Some subsystems have a small "head" icon above their power levels. These systems are:
- Piloting
- Shields
- Weapons
- Engines
By staffing these systems with a crew member, you increase the abilities of that system. When you send a crew member into an unstaffed room, you can see them head straight for the console and start working there.
From my observations:
- Staffing the Cockpit and the Engine Room increases your chance to dodge.
- The Engine Room also has the added benefit of reducing FTL charge time when staffed.
- Please note that staffing the Cockpit is required for almost everything; the engines won't recharge even if someone is manning the Engine Room. Your dodge chance also goes to 0% if no one is trying to pilot the ship; it's an inert hunk of metal.
- Staffing the Shield System results in shields recharging faster.
- Staffing the Weapons System results in your weapons charging faster.
- Staffing the Door Control System results in your doors upgrading a level.
- Staffing the Sensor Control System results in your sensors also upgrading a level.
The amount of the benefit you receive is based on the crew member's system skill level, which you can see by going to Ship --> Crew, and hovering over the crew member. They will gain experience by working on the system, increasing the bonus they provide to the relevant system. You can occasionally see your crew gain experience by seeing yellow icons appear above them. These icons will match the system they are currently working on.
Note that it doesn't seem like crew gain experience when the ship is not in danger, so staying in a system doing nothing is unlikely to help your crew gain experience.
The exception to this, as @Halfwarr noted, is asteroid fields. Since your ship is continually in danger and the asteroid damage can be mitigated, this is probably an excellent way to gain skill. This is no longer valid with the full release.
Also, there is only a single console per system, no multiple crew members do not provide any bonus beyond faster repair speed in the event the system becomes damaged. This is easily testable by sending another crew member to the cockpit; the first one will provide a bonus to dodging when he reaches the console. The second will not increase your ability to dodge.
I have not unlocked all ships, however, so it may be possible that some of the later ships have multiple consoles for some or all systems, in which case, multiple crew members would provide a greater bonus.
Breach bombs damage systems and crew, and cause cracks, but don't hurt hulls. Alternate bombing the medical bay and the O2 generator. Put priority on whichever one the crew is trying to repair. Eventually they'll have so little health they won't try to repair things, and you can just wait. If the ship doesn't have a medical bay it's even easier - just bomb the O2 generator until they stop trying to repair it.
If you're taking this tack, it helps to upgrade your own shields (and maybe have a defense drone) so you can sit and wait them out without having to waste missiles bombing their weapons as well.
Ion weapons can help, but it's hard to get enough of them to punch through 3-4 shields reliably, while you are still getting shot at. If you have them, great, but don't prioritize them.
You are correct about sensors. Don't even bother trying to kill crew without damaging the ship until you have the first sensor upgrade or a slug crew member.
Best Answer
TL;DR. --> No. The rate is fixed.
For Science! --> I ran a series of tests, each iteration tracking the amount of time necessary to go from 100% oxygen to 25% oxygen with all internal doors open. I stopped here to avoid damaging my crew's health and thereby requiring time in sickbay before the next iteration began.
Results were as follows:
As you can see, from one crew to four the oxygen depletion rate remains constant. The rate is also not affected by Mantis or Zoltan biological distinctiveness.
Thus, one must recommend the immediate cessation of emergency crew execution measures intending to reduce oxygen depletion as this approach is demonstrably ineffective.