The Martian

The spec said 44.1pn, but all this time it’s only been using 7.35 because of the reduced load. Now we’re getting somewhere!

Then there’s the matter of the Atmospheric Regulator. The regulator samples the air, figures out what’s wrong with it, and corrects the problem. Too much CO₂? Take it out. Not enough O₂? Add some. Without it, the Oxygenator is worthless. The CO₂ needs to be separated in order to be processed.

The regulator analyzes the air with spectroscopy, then separates the gasses by supercooling them. Different elements turn to liquid at different temperatures. On Earth, supercooling this much air would take ridiculous amounts of energy. But (as I’m acutely aware) this isn’t Earth.

Supercooling is done by pumping air to a component outside the Hab. The air quickly cools to the outdoor temperature, which ranges from -150°C to 0°C. When it’s warm, additional refrigeration is used, but cold days can turn air to liquid for free. The real energy cost comes from heating it back up. If it came back to the Hab unheated, I’d freeze to death.

“But wait!” You’re thinking, “Mars’s atmosphere isn’t liquid. Why does the Hab’s air condense?”

The Hab’s atmosphere is 90 times as dense, so it turns to liquid at much higher temperatures. The regulator gets the best of both worlds. Literally. Side note: Mars’s atmosphere does condense at the poles. In fact, it solidifies into dry ice.

Problem: the regulator takes 21.5pn. Even adding some of the Hab’s power cells would barely power the regulator for a sol, let alone have juice to drive.

More thinking is required.

LOG ENTRY: SOL 199

I’ve got it. I know how to power the Oxygenator and Atmospheric Regulator.

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% you’ll start to get drowsy. At 2% it’s like being drunk. At 5%, it’s hard to stay conscious. 8% will eventually kill you. Keeping alive isn’t about oxygen, it’s about getting rid of CO₂.

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 25L tanks here in the Hab. That’s 50,000L 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, adding oxygen to my air as needed. When I run low on oxygen, I can camp out for a day and use all my power to run the Oxygenator. 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.

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 100W of electricity. So what happens to the other 1400W? 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 ran the numbers. The regulator uses 790W to constantly reheat air. The RTG’s 1400W 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 21.5pn. Without it… (drum roll) 1pn. 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.

LOG ENTRY: SOL 200

I hauled rocks today.

I needed to know what kind of power efficiency the rover/trailer will get. On the way to Pathfinder, I got 80km from 18kwh. This time, the load will be a lot heavier. I’ll be towing the trailer and all the other shit.

I backed the rover up to the trailer and attached the tow clamps. Easy enough.

The trailer has been depressurized for some time now (there’s a couple of hundred little holes in it, after all), so I opened both airlock doors to have a straight shot at the interior. Then I threw a bunch of rocks in.