Bullet flight time conventions

[Joseph Paul]

EDIT - Oh my! Such mathy endeavors! Response below written before seeing these.

Nope, pretty much I understand homing. Pretty sure a lot of people are influenced by popular depictions of it though and I am nixing that.

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. I am dubious of any kind of wing or fin arrangement for the 10-15mm range which leaves active skin or maybe a memory metal jacket that forms a lifting body shape. How that works while spinning several hundred times a second I am not sure. I am not sure if the Copperhead spins or not once the glide wings are deployed but I doubt it. I have my doubts about stability of spinning rounds that try to change direction. Heck they might get into a tumble if CG and CP get out of whack. And I don't know what it costs the round in range to make a turn.

Playing with a triangle calculator and assuming that the 15mm AM rifle does 1000 yps making a 1 deg change at 1000 yards after firing allows the round to move left or right ~139 yards over 8000 yards of travel. Making a 1 deg shift at 8000 yards it only covers ~17.5 yards. A 10 degree shift at the same ranges allows ~1410 yards of shift and ~176 for the last 1000.

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. :)

[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.

[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.

[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.