“Leading”, with a long “e”, refers to the technique of aiming at a moving target and moving your point of aim to a position so that your projectile hits the moving target. This involves actually shooting, not directly at the target, but at the pint where the target will be in the time it takes for your projectile to get there.

For us tankers, we started out with a standard lead of five mils, figuring that our moving target was doing ten-fifteen miles per hour and our projectile would leave the barrel and average a bit over a thousand meters per second. At a thousand yards, this means that the target moves forward fifteen or so feet and if we’ve aimed five mils ahead of where we wanted to hit, that’s right at five meters, or fifteen feet. Bingo! A neat hole in the target!

These calculations are exercised every day at tank ranges around the world.

Now, let’s expand the problem a bit. Assume that the target is a school bus sized satellite orbiting a hundred and fifty miles above the earth and instead of a sweet little 105mm gun, you’ve got a missile… Your target is moving at 17,000 MPH.

It’s a bit tougher, ain’t it?

Somebody, though, figured it out as the Navy launched a missile to tear up a satellite in a decaying orbit.

I lifted this graphic from the BBC article:

1 SM-3 missile launched from a US Navy cruiser in Pacific Ocean
2 The three-stage missile headed for collision location, where the relative “closing” speed was expected to be 10km/s (22,000mph)
3 Satellite came in range at altitude of 247km (133 nautical miles), close to edge of Earth’s atmosphere
4 Missile made contact with satellite with objective of breaking fuel tank, freeing hydrazine into space
5 Much of the debris will burn up but an as yet unknown amount is expected to be scattered over hundreds of kilometres

Yeah, you can talk about the radar tracking and in-flight correction and all that, and it’s true, but please note that this was a “kinetic energy” missile. That means that the warhead is a big chunk of something hard, and nothing less than a direct hit would count. As the saying goes, “‘Close’ only counts in horseshoes and hand grenades”.

A school bus is what, about forty feet long? And that was a hundred and fifty mile shot? That works out to hitting a quarter of an inch MOVING targetAT A HUNDRED YARDS, on the first try.. That’s one fine shot!

And if the rest of the world happens to look at this and think, “Wow, those ba*tards can SHOOT!”, well, we’ll just call that a happy coincidence of the project…