[AR] Re: starship abort?
- From: David McMillan <skyefire@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 22 Apr 2023 12:18:47 -0400
On 4/22/2023 11:46 AM, Andre wrote:
Hi, there seem to be a few who blame some of the debris coming off the rocket
as failing hydraulic powerpacks. I wonder though if the pad debris did not
cause some turbopumps to fail catastrophically and exit via the side skirt. I
base this assumption an the continued vapour escaping from engine area during
the latter high AOA of the rocket. I would assume it to be possible for some
feed lines to have been breached. May explain continued flames not looking like
rocket engine plumes? There must have been tens of tons of debris being thrown
around.
Andre
Obviously, we are all just speculating on extremely limited data.
But what we /do/ know is:
1. The first few seconds of liftoff threw a /lot/ of debris around, and
some of it was heavy and fast enough to do significant damage.
2. Three engines were shown as "dead" in the telemetry as soon as that
part of the stream started -- several seconds /after/ ignition, I'll
note. Also worthy of note is that the telemetry display did not
always match the visible engines, /and/ the telemetry showed an
outer-ring engine going out, then coming back. But IIRC, none of
the outer-ring engines are capable of in-flight restart. So, we
need to take the engine telemetry display with a grain of salt.
3. At least one of the HPUs certainly appeared to fail rather violently
in flight.
4. There was exhaust discoloration that seemed to hint at combusting
hydraulic fluid, oxygen-rich combustion, engine-rich combustion, or
some combination of all three
5. The telemetry seemed to show LOX being consumed faster than methane.
The engines out at liftoff could simply be Raptors that failed to
ignite -- we know SpaceX hasn't gotten that 100% ironed out yet. But
given the amount of debris being thrown around, that debris is certainly
the prime suspect -- it's entirely plausible that shrapnel damaged the
HPUs, some Raptors, and/or various plumbing.
But, it's also entirely plausible that the extreme vibration
environment of 30 Raptors at 100% throttle found a weak spot in the
plumbing that the earlier static-fire tests didn't.
What we /can/ be sure of is that SpaceX, now having a lot more
actual flight-conditions data, will be /massively/ upgrading the pad
(they've been planning to do so anyway, but it sounds like they honestly
expected the high-strength concrete to withstand at least /one/ flight),
and going over all the telemetry data with a fine-tooth comb.
I have to say, though, this is one /tough/ ship. Of course, re-use
requires durability, but it was still pretty dramatic watching the FCS
fight to keep control authority right up until the end (almost as
impressive as Astra's "moonwalk"), and watching the whole stack hold
together through nearly 2 or 3 full flips before the interstage failed
and the FTS triggered. It'll be interesting to find out if the flipping
started with an attempt to start the stage-separation "toss" maneuver,
or it was just the FCS losing control authority completely when the last
of the hydraulic fluid bled out. Given how the entire stack seemed to
be "mushing" laterally during later ascent, my off-the-cuff guess is
that the FCS was keeping the gimballed engines well over to one side to
deal with the off-center thrust of the failed engines, and when the
hydraulics gave out they were stuck that way and started the cartwheel.
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