Bullet flight time conventions

[Ulzgoroth]

Originally Posted by Joseph Paul

Problems I see with rifle sized homing are that they stop accelerating once they leave the barrel - they are on a glide path with a steadily shrinking area they can reach.

This is true, but I think 'glide path' isn't really the best way to think about something that's only up for a handful of seconds.

Also, steadily shrinking area it can reach applies in much the same way to high-speed missiles. Even ignoring the eventual exhaustion of their propulsion, they (like a smart bullet) will inescapably overshoot the target. As the remaining range to the target decreases, so does the space the missile can maneuver into before such maneuvering becomes irrelevant.

Originally Posted by Joseph Paul

These rules for time of flight and how hard a round can turn have to deal with more than paltry humans - various vehicles, powered armor with Superjump, Supers with enhanced move, Teleporters, magic (hello Wanda!). It pays to ask the questions and nail down how it works and of course it is GURPS so it can work lots of ways. I am just skeptical of some of them. :)

Teleporters and some kinds of magic would probably make the seeker lose track of the target. At which point if it's not a lot smarter than I'd expect in a bullet-sized package it probably will either fly dumb or attack something that was right next to the target when it disappeared.

[Anthony]

Originally Posted by Joseph Paul

Not a bullet - look at the cutaway - more akin to a gyroc. It is lit up from the moment it comes in frame

Apparently the actual tech used is classified, but even if it has a rocket assist, that's not the steering mechanism, as a rocket without gimballed thrusters can't steer itself anyway.

Speaking theoretically, any fin-stabilized ballistic projectile can adjust its course laterally by aerodynamic means, it just bleeds velocity doing so (velocity loss depends on quantity and speed of correction, and would be negligible for correction sufficient to hit something evading at human speeds). Spinning projectiles are a more complicated problem (though it's the same basic velocity bleed), though it's unknown whether the darpa bullets spin in the first place, they could easily be fired from a smooth barrel.

[Rupert]

Another problem at longer ranges is that the bullet won't actually be able to 'see' the target when it's fired, because the barrel will be pointing upwards too far. That means you're relying on the bullet acquiring the (correct) target after being fired, and soon enough that it has time to home on it. Either that or it's some kind of beam rider, command guided, or semi-active system, and all of these mean the operator is emitting right at the target which strikes me as unhealthy for the operator.

[Ulzgoroth]

Originally Posted by Rupert

Another problem at longer ranges is that the bullet won't actually be able to 'see' the target when it's fired, because the barrel will be pointing upwards too far. That means you're relying on the bullet acquiring the (correct) target after being fired, and soon enough that it has time to home on it. Either that or it's some kind of beam rider, command guided, or semi-active system, and all of these mean the operator is emitting right at the target which strikes me as unhealthy for the operator.

Short-range command-guidance via laser com to get it pointed at the right target for homing to pick up? Might be feasible for very long ranges where it's got a good few seconds in the air.

[Anthony]

Originally Posted by Rupert

Another problem at longer ranges is that the bullet won't actually be able to 'see' the target when it's fired, because the barrel will be pointing upwards too far.

If you've got course correction, there's no need to aim the barrel upwards; any viable homing round should be able to maintain a flat trajectory out to the limits of its effective range.

[Rupert]

Originally Posted by Anthony

If you've got course correction, there's no need to aim the barrel upwards; any viable homing round should be able to maintain a flat trajectory out to the limits of its effective range.

Fair enough.

I'm somewhat sceptical of the whole thing, at least for shooting at man-sized targets at range. We don't use self-homing ATGMs from ground launchers very much, and that's a much larger volume and mass available for the seeker, hunting for a much larger target.

Basically, air-to-air detection and homing is 'easy mode'. Ground targets are... not.

[Anthony]

Originally Posted by Rupert

Fair enough.

I'm somewhat sceptical of the whole thing, at least for shooting at man-sized targets at range.

Oh, there's a fine chance that it's a DARPA pipe dream, they're prone to that (and it's sorta their job).

[Joseph Paul]

Originally Posted by Ulzgoroth

This is true, but I think 'glide path' isn't really the best way to think about something that's only up for a handful of seconds.

Also, steadily shrinking area it can reach applies in much the same way to high-speed missiles. Even ignoring the eventual exhaustion of their propulsion, they (like a smart bullet) will inescapably overshoot the target. As the remaining range to the target decreases, so does the space the missile can maneuver into before such maneuvering becomes irrelevant.

Teleporters and some kinds of magic would probably make the seeker lose track of the target. At which point if it's not a lot smarter than I'd expect in a bullet-sized package it probably will either fly dumb or attack something that was right next to the target when it disappeared.

Time interval doesn't matter - if it has control surfaces and no propulsion it has a glide path - even if it is an F-4 (which was said to have the glide characteristics of a brick with the engines off)... No controls and no propulsion? It is a ballistic object trapped on a trajectory.

Re: shrinking area of opportunities - Exactly. The difference is that missiles have continuous propulsion (until the fuel runs out) and controls and bullets get one good wallop and then nothing so what ever controls they get in GURPS with a G&H system has to make do with the energy they have. If we postulate that they have some sort of energetic jet to add energy to the system then they are really a hybrid gyroc. And that stuff is generally less dense than the bullet is so we go down a rabbit hole of trading off penetrating mass for controls to raise the probability of hitting the target and it's a mess.

Re: Dumb rounds - RAW says any Homing system with IR gets a skill 13 so no downside to packing it into as small a round as allowed. That aside there are a lot of complications to think through for this tech.

Passive camouflage countermeasures, heat control/matching, active measures and intercepts. The interplay of powers.

Several posts have been about sniping but is that the best use of such technology? The intention is to raise the hit ratio of the user - one bullet, one kill. A novice may be able to do very well with such a system so that leverages the manpower and lets less skilled people do better. But you could run a sensor over a crowd or a base, pick targets in real-time and then fire a burst of active homing rounds. Do it from within the one second range to reduce some counter measures. Send an armed drone as the firing platform and remotely engage if the range is too close for the firer to escape and evade retribution. Fire from further out if there is a need to cover more wiidth. And thus begins wheels within wheels of strategy and doctrine.

[Joseph Paul]

Originally Posted by Rupert

Another problem at longer ranges is that the bullet won't actually be able to 'see' the target when it's fired, because the barrel will be pointing upwards too far. That means you're relying on the bullet acquiring the (correct) target after being fired, and soon enough that it has time to home on it. Either that or it's some kind of beam rider, command guided, or semi-active system, and all of these mean the operator is emitting right at the target which strikes me as unhealthy for the operator.

I would think that it would be possible for the round to be fed data from the sensor suite and on firing takes over control with it's own active system or continues to get the data from the sensor.

Add in as many iterations of Tracking as needed for the capacity of the magazine and the whole thing could be dumped with a round or more per each target.

[Ulzgoroth]

Originally Posted by Joseph Paul

Time interval doesn't matter - if it has control surfaces and no propulsion it has a glide path - even if it is an F-4 (which was said to have the glide characteristics of a brick with the engines off)... No controls and no propulsion? It is a ballistic object trapped on a trajectory.

Re: shrinking area of opportunities - Exactly. The difference is that missiles have continuous propulsion (until the fuel runs out) and controls and bullets get one good wallop and then nothing so what ever controls they get in GURPS with a G&H system has to make do with the energy they have.

That is technically true, but once again, it's misleading.

Yes, the bullet has only so much energy to work with. But that's not a binding constraint, because it also only has so much distance to work with before overshooting the target. And it's not likely to have enough maneuver authority to run out of energy before it runs out of space.

The smart bullet isn't performing any sort of extensive maneuvers. It's just deflecting its ballistic trajectory enough to make it pass through the target rather than pass by the target.

(A bullet, smart or not, also could be said to have much the same glide characteristics as a brick. If you threw said brick at supersonic speeds.)

Originally Posted by Joseph Paul

Several posts have been about sniping but is that the best use of such technology? The intention is to raise the hit ratio of the user - one bullet, one kill. A novice may be able to do very well with such a system so that leverages the manpower and lets less skilled people do better. But you could run a sensor over a crowd or a base, pick targets in real-time and then fire a burst of active homing rounds. Do it from within the one second range to reduce some counter measures. Send an armed drone as the firing platform and remotely engage if the range is too close for the firer to escape and evade retribution. Fire from further out if there is a need to cover more wiidth. And thus begins wheels within wheels of strategy and doctrine.

Being able to spray a burst of rounds at a scatter of targets based on the take from a separate sensor is a pretty big demand for fire control. It requires the bullets have two kinds of guidance, and receive target-designation instructions from the launcher either before or after being fired. Plus the basic added hazard of having to acquire the target with onboard sensors on the fly. If you're firing into a target-rich environment that's a good way to wind up with rounds locking on to the wrong things.