The History of Stealth in Aviation I

The idea of creating stealthy aircraft capable of avoiding detection is as old as the idea of using aircraft in war. All the way back in World War I the Germans created the Linke-Hofmann R.1. This was an attempt to create an aircraft that the enemy would see straight through, and they did so by replacing much of the canvas on its body with cellophane. This ended up having the opposite effect, however, as it would catch the sun's rays and reflect them brightly into the enemies' eyes. Despite its failure though, it shows forward thinking on their part and represented a first step towards stealthy aircraft.

These days stealth is generally referred to as LO, or Low Observable. This description has five major elements to it:

1. Radar Cross Section (RCS)

2. Acoustic Signature

3. Infrared (IR) Signature

4. Visibility

Today, I'm going to be discussing the first of these elements: Radar Cross Section.

Radar Cross Section (RCS) is a relatively simple concept. It is the magnitude of radio waves that a given object reflects back to the source (the radar station), and as an extension how detectable the object is to Radar.. How radar stations work is that they emit radar waves into the air and wait for them to reflect off an object and come back. They then receive these reflected waves and use the time interval and the magnitude of waves received to determine how big and far away an object in the air is. It then displays these reflections as blips on a screen.

There are a few ways to reduce the chances of being spotted by radar. The first, and perhaps most effective, method is to design the plane so that it reflects radar waves away from the source rather than towards it. A second way to reduce a plane's RCS is by coating it with special radar absorbing materials.

These methods were, for a long time, incredibly difficult to employ in practice just because of the complexity of the calculations involved with determining how radar would reflect off curved surfaces. This led to the development of the F-117 Nighthawk, a stealth bomber with no curved edges. Strange as it looked, it had an RCS of only 0.003m^2, barely that of a hummingbird!

A U.S. Air Force F-117A flies over Nellis Air Force Base

(Image Credit: Staff Sgt. Aaron Allmon II, Aug. 6, 2002)

As computers became more powerful, however, using curves in the plane's design became viable and this along with various other design elements contributed to the development of the B-2 Spirit. With its advanced design and the use of proprietary materials to absorb and reflect radar waves away from stations, this plane reduces its RCS down to 0.0001m^2! That's the same as a bee!

A USAF B-2 Spirit soaring over the Pacific Ocean after a refueling

(Image Credit: Staff Sgt. Bennie J. Davis III, May 30, 2006)

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