Very low Earth and Mars orbits contain atoms of oxygen that deteriorate spacecraft surface via chemical reactions, especially when combined with ultraviolet radiation from the Sun. Most modern coating need extremely long exposure before the damage is visible, but some materials such as carbon or silver erode as fast at 1/3 inch per year. The GM can overlook this effect unless for wrecks, from which it should be difficult to salvage delicate equipment. If the players are stubborn (or broke) enough to not fix a damaged hull and keep working in LEO, leaving fragile material exposed to erosion, 1 cDAM should be added to a damaged hull every month spent below 400 miles altitude above Earth or 800 miles above Mars.
Space is filled with meteoroids and debris that can be lethal to a light-armored spacecraft. In deep space and near most planets, the density is negligible, but it becomes significantly higher in Low Earth Orbit. The most dangerous orbit is LEO (below 1240 miles), in particular above 300 miles where debris do not decay quickly.
In these orbits, each ksf of hull is hit by a sizable object about once a year (individuals are assumed to have a 0.02 ksf area). Impacts on hulls are often at large angles and do not create serious threats and these minor damages are assumed to be repaired during maintenance time. For people in vacc suits and for small spacecraft, the damage is 3d6 × 5 (divide per 100 to have cDAM). Space walk in LEO is avoided but accidents do happen once in a while (every 50 man-year spent in space).
Each 10 ksf of hull is also hit every year by objects with sufficient energy to make 1d6 cDAM. For example, for every year spent in LEO, a 16 ksf Pegasus-Class (p. TS192) is hit 16 times in average by small debris and 1.6 times, or once or twice by a damaging object.
Any pressure below 15% of Earth's is considered as vacuum, with the effect described p. TS57. Below 50%, with a normal ratio of oxygen (21% of 50%, i.e. 10%), quadruple Fatigue costs; and Fatigue drops by 1 point for every 5 min of any exertion. Below 70% (14% of oxygen), double Fatigue costs. If the character has an Andraste biomod or breathing equipment, the effect at 70 and 50% are ignored, but not those below 15%.
A spacecraft is assumed to be punctured when it has internal Major Damage (see p. TS203, excluding knocked out sensors). If a habitat module is hit in combat (which can happen in case of occupant injury), an air leak is assumed to be created through a 1" × 1" puncture. The pressure in a 1-space module then falls to 70% of normal in 40 seconds, to 50% in 80 s and to 15% in 4 minutes. These values scale with the volume of the module and the area of the hole: a 1" × 1" puncture in a 2-space module causes the pressure to fall to 15% in 8 minutes, while a 2" × 2" hole (4 times the area) in this module causes it to fall in 2 minutes. Each module on a spacecraft is independently sealed (though it can always be opened manually). Occupants of a Shelter can not be injured unless the spacecraft becomes disabled in the same turn, then the Shelter is assumed to be breached (which does not affect the radiation protection).
Vacc suit helmets can decompress rapidly: with a 1/2" × 1/2" hole, the pressure falls to 50% in 1 s and to 15% in 3 s. For a crack, or if the spaceman tries to plug the leak with his hand, the decompression will take 10 times longer.
A vacuum creates ebullism, or creation of water vapor in the soft tissues, making them swell. Modern spacesuits are self-repairing pressure suits that reduce greatly this effect anywhere but for the head. A hole in a vacc suit makes the underlying skin to swell and become numb. If a entire piece such as a glove is taken off, the character will lose sensitivity in seconds and his hand will become swollen, painful and useless, loosing 1 HP per 15 minutes of exposure. However, unless the HP loss damages seriously the limb, the ability to use the limb is recovered in 15 minutes once back to normal pressure.
Once in vacuum, an unprotected body at Earth distance or closer to the Sun never freezes in sunlight. If not in sunlight, or if it is further from the Sun, it starts freezing in a few hours and turns solid to the bone in a day. In an insulated spacesuit, even if the air has escaped, the heat is kept inside very effectively, though the body is protected from sunlight. In this case it can take three days or more before a body shows frostbites, and two weeks before it freezes solid. While freezing, the body also dries as the water quickly evaporates. The cold and the absence of oxygen and water or external agents (insects) does not allow the body to decay, it rather tends to mummify. After the body has frozen solid, it becomes very difficult for a forensic expert to estimate how long the person has been dead without looking at the state of the suit (micrometeoroid impacts, effects of radiations, etc.).
Nemtos