I just measured a .50 BMG round I have here at hand, and they’re 5.5 inches.
You’re right about the laser modulation as well, and probably an encrypted ID carried in that stream so that the bullet knows its target from, say, the one that just got fired at another vehicle by the guy next to you.
It seems to me this would be vulnerable to dazzling technologies, where the target has lasers oriented toward the possible threat, and that bright light could blind the various optics involved.
EDIT: Wiki says .50 BMGs are 5.45", but my wooden ruler doesn’t have that kind of resolution.
“True to DARPA’s mission, EXACTO has demonstrated what was once thought
impossible: the continuous guidance of a small-caliber bullet to
target,” said Jerome Dunn,
DARPA program manager. “This live-fire demonstration from a standard
rifle showed that EXACTO is able to hit moving and evading targets with
extreme accuracy at sniper ranges unachievable with traditional rounds.
Fitting EXACTO’s guidance capabilities into a small .50-caliber size is a
major breakthrough and opens the door to what could be possible in
future guided projectiles across all calibers.”
In weapons speak, “Small Arms” is anything a soldier can hold and fire. So that would include rocket propelled grenades, mortars, large machine guns (but usually not mounted guns), or even, arguably, the nuclear Davy Crockett RPG that the US military used to field.
EDIT: I’m still learning how to link properly on this BBS, sorry about that.
I’d imagine it’d be prohibitively expensive to equip as standard, and, as you state, any recovered ballistics can be used to reverse-engineer the tech, thereby negating the ‘surprise’ advantage.
I think they plan using it against soft targets, like tribal leader assassinations. These don’t typically have vehicles with advanced electrooptical systems.
Todo: figure out how to make such system on an Arduino…
Having read a great number of your posts in the past, I imagine your ‘to-do’ list is growing rather lengthy.
EDIT:
If the beam is neither modulated, nor filtered, it would be as easy as using laser-pointers to deflect. I don’t think it would require massively advanced electrooptical systems to encode or filter it either. Possibly even,as you say, as small and simple as an arduino.
Yes, by now the list doubles as a highway measurement tape.
There will certainly be some sort of modulation. An unmodulated beam is just a dot, difficult to recognize from all the clutter around. A modulated one is much easier - “look for something that blinks at (say) 40 kHz”, or “maximize the 40-kHz optical signal on the sensor, minimize its wobble” is fairly easy to implement even on analog tech (see the early laser-guidance systems).
An unmodulated laser pointer could work to dazzle the sensor, saturate it so it won’t respond to the modulated reflected signal anymore, but that requires precision aim in real time. Which I’d consider rather difficult. A receive-and-retransmit signal scheme, with a disposable target, e.g. a wireless-linked battery-laser thing that gets ejected from the vehicle with hope that the bullet will track it (or sprung out on an “antenna”, or thrown out with a trailing wire to feed with power and data - would not be jammable, something like what’s done with wire-guided missiles) could work here. Or an electrooptics turret that senses the vehicle being painted with the target designator, and illuminating self with stronger, brighter dot with the same signal (receive-retransmit), then sweeping it away to lure the bullet away like a cat with a laser pointer.
Of course the counter-countermeasure to a laser guided bullet would be to first hit the target with an ordinary bullet and wait for it to stop moving. That way its ability to deploy any countermeasures to the fancy bullet is severely curtailed, and even in the case of automatic detection/deployment, you wouldn’t need the laser bullet to do anything special to hit the now immobilized target.
