Everyone’s talking about how the F-35 Lightning II has a RCS the size of a Golfball but I don’t know what it means or how significant it is.
In: 5
Everything has a radar cross section.
Radar works by sending out an electro magnetic pulse and then listening for a bounce back. By counting the milliseconds between when you sent out the pulse and when you got a bounce back you now have a range, and by observing from what direction you got the bounce from, you now have a bearing (there are two types of radars, directional and non directional, but Im gonna skip that for now).
So anything that can reflect the frequencies that various radars send out their pulses in has a radar cross section. The term “cross section” stems from the historical early radars where in most cases the size of the “blip” on the radar scope was really just a reflection of the thing’s size. Big ship or airplane == bigger blip.
Now, there’s a few things that influence how big your bip is to a radar: size is obvious, but there’s also:
– incident deflection: if you form the body of your plane with flat surfaces angled away from the radar, it will bounce the radar pulses alright, but it will angle them away from the radar, so it never sees the return pulse.
– this same effect can come from interesting aspects of your plane. The turbine blades inside the jet engine for one – huge reflectors of radar pulses. But if we can _hide_ the blades inside a duct or deep within a nacelle, the radar won’t get a bounce back from the blades.
– radar absorbing paints and materials: can’t send back a radar bounce if you absorb it.
Large flat rounded surfaces have _Huge_ radar cross sections: there literally is a huge area to bounce a radar signal back from. So do large straight seams between panels. So stealth aircraft will make a door or a panel with a zig-zag shaped door so the edge of the door or panel has lots of little angles that will bounce a radar signal off in different directions instead of all back in one direction (if it happens to be in the direction of the radar).
Old warships have a lot of flat vertical walls that make up the superstructure. When the angle to the radar is right, those will just bounce the whole radar pulse right back to the radar receiver. MOdern warships have flat panels that are angled away from vertical so any radar pulses are bounced up and hopefully away from the radar receiver.
So an airliner has all these large flat or rounded body panels, they reflect huge radar signals. Stealth aircraft will reflect very little, and this is on top of what their skin absorbs using special materials.
So when they say the F-35 has the RCS of a golfball, they literally mean, at the same distance, the F-35 will reflect the same about of radar reflection as a literal golf ball. THat’s pretty good. The RCS of a 747 is about the same as a barn.
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