Crew-2 parachutes
An infrared image of the Crew Dragon descent on the Crew-2 mission Nov. 8, with one of the four parachutes not fully deployed. That parachute did deploy about 75 seconds after the others, and NASA and SpaceX said similar behavior had been seen in previous tests. Credit: NASA TV

WASHINGTON — NASA and SpaceX are studying why parachutes on two consecutive Dragon missions opened late but said they don’t believe the issue poses a safety risk.

Officials said at a Feb. 4 briefing that it’s possible that the delayed opening of one of four parachutes on both the Crew-2 splashdown Nov. 8 and the CRS-24 cargo mission splashdown Jan. 24 may be an artifact of the aerodynamics of those parachute systems, but they will examine the phenomenon in more detail before the next Dragon missions.

Steve Stich, NASA commercial crew program manager, said that lagging parachute on the CRS-24 mission opened 63 seconds after the other three, compared to 75 seconds on the Crew-2 splashdown. He added lagging parachute openings had been seen on earlier cargo missions but did not identify specific ones. Bill Gerstenmaier, vice president of build and flight reliability at SpaceX, later suggested those earlier incidents involved a different version of the parachutes than the Mark 3 parachutes used on the current Dragon spacecraft.

“This lagging parachute phenomenon is something we see with these large ringsail parachutes,” Stich said. “What we think — and this is just a theory at this point — is that aerodynamically the three other canopies may sort of shade, if you will, one of the other canopies, and it just struggles to inflate at times.”

Because this happened on two consecutive missions, he said, NASA and SpaceX are taking extra time to inspect the parachutes and examine other data from those missions. “So far we don’t see anything that looks strange in any of the imagery, or off-nominal.”

The delayed opening of the fourth parachute did not affect the descent of either capsule. “If you looked at the actual data, you wouldn’t even detect the fact these chutes that we saw on Crew-2 and on CRS-24 were actually late,” Gerstenmaier said. “If you look at the descent data, it looks just like a regular four-chute parachute return.”

He said that, even when not fully inflated, the fourth parachute is still providing some drag. Dragon is designed to splash down safely if one parachute of four does not open at all.

Gerstenmaier said there’s been no recent design or manufacturing changes that might explain why the lagging parachute was seen on two consecutive missions. “This will be thoroughly investigated,” he said. “We’ll use this as another data point and see if we can get smarter about how these systems operate so we can make sure that, yes, this really is a nominal operation of this four-chute system, or maybe there’s something here that’s going on that’s different.”

Stich said there was nothing to suggest there needed to be a delay in the launch of the next Crew Dragon mission, Crew-4, currently scheduled for April 15. The agency and SpaceX expect to close out the issue by the flight readiness review for that mission in early April. Gerstenmaier said the chute issue would also be closed out before the launch of a Crew Dragon on the Ax-1 commercial mission to the station, scheduled for March 30.

Stich added that NASA did not consider the issue serious enough that it would have switched to Boeing’s CST-100 Starliner commercial crew vehicle for the next crew rotation mission had that spacecraft been certified by now. SpaceX plans to share its parachute data with NASA and Boeing as both Starliner and Orion also use large ringsail parachutes, but with different configurations.

While the Crew-2 splashdown was broadcast live, allowing everyone to see the lagging parachute, the CRS-24 splashdown was not broadcast and NASA has not released any images or video of its splashdown. Kathy Lueders, NASA associate administrator for space operations, said the agency isn’t broadcasting cargo mission splashdowns to save the costs of deploying the assets needed for such coverage.

Lueders, though, said the agency would return the earlier practice of holding post-splashdown media briefings. “These are the nation’s missions, and we want to make sure that you’re understanding that we’re providing the data we need to be able to make sure that our nation understands what’s going on on their missions.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...