SpaceX’s launch of NASA astronauts was scrubbed and rescheduled for Saturday due to poor weather, just 17 minutes before liftoff

SpaceX’s Crew Dragon spaceship and Falcon 9 rocket stand ready at Cape Canaveral, Florida, at NASA’s Kennedy Space Center on May 24, 2020.Ben Cooper/SpaceX

SpaceX was set to launch astronauts for the first time on Wednesday, thereby restoring NASA’s human spaceflight program. But then storm clouds rolled in.

The rocket was fueled and sitting vertical on the launchpad. Officials had conducted final reviews to make sure everything was ready for liftoff, which was scheduled for 4:33 p.m. ET. NASA astronauts Bob Behnken and Doug Hurley were suited up onboard.

But bad weather, specifically a strong electric field that could produce lightning strikes, made the skies of Cape Canaveral, Florida unsafe. The mission commanders called off the launch just 17 minutes before the scheduled liftoff.

“Not quite going to make it for this,” a weather officer said on NASA’s live feed of the launch.

He added that if they had an extra 10 minutes, the conditions could change. But the window to launch only lasts about one second.
SpaceX’s Crew Dragon spaceship and Falcon 9 rocket await launch from Cape Canaveral, Florida, at NASA’s Kennedy Space Center on May 23, 2020.Ben Cooper for SpaceX

SpaceX – the private rocket company founded by Elon Musk in 2002 – and NASA are now preparing to launch the mission, called Demo-2, at 3:22 p.m. ET on Saturday. Failing that, they have one more opportunity on Sunday at 3 p.m., Emre Kelly of Florida Today tweeted Monday.

Demo-2 is the culmination of roughly $3.1 billion in funding from NASA through the agency’s Commercial Crew Program, which is an effort to resurrect NASA’s capability to launch its own astronauts into space. The agency lost that in July 2011, after it retired its fleet of space shuttles.

“We are going to launch American astronauts on American rockets from American soil,” Bridenstine said during a televised briefing on May 1. “We’re going to do it here in the midst of the coronavirus pandemic, and I’m going to tell you that this is a high-priority mission to the United States of America.”

The mission requires Behnken and Hurley to fly SpaceX’s Crew Dragon spaceship into orbit – launched atop a Falcon 9 rocket – then dock with the International Space Station, where they could live for up to 110 days before returning to Earth.

Safe weather means low winds, no lightning, and gentle seas
NASA astronauts Douglas Hurley (left) and Robert Behnken (right) participate in a dress rehearsal for launch at the Kennedy Space Center in Florida on May 23, 2020, ahead of NASA’s SpaceX Demo-2 mission to the International Space Station.Kim Shiflett/NASA

This launch is tricky not only because it’s a test flight with people on board, but also because it has to happen when the space station is more or less flying over the launch site (so the spaceship can use less fuel). The window to launch lasts about one second, so if the moment is missed, the attempt must be scrubbed.

To ensure the moment is right, mission managers monitor weather conditions that could endanger the rocket, including lightning, rain, or heavy clouds.

“You could trigger lightning,” Tim Garner, a meteorologist at the National Oceanic and Atmospheric Administration, said on a NASA podcast in 2017. “[A rocket’s] mere presence in a high electric field will be that thing that sets off the lightning strike.”

That happened to the Apollo 12 mission in 1969. The astronauts inside the rocket felt the lightning strike, and it disabled nine non-essential instrument sensors.

That seems to have been the threat that delayed SpaceX’s launch on Wednesday.

Beyond storms, less obvious weather dynamics can throw a rocket off course as well. SpaceX CEO Elon Musk has said that high-altitude wind shear “hits like a sledgehammer.” That can cause “control problems,” according to NASA’s weather criteria for launching Falcon 9.

Those criteria outline the weather conditions needed for the rocket to launch safely, including an absence of lightning or thunderstorm anvil clouds within 10 nautical miles. There also cannot be a cloud layer thicker than 4,500 feet with freezing temperatures, and no cumulus clouds with freezing temperatures.

Additionally, SpaceX watches for high seas in the Atlantic Ocean, since that’s where emergency rescue boats will be stationed in case Behnken and Hurley have to abort, detach from the rocket, and fly to safety as the Crew Dragon flies overhead.

“We need to make sure that if the crew had to come down, in a launch-escape scenario, that they would come down in a sea state that would keep them safe, and that the rescue forces would be able to come and get them,” Benji Reed, director of Crew Mission Management at SpaceX, said in a briefing on Friday.