IDN: Hitler’s Secret Weapon the Horten Ho 229 Bomber was designed to carry 2,000 pounds of armaments while flying at 49,000 feet at speeds north of 600 mph. Equipped with twin turbojet engines, two cannons, and R4M rockets, the Horten Ho 229 was the world’s first stealth aircraft and took its first flight in 1944
It may surprise many, but the first rudimentary stealth aircraft was the German Horten Ho-229, made during World War II. A twin-jet, flying-wing concept, the aircraft never flew but was a prized war trophy spirited away by the US after the war for further research.
The world in general came to know about stealth in aviation when the F-117 was unveiled and went into action in the first Gulf War in 1991. With its flat, faceted plates placed at angles that gave it a peculiar triangular frontage, recessed engines and cockpit (the pilot was almost invisible from the outside), the pitch-black F-117 was the antithesis of a sleek aerodynamic design. But stealthy it was as it led the first raid into Iraq. For the world, stealth had arrived.
Stealth is not just “invisibility” to radar, but also includes aural, visual and thermal signatures—anything that gives away its presence. Thus, it is a package of steps taken to delay, as far as possible, or deny the knowledge of existence of a body.Aural signatures may not be very important for fast jets but are vital for helicopters and unmanned aerial vehicles (UAVs) that have to fly close to enemy lines, and many times at low altitudes. Low visual signatures are a must for any type of stealthy machine for it reduces the time available to observers to track it and train their weapons. Low thermal signatures come into the equation to ward off thermal detection by capable imaging systems mounted on surveillance, tracking and targeting systems.
However, the denial of radar detection is the real art in stealth and the subject of breathless research the world over—so also is the research into beating stealth. Thus, even as the B-2 stealth bomber came into public knowledge in the 1990s, its technology was already obsolescent, with the world experimenting with fancy carbon nanotube paint and cenospheres to decrease the radar cross-section of stealth aircraft. The “antidotes” too are progressing—as Popular Science magazine wrote: “Even these radar-cloaking techniques may be rendered obsolete one day.” In 2012, scientists from the University of Rochester in New York demonstrated a way to use the quantum properties of photons to create a reportedly “unjammable aircraft detection system”.
From a macro perch, modern stealth technology involves two facets. Firstly, tailored physical construction in terms of shapes, geometry and precise positioning of major radar-reflecting parts of an aircraft. The radar may still register pick-ups of some reflected energy, but because the signal would be weak, or received very late, the aircraft could still execute a stealthy approach and get away. Thus, the flat angular plates of the F-117 have given way to the sleeker panels on the F-22 Raptor and F-35. The Chinese J-20 and J-31 too have a very similar design. The engine intakes are finely contoured and the engines positioned such that they are shielded from direct radar waves because their compressors act as good flat plate reflectors of radar waves. In the case of UAVs, special engines and propellers have been manufactured so that above a certain altitude, the UAV becomes inaudible to an observer.
Secondly, special paints are used to “absorb” radar waves and convert them to heat, which is dissipated into the atmosphere; ferrite tiles and carbon-fibre epoxies, if used in fuselage construction, themselves absorb radar waves.
UAV operations in Iraq, Afghanistan, Yemen, etc., do not require them to be stealthy since the airspace they operate in is uncontested—there is no adversary that can present a threat with air defence systems or fighter aircraft. In contested airspaces, there would be adversarial action for which the US and the UK already have machines in the test-flying phase—the RQ-180 and Taranis, respectively. The Taranis is a compact and stealthy unmanned combat aerial vehicle (UCAV) that would be able to engage enemy aerial vehicles in combat, even in a head-on mode. The RQ-180, teamed with a manned surveillance aircraft (which would stay in friendly airspace), would penetrate deep into enemy airspace to carry out electronic surveillance and maybe electronic attacks too.
In India, stealth as a concept is yet to be implemented on any aviation product; in fact, the first aircraft to be designed from scratch with stealth as an air force requirement would be the advanced medium combat aircraft (AMCA). Still on the drawing board, the AMCA would be a fifth-generation fighter that would be the mainstay of the IAF in the 2030s and beyond.
Another Indian project, though way into the future, is the Aura, a UCAV being planned by the Defence Research and Development Organisation. Planned to be stealthy, the Aura would test Indian aerodynamicists and engineers to deliver the advertised capabilities, which are based on its flying wing design. The IAF’s fifth-generation fighter aircraft would also be in the stealth class, but this is being co-developed with Russia.
The new ships of the Indian Navy are being made with stealth features too. In the case of marine vehicles, besides the requirement to reduce the visual and infrared signature and the radar cross-section, it is an imperative that acoustic, magnetic, electric and hydro-dynamic wake signatures also be minimized.
There is obviously a price to pay when engineers have to tweak the balance between the level of stealth sought and performance of aircraft (and ships). Some navies have given up the idea of building stealth into their naval assets when the high costs involved are balanced against the advantages obtained in the maritime domain. This choice, however, is not available in air warfare, as in the future an air force would be counted among one of two types—one that has stealth and is invisible (in a manner of speaking) and one that doesn’t.
The author, a retired air vice marshal, is a distinguished fellow at the Centre for Air Power Studies, New Delhi. The views are personal.