Stealth: radar cross section and how to shrink it

Prelims and MainsCurrent affairs on this: Military platforms, drones and new weapons

A radar finds an aircraft or ship by sending a radio pulse and listening for the echo; the strength of that echo is the target's radar cross section, in square metres: a bomber reflects like a barn door, a stealth fighter like a bird. Stealth is engineering the target so the echo goes anywhere but back to the radar. Shaping does most of the work: facets and aligned surfaces bounce the pulse to the side, and curved inlets hide the engine fan. Radar absorbing materials on the skin turn the rest of the pulse into heat. Weapons are carried inside so no bomb or missile adds its own reflection, and exhaust is cooled and shielded to hide from infrared sensors. Stealth is not invisibility: long wavelength radar still sees the shape, and an aircraft that opens its bay or switches on its own radar can be found.

Conventional against stealth design

	Conventional aircraft	Stealth aircraft
Shape	rounded fuselage, vertical fins, external stores	flat facets and aligned edges, canted fins, smooth blended body
Weapons	on pylons under the wings	in internal bays
Inlets	straight duct, fan visible to radar	curved duct hiding the fan
Skin	paint	radar absorbing coatings
Exhaust	round hot nozzle	flattened, cooled, shielded
Radar cross section	square metres to tens of square metres	fractions of a square metre
Cost of the trade	cheap, easy to maintain	expensive coatings, limited payload, careful maintenance

Stealth is a set of trades: payload and cost for a smaller echo.Source: Standard aerospace references

India's programmes: the Advanced Medium Combat Aircraft (AMCA), a fifth generation stealth fighter approved for development in 2024 with internal weapons bays and, in later versions, an Indian engine; the Project 17A Nilgiri class stealth frigates built at Mazagon and Garden Reach, with angled hulls and enclosed decks to cut their radar signature.
What "fifth generation" means: stealth, sensor fusion, supercruise (supersonic flight without afterburner) and networked operation; the F 22, F 35, Su 57 and J 20 are the reference points, and India's Tejas is fourth generation plus.
Ship stealth is about the same physics at larger scale: sloped superstructures, hidden mooring gear and cooled funnels; a frigate cannot hide but can look like a fishing boat on a long range radar.
The counters: low frequency and passive radars, infrared search and track, and networking many sensors so the small echo is caught from several angles; stealth versus counter stealth is the arms race of the decade.
Drones change the arithmetic: a swarm of cheap unstealthy drones can saturate a defence that a single stealth aircraft would have to sneak past.

Mains: Stealth matters less for what it hides than for what it forces: an opponent must buy new radars, network its sensors and spread its defences, and that cost imposition is the strategic purpose of the AMCA.

UPSC has asked

Prelims 2026: stealth technology, radar cross-section and radar absorbing material