Author Topic: SpaceX customers' views on reuse  (Read 150059 times)

Offline oldAtlas_Eguy

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Re: SpaceX customers' views on reuse
« Reply #560 on: 07/15/2018 07:58 PM »
All B5 cores can serve as a FH center core. This was confirmed a few weeks ago.
Do you have a source for that? The only public information tells us that any B5 F9 first stage can be used as a FH side-boorster, but that FH cores are very different.

There is public information that block 4 S1 can be converted to a block 4 FH booster, and that the block 4 FH core was a special build. There is no such information for block 5, but I can tell you from my analysis of the FH demo mission that the core stage either had a lot of unused propellant, or it had a lot more dry mass than a regular block 4 stage. Similarly, from the block 5 Bangabandhu-1 mission, either it ran at less than 100% thrust, and also had a lot of unused propellant, or it had a similar dry mass to the FH demo core stage. This is admittedly not hard proof, but I do suspect that all block 5 first stages are structurally similar. This may have been deemed necessary to meet the 1.4 factor of safety requirement for the commercial crew program.
Yes it would make sense to use a BLK5 structure design for the FH demo core but we do not have any confirmation on that. Plus they would need to do a demonstration on the BLK5 structure changes including a qual test of structure strength. It definitely would make sense to combine this use of the FH demo core flight as another data point to validate the dry weight/structure for BLK5 prior to a full up BLK5 operational flight. They would even gather landing data related to the problems with landing a heavier stage.

But we still do not have any real confirmation on our sensible conclusions.

It is still possible that the FH core tank is still heavier and stronger than a standard BLK5, but with all the same other hardware.

So now back to customers views on reuse.

The customers want a large baseline (flights) of a single design and not significant variants. Having a FH core stage as a significant variant from the standard BLK5 would make customers uncomfortable with using a stage that would have very low flight numbers and not fly very often (a couple of times a year as in 1 to 4 vs F9 standard BLK5 at 20 to 50 times a year).

Offline john smith 19

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Re: SpaceX customers' views on reuse
« Reply #561 on: 07/19/2018 05:48 AM »
So now back to customers views on reuse.

The customers want a large baseline (flights) of a single design and not significant variants. Having a FH core stage as a significant variant from the standard BLK5 would make customers uncomfortable with using a stage that would have very low flight numbers and not fly very often (a couple of times a year as in 1 to 4 vs F9 standard BLK5 at 20 to 50 times a year).
That's the issue. As usual it's back when does "small changes" become "complete redesign" ?

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Offline FutureSpaceTourist

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Re: SpaceX customers' views on reuse
« Reply #562 on: 08/03/2018 02:02 AM »
As far as Im aware its not yet been announced that the Merah Putih launch is the first block 5 re-use and yet:

And I have visual confirmation from Tom Cross that the booster is indeed sooty and thus B1046.2 :) photos incoming.

Edit: the tweet!
https://twitter.com/_TomCross_/status/1025074341040533504



Offline JamesH65

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Re: SpaceX customers' views on reuse
« Reply #563 on: 08/03/2018 11:57 AM »
So now back to customers views on reuse.

The customers want a large baseline (flights) of a single design and not significant variants. Having a FH core stage as a significant variant from the standard BLK5 would make customers uncomfortable with using a stage that would have very low flight numbers and not fly very often (a couple of times a year as in 1 to 4 vs F9 standard BLK5 at 20 to 50 times a year).
That's the issue. As usual it's back when does "small changes" become "complete redesign" ?

Same as any other rocket manufacturer. They all change some bits after each flight as they find issues. I bet even some smaller parts are 'completely redesigned', rather than just modified. As for when the cummulative total of all these changes means its actually a a new rocket, well, that's a matter of opinion. When the manufacturer says so would be mine.

Offline FutureSpaceTourist

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Re: SpaceX customers' views on reuse
« Reply #564 on: 08/03/2018 01:14 PM »
For completeness of this thread (and as noted by crandles57) NSFs SAOCOM 1A article 2 days ago about the first West Coast RTLS launch includes:

Quote from: https://www.nasaspaceflight.com/2018/08/saocom-1a-ships-vandenberg-falcon-9-first-west-coast-rtls/
The booster that will be used to perform the first land landing on the west coast is B1048.2 which previously flew Iridium-7 on July 25th. The change to a flight-proven booster was finalized only a few weeks ago.

Offline Nomadd

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Re: SpaceX customers' views on reuse
« Reply #565 on: 08/03/2018 02:41 PM »


The customers want a large baseline (flights) of a single design and not significant variants. Having a FH core stage as a significant variant from the standard BLK5 would make customers uncomfortable with using a stage that would have very low flight numbers and not fly very often (a couple of times a year as in 1 to 4 vs F9 standard BLK5 at 20 to 50 times a year).
Maybe you can't fly a standard F9 as an FH core, but is there any reason they can't use an FH core as an F9? A few extra tons of dry weight isn't going to affect payload that much.
« Last Edit: 08/03/2018 02:42 PM by Nomadd »

Offline Tomness

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Re: SpaceX customers' views on reuse
« Reply #566 on: 08/03/2018 03:02 PM »


The customers want a large baseline (flights) of a single design and not significant variants. Having a FH core stage as a significant variant from the standard BLK5 would make customers uncomfortable with using a stage that would have very low flight numbers and not fly very often (a couple of times a year as in 1 to 4 vs F9 standard BLK5 at 20 to 50 times a year).
Maybe you can't fly a standard F9 as an FH core, but is there any reason they can't use an FH core as an F9? A few extra tons of dry weight isn't going to affect payload that much.
How about on that token, you need FH Booster, convert, you need F9 convert again. maybe that could swap them or just keep FH stored.

Offline edzieba

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Re: SpaceX customers' views on reuse
« Reply #567 on: 08/07/2018 03:20 PM »


The customers want a large baseline (flights) of a single design and not significant variants. Having a FH core stage as a significant variant from the standard BLK5 would make customers uncomfortable with using a stage that would have very low flight numbers and not fly very often (a couple of times a year as in 1 to 4 vs F9 standard BLK5 at 20 to 50 times a year).
Maybe you can't fly a standard F9 as an FH core, but is there any reason they can't use an FH core as an F9? A few extra tons of dry weight isn't going to affect payload that much.
How about on that token, you need FH Booster, convert, you need F9 convert again. maybe that could swap them or just keep FH stored.
That depends on just how much of a F9 needs to be changed to create a FH centre core.
If it's just a matter of replacing components of the (bolt together) Octaweb and swapping out the interstage for one with the pusher hardware - i.e. the same sort of 'conversion' to turn a regular F9 core to a FH side core - then potentially any core can become a FH centre core just as any core can become a FH side core. This was rumoured from a few different sources, but has been shot down recently by Elon.
If the actual tank structure of an FH centre core is significantly strengthened from a regular F9 or FH side core, then while you could in theory swap in regular F9 octaweb and interstage hardware (or at the very least, swap in the specific octaweb segments that contain the 'missing' holddowns), then not only would you be losing some margin from lugging around that extra structural mass but you risk a core that cannot be as easily subbed out for another as is possible with a 'standard' core.

Offline sghill

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Re: SpaceX customers' views on reuse
« Reply #568 on: 08/10/2018 12:38 AM »
Quote from: john smith 19

From the customers PoV reuse only matters to them when it
a) Changes the price over a new build booster
b) Changes the reliability WRT  a new build booster.

You left out a critical 3rd one.

C) Changes booster availability and launch dates.

A customer who can launch their bird this year or next on a used booster is going to save millions over the carrying cost of waiting several years with their payload in storage for an assembly line to churn out a new one.
« Last Edit: 08/10/2018 12:42 AM by sghill »
Bring the thunder Elon!

Offline Lar

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Re: SpaceX customers' views on reuse
« Reply #569 on: 08/10/2018 02:27 AM »
the one failure (not crash, failure) was from a development/test flight, not a production one, since the FH center core was coming back from a much tougher flight regime.
Much tougher? Wouldn't that have an effect on the stress and thermal loads, rather than engine reignition?
ISTR statements by SpaceX that the center core ran out of starter fluid because earlier starts used more, and that was because they had to start the engines during a tougher flight regime.

So yes, what I said was correct.

But too much FH failure analysis is probably off topic.
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