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?”