by Andy Weir
[18:09] Watney: system_command: STATUS
[18:09] SYSTEM: Last message sent 00h31m ago. Last message received 26h17m ago. Last ping reply from probe received 04h24m ago. WARNING: 52 unanswered pings.
Pathfinder was no longer talking to the rover. It had stopped answering pings 4 hours and 24 minutes ago. Some quick math told me that was around 13:30 today.
The same time the drill died.
I tried not to panic. The troubleshooting sheet has a list of things to try if communication is lost. They are (in order):
1. Confirm power still flowing to Pathfinder.
2. Reboot rover.
3. Reboot Pathfinder by disconnecting/reconnecting power.
4. Install rover's comm software on the other rover's computer, try from there.
5. If both rovers fail, problem is likely with Pathfinder. Check connections very closely. Clean Pathfinder of Martian dust.
6. Spell message in Morse Code with rocks, include things attempted. Problem may be recoverable with remote update of Pathfinder.
I only got as far as step 1. I checked Pathfinder's connections and the negative lead was no longer attached.
I was elated! What a relief! With a smile on my face, I fetched my electronics kit and prepared to reattach the lead. I pulled it out of the probe to give it a good cleaning (as best I can with the gloves of my space suit) and noticed something strange. The insulation had melted.
I pondered this development. Melted insulation usually means a short. More current than the wire could handle had passed through. But the bare portion of the wire wasn't black or even singed, and the positive lead's insulation wasn't melted at all.
Then, one by one, the horrible realities of Mars came in to play. The wire wouldn't be burnt or singed. That's a result of oxidization. And there's no oxygen in the air. There likely was a short after all. But with the positive lead being unaffected, the power must have come from somewhere else...
And the drill's breaker tripped around the same time...
Oh... shit...
The internal electronics for Pathfinder included a ground lead to the hull. This way it could not build up a static charge in Martian weather conditions (no water and frequent sandblasting can make impressive static charge).
The hull sat on Panel A, one of four sides of the tetrahedron which brought Pathfinder the Mars. The other 3 sides are still in Ares Vallis where I left them.
Between Panel A and the workbench were the Mylar balloons Pathfinder had used to tumble-land. I had shredded many of them to transport it. Still, a lot of material remained; enough to reach around Panel A and be in contact with the hull. I should mention that Mylar is conductive.
At 13:30, I leaned the drill against the workbench. The drill's cowling was off to make room for the power line. The workbench is metal. If the drill leaned against the workbench just right, it could make a metal-to-metal connection.
And that's exactly what happened.
Power traveled from the drill line's positive, through the workbench, through the Mylar, through Pathfinder's hull, through a bunch of extremely sensitive and irreplaceable electronics, and out the negative lead of Pathfinder's power line.
Pathfinder operates on 50 milliamps. It got nine thousand milliamps, which plowed through the delicate electronics, frying everything along the way. The breakers tripped, but it was too late.
Pathfinder's dead. I've lost the ability to contact Earth.
I'm on my own.
Chapter 18
LOG ENTRY: SOL 197
Sigh...
Just once I'd like something to go to plan, 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.
Ok, enough self-pity. I'm not doomed. Things will be 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. “PATHFINDER FRIED WITH 9AMPS. 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.
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 CO2 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 have to run all day long. The rover batteries have 18kwh of juice. The Oxygenator alone uses 44.1kwh 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... oh fuck it. I'll call it a “pirate-ninja.”
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 drow
sy. 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.
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 18pn budget can power the Oxygenator enough to make 2.5 sols of O2. I'd have to stop every two to three sols to reclaim oxygen. My 65 sol trip would become 91!
That's too fucking 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.
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 4km 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 in to 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 in to 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 in to 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.
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 canvass around the edges. Weighing down the excess canvass with rocks, I now had a water-tight bathtub!
It only took 100L 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). Hooking it up to my RTG-water-heater, I put both the input and output lines in 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 37C. 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?
LOG ENTRY: SOL 207
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, laid in my bunk a lot, and watched shitty '70's 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 14 panels I took to Pathfinder provided the 18kwh that the batteries could store. When traveling, I stowed the panels on the roof. The trailer gives me room to store another 7 (half of its roof will be missing because of the hole I'm cutting in it).
Th
is trip's power needs will be driven by the Oxygenator. It all comes down to how much power I can give that greedy little fucker 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.”
Let's get greedy. Lets say I can find a home for 14 more panels instead of 7. Not sure how to do that, but let's say I can. That would give me 38pn to work with, which would net me 5.1 sols of oxygen per air-sol. I'd only have to stop once per five sols. That's much more reasonable.
Plus, if I can arrange battery storage for the extra power, I could drive 100km per sol! Easier said than done, though. That extra 18kwh of storage will be tough. I'll have to take 2 of the Hab's 9kwh fuel cells and load them on to the rover or trailer. They aren't like the rover's batteries; they're not small or portable. They're light enough, but they're pretty big. I may have to attach them to the outside hull, and that would eat in to my solar cell storage.
100km per sol, stopping every fifth sol to reclaim oxygen. If I could pull that off, I'd get there 40 sols. That would be sweet!
In other news, It occurred to me that NASA is probably shitting bricks. They're watching me with satellites, and haven't seen me come out of the Hab for six days. With my back better, it was time to drop them a line.
I headed out for an EVA. This time, being very careful while lugging rocks around, I spelled out a Morse code message: “INJURED BACK. BETTER NOW. CONTINUING ROVER MODS.”
That was enough physical labor for today. I don't want to overdo it.
Think I'll have a bath.
LOG ENTRY: SOL 208
Today, it was time to experiment with the panels.