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This week I want to explore Spaceships, in what may be the furthest divergence from Fantasy settings with thick stone walls and heavy Oak doors, Spaceships and Aircraft put a premium on the weight of materials used in their construction.

The first example I found is a module on the International space station with two Aluminum walls 2 and 3 millimeters thick. In Terms of an OGL game Aluminum has a Hardness of 6 and 10 hit points per inch, at 25 millimeters per inch lets say that each wall has 1 hit point. This means that the average damage from a 9mm pistol would penetrate the first wall easily.

A one square centimeter hole would reduce the pressure of a 10 cubic meter space to half normal pressure in about 6 minutes. 10 cubic meters is 353 cubic feet. Assume a hallway section is 10 feet wide, twenty feet long and ten feet high, that is 2000 cubic feet. Divided by 353 that's 5.66 or 34 minutes to half pressure.

If some idiot shoots a 10 round burst into the room it becomes 3.4 minutes, or 34 rounds, that still seems like plenty of time to put on a breathing mask and patch all the holes.

Now if the 4 player party faces off with 4 NPCS and the NPCs are using Automatic Weapons, half the rounds hit and half go into the walls, the PCs are using Semi Auto weapons and half their rounds miss, we have 22 holes in the walls, for 15 rounds to half atmospheric pressure. If everybody is behind cover and everybody misses it is 7 rounds.

If one of the NPCs throws a 4d6 Fragmentation Grenade, the average damage of 14 points blows through the Inner Pressurized wall and Outer Unpressurized wall and opens all 8 squares into Deep Space. One can assume superstructure that holds various compartments together, but the thin Aluminum walls are just confetti at this point there is no atmospheric pressure where the hallway was and the rest of the ship or station is losing atmosphere through the hatchways at the ends of the hallway.

In early playtesting for Galaxy Pirates I lent a copy of the rules to a friend of mine who wasn't involved in the early playtesting and didn't know any of the previous playtesters. I don't know how much he'd ever used D20 Modern or D20 Future and right away he thought there was a problem with the power level of the game. At that point the game was a copy of the D20 Modern SRD including Future with some Pathfinder rules changes. He had some players encounter a Security Guard who was armed with a Light pistol, he shot and Critically injured the team's Medic in the first shot.the other characters followed similarly.

At first I was incredulous that this was exactly what D20 Modern did and it wasn't really my fault.

However it is supposed to be my game and I looked at the Paizo Monster Creation chart and a CR 1/2 that most low level Characters encounter should do 4 points of Damage on average with their Highest damaging attack or some combination of lower powered attacks. A CR 1 should do about 7 on average with their highest damage attack or some combination. Therefore a 2D6 Pistol isn't really an appropriate weapon for a an encounter for first level characters. There was a 2D4 pistol they could use, there are 1d2 Pellet Pistols in D20 Modern somewhere. I don't think some kind of Air rifle for varmint hunting would be totally out of place among space colonists.

When Paizo released their Iron Gods Adventure Path they also released their Technology Guide and it included many 1d6 to 1d8 Energy weapons. At the time I was wrangling with the idea of bringing down the power level and coming up with a reason why.

Lets go back to our Tissue paper space station for a minute, for every hit point I want to add to the walls, or extra wall I would add to the Wipple shield to get another 6 Hardness I would add 50% to the Aluminum weight of my spaceship. Modern Commercial Aircraft are 80% Aluminum by weight, the ISS is 925,000 pounds so 740,000 pounds aluminum and adding 50% to that would be 370,000 pounds or another 40% to the overall spacecraft weight.

Now we can say this is the future and space travel is cheaper and costs to lift things into orbit become cheaper so they could thicken the walls, well they could. In order to ensure a 9mm round (12 HP max) doesn't penetrate we'd need 6 more hit points on the Pressurized Hull so 6 * 2.5mm or 15mm thickness basically 5 times what we already have in the primary wall.

The 14 Hit Points on average from our Frag Grenade still shreds the pressure wall and our ship now weighs 1,850,000 pounds more than it used to, tripling the initial weight of the spacecraft. The max damage on our Frag Grenade is 24 hit points and

1 half inch or 12.5mm of Iron, Hardness 10 and 15 Hit Points would stop the Frag Grenade. Iron (Stainless Steel 7.5 kg/m3) weighs 2.7 times as much as Aluminum. Initial Thickness 5mm * 2.5 to 12.5mm and weight 1,850,000 times 2.7 equals 4,995,000 pounds. So 5.4 times what our ship used to weigh just for the half inch Steel walls.

Suffice it to say sane people don't want you using Guns on their ships and Grenades and other Explosives are right out. They might allow Gas Grenades and other Non-Lethal weapons onboard, anything else would have to be locked in the ship's vault or Armory.

Now, from all the D20 sources I could find that you might actually use on a spacecraft we have;

Mysterious Alloy, Aluminum, Bulletproof Glass, Chitin, Iron (Steel Alloys), Glass, Plastic, Wood, Polymeric (Carbon fiber), Vanadium, Cerametal, my game won't support Neutronite (5x heavy as Lead) or Nanofluidic which is a Nanite gel sandwiched between layers of Neutronite. I don't like how Alloy is supposed to be the Lightweight material while being the same weight as Vanadium, but Alloy carries the same Speed penalty as Neutronite a much heavier armor? Vanadium has no speed penalty. So we're going to work through that.

An average person breathes 388 cubic feet of air per day, the standard 5x5 square 10 feet high that we assume from a lot of gaming miniatures maps is 250 cubic feet or less than a day's worth of air.

Some athletes are more efficient at their Oxygen consumption and a person that increases their activity will go through Oxygen faster as a person who slows their metabolism will go through Oxygen slower. We'll handwave that to the game effects of having better Constitution scores. Also a person's body displaces a certain amount of air, but I am going to ignore that to establish a baseline of how much Oxygen is in a 5 ft square and how long that Oxygen will allow a Medium sized creature to breathe.

Paul

Designer at Evilrobotgames.com