On 3/25/2021 4:30 PM, Alain Fournier wrote:
Has anyone heard anything about what caused the premature relaunch of
SN10. Relaunches are usually after much more than a few minutes or
within a few seconds of landing (for the relaunches of the SN10 type
leading to RUD).


Nothing specific, but there was rampant speculation out there that
either a connection line or the main propellant methane tank itself
became damaged because of the hard landing causing an uncontrolled
methane leak that eventually accumulated enough around the damaged
rocket that was set off by an extant fire that started on the way back
down prior to landing and was never completely extinguished. The root
cause of that fire also remains a mystery.

Another line of speculation thought that perhaps the tank let go due to
structure failure first *before* the explosion that was subsequent.

As for the cause of the hard landing itself, Elon has tweeted about
that, you can read the whole thing he

https://www.teslarati.com/spacex-sta...ion-explained/

Several design changes in the works for SN11. I suspect a total re-think
of the helium pressurization setup for the header tanks. Perhaps some
new form of autogenous pressurization, along the lines of a cascade dual
pressurization scheme, whereby the header tanks are placed under higher
pressure than before from the engines and then that is used to prevent
ullage slosh, while the engines are off during the belly flop. Not sure
why Elon went the helium route in the first place on SN9/SN10. It's
going to be more complex in some ways than the helium scheme but
hopefully and somewhat un-intuitively more reliable.


I'm wondering, will this lead to something like don't start servicing a
Starship less than several hours after landing to let the engines cool
down or what not. Or maybe it will lead to keep this valve closed after
landing.

Some have speculated on flaring the methane after landing. Which would
look incredibly cool (I mean hot, heh). When I was a kid, seeing the
verniers firing on the old Atlas was one of the coolest (hotest?)
features of an Atlas launch in my opinion at the time:

https://i1.wp.com/everydayastronaut....-Thrusters.jpg

Having the methane flared off would look similar, but on an otherwise
stationary Starship.


If SpaceX ends up delaying servicing returning vehicles for several
hours, it isn't really a big deal. But still, they seem to want to go
for a very rapid turnaround, so if they could trim those several hours
from the refurbishment time, it can make it even more cool.


Flaring off the methane would be even more hot. :-) Might be not only
the quickest way to depress the tanks but also the safest! Methane wants
to misbehave a bit after agitation. Not as bad as hydrogen, but he's not
trying to land a hydrogen rocket.

Dave