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.
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 O2. 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.
Yeah, I definitely pulled something in my back. I woke up in agony.
So I took a break from rover planning. Instead, I spent the day taking drugs and playing with radiation.
First, I loaded up on Vicodin for my back. Hooray for Beck’s medical supplies!
Then I drove out to the RTG. It was right where I left it, in a hole four kilometers away. Only an idiot would keep that thing near the Hab. So anyway, I brought it back to the Hab.
Either it’ll kill me or it won’t. A lot of work went into making sure it doesn’t break. If I can’t trust NASA, who can I trust? (For now I’ll forget that NASA told us to bury it far away.)
I stored it on the roof of the rover for the trip back. That puppy really spews heat.
I have some flexible plastic tubing intended for minor water reclaimer repairs. After bringing the RTG into the Hab, I very carefully glued some tubing around the heat baffles. Using a funnel made from a piece of paper, I ran water through the tubing, letting it drain into a sample container.
Sure enough, the water heated up. That’s not really a surprise, but it’s nice to see thermodynamics being well behaved.
There’s one tricky bit: The atmospheric regulator doesn’t run constantly. The freeze-separation speed is driven by the weather outside. So the returning frigid air doesn’t come as a steady flow. And the RTG generates a constant, predictable heat. It can’t “ramp up” its output.
So I’ll heat water with the RTG to create a heat reservoir, then I’ll make the return air bubble through it. That way I don’t have to worry about when the air comes in. And I won’t have to deal with sudden temperature changes in the rover.
When the Vicodin wore off, my back hurt even more than before. I’m going to need to take it easy. I can’t just pop pills forever. So I’m taking a few days off from heavy labor. To that end, I made a little invention just for me….
I took Johanssen’s cot and cut out the hammock. Then I draped spare Hab canvas over the frame, making a pit inside the cot, with extra canvas around the edges. Once I weighed down the excess canvas with rocks, I had a water-tight bathtub!
It only took 100 liters to fill the shallow tub.
Then, I stole the pump from the water reclaimer. (I can go quite a while without the water reclaimer operating.) I hooked it up to my RTG water heater and put both the input and output lines into the tub.
Yes, I know this is ridiculous, but I hadn’t had a bath since Earth, and my back hurts. Besides, I’m going to spend 100 sols with the RTG anyway. A few more won’t hurt. That’s my bullshit rationalization and I’m sticking with it.
It took two hours to heat the water to 37°C. Once it did, I shut off the pump and got in. Oh man! All I can say is “Ahhhhhh.”
Why the hell didn’t I think of this before?
I spent the last week recovering from back problems. The pain wasn’t bad, but there aren’t any chiropractors on Mars, so I wasn’t taking chances.
I took hot baths twice a day, lay in my bunk a lot, and watched shitty seventies TV. I’ve already seen Lewis’s entire collection, but I didn’t have much else to do. I was reduced to watching reruns.
I got a lot of thinking done.
I can make everything better by having more solar panels. The fourteen panels I took to Pathfinder provided the 18 kilowatt-hours that the batteries could store. When traveling, I stowed the panels on the roof. The trailer gives me room to store another seven (half of its roof will be missing because of the hole I’m cutting in it).
This trip’s power needs will be driven by the oxygenator. It all comes down to how much power I can give that greedy little bastard in a single sol. I want to minimize how often I have days with no travel. The more juice I can give the oxygenator, the more oxygen it’ll liberate, and the longer I can go between those “air sols.”