[Spaceships] Armor Density
 

So I've been debating whether these two house rules were too complicated, since they require logarithms, cube roots, and all kinds of other nasty things. So I started simplifying the math. It now features only multiplication, addition, and comparing to a chart. It can be done on a $1 calculator, or very quickly on paper.

And what's best of all: the results are perfectly identical.

First of all, some quick terminology: Heavy armor means steel, iron, or orichalcum. Light armor means ice, wood, or etherwood. Medium armor means pretty much all other armors. Roomy systems are those that have substantial empty spaces, such as habitats and hangar bays, while extremely roomy systems are those that are almost entirely empty space, such as open spaces. If using the smaller subsystems rule, treat a smaller system as 1/3 or 1/2 of a system.

Get the secret number by adding 9 times the number of heavy armor systems and 7 times the number of medium armor systems, then subtract 10 times the number of roomy systems and 30 times the number of extremely roomy systems. Remember this number: You'll need it later.

A lot of armor makes a ship smaller, increasing armor thickness

Look up the secret number on the chart below. If it falls between two rows, use the row above. The result is the multiplier to all dDR (including that of light armor, even though it doesn't contribute to the secret number).

A lot of armor makes a ship smaller, decreasing target area

As before, look up the secret number on the table below, using the row above if you fall between. The result is the reduction of SM for combat purposes.

Special case: Exotic materials

Exotic laminate can be any of a number of different hypothetical ways of making super tough materials. Depending on the exact technology in the setting, this could be a light, medium, or heavy armor, or an even more dense super-heavy armor. If the latter, multiply the number of subsystems by some higher number when calculating the secret number. 9.5 would be as dense as lead, 10 would be as dense as gold or osmium, and 10.5 is exotic collapsed matter of effectively infinite density.

Re: [Spaceships] Armor Density
 

I thought about doing the volume thing. Gave everything a volume rating and compared bulk cargo ships to 70% armour combat ship. Decided it wasn't worth all the extra work - they still fitted into their SM class:( It did, however, give data for floorplans.
Hadn't thought about increasing armour. Guess it'd work in reverse too for high-volume systems (habitat).
re table. Using only dense armour, 20x9 = 180. Any reason it goes over 180?

Re: [Spaceships] Armor Density
 

An even easier method: just have armor not take up any component space at all (i.e. you can have 20 modules, plus armor); instead, if you have more than 20 total modules in a ship, multiply acceleration, delta-V, and jump capability by 20/(# of modules).

Re: [Spaceships] Armor Density
 

Part of the problem with any system that adds volume detail to Spaceships is that the systems already have vastly different volumes.

When I first got Spaceships, I tried it out with a handful of designs; among them were a fire support drone and a diplomatic shuttle, both with the same mass(same Spaceships SM). I then tried comparing those Spaceships designs to equivalent VE designs, and they differed in volume by more than an order of magnitude(with corresponding difference in SM).

Which totally makes sense, but it's all ignored by Spaceships. And I do mean ignored, not just abstracted — rolls to hit that drone and shuttle take the same SM modifier, despite the shuttle being a larger target.



Now, a system/list for assigning densities to systems, and a system for adjusting SM based on density, might be neat, and would support this sort of thing. It just has to first determine that 5 tons of armor is thinner on the shuttle than on the drone.

Re: [Spaceships] Armor Density
 

That doesn't make sense, as modules are based on mass, not volume. Armor definitely takes up mass. Using your suggestion, cargo bays would be free, not armor.

Re: [Spaceships] Armor Density
 

If you have an exotic armor that is denser than steel, you can use a higher multiplier than 9. Look at the special case note at the end.

Re: [Spaceships] Armor Density
 

Oops - Reading failure LOL

Have you assigned density to other systems?
eg Habitat, hanger, cargo 0.25, electronics 0.5, powerplant 1, drives, 2...

Re: [Spaceships] Armor Density
 

As would, ahem, empty space. Also hangars and habitats would probably take up significantly less than one module as they're mostly "empty space."

Re: [Spaceships] Armor Density
 

Modules are based on both mass and volume -- the reason you can only fit X modules in a SM +Y hull is because of volume, not mass. The mass of the modules is handled by the change in performance.

Re: [Spaceships] Armor Density
 

No. I considered it, and might do it in the future. If I do, it's going to be only one or two non-standard multipliers. Maybe -5 for "roomy" systems and -10 for open spaces. That would mean sending the tables into the negative.

Re: [Spaceships] Armor Density
 

That doesn't sound like Spaceships, since it's always 20 systems regardless of SM.

Re: [Spaceships] Armor Density
 

I've added some modifications for lighter systems.

Re: [Spaceships] Armor Density
 

Nah, spaceships is just X=20.

Re: [Spaceships] Armor Density
 

No, that's not true. Each system is 5% of the ships total mass. It abstracts volume.
Emphasis from book.

Re: [Spaceships] Armor Density
 

All that needs to be done is take the extra systems and divide the speed by it. If the ship ends up being 30 modules then the speed will be X

X = (given speed from spaceships) / 30 times 20.

For low volume system like armor (and considering how coarse the spaceships systems are already) this works fine. (I also tend to ignore hits on extra armor systems in this case)

Ships still only get two core modules as well.

Re: [Spaceships] Armor Density
 

Anthony's method should work fine. The only reason ships are restricted to 20 locations is due to the effect ship mass has upon performance (which is mostly fixed adequately by modifying performance by the total number of systems used, except for fuel tanks, which would need to be reworked a bit more) and for reasons based upon volume. If you alter the ship performance based upon total number of modules, you've got a system that needs 20 systems for volume-based reasons (such as number of people that can fit in a hull section or the hit location rules), not mass.

You could expand it so that different systems took up different amounts of volume slots while taking up one mass slot. Armor modules would take up 1 mass slot and 0 volume slots, habitats might take up one mass slot and two volume slots, etc.

For fuel tanks, the fuel tank multiplier would need to be based upon the actual fraction of fuel tanks to total mass slots used. Everything else should work fine.

Re: [Spaceships] Armor Density
 

That way works, but is a completely different design system from Spaceships. It's similar to how it was done with the various 3e modular vehicle design systems. A hull of a given size has a given number of spaces, and you calculate mass and performance last.

The problem I see with this idea is one that haunted all of the 3e systems: It's difficult to build a vehicle with a target performance. Basing everything on same-mass modules means that each module give a certain performance (3G for an engine, 12 mps dV for a fuel tank), rather than having to calculate performance at the end.

Re: [Spaceships] Armor Density
 

Partitioning spaceships into a different number of systems breaks the Spaceships damage system.

Everything else you can work around if you're willing to do the math, but how do you deal with that?

Re: [Spaceships] Armor Density
 

This is true, but the fewer variants you have, the easier it is. If just armor has nonstandard volume, it's actually pretty easy to come up with target performance (adding fuel and habitat makes it messy rapidly).

Re: [Spaceships] Armor Density
 

By not assigning damage locations to extra armor?

Re: [Spaceships] Armor Density
 

Er...that may make something coherent, but only makes any sense once you completely discard the meaning of Systems in the Spaceships mechanics.

Re: [Spaceships] Armor Density
 

"Hits" on armor was kinda dodgy to begin with, ignoring it is a really good idea. Armor is something you penetrate in order to get to the important bits inside, only something like a matter disintigration beam should have any effect on armor - other then going through it or being stopped by it.

Re: [Spaceships] Armor Density
 

I think the volume of what is inside the armour is more important than the volume of armour - armour volume is just how thick the covering will be.

Using excel and VDS:
for a known dDR, you can get the thickness (2.75 pe mm for steel?)
for the weight of armour, you have a volume (density 7.9)
volume and thickness give you area of coverage, ie the surface area these ships are meant to have.
Assign volumes for all systems, and a hull design, and you get how far your armour has to spread.

Re: [Spaceships] Armor Density
 

I was working on a mass/shape modification for spaceships although I got sidetracked and haven't finished it.

Basically, I assigned a density modifier to various components based on the intitial Mass:SM ratio, which hovered around 0.3 Specific gravity... I then just used the Spaceships 3-10-30-100 mass progression to create a "Density Modifier".

• This worked out to -2 for Hydrogen tanks (Specific gravity less than 0.1)

• -1 for open areas and roomy habitats (Specific Gravity less than 0.3)

• +0 for normal habitats, organic/ice armors, and most components (Specific gravity less than 1)

• +1 for low-access components (penalty to Fire Control), Most fuel Tanks and low-density armors (specific gravity less than 3)

• +2 for clamps and high-density armors (Specific gravity less than 10)

• I do have a hardened High-Density Armor type (Irridum based alloy) in my
  campaign that earned a +3 density mofifier (Specific gravity less than 30)

Total it up, divide by 20, round towards zero, subtract it from SM.
This affects targeting and active sensors (not passive sensors).
It also affects armor value, add the density modifier to SM to determine dDR.

------------

I also came up with rules that modified front/center/rear profiles based on shape... as well as coolant issues based on shape. For instance a sphere gets -2 on all profiles but has a much bigger heat problem. The base-line assumption was a 3:1 rectangular/cylindical shape.

Hope that helps!

Re: [Spaceships] Armor Density
 

Nice one. Takes a lot of the maths out - very GURPSian.
Must try it for the designs I have.

Re: [Spaceships] Armor Density
 

As Anthony said, by not assigning armor to the damage system (as it should be). The damage system is based on the assumption that all systems have the same volume. If you use the assumption that armor takes up no volume (which is what this alternative system is based upon), then there's no problem.

Re: [Spaceships] Armor Density
 

Emphasis mine.

No, that's just not true. I've already quoted, from the book, where it specifically states that the systems do not take volume into account. The damage system only takes mass into account not volume.

If your new system doesn't take mass into account and only works on volume, then you'll be fine, but don't go saying that the original system takes volume into account when the book specifically states it does not.

There's no reason you couldn't build one based on Volume, however, you'd have to go back and figure out how large each system is, then rebuild the entire system by adding a mass component to keep track of, and you'd still be limited to 20 systems as each one would then be 5% of the total volume.

Re: [Spaceships] Armor Density
 

The damage system assumes equal hit probability on all components. That only makes sense if all components have equal volume (actually, equal exposed area). Basically, your quote, while accurate, is not true -- the actual behavior of Spaceships is inconsistent with the stated design.

Re: [Spaceships] Armor Density
 

So, what you're saying here is accurate...but the entire point of the design system is simplicity and fun, fast play.

It's explicitly said, and all performance is calculated, based on the assumption of 20 equal-mass slices.

The targeting probabilities is a side effect of wanting to use d6 dice mechanics, and was clearly done for ease of rules and play.

It's a mass-based system, with some kludges there for purposes of fun.

Re: [Spaceships] Armor Density
 

All performance and stats are calculated based on the assumption of 20 slices that are equal in both mass and volume. This is a simplifying assumption, but it results in significant implausible results in extreme cases. There are no ways to fix the anomalies without increasing complexity, but adding extra armor boxes that don't count against the limit of 20 is probably easier than recalculating DR and SM based on what modules the ship contains.

Re: [Spaceships] Armor Density
 

You keep stating this, but it was not David's intent. I was there for the writing AND the playtest, and you're just mistaken here.

The mass is an explicit calculation of equality. The volume is an admitted kludge for simplicity. Period.

Re: [Spaceships] Armor Density
 

So was I, and I'm not. The spaceships system is based on assuming that all ships of the same mass will have approximately the same volume.

Re: [Spaceships] Armor Density
 

Anthony's right. It's just an assumption that falls out of the math used in Spaceship's combat system. If you have an equal probability of hitting each of the systems (neglecting core), then they all have the same surface area exposed to be hit. Thus, the simplest assumption is that each segment not only has the same mass but also has the same volume.

Sure, it's a gamable abstraction, but what that abstraction ends up implying is that all systems have identical mass AND volume, even though you're only designing ships by looking at the mass.

Re: [Spaceships] Armor Density
 

Requoting from the book:

Mass, not volume. QED.

As I said, I agree that equal-surface area approximation seems logical due to the simplistic metagame desire to have a 1d6 roll for what section of hull is hit. However, it's explicitly a metagame and INCORRECT assumption based on the author's own statements.

You guys are taking literalism way too far.

Re: [Spaceships] Armor Density
 

The base Spaceships system ignores volume, true - but it does so by assuming every system has the same volume, and that's completely evident in the hit location rules (where systems have equal hit probability no matter if they're high-density armor or low-density hydrogen fuel tanks). It's an implicit assumption of the system, sure, but just because it's not explicit doesn't mean it isn't there.

You also seem to be forgetting that we're talking about an alternative design system here where differences in system volume are accounted for (at least in relation to armor). Nobody has been saying that the base system works by volume - just that it's relatively easy to rejigger the system so that it does account for volume as well as mass.

Re: [Spaceships] Armor Density
 

Exactly. It doesn't matter if the author says "I'm using normal arithmetic" and then proceeds to state that 1+1=3. He ain't using normal math. I understand that the hit location dealie is a gamable approximation. But the original point is that the hit location percentages are off using realistic densities for varying sections because all sections have the same probability of being hit.

The same mass of crew cabins and liquid hydrogen tankage will realistically have different volumes. But not according to the Spaceships hit location rules.

Re: [Spaceships] Armor Density
 

Also because DR doesn't vary with what modules you have.

Re: [Spaceships] Armor Density
 

No, they all have the same surface area in a given hull section. We aren't given anything to indicate that the front, center and rear sections actually divide the ship's volume or surface area up equally, but it will probably be close. We also don't have enough information about the core systems beyond the fact they are 5% mass.

In short, there isn't enough information provided to say anything about volume. However we can freely talk about surface area.

Re: [Spaceships] Armor Density
 

Well, if we make the assumption that ship designs are rational, surface area will range from 4.84 to maybe 8 times volume ^ 2/3. Also, we know that streamlined ships have a surface area penalty, since they have lower DR, so we should probably assume that surface area for unstreamlined ships is pretty close to the 6 * v^2/3 used by VE2.

Re: [Spaceships] Armor Density
 

Mass vs Volume?
[Spaceships] designer notes re volume:
I interpret the above information as "go with what suits your campaign".
For example: a SM +10 ship (10,000 ton) in my campaign, streamlined wedge with 15% armour mass would maybe have 7000 cubic meters volume (no I cannot handle imperial measurements). This is all too complex for me so irrespective of the mass of systems, I have given 10 kiloton streamlined ships:
Volume: 10,000 cubic meters.
Length: 200 m
Hight: 12.25 m
Surface Area: 5,050 square meters

Sure I have old battleships massing 1 megaton the size of large freighters (100 kilotons) kicking about. However as the Spaceships combat system is totally irrelevant to any hostile encounter involving players (poof; you're vapourised), why bother with the "reality" calculations?
Just because I like it.
Really want a copy of GURPS Vehicle Design!

Re: [Spaceships] Armor Density
 

No, he's not.

We have an equal probability of hitting something relevant in a given section. Sure, a cargo bay may take up 500%+ of the volume of a stardrive, but if you hit something in the much more compact stardrive it's likely to be relevant, where a lot of shots can pass through the cargo bay and hit nothing.

So, the game abstraction is simply that you have an equal change of hitting something relevant in large, relatively diffuse system, as you do in a compact, dense system.

It doesn't presume that they have identical volume. You're more likely to hit something vital in a compact system then you are in a larger one. Hence the identical chance for damage.

Re: [Spaceships] Armor Density
 

Each segment of the design has equal mass, but volume is a variable, as is surface area. The real numbers would be a pain to work out and not very gameable.
The surface areas for floorplans would suggest armour averages three times the density of non-armour segments, therefore, volume is not the same.

I like Trachmyr's idea (although, based on the surface area required for the given dDR for steel armour, I figure the relative density as 0.7).

Following on from that simple idea (modify SM for targeting and armour), Sphere's should have armour for +1SM. If all other shapes could be said to fall into a "ballpark" surface area; a sphere would fit the diamond:)
And something from old VDS: cheap armour is 1/2 price, -1 SM; Expensive +2cf, +1SM; Advanced +9cf, +2SM.