CT Only: Hull and Bulkhead Thickness-Classic Traveller

[Timerover51]

Based on the material in the Classic Version of Traders and Gunboats, the adventure Chamax Plague, and the adventure Annic Nova, the hull thickness and bulkhead thickness of a commercial starship in Classic Traveller is about 10 millimeters in thickness of steel. The standard internal partition should be about 1 millimeter of steel plate equivalent, or maybe 3 millimeters of aluminum. That is based on, in the Annic Nova, 200 millimeters of steel armor requiring 20,000 damage points from laser fire or a cutting torch to cut through, while ship bulkheads require 1000 damage points and internal partitions require 100 damage points. Ten millimeters is pushing it to stop full rifle caliber AP rounds, such as the WW2 .30-06 round. Because the ship bulkhead presents a flat face to the internal pressure of the ship, and they are intended to maintain internal pressure in the event of damage elsewhere, they may actually be thicker than the ship hull. In Chamax Plague, the Chamax acid ate through the ship hull and the ship bulkheads, apparently with equal ease.

 

[Vladika]

Based on the material in the Classic Version of Traders and Gunboats, the adventure Chamax Plague, and the adventure Annic Nova, the hull thickness and bulkhead thickness of a commercial starship in Classic Traveller is about 10 millimeters in thickness of steel. The standard internal partition should be about 1 millimeter of steel plate equivalent, or maybe 3 millimeters of aluminum. That is based on, in the Annic Nova, 200 millimeters of steel armor requiring 20,000 damage points from laser fire or a cutting torch to cut through, while ship bulkheads require 1000 damage points and internal partitions require 100 damage points. Ten millimeters is pushing it to stop full rifle caliber AP rounds, such as the WW2 .30-06 round. Because the ship bulkhead presents a flat face to the internal pressure of the ship, and they are intended to maintain internal pressure in the event of damage elsewhere, they may actually be thicker than the ship hull. In Chamax Plague, the Chamax acid ate through the ship hull and the ship bulkheads, apparently with equal ease.

Structurally, that might as wells be aluminum foil. There's not enough rigidity there for an internal wall diaphragm to hold it's shape or resist denting in any way. For whatever armor value, I go with 3-4 inches of wall thickness both for the required rigidity as well as in-the-wall/bulkhead utilities.

As for the exterior walls/hull, 10mm may be OK with sufficient frame reinforcing. I'm not going to get into the wet/dry navy thing but these ships are supposed to be able to land in water.

 

[The Oz]

When I did my calculations on how the armor ratings of the hull could limit the maximum speed of TRAVELLER ships, I used the specified value of 40 (in STRIKER terms) as the armor rating of a civilian hull. That back-calculates to a hull thickness of 33.6 cm of hard steel.

I've always thought that was too thick for a hull, so I home-ruled that standard civilian spacecraft hulls were forged from crystaliron, which reduced the thickness to a more reasonable value. Civilian hulls built of higher-tech materials (superdense, bonded) were rare IMTU, and were assumed to be thinner, thus maintaining the same armor value.

 

[mike wightman]

Yup, I used the armour materials from Striker to describe hull material too, which became canon with MT (although their factors were not the same as Striker)

At TL 7-9 that means composite materials for hulls, which have double the toughness of hard steel so your hull is half as thick as if it is made of hard steel.

TL 10-11 crystaliron alloys which are four times as tough so your hull is a quarter of the thickness of the equivalent steel hull.

TL 12-13 superdense is seven times tougher than hard steel...

TL 14-15 bonded superdense is fourteen times tougher than hard steel...

Since these TLs map to the armour table in HG2 I was happy enough.

Note that MT introduced coherent superdense at TL 17+ which is twice the toughness of bonded superdense.

 

[Timerover51]

When I did my calculations on how the armor ratings of the hull could limit the maximum speed of TRAVELLER ships, I used the specified value of 40 (in STRIKER terms) as the armor rating of a civilian hull. That back-calculates to a hull thickness of 33.6 cm of hard steel.

I've always thought that was too thick for a hull, so I home-ruled that standard civilian spacecraft hulls were forged from crystaliron, which reduced the thickness to a more reasonable value. Civilian hulls built of higher-tech materials (superdense, bonded) were rare IMTU, and were assumed to be thinner, thus maintaining the same armor value.

Hmmm, the side armor of the Iowa-class battleships of the US Navy is 12 inches, or 305 millimeters of face-hardened steel armor plate. So a Striker armor value of 40 makes a star ship more heavily armored all over than the side armor of an Iowa-class. Interesting. And that 40 value armor has to be bent as well.

Out of sheer curiosity, how thick is the metal on the Iris valves and hatches in the hull? Eyeballing the manual hatches on ship deck plans, they look to be roughly 3 feet or 1 meter in diameter. For every 25.4 millimeters of steel, the hatch weighs a minimum of 282 pounds. Your player is standing on a ships ladder, trying to open a hatch weighing more than he does, and that assumes a steel thickness of 25.4 millimeters of 1 inch. At a thickness of 8 inches or 203 millimeters, the hatch weighs 2,256 pounds.

Also, in Chamax Plague, the Chamax have no problem melting through, with their internal acid, the bulkheads and hull of the Shaarin Challenger. If the hull and bulkheads are as thick or resistant as the side armor of an Iowa-Class battleship, then a vacc suit hit with the acid and the person wearing the vacc suit should be dissolved almost instantaneously. The vacc suit is rated at taken 25 points in acid damage, bulkheads 1000.

The rule of thumb for a demolition charge to breach steel plate is the charge weight of TNT in pounds is equal to the cube of the thickness of plate to be breached. This does not assume a shaped charge, as a shaped charge large enough to punch a one meter diameter hole in a 305 millimeter armor plate is going to at least one meter in diameter, and require a stand-off distance equal to 6 times its diameter. For a straight demolition charge, that means about 1700 pounds of TNT. The Japanese developed a aerial shaped charge for punching through battleship side armor in WW2, using a twin-engine bomber as a suicide plane. The weight, allowing for internal liner and external casing to contain the charge and help focus the blast came out to about 1800 pounds. I will leave it to your imagination of what happens to that compartment if you touch off that much explosive inside of a space ship hull. If you use a more energetic explosive than TNT, you reduce the weight, but still need the energy equivalent of TNT.

I think that I will stick with my initial conclusions, as those are in line with submarine hull contraction, which is reasonably close to the pressure requirements for a space ship hull.

Edit Note: A correction to the weight of the Japanese Sakura-2 shaped charge warhead. Total weight was 1300 kilograms, with an explosive weight of 900 kilograms of an RDX-based compound, which would have been considerably more energetic than 900 kilograms of TNT. The diameter was 1 meter, and with some standoff, should be able to penetrate 30 centimeters or more of steel plate. It was not what I would call a precision shaped charge, having a hemispheric liner of steel.

 

[Carlobrand]

Based on the material in the Classic Version of Traders and Gunboats, the adventure Chamax Plague, and the adventure Annic Nova, the hull thickness and bulkhead thickness of a commercial starship in Classic Traveller is about 10 millimeters in thickness of steel. The standard internal partition should be about 1 millimeter of steel plate equivalent, or maybe 3 millimeters of aluminum. ...

Structurally, that might as wells be aluminum foil. There's not enough rigidity there for an internal wall diaphragm to hold it's shape or resist denting in any way. For whatever armor value, I go with 3-4 inches of wall thickness both for the required rigidity as well as in-the-wall/bulkhead utilities.

As for the exterior walls/hull, 10cm may be OK with sufficient frame reinforcing. I'm not going to get into the wet/dry navy thing but these ships are supposed to be able to land in water.

CT canon splits ways with Striker. The 1000-point bulkhead wall is the standard for Supplement 7, Adventure 1 (the Kinunir), Double Adventure 3 (Death Station) and Adventure 10 (Safari Ship), that last one published 3 years after Striker. And, as Timerover pointed out, the chamax don't much care whether they're facing hull or bulkhead. In each adventure, the bulkhead is described as serving both for internal compartmentalization and for the outer hull. One hopes there is some sort of framing or skeleton to support these walls. Me and my trusty laser rifle, we can hypothetically burn through a Safari ship bulkhead or hull wall in an average 57 shots - which is a little odd since I thought it delivered a quick penetrating pulse, not something I could cut with, but I'll assume there's some trick to a TL 9 laser weapon that my TL 7 player self doesn't know about. 57 shots, that suggests something like a 5 cm cut per shot.

However, Striker paints a picture of a civilian ship hull that can stop tank rounds up to 75 mm. Faced against a Striker hull, there's no way we're making much of a mark with my laser rifle.

Handling the dichotomy depends on your agenda. You could deal with them as distinct and separate parallel universes - but in one of those, all the adventures where you need to cut through bulkheads aren't gonna work the same. Or, you could merge them and make the hull thick and the bulkheads and flooring 10 mm equivalent. That doesn't work for the Chamax, though - they either can't get through a ship's hull in anything short of around 1500 or so hits, or you upgrade their venom by a factor of about 30 and they're burning through interior bulkheads in a couple of shots (and otherwise behaving rather like a Horta). It's just - well, they're very different treatments of the hull/bulkhead.

An internal wall partition with the strength of 1 mm steel does not necessarily have to be a 1 mm steel wall. It could be 8 mm of some sound-absorbing rigid plastic compound that happens to be 1/8 the equivalent strength of steel, held up by framing every meter or two.

 

[mike wightman]

The 1000 points of damage makes a hole "big enough for a person to pass through", not a small penetration.

Your laser rifle takes 57 shots to make this gap, it penetrates and makes a small hole first I would imagine.

The rules, sadly, don't make an issue of this.

 

[aramis]

Note that Striker also presumes a much tougher armor material than steel - that 33.3cm equivalent is about 2.4cm of TL14 Bonded, or 4.8cm of TL12-13 Superdense. Or 8.3cm of Crystaliron.

 

[Timerover51]

Note that Striker also presumes a much tougher armor material than steel - that 33.3cm equivalent is about 2.4cm of TL14 Bonded, or 4.8cm of TL12-13 Superdense. Or 8.3cm of Crystaliron.

As stated earlier, mass is what stops a shaped charge jet. A WW2 German Panzerfaust was capable of effective penetration of 8 inches of steel plate, or 203 millimeters. All of those would be readily penetrated in the Real World by WW2 technology. Something like the current version of the TOW missile would probably blow a full-caliber or better hole through the plate. Depending how creative you get with something like an increased energy PBX-based or Octol-based explosive, extended stand-off detonation, and an exotic liner material, it might be possible to push penetration beyond current technology by a factor of 2 or more. I would have to dig out my copies of Striker, but it looks like Striker vehicles would be extremely vulnerable to shaped charge warheads.

Also, a 12 inch gun, assuming a muzzle velocity of 2600 feet per second or so, with a Armor-Piercing projectile weighing about 850-900 pounds, should be able to penetrate 12 inches or 305 millimeters of armor plate at point-blank range. Now, if that Striker 40 armor factor is equal to 33.6 centimeters of steel armor, then it could take a direct 90º angle hit from a 12 inch gun at the muzzle. The target would have to deal with the kinetic energy of the projectile however, about 39,000 foot tons or so. I would have to get out my armor penetration tables to figure out what a US Navy 16 inch gun, firing a 2700 pound AP round at 2500 feet per second would do at close range.

 

[Piper]

You're ignoring creative advances in armor technology such as ceramics, composites and explosive reactive armor.

Just out of curiosity, you're seriously attempting to determine plating thickness based on a rule that allows you to shoot a man-accessible opening through walls with a pistol?

 

[Enoki]

As stated earlier, mass is what stops a shaped charge jet. A WW2 German Panzerfaust was capable of effective penetration of 8 inches of steel plate, or 203 millimeters. All of those would be readily penetrated in the Real World by WW2 technology. Something like the current version of the TOW missile would probably blow a full-caliber or better hole through the plate. Depending how creative you get with something like an increased energy PBX-based or Octol-based explosive, extended stand-off detonation, and an exotic liner material, it might be possible to push penetration beyond current technology by a factor of 2 or more. I would have to dig out my copies of Striker, but it looks like Striker vehicles would be extremely vulnerable to shaped charge warheads.

That isn't entirely true. The material makes a huge difference. A shaped charge would have almost zero penetration on many ceramics 20 cm thick. Composite armor used on modern tanks uses a variety of materials to dissipate and disrupt the jet.
If you assume that starships are built with something other than steel or some variant there of, then it is possible a bulkhead might be just a few centimeters thick and capable of stopping current technology weapons.

Also, a 12 inch gun, assuming a muzzle velocity of 2600 feet per second or so, with a Armor-Piercing projectile weighing about 850-900 pounds, should be able to penetrate 12 inches or 305 millimeters of armor plate at point-blank range. Now, if that Striker 40 armor factor is equal to 33.6 centimeters of steel armor, then it could take a direct 90º angle hit from a 12 inch gun at the muzzle. The target would have to deal with the kinetic energy of the projectile however, about 39,000 foot tons or so. I would have to get out my armor penetration tables to figure out what a US Navy 16 inch gun, firing a 2700 pound AP round at 2500 feet per second would do at close range.

Just to show the difference here with the above example:

Change the armor to wrought iron (a minor variation in carbon content makes that happen) and that 12" shell now goes through nearly 30" of plate. Change it to Harvey nickel and its about 18".
So, given the technology we are postulating it could very well be possible to get the thickness down to just a few inches and theoretically stop a 12" round.

This requires that we accept that in the time forward people have invented materials far tougher, denser, heat resistant, whatever than we have today. That is reasonable.

 

[Timerover51]

You're ignoring creative advances in armor technology such as ceramics, composites and explosive reactive armor.

Hmm, you are going to put explosive reactive plates all over your ship. Note I do know about explosive reactive plating. Interesting.

As for the ceramics and composites, I actually do know about those as well. However, I am looking at the quoted armor and equivalent thicknesses.

Just out of curiosity, you're seriously attempting to determine plating thickness based on a rule that allows you to shoot a man-accessible opening through walls with a pistol?

I am looking at the amount of damage inflicted by an energy device, be it laser or cutting torch (see the Annic Nova adventure) or whatever, to include Chamax acid, to achieve a roughly one meter hole in a thickness of plating. The Annic Nova gives me one hard data point, the 200 millimeters of steel plate requiring 20000 points of damage. The amount of energy required to cut a hole through steel plating is proportional to the thickness of the plating, although, if anything, I should give the thicker plate a bonus for heat absorption by the surrounding plate. In numerous places, it is stated that 100 points of damage from some form of energy device with cut a one meter hole through ship partitions, and 1000 points of damage from an energy device will cut a one meter hole through the ship bulkhead. The gives the proportional thickness of the bulkhead and interior partitions to 200 millimeters. It is also stated in numerous places that 1000 points of damage from a projectile weapon will produce a one meter hole in the interior partition, while the normal projectile weapon will not penetrate the bulkhead.

Now, in the Final Report of the NATIONAL DEFENSE RESEARCH COMMITTEE in World War 2, dated September 1945, Weapon Data: Fire-Impact-Explosion, under page 2C2, discussing Perforation of Plastic Protection, I find that the US .30 caliber M2 AP round, at a velocity of 2580 feet per second, required 1.10 inches of mild steel or .75 inches of Special Treated Steel to provide a 95% level of protection from a 200 yard range normal impact. An additional chart on the page indicates that at 200 yards range, the M2 round had a 60% probability of inflicting a pinhole perforation in one-half inch of homogenous hard steel plate of 415 Brinell hardness. Other sources give the penetration of that round in armor steel at 200 yards of 0.3 inches. The muzzle velocity of the round, per the 1944 Ammunition Inspection Guide, was to be 2,775 feet per second. Presumably, given the widespread use of cloth armor, most characters will be carrying rifles loaded with armor-piercing ammunition. Based on all of this, and allowing for a high-strength steel alloy to be used for the bulkheads and hull, a thickness of about 10 millimeters appears to be warranted. To be on the safe side, you could also use 15 millimeters, and figure that the thicker 200 millimeter plate gets a bonus for heat absorption.

That fact that acid damage from the Chamax is treated in the same proportion between partitions and bulkheads, with the ability to also penetrate the ship hull, demonstrates that the proportions are correct, as acid damage will be proportional as to thickness.

 

[Piper]

Hmm, you are going to put explosive reactive plates all over your ship. Note I do know about explosive reactive plating. Interesting.

No, I was actually suggesting that your earlier statement that "mass is what stops a shaped charge jet" was an oversimplification.

All of your impeccably researched ballistics data notwithstanding, the fact remains that none of the rules in question was actually written to define plating thickness.

Hull thickness was explicitly defined in "Striker". Yes, the "Striker" numbers are, well ... "improbably generous" might be a polite way of phrasing it. I have a sneaking suspicion that the selected value had very little to do with engineering principles. You're not the first to have pondered this.

Chamax acid was defined in "Striker" terms in JTAS 17: "Acid has a penetration value of 2 each turn per bug."
Bear in mind that the Chamax were not intended to define plating thickness either.

 

[Timerover51]

No, I was actually suggesting that your earlier statement that "mass is what stops a shaped charge jet" was an oversimplification.

All of your impeccably researched ballistics data notwithstanding, the fact remains that none of the rules in question was actually written to define plating thickness.

Hull thickness was explicitly defined in "Striker". Yes, the "Striker" numbers are, well ... "improbably generous" might be a polite way of phrasing it. I have a sneaking suspicion that the selected value had very little to do with engineering principles. You're not the first to have pondered this.

Chamax acid was defined in "Striker" terms in JTAS 17: "Acid has a penetration value of 2 each turn per bug."
Bear in mind that the Chamax were not intended to define plating thickness either.

I am simply trying to make some sense out of the various comments on plating and penetration contained in Classic Traveller, not Striker. I will make no comments with respect to Striker armor.

 

[Timerover51]

That isn't entirely true. The material makes a huge difference. A shaped charge would have almost zero penetration on many ceramics 20 cm thick.

Cite sources for your comment please.

Composite armor used on modern tanks uses a variety of materials to dissipate and disrupt the jet.

It is also far more expensive than simple steel, and does not lend itself readily to being bent and curved. It functions best when used as a flat plate.

If you assume that starships are built with something other than steel or some variant there of, then it is possible a bulkhead might be just a few centimeters thick and capable of stopping current technology weapons.

I am assuming that the future will be using the same Periodic Table chart of the Elements that we are. Any additions are going to be beyond the mass of the Transuranic Elements, and correspondingly extremely heavy. Aside from steel, the only other major metal available to work with is Titanium, although if a sufficient supply of Beryllium is available, you could work with a Aluminum-Berylium alloy, although Beryllium is quite toxic. Then you have copper and its alloys. Any form of composite laminate is going to cost a lot more than simple steel, and we are talking commercial, private vessels here, not warships.

Just to show the difference here with the above example:

Change the armor to wrought iron (a minor variation in carbon content makes that happen) and that 12" shell now goes through nearly 30" of plate. Change it to Harvey nickel and its about 18".
So, given the technology we are postulating it could very well be possible to get the thickness down to just a few inches and theoretically stop a 12" round.

You also have a difference in penetration depending on whether or not you are firing a capped or an uncapped projectile, as a capped projectile is best at penetrating face-hardened armor, while for homogenous armor, uncapped projectiles are best. The conversion factor for Wrought Iron, which is considerably more than just a variation in carbon content, from Krupp Face-Hardened armor is 2.6, while the Figure of Merit for Krupp verses Harvey Face-Hardened armor is 1.3. Those figures come from the Royal Navy Gunnery Manual for 1915, along with a variety of other sources. Both Krupp and Harvey contain nickel, along with other alloys, the principal difference being the manner in which the front face of the plate was enriched with carbon. The Harvey process yielded a plate with a pronounced boundary between the very hard enriched carbon face and the softer but tougher back, while the Krupp process produced a gradual reduction in the carbon enrichment, avoiding the sharp discontinuity.

You also still have to absorb the kinetic energy of impact, even if you postulate stopping the round with a few centimeters of plate. I will not even begin to address the difference in resistance depending on the temperature of a given plate.

This requires that we accept that in the time forward people have invented materials far tougher, denser, heat resistant, whatever than we have today. That is reasonable.

Hmmm, I do not view that as reasonable unless you assume a significant expansion of the current Periodic Table of the Elements. Iron has been around for over 3,000 years, and is still in extremely wide use, having the advantages of being cheap, widely available, and relatively easy to process. Your other available metals in use are titanium, copper, and aluminum. Beryllium is light, strong, rigid, and also expensive and toxic. Magnesium does have this distressing tendency to burn readily.

I am looking at commercial ships here, requiring to be operated at a profit, which means that the cost of the ship is a major factor. If you are going to replace steel or aluminum with something else, it had better be in the same order of price. Composites and Laminates are going to have a very hard time achieving that.

 

[aramis]

Shaped charge warheads have two effects - concussive force, and heating. Many do most of their damage by heating, not concussion. If the ceramic doesn't shatter from the concussive force, it's NOT going to melt and soften.

 

[Timerover51]

Shaped charge warheads have two effects - concussive force, and heating. Many do most of their damage by heating, not concussion. If the ceramic doesn't shatter from the concussive force, it's NOT going to melt and soften.

Again, cite your sources for that information.

 

[Carlobrand]

I don't seriously see a problem in attempting to determine plating thickness based on a rule that allows me to shoot a man-accessible opening through walls with a pistol, if the game repeatedly says I can do it and then gives me enough information about the pistol. We do that kind of thing all the time with any number of rules and any number of pieces of equipment. It's certainly no worse than trying to speculate on the properties of a fusion power plant based on a rule about fuel consumption, or trying to figure out whether a grav drive would crush someone standing beneath it. It's an interesting mental exercise, and once in a while it gives us a way to add a little color to the game. For example, if you can cut a bulkhead with a laser, maybe you can give your players' lasers a "tool" setting that allows them to be used as low power cutters when needed for other purposes. Like ice carving.

With respect to a ship's hull or bulkhead, again, we are dealing with two very different interpretations. CT has us cutting through hulls with our laser rifle. Striker has ordinary hulls strong enough to stop a WW-II tank's round, hulls that aren't going to notice our laser rifle. Whether mass does or does not stop, or whether a composite or ceramic can be made to serve as hull, all fascinating. I'm saving a lot of this info for my own use later. However, I do not feel we know enough about the properties of crystaliron or superdense armor to be able to say anything other than what the game chooses to say about them, they being fictional armors invented by the game.

We are playing a science fiction game. We are in some ways constrained by how the milieu and rules say the materials are performing - or we abandon those and write new rules that better fit our knowledge of science. If the game decides that 4.8 cm of superdense armor or 8.3 cm if crystaliron can stop the jet of incandescent plasma created by a shaped charge of X diameter, then one concludes there is some feature of superdense armor or crystaliron that we don't understand - maybe unusual strength in molecular bonds, maybe extremely rapid heat conductivity, maybe I'm clueless and someone with a better understanding of the physics of shaped charges and their interactions with materials can speculate more effectively - that allows it to do that. Alternately, we can grind our teeth and accept the inconsistency, as we do with the lasers of magical range or the clouds of sand that seem to stop those lasers when our hull won't. Or, we decide to rewrite the rules.

 

[aramis]

I don't seriously see a problem in attempting to determine plating thickness based on a rule that allows me to shoot a man-accessible opening through walls with a pistol, if the game repeatedly says I can do it and then gives me enough information about the pistol. We do that kind of thing all the time with any number of rules and any number of pieces of equipment. It's certainly no worse than trying to speculate on the properties of a fusion power plant based on a rule about fuel consumption, or trying to figure out whether a grav drive would crush someone standing beneath it. It's an interesting mental exercise, and once in a while it gives us a way to add a little color to the game. For example, if you can cut a bulkhead with a laser, maybe you can give your players' lasers a "tool" setting that allows them to be used as low power cutters when needed for other purposes. Like ice carving.

With respect to a ship's hull or bulkhead, again, we are dealing with two very different interpretations. CT has us cutting through hulls with our laser rifle. Striker has ordinary hulls strong enough to stop a WW-II tank's round, hulls that aren't going to notice our laser rifle. Whether mass does or does not stop, or whether a composite or ceramic can be made to serve as hull, all fascinating. I'm saving a lot of this info for my own use later. However, I do not feel we know enough about the properties of crystaliron or superdense armor to be able to say anything other than what the game chooses to say about them, they being fictional armors invented by the game.

We are playing a science fiction game. We are in some ways constrained by how the milieu and rules say the materials are performing - or we abandon those and write new rules that better fit our knowledge of science. If the game decides that 4.8 cm of superdense armor or 8.3 cm if crystaliron can stop the jet of incandescent plasma created by a shaped charge of X diameter, then one concludes there is some feature of superdense armor or crystaliron that we don't understand - maybe unusual strength in molecular bonds, maybe extremely rapid heat conductivity, maybe I'm clueless and someone with a better understanding of the physics of shaped charges and their interactions with materials can speculate more effectively - that allows it to do that. Alternately, we can grind our teeth and accept the inconsistency, as we do with the lasers of magical range or the clouds of sand that seem to stop those lasers when our hull won't. Or, we decide to rewrite the rules.

There's a big difference between a laser and a KE shell.

In a KE shell, in penetration, the KE has to deform the metal sufficiently to exceed the tensile strength. If it doesn't, it either deforms or elastically rebounds.

In a Laser, it just has to exceed the heat dissipation capability of the spot hit to do damage - it may not penetrate the armor, but it can slowly wear the armor down in a way that KE rounds cannot.

You can literally shoot 50000 5.56 rounds at a chunk of 1" modern armor steel and only scratch the paint, and if fast enough, make a small deformation and some localized heating. You can't get enough heating to cause a failure. 12.7mm, same target, a few thousand autofire rounds later, you've got a bowl - it can't dissipate the heat fast enough, and begins to deform under the pressure. 20mm, same target, same ROF, you penetrate in a few dozen rounds - the KE doesn't even have time to transition fully to heat up, and so the steel deforms. 120mm, it punches right through with the first round - the impact energy simply deforms the metal too fast to heat it.

Likewise, you can't cut that 1" sheet steel with a plumber's torch - it can dissipate the heat faster than the propane flame generates it. Oxy-Acetylene can, but it's slow, multi-pass. Localized heating is FAR faster.

But the laser — if high enough to matter at all — strips off surface layers with every hit and heats the surrounding area. That stripping effect is literally vaporizing the metal. If tuned right, the pulse rate allows the vaporized metal out, carrying much of the applied heat (and thus not giving it as much time to travel into the adjacent material), resulting in more localized and precise cuts.

It's not that the laser penetrates the tank-like armor of a hull - it's that it errodes it.

 

[Carlobrand]

There's a big difference between a laser and a KE shell.

In a KE shell, in penetration, the KE has to deform the metal sufficiently to exceed the tensile strength. If it doesn't, it either deforms or elastically rebounds.

In a Laser, it just has to exceed the heat dissipation capability of the spot hit to do damage - it may not penetrate the armor, but it can slowly wear the armor down in a way that KE rounds cannot.

You can literally shoot 50000 5.56 rounds at a chunk of 1" modern armor steel and only scratch the paint, and if fast enough, make a small deformation and some localized heating. You can't get enough heating to cause a failure. 12.7mm, same target, a few thousand autofire rounds later, you've got a bowl - it can't dissipate the heat fast enough, and begins to deform under the pressure. 20mm, same target, same ROF, you penetrate in a few dozen rounds - the KE doesn't even have time to transition fully to heat up, and so the steel deforms. 120mm, it punches right through with the first round - the impact energy simply deforms the metal too fast to heat it.

Likewise, you can't cut that 1" sheet steel with a plumber's torch - it can dissipate the heat faster than the propane flame generates it. Oxy-Acetylene can, but it's slow, multi-pass. Localized heating is FAR faster.

But the laser — if high enough to matter at all — strips off surface layers with every hit and heats the surrounding area. That stripping effect is literally vaporizing the metal. If tuned right, the pulse rate allows the vaporized metal out, carrying much of the applied heat (and thus not giving it as much time to travel into the adjacent material), resulting in more localized and precise cuts.

It's not that the laser penetrates the tank-like armor of a hull - it's that it errodes it.

Okay, I gather you're not refuting the point that this is a game, or that we can either accept the future tech or rewrite it. I think you're focused in on the ship hull stopping KEAP and then coming under sustained laser rifle fire, yes? The, "We're trying to cut our way in," scenario.

So, I'm looking at my trusty laser rifle: by Striker, equipped with a TL 9 4 kg battery giving it 100 shots, said battery by Striker apparently able to hold 9 megawatt-seconds of power - which nicely matches the price. And, CT says I can make a hole I can get through with about 57 shots, so I'm delivering about 5.13 megawatts of energy to the armor, yes?

My trusty Wikipedia article on Iron says it's got a heat of fusion of 13.81 kilojoules per mole. And there's 55.85 grams of iron in a mole. This means if I can get that much energy into 55.85 grams of iron, it goes all gooey. I'm going to go with not trying to vaporize: that takes a lot more energy, and my gut tells me we'll affect more hull by just letting it flow off.

Steel I don't know for. Maybe we can see where we end up with the iron and figure whether the difference will matter or not.

Here I get the weak-kneed physics. If I can get 5.13 megawatts of power out of the battery and deliver it more or less instantly to the iron with 100% efficiency and not have it dissipate away too badly while I'm doing it, I can bring 371 moles of iron to that ooey-gooey state? 20,747 grams? A bit under 21 kilograms?

And 21 kilograms of iron at 7.874 grams per cubic centimeter is 2635 cubic centimeters - a bit over 2 and a half liters. So, under impossibly perfect conditions of translating the power from battery to the hull, I can make a crater 10.77 cm deep and 21.54 cm across in an iron hull - thereby getting about a third of the way through the hull? And, of course, I got a lot of it wrong with short-cuts and the dissipation issue, so it's probably less than that. There's some play there, it doesn't have to be a hemisphere, but I don't see me making a hole I can crawl through that way. And, I'm thinking I'm not going to enjoy as much success with steel or one of the sci-fi materials. It's an interesting idea, but I think I need more batteries.

Like I said, we're dealing with two very different interpretations of the game. We can decide not to look too closely at the physics and say, "Yes, you succeeded in melting a hole through the hole big enough to squeeze through after 60 shots." Or we can change the rules a bit, run numbers and tell the player to go recharge his battery a dozen times as he makes slow but visible progress, though canon says he should'a been able to get through on just the one battery. I don't think he'll gripe too badly so long as his end goal is achieved.

Of course, then we still have interior bulkheads that are supposedly identical in strength to the hull. Either they can stop tank rounds and I really shouldn't worry about letting loose with my FGMP inside the ship, or we need some tapdance explanation to explain why the thinner interior bulkheads take as much work to cut through as that hull did. Maybe we come back to the problem of burning holes through and losing energy, try to explain it that way.

But then, something on the other side of that interior bulkhead is gonna take a whole lotta laser hits. Hmmm - gotta think on that.