A modern stealth aircraft like the F-22 Raptor has the radar cross-section of a marble. A non-stealth fighter like the F-15 Eagle? About the size of a pickup truck. That difference — from clearly visible to nearly invisible on radar — is what stealth technology achieves. But how?
What Is Radar Cross-Section (RCS)?
Radar works by sending out radio waves that bounce off objects and return to the receiver. The strength of that return signal depends on the object’s Radar Cross-Section (RCS) — not its physical size, but how effectively it reflects radar energy back to the source.
RCS is measured in square meters:
- B-52 bomber: ~100 m² (enormous radar return)
- F-15 Eagle: ~10-25 m²
- F/A-18 Super Hornet: ~1-3 m²
- F-35 Lightning II: ~0.005 m² (a golf ball)
- F-22 Raptor: ~0.0001-0.001 m² (a marble to a metal ball bearing)
- B-2 Spirit: ~0.0001 m² (an insect)
The Four Pillars of Stealth
1. Shape (Planform Alignment)
The most important factor. Stealth aircraft use carefully angled flat surfaces that reflect radar energy away from the source rather than back to it. All edges — wing leading edges, tail surfaces, intake lips — are aligned to the same few angles. This concentrates radar returns into narrow “spikes” in directions away from the threat radar.
This is why stealth aircraft look so distinctive — the F-117 Nighthawk’s faceted diamond shape, the B-2’s flying wing, the F-22’s angled surfaces — they’re all optimized to deflect radar.
2. Radar-Absorbing Materials (RAM)
Special coatings and materials that absorb radar energy and convert it to heat rather than reflecting it. Modern RAM includes iron ball paint, carbon-fiber composites, and specialized multi-layer coatings. The F-117 and B-2 required extensive (and expensive) maintenance of their RAM coatings; newer aircraft like the F-35 use more durable materials.
3. Internal Weapons Carriage
External weapons — bombs, missiles, fuel tanks — create massive radar returns. Stealth aircraft carry weapons in internal bays, keeping the outer surface smooth and radar-reflective surfaces hidden. The F-22 carries six AIM-120 AMRAAMs and two AIM-9X Sidewinders internally.
4. Engine/Intake Design
Jet engine fan blades are excellent radar reflectors. Stealth aircraft use serpentine (S-shaped) intakes that hide the engine face from incoming radar. The intake ducts curve so that radar waves entering the intake bounce off the walls and get absorbed before reaching the reflective engine.
Beyond Radar: Other Signatures
True stealth requires managing multiple signatures:
- Infrared (heat): Flat, wide exhaust nozzles spread and cool the exhaust plume. The B-2’s engines are buried deep in the wing to shield their heat from below.
- Visual: Reduced contrails, camouflage paint schemes, smaller overall size
- Electronic emissions: Low-probability-of-intercept (LPI) radar that’s hard to detect. Passive sensors that listen without broadcasting.
- Acoustic: Less relevant for high-altitude operations but considered in design
Can Stealth Be Defeated?
No technology is invincible. Potential counters include:
- Low-frequency radar: Longer wavelengths can detect stealth aircraft, but with poor accuracy — good enough to know something is there, not good enough to guide a missile
- Bistatic/multistatic radar: Separate the transmitter and receiver so reflected energy doesn’t need to return to the source
- Infrared Search and Track (IRST): Passive heat sensors that don’t rely on radar at all
- Networking: Sharing data from many sensors to build a composite picture
The cat-and-mouse game between stealth and detection continues to drive innovation on both sides.
Dive deeper with our How Stealth Technology Works page, or explore stealth aircraft in our collection.