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by sawjet 2846 days ago
Shape is the major determining factor for radar return, not size. From Ben Rich's Skunk Works-

>I really wanted a photographer around for historical purposes to capture the expression on Kelly’s big, brooding moon-shaped mug when I showed him the electromagnetic chamber results. Hopeless Diamond was exactly as Denys had predicted: a thousand times stealthier than the twelve-year-old drone. The fact that the test results matched Denys’s computer calculations was the first proof that we actually knew what in hell we were doing. Still, Kelly reacted about as graciously as a cop realizing he had collared the wrong suspect. He grudgingly flipped me the quarter and said, “Don’t spend it until you see the damned thing fly.” But then he sent for Denys Overholser and grilled the poor guy past the point of well-done on the whys and hows of stealth technology. He told me later that he was surprised to learn that with flat surfaces the amount of radar energy returning to the sender is independent of the target’s size. A small airplane, a bomber, an aircraft carrier, all with the same shape, will have identical radar cross sections. “By God, I never would have believed that,” he confessed. I had the feeling that maybe he still didn’t.

2 comments

>with flat surfaces the amount of radar energy returning to the sender is independent of the target’s size.

it is basic geometry. Like a flat mirror, no matter the size, will reflect to you the same Sun spotlight (to be precise - as long as the mirror is bigger than 32 arcminutes as seen from the receiving position)

Yup, shape is the biggest thing you can control, then radar absorbing and reflecting materials.

One of the big anecdotes from the early days of stealth aircraft development in the 1970s is how at some wavelengths the Hopeless Diamond shape wasn't visible to range radars at all. During one test, the range radar guys went absolutely crazy trying to detect the shape -- which was a pole model, not even flying yet -- and were about to just give up, when suddenly, there it is on their screens, plain as day. Awesome, the Hopeless Diamond lost its stealth! Or not, because what really happened was a bird landed on the pole model.

That's the power of your aircraft's shape.