Author Topic: Aviation week article on SpaceX reusability  (Read 3686 times)

Online LouScheffer

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Aviation week article on SpaceX reusability
« on: 06/11/2022 11:50 am »
There is a most excellent article on Aviation Week, SpaceX Building Airline-Type Flight Ops For Launch that is chock full of information. It's behind a paywall, but here are a few points:

They are now aiming at 15 flights per booster.  They do this vibrating, heating, etc. each component to 4x the expected time of exposure at 15 flights.

They are aiming at a flight every 5 days with a 21 booster fleet.

The engine boots are water-cooled and get replaced proactively.

The oxidizer transfer tube has seals (thermal expansion, I'd guess) and is being looked at carefully.

SpaceX has an airline type inspection system.  'A' check after every flight, 'B' check every 6-7 flights, 'C' check for life leaders and crewed missions.

Static fires used to be run after an engine was pulled or a turbine wheel changed.  Now only if 3 engines are pulled; turbine wheels are now monitored by accelerometers during startup, and don't force a static fire.

Even Block 5 is still evolving; examples include better thermal shields and a way to drain the second stage tanks even if the QD pops off (which would otherwise be fatal). For most changes they identify the potential improvement, then test it on the bench, then on a StarLink launch, then it becomes general.

SpaceX has had two recent-ish booster engine shutdowns (March 2020 and Feb 2021).  Both still made orbit.  The 2020 failure was cleaning fluid left in the oxygen section of the gas generator, the 2021 failure was hot gas penetrating the engine shield and eating a harness.  This was the center engine so no landing was possible.

They keep tweaking the time interval between MECO and second stage start.  The smaller the delay, the better the performance, but the more wear on the first stage.

On Starlink launches they are experimenting with dropping the fairings earlier, allowing up to 10x the normal heating (which I think is one sun).

They have two software systems tuned for re-use.  One called Hyperion looks at the telemetry and points out areas that need a closer look.  Warp, their production system, also has modifications for re-use such as pointing out similar problems that have occured on prior flights.

Lots of other tidbits.  Overall a fascinating article in the best Aviation Week tradition.



Online ThatOldJanxSpirit

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Re: Aviation week article on SpaceX reusability
« Reply #1 on: 06/11/2022 02:50 pm »
Itís so good to see how well Gerst appears to have adapted to SpaceX culture, and fascinating how frustrated he had become with the NASA way.

Offline NavierĖStokes

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Re: Aviation week article on SpaceX reusability
« Reply #2 on: 06/11/2022 03:08 pm »
Thanks for the summary. It should be noted that the full article is accessible with a free Aviation Week account.

Offline Norm38

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Re: Aviation week article on SpaceX reusability
« Reply #3 on: 06/20/2022 02:39 am »
Why would dropping the fairings earlier mean more heating? 
Isnít that a lower velocity and closer to shore?

Online gongora

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Re: Aviation week article on SpaceX reusability
« Reply #4 on: 06/20/2022 02:57 am »
Why would dropping the fairings earlier mean more heating? 
Isnít that a lower velocity and closer to shore?

More heating of the uncovered payload on Stage 2

Offline rpapo

Re: Aviation week article on SpaceX reusability
« Reply #5 on: 06/20/2022 11:03 am »
Why would dropping the fairings earlier mean more heating? 
Isnít that a lower velocity and closer to shore?
More heating of the uncovered payload on Stage 2
It's not just heating.  If you uncover the payload too soon, you also risk damage due to physical drag.
An Apollo fanboy by the time Apollo 8 launched.

Offline Jim

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Re: Aviation week article on SpaceX reusability
« Reply #6 on: 07/19/2022 02:08 pm »
Itís so good to see how well Gerst appears to have adapted to SpaceX culture, and fascinating how frustrated he had become with the NASA way.

He was the reason for the "NASA" way and was in position to affect it.

Offline meekGee

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Re: Aviation week article on SpaceX reusability
« Reply #7 on: 07/20/2022 12:11 am »
It’s so good to see how well Gerst appears to have adapted to SpaceX culture, and fascinating how frustrated he had become with the NASA way.

He was the reason for the "NASA" way and was in position to affect it.
Yup and either he found it impossible to change, or more likely it was impossible for him to see how stagnant it is while looking from the inside.

If that was all he saw and knew, then that's what he thought the universe was like.  And after a bit of time somewhere else, he came around to realize maybe there is a better way, and he now gets frustrated at the very things he used to accept.

It just shows that he's capable of changing and growing.

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Offline john smith 19

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Re: Aviation week article on SpaceX reusability
« Reply #8 on: 08/05/2022 07:48 pm »
Quote from: LouScheffer
They are now aiming at 15 flights per booster.  They do this vibrating, heating, etc. each component to 4x the expected time of exposure at 15 flights.
This is a very interesting.

So 7 years after the start of reuse a booster can manage maybe 15 flights, compared to the previous 0 reuses of all previous systems. It's very impressive what can be achieved with a constant focus on improvement.

So linearly that's a smidgeon over 2 increases per year.

[Edit Just to put this in perspective the Space Shuttle Discovery made 39 flights during its opearting lifetime. I'm not sure if the structure was at its retirement limits at that point or if they could have continued flying if the programme continued. Stage and pad turnaround times are remarkable, but F9 is still far from breaking that number of reuses but with current rate of prgress should be there by 2033]

IOW into 10s of reuses of a first stage to M6, but nowhere near the 100's (1000s?) Musk thought was possible.  That suggests the booster takes a hell of a beating

Obviously a clean-sheet design incorporating all the lessons learned from F9/FH ops will be considerably better

But how much better? On the current basis a 100 flights sound like a massive improvement.  Actual airliner relaibility is into the 10s of 1000s.


Quote from: LouScheffer
Static fires used to be run after an engine was pulled or a turbine wheel changed.  Now only if 3 engines are pulled; turbine wheels are now monitored by accelerometers during startup, and don't force a static fire.
There was a NASA project using these techniques connected to the SSME's. Seemed an excellent idea but I was never sure if they got it deployed before the programme ended.
Obviously the processors running the Merlins are much more powerful than the dual M68000's that ran the 2nd generation SSME controllers.

Quote from: LouScheffer
Even Block 5 is still evolving; examples include better thermal shields and a way to drain the second stage tanks even if the QD pops off (which would otherwise be fatal). For most changes they identify the potential improvement, then test it on the bench, then on a StarLink launch, then it becomes general.
TBH I always thought the claim that "Block 5" would be the end of F9 development was rather strange and always expected them to go on tweaking it, wheather it was announced as  new version or not.

Quote from: LouScheffer
They keep tweaking the time interval between MECO and second stage start.  The smaller the delay, the better the performance, but the more wear on the first stage.
Now this is surprising. I'd have guessed a longer coast would have given them more altitude and be beneficial. OTOH more booster damage due to earlier sustainer ignition makes perfect sense due to greater exposure to engine plume.

Quote from: LouScheffer
They have two software systems tuned for re-use.  One called Hyperion looks at the telemetry and points out areas that need a closer look.  Warp, their production system, also has modifications for re-use such as pointing out similar problems that have occured on prior flights.
NASA Goddard have done a lot of work in this area. The application of AI ("Deep learning" to some, advanced pattern recognition to others) to space operations as a way to eliminate routine eyeballing of the data and automated management-by-exception

It's good to get an idea of how an SoA launch operations centre functions.

One key area that has proved very expensive in the past (IIRC about 30% of shuttle launch costs) were misison planning. IE trajectory design and things like coupled loads analysis IE making sure the payload didn't excite dangerous resonances in the LV, and vice versa. Historically this has been very time consuming, especially when the a dangerous mode can't be fixed by changing the engine burn, or the fuel loading and the payload needs to be rebuilt.
« Last Edit: 08/10/2022 11:50 am by john smith 19 »
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