The problem with small pressure vessels is CO₂ toxicity. You can have all the oxygen in the world, but once the CO₂ gets above 1 percent, you’ll start to get drowsy. At 2 percent, it’s like being drunk. At 5 percent, it’s hard to stay conscious. Eight percent will eventually kill you. Staying alive isn’t about oxygen, it’s about getting rid of CO₂.

That means I need the regulator. But I don’t need the oxygenator all the time. I just need to get CO₂ out of the air and back-fill with oxygen. I have 50 liters of liquid oxygen in two 25-liter tanks here in the Hab. That’s 50,000 liters in gaseous form, enough to last 85 days. Not enough to see me through to rescue, but a hell of a lot.

The regulator can separate the CO₂ and store it in a tank, and it can add oxygen to my air from my oxygen tanks as needed. When I run low on oxygen, I can camp out for a day and use all my power to run the oxygenator on the stored CO₂. That way, the oxygenator’s power consumption doesn’t eat up my driving juice.

So I’ll run the regulator all the time, but only run the oxygenator on days I dedicate to using it.

Now, on to the next problem. After the regulator freezes the CO₂ out, the oxygen and nitrogen are still gasses, but they’re −75°C. If the regulator fed that back to my air without reheating it, I’d be a Popsicle within hours. Most of the regulator’s power goes to heating the return air so that doesn’t happen.

But I have a better way to heat it up. Something NASA wouldn’t consider on their most homicidal day.

The RTG!

Yes, the RTG. You may remember it from my exciting trip to Pathfinder. A lovely lump of plutonium so radioactive it gives off 1500 watts of heat, which it uses to harvest 100 watts of electricity. So what happens to the other 1400 watts? It gets radiated out as heat.

On the trip to Pathfinder, I had to actually remove insulation from the rover to vent excess heat from the damn thing. I’ll be taping that back in place because I’ll need that heat to warm up the return air from the regulator.

I ran the numbers. The regulator uses 790 watts to constantly reheat air. The RTG’s 1400 watts is more than equal to the task, as well as keeping the rover a reasonable temperature.

To test, I shut down the heaters in the regulator and noted its power consumption. After a few minutes, I turned them right back on again. Jesus Christ that return air was cold. But I got the data I wanted.

With heating, the regulator needs 21.5 pirate-ninjas. Without it… (drumroll) 1 pirate-ninja. That’s right, almost all of the power was going to heat.

As with most of life’s problems, this one can be solved by a box of pure radiation.

I spent the rest of the day double-checking my numbers and running more tests. It all checks out. I can do this.