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SpaceX Starship Program / Re: Starship hot staging
« Last post by Slarty1080 on Today at 12:15 pm »
This means the SH fuselage will experience a brief slam of negative acceleration relative to its own prop.

I was disabused of this notion back about 2,000 pages.
Without more telemetry data, or a much more serious analysis, all we can say is that the acceleration of SH was REDUCED from the pre-hot staging acceleration.  We really don't have enough information to say that it we reduced far enough to go negative.  As long as the acceleration remains at least slightly positive (say, went from +3G to +0.01G), the propellants will remain settled at the bottom of the tank.  This is the simplified view; one would also need to take into account the rotational acceleration to truly model the behavior of the propellants, but that kind of work makes my head hurt.
It's not a certisnty, but there's certainly supporting evidence, both in the vented gasses and in the slosh simulation, and also force analysis supports the idea.
And opposing the idea is that the centre engines remained lit throughout hot-staging, and all but one of the centre 13 relit after hot-staging had completed and the flip started. And that the entire reason hot-staging was implemented was to keep booster prop settled through the staging sequence without needing to re-pressurise the tanks or resettle prop.

Whatever happened that caused the last engine in the boostback reignition sequence not the light, and the lit engines to start shutting down, occurred well into the post-staging flip.
I've been noodling the issue of the three engines staying lit while purportedly experiencing negative acceleration. You know a lot more about this than I do. Could you (and everybody else for that matter) critique an idea?

For the sake of argument assume there really was a negative acceleration and let's only look at the earliest moments before the flip starts. And let's further assume the methane header holds enough that, at least initially, methane starvation is not an issue. We'll concentrate on the LOX.

The simplest of model has the LOX moving towards the common dome as a simple cylinder of fluid. But there is a force moving a portion of the lox towards the engine inlets. Inertia. It wouldn't be applied to the entire fluid cylinder. It would mostly be in the center around the downcomer and above the three center engine inlets. It would also probably be in the form of three vortexes which (I think) would help keep the inertia effects strongly localized.

The simple cylinder of fluid would most likely transform into a rough cone, apex to the inlet area with a fluid cylinder above that. This would be a strictly transient effect with a full detatch inevitable if the negative acceleration continues. Once the flip starts the LOX would go chaotic.

If I've noodled this correctly, the three center engines could keep running for a short time while the LOX was otherwise reacting to the negative acceleration. As long as we saw them running? I do not know.

If my surmise is realistic we can't rule out negative acceleration.
Can't rule out negative acceleration by accident, but I suspect it would be deadly. As soon as LOX is in motion in the head space there will be ullage collapse to some degree in the main tank. Reapplication of acceleration would slam the bulk of the LOX back against the bulk head with resulting splash back especially if any turning moment was applied. Any significant ullage collapse would lead to pressure reduction and cavitation. And even if the header tank somehow avoided this fate the pressure loss in the main tank would have robbed all of the advantages of hot staging as vast quantities of cold compressed (heavy) gas would be required to repressurise it.
Yet another partially un-redacted iteration of "UNITED STATES CRIPTOLOGIC HISTORY/American Criptology during the Cold War, 1945-1989"  is out. This one has been FOIAed by John Greenewald. "Book II: Centralization Wins, 1960-1972" includes a brief section on "The P-11 Payloads".

Attached is the TOC and the relevant section. Have fun with filling in the blanks ;-)
(for comparison, the previously released version is attached as well)
Per machine translation: The satellite launched was not in South Korea MoD’s original plans for this test flight, but rocket co-developer Hanhwa Aerospace approached them with their own SAR prototype satellite (apparently named S-STEP) waiting for a ride, and both agreed to replace the planned dummy payload with it. The MoD calls it a “win-win” situation.
So how soon we see it top of a Falcon, do you take bets?
SpaceX Reusability / Re: Progress on rapid booster reuse
« Last post by FLHerne on Today at 11:51 am »
As these boosters creep up on the 20 flight mark, does anyone think they will add more flights beyond 20?

Yes -- from Ars Technica article here:

With so many launches planned next year, 20 flights is probably not a stopping point. "We might go a little higher," the SpaceX official said.


Unrelated from another thread:
Some reusability stats for this launch (Starlink Group 6-31):

Booster B1078.6 turnaround time: 78 days 0 hours 21 minutes
(its previous mission was Starlink Group 6-16 on Sep 16, 2023 UTC).

That's kind of slow turnaround time for a relatively new Falcon 9 booster ???

I think this overlooks that booster availability isn't a constraint at the moment (except possibly the small West Coast fleet) so turnarounds aren't the minimum possible.

They could be deliberately reducing the use of low-flight-count boosters on Starlink to keep them available for pickier customers.
A second launch was conducted on Dec 3, 2023  here is the link to continue the story


The first two flights in March and December 2022, respectively, tested the performance of three engines except the first-stage booster.
Now it would be nice if we could also get the name of the vehicle.

It is up to you to name it. The rest of the world will adopt the name given on your website.
Update from NASA (December 01st, 2023):

COMMENT |       EVENT        |       TIG        | ORB |   DV    |   HA    |   HP    |
COMMENT |                    |       GMT        |     |   M/S   |   KM    |   KM    |
COMMENT |                    |                  |     |  (F/S)  |  (NM)   |  (NM)   |
COMMENT =============================================================================
COMMENT  SpX-29 Undock         348:22:00:00.000             0.0     421.4     408.3
COMMENT                                                    (0.0)   (227.5)   (220.5)
COMMENT =============================================================================

That's December 14, for those of us who don't have our Julian dates memorized.
Now it would be nice if we could also get the name of the vehicle.
Fuel operations for the Arktika-M n.º 2 have been completed at Baikonur.

The satellite will now be integrated in the launcher.
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