Homebrew Star Wars D6 - Exposure to Vacuum Rules

[Celebrim]

So, perhaps not surprisingly, since Star Wars generally seems to occur in a universe where outer space has air and gravity, there has been very little mention of exposure to a vacuum in published Star Wars material. But I play a bit grittier of a Star Wars game than most, and while I've played like 70 sessions of the current campaign without having to worry particularly about the problem of being in a vacuum, that is going to change in the next adventure. A quick perusal of the internet and published materials doesn't find this most basic of space hazards covered.

So, now I need to cover it.

How would you handle exposure to a vacuum using the D6 rules?

In general, I have the following first instincts:

1) Damage from a vacuum should be resisted by Survival or Stamina.
2) Base difficulty of resisting damage should increase with length of exposure. So maybe 1 round is easy, the 2nd round is moderate, and so forth.
3) Damage should be linear. No "instant death" from vacuum exposure, you just slide down the wound track at a steady pace.
4) The worst possible result should be "mortally wounded". Vacuum exposure doesn't kill, but can put you in a dying state where you will die shortly and by that point you need major medical intervention like a Baatha Tank
5) You don't tank vacuum damage if you are protected from it fully (you have an enclosed environmental suit). You get a bonus to resist vacuum damage if you are partially protected from it such as wearing a compromised suit. The bonus goes down the worse the suit is compromised, down to zero.

I have the following problems:

1) Which is more reasonable, survival or stamina?
2) I don't like that the difficult is entirely independent. If I go with Stamina, is it entirely reasonable that a Wookie on average survives longer in a vacuum than a human? If I go with Survival, is it entirely reasonable that the smart guy survives longer in a vacuum than the dumb guy? I can't think of a better rule though.
5) How do we resolve whether a suit or armor is compromised by an attack? And to what degree? And how much bonus should a compromised suit provide. Remember that a bonus just on average increases the number of rounds before you succumb, because of #2 the difficulty will eventually always increase past your ability to endure even with a leaking suit. Of course, this may give you time to make an Armor Repair role to patch the damage, difficulty depending on how compromised the suit/armor is.

Any thoughts by anyone on the subject or any house rules that you've used in the past so I can compare approaches would be appreciated.

 

[Mustrum_Ridcully]

I don't really know enough about Star Wars d6 to give any specific rules advice. Are you required to decide which skill to use? Maybe the player simply uses the better one - the smart guy is doing stuff to help his body deal with the vacuum better, the Wookie just has better endurance?

Exposure on your outer body (skin):
Your skin and muscle tissue holds you together for a while, so your blood is in a closed system and not instantly boiling or anything, but gas and fluids still will slowly evaporate, leading to swellings, your skin (or eyes, if they are exposed) would become dry.
But if you're only exposed partially, it might really take some time before it can kill you, though affected limbs might become difficult to use.

Partial Exposure
I think that part is mostly Endurance, unless you do something to protect the exposed part, where the Survival skill might work better. So maybe you can spend actions to get an Survival skill check to improve your odds of success?
Less exposure to vacuum probably means you can last longer, so either the DC is lower or your need to check later and less often?

Lungs in Vacuum
Then, if you don't have a helmet protecting your head or something similar protecting your breathing apparatus, you naturally have a big problem breathing. The lack of outside pressure would cause air to rapidly expand and escape your body - don't hold your breath, it will rupture your lungs. Knowing that might perhaps give you some valuable extra seconds of conciousness. But eventually, you fall unconciousness (~15 seconds), and then it's really just a question of how long your body or brain can survive without oxygen, and that is probably a function of the Endurance skill (90-150 seconds?).
So Survival for managing the loss of breathable air and give you a bit of extra conciousness, and Endurance for time to death/dying.

 

[JiffyPopTart]

I'm almost positive that the Survival skill was used for survival in a vacuum in the RAW. I definitely remember making a skill check for that rarely used skill when ejecting from an X-Wing.

 

[aramis erak]

I don't really know enough about Star Wars d6 to give any specific rules advice. Are you required to decide which skill to use? Maybe the player simply uses the better one - the smart guy is doing stuff to help his body deal with the vacuum better, the Wookie just has better endurance?

Exposure on your outer body (skin):
Your skin and muscle tissue holds you together for a while, so your blood is in a closed system and not instantly boiling or anything, but gas and fluids still will slowly evaporate, leading to swellings, your skin (or eyes, if they are exposed) would become dry.
But if you're only exposed partially, it might really take some time before it can kill you, though affected limbs might become difficult to use.

Joe Kittinger proved (unintentionally) that vacuum exposure doesn't lose much water - but his hand ballooned to uselessness - and he wasn't even jumping from hard vacuum. It's said his hand ballooned to double thickness. (Excelsior III: August 16, 1960, 102,800 feet/31,300m - one third of the way to the karman line and "true vacuum"... an estimate of 0.0075 bar. Surface sea level is typically 1.013 bar. (1 bar is roughly 1 atmosphere at 111m above sea level.) By the way, Mars runs 0.005 to 0.015 Bar at surface depending upon weather and time of day... So Joe was essentially jumping from Martian atmosphere levels.

On a more exposed body, you can figure expanding the body volume by 1 to 2 cm in all directions. A typical male adult is about 1.9m² surface area, so 1 cm would add about 0.019m³, or 19 liters; the belly is likely to add another 2 liters, but that's mostly going to be gas inside the gut. That's fatal level expansion from blood density decrease, as normal blood volume is 5 to 6 liters, and that's more than triple. (3-4 liters loss is usually fatal; sending it through much more volume is much the same as losing it.)
Useful consciousness then is based upon extant brain oxygenation, so 30 seconds or so.

So realistically, Stamina checks starting round of exposure to remain conscious: TN is 3 for a hand, 5 for an arm or leg or the head, 10 for torso, and 5 per round after first (3 per round if doing nothing), fail and lose useful consciousness. Further, anything bigger than a hand or foot, general 1d penalty; any exposed location used is an additional 1d penalty.


See Joseph Kittinger - Wikipedia (more correctly, follow the sources therein) for good info. The specific incident was on the

 

[Celebrim]

I'm almost positive that the Survival skill was used for survival in a vacuum in the RAW. I definitely remember making a skill check for that rarely used skill when ejecting from an X-Wing.

Survival is used in the RAW to see if you can successfully eject from an exploding vehicle. So that's what you remember. It's used significantly more commonly depending on how you play. I've avoided desert planets so far, out of a feeling Tatooine and Tatooine like planets are overexposed, but I have had several icy and jungle planets and one swamp planet orbiting a Class F blue giant where daytime brightness was an order of magnitude higher than on the earth, and unprotected eyes would be blinded in seconds, and this is the second adventure that has involved derelict or damaged space structures where the PCs are in a vacuum. So we've had our share of survival rolls. The reason for the particular interest in vacuum exposure is the PC are fighting these spider monsters in a vacuum that have knives for legs, so when they get hit their pressure suits get compromised.