40K lasgun analysis methodology thread

[Connor MacLeod]

Since I began my little 40K analysis gig, I've found that lasguns are the hardest weapon to calc. I didnt think that way initially. I saw the word "vaporise" in the 3rd edition core rules and just
assumed they did local vaporisation (part of me still does.), but I admit that was a certain bit of naivete on my parrt. Its way more complex than that. Other 40K weapons are fairly straightforward - plasma guns vaporize and/or cremate, meltaguns melt/vaporize, and even bolters and ballistic weapons are more easily calced (projectile weights and recoil are good indicators.) Hell, even hellguns have been easier to calc.

Part of the reason is that they have multiple damage mechanisms: They have both heat and blast/shockwave effects (thermal and mechanical damage), and as described on the quite useful atomic rockets site, the mechanical damage effects can do alot of damage for very little energy. But lasguns also cause extensive cauterization and charring/burning, so the thermal effect must also be considered (and is in fact the most reliable mechanism I've found for calcing them.) Problem is, its been a bitch to figure out the exact temperatures one can associate with cauterization. Its not as if laser guns exist in this form, after all.

First, an overview of how they are desribed to work in the various sources. A lasgun fires a beam or bolt of massless energy (although there is some question to this, since some sources describe them as more "bullet" like, and others describe them as radiating heat or possessing kinetic force: it may be some are more akin to particle beams or a hybrid weapon.) The focused beam of energy strikes the target. The energy is delivered in a highly concentrated form, very rapidly, vaporizing the object (be it organic or inorganic) at the point of contact. This sudden, violent vaporization - a steam explosion, really - transmits thermal and blast ("kinetic", "concussive" or "mechanical" - terms I've seen to describe it, but for all intents and purposes it refers to the same effect.) effects into the target's surrounding matter (like with the asteroid vaporized in TESB.) In organic tissue, it is the water content of the body that is rapidly vaporized, causing the explosive shocks that propogate through the body, causing mechanical damage as described on atomic rockets source here

Whether you use lasers or particle beams, you'll need a bit over a kilojoule of output energy to reliably incapacitate a human target. In the case of a laser weapon, that energy would be subdivided into ~1 joule pulses at ~5 microsecond intervals, to achieve penetration in the face of a laser's natural tendency to deposit energy at the target's surface. Particle beams don't have that problem; boost the electrons up to a few hundred MeV, and you can dump the whole kilojoule's worth at once.

The plasma clears away easily in that time frame; debris is the real issue, and the driving force between the 5 microsecond pulse rate. That allows roughly 90% of the debris to clear the beam path, assuming a 1mm beam and instantaneous 1J pulses. 1 joule every 5 microseconds is optimal against soft tissue, other materials will want different pulse trains

Note that as I mentioned, though, this method allows for little or no cauterization:

I assume that since the beam is one millimeter in diameter but the hole in the pirate is four centimeters, little or no wound cauterization will occur.

Nope, the wound would be ragged and messy. It is created by mechanical, not thermal effects.

Additionally, the shockwave can induce heating in the surrounding tissue, resulting in cauterization and severe burning. It is worth noting that while this is probably considered to be the "usual" effect, it is by no means the sole mode of operation. Lasguns can and have operated in sustained mode, inflicting piercing or cutting effects, as well as purely thermal damage with minimal to no concussive effects. It is also worth noting that because of inefficiencies as well as the mechanical damage aspect, bleeding can still occur despite cauterization. The wound will just bleed much less in most cases. (one of the major purposes of Flak armor, in fact, is probably to minimize the concussive/shock effects as much as the thermal, since if the wound cauterizes it won't bleed, and suppressing the blast will remove the secondary bleeding.)

As I mentioned, its hard to attach a temperature to cauterization. Specific heat is easy: water is 4185 J/kg*K, and flesh (easily googled) is 3500 J/kg*K - not dramatically different from one another. Melting point and boiling point aren't really relevant in this case, because the human body is 70% water for the most part (blood is higher at 83%, muscle and other tissue is around 75%, and bone is only 22%, but bones make up only 20% of the overall body mass, and blood less, but it works out to roughly 65-70% on average. Source here) Latent heat of vaporization for water is around 2.3-2.5 MJ/kg (depending on source). But we need the temperatures in order to complete the calcs (unless assuming total vaporization. That can be argued in some cases, and a fair amount of vaporisation probably does occur anyhow, but total vaporization is probably an upper limit for lasguns in general - though you could still argue that.)

The closest before now (and what I always used) was the boiling point of water. We know from Ghostmaker that water will boil when hit by a lasbeam, and we already knew from numerous sources that vaporization can occur (including hitting snow or flesh), and partial vaporization will occur with boiling. Moreover, boiling point qualifies as a 2nd or 3rd degree burn (the cloeset point that charring can occur. As far as I can tell, cauterization is commonly associated with third degree burns, especially in branding. Technically, the term is referred to as "Scalding" for boiling liquid though.) This conclusion, however, turns out to be dramatically conservative (not that that's bad..) for various reasons. First and foremost, the "scald" temperature I used assumed a one second timeframe - realistically, especially considering the "explosive" effects, the timeframe would be MUCH shorter, which ought to mean the temperature should be considerably higher. Secondly, the images I have seen for scalding do not seem to indicate any real or significant charring, at least at that temperature. Third, the boiling point assumes very little vaporization occurs, which obviously isn't really going to be the case.

So a more accurate temperature is needed. Research on medical cauterization was time consuming, but did yield some results. The problem is, just becaue a temperature is stated does not mean its applying to the tissue. The cauters themselves could be very high temperature, but the temperatures applied to tissue need not be the same (energy balances, remember. Specific heat + a given temp over a certain mass for the energy input.) However, looking into medical cauterization, I did manage to find enough on tissue temperatures.


Lotsa links will be following. Like with my last little (ha ha, "little") essay, I'll post the links, with the relevant tidbits. Bear wiht me, this will be MUCH longer...

Link 1

Adventitial tissue temperatures below 80 degrees C were not associated with appreciable welds, while equilibrium temperatures between 95 degrees C and 140 degrees C were consistently associated with effective mean weld strengths, which increased linearly from 25 to 110 g, respectively. Temperatures greater than 150 degrees C were associated with rapid tissue dehydration and charring. These data suggest that the therapeutic range of tissue temperature that provides effective thermal fusion of intima-media separations is broad and that the depth and degree of thermal coagulation can be controlled by manipulation of laser energy delivery.

Techncialyl the above refers to coagulation rather than cauterization, but the two I have noticed are sometimes used interchangably (and to mean much the same thing) In any case, as I bolded, temperatures of 150 C minimum are associated with "charring" and "dehydration" (IE damage to the tissues.) In terms of a medical surgery/cauterization, its desirable to limit termperatures to avoid this, but of course in a weapon such is not a consideration. So at a minimum, 150 C can be considered "charring/cauterization" temp.
link 2

There are several disadvantages to the conventional electrosurgical unit, which include tissue adhesion to the electrosurgical unit tip, significant charring of tissue, generation of significant quantities of smoke, and ineffective coagulation of bone and other high-impedance tissues. With argon-enhanced coagulation, the argon beam displaces oxygen and nitrogen, limiting oxidation of tissue and resulting in less combustion and therefore less carbonization (charring) of the tissue, less smoke and odor, and less tissue adhesion to the electrode tip than in standard electrosurgery. This combined with the lower power settings that can be employed with the argon gas surgical unit contributes to decreased tissue destruction and necrosis. The conduction of current by the argon beam allows for effective coagulation of even high-impedance tissues such as bone. When tissue is being cauterized with an argon gas surgical unit, the tissue temperature never exceeds 110?C because of a cooling effect from the argon gas and because no further conduction of rf energy occurs once eschar forms; in contrast, with conventional electrosurgical units, tissue temperature is approximately 270?C. This precise flow of energy allows the user to coagulate tissue in a more efficient and controlled manner.

Again, note that coagulation and cauterization is used interchangably. Also note the references to "charring" and associated thermal damage. Also notice the 110 C - 270 C temps associated with "medical" cauterization. Which, again, hints my use of "boiling point" is grossly conservative (and this is still for medical purpsoes, much less military ones.)
Note that this does refer to "electrocautery" rather than laser cautery (or laser vaporization, again the terms seem interchangable in that regard), but the effects are still thermal, so the results should be approximately accurate (especially since they dont need to be precise or controlled.)
link 3

The Indigo® laser treatment system has unique characteristics that define it as a minimally invasive thermal therapy rather than as a conventional laser therapy, even though the name suggests the latter. The temperature in the prostate during Indigo® ILC rises at a steady rate and is in line with other thermal therapies (80°C to 100°C) rather than conventional laser therapies (>300°C).

Again we have a link dealing with lasers and cautery/coagulation. note that they also use the term laser vaporization in the same arrticle, so the effects are (no surprise) much the same, given the temepratures involved. The quote above, of course, notes that the 80-100C range is considered appropriate for "medical" purposes, but "conventional" laser therapies go with 300+C temps. As I noted before, its clear that my initial beliefs were grossly underestimated.

Link 4

By modifying the waveform of this current, the physician can use it to coagulate or dehydrate the edges of the severed tissues, thereby arresting bleeding in certain surgical operations. This type of electrosurgery generates tissue temperatures of many hundred degrees Centigrade (up to 800 degrees) most RF generators in common use today are intended to achieve both RF cautery and blood coagulation.

At temps of "many hundreds of degrees", up to 800 C. This indicates nearly an order of magntidue higher temp than I assumed before (Its close to cremation level temps, I should add.)

Irreversible damage to tissue (i.e., denaturation of tissue proteins) occurs at temperatures greater than 47 degrees Centigrade.

This does indicate that at lower temps the sort of desired destruction we see can START to occur, however, as noted above, much higher temperatures have been used in surgical practices, so its not a absolute thing (indeed, if this were sufficient, they'd have no need for 100+ C temps, would they?) This could be on a highly localized, or a long term scale (alot of the surgical procedures rely on very sustained applications.. many seconds or minutes.)

Beyond that point, greater current intensities tend to heat up tissue too much, elevating tissue temperature to 100 degrees Centigrade and above and thereby causing carbonization of the tissue in the immediate vicinity of the electrode tip. This carbonization in turn increases tissue resistance to further passage of current (i.e. tissue impedance), which limits the extension of the lesion to a thin tissue shell surrounding the needle tip.

Again, as above, this tends to suggest lower temperatures can ALSO lead to damage (something I suspected and never denied, because I'm sure someone will point it out), but that its not really changing anything, and as noted, much higher temps are routinely used, (and have been), in medical procedures, so it must not be an absolute. (The fact that its referring to intneisities tends to reinforce the "localized effect" issue.) And also remember that in medicine, lower temps to achieve the results are desirable to limit damage (indeed its the higher temps that result in the damage we need.)
link 5

Electrocautery uses high temperatures (400 degrees to 600 degrees Centigrade) to remove tissue, which burns and chars surrounding tissue, and frequently leads to significant post-operative pain and long recovery periods. Coblation applies bipolar radiofrequency (bRF) energy to a conductive solution, such as saline, to create a relatively cool (40 degrees to 70 degrees Centigrade) plasma field, which virtually dissolves tonsil tissue, preserves healthy surrounding tissue and can seal any vessels that bleed.

Again note "400-600" C temps, associated with electrocautery.

Link 6

As the RF energy is applied, frictional heating of tissues results, with cell death occurring at temperatures between 60 and 1000º C.

This seems to indicate cauterization can occur at up to 1000C. Possible, but I admit that this source makes me a tad leery given some of the later statements. This is probably the least
reliable of the statements. I suspect that they may be off by an order of magnitude temp-wise on some of the temps. (So in this case 1000 C is 100 C)

The high frequency radio surgery and its results should also not be confused with diathermy, electric cauterization, or spark producer. With radiofrequency, the targeted tissue temperatures stay localized within a 60-100°C range thus limiting heat dissipation and damage to adjacent tissue. In contrast, electrocautery, diathermy, or laser temperatures are significantly higher (750-900°C) which result in a very high heat propagation, which is far in excess of the desired therapeutic need (6).

This is perhaps the MOST reliable of the temps.. note the "60-100C" is accurate, so it is likely the representation of electrocautery might be accurate. (especailly since it is indicating that Electrocautery is much higher-temp and excessive.)

he cellular water in the soft tissues gets heated and when the temperature reaches 1000C, it starts boiling and produces steam, which results in cellular molecular dissolution of individual tissue cells. The cells exposed to these waves are destroyed while the surrounding tissues remain unaffected

Sorry, but at 1000C you're way BEYOND boiling point for water (100C). You're well into cremation level temps at that point. Water would have long vaporized at the point of 1000C.
Still, it *might* be accurate, but I have my doubts.

RADIOFREQUENCY ELECTROCAUTERY OR BOVIE
Simultaneous cut and coagulation. Requires different modes and adjustments for different applications.
Minimal smoke production. Produces excessive smoke.
Minimal surrounding tissue damage. Tissue damage like 3rd degree burns.
Heats tissues below 1000 C. Raises tissue temperature above 5000C.
Sterilizes tissues under application. Can cause postoperative sepsis.
Minimal scarring creates soft supple scar. Gross scarring and fibrosis.
Faster healing. Slow healing.

Again, 1000C and 5000C are WAY too excessive for surgical temps as far as I can tell. I think what they mean is 100C and 500C, which would be more plausible given the overall context. 500C would definitely cause "third degree burns", excecssive smoke, gross scarring, and charring. Its still much higher than the boiling point temp I used before, though.

Link 7

The saline couples radiofrequency electrical
energy into tissue in which it is converted into
thermal energy. The flow of saline provides cooling to
limit peak tissue temperatures to 100°C or less (Fig 1).
This is contrary to conventional electrosurgical devices in
which tissue temperature can easily exceed 300°C, resulting
in tissue desiccation, char formation, smoke generation,
electrodes sticking to tissue, and undesired lateral
thermal damage.

Again, see that 100C is consiervative, temps in Excess of 300C are mentioned for "tissue dessication, char formation, etc."

link 8

In our experiment, once the needle
had been inserted and deployed in the liver parenchyma,
the generator was used for 15 min in the
mean-temperature-control mode with a threshold
set at 95°C.

I only mention this because it notes that long timeframes (15 minutes) in this case are associated with the lower temps (95C here) This makes sense, after all. You can reach a certain energy threhshold (ie melting something) by prolonged heating at lower levels, or a single large injection of energy, even though the two differe. (depending on the results, the latter is generally more efficient, since it gives less time for energy to radiate away. But its much less precise and more damaging to surroundings.)

Link 9

Conventional monopolar electrocautery is also associated
with much higher tissue surface temperatures than with the
Aquamantys System with temperatures reaching in excess
of 300°C. The higher temperature associated with
conventional monopolar electrocautery results in a charring
of the tissue or bone surface, smoking, and the
development of a superficial coagulated blood plug which
temporarily stops bleeding. This plug often cracks or is
dislodged resulting in intraoperative or postoperative
rebleeding from the site.

This is precisely a description of what I conclude a lasgun would do (and fits the descriptions in the novels.) "tissue surface temperatures" indicates wide-spread effects (the cauterization occurs on the edges of the wound, remember, so the average volume of the wound needs to be around 300C). Also take note of the "tissue and bone charring", and the "blood plug" that temporarily stops bleeding, but can be broken open again. Cauterization is hardly consistent or perfecT (variable outputs, body armour or lack thereof, glancing or direct hits, etc.) so some owunds could be MORE cauterized than others, or more violently broken open (by motion, jarring, the explosive kinetic effects, etc.) The only real difference is volume (its still a medical procudure we're talking about, so teh damage is much more localized. Lasguns blow out fairly sizeable wounds, relatively speaking.)

link 10

The saline used as a conductive fluid at the tip of the
BPS5.0-VT device (Figure 2) also cools the tissue surface
and prevents the surface temperature from exceeding 100°C.
The use of standard electrocautery results in the
tissue surface temperature exceeding 300°C. The use of
standard electrocautery also leads to charring of the tissue or
bone surface and scar formation.

Same site, essentially a repeat of the previous evidence phrased just a bit differently. 300 C temp vs 100C, mention of charring and scar formation along with cauterization. STill, its useful supplementary data.


link 11

"As tissue begins to heat above 60 degrees C, it begins to desiccate, blanch white and shrink as proteins denature, and flash boil at temperatures somewhere over 100 degrees Centigrade. In tissues with normal blood flow, temperatures below about 45 degrees C are non injurious. Higher temperatures cause irreversible damage, and tissue death and coagulation is time dependent to some degree. One can raise tissue temperature to a higher degree for a very short period of time with no tissue death occurring, while at the same time if one prolongs temperatures in the lower range for many seconds, then tissue death will occur. The generation of heat should occur quickly when using laser or electrosurgery to cut, so that we generally ignore this time variable."

Nothing specific on temperature, but this does reinforces the idea that lower temperatures (used in many procedures for cauterization or cutting) deliver much less energy (and lower temps) over a longer period of time (many seconds or even minutes), whereas the other "higher" temperature proceesses like laser or electrocautery (interesting inasfar as they are noted similar) are shorter-term and much higher temp.

Also of note is that there is a chart attached that indicating at 100C and above is where "vaporization and charring" occur. We can conclude that any vaporization that occur in these calcs will be factored into the overall temp (IE we don't have to really factor vaporization sepaarately)

Tomorrow or in a day or two I'll present a few examples (already mentioned in past debates) to possibly demonstrate how it works. It'll be a bit complicated, and I kinda want to get some feedback and such first.

[Shroom Man 777]

I got no idea 'bout calculations. But...aren't Hellguns just Lasguns with a bigger battery pack?

[18-Till-I-Die]

AFAIK...

Hellguns are tricked out Lasguns that fire faster, have a cooling system, and a backpack energy reserve. So yeah, it's pretty much implied everywhere i've seen the technologies are one and the same. Unless the fluff has changed recently, they're overcharged lasguns with big battery sytems.

[2000AD]

I'm not sure. Imperial Stormtroopers (around 2nd Ed.) used to use 'Hot-Shot Lasguns', lasguns that were over charged. Then in later editions they were switched to hellguns which certainly appear to be simular in everything but name.

In Xenos (Eisenhorn book 1) the term hell gun is used for the stormtrooper weapon, and in the Gaunts Ghost's series snipers use Hot shot batteries, over powered lasgun power cells like the old ones. So it would appear that they are now two seperate things

It looks to me like the Hellgun is a new las-weapon, with the power of the hotshot but without the decreased ammo capacity that hot shots have compared to regular lasguns (Lack of ammo covered in Gaunts Ghosts and Necromunda rulebook, while in Xenos when Hellguns are used there isn't mention of the limited ammo which is brought up just about whenever hot shots are mentioned)

As an extra that probably isn't worth much, in the game Dawn of War hellguns fire a continous laser beam unlike regular las guns, but game mechanics aren't used that much.

[Shroom Man 777]

DoW doesn't have hellguns fire a continuous beam. It fires in rapid pulses.

[2000AD]

DoW doesn't have hellguns fire a continuous beam. It fires in rapid pulses.

Could have sworn it looked like a continous beam. Mind you, I haven't played it in a while.

[Shroom Man 777]

Well, it's a really really rapid fire pulse. Imagine a laser pulsing with the rate of fire of, I dunno, an automatic rifle. No wonder it'd look like a continuous beam.

[Hawkwings]

Maybe you should do calcs for two types of lasguns: the laser kind and the particle kind.

[Teleros]

Hellguns are tricked out Lasguns that fire faster, have a cooling system, and a backpack energy reserve. So yeah, it's pretty much implied everywhere i've seen the technologies are one and the same. Unless the fluff has changed recently, they're overcharged lasguns with big battery sytems.

Yep - most Guardsmen use lasguns mainly because hellguns are more expensive, harder to maintain etc. In game mechanics they have the same strength (3) but ignore flak armour or worse (ie AP5 weapons), so they pack a much more impressive punch but don't seem to be that more effective against an unarmoured human. Makes me wonder if the beam tends to go through a target more easily.

[Imperial Overlord]

Yep - most Guardsmen use lasguns mainly because hellguns are more expensive, harder to maintain etc. In game mechanics they have the same strength (3) but ignore flak armour or worse (ie AP5 weapons), so they pack a much more impressive punch but don't seem to be that more effective against an unarmoured human. Makes me wonder if the beam tends to go through a target more easily.

Strength categories in tabletop are very broad category. Strength 3, for example covers primitve projectile weapons, slug throwers, lasguns, hellguns, etcetera. If they kicked hellguns up to Strength 4 they would be up there with the rpg like bolters and the flesh shredding hails from shuriken catapults and they aren't quite that nasty so they stay Strength 3.

Inquisitor stats hellguns as doing more damage than standard las weapons, but less than bolters.

[Lord Revan]

DoW doesn't have hellguns fire a continuous beam. It fires in rapid pulses.

Could have sworn it looked like a continous beam. Mind you, I haven't played it in a while.

it's like the regular las rifle shots with about 100 times faster RoF

[Connor MacLeod]

I'm not sure. Imperial Stormtroopers (around 2nd Ed.) used to use 'Hot-Shot Lasguns', lasguns that were over charged. Then in later editions they were switched to hellguns which certainly appear to be simular in everything but name.

In Xenos (Eisenhorn book 1) the term hell gun is used for the stormtrooper weapon, and in the Gaunts Ghost's series snipers use Hot shot batteries, over powered lasgun power cells like the old ones. So it would appear that they are now two seperate things.

From what I can gather, that seems to be pretty much what is the case. For the purposes of the calcs, the two tend to come out pretty close in terms of "per shot" output (hellguns are a bit mroe destructive) and they both tend to do more outright "vaporization" than lasguns do (both would vaporize a human head in a single shot, for example.) I tend to treat them as being virtually one and the same, (and also for the "vaporizing" bit, easier to calc than lasguns are.) Hellguns and such probably do quite a bit of cauterizing as well, but that wouldn't contribute a grreat deal to the overall calc compared to vaporization.

I should note though, in the Eisenhorn books hellguns were also used by Naval troops, not just storm troops (although KasrKin used lasguns, not hellguns.)

It looks to me like the Hellgun is a new las-weapon, with the power of the hotshot but without the decreased ammo capacity that hot shots have compared to regular lasguns (Lack of ammo covered in Gaunts Ghosts and Necromunda rulebook, while in Xenos when Hellguns are used there isn't mention of the limited ammo which is brought up just about whenever hot shots are mentioned)

Well in a normal lasgun a hotshot pack can damage the weapon and require replacement of components (IE the barrels in the long-las variant) due to the increased "per shot" output. I'd guess this means Hellguns are more "durable" or built to withstand the strain of the enhanced output compared to lasguns (and probably why they are rarer.)

Hellguns also seem to differ in some other ways as well. Since they are generally more "high tech", they seem to have better targeting ystems. As well, some hellguns (4th edition rules and the 2005 Wargear) note they are gyro-stabilized to improve accuracy. The barrel MAY focus teh beam more tightly (concentrating more energy on a smaller area, thus making ti better at penetrating and inflicting damage than lasguns - this might account for its Armor piercing qualities in-game as well as the higher maintenance, but I wouldn't put much faith on sheer game mechanics.)

Of course the biggest difference is that hellguns is that hellguns usually have the backpack mount (not true in all cases, sincec in the Gaunt's Ghosts novels and the Cain novels hellguns usually run on powerpacks - hotshots perhaps). Presumably this gives them a far greater ammo capacity (akint o a backpack mounted belt-fed ammo pack or some such.)

I shoudl also note there is no reason lasguns couldn't do this: In the "battlezone cityfight/Cities of Death" urban warfare supplements its mentioned that lasguns can be hooked up to power generators for a virtually indefinite power supply simialr to a hellgun.

As an extra that probably isn't worth much, in the game Dawn of War hellguns fire a continous laser beam unlike regular las guns, but game mechanics aren't used that much.

Various fluff has "continuous/cutting" settings for lasguns, most notably the early Ghosts novels. That doesn't seem contradictory per se. Depending on how you do it, even a rapidly pulsed weapon can look "sustained" as far as I recall things, nor do I see it as a problem. hell that's probably their equivalent to "full auto', really. (and its better than that painful 220 RPM from the uplifting primer..*groan*)

[Connor MacLeod]

Maybe you should do calcs for two types of lasguns: the laser kind and the particle kind.

What do you mean?

[Hawkwings]

I mean, if you're trying to resolve two types of damage effects into one weapon, you might want to first try calcing them seperately first. Calc some vaporiztion numbers, then calc KE numbers, and see how different the results are.

[Connor MacLeod]

I mean, if you're trying to resolve two types of damage effects into one weapon, you might want to first try calcing them seperately first. Calc some vaporiztion numbers, then calc KE numbers, and see how different the results are.

Um, I'm not sure you're actually getting what I was talking about. The "two types of damage" are related to completely different mechanisms - thermal and mechanical. Mechanical damage is more akin to a bullet (or rather a bomb blast) in effect because its non thermal damage, and doesn't require that much energy to achieve (so little that minimal cauterization occurs - all you're doing is vaporizing a small section of the target - the rapidly and violently expanding vapor is what does the damage.)

The thermal effects are something else entirely (cauterization and/or vaporization.) at least as far as HOW they inflict damage. The thermal effects I am calcing have little to do (directly) with vaporization as far as lasguns effects on human bodies go - total vaporization would be an upper limit, at most, and in most cases lasguns don't vaporize large chunks of the body - only hotshots and hellguns do. And Lascannon. Partial vaporization WILL occur (probably around the impact point), but the cauterization calcs should account for that (every degree past the boiling point basically results in water being converted to steam, after all, and with the temps below for tissue cauterization, some of that will result in steam being created.)

The fact that they are "different" does not mean they are separately or distinctly created - they're brought about from the rapid injection of energy from the laser beam (shock waves can cause thermal as well as mechanical damage - thats how the TESB asteroids vaporized.) there aren't "two kinds" of lasguns, you have the same lasgun causing multiple effects.

The bit on "massless vs particle or kinetic" is simply noting that not all the sources seem to act as if lasguns are "true" lasers. The reference to "laser shells" in early 40K game fluff (1st and 2nd edition mainly) is a prime example of this. But in the case of a laser or particle beam, the effective results won't matter much (As the Atomic Rockets site notes. the only real difference is that the laser need be pulsed to allow time for the vapor to dissipate - partticle beams don't suffer from this limitation.) If they are "kinetic" as in a projectile of some kind (possible, but I consider this highly unlikely for the vast majority of lasguns) they probably have minimal "kinetic" effects - most of the energy will be "stored" in the projectile and released on impact. (these may actualyl be more like a kind of autogun or bolter though, instead of a lasgun. Those descriptions could, in some ways, also be considered to have been overwritten.)

Edit: I'm tired, so I'll get around to doing some example calcs (and posting some quotes from earlier fluff sources.) later. It should make more sense once I write up a few examples.

[andrewgpaul]

I always took the references to "laser shells" to mean short pulses, rather than beams - blasters rather than phasers.

[Teleros]

I don't think they're SW blaster-style - look at the IA books too to see glowing beams striking targets .

[Azazal]

I don't think they're SW blaster-style - look at the IA books too to see glowing beams striking targets .

Augghh!! attack of the changing fluff by GW!! Back in the olden days, circa 1991-92 or so, long before there was Necromunda, there was an in development game call Confrontation. It was going to be more like what Inquisitor became, but with Necroumunda and the gangs as the background. Anyhow, GW released many articles in WD that outlined about 90% of the game, including the first real indepth discussion of the various weapons. The las weapons were all described as firing high energy packets that exploded on impact, very much like a SW blaster. But given that GW loves to throw out the old, sai-la-vie.

[NecronLord]

Las packets were, frankly, a silly idea. It's called a laser, and now, it's very much like a laser. Which is good.

[Connor MacLeod]

I always took the references to "laser shells" to mean short pulses, rather than beams - blasters rather than phasers.

You can fire in short pulses or a continuous beam - there isn't neccesarily a whole lot of distinction between it, except the number of pulses and the duration between them. You're not realy going to "see" pulses as anything resembling a "Shell" or projectile really, it would look like a very short beam if anything.

Las packets were, frankly, a silly idea. It's called a laser, and now, it's very much like a laser. Which is good.

Well I did say it was a rather unlikely idea except maybe as a very rare weapon.

[Connor MacLeod]

Okay, I finally got off my butt and did the calcs. hopefully this will serve as an example of how the methodology ought to be done. I may go over it again as a remidner in future calcs (mostly when I start covering the Ghosts novels) but this also revises a number of prior calcs on the basis of the new data. Hopefully it will be the last time I need to do this, but I'm not holding out in that regard

I'm also taking some time to introduce a few new ones that I uncovered, some of which while from older sources, are from fluff (and thus useful against those people who like to toss out the novels or regard them as "lower" status.)

The shortt duration high energy [lasgun] beam produces such a rapid temperature change on the target's surface that it vapourises in a small explosion.

Only including this to verify the "vaporization" aspect. Doesn't tell us the amount of vaporization occuring, but it ought to occur along the path of the beam and the surrounding area (a diameter of at least several inches, and probably 4-6 inches depth) Given the "300-400 K" temps implied by the quotes I already provided, though, its quite probable that a significant amount of vaporization will occur once the water content in the body reaches boiling point (every degree beyond boiling point will result in vapor forming, just like when a pot of water is brought to the boil.)

Las weapons work by firing a blast of highly charged light which transforms into heat and kinetic energy upon impact, causing tissue damage and burning.

This confirms that there is both a thermal and 'kinetic" (ie mechanical/concussive) damage element to las weaponry, and that thermal effects (burning) is a significant partt of the damage mechanism.

"Tarok slumped down behind the rock.

...


As the stones pattered to the ground, a Deathlight flashed the stunted bushes itno flame. Tarok sprang up and fired at the Brannath who had just given away his position. The man fell forward out of the bushes with a fist-wide, smoking hole punched through his body from front to back. Strange, thought Tarok, that there is no blood.

That thought almost cost him his life. He almost failed to notice the shadow sliding over the rocks behind and right of him. The rock glowed and began to melt as he dived away from the beam of the Deathlight. The Brannath was not quick enough with his second shot.

Then, on all sides of him, the air was shot through with the deadly bright rods of soldier-lightning.

...

They were watching through their magic, he knew - the same magic that made the Deathlight spit its soldier-lightning.

A "fist sized" hole in a humanoid body implies at least around 10-12 cm diameter area cauterized (the hole plus some of the surrounding tissue). "Through" the body implies it passes through roughly 20-25 cm or so of torso (depending on physique.) We know its cauterized due to the "lack of blood" and the "smoking hole".

Assuming a cylindrical hole given the dimensions above, the amount of tissue affected would be around 1.5-2.8 kg, including the cauterization of the tissues around the hole.

Conservative estimates should put tissue temp at a minimum of 200C, the water content in the body should be raised to a temp of 173C.
Assuming tissue temps reach 300-400 C at least, this corresponds to the water content in the body (factoring in the differences in specific heat) of between 256-340 C. The temp of a human body is roughly 37 degrees C. Given that, this means that tissue temp must be raised by at least 163 degrees, the body water content by 136 degrees (200 C cauterization.) At 300-400C, the increase is 263 and 219 C (300 C cauterization) and 363 and 303 C (400 C cauterization)

Given the specific heats above, this translates to an energy input of:

- 571 kilojoules per kg at 200 C cauterization

- 921 kilojoules per kg at 300 C cauterization

- 1.271 megajoules per kg at 400 C cauterization.

This works out to a "per shot" las-bolt range of at least 860 kilojoules to 1.9 megatjoules at least (1.5 kg) to 1.6-3.55 megajoules per shot (2.8 kg)

AS a side note, another enemy evidently uses a las-weapon to begin melting the stone Tarok was hiding behind. It looks more like a sustained event, and its not easy to get an EXACT size on the rock (or properties), but even if it were a fairly small rock (say half a foot in diameter) it would weigh at least a few kg. Assuming silicon like properties it could easily take 5-6 megajoules to melt, and the whole event could be no more than a couple seconds, providing a secondary confirmation of the magnitude of the firepower.


Wargear 1993 page 26

It [the lasgun] fires an explosive energy blast with a similar effect to a bullet or small shell.

This gives us a comparison to work off of. Note, however, that while the EFFECT is similar, the mechanisms are dramaticallyh different (as I've explained before.) Lasers don't have any momentum the way bullets do

this link has a number of ballistics-gel tests involving firearms and wound profiles, showing how big a hole a bullet could reasonably be expected to make. In geenral you can expect a bullet or shell to make a (permanant) hole (for a rifle at least) to be 7-10 cm at its widest point. Shotguns seem to produce the widest holes, but have less penetration than a bullet.

If we assume 6 cm average diameter and 20 cm depth for a bullet, and a roughly cylindrical hole, we can infer between .57 kg worth of mass is affected.

If we assume a 10 cm diameter and 10 cm deep penetration for a shotguns shell and a cylindrical hole, roughly .79 kg worth of mass is affected.

Since I already worked out the energy inputs I will not repeat them here. the energy works out to roughly ~ 325 kilojoules to 724 kilojoules for the bullet, to ~451 kilojoules to 1 megajoule for the shotgun blast.

Danil Vorens lowered his smoking laspistol and returned his attention to the viewscreen before him. A stunned silance filled the defence control room, the technicians agog at what had just happened. Lutricia Vijeon stared in open mouthed hoor at the corpse lying in the center of the room with a ragged hole where its face had been.

Since I already calculated the temps and energies, I'll just go with the masses. Assuming a roughly 20 cm diameter head and a hemispherical "crater", the hole could probably be around 1-2 kg (depending on how conservative you take it), leading to a laspistol firepower of between 600 kilojoules and ~3 megajoules per shot.

The bolt impacted. It tunnelled and exploded. Flesh and bone or a vital organ erupted. It was ever this roudy way. By contrast, laspistols were silent in operation. If the aim was inaccurate, the scalpel-blade of energy soon dispersed. Whener a las-pulse met its target: such lacerating flare-up, such a scream of agony, if the victum still had the breath and lungs and heart to scream. Perhaps ten of the pilgrams had fled. A score more lay dead or dying, almost all thanks to the laspistols."

last time I did the calc I only toko into account what I could find for heart/lung mass (which worked out to between half a kilo and a kilo, depending on source) That, however is tremendously conservative, given that to reach the lungs one has to penetrate through the flesh and even bones (ie ribcage) protecting them, which means a substnatially greater amount of flesh will be affected. In terms of volume, we know the heart and most of the lungs are destroyed (lungs may only be partly destroyed). This probably implies a roughly head sized (or larger) volume affected, if not the whole chest. It owuld also have to reach between 4 and probably 6 inches (10 to 15 cm) into the chest to do anyy real damage. This will roughly translate to at least 3-5 kgs of flesh being affected. Which in turn, given the above figures already calced, yields 1.7 to 6.4 megajoules per shot.

A las-blast felled the armsman beside Semper. The captain grabbed the man as he fell, intending to drag him into the bay, but then found himself staring into the excavated crater of the man's skull, where the las-shot had blown half his head away.

Half the head probably means around 2-3 kg or so (a bit more, ,if we factor in the probable crater) is blasted off. This leads to roughyl 1.14 megajoules to ~3.8 megajoules per bolt.
This is conservative also because it assumes the armsman was bareheaded, which is not neccsarily true. It also doesn't factor in whether it was a rifle or a pistol (doesn't say. Its going to be at least a rifle, but if it was a pistol the rifle version woudl arguably be more powerful.)

A stray shotgun blast took off the head of the man next to him, adding another corpse to the carpet of bodies that littered the passageway.

Now, this isn't a las weapon really, but the aforementioned rogue Trader source mentions that lasguns inflict damage comparable to a bullet or small shell, which can quite possibly mean a shotgun shell. In that case its probably twice the value of the calc above, since you're basically blasting the entire head off (~2.3 to 7.6 megajoule). Not confirmed though, so this is more of an implied calc than anything else (but not unreasonable.)

And, ,there we go! Hopefully in the future those of you using these calcs will have a better time explaining them, or be able to presnt better numbers at least. If there is any confusion, just pm and I can try to explain it again.

[Nyrath]

There is a new website on laser weapons that is slowly filling up with some crunchy hard-science goodness:
http://panoptesv.com/SciFi/DeathRay.html
The author is an actual physicist. Email him with encouragement to keep working on it.

[Falkenhayn]

It looks like the one to three megajoule range is the most recurring number, with 600kj and 7 mj outliers. Would it be reasonable to use that range when referencing your calcs?

[NecronLord]

Looks like. Fortunately, discrepancies can be smoothed out as most lasguns have settings. Some three settings, some two, some more elaborate ones seem to have a variable slider. So anything between one to six (or indeed, nineteen, if one want's to call 'megathules' megajoules) seems possible.

[Connor MacLeod]

There is a new website on laser weapons that is slowly filling up with some crunchy hard-science goodness:
http://panoptesv.com/SciFi/DeathRay.html
The author is an actual physicist. Email him with encouragement to keep working on it.

Thanks! I looked over that site and it looks fascinating, and I think I may have to re-think or revise some of my conclusions/analysis.

Tenatively, my calcs will probably assume the "heat ray" style effect. In most of the novel examples I'll likely be calcing they have a noticable duration (they fire long enough to be noticable by the human eye, and to produce a noticable beam) so we're probably talking a sustained effect in that regard. Some may be more "rapidly pulsing" of course, but I'll have to think about that (that sounds more like the "insta vaporize" interpretation I initially used. Then again at the higher cauterization temps the distinction becomes alot less major anyhow..)

Anyways, thanks.