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  #1  
Old March 25th 21, 08:30 PM posted to sci.space.policy
Alain Fournier[_3_]
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Posts: 548
Default SN10

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).

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.

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.


Alain Fournier
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  #2  
Old March 25th 21, 11:03 PM posted to sci.space.policy
David Spain
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Posts: 2,901
Default SN10

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

  #3  
Old March 26th 21, 05:48 AM posted to sci.space.policy
snidely
external usenet poster
 
Posts: 1,303
Default SN10

David Spain pounded on thar keyboard to tell us

Several design changes in the works for SN11.


SN11? Probably not any major change. SN15 is supposed to be the 1.1
release.

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.


It was a quick fix to the low header pressure problem of SN8, of
course. And it wasn't so supposed to be the permanent fix, so SN15
could be a *revised* autogenous pressurization scheme; after all,
they've had 3 months to do fresh engineering.

/dps

--
"This is all very fine, but let us not be carried away be excitement,
but ask calmly, how does this person feel about in in his cooler
moments next day, with six or seven thousand feet of snow and stuff on
top of him?"
_Roughing It_, Mark Twain.
  #4  
Old March 28th 21, 05:53 PM posted to sci.space.policy
Douglas Eagleson[_2_]
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Posts: 15
Default SN10

On Thursday, March 25, 2021 at 4:30:44 PM UTC-4, 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).

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.

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.


Alain Fournier


I have always wondered. variable temperatures and fuel line
diameters can cause a vapor lock in the fuel system. This is
fairly common in small aircraft engines. But the existence of this
lock does not exclude its application to rocket engines.

This dynamic at liquid O2 temperatures has been tested?
This can result in rocket detonation?
 




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