On the real trip, I’m going to have 620 liters of water. I made up the weight difference by loading 600 kilograms of rocks in with my other supplies.

Back on Earth, universities and governments are willing to pay millions to get their hands on Mars rocks. I’m using them as ballast.

I’m doing one more little test tonight. I made sure the batteries were good and full, then disconnected the rover and trailer from Hab power. I’ll be sleeping in the Hab, but I left the rover’s life support on. It’ll maintain the air overnight, and tomorrow I’ll see how much power it ate up. I’ve watched the power consumption while it’s attached to the Hab, and there weren’t any surprises. But this’ll be the true proof. I call it the “plugs-out test.”

Maybe that’s not the best name.

• • •

THE CREW of Hermes gathered in the Rec.

“Let’s get through status quickly,” Lewis said. “We’re all behind in our science assignments. Vogel, you first.”

“I repaired the bad cable on VASIMR 4,” Vogel reported. “It was our last thick-gauge cable. If another such problem occurs, we will have to braid lower-gauge lines to carry the current. Also, the power output from the reactor is declining.”

“Johanssen,” Lewis said, “what’s the deal with the reactor?”

“I had to dial it back,” Johanssen said. “It’s the cooling vanes. They aren’t radiating heat as well as they used to. They’re tarnishing.”

“How can that happen?” Lewis asked. “They’re outside the craft. There’s nothing for them to react with.”

“I think they picked up dust or small air leaks from Hermes itself. One way or another, they’re definitely tarnishing. The tarnish is clogging the micro-lattice, and that reduces the surface area. Less surface area means less heat dissipation. So I limited the reactor enough that we weren’t getting positive heat.”

“Any chance of repairing the cooling vanes?”

“It’s on the microscopic scale,” Johanssen said. “We’d need a lab. Usually they replace the vanes after each mission.”

“Will we be able to maintain engine power for the rest of the mission?”

“Yes, if the rate of tarnishing doesn’t increase.”

“All right, keep an eye on it. Beck, how’s life support?”

“Limping,” Beck said. “We’ve been in space way longer than it was designed to handle. There are a bunch of filters that would normally be replaced each mission. I found a way to clean them with a chemical bath I made in the lab, but it eats away at the filters themselves. We’re okay right now, but who knows what’ll break next?”

“We knew this would happen,” Lewis said. “The design of Hermes assumed it would get an overhaul after each mission, but we’ve extended Ares 3 from 396 days to 898. Things are going to break. We’ve got all of NASA to help when that happens. We just need to stay on top of maintenance. Martinez, what’s the deal with your bunk room?”

Martinez furrowed his brow. “It’s still trying to cook me. The climate control just isn’t keeping up. I think it’s the tubing in the walls that brings the coolant. I can’t get at it because it’s built into the hull. We can use the room for storage of non-temperature-sensitive cargo, but that’s about it.”