Chapter 18
Sigh…
Just once I’d like something to go as planned, ya know?
Mars keeps trying to kill me.
Well…Mars didn’t electrocute Pathfinder . So I’ll amend that:
Mars and my stupidity keep trying to kill me.
Okay, enough self-pity. I’m not doomed. Things will just be harder than planned. I have all I need to survive. And Hermes is still on the way.
I spelled out a Morse code message using rocks. “PF FRIED WITH 9 AMPS. DEAD FOREVER. PLAN UNCHANGED. WILL GET TO MAV.”
If I can get to the Ares 4 MAV, I’ll be set. But having lost contact with NASA, I have to design my own Great Martian Winnebago to get there.
For the time being, I’ve stopped all work on it. I don’t want to continue without a plan. I’m sure NASA had all kinds of ideas, but now I have to come up with one on my own.
As I mentioned, the Big Three (atmospheric regulator, oxygenator, and water reclaimer) are critical components.
I worked around them for my trip to Pathfinder .
I used CO 2 filters to regulate the atmosphere, and brought enough oxygen and water for the whole trip.
That won’t work this time. I need the Big Three.
Problem is, they soak up a lot of power, and they have to run all day long. The rover batteries have 18 kilowatt-hours of juice. The oxygenator alone uses 44.1 kilowatt-hours per sol. See my problem?
You know what? “Kilowatt-hours per sol” is a pain in the ass to say. I’m gonna invent a new scientific unit name. One kilowatt-hour per sol is…it can be anything…um…I suck at this…I’ll call it a “pirate-ninja.”
All told, the Big Three need 69.2 pirate-ninjas, most of that going to the oxygenator and the atmospheric regulator. (The water reclaimer only needs 3.6 of that.)
There’ll be cutbacks.
The easiest cutback is the water reclaimer. I have 620 liters of water (I had a lot more before the Hab blew up). I need only 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 CO 2 to 900°C, 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.
One-sixth the quantity of CO 2 means one-sixth the energy to heat it.
The spec says it draws 44.1 pirate-ninjas, 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 CO 2 ? Take it out. Not enough O 2 ? Add some. Without it, the oxygenator is worthless. The CO 2 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.
Here on Mars, 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 over 100 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 21.5 pirate-ninjas. Even adding some of the Hab’s power cells would barely power the regulator for a sol, let alone give me enough 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 CO 2 toxicity.
You can have all the oxygen in the world, but once the CO 2 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 CO 2 .
That means I need the regulator. But I don’t need the oxygenator all the time.
I just need to get CO 2 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 CO 2 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 CO 2 .
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 CO 2 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.
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 80 kilometers from 18 kilowatt-hours. 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.
620 kilograms’ worth. My freeze-dried potatoes will add another 200 kilograms. 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 1200 kilograms.
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 25 kph, 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 57 kilometers before I was out of juice.
That was 57 kilometers on level ground, without having to power the regulator (which won’t take much with the heater off). Call it 50 kilometers per day to be safe. At that rate it would take 64 days to get to Schiaparelli.
But that’s just the travel time.
Every now and then, I’ll need to break for a day and let the oxygenator use all the power.
How often? After a bunch of math I worked out that my 18-pirate-ninja budget can power the oxygenator enough to make about 2.
5 sols of O 2 . I’d have to stop every two to three sols to reclaim oxygen.
My sixty-four-sol trip would become ninety-two!
That’s too long. I’ll tear my own head off if I have to live in the rover that long.
Anyway, I’m exhausted from lifting rocks and whining about lifting rocks. I think I pulled something in my back. Gonna take it easy the rest of today.
LOG ENTRY: SOL 201
Yeah, I definitely pulled something in my back. I woke up in agony.