Heat and Pew-Pew

[Alrik Vas]

I've recently read that lasers don't heat the air around them as they fire, that they heat up what they strike and only then.

But I've also read that lasers are subject to weather (mist in particular).

My question is, if you shot a laser in rifts (with several megajoules of power, more heat transfer than a bolt of lightning, etc) into a sand storm, would it melt the sand, cutting to target, or would the sand essentially suppress the beam?

[Killer Cyborg]

I've recently read that lasers don't heat the air around them as they fire, that they heat up what they strike and only then.

But I've also read that lasers are subject to weather (mist in particular).

My question is, if you shot a laser in rifts (with several megajoules of power, more heat transfer than a bolt of lightning, etc) into a sand storm, would it melt the sand, cutting to target, or would the sand essentially suppress the beam?

Yes.
It would probably work like this:

Mutants in Orbit 84

Sand-Caster
Sand casters throw a field of ordinary sand, or highly reflective, fine grains of matter into space in a sphere 660' across. Its primary effect is to scatter laser beams, reducing the laser damage by one third.

[kaid]

Sand/chaff if its dense enough/ very dense smoke/fog/mist could impact lasers effectiveness. That said MDC capable lasers are really high powered so it would take a lot to blunt them enough to impact to much. Just look at normal laser weapons still do good damage even underwater although the blue green ones are best.

One thing about heating from lasers is that yes this does happen but lasers are very cohesive so the area they impact with heating is still a much smaller foot print than one would expect.

[J_cobbers]

Disclaimer, I am not a scientist, and my experience with lasers amounts to laser pointers and IR lasers detectable by night vision mounted on an M16 in basic training for night fire exercise.

I would likely guess both would occur, the sand would be melted or vaporized like any other solid object as the beam travels diminishing its power, but not enough to prevent it from reaching its target and doing some damage. If you have ever been in a dust or sand storm, there is a lot of variability in the intensity. I've seen a few in Kuwait, and they are not fun, but visibility is not totally destroyed. I would guess that the material being shot through would matter a lot as well as the wavelength and intensity of the laser as to how much of it gets scattered and broken up by the intervening material be it sand and dust of water vapor like mist and clouds.

For an in game context, we have very high power short duration lasers the are focused in a particular way so as to limit their range. Sand/dust are SDC materials, so would be rapidly super heated and either melted or vaporized by the beam, detracting from the intensity. The denser the storm, the more material that would effect the beam, the less damage it would do. Kind of like the rules for firing normal MD lasers under water. Perhaps you reduce the MD dealt or the effective range by a few hundred feet? I think those would be reasonable house rules. Or just apply what Killer Cyborg quoted from Mutants in Orbit.

[drewkitty ~..~]

KC did state one of the two non-force field & non-shield canon texts that cover defenses vs lasers. The other being in AUGG and it basically reads the same.

Yes, Low powered lasers do not significantly heat up the gasses in the air. This is true for even MD lasers according to the books. But the energy transfer is a % so it will always heat the air to some extent.
(Maybe the super IR from JU could detect the temp difference…maybe. Gm's would have to decide for themselves.)

However, once you put something into the air the laser has something to hit and heat up. So firing a laser through a fog bank will leave a "Tunnel" in the fog from the laser boiling off or atomize the water droplets that were suspended in the air. (About ½ cup of liquid per mile of fog bank…*drags up something I heard somewhere that might be wrong in the particulars but correct in the concept of 'there is not much water in the fog bank')

Very high powered lasers will heat up the air…the visible effects will be the boiling off any sort of clouds.
Find a video on an atomic bomb test and look at how the clouds are burned off. That will give you a idea of what happens when large scale Ship grade lasers are fired in an atmo. Which smallarms lasers will produce at a vastly smaller scale.

[flatline]

In my setting, you can buy aerosol grenades/sprays/etc that make the air semi-opaque to select frequencies (reduce damage to 10% for game purposes). Most military vehicles have these dispensers by default and they are simple to add to civilian vehicles as an after-market accessory.

Naturally, this makes non-variable frequency lasers a "poor man's" weapon.

--flatline

[taalismn]

Not to mention that if your shooter goes dumbass and holds the trigger down for sustained burn on the target, the scattering might paint the laser beam path and give your target(or more likely their companions) a general idea where the shooter is.

[dragonfett]

In my setting, you can buy aerosol grenades/sprays/etc that make the air semi-opaque to select frequencies (reduce damage to 10% for game purposes). Most military vehicles have these dispensers by default and they are simple to add to civilian vehicles as an after-market accessory.

Naturally, this makes non-variable frequency lasers a "poor man's" weapon.

--flatline

What about the spell Create Fog? Does it have any impact in your games (aside from obscuring vision)?

[kaid]

In my setting, you can buy aerosol grenades/sprays/etc that make the air semi-opaque to select frequencies (reduce damage to 10% for game purposes). Most military vehicles have these dispensers by default and they are simple to add to civilian vehicles as an after-market accessory.

Naturally, this makes non-variable frequency lasers a "poor man's" weapon.

--flatline

What about the spell Create Fog? Does it have any impact in your games (aside from obscuring vision)?

I don't believe so just penalties to hit from what I recall.

[dragonfett]

In my setting, you can buy aerosol grenades/sprays/etc that make the air semi-opaque to select frequencies (reduce damage to 10% for game purposes). Most military vehicles have these dispensers by default and they are simple to add to civilian vehicles as an after-market accessory.

Naturally, this makes non-variable frequency lasers a "poor man's" weapon.

--flatline

What about the spell Create Fog? Does it have any impact in your games (aside from obscuring vision)?

I don't believe so just penalties to hit from what I recall.

Rules as written, yes. However I was asking flatline about a specific house rule that he uses.

[flatline]

In my setting, you can buy aerosol grenades/sprays/etc that make the air semi-opaque to select frequencies (reduce damage to 10% for game purposes). Most military vehicles have these dispensers by default and they are simple to add to civilian vehicles as an after-market accessory.

Naturally, this makes non-variable frequency lasers a "poor man's" weapon.

--flatline

What about the spell Create Fog? Does it have any impact in your games (aside from obscuring vision)?

It's never come up. If fog blocks visible light and the laser is in the visible spectrum, then fog would partially block the laser (the laser would expend some of its energy "burning" through the fog...that is converting "foglets" to steam). I'd have to think about higher frequency lasers. The beam would disperse because of refraction through the "foglets", but I don't know how big that effect would be over short distances...probably not enough to matter in game terms.

Let me give it some thought.

--flatline

[Alrik Vas]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

[flatline]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

I'm not certain I understand your question.

Lasers anywhere on the spectrum, visible or not, can be damaging as long as they transfer energy fast enough to a small enough area of the target.

However, since the atmosphere is not transparent to all frequencies, you want your laser to use a frequency that won't be absorbed by the air before it reaches your target. If there's water droplets suspended in the air, some frequencies will lose more energy to the water than others, but a high enough power laser will vaporize the water faster than the droplets can be replaced by air currents. Probably not enough energy to matter in game terms.

--flatline

[Natasha]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

I'm not certain I understand your question.

Lasers anywhere on the spectrum, visible or not, can be damaging as long as they transfer energy fast enough to a small enough area of the target.

However, since the atmosphere is not transparent to all frequencies, you want your laser to use a frequency that won't be absorbed by the air before it reaches your target. If there's water droplets suspended in the air, some frequencies will lose more energy to the water than others, but a high enough power laser will vaporize the water faster than the droplets can be replaced by air currents. Probably not enough energy to matter in game terms.

--flatline

It takes a fair bit of calculus to show it but an amazing result is that 10 kilojoules is enough energy to destroy just about anything.

You're correct, but it's not correct to generalise the atmosphere to the planet's surface because the atmosphere is stratified; X-ray machines have been around for over a hundred years, after all. The obstacle to developing lasers any more energetic than visible light is the difficulty in gaining photon population inversion.

[Alrik Vas]

Ok, I get you guys. Thanks for the responses.

[guardiandashi]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

this is one that if you have or can find a copy of GURPS Vehicles there is a section on Lasers and "building/designing" weapons.

it has: lasers, UV lasers, xray lasers, grasers (Gamma ray lasers) etc.

under the gurps ruleset lasers are impaling weapons which means that armor gets a devisor for stopping them, but they also do reduced damage once they penetrate the armor.
standard lasers in that game are a X3 modifier but some of the more advanced ones are x5 or x10

[Natasha]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

this is one that if you have or can find a copy of GURPS Vehicles there is a section on Lasers and "building/designing" weapons.

it has: lasers, UV lasers, xray lasers, grasers (Gamma ray lasers) etc.

under the gurps ruleset lasers are impaling weapons which means that armor gets a devisor for stopping them, but they also do reduced damage once they penetrate the armor.
standard lasers in that game are a X3 modifier but some of the more advanced ones are x5 or x10

I don't have GURPS and I certainly don't want to derail this topic but impalement doesn't make sense for lasers.

[flatline]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

this is one that if you have or can find a copy of GURPS Vehicles there is a section on Lasers and "building/designing" weapons.

it has: lasers, UV lasers, xray lasers, grasers (Gamma ray lasers) etc.

under the gurps ruleset lasers are impaling weapons which means that armor gets a devisor for stopping them, but they also do reduced damage once they penetrate the armor.
standard lasers in that game are a X3 modifier but some of the more advanced ones are x5 or x10

I don't have GURPS and I certainly don't want to derail this topic but impalement doesn't make sense for lasers.

If my memory serves, in GURPS, impalement simply means more likely to penetrate armor but does less damage once it gets through. But it's been years since I've looked at GURPS so perhaps I'm remembering incorrectly.

--flatline

[guardiandashi]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

this is one that if you have or can find a copy of GURPS Vehicles there is a section on Lasers and "building/designing" weapons.

it has: lasers, UV lasers, xray lasers, grasers (Gamma ray lasers) etc.

under the gurps ruleset lasers are impaling weapons which means that armor gets a devisor for stopping them, but they also do reduced damage once they penetrate the armor.
standard lasers in that game are a X3 modifier but some of the more advanced ones are x5 or x10

I don't have GURPS and I certainly don't want to derail this topic but impalement doesn't make sense for lasers.

If my memory serves, in GURPS, impalement simply means more likely to penetrate armor but does less damage once it gets through. But it's been years since I've looked at GURPS so perhaps I'm remembering incorrectly.

--flatline

more or less...
in that game in general there is: slashing crushing and impaling damage, I believe there are additional more exotic types such as fire, acid, and sonic damage but those are more special case.

obviously slashing (cutting) damage is pretty common among many weapons, and a lot of armor specifically defends well against it.
crushing (blunt) damage is also very common although the defenses are a little less common.

Impaling damage is actually fairly rare and very few armors specifically counter it, and in many ways lasers are the definition of impaling damage, in that they tend to directly affect small areas of armor and attempt to burn through leaving the rest of the armor untouched. much like a rapier, stiletto, or pick does.

[Natasha]

What if the laser isn't on a visible spectrum? Are they not damaging lasers? No idea, actually curious.

this is one that if you have or can find a copy of GURPS Vehicles there is a section on Lasers and "building/designing" weapons.

it has: lasers, UV lasers, xray lasers, grasers (Gamma ray lasers) etc.

under the gurps ruleset lasers are impaling weapons which means that armor gets a devisor for stopping them, but they also do reduced damage once they penetrate the armor.
standard lasers in that game are a X3 modifier but some of the more advanced ones are x5 or x10

I don't have GURPS and I certainly don't want to derail this topic but impalement doesn't make sense for lasers.

If my memory serves, in GURPS, impalement simply means more likely to penetrate armor but does less damage once it gets through. But it's been years since I've looked at GURPS so perhaps I'm remembering incorrectly.

--flatline

more or less...
in that game in general there is: slashing crushing and impaling damage, I believe there are additional more exotic types such as fire, acid, and sonic damage but those are more special case.

obviously slashing (cutting) damage is pretty common among many weapons, and a lot of armor specifically defends well against it.
crushing (blunt) damage is also very common although the defenses are a little less common.

Impaling damage is actually fairly rare and very few armors specifically counter it, and in many ways lasers are the definition of impaling damage, in that they tend to directly affect small areas of armor and attempt to burn through leaving the rest of the armor untouched. much like a rapier, stiletto, or pick does.

Thanks! I see the reasoning although completely disagree because a laser does not impale, it ablates. I also understand the need to balance level of detail and play-ability.

[SpiritInterface]

Now we are talking old school Sci/Fi RPG tech. Sandcasters and anti-laser aerosol grenades straight out of Traveler.

The anti-laser aerosol grenades had mylar bits in the fog to defuse the beams.