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. Eighty-seven days’ worth. Plenty.
Oxygen’s a little trickier. The rover was designed to support three people for two days, plus some reserve for safety. So its O2 tanks can hold enough to last me seven days. Not enough.
Mars has almost no atmospheric pressure. The inside of the rover has one 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 25-liter liquid oxygen tanks and brought it into the rover. According to NASA, a human needs 588 liters 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 49 days. That’ll be plenty.
Sirius 4 will be a twenty-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 forty 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. A 10-liter tank of compressed liquid CO2, vented into 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 into 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 Warner 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 operations for NASA. Dr. Kapoor, thank you for coming.”
“A pleasure to be here, Cathy,” Venkat said.
“Dr. Kapoor,” Cathy said, “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 twelve 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 said, “it looks like he’s preparing Rover 2 for a long trip. On Sol 64, he took the battery from the other rover and attached it with a homemade sling. The next day, he detached fourteen 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 four kilometers 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 thirty-two hundred kilometers 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? 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.”
MINDY GLANCED nervously around the conference room. She’d never felt so thoroughly outranked in her life. Dr. Venkat Kapoor, who was four levels of management above her, sat to her left.
Next to him was Bruce Ng, the director of JPL. He’d flown all the way to Houston from Pasadena just for this meeting. Never one to let precious time go to waste, he typed furiously on his laptop. The dark bags under his eyes made Mindy wonder just how overworked he truly was.
Mitch Henderson, the flight director for Ares 3, swiveled back and forth in his chair, a wireless earpiece in his ear. It fed him a real-time stream of all the comm chatter from Mission Control. He wasn’t on shift, but he was kept apprised at all times.
Annie Montrose entered the conference room, texting as she walked. Never taking her eyes off her phone, she deftly navigated around the edge of the room, avoiding people and chairs, and sat in her usual spot. Mindy felt a pang of envy as she watched the director of media relations. She was everything Mindy wanted to be. Confident, high-ranking, beautiful, and universally respected within NASA.
“How’d I do today?” Venkat asked.
“Eeeh,” Annie said, putting her phone away. “You shouldn’t say things like ‘bring him home alive.’ It reminds people he might die.”
“Think they’re going to forget that?”