(passive) sonar for detecting planes

[jrtom]

no, seriously: http://www.boingboing.net/2009/03/03/britains-vast-cement.html

Superseded by radar, and apparently doesn't help much with faster planes, but one wonders whether this might be an effective technique for detecting stealthed aircraft.

Comments

[zandperl.livejournal.com]

Do stealthed aircraft tend to break Mach 1? If so, it's 100% useless. If not then it's only useful for warning if the plane is slow. I'd be more interested to know if there's a way to set microphones/pressure sensors up on planes in the air to detect changes to the air around them such as the wake of a plane that's passed. Then you could mount them on a fast plane and have it canvass sensitive areas. Again, it probably wouldn't be good for catching/stopping the stealthed plane, but at least you'd know if it'd been there.

[jrtom.livejournal.com]

You have a good point (in much the same way that radar is presumably less useful for detecting superluminal craft :) ). I would assume, though, that while stealthed aircraft are often _capable_ of breaking Mach 1, they probably don't tend to do so when they're trying to be stealthy because the sonic boom is kind of a giveaway. Same reason that some guns that are designed to be silent use subsonic rounds.

As for it being useful in inverse proportion to the speed: maybe. However, if you own enough territory between where the stealthed plane takes off and its target, then you can set up sensors that will tell you that it's just passed through (and probably give you a vector if you've got enough data to triangulate). Remember that the sensors don't have to be exactly where the countermeasures are. :)

[zandperl.livejournal.com]

Oh good point! I was assuming the sensors had to be near the sensitive target.