The horrid power of the las-pistol

[Connor MacLeod]

I really probably should have held this back for "Eye of Terror" when I wanted to cover it, but I'm bored, so here it is.


Eye of Terror, ,page 116

Calliden came out of his mad, erotic trance. He plunged his hand inside his black tunic, noticing for the first time that it was wet through. Out came the laspistol. Calliden was unused to wielding weapons. It took him a moment or two to wrap his fist around the handgrip, release the safety, aim, and press the firing stud.

Steam bubbled all along the length of the laser beam as it hissed through the water. But it failed to reach Aegelica. Instead, it struck a fish, nearly a yard long, which at that moment had glided between them. The fish exploded as the water in its body turned to steam. Fragments of flesh, skin, and bone drifted to the sea bed.

The Las-pistol. The ultimate fishing device, so long as you don't want to actually eat it.

I'll probably calc it later. For now just enjoy the sheer firepower implied and how manyn people will deny it.

[Ford Prefect]

Hahahahahahaha, oh wow. You were right when you said this was a nutty scene. Sweet Emperor!

[Shroom Man 777]

Being a big fish (how big is a yard?), it must've looked really dumb too.

[Black Admiral]

(how big is a yard?)

A yard's about 0.9 meters, or three feet.

[Ford Prefect]

Being a big fish (how big is a yard?), it must've looked really dumb too.

A yard is three feet, or very nearly a metre. That's not actually big in terms of fish - the Pacific Bluefin Tuna can get to be about three metres long, great white sharks can reach four metres and the whale shark is enormous. This fish that got exploded is roughly the same length as a blackfin tuna, and could mass as much (around 20kgs).

[Zor]

One yard seems to be in the area of a resonably large freshwater fish, such as many species of trout in the 10-20 kilogram range.

However what is more important is this, was the distance that said laser beam had to go underwater to impact said fish? The water would ablate the hell out of the beem and the moving surfaces of the steam bubbles of the water it just boiled would quickly disrupt said beam

Zor

[fusion]

God! Notice the huge amount of energy released by the water and still nearly vaporize the fish and this is only pistol!!!!!!!!!!!!!!!!!

Holy Crap!!!!!!!!!!!!!
So, isn't a mutli-las cannon in the high multi gigajoules because this pistol is in the high megajoules/ low gigajoules....

[Feil]

However what is more important is this, was the distance that said laser beam had to go underwater to impact said fish? The water would ablate the hell out of the beem and the moving surfaces of the steam bubbles of the water it just boiled would quickly disrupt said beam

Indeed. Blowing up a fish is well within the known capability of a lasgun - it would only take a few hundred kilojoules to make quite a mess, though the explosion in the text looks to be in the megajoule range. It's the underwater usage that's interesting.

[Dark Hellion]

Given that a lasgun with a bayonet attached seems to be 40k's version of the swiss army knife (you know, explode head, explode torso, explode fish settings), the underwater usage ability of las-weapons doesn't surprise me.

What I really want to see is a bunch of Catachans on their day off fishing with lasguns and demo-charges. Catachan fishing adventure... that book would definitely rock.

[Falkenhayn]

Bah. Eisenhorn vs Cyberwitch I say! Eisenhorn vs Cyberwitch!

[Ford Prefect]

Bah. Eisenhorn vs Cyberwitch I say! Eisenhorn vs Cyberwitch!

Nooo, not that! That one was almost equally as insane!

[Zor]

Given that a lasgun with a bayonet attached seems to be 40k's version of the swiss army knife (you know, explode head, explode torso, explode fish settings), the underwater usage ability of las-weapons doesn't surprise me.

Lasers are very bad weapons for use underwater. The water would quickly ablate and disrupt beams of low power and beams powerful enough to burn though resonable distances are going to hit you with a nasty pulse of boiling water/steam that would boil you to death. Shooting underwater would require some sort of Supercaviational bullet, which i am sure the Imperium could produce.

Zor

[ThatGuyFromThatPlace]

there are plenty of real life under water bullets. event he chinese have an underwater assault rifle.

[Lord of the Abyss]

Shooting underwater would require some sort of Supercaviational bullet, which i am sure the Imperium could produce.

Besides what ThatGuyFromThatPlace said, another solution would be something like the old Gyrojet rocket pistols. A rapid fire and explosive version, since this is 40k.

[Ford Prefect]

Besides what ThatGuyFromThatPlace said, another solution would be something like the old Gyrojet rocket pistols. A rapid fire and explosive version, since this is 40k.

How about boltguns, which are full automatic and explosive?

[Connor MacLeod]

oops forgot this one....

Ok some trusty links from my favorite sites:

link 1


link 2


Given above (the second link you have to do a bit of digging I think, but the info is there) you can safely assume a yard logn fish generally ought to weigh at least a couple kilos, possibly as much as 10+ kilos.

This means that the laspistol generally encompasses at least single or double digit MJ (5-20 MJ, depending on variables.)

[Surlethe]

The specific heat of water is 4.186 J/g*C. If the laser beam shot through 20 m of water and vaporized a 1 cm radius tube through the water, and the temperature of the water started at about 20 C, it would have exuded some 2.1 kJ, and must generate power at at least 2.1 kW. This is an absolute lower limit, does not take into account possibly colder seas, the ablation and bubbling Zor pointed out, or greater distances.

Blowing up a 1 m fish by roasting it and flashing all of its internal water to steam will require MJ of energy. If it's 10 kg for a lower limit and is composed of 90% water, raising the energy of those 9 kg of water from, say, 20 C to 100 C requires no less than 3 MJ.

[Connor MacLeod]

However what is more important is this, was the distance that said laser beam had to go underwater to impact said fish? The water would ablate the hell out of the beem and the moving surfaces of the steam bubbles of the water it just boiled would quickly disrupt said beam

Indeed. Blowing up a fish is well within the known capability of a lasgun - it would only take a few hundred kilojoules to make quite a mess, though the explosion in the text looks to be in the megajoule range. It's the underwater usage that's interesting.

Forgot this reply: Could you mind explaining how you came up with that figure or what you base it on

In any case, there is one key detail to note about the incident - no blood whatsoever in the water. If you blow something up messily underwater with, say, ,a bolter, more often than not you'll splatter blood and other bodily fluids about rather messiyl as well as bits of bone or flesh, and that blood/other fluids would fog the water in a noticable fashion.

This leads to two possibilities:

1.) either a substantial portion of the fish's bodily fluids were vaporized

2.) the fish suffered some fairly hefty cauterization during the process of being blown apart.

Given the energies/temperatures I have noted previously as neccesary for cauterization, the energy result will not alter the results dramatically - you're still basically going to be looking at it being a multi-megajoule event even BEFORE

On the other hand, there's also those idiots who like to slavishly and literally interpret 40K in order to reinforcec their own prejudicees (you know, the "bayonet toting fanatics using napoleonic tactics without sophisticated gear backing them up.") and in that context the literal interpretation of the quote DOES indicate total/near total vaporization. (This "literal" interpretation is probably more plaubile than most of the anti-40K BS anyhow.)

And that doesn't even address the "vaporizing the water" bit..

[Connor MacLeod]

The specific heat of water is 4.186 J/g*C. If the laser beam shot through 20 m of water and vaporized a 1 cm radius tube through the water, and the temperature of the water started at about 20 C, it would have exuded some 2.1 kJ, and must generate power at at least 2.1 kW. This is an absolute lower limit, does not take into account possibly colder seas, the ablation and bubbling Zor pointed out, or greater distances.

Blowing up a 1 m fish by roasting it and flashing all of its internal water to steam will require MJ of energy. If it's 10 kg for a lower limit and is composed of 90% water, raising the energy of those 9 kg of water from, say, 20 C to 100 C requires no less than 3 MJ.

A few points: you seem to only be addressing temp/specific heat, but not boiling point, much less the heat of vaporization - your "absolute lower limit" can be MUCH higher (300-400 kilojoules per kg for boiling, roughly.)

The Diameter of the beam is likely to be a few centimeters, judging by the "thickness" of beams stated in the Gaunt's Ghosts Omnibus (the founding) as well as the ability for beams to slicec through gun straps and other examples (Ghostmaker.)

As for distance? no clue. One owuld infer at least a few meters, given that the guy opted for firing his gun rather than reaching forward if he'd been close enough to do so. The fact the fish was able to move into the path of the beam before being hit would imply a fairly significant distance as well.

Given a 2 cm diamter beam and a distance of about 2-3 meters (about one-two body lengths away, outside possible hand to hand/melee range) yields approximatley between .63 and .95 kg of water affected. If it were merely raised to the boiling point, (assume 10C water) the output would be between 240-360 kilojoules. If it was vaporization, the output would increase by a further 1.42 to 2.14 megajoules.

[Connor MacLeod]

Here's another one. Haven't actually started reading the Kal Jerico novels yet, but the implications are amusing/useful.

Kal pulled out his sword, but Ramone was quicker. He whipped a laspistol from his jacket and fired at Kal's head.

This is here mainly to establish the type of weapon being mentione din the following passage - a laspistol.

"Pull him to his knees," roared Ramone. "I want him to kneel before his better before I incinerate that little brain of his."

As I've mentioned before regarding las-weapons (a similar passage was mentioned in the Gaunt's Ghosts short story included in The Founding Omnibus. Lasweapons are also mentioned as firing "incinerating" beams in the second Shira Calpurnia novel.), a human brain can weigh roughly between 1.3-1.5 kilograms. Incinerating it can require at least 3-4 megajoules of energy (assuming 1000K cremation temperature, and 3.5 kJ*kg/k specific heat for human flesh, ,as establisehd in prior threads of mine.)

Inefficiencies can dictate an even higher number: it typically requires around 1 million (or more BTU to cremate a human body (150 lb) The human brain is about 1/50th that mass, so it would take about 20,000 BTU (~21 MJ) to cremate the brain, potentially. Thus one could infer that the conservative figure above might be seveal times greater, easily.