[InclinedPlane]

Let's continue this digression.

Fun fact I learned recently about guided missiles (I have diverse interests), modern ones don't adjust to aim directly at the target, they adjust to keep the target at the same relative angle (the same position on the imager). This has the effect of leading the target and flying an intercept course instead of a following course, which is more efficient and effective.

[mpyne]

Interestingly, the fun fact is something any mariner could have told a missile designer. We call it CBDR; Constant [relative] Bearing, Decreasing Range.

Stay in CBDR for long enough and you're pretty much guaranteed a collision.

[marklabedz]

Dogs catching frisbees employ a similar methodology: http://digitalunion.osu.edu/r2/summer06/maynor/journal_artic...

[kevinconroy]

I heart comment chains like these. Thanks for the wonderful side trip of interesting but unrelated facts!

[arethuza]

This video of the Sprint ABM missile (0 to Mach 10 in 5 seconds!) shows it intercepting a ICBM RV in a test - given the speed of the RV it does look like the missile is aiming where the RV is going to be rather than where it is - and this is from the 1970s:

http://www.youtube.com/watch?v=msXtgTVMcuA

[InclinedPlane]

Another fun fact, the Sprint's first stage only fired for 1.2 seconds.

[Gravityloss]

Umm, "modern ones"? Meaning practically the first one, Sidewinder: http://en.wikipedia.org/wiki/AIM-9_Sidewinder#History

"The Sidewinder also included a dramatically improved guidance algorithm. The Enzian attempted to fly directly at its target, feeding the direction of the telescope into the control system as it if were a joystick. This meant the missile always flew directly at its target, and under most conditions would end up behind it, "chasing" it down. This meant that the missile had to have enough of a speed advantage over its target that it did not run out of fuel during the interception.

The Sidewinder is not guided on the actual position recorded by the detector, but on the change in position since the last sighting. "

[InclinedPlane]

By "modern" I mean a subset of systems which excludes first generation systems as well as some second and other generation systems, it's generally just simpler to say "modern" than be more specific. If I said "modern computers use integrated circuits" the timeline of modernity would be clear, I don't mean state of the art, just not archaic.

[badgar]

> By "modern" I mean a subset of systems which excludes first generation systems as well as some second and other generation systems

The word you're looking for is "mature."

[InclinedPlane]

Maturity of a technological system to me implies a plateau of design, but that's not the case in missile guidance. Current generation systems are significantly more advanced and more capable than previous generation systems.

[Gravityloss]

Yes, sorry for nitpicking but I just think that the word choice was perhaps not good. I'd think modern missiles means something much more recent easily, when this is talking about something practically existent for the whole development time of missiles. Sidewinder development was started in 1946.

[dubya]

To get back to sports, this is also how outfielders (in baseball) catch fly balls: http://psychology.clas.asu.edu/files/2002_JEP-HPP%28Uncatcha...