by Andy Weir
LOG ENTRY: SOL 66
The time has come (ominous musical crescendo) for some missions!
NASA gets to name their missions after gods and stuff, so why can’t I? Henceforth, rover experimental missions will be “Sirius” missions. Get it? Dogs? Well if you don’t, fuck you.
Sirius 1 will be tomorrow.
The mission: Starting with fully charged batteries, and having the solar cells on the roof, drive until I run out of power, and see how far I get.
I won’t be an idiot. I’m not driving directly away from the Hab. I’ll drive a half-kilometer stretch, back and forth. I’ll be within a short walk of home all times.
Tonight, I’ll charge up both batteries so I can be ready for a little test drive tomorrow. I estimate 3½ hours of driving, so I’ll need to bring fresh CO2 filters. And, with the heater off, I’ll wear three layers of clothes.
LOG ENTRY: SOL 67
Sirius 1 is complete!
More accurately, Sirius 1 was aborted after 1 hour. I guess you could call it a “failure” but I prefer the term “learning experience.”
Things started out fine. I drove to a nice flat spot a kilometer from the Hab, then started going back and forth over a 500m stretch.
I quickly realized this would be a crappy test. After a few laps, I had compressed the soil enough to have a solid path. Nice, hard ground, which makes for abnormally high energy efficiency. This is nothing like it would be on a long trip.
So I shook it up a bit. I drove around randomly, making sure to stay within a kilometer of the Hab. A much more realistic test.
After an hour, things started to get cold. And I mean really cold.
The rover’s always cold when you first get in it. When you haven’t disabled the heater it warms up right away. I expected it to be cold, but Jesus Christ!
I was fine for a while. My own body heat plus three layers of clothing kept me warm and the rover’s insulation is top-notch. The heat that escaped my body just warmed up the interior. But there’s no such thing as perfect insulation, and eventually the heat left to the great outdoors while I got colder and colder.
Within an hour, I was chattering and numb. Enough was enough. There’s no way I could do a long trip like this. The test was over.
Turning the heater on, I drove straight back to the Hab.
Once I got home, I sulked for a while. All my brilliant plans foiled by thermodynamics. Damn you, Entropy!
I’m in a bind. The damn heater will eat half my battery power every day. I could turn it down, I guess. Be a little cold but not freezing to death. Even then I’d still lose at least a quarter.
This will require some thought. I have to ask myself… what would Hercule Poirot do? I’ll have to put my “little gray cells” to work on the problem.
LOG ENTRY: SOL 68
Well shit.
I came up with a solution, but… remember when I burned rocket fuel in the Hab? This’ll be more dangerous.
I’m going to use the RTG.
The RTG (Radioisotope Thermoelectric Generator) is a big box of Plutonium. But not the kind used in nuclear bombs. No, no. This Plutonium is way more dangerous!
Plutonium-238 is an incredibly unstable isotope. It’s so radioactive that it will get red hot all by itself. As you can imagine, a material that can literally fry an egg with radiation is kind of dangerous.
The RTG houses the Plutonium, catches the radiation in the form of heat, and turns it in to electricity. It’s not a reactor. The radiation can’t be increased or decreased. It’s a purely natural process happening at the atomic level.
As long ago as the 1960’s, NASA’s been using RTGs to power unmanned probes. It has lots of advantages over solar power. It’s not affected by storms; it works day or night; it’s entirely internal, so you don’t need delicate solar cells all over your probe.
But they never used large RTGs on manned missions until The Ares Program.
Why not? It should be pretty fucking obvious why not! They didn’t want to put astronauts next to a glowing hot ball of radioactive death!
I'm exaggerating a little. The Plutonium is inside a bunch of pellets, each one sealed and insulated to prevent radiation leakage even if the outer container is breached. So for the Ares Program, they took the risk.
An Ares mission is all about the MAV. It’s the single most important component. It’s one of the few systems that can’t be replaced or worked around. It’s the only component that causes a complete mission scrub if it’s not working.
Solar cells are great in the short-term, and they’re good for the long-term if you have humans around to clean them. But the MAV sits alone for years quietly making fuel, then just kind of hangs out until its crew arrives. Even doing nothing, it needs power, so NASA can monitor it remotely and run self checks.
The prospect of scrubbing a mission because a solar cell got dirty was unacceptable. They needed a more reliable source of power. So the MAV comes equipped with an RTG. It has 2.6kg of Plutonium-238, which makes almost 1500 Watts of heat. It can turn that in to 100 Watts of electricity. The MAV runs on that until the crew arrive.
100 Watts isn’t enough to keep the heater going, but I don’t care about the electrical output. I want the heat. A 1500 Watt heater is so warm I’ll have to tear insulation out of the rover to keep it from getting too hot.
As soon as the rovers were un-stowed and activated, Commander Lewis had the joy of disposing of the RTG. She detached it from the MAV, drove 4 km away, and buried it. However safe it may be, it's still a radioactive core and NASA didn't want it too close to their astronauts.
The mission parameters don’t give a specific location to dump the RTG. Just “At least 4km away”. So I’ll have to find it.
I have two things working for me. First, I was assembling solar panels with Vogel when Commander Lewis drove off, and I saw she headed due south. Also, she planted a 3 meter pole with a bright green flag on it where she buried it. Green shows up extremely well against the Martian terrain. It’s made to ward us off, in case we get lost on a rover EVA later on.
So my plan is: Head south 4km, then search around till I see the green flag.
Having rendered Rover 1 unusable, I’ll have to use my Mutant Rover for the trip. I can make a useful test mission of it. I’ll see how well the battery harness holds up to a real journey, and how well the solar cells do strapped to the roof.
I’ll call it Sirius 2.
LOG ENTRY: SOL 69
Found the RTG.
It wasn’t hard to find. I drove 4km south and saw the flag right away.
Commander Lewis had buried it atop a small hill. She probably wanted to make sure everyone could see the flag, and it worked great! Except instead of avoiding it, I bee-lined to it and dug it up. Not exactly what she was going for.
It’s a large cylinder with heat-sinks all around it. I could feel the warmth it gave off even through my suit’s gloves. That’s really disconcerting. Especially when you know the root cause of the heat is radiation.
No point in putting it on the roof; my plan was to have it in the cabin anyway. So I brought it in with me, turned off the heater, then drove back to the Hab.
In the 10 minutes it took to get home, even with the heater off, the interior of the rover became an uncomfortably hot 37C. The RTG would definitely be able to keep me warm.
The trip also proved my rigging worked. The solar cells and extra battery stayed beautifully in place while traversing 8km of random terrain.
I declare Sirius 2 to be a successful mission!
I spent the rest of the day vandalizing the interior of the rover. The pressure compartment is made of metal. Just inside that is insulation, which is covered by hard plastic. I used a sophisticated method to remove sections of plastic (hammer), then carefully removed the solid foam insulation (hammer again).
After tearing out some insulation, I suited up and took the RTG outside. Soon, the rover cooled down again, and I brought it back in. I watched as the temperature rose
slowly. Nowhere near as fast as it had on my trip back from the burial site.
I cautiously removed more insulation (hammer) and checked again. After a few more cycles of this, I had enough insulation torn out that the RTG could barely keep up with it. In fact, it was a losing battle. Over time, heat would slowly leech out. That’s fine. I can turn on the heater for short bursts when necessary.
I brought the insulation pieces with me back in to the Hab. Using advanced construction techniques (duct tape) I reassembled some of it into a square. I figure if things got really cold, I could tape that to a bare patch in the rover, and the RTG would be winning the “heat fight.”
Tomorrow, Sirius 3 (Which is just Sirius 1 again, but without freezing)
LOG ENTRY: SOL 70
Today, I write to you from the rover. I’m halfway-through Sirius 3 and things are going well.
I set out at first light and drove laps around the Hab, trying to stay on untouched ground. The first battery lasted just under two hours. After a quick EVA to switch the cables, I got back to driving. When all was said and done, I had driven 81km in 3 hours and 27 minutes.
That’s very good! Mind you, the land around the Hab is really flat, as is all of Acidalia Planitia. I have no idea what my efficiency would be on the nastier land en route to Ares 4.
I could have gone further, but I need life support while recharging. The CO2 gets absorbed through a chemical process, but if the fan that pushes it isn’t working, I’ll choke. The oxygen pump is also kind of important.
I set up the solar cells. It was hard work; last time I had Vogel’s help. They aren’t heavy, but they’re awkward. After setting up half of them, I figured out I could drag them rather than carry them and that sped things up.
Now I’m just waiting for the batteries to recharge. I’m bored, so I’m updating the log. I have all the Poirot books in my computer. That’ll help. It’s going to take 12 hours to recharge, after all.
What’s that, you say? 12 hours is wrong? I said 13 hours earlier? Well, my friend, let me set you straight.
The RTG is a generator. It’s a paltry amount of power, compared to what the rover consumes, but it’s not nothing. It’s 100 Watts. It’ll cut an hour off my total recharge time. Why not use it?
I wonder what NASA would think about me fucking with the RTG like this. They’d probably hide under their desks and cuddle their slide-rules for comfort.
LOG ENTRY: SOL 71
As predicted, it took 12 hours to charge the batteries to full. I came straight home.
Time to make plans for Sirius 4. And I think it’ll be a multi-day field trip.
Looks like power and battery recharging is solved. Food’s not a problem; there’s plenty of space to store things. Water’s even easier than food. I need 2L per day to be comfortable.
In the long term, I’ll need to bring the Oxygenator. But it’s big and I don’t want to screw with it right now. So I’ll rely on O2 and CO2 filters for Sirius 4.
CO2 isn’t a problem. I started this grand adventure with 1500 hours of CO2 filters, plus another 720 for emergency use. All systems use standard filters (Apollo 13 taught us important lessons). Since then, I’ve used 131 hours of filter on various EVAs. I have 2089 left. 87 days worth. Plenty.
The rover was designed to support 3 people for 2 days, plus some reserve for safety. So its O2 tanks can hold enough to last me 7 days. Not enough.
Mars has 1/90th Earth’s atmospheric pressure. The inside of the rover has 1 atmosphere. So the oxygen tanks are on the inside (less pressure differential to deal with). Why does that matter? It means I can bring along other oxygen tanks, and equalize them with the rover’s tanks without having to do an EVA.
So today, I detached one of the Hab’s two 25L oxygen tanks and brought it in to the rover. According to NASA, a human needs 588L of oxygen per day to live. Compressed liquid O2 is about 1000 times as dense as gaseous O2 in a comfortable atmosphere. Long story short: with the Hab tank, I have enough O2 to last 42 days. That’ll be plenty.
Sirius 4 will be a 20 day trip.
That may seem a bit long, but I have a specific goal in mind. Besides, my trip to Ares 4 will be at least 40 days. This is a good scale model.
While I’m away, the Hab can take care of itself, but the potatoes are an issue. I’ll saturate the ground with most of the water I have. Then, I’ll deactivate the Atmospheric Regulator, so it doesn’t pull water out of the air. It’ll be humid as hell, and water will condense on every surface. That’ll keep the potatoes well watered while I’m away.
A bigger problem is CO2. The potatoes need to breathe. I know what you’re thinking. “Mark, old chap! YOU produce carbon dioxide! It’s all part of the majestic circle of nature!”
The problem is: Where will I put it? Sure, I exhale CO2 with every breath, but I don’t have any way to store it. I could turn off the Oxygenator and Atmospheric Regulator and just fill the Hab with my breath over time. But CO2 is deadly to me. I need to release a bunch at once and run away.
Remember the MAV fuel plant? It collects CO2 from the Martian atmosphere. My small crops aren’t nearly as needy as me, so a 10L tank of compressed liquid CO2, vented in to the Hab, will be enough CO2 to do the trick. That’ll take less than a day to create.
So that’s everything. Once I vent the CO2 in to the Hab, I’ll turn off the Atmospheric Regulator and Oxygenator, dump a ton of water on the crops, and head out.
Sirius 4. A huge step forward in my rover research. And I can start tomorrow.
Chapter 8
“Hello, and thank you for joining us,” Cathy said to the camera. “Today on CNN’s Mark Watney Report: Several EVAs over the past few days… what do they mean? What progress has NASA made on a rescue option? And how will this affect the Ares 4 preparations?
“Joining us today is Dr. Venkat Kapoor, Director of Mars Missions for NASA. Dr. Kapoor, thank you for coming.”
“A pleasure to be here, Cathy,” Venkat said.
“Dr. Kapoor,” Cathy began, “Mark Watney is the most-watched man in the solar system, wouldn’t you say?”
Venkat nodded. “Certainly the most watched by NASA. We have all 12 of our Martian satellites taking pictures whenever his site’s in view. The European Space Agency has both of theirs doing the same.”
“All told, how often do you get these images?”
“Every few minutes. Sometimes there’s a gap, based on the satellite orbits. But it’s enough that we can track all his EVA activities.”
“Tell us about these latest EVAs.”
“Well,” Venkat began, “It looks like he’s preparing Rover 2 for a long trip. On Sol 65, he took the battery from the other rover and attached it with a homemade sling. The next day, he detached 14 solar cells and stacked them on the rover’s roof.”
“And then he took a little drive, didn’t he?” Cathy prompted.
“Yes he did. Sort of aimlessly for an hour, then back to the Hab. He was probably testing it. Next time we saw him was two days later, when he drove 4km away, then back. Another incremental test, we think. Then, over the past couple of days, he’s been stocking it up with supplies.”
“Hmm,” Cathy said, “Most analysts think Mark’s only hope of rescue is to get to the Ares 4 site. Do you think he’s come to the same conclusion?”
“Probably,” Venkat said. “He doesn’t know we’re watching. From his point of view, Ares 4 is his only hope.”
“Do you think he’s planning to go soon? He seems to be getting ready for a trip.”
“I hope not,” Venkat said. “There’s nothing at the site other than the MAV. None of the other presupplies. It would be a very long, very dangerous trip, and he’d be leaving the safety of the Hab behind.”
“Why would he risk it?”
“Communication,” Venkat said. “Once he reaches the MAV, he could contact us.”
“So that would be a good thing, wouldn’t it?”
“Communication would be a great thing. But traversing 3,200km to Ares 4 is
incredibly dangerous. We’d rather he stayed put. If we could talk to him, we’d certainly tell him that.”
“He can’t stay put forever, right?” she asked. “Eventually he’ll need to get to the MAV.”
“Not necessarily,” Venkat said. “JPL is experimenting with modifications to the MDV so it can make a brief overland flight after landing.”
“I’d heard that idea was rejected as being too dangerous,” Cathy said.
“Their first proposal was, yes. Since then, they’ve been working on safer ways to do it.”
“With only three and a half years before Ares 4’s scheduled launch, is there enough time to make and test modifications to the MDV?”
“I can’t answer that for sure. But remember, we made a lunar lander from scratch in seven years.”
“Excellent point,” Cathy smiled. “So what are his odds right now?”
“No idea,” Venkat said. “But we’re going to do everything we can to bring him home alive.”
“How’d I do today?” Venkat asked.
“Eeeh,” Annie said. “You shouldn’t say things like ‘Bring him home alive.’ It reminds people he might die.”
“Think they’re going to forget that?”
“You asked my opinion. Don’t like it? Go fuck yourself.”
“You’re such a delicate flower, Annie. How’d you end up NASA’s Communications Director?”
“Beats the fuck out of me,” Annie said.
“Guys,” said Bruce Ng, Director of JPL. “I need to catch a flight back to LA in three hours. Is Teddy coming or what?”
“Quit bitching, Bruce,” Annie said. “None of us want to be here.”
“So,” said Hermes Flight Director Mitch Henderson “Who are you, again?”
“Um,” Mindy said, “I’m Mindy Park. I work in SatCon.”
“You a director or something?”
“No, I just work in SatCon. I’m a nobody.”
Venkat looked to Mitch “I put her in charge of tracking Watney. She gets us the imagery.”
“Huh,” said Mitch. “Not the Director of SatCon?”
“Bob’s got more to deal with than just Mars. Mindy’s handling all the Martian satellites, and keeps them pointed at Mark.”
“Why Mindy?” Mitch asked.