KENNEDY SPACE CENTER, Fla. – After the first attempt to launch NASA astronauts from Kennedy Space Center for the first time in years was scrubbed due to weather SpaceX will try again this weekend but some might be asking, “why not launch Friday?” because the weather is a lot better than the stormy conditions expected again Saturday and Sunday.
The reason NASA and SpaceX have set days and times to launch Astronauts Bob Behnken and Doug Hurley to the International Space Station depends on a lot of factors, outside of the weather alone.
The International Space Station is home to hundreds of science experiments and astronauts from several counties. Spacecraft from three different counties can launch and dock at the station to bring supplies or bring cargo back to Earth. That can mean managing traffic from multiple cargo supply missions as well as astronaut arrivals and departures.
On Monday, a Japanese spacecraft, HT-9, arrived on station bringing four tons of supplies including new science experiments and spare parts for the ISS. On May 12, Northrop Grumman’s Cygnus cargo craft departed the space station.
The Russian Soyuz spacecraft is also currently docked at the ISS. That spacecraft is how astronauts launch to the station and return to Earth. A successful mission for SpaceX’s Crew Dragon will mean astronauts will now have a second ride to the orbiting laboratory.
NASA must work with Russia and Japan to make sure there are no conflicts in docking another spacecraft at the station.
The crew on board the space station are also very busy. Their schedules are packed with station maintenance, doing experiments, exercising and somewhere in there they also need to sleep.
NASA Administrator Jim Bridenstine said launch teams also consider the astronaut’s schedule before a launch.
“We’re balancing a lot of things. We’re also balancing the time of day that we launch, making sure that we have to consider the sleep cycles of the crew to make sure that they’re not, you know, in the midst of a very critical portion of the flight, when they’ve been without sleep for a period of 24 hours,” Bridenstine said.
The launch window to the ISS is also a factor, Bridenstine said. Whereas some spacecraft and satellites have launch windows that are several hours that is not the case when sending supplies or people to the station.
“When you talk about launching to the International Space Station, your launch window is not a window at all. It’s instantaneous,” he said. “If you don’t meet it you don’t go.”
Finally, the weather plays a major role in any launch but there are more weather factors to consider when humans are launching, too.
There are weather certain criteria under which a rocket launch will not be able to launch for safety reasons. For Crew Dragon and Falcon 9, because two astronauts are on board they also must factor in conditions in the Atlantic Ocean in case of a launch abort.
There are 14 weather conditions that would prevent the launch from happening, according to NASA, which include cloud cover, rain, lightning and conditions at sea.
The 45th Weather Squadron is predicting a 50% chance of good launch conditions for the Saturday window at 3:22 p.m. and 40% on Sunday at 3 p.m., which are not great, considering that’s only the weather for liftoff. SpaceX must also factor in recovery conditions at sea, where rescue crews will be standing by in the Atlantic Ocean should an emergency abort happen and the Crew Dragon capsule is jettisoned away from the rocket, landing in the Atlantic Ocean.
Bridenstine said NASA and SpaceX will get another weather update from the 45th Weather Squadron at 4 p.m. Friday. After that, the decision will be made to either attempt the launch again on Saturday or Sunday. For now, the launch is scheduled for 3:22 p.m. Saturday.