The Martian

All told, the Big Three need 69.2pn, most of that going to the Oxygenator and Atmospheric Regulator. (The Water Reclaimer only needs 3.6 of that.)

There'll be cutbacks.

The easiest one is the Water Reclaimer. I have 620L of water (I had a lot more before the Hab blew up). I only need three liters of water per sol, so my supply will last 206 sols. There's only 100 sols after I leave and before I'm picked up (or die in the attempt).

Conclusion: I don't need the Water Reclaimer at all. I'll drink as needed, and dump my waste outdoors. Yeah, that's right Mars, I'm gonna piss and shit on you. That's what you get for trying to kill me all the time.

There. I saved myself 3.6 pirate-ninjas.

LOG ENTRY: SOL 198

I've had a breakthrough with the Oxygenator!

I spent most of the day looking at the specs. It heats CO2 to 900C, then passes it over a zirconia electrolysis cell to yank the carbon atoms off. Heating the gas is what takes most of the energy. Why is that important? Because I'm just one guy and the Oxygenator was made for six. 1/6th the quantity of CO2 means 1/6th the energy to heat it.

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 -150C to 0C. 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 -75C. 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.

I had to guess at the weight. The heaviest thing I'll bring with me is the water. 620kg worth. My freeze-dried potatoes will add another 200kg. I'll probably have more solar cells than before, and maybe a battery from the Hab. Plus the Atmospheric Regulator and Oxygenator, of course. Rather than weigh all that shit, I took a guess and called it 1200kg.

Half a cubic meter of basalt weighs about that much (more or less). After two hours of brutal labor, during which I whined a lot, I got it all loaded in.

Then, with both batteries fully charged, I drove circles around the Hab until I drained them both.

With a blistering top speed of 25kph, it's not an action-packed thrill ride. But I was impressed it could maintain that speed with all the extra weight. The rover has spectacular torque.

But physical law is a pushy little shit, and it exacted revenge for the additional weight. I only got 57km before I was out of juice.

That was 57km on level ground, without having to power the regulator (which won't take much with the heater off). Call it 50km per day to be safe. At that rate it would take 65 days to get to Schiaparelli. But that's just the travel time.