Author Topic: Are re-used boosters less finicky?  (Read 26402 times)

Offline meekGee

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Re: Are re-used boosters less finicky?
« Reply #20 on: 05/09/2019 09:36 pm »
Cross threading at Gongora's suggestion.



I wrote an article about the recent Starlink-1 news and I'm also speculating that SpaceX might soon stop doing static fires before Starlink launches.

https://www.elonx.net/falcon-9-will-launch-dozens-of-starlink-satellites-and-there-could-be-up-to-7-such-launches-this-year/
That would be interesting.

My view on this from a few years back was that static fires could be eliminated for reused boosters once SpaceX feels comfortable that data collected through ascent and descent is understood well enough to be used in lieu of static fire data for the following flight.

Maybe we have arrived...

Several years ago ULA stopped doing WDRs for the Atlas V (unless for military, NASA, or customer request) because they got to the point where they almost never uncovered an issue before launch.

True.  And I like how you still use "almost" in there.

The thing is, a static fire still suffers from the risk of "but what if the static fire broke something".

That, plus that ability to do real time analysis during the regular hold-down, plus the fact the a major risk factor is solid motors that can't be tested anyway - all added up to a "why bother".

With F9, it's different.  The vehicle is designed for a very large number of flights, there are no solids, and so why not?

The path to removing static fires for SpaceX is different. Once a vehicle already flew, the chance of there being a pad-detectable fault that's not already detectable in the post flight data analysis is really low, basically limited to landing damage.



Not really.  It has nothing to do with solids.    It is also has nothing to do with flight data.  ULA only took on a schedule risk with the elimination of WDRs .  If there was a problem, they would find it on the day of launch,  scrub and fix it.

A static fire or WDR is not going to uncover flight structural or thermal issues or even flight control problems.  A static fire or WDR only looks at the plumbing and environments cause by the propellants and nothing more.  It doesn't test staging, deployment or recovery systems.   Avionics can be checked out by sim flights.
Naw.

Flight data can show out-of-family or even variation-over-time for individual engines - pretty much what a static fire looks for, but over the full flight envelope.

Meanwhile  when you have solids, even if you could get full knowledge from a static fire of the main engines, you'd still be blind to defects in the solids or solid integration.

Schedule issues are just an added layer on top of this.  Reliability generally trumps schedule, unless the test doesn't help with reliability - which is what happened.
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Offline LouScheffer

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Re: Are re-used boosters less finicky?
« Reply #21 on: 06/15/2019 10:32 pm »
Looking again at this, now with more data.   This just counts scrubs due to booster problems, not upper level winds, weather, etc.

Booster scrubs mission
1046.1       1 Bangabandhu
1047.1       0 Telstar 19
1048.1       0 Iridium/Grace
1046.2       0 Merah Putih
1049.1       0 Telstar 18
1048.2       0 SAOCOM
1047.2       0 Es'hail
1046.3       0 SSO-A
1050.1       0 CRS-16
1054.1       1 GPS-III
1049.2       0 Iridium
1048.2       0 Nusantara Satu
1051.1       0 SpX-Dm1
1052.1       0 FH
1053.1       0 FH
1055.1       0 FH
1056.1       0 CRS-17
1049.3       0 Starlink
1051.2       0 RADARSAT


So there have been 11 new and 8 used launches, and overall 2 of 19 (10.5%) had a technical scrub due to the booster(s) during countdown.  If two scrubs were evenly distributed among the 19 launches, we would naturally expect both on new boosters 55/171 (32%) of the time, both on used boosters 28/171 (16.3%) of the time, and one each 88/171 (51%) of the time.

Clearly the numbers are still small, and not statistically significant, but the evidence points slightly in the direction of used boosters having fewer scrubs.  On the other hand, the number of booster-related scrubs per mission seems to be decreasing in general, so it may not be possible to measure this with certainty.

Online FutureSpaceTourist

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Re: Are re-used boosters less finicky?
« Reply #22 on: 06/16/2019 06:30 am »
I think we can at least say that whatever amount of refurbishment is needed, SpaceX is doing enough to ensure launches proceed without issue post static fire. Only if/when times between reuses become small can we be confident that there is little refurbishment and thus be more confident that reused boosters likely are less finicky. I’m hoping that an increasing frequency of Starlink launches in the coming months/year may provide that evidence.

Offline aero

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Re: Are re-used boosters less finicky?
« Reply #23 on: 06/16/2019 05:51 pm »
At 60 satellites per launch, how many launches are required per phase?

When launching with the Starship, how many launches per plane? Or per phase if that is the metric.
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Offline joek

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Re: Are re-used boosters less finicky?
« Reply #24 on: 06/16/2019 06:25 pm »
At 60 satellites per launch, how many launches are required per phase? ...
Depends on what you mean by "phase".  In any case, better asked (and likely already answered) in Starlink threads here and here (among others).

Offline Jim

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Re: Are re-used boosters less finicky?
« Reply #25 on: 06/16/2019 08:07 pm »
Flight data can show out-of-family or even variation-over-time for individual engines - pretty much what a static fire looks for, but over the full flight envelope.

Wrong again.  Flight envelope has no bearing on engine performance. 

Meanwhile  when you have solids, even if you could get full knowledge from a static fire of the main engines, you'd still be blind to defects in the solids or solid integration.

Meh.  Meaningless.  In over 1200 flights of monolithic composite cased SRMs on Delta II, IV and Atlas V, only one had a failure.  Meanwhile, Falcon 9 had an inflight failure of a Merlin, even after static firing as stage twice. 

Schedule issues are just an added layer on top of this.  Reliability generally trumps schedule, unless the test doesn't help with reliability - which is what happened.

And it has been shown that static test is also in this category.  And static test itself has lead to a mission loss.

« Last Edit: 06/16/2019 08:08 pm by Jim »

Offline zodiacchris

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Re: Are re-used boosters less finicky?
« Reply #26 on: 06/16/2019 08:27 pm »
Shouldn’t you include the Shuttle solids and Challenger in there Jim?  ??? Still makes it only one failure in 1300 flights, but what a failure it was...

Offline meekGee

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Re: Are re-used boosters less finicky?
« Reply #27 on: 06/16/2019 08:46 pm »
Flight data can show out-of-family or even variation-over-time for individual engines - pretty much what a static fire looks for, but over the full flight envelope.

Wrong again.  Flight envelope has no bearing on engine performance. 

Meanwhile  when you have solids, even if you could get full knowledge from a static fire of the main engines, you'd still be blind to defects in the solids or solid integration.

Meh.  Meaningless.  In over 1200 flights of monolithic composite cased SRMs on Delta II, IV and Atlas V, only one had a failure.  Meanwhile, Falcon 9 had an inflight failure of a Merlin, even after static firing as stage twice. 

Schedule issues are just an added layer on top of this.  Reliability generally trumps schedule, unless the test doesn't help with reliability - which is what happened.

And it has been shown that static test is also in this category.  And static test itself has lead to a mission loss.

Love it how you start with "wrong again" without even properly reading what's written.  It's like you have a message template that starts with that...

Things are changing Jim.  Instead of nit-picking, maybe you should address the core proposition here, which is that with a reusable vehicle, flight data from the previous launches gives them a previously unthinkable amount of data about the health of the system, which can be used as absolute metrics, for trend analysis, for in-family analysis - applied to the very specific system that's about to re-fly.

This is unprecedented, and completely different from "focus on process control during manufacturing and hope for the best" which is how expendables work.

Nobody gives a damn if there are a few failures while this transition is happening. There were far, far more failures during the development of expendable rockets, and the resultant ecosystem proved unable to innovate and move forward.

The future belongs to reusable vehicles with a high level of redundancy, not to expendables with a bunch of strap-ons and two main engines.
« Last Edit: 06/16/2019 10:35 pm by meekGee »
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Offline LouScheffer

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Re: Are re-used boosters less finicky?
« Reply #28 on: 06/16/2019 09:43 pm »
Compared to the Delta-4, the  Falcon 9 has relatively few post-rollout delays.  From the beginning of 2016

Mission  scrubs
NROL-45    0
NROL-37    0
AFSPC      0
WGS-8      0
WGS-9      1
JPSS-1     1
NROL-47    1
PSP        1
NROL-71    3
WGS-10     1

This could potentially be due to lack of practice, hydrogen fuel (often thought to be finicky), or design.

It would be great to have the same figures for other launchers.   My intuitive guess would be that the shuttle was finicky, Atlas and Ariane are quite good, and Soyuz has the fewest technical delays.

Offline meekGee

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Re: Are re-used boosters less finicky?
« Reply #29 on: 06/17/2019 01:34 am »
Compared to the Delta-4, the  Falcon 9 has relatively few post-rollout delays.  From the beginning of 2016

Mission  scrubs
NROL-45    0
NROL-37    0
AFSPC      0
WGS-8      0
WGS-9      1
JPSS-1     1
NROL-47    1
PSP        1
NROL-71    3
WGS-10     1

This could potentially be due to lack of practice, hydrogen fuel (often thought to be finicky), or design.

It would be great to have the same figures for other launchers.   My intuitive guess would be that the shuttle was finicky, Atlas and Ariane are quite good, and Soyuz has the fewest technical delays.

The interesting thing about this sequence is that the problems are definitely not clustered around the beginning of the timeline - they're in fact clustered around the end.
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Offline tdperk

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Re: Are re-used boosters less finicky?
« Reply #30 on: 06/20/2019 08:24 pm »

Flight envelope has no bearing on engine performance. 

An objectively and obviously wrong claim.

Why do you think there are different Isp's for sea level and vacuum?

Offline spacenut

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Re: Are re-used boosters less finicky?
« Reply #31 on: 06/20/2019 09:44 pm »
Jim said monolithic solids, like the strap on one piece solids on Atlas V and Delta IV, and Delta II.

Shuttle solids were 4 individual casings bolted together.  Failure was between the casings on Challenger. 

Also, SpaceX having one engine failure with no loss of mission with 9 individual liquid engines. 

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Re: Are re-used boosters less finicky?
« Reply #32 on: 06/20/2019 11:34 pm »
The interesting thing about this sequence is that the problems are definitely not clustered around the beginning of the timeline - they're in fact clustered around the end.

IIRC a number of issues have been GSE related. I think this is a combination of ageing infrastructure and lack of/reduced investment in the infrastructure due to forthcoming replacement by Vulcan. So different issues to the focus of this thread.

Offline meekGee

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Re: Are re-used boosters less finicky?
« Reply #33 on: 06/21/2019 12:53 pm »



Flight envelope has no bearing on engine performance. 

An objectively and obviously wrong claim.

Why do you think there are different Isp's for sea level and vacuum?

Not only that, but back when grasshopper was proving reusability and was planning high altitude flights, Jim constantly argued that it will prove nothing because "the flight envelope is not the same".

Now that it is the same, it is suddenly nothing new or important because "flight envelope has no bearing".

Shrug.
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Offline su27k

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Re: Are re-used boosters less finicky?
« Reply #34 on: 07/24/2019 02:57 pm »
This may have some bearing here, too bad nobody asked if this issue is related to reuse:

Jessica talking about Static Fire issues.

Sensors on Stage 1 detecting a small LOX leak. Inspection and repair occurred. Took a couple days.  That static fire occurred on Friday.

Offline intelati

Re: Are re-used boosters less finicky?
« Reply #35 on: 07/24/2019 03:01 pm »
This may have some bearing here, too bad nobody asked if this issue is related to reuse:

Jessica talking about Static Fire issues.

Sensors on Stage 1 detecting a small LOX leak. Inspection and repair occurred. Took a couple days.  That static fire occurred on Friday.

There is some conversation in L2.

I don't think anything is official, but it certainly quacks like a duck...

But still, the reused boosters still have quite the record for reliability.
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Offline speedevil

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Re: Are re-used boosters less finicky?
« Reply #36 on: 08/01/2019 11:31 pm »
It occurred to that the margin available for reuse of the booster might allow a complete recovery under nearly all circumstances from a single engine out.
If an engine fails, you end up not recovering the payload, not it missing its orbit.

Offline LouScheffer

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Re: Are re-used boosters less finicky?
« Reply #37 on: 08/07/2019 04:18 pm »
Looking again at this yet again.   This just counts scrubs due to booster problems, not upper level winds, weather, etc.

Booster scrubs mission
1046.1       1 Bangabandhu
1047.1       0 Telstar 19
1048.1       0 Iridium/Grace
1046.2       0 Merah Putih
1049.1       0 Telstar 18
1048.2       0 SAOCOM
1047.2       0 Es'hail
1046.3       0 SSO-A
1050.1       0 CRS-16
1054.1       1 GPS-III
1049.2       0 Iridium
1048.2       0 Nusantara Satu
1051.1       0 SpX-Dm1
1052.1       0 FH
1053.1       0 FH
1055.1       0 FH
1056.1       0 CRS-17
1049.3       0 Starlink
1051.2       0 RADARSAT
1057.1       0 STP-2
1052.2       0 STP-2
1053.2       0 STP-2
1056.2       0 CRS-18
1047.3       1 AMOS-18 (extra static fire needed)


So there have been 12 new and 12 used launches, and overall 3 of 24 (12.5%) had a technical scrub due to the booster(s) post rollout.  If three scrubs were evenly distributed among the 24 launches, we would naturally expect all on new boosters 220/2024 (11%) of the time, all on used boosters 220/2024 (11%) of the time, and two of one, one of the other each  792/2024 (39%) of the time.  So most likely, based on limited samples, there is little difference in finickyness between new and used boosters.


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Re: Are re-used boosters less finicky?
« Reply #38 on: 06/05/2020 02:50 pm »
This extract from the recent Discovery documentary talks about reuse generally but also includes a segment with Elon talking To Jim Bridenstine about insurance rates etc


Offline oiorionsbelt

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Re: Are re-used boosters less finicky?
« Reply #39 on: 06/09/2020 01:15 am »
This comment doesn't fit here that well but I didn't see a better place and the picture illustrates well.
 I'm surprised that the returned F9's are both sooty and shiny.
 Do they "polish" them?
 If yes, is that more finicky?

Whew, on topic in the end.

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