Life support is something that is often mentioned in Star Trek, but not really detailed beyond some vague technobabble or through implying that things are ‘bad’ without it. Off-screen, the Next Generation Technical Manual goes into more detail (see pgs 142-146), talking about atmospheric processing, gravity generation, waste management, and emergency environmental systems.
The amount of detail is great. For a Galaxy-class starship, the information found in the book is almost required reading if you really want to get into the nuts and bolts of starships of the class. One quote from this book stands out to me when reading it, “Believability (not to mention crew safety) demands that the [life support] be extremely reliable…”.
This is needed for a television series where budgets are constrained. But in your game, the FX and locations are limited only by imagination. So let’s expand on what’s found in the Technical Manual and see what we can find to add to your games!
Any attempt to calculate the way a starship generates oxygen and scrubs out CO2 using the photosynthetic processing units isn’t really easy, nor should modern values for production of oxygen through algae be assumed.
It is very possible that through selective breeding or even genetic tinkering with algae that the United Earth and later the Federation have used single-celled organisms from hundreds of worlds to breed algae capable of producing as much breathable air as needed for a starship with huge redundancy. These huge vats or tanks would have vast amounts of water containing photosynthetic single celled organisms—CO2 from the atmosphere bubbling through the water, bright synthetic sunlight blasting down. Additionally, these tanks would probably have feed lines from solid and liquid waste treatment in order for trace minerals to be injected into the water to allow for better reproduction rates from the algae. In a pinch, these same vats could be used as emergency water sources, very unpalatable food substitute, or as a major plot device for your game.
Any system designed to allow single-celled organisms to thrive means there is a chance for unwanted organisms to get inside and wreak havoc. Perhaps an airborne bacteria or virus enters through the CO2 bubblers and begins to kill off or totally out-reproduce the good algae. These tanks could also be a place where multi-celled organisms might grow and breed out of the view of the crew, bursting forth when they are mature or too numerous to stop. Tanks of corrupted water, stagnant with dead algae and containing, let’s say Arcadian Yeast, may make for an interesting new IPA but won’t make for good air to breathe.
When a starship is in deep space, losing your primary way of breathing may mean your first priority is to start searching for strange new worlds that might have algae that seems to work. But will it? There are a lot of story possibilities to be had just with that idea.
Likely, there are secondary systems for air production—a reserve system that operates, we assume, much the same way as the others. Any problem affecting the algae in the primary system may well cause problems in the secondary. Finally, it’s logical that there are emergency atmospheric supplies. Think oxygen tanks and square CO2 scrubbers in shuttlecraft. I’m sure such standardization is fully implemented in Starfleet of the mid-22nd century.
What other ways are there to make oxygen? There is always the electrolysis of water into oxygen and hydrogen. Unless you’re careful to separate the hydrogen and oxygen from each other, certain impressive exothermic reactions can occur.
There’s another way, but your chief engineer may not like it as it’s very power intensive: replicators. A replicator could be set up to just spit out a breathable atmospheric mix and another replicator set up to dematerialize CO2. Energy intensive is putting it lightly, and such a system couldn’t sustain a full starship, but it very well could provide enough ‘breathing room’ for a team of engineers to fix a problem with the primary systems while the rest of the crew takes shore leave on a sandy beach on the planet below. Just assume that the replicators used this way are probably going to be wrecked quickly from the constant usage and will need to be replaced.
The replicator isn’t something that’s going to be around much in the TOS or Movie era, let alone earlier, but there has to be other ways to make oxygen for all those pesky crew members. Of course there is, and hopefully your starship has a chemist on board willing to do some really dangerous things to make small amounts of oxygen.
On modern commercial airliners the oxygen masks that drop in case of an emergency aren’t hooked up to compressed oxygen cylinders. In fact, they make oxygen through an exothermic reaction (one that generates heat) with sodium chlorate (highly toxic to humans) barium peroxide and potassium perchlorate (both oxidizers that can be used in explosives).
All of these materials would probably be already present in small amounts in emergency packs in a starship, but in large enough quantities to generate breathable atmosphere for a few dozen crew or more. And the amount of heat generated from such a reaction would be problematic to say the least.
The air the crew breathes is something that many people take for granted. Writing a story around the fact that your starship is surrounded by light-years of nothing and you’ve only got what’s stuck inside your little metal shell is something that could make for an interesting set of events.