“Ignition sequence start.”

“…three… two… one…”

Clamps released, the booster rose amid a plume of smoke and fire, slowly at first, then racing ever faster. The assembled crowd cheered it on its way.

“…and liftoff of the Iris supply probe,” the timer controller said.

As the booster soared, Mitch had no time to watch the spectacle on the main screen. “Trim?” he called out.

“Trim’s good, Flight” was the immediate response.

“Course?” he asked.

“On course.”

“Altitude one thousand meters,” someone said.

“We’ve reached safe-abort,” another person called out, indicating that the ship could crash harmlessly into the Atlantic Ocean if necessary.

“Altitude fifteen hundred meters.”

“Pitch and roll maneuver commencing.”

“Getting a little shimmy, Flight.”

Mitch looked over to the ascent flight director. “Say again?”

“A slight shimmy. Onboard guidance is handling it.”

“Keep an eye on it,” Mitch said.

“Altitude twenty-five hundred meters.”

“Pitch and roll complete, twenty-two seconds till staging.”

• • •

WHEN DESIGNING Iris, JPL accounted for catastrophic landing failure. Rather than normal meal kits, most of the food was cubed protein bar material, which would still be edible even if Iris failed to deploy its tumble balloons and impacted at incredible speed.

Because Iris was an unmanned mission, there was no cap on acceleration. The contents of the probe endured forces no human could survive. But while NASA had tested the effects of extreme g-forces on protein cubes, they had not done so with a simultaneous lateral vibration. Had they been given more time, they would have.

The harmless shimmy, caused by a minor fuel mixture imbalance, rattled the payload. Iris, mounted firmly within the aeroshell atop the booster, held firm. The protein cubes inside Iris did not.

At the microscopic level, the protein cubes were solid food particles suspended in thick vegetable oil. The food particles compressed to less than half their original size, but the oil was barely affected at all. This changed the volume ratio of solid to liquid dramatically, which in turn made the aggregate act as a liquid. Known as “liquefaction,” this process transformed the protein cubes from a steady solid into a flowing sludge.

Stored in a compartment that originally had no leftover space, the now-compressed sludge had room to slosh.

The shimmy also caused an imbalanced load, forcing the sludge toward the edge of its compartment. This shift in weight only aggravated the larger problem, and the shimmy grew stronger.

• • •

“SHIMMY’S GETTING violent,” reported the ascent flight director.

“How violent?” Mitch said.

“More than we like,” he said. “But the accelerometers caught it and calculated the new center of mass. The guidance computer is adjusting the engines’ thrusts to counteract. We’re still good.”

“Keep me posted,” Mitch said.

“Thirteen seconds till staging.”

The unexpected weight shift had not spelled disaster. All systems were designed for worst-case scenarios; each did its job admirably. The ship continued toward orbit with only a minor course adjustment, implemented automatically by sophisticated software.

The first stage depleted its fuel, and the booster coasted for a fraction of a second as it jettisoned stage clamps via explosive bolts. The now-empty stage fell away from the craft as the second-stage engines prepared to ignite.