HMM: NASA and SpaceX say lagging Dragon parachute may be normal phenomenon.
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.”
A difference that makes no difference is no difference, but you would kind of like to understand what’s going on.