[Ultra-Tech] worries concerning ETC weapons

[Agemegos]

I understand that the boofiness of personal firearms is limited by weight and ergonomics. We can already make pistols, SMGs, and rifles that are too heavy to carry, that require ammo that is too heavy to carry, that kick and flash more than shooters will put up with, or that have their ammo capacity reduced to meet weight limits. We can do that without ultra-tech, just by using oversized cartridges.

So what's the go of ETC weapons in Ultra-Tech? They get 1.5 times piercing damage, which means 2.25 energy, right? The energy has to come from somewhere. ie. from the battery in the weapon. And that means that unless we have superscience batteries but not superscience propellants the extra battery storage has to weigh about 1.25 times as much as the propellant in the cartridges. That ought to push up weight-per shot (inclusive of batteries) just the same as packing in more propellant would. Also, the batter has to go somewhere. It presumably takes up about as much space as the propellant in the cartridges. Which argues that either the weapons ought to be bigger or that the batteries take up part of the magazine, reducing magazine capacity.

In short, unless batteries have a much higher energy density than propellants (and I can't see why they should) it seems to me that ETC weapons should be heavier or have a lower ammo capacity, and in either case have a higher total weight per shot, than conventional equivalents.

Further, there is this thing about recoil not being increased. I can't see how that is possible. Conservation of momentum dictates that the mechanical energy produced must be partitioned between (muzzle energy + energy of propellant gases in the muzzle flash) and recoil energy in the inverse ratio of the masses involved. If recoil is not increased the extra energy of the bullet has to come from reduced energy of the flash, and I just don't think there is enough energy in the flash for the sums to add up.

So am I missing something, and if so, what? Or are ETC weapons un-labelled superscience?

[Langy]

The energy has to come from somewhere. ie. from the battery in the weapon.

That's not where ETC weapons get their extra energy from. They do it by making the propellant more efficient, not by adding more energy from a battery.

Also, you're conflating Rcl and recoil. Remember that GURPS Rcl is not real-world recoil, whose closest approximation in GURPS is the ST requirement.

It is unclear whether or not the weight of the batteries should be added to the weight of the weapons or not, but I think the assumption is that the battery just replaces structural material, which is why there is no weight gain.

[Agemegos]

Originally Posted by Langy

That's not where ETC weapons get their extra energy from. They do it by making the propellant more efficient, not by adding more energy from a battery.

"Efficient" Two and a quarter times as much mechanical energy out of the same chemical reaction? Are firearms really that inefficient?

Also, you're conflating Rcl and recoil.

No I'm not. No more than Ultra-Tech does. "...without a significant increase in recoil" is what it says. It makes no mention of Rcl or ST either.

It is unclear whether or not the weight of the batteries should be added to the weight of the weapons or not, but I think the assumption is that the battery just replaces structural material, which is why there is no weight gain.

If that structural material isn't needed for structure, why don't we just leave it out?

[lexington]

Originally Posted by Brett

"Efficient" Two and a quarter times as much mechanical energy out of the same chemical reaction? Are firearms really that inefficient?

Yes.

ETC is a real technology by the way, so certainly not superscience.
http://en.wikipedia.org/wiki/Electro...cal_technology

Originally Posted by Brett

If that structural material isn't needed for structure, why don't we just leave it out?

Strictly speaking I don't think most of a gun is "needed" but weight helps reduce felt recoil and those extra bits give you the fun bits like a handle, sight and other ergonomics.

[Agemegos]

Originally Posted by lexington

ETC is a real technology by the way, so certainly not superscience.

It's not doubling the muzzle energy of smallarms without increasing weapon weight, weight per shot, or recoil, though. At best it is promising to improve the ignition characteristics of propellant in very large chambers.

Even if the same thing did work in smallarms (where the whole chamber is within the flash of the primer) there remains the problem that people firing smallarms can't handle much more. The 10mm Auto cartridge is losing out to the 10mm S&W because it is simply too much for most people to fire without making the guns heavier. The Desert Eagle and .44 Automag and than Wildey thingo are impractical because they throw too much lead too fast.

[lexington]

Originally Posted by Brett

It's not doubling the muzzle energy of smallarms without increasing weapon weight, weight per shot, or recoil, though. At best it is promising to improve the ignition characteristics of propellant in very large chambers.

With better energy density reduced weight per shot would seem to be an obvious outcome. I don't know enough about the technology to answer the rest.

Originally Posted by Brett

The 10mm Auto cartridge is losing out to the 10mm S&W because it is simply too much for most people to fire without making the guns heavier. The Desert Eagle and .44 Automag and than Wildey thingo are impractical because they throw too much lead too fast.

That's just an argument for not using ECT in small arms, not for it being impossible. Or I guess you could just use a smaller charge?

[Anthony]

Originally Posted by Brett

"Efficient" Two and a quarter times as much mechanical energy out of the same chemical reaction? Are firearms really that inefficient?

Usually not precisely the same reaction, and it lets you just use more propellant.

[malloyd]

Originally Posted by Brett

"Efficient" Two and a quarter times as much mechanical energy out of the same chemical reaction? Are firearms really that inefficient?

Worse. The difference between explosives and fuel/oxidizer mixtures isn't quite a factor of 10. Though of course that isn't really the problem or you could just use more gunpowder. The gain to be had from changing reactants is an energy partition issue, the fraction of the energy carried off by the exhaust gases is of course lower if you reduce the weight of the gases, and in a conventional firearm that can be in the vicinity of the weight of the actual bullet, divide that weight by that factor of 10 (same energy yeild with less propellant) and that's available for the bullet.

The big gain in liquid propellant though is the better burn control - ideally you'd like the propellant to burn just behind the bullet as it moves down the barrel, with the burn rate increasing as it does so that the pressure behind it stays constant even as the bullet accelerates and the volume behind it increases. This lets you use more propellant for the same maximum barrel pressure (or gun kick I suppose), and in any case even with the same energy you get better energy transfer - more or less the same concept as impedence matching.

You can control that some with the shape and compression of the individual powder grains - this is why stuff like compressed powder, or charges with holes drilled down the middle are worth doing, but individual shaping and careful layering of additives like we do for solid rocket fuels would be insanely expensive for each grain of powder. It's much easier with liquid fuel, for either guns or rockets.

[Captain-Captain]

Originally Posted by Brett

"Efficient" Two and a quarter times as much mechanical energy out of the same chemical reaction? Are firearms really that inefficient?

Sound, that can be heard over a mile away, waste heat, that can render the gun inoperative with prolonged* use, often requiring cooling systems be built into the gun, propelled unburnt spewed out as gunpowder residue all indicate a good amount of waste energy in the process.

*'Prolonged' is a relative term depending on the gun. But in some cases the time needed to make the gun inoperable is pretty damn short.

[Langy]

Mostly. Many designs do actually use electrical energy to heat the gases to counter the temperature and pressure drop as they expand. This *does* require a much bigger electrical energy source than a battery and is where the "electrothermal" part of the name probably came from.

The ones you're talking about here are probably ETK weapons rather than just ETC, as that sounds exactly like the differences between the two.