FYI everyone:
*From Spaceflight Now * *October 28, 2020*
<https://spaceflightnow.com/2020/10/>
SpaceX traces engine problem to blocked valve ahead of November crew launch
SpaceX is replacing two engines on the Falcon 9 booster set to launch four
astronauts next month on the company’s first operational Crew Dragon flight
to the International Space Station, following an investigation that
revealed a subcontractor failed to adequately clean out narrow vent ports
on multiple engines across the company’s fleet, officials said Wednesday.
NASA and SpaceX officials said they are working toward a target launch date
of Nov. 14 for the Crew Dragon mission, which will take off on top of a
Falcon 9 rocket from pad 39A at the Kennedy Space Center in Florida.
The mission, designated Crew-1, will launch NASA commander Mike Hopkins,
pilot Victor Glover, mission specialist Shannon Walker, and veteran
Japanese astronaut Soichi Noguchi on a half-year expedition on the space
station.
Managers delayed the launch of the Crew-1 mission from Oct. 31 to
investigate an engine problem that triggered an automatic abort just before
liftoff of a different Falcon 9 rocket Oct. 2 with a GPS navigation
satellite for the U.S. military. Hans Koenigsmann, SpaceX’s vice president
of build and flight reliability, said Wednesday that engineers identified a
masking treatment inadvertently left behind in the engine as the cause of
the Oct. 2 abort.
Engineers found two of the nine Merlin 1D engines on the Falcon 9 first
stage for the Crew-1 mission have the same problem.
“We’re in the process of swapping out two engines on the first stage on the
Crew-1 vehicle due to this problem, and that is in work at this time,” said
Steve Stich, NASA’s commercial crew program manager, in a conference call
with reporters Wednesday.
According to Koenigsmann, the Oct. 2 launch abort at Cape Canaveral
occurred immediately after sensors detected an unusual pressure rise in gas
generators on two Merlin engines.
“When we looked at the data, we saw that two of the engines attempted to
start early, and the auto abort prevented that,” Koenigsmann said. “And by
doing that, it prevented a possible hard start that could have been
damaging to the engine hardware.”
The Merlin engines power up with help from an igniter fluid known as
TEA-TEB — or triethylaluminum-triethylborane — that gives off a bright
green flash at the start of the ignition sequence.
“And then we have liquid oxygen, and we have kerosene, (RP-1),” Koenigsmann
said. “And you need to introduce these liquids in the right order. If you
do this in the wrong order, if you happen to throw in the liquid oxygen and
the RP-1 and the igniter fluid, then what would happen is we call it a hard
start.”
A hard start would “rattle” the engine in most cases, but could cause
damage, Koenigsmann said. “So in general, you do not want that. You want a
good startup.”
“If we see the pressure rise too early, then we know liquid is in there,
and it shouldn’t be there,” he said. “And software in the engine controller
then stops the whole process.”
https://spaceflightnow.com/2020/10/28/spacex-traces-engine-problem-to-blocked-valve-ahead-of-november-crew-launch/