“How much more?”

“For every kilogram of hydrogen, it can make thirteen kilograms of fuel. Watney has five hundred and fifty liters of water. We’ll have him electrolyze it to get sixty kilograms of hydrogen.” Bruce reached over the desk and flipped a few pages, pointing to a diagram. “The fuel plant can make seven hundred and eighty kilograms of fuel from that.”

“If he electrolyzes his water, what’ll he drink?”

“He only needs fifty liters for the time he has left. And a human body only borrows water. We’ll have him electrolyze his urine, too. We need all the hydrogen we can get our hands on.”

“I see. And what does seven hundred and eighty kilograms of fuel buy us?” Venkat asked.

“It buys us 300 kilograms of payload. It’s all about fuel versus payload. The MAV’s launch weight is over 12,600 kilograms. Even with the bonus fuel, we’ll need to get that down to 7,300 kilograms. So the rest of this booklet is how to remove over 5,000 kilograms from the ship.”

Venkat leaned back. “Walk me through it.”

Bruce pulled another copy of the booklet from his briefcase. “There were some gimmes right off the bat. The design presumes five hundred kilograms of Martian soil and rock samples. Obviously we won’t do that. Also, there’s just one passenger instead of six. That saves five hundred kilograms when you consider their weight plus their suits and gear. And we can lose the other five acceleration chairs. And of course, we’ll remove all nonessential gear—the med kit, tool kit, internal harnessing, straps, and anything else that isn’t nailed down. And some stuff that is.

“Next up,” he continued, “We’re ditching all life support. The tanks, pumps, heaters, air lines, CO₂ absorption system, even the insulation on the inner side of the hull. We don’t need it. We’ll have Watney wear his EVA suit for the whole trip.”

“Won’t that make it awkward for him to use the controls?” Venkat asked.

“He won’t be using them,” Bruce said. “Major Martinez will pilot the MAV remotely from Hermes. It’s already designed for remote piloting. It was remotely landed, after all.”

“What if something goes wrong?” Venkat asked.

“Martinez is the best trained pilot,” Bruce said. “If there is an emergency, he’s the guy you want controlling the ship.”

“Hmm,” Venkat said cautiously. “We’ve never had a manned ship controlled remotely before. But okay, go on.”

“Since Watney won’t be flying the ship,” Bruce continued, “he won’t need the controls. We’ll ditch the control panels and all the power and data lines that lead to them.”

“Wow,” Venkat said. “We’re really gutting this thing.”

“I’m just getting started,” Bruce said. “The power needs will be dramatically reduced now that life support is gone, so we’ll dump three of the five batteries and the auxiliary power system. The orbital maneuvering system has three redundant thrusters. We’ll get rid of those. Also, the secondary and tertiary comm systems can go.”

“Wait, what?” Venkat said, shocked. “You’re going to have a remote-controlled ascent with no backup comm systems?”