Gwynne Shotwell, president of SpaceX, told a post-scrub press conference that the failure to launch Falcon9-Dragon to the International Space Station early May 19 was “aborted with purpose” and so not a failure.
Regardless, the next launch attempt has been postponed until at least May 22 at 3:44 a.m., EDT. May 23 provides another possible launch time.
All was nominal until 0.5 seconds before liftoff, but the software monitoring the health of the Falcon 9 systems detected higher than normal chamber pressure for engine 5 of the nine-engine launcher – and the trend was upward.
The launch was stopped, and the system started “detanking,” as planned. “We aborted with purpose. It would be a failure if we were to have lifted off with an engine trending in this direction,” Shotwell said.
“The software did what it was supposed to do” this was not a software problem, she added. She attributed the higher pressure to higher temperature in the chamber, as a result of low flow of one of the propellant fluids; but said the pre-valve did fully open.
Evidently, engine 5 also did show high pressure in the hot fire hold down test just completed.
SpaceX chief technical officer and founder Elon Musk, tweeted “Launch aborted: slightly high combustion chamber pressure on engine 5. Will adjust limits for countdown in a few days.”
Shotwell pointed out that another Falcon 9 was on hand at SpaceX’s Launch Complex 40. She said that if needed, engine 5 could be swapped out with the one on this booster, and also that a May 23 launch would be feasible.
Launch to the orbiting International Space Station is efficient only at a given moment.
This time is when the ISS orbit puts it over the launch location. These times comes separated by several days, and then at intervals usually of each 2 or 3 days. The ISS orbital track projections on the earth look like the elongated S curves visible on the displays shown in the ISS control room images. After May 23, the next launch time will be in early June.