• • •

RICH PURNELL sipped coffee in the silent building. He ran a final test on the software he’d written. It passed. With a relieved sigh, he sank back in his chair. Checking the clock on his computer, he shook his head. 3:42 a. m.

As an astrodynamicist, Rich rarely had to work late. His job was to find the exact orbits and course corrections needed for any given mission. Usually, it was one of the first parts of a project, all the other steps being based on the orbit.

But this time, things were reversed. Iris needed an orbital path, and nobody knew when it would launch.

Planets move as time goes by. A course calculated for a specific launch date will work only for that date. Even a single day’s difference would result in missing Mars entirely.

So Rich had to calculate many courses. He had a range of twenty-five days during which Iris might launch. He calculated one course for each.

He began an e-mail to his boss.

Mike, he typed, Attached are the courses for Iris, in 1-day increments. We should start peer review and vetting so they can be officially accepted. And you were right, I was here almost all night.

It wasn’t that bad. Nowhere near the pain of calculating orbits for Hermes. I know you get bored when I go into the math, so I’ll summarize: The small, constant thrust of Hermes’s ion drives is much harder to deal with than the large point-thrusts of presupply probes.

All 25 of the courses take 414 days, and vary only slightly in thrust duration and angle. The fuel requirement is nearly identical for the orbits and is well within the capacity of EagleEye’s booster.

It’s too bad. Earth and Mars are really badly positioned. Heck, it’s almost easier to—

He stopped typing.

Furrowing his brow, he stared into the distance.

“Hmm,” he said.

He grabbed his coffee cup and went to the break room for a refill.

• • •

TEDDY SCANNED the crowded conference room. It was rare to see such an assembly of NASA’s most important people all in one place. He squared a small stack of notes he’d prepared and placed them neatly in front of him.

“I know you’re all busy,” Teddy said. “Thank you for making time for this meeting. I need status on Project Iris from all departments. Venkat, let’s start with you.”

“The mission team’s ready,” Venkat said, looking at spreadsheets on his laptop. “There was a minor turf war between the Ares 3 and Ares 4 presupply control teams. The Ares 3 guys said they should run it, because while Watney’s on Mars, Ares 3 is still in progress. The Ares 4 team points out it’s their coopted probe in the first place. I ended up going with Ares 3.”

“Did that upset Ares 4?” Teddy asked.

“Yes, but they’ll get over it. They have thirteen other presupply missions coming up. They won’t have time to be pissy.”