h a l f b a k e r y
Make mine a double.
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So, I was mulling over things like "smart" projectiles
can steer themselves. The example I had in mind was a
smart arrow, but smart bullets have been proposed
One common problem is that, if the target is moving,
smart projectile has to be able to follow
it. This is
if the shooter keeps a laser aimed at the moving target
(the projectile can aim towards the laser dot), but this
Ideally, one would prefer to walk up to the target, stick
adhesive marker dot on them, then step back and shoot a
projectile that homes in on that dot. However, the need
to walk up and attach the dot somewhat defeats the
purpose of the smart projectile.
So, can you "dot" a target remotely? I think you can.
instead of a regular targeting laser, have a laser
enough to heat the surface of the target by at least 50-
100°C. This can be done in a single pulse, which means
that fairly modest lasers can be used.
For a few tens of milliseconds after the pulse, the target
spot will remain hot, and should have a strong infrared
signal. The smart projectile is fired at the moment the
heat pulse is delivered, ensuring that an infrared-bright
hotspot remains on the target until the projectile
it. It doesn't matter if the target moves once the heat
pulse has been delivered - the shooter doesn't need to
track the target until the projectile reaches it.
For added discrimination (for example, if there are other
hot objects around), the heat-pulse can write a barcode
other pattern, in heat, on the target. The smart
can then track this, with less risk of being distracted by
other heat sources.
||Bejeesus that was a high-velocity bun!
||Call the target on their cell phone, and say something to anger
or embarrass them, then lock on to the heat bloom
||...and not just a high-velocity bun, a laser-tracking armor-piercing high-velocity bun.
||// a heat barcode would be worthless at the time
of writing. // Why? If I heat up the surface of a
piece of clothing (or an area or fur, or whatever)
quickly, it will retain that heat for at least a
fraction of a second. In fact, I have seen thermal
(IR) videos which show the thermal "fingerprints"
left by a warm hand on an object. I see no reason
why a barcode or other readable signal couldn't be
"heat printed" - its lifetime would be limited
(perhaps to a hundred msec or so) by the time
needed for the heat to disperse or to spread and
blur the image.
||//fire and forget missile// Yes, but I am looking
for a way to laser-designate a target that can be
hit by a smart bullet. Reliable optical tracking, I
would guess, is harder to implement in a small
||//any fine grain pattern will blur pretty quickly//
||We're talking about tens of milliseconds here - the
time it takes the bullet to travel to the target. If
the laser-made target has features on the scale of a
centimetre, it won't dissipate in that time. As I
mentioned, infrared hand "prints" left on cold
objects are visible for seconds.
||It seems like a smart projectile could use pattern
recognition to home in. Even if a thing changes its
appearance (eg turns tail to run) it changes
incrementally and this could be tracked.
||At the risk of being accused of haplotism or
epheuresis, can I suggest, [bung] that you look at
some of the superhended annotations? Image
recognition software is a bulky and, at best,
underelegant solution to the problem. Far simpler
to tag the target and then have the projectile tract
that [distinctive] tag.