Author Topic: SpaceX Starship : Booster 9/ Ship 25: Starbase, TX - DISCUSSION THREAD 3  (Read 114015 times)

Online meekGee

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Do you think they will, in future, do grid fin tests earlier so that if a similar problem arises they won't have to delay launch attempt?
They've done plenty of 'wiggle tests' before. Problem is, tests can't catch issues that haven't occurred yet.
Sure, but 3?

Or more likely, only one of them caused an issue, but once they knew what to look for, they saw preliminary signs in two others.

Also let me make a wild guess that these actuators are already obsolete, and they have more of them manufactured than they actually need. 
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Online eriblo

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Do you think they will, in future, do grid fin tests earlier so that if a similar problem arises they won't have to delay launch attempt?
They've done plenty of 'wiggle tests' before. Problem is, tests can't catch issues that haven't occurred yet.
Sure, but 3?

Or more likely, only one of them caused an issue, but once they knew what to look for, they saw preliminary signs in two others.

Also let me make a wild guess that these actuators are already obsolete, and they
have more of them manufactured than they actually need.
Indeed, there might not even have been any signs of failure just the realization that there was a chance and a precautionary swap while they were at it anyway.

Offline OTV Booster

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This is interesting. From p. 13 of today's FAA Written Re-evaluation linked in the Updates thread:

Quote
Forward Heat Shield Interstage

SpaceX proposes to add an interstage to Super Heavy consisting of a forward heat shield. The forward heat shield provides thermal protection against heat produced by Starship engines start during the stage separation event. It is made of stainless steel and is approximately 30 feet in diameter and 6 feet long, weighing approximately 20,000 pounds. For some missions, the forward heat shield would be jettisoned between 30 and 400 kilometers offshore in the Gulf of Mexico. SpaceX would not recover the forward heat shield as it is expected to sink.

Emphasis added. Did we know the interstage might be expendable?
Good catch.


The range of 30 to 400km is a bit of a puzzler. I'd take 30 to be a bit below the minimum possible staging altitude and 400 to be a placeholder and not really expected. Or maybe a typo for 40km.
I think what that means is the 400 km means that it would be jettisoned right after stage sep and the 30 km would be after the boost back burn is has been completed. For the first scenario though, all of the booster engines would need to be shutdown after meco.
For the F9 staging is around 40-50km. Can somebody help with a firmer number? It varies with loft angle but not all THAT much. 400km is roughly ISS altitude.


At staging the booster still has a vertical component and AIUI, the burn kicks it higher yet. For the F9, 80 km sticks in my mind. Still think it's a typo or they don't want to paint themselves into a corner.

I'm pretty sure they're talking downrange from the launch site, not altitude.
Brain fart on my part. All I can do is quote my mentor and role model. He would say "DuH!"
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

Offline Malisk

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Why not the two hours of Friday?

I see no flights coming into Hawaii area in the 5am hour (Hawaii local time when ship is set to re-enter) but there are some the hour before and after..possibly the reason?

Offline Echo_Jex

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Do you think they will, in future, do grid fin tests earlier so that if a similar problem arises they won't have to delay launch attempt?
They've done plenty of 'wiggle tests' before. Problem is, tests can't catch issues that haven't occurred yet.
Sure, but 3?

Or more likely, only one of them caused an issue, but once they knew what to look for, they saw preliminary signs in two others.

Also let me make a wild guess that these actuators are already obsolete, and they
have more of them manufactured than they actually need.
Indeed, there might not even have been any signs of failure just the realization that there was a chance and a precautionary swap while they were at it anyway.

I know the goal is to make the whole system ambient environment proof, but with outdoor machinery in general fluid intrusion is a constant battle... There was a small rain storm between last grid fin test and parts replacement, maybe it was as simple as water ingress into the actuators
« Last Edit: 11/17/2023 05:53 pm by Echo_Jex »

Offline tgr9898

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Do you think they will, in future, do grid fin tests earlier so that if a similar problem arises they won't have to delay launch attempt?
They've done plenty of 'wiggle tests' before. Problem is, tests can't catch issues that haven't occurred yet.
Sure, but 3?

Or more likely, only one of them caused an issue, but once they knew what to look for, they saw preliminary signs in two others.

Also let me make a wild guess that these actuators are already obsolete, and they
have more of them manufactured than they actually need.
Indeed, there might not even have been any signs of failure just the realization that there was a chance and a precautionary swap while they were at it anyway.

It might have even just been some feedback/positioning sensor data that was closer to the limit than they liked on 2 or even all 3.  Given the scrutiny & the permitting delays, and extra day to be 100% sure is worth it.

Online FutureSpaceTourist

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Thread locked and IFT-2 flight discussion moved to the IFT-2 discussion thread.

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