealth aircraft is that there should be no projections or extensions of any sort on the fighter. This means that easily detectable parts such as the tail surface, propellers, jet turbine blades, compressor blades, the leading-edge of the wings, weapons, fuel tank—all have to be optimised to avoid radars.
This has been done in different ways in various aircraft. For instance, the Nighthawk adopted tilted tail surfaces to reduce reflections. The B-2 Spirit, on the other hand went to the extreme of dropping the tail entirely, thus achieving a near-perfect stealth shape with no angles to reflect radar waves.
In addition to hiding pointy, angled surfaces, a good stealth design will also need to hide the engines within the wing or fuselage (the main body of the aircraft) or install baffles in the air so that the compressor blades remain hidden to radar.
Design aside, use of specific radar absorbing materials is also important in stealth technology. These materials must be used to build the aircraft cone and the leading edge of the wing in order to trap the waves. The cockpit canopy is coated with a film of transparent conductor to minimise radar reflections from the cockpit and pilot’s helmet. Recently, dielectric composite materials have come to replace electrically conductive materials like metals and carbon fibres.
Yet another important aspect of stealth aircraft is the focus on reducing the radar cross section (RCS) of an aircraft. RCS is the measure of the detectability of an aircraft by radar. Lower the radar signature, lesser the detectability.
Metasurfaces—thin two-dimensional meta-material layers that enable or inhibit the propagation of electromagnetic waves in chosen directions—have helped in significantly reducing RCS. Metasurfaces have the capability to redirect scattered waves without modifying the target’s geometry. Another technology proposed to reduce radar signature is plasma stealth. This suggested process would use the interaction between ionized gas (plasma) and electromagnetic radiation to create a layer of plasma around the platform to deflect or absorb radar. Efforts are also underway to integrate the functions of aircraft flight controls into wings. This would reduce the weight, number of moving parts, and the cost of the aircraft, in turn leading to lower RCS. A flexible wing that can change shape in flight to deflect airflow is in the pipeline while adaptive aeroelastic wings are also being researched.
Stealth Aircraft Detection
Stealth aircraft are detected almost the same way as any other aircraft. The difference is largely in terms of difficulty. For instance, a radar will still be able to detect a stealth aircraft. However, it will not be able to do so until such an aircraft is very close, minimising the response time and making a counter-attack nearly impossible. The situation is similar in case of IR signatures of stealth aircraft. While these aircraft do emit infrared signatures, they take efforts to diffuse and minimize the same. This makes it much harder to detect from a distance.
Two other methods of detecting aircraft look for the acoustic and visual clues. Stealth jets, like all planes, make sound despite employing methods to suppress it. However, sound moves slowly compared to something like radar signals, and is difficult to use for targeting or even pinpointing correct location/ direction. To avoid visual detection, stealth aircraft use the same camouflage paint scheme as other fighter jets. Yet, visual detection ranges are frequently too close to be of much tactical value.
Despite these measures, development in technology has provided some drones, in particular, with great abilities for addressing all of these detection methods.
Drawbacks
It is quite clear that stealth combines several technologies that significantly reduce the distances at which the enemy can detect an aircraft. Since 1990, when the concept first garnered public attention, ‘stealth’ as a technology is being incorporated at the design stage itself. Air forces’ designers are focusing on evolving more and more stealth features. They are also simultaneously building features to beat and penetrate the stealth effect. Passive infrared (PIR) sensors, multi-static radars, very low-frequency radars, and over-the-horizon radars are some counter technologies that are being developed.
USA and Israel are the only two countries that have used stealth aircraft in combat. This was done in 1990 during the Gulf War- the F-117s managed to land direct hits of 1,600 high-value targets in Iraq over the course of 1,300 sorties. The F117s comprised only 2.5 per cent of the American aircraft in Iraq, yet they managed to strike 40 per cent of the strategic targets with an 80 per cent success rate. That data point alone could be interpreted to mean that stealth aircraft are extremely efficacious and powerful.
However, there is a flip side to the coin. Stealth aircraft are design intensive—demanding personnel and having lengthy timelines. Extensive testing can be arduous, time-consuming, and costly. The composite materials used for building stealth aircraft are expensive and difficult to source. Moreover, maintaining these planes is also a pricey task.
Accordingly, the cost-to-benefit ratio does not speak well for stealth planes. The high expenses involved in acquiring, operating, and maintaining stealth jets means that they must be used sparingly. Many long-range air-to-air missiles are hard to carry internally in most fighter planes, something that needs to be done for stealth aircraft as external hardpoints and canard controls and aircraft external hardpoints are ‘stealth killers’. Besides, many stealth carriers are not completely foolproof to radar. Numerous aircraft specialists have recommended alternatives.
For instance, a quick, well-armed, and highly manoeuvrable jet of the class of Boeing EA-18G Growler has the ability to jam across the entire spectrum. Suppression of Enemy Air Defences (SEAD) also is suggested as it is much cheaper than stealth. Some experts have argued that stealth is overrated, further claiming that buying greater numbers of cheaper, non-stealthy planes would be better.