WASHINGTON — NASA has delayed the undocking of a Crew Dragon spacecraft from the International Space Station by a day because of high winds at splashdown locations in the Gulf of Mexico, a move that won’t affect the launch of the next crew to the station.
NASA announced early Nov. 7 that it was postponing the undocking of the Crew Dragon spacecraft Endeavour that was scheduled for 12:05 p.m. Eastern that day. NASA said in a statement that a weather review showed winds “unfavorable for recovery” when the spacecraft would splash down in the Gulf at about 7:14 a.m. Eastern Nov. 8.
NASA is now scheduling the undocking for 2:05 p.m. Eastern Nov. 8, which would set up a splashdown off the Florida coast at 10:33 p.m. Eastern that day.
At a Nov. 6 media teleconference about the upcoming return of the Crew-2 mission, Sarah Walker, director of Dragon mission management at SpaceX, said winds at the splashdown locations were several kilometers per hour above limits for the spacecraft. Those limits are about 14 kilometers per hour at the primary splashdown location and 18.5 kilometers per hour at an alternative location. She said managers elected to wait until a briefing six hours before the previously scheduled undock time to get updated weather conditions and decide whether to proceed with the undocking.
An undocking and return on Nov. 8 would still allow NASA and SpaceX to proceed with the launch of the Crew-3 mission, scheduled for 9:03 p.m. Eastern Nov. 10, with additional launch opportunities Nov. 11 and 12.
A gap of a little less than 48 hours between splashdown of Crew-2 and launch of Crew-3 “is a supportable amount of time,” Walker said, because the personnel and assets, such as boats, are largely separate between splashdown and launch. The gap is also enough time to review data from Crew-2’s return ahead of launch of Crew-3.
Having Crew-2 come back to Earth before Crew-3 launches is what NASA calls an “indirect” handover. The agency prefers a direct handover, where Crew-3 arrives before Crew-2 leaves, allowing for an overlap on the station. A direct handover was planned before weather and a minor medical issue with a Crew-3 astronaut pushed back its launch from the end of October.
Keeping Crew-2 in orbit until after the delayed Crew-3 launch was no longer an option, station managers said in the call. The Crew-2 Crew Dragon would reach its certification limit of 210 days in orbit on Nov. 19, said Ven Feng, deputy manager of the commercial crew program. While there are no known issues that would prevent the spacecraft from staying in orbit beyond that point, he said, weather “doesn’t get any better as we go further into the month, and perhaps even into December.”
In the few days between the departure of Crew-2 and arrival of Crew-3, scheduled for 7:10 p.m. Eastern Nov. 11 if it launches Nov. 10, there will still be one NASA astronaut on board. Mark Vande Hei flew to the station on a Soyuz spacecraft in April and will remain on the station until next March.
“That helped me feel more comfortable in the decision to land first before we launch,” said Joel Montalbano, NASA ISS program manager.
One advantage of the one-day docking delay is that is restores a flyaround of the station by the Crew Dragon after undocking to take images of the station’s exterior. Had the spacecraft undocked Nov. 7, Feng said, the two-hour flyaround would not have been possible to preserve more options for splashdown locations. “Adding the two hours can take out some potential landing sites” by extending the crew day beyond allowed limits, he said.
Feng said NASA was still evaluating whether to perform a flyaround if the Crew Dragon undocked Nov. 8. “It can fit in the timeline from a trajectory standpoint. We’ll just decide operationally if we want to go pursue it for this flight,” he said. NASA’s statement about the rescheduled undocking did state that the flyaround would take place.