With the weather looking up, SpaceX and NASA officials vowed Tuesday to keep crew safety the top priority for the nation's first astronaut launch to orbit in nearly a decade.
Veteran NASA astronauts Doug Hurley and Bob Behnken were set to make history Wednesday afternoon, riding SpaceX's Falcon 9 rocket and Dragon capsule to the International Space Station on a test flight.
SpaceX was on the cusp of becoming the first private company to put astronauts in orbit, something achieved by just three countries — Russia, the U.S. and China.
On the eve of the launch, NASA Administrator Jim Bridenstine said from Kennedy Space Center that both the space agency and SpaceX have been diligent about making sure everyone in the launch loop knows they're free to halt the countdown if there's a concern.
President Donald Trump and Vice President Mike Pence are expected at Kennedy for the planned 4:33 p.m. liftoff, but “our highest priority” will remain the astronauts' safety, according to Bridenstine.
Bridenstine said he texted the two astronauts Monday and told them, “`If you want me to stop this thing for any reason, say so. I will stop it in a heartbeat if you want me to.' They both came back and they said, ‘We’re go for launch.' ”
Hans Koenigsmann, a SpaceX vice president, said Monday evening that he and other company workers have imagined themselves in the astronauts' shoes on launch day — “or their helmets.”
“That changes the equation pretty dramatically," he said.
SpaceX has been launching cargo capsules to the space station since 2012.
“It's a huge step, obviously, going from cargo ... to launching two people that are dads as we call them and have families, kids, wives.," Koenigsmann added.
NASA will have input throughout the countdown, but in the end, it will be SpaceX giving the final go — with NASA's concurrence.
“SpaceX is controlling the vehicle, there’s no fluff about that,” Norm Knight, a NASA flight operations manager, said Monday.
The odds of acceptable launch weather improved Tuesday to 60%. But that didn't factor in conditions along the Dragon’s route to orbit.
SpaceX needs relatively calm waves and wind up the U.S. and Canadian seaboard and across the North Atlantic to Ireland, in case astronauts Hurley and Behnken need to make an emergency splashdown.
If SpaceX does not launch during Wednesday's split-second window, the next try would be Saturday. Liftoff is set for 4:33 p.m. EDT.
The last time astronauts launched from Florida was on NASA's final space shuttle flight in July 2011. Hurley was the pilot of that mission.
NASA hired SpaceX and Boeing in 2014 to transport astronauts to the space station, after commercial cargo shipments had taken off. Development of SpaceX's Dragon and Boeing's Starliner capsules took longer than expected, however, and the U.S. has been paying Russia to launch NASA astronauts in the interim.