CT Only: Hull and Bulkhead Thickness-Classic Traveller

[Timerover51]

Or, we decide to rewrite the rules.

I rewrite the rules, as I do for a lot of my games.

 

[Piper]

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.

I don't see a problem with it either, as such, but reverse engineering from sketchy rules can easily lead one astray.

Consider the Chamax acid issue. Chamax can melt a one meter hole in an interior wall in a little over a minute:

100 points divided by 6D times 3.5 average per die comes out to 21 points per round.

JTAS 17 gave Chamax a Striker penetration of 2 per 30 seconds. That's 4 after a minute, equivalent to an armor thickness of 1cm steel for an interior wall. Multiply that by 10 for a bulkhead and you get an armor value of 40.

Different set of assumptions, different path, different outcome.

That being said, I would still allow players to shoot their way through a wall if the story needed it to happen (there's always void spaces for wiring and plumbing).

 

[Timerover51]

I don't see a problem with it either, as such, but reverse engineering from sketchy rules can easily lead one astray.

Consider the Chamax acid issue. Chamax can melt a one meter hole in an interior wall in a little over a minute:

100 points divided by 6D times 3.5 average per die comes out to 21 points per round.

JTAS 17 gave Chamax a Striker penetration of 2 per 30 seconds. That's 4 after a minute, equivalent to an armor thickness of 1cm steel for an interior wall. Multiply that by 10 for a bulkhead and you get an armor value of 40.

Different set of assumptions, different path, different outcome.

That being said, I would still allow players to shoot their way through a wall if the story needed it to happen (there's always void spaces for wiring and plumbing).

Actually, steel plating of 10mm to 12.7mm, 0.4 inches to 0.5 inches, or 16 to 20 pound weight, (wet ship plating is often given in pounds per square foot of weight) is quite common for use as water-tight bulkheads is wet ship construction. A hull thickness of a half inch is also quite common in ships of less than 2,000 tons intended for commercial use. Considering that you are looking at a pressure differential of one atmosphere, a half inch thick hull would be adequate for a wide range of ships, especially if using a high tensile strength steel, such as HY-80 or better. I can see something like an HY-120 or so steel used in the future.

 

[aramis]

For comparison purposes: that 10mm is Striker/MT AV=4; 12.5mm is AV=5.

 

[Enoki]

Cite sources for your comment please.

Personal experience for one. For a number of years I was working in the advanced materials research field, not as a scientist but rather as an engineer building the devices the research people needed.
I can tell you something like a fiber reinforced aluminum nitride ceramic is incredibly tough and will withstand an immense amount of heat. SiALON, silicone carbide fibers, Carbon 60, and the rest of that field is just getting going. In several millennia who knows what they'll come up with.
Powdered metallurgy is just now going into widespread use. These are much tougher than a random melt and pour.

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.

Ceramics can be cast in all sorts of shapes easily. I made molds for things like car turbocharger rotors and such. The oddest was for Ping Corporation, a golf club head. It is very easy to make a complex mold even today using multi-axis CNC machining centers.
If you had one that was like a 3D printer and could make something in ceramics it could be any shape imaginable.
Using something like a Hot Isotactic Press you can run the pressure easily to over 100,000 psi on something. That is a common method to make artificial diamond today. Installed several of those.

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.

Doesn't mean they are limited to the compounds and molecules we can make. If in the future they have come up with better ways to make stronger materials and can put those materials together with greater precision than we can they could have grossly increased their strength.

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.

Certainly, there will be differences in how different projectiles work against various materials. Kinetic energy is different from light energy, or chemical energy. So, there will be distinct differences in how different rounds work on a material.

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.

Given that one company I worked for (Keramont, now defunct) was making aluminum nitride armor for Apache helicopters and it would stop 23mm cannon rounds ceramics proved lighter and more resistive than steel in that case.

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.

Magnesium makes a great ceramic as MgO. That is what Ping wanted for their golf club heads. It has a slight orange color to it. Titanium carbide for example actually gets less friction as it increases in temperature. I had to make a test device to prove that.
The point is that even within the table there is lots of room for improvement. Look at Carbon 60 and nanotubes and such. Made the first reactor for that one at MER Corp for Dr. Wright of the University of Arizona.

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.

We can't say for sure what improvements would have occurred in the time frame given. But, it is certain that improvements would be made and that a bulkhead might well be 20 or 30 millimeters thick and stop far more than a low carbon steel one today would.
Composites and laminates might be a necessity. We can't be sure can we?

 

[Timerover51]

To each his or her own in his or her own Traveller universe.

As stated previously, I was attempting to make some sense with respect to Classic Traveller.

I have Striker since it was first release (and the box has the water damage to prove it), and have always had ZERO interest in it.

If you wish to have exotic materials which make invulnerable space ships, go ahead. I will not be using them.

 

[mike wightman]

Instead of looking at the properties of hardened steel for WW1/2 BBs try look into the properties of modern composites, ceramics and alloys which is what star ship hulls would be made of until they start using mass produced crystalliron at even higher TLs (according to Striker which is CT).
These are not exotic, they exist now. It's the manufacturing techniques that are exotic allowing for mass production.

The best way to find out what that stuff (crystalliron) would be like is to study the properties of modern superalloys used in turbines and imagine such materials being mass produced thanks to the advent of cheap fusion power making the extraction and purification of metals much cheaper, and the use of nano-scale manufacture in gravity controlled conditions.

 

[martletsquire]

I always thought that the Stryker rules compensated for the size of the starship when including the damage and penetration. Yeah, a starship may have thin walls, but there is so much space to shoot at in comparison to an AFV or IFV.

I mean, shoot at a Prius, vs shoot at a school bus. Statistically your chances of hitting something critical in a Prius are much higher than a school bus.

Also, IMTU, every ship is assumed to have some sort of spall liner/self seal system to stop micro and small macro penetrations. I mean, if they got them for fuel tanks, or space stations, you ought to have them in your starships. Discount deathtrap ships IMTU may do away with the spall liner and sealer, but then you get what you deserve.

 

[Carlobrand]

I always thought that the Stryker rules compensated for the size of the starship when including the damage and penetration. Yeah, a starship may have thin walls, but there is so much space to shoot at in comparison to an AFV or IFV.

I mean, shoot at a Prius, vs shoot at a school bus. Statistically your chances of hitting something critical in a Prius are much higher than a school bus. ...

To the best of my knowledge, Striker treats ships and small craft in the combat area the same as other vehicles. There are rules that let you translate the ship's armor into a Striker armor rating and that tell you what the ship's weapons will do, but it makes no allowance for the "so much space" bit.

This is actually a bit of a problem. Presumably, the typical gunner knows roughly where the engines are located and isn't going to waste his shots punching randomly into the body of a scout or free trader. On the other hand, the size DM is based on the dimensions of the entire ship - including the volume that is just cargo bay and staterooms. We are making the ship easier to hit and then confining the hit to key systems.

Then there's the damage problem: the same missile that hits in space, knocking out maybe a factor of drive or a weapon, is now capable of catastrophically destroying a ship or small craft and will do so about a third of the time. Lasers same. You could, in other words, utterly wreck a Broadsword with a single missile. One could argue that proximity made for increased precision, if that result had any chance at all of occurring in space. However, it doesn't occur in High Guard unless the target is facing a battery rating larger than the target's size rating.

Another issue is that the game discriminates between the "high" and "low" DM - you can decide to shoot the turret or the body of an AFV. You can presumably apply the rule similarly to a Scout/Courier, which has that single turret, and small craft are described as having integral weapons in High Guard rather than turrets, so those are treated as chassis-mounted. However, there's no real rule for what to do when you're faced with a Broadsword in the combat zone, with its 8 separate turrets. I'd treat each turret as a separate target, but it isn't specifically stated.

Introducing a ship typically requires some negotiation between players to come up with rules addressing their unique characteristics. One could deal with the damage problem, for example, by applying the ship's size factor as a negative DM to the vehicle penetration table, then rule that any hit that would have done damage if it had not been neutralized by the size DM will instead become a fuel hit, causing the loss of 1% or 10 dTons of fuel.