Questions about UT smoke, lasers, and plasma.

[Anthony]

Originally Posted by sethbrayman

I would like for the laser to follow the rules that other lasers in UT do and simply be effected by smoke depending on the type of laser and type of smoke. My argument is that, based off of the description of plasma weapons, they would do exactly what you describe and in fact "explode at whatever depth the laser's penetration of the cloud fails".

The problem is that this range is actually equal to the weapon's listed range. The amount of energy required to create an evacuated channel through smoke is not appreciably higher than the amount required to create an evacuated channel through clear air.

[sethbrayman]

Originally Posted by Fred Brackin

More than superscience what you have here is two flavors of _bad_ science and predictably enough trying to referee between them with good scicne doesn't work very well.

First, the game rules about weapons grade lasers being stopped by smoke are bad science. They have a single hex of smoke that blocks normal vision (-10 penalty) giving DR 10 and basically stopping a 3D laser.

Somebody can come along and work out the equivalency of normal lighting to watts of laser output if they want to bt why don't we stick to comparing lasers to lasers and say that a smoke hex that stops normal vision will also stop a common laser pointer.

Said laser pointer is limited to 5 milli-watts by US law. A modest real world laser such as the US Navy has just deployed will be in the vicinity of 100 kilowatts. Just to put everything in the same units 100 kw is equal to 100,000,000 milli-watts.

From this we can see that the weapon laser is 20,000,000 times as intense as the laser pointer. It would take 20 million times as many smoke particles to absorb the weapons laser. Fairly predictable when Gurps would normally measure the penetration of the weapons laser in millimeters of RHA steel (and get a value of about 3.5mm of RHA).

Incidentally, this is a real world laser. By the standards of sci-fi laser it would be only a pistol and possibly a small one at that.

So single hexes of regular smoke would have no measurable effect on a weapons grade laser. Bad science.

As you've asked a laser that would heat a horizontal column of air so much that it would expand enough to create a channel of near vacuum and hold it open would indeed have to be even stronger than a simple weapon laser.

This is good stuff! Can't use real world and GURPS rules together. So, would it be appropriate to say that in the GURPS UT world (GURPS rules not real world rules), without changing any other rules about smoke or lasers, and without altering the description of how a plasma weapon works, I can conclude that sufficient smoke would indeed stop the laser, thereby causing a premature explosion of the plasma bolt?

[sethbrayman]

Originally Posted by Anthony

The problem is that this range is actually equal to the weapon's listed range. The amount of energy required to create an evacuated channel through smoke is not appreciably higher than the amount required to create an evacuated channel through clear air.

How can this be reconciled with the rules in UT that give DR vs lasers to smoke? It seem like smoke does specifically create an appreciably higher energy cost to penetrate it compared to air, per UT rules.

[Ulzgoroth]

Originally Posted by sethbrayman

How can this be reconciled with the rules in UT that give DR vs lasers to smoke? It seem like smoke does specifically create an appreciably higher energy cost to penetrate it compared to air, per UT rules.

That's for lasers that are trying to pass through the air. Smoke gets in the way of that.

This laser is not trying to pass through the air. It is trying to get absorbed by the air until the air blows away and isn't there to absorb it anymore. And adding smoke doesn't really do anything to stop the air from blowing away.

[sethbrayman]

Originally Posted by Ulzgoroth

That's for lasers that are trying to pass through the air. Smoke gets in the way of that.

This laser is not trying to pass through the air. It is trying to get absorbed by the air until the air blows away and isn't there to absorb it anymore. And adding smoke doesn't really do anything to stop the air from blowing away.

I definitely understand what you are saying, but I don't know how its possible to achieve that effect within whats described in the UT rules...

When a laser tries to pass through air, but instead hits smoke, and is unable to penetrate that smokes DR, where is that energy going? Either its easy to penetrate the smoke once an interaction is happening i.e. "the air blows away" or the smoke becomes and obstacle i.e. DR.

Maybe I'm just not getting it, but I can not see how these things are anything but mutually exclusive. A laser either can cut through smoke, making smoke DR no longer a rule, or it can't cut through (sufficient) smoke, thus stopping the plasma bolt that follows. If it ignores the smoke completely (like x-ray lasers) then the plasma bolt that follows will hit the smoke and explode.

[Anthony]

Originally Posted by sethbrayman

When a laser tries to pass through air, but instead hits smoke, and is unable to penetrate that smokes DR, where is that energy going?

Mostly, it's going into the air, heating it up so you get a beam path. Basically, a laser intended to create an evacuated path treats clear air as smoky, and thus suffers no additional penalty from smoke.

It is important to remember that the base mechanics behind plasma guns are physical nonsense; if you've got a laser sufficient to create a path the plasma can shoot through, you just kill people with the laser and ignore the plasma part.

[Anaraxes]

The key word was "sufficient".

In this particular application, air is _not_ transparent to the laser. The weapon designers don't want it to be. Air absorbs laser energy and gets blown out of the way to create that evacuated channel for the plasma. Smoke is no different in this regard. If it's better than air at absorbing laser light, it's that much easier to blow it out of the way.

The limit comes in the energy of the laser. The weapon puts out enough laser energy to clear a cylinder of air between the muzzle and the target. It has a certain effective range, which is to say a volume of air that the guide laser is designed to clear. Smoke particles might need a different amount of energy to clear*. So, it seems a reasonable effect of smoke is to reduce effective range of the weapon. "Sufficient" smoke to reduce the range to the point where the laser can no longer clear a path to the target would have the effect of blocking the shot. Lesser amounts of smoke get cleared out of the way and don't affect the plasma that follows the laser, and so aren't an effective defense. The plasma still has a path to follow and still has its normal effect on the target.

So you'd really want a factor that says 1 meter of smoke counts as X meters of air, subtracting X from the range of the weapon. A given depth of smoke might help at long ranges, while the same amount of smoke is ineffective at short ones.

This is different from the effect on a laser weapon, where the laser itself carries the energy that damages the target, and which frequency is intended to be transparent as possible to air. In that case, any joule you dissipate from the laser is one less joule to damage the target. For laser weapons, it seems reasonable to model smoke as DR. A little smoke saves you some damage; a little more saves you yet more. DR more than the max weapon damage means you're safe.

Returning to the plasma weapon, note that if smoke does reduce the range so that it doesn't reach the target, that doesn't mean the plasma stays in the weapon. It will still follow the evacuated channel as far as that goes; the energy then gets dumped into whatever happens to be where the plasma "runs out of track". So, if your smoke is right next to you, it might not be that useful. Having a plasma / air / smoke explosion two centimeters in front of your face is perhaps better than letting that plasma hit your face, but it's not negligible. To model a smoke defense that's something like a laser detector wired to a dispenser that blows out a cloud of smoke when touched by a laser, you might want to apply the near-miss by explosions rule, and have the smoke turn contact hits into non-contact blast damage. You'd rather have that smoke in a screen some distance away from you; or, if the setting has battlesuited troopers, the splash damage might be minor enough that they just let their armor take it.

--
* The actual amount would depend on the particle composition, mass, density in the volume, and so on; we're already well into technobabble just to have the weapon in the first place, so I don't know if you really want to model things in that much detail.

[sethbrayman]

Originally Posted by Anthony

Mostly, it's going into the air, heating it up so you get a beam path. Basically, a laser intended to create an evacuated path treats clear air as smoky, and thus suffers no additional penalty from smoke.

It is important to remember that the base mechanics behind plasma guns are physical nonsense; if you've got a laser sufficient to create a path the plasma can shoot through, you just kill people with the laser and ignore the plasma part.

That's a very good point. You would just use this super laser instead. I'm looking for internal consistency and that fact does make it difficult to find.

[sethbrayman]

Originally Posted by Anaraxes

The key word was "sufficient".

In this particular application, air is _not_ transparent to the laser. The weapon designers don't want it to be. Air absorbs laser energy and gets blown out of the way to create that evacuated channel for the plasma. Smoke is no different in this regard. If it's better than air at absorbing laser light, it's that much easier to blow it out of the way.

The limit comes in the energy of the laser. The weapon puts out enough laser energy to clear a cylinder of air between the muzzle and the target. It has a certain effective range, which is to say a volume of air that the guide laser is designed to clear. Smoke particles might need a different amount of energy to clear*. So, it seems a reasonable effect of smoke is to reduce effective range of the weapon. "Sufficient" smoke to reduce the range to the point where the laser can no longer clear a path to the target would have the effect of blocking the shot. Lesser amounts of smoke get cleared out of the way and don't affect the plasma that follows the laser, and so aren't an effective defense. The plasma still has a path to follow and still has its normal effect on the target.

So you'd really want a factor that says 1 meter of smoke counts as X meters of air, subtracting X from the range of the weapon. A given depth of smoke might help at long ranges, while the same amount of smoke is ineffective at short ones.

This is different from the effect on a laser weapon, where the laser itself carries the energy that damages the target, and which frequency is intended to be transparent as possible to air. In that case, any joule you dissipate from the laser is one less joule to damage the target. For laser weapons, it seems reasonable to model smoke as DR. A little smoke saves you some damage; a little more saves you yet more. DR more than the max weapon damage means you're safe.

Returning to the plasma weapon, note that if smoke does reduce the range so that it doesn't reach the target, that doesn't mean the plasma stays in the weapon. It will still follow the evacuated channel as far as that goes; the energy then gets dumped into whatever happens to be where the plasma "runs out of track". So, if your smoke is right next to you, it might not be that useful. Having a plasma / air / smoke explosion two centimeters in front of your face is perhaps better than letting that plasma hit your face, but it's not negligible. To model a smoke defense that's something like a laser detector wired to a dispenser that blows out a cloud of smoke when touched by a laser, you might want to apply the near-miss by explosions rule, and have the smoke turn contact hits into non-contact blast damage. You'd rather have that smoke in a screen some distance away from you; or, if the setting has battlesuited troopers, the splash damage might be minor enough that they just let their armor take it.

--
* The actual amount would depend on the particle composition, mass, density in the volume, and so on; we're already well into technobabble just to have the weapon in the first place, so I don't know if you really want to model things in that much detail.

Thank you that's very helpful and along the lines of what I was trying to figure out.

[Ulzgoroth]

Originally Posted by sethbrayman

I definitely understand what you are saying, but I don't know how its possible to achieve that effect within whats described in the UT rules...

When a laser tries to pass through air, but instead hits smoke, and is unable to penetrate that smokes DR, where is that energy going? Either its easy to penetrate the smoke once an interaction is happening i.e. "the air blows away" or the smoke becomes and obstacle i.e. DR.

Maybe I'm just not getting it, but I can not see how these things are anything but mutually exclusive. A laser either can cut through smoke, making smoke DR no longer a rule, or it can't cut through (sufficient) smoke, thus stopping the plasma bolt that follows. If it ignores the smoke completely (like x-ray lasers) then the plasma bolt that follows will hit the smoke and explode.

The answer is that the smoke doesn't change anything. To the evacuation laser, all air is opaque whether or not there is smoke in it.