Author Topic: F9 Second Stage Reusability  (Read 88256 times)

Offline dante2308

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Re: F9 Second Stage Reusability
« Reply #520 on: 07/19/2017 07:24 AM »
With BFR though, I think its not worth doing.

The reason is, that (subscale) BFR/BFS might launch in 4 years. Lets say that tinkering with F9 brings it up to 5 years, thats one year of full steam operation of F9 (and arguably, around 100 launches per year) that are on F9 instead of (subscale) BFR. Even if in these 4 years, F9 becomes fully reusable for LEO missions, that is still a very substantial number of launches that are not reusable.

Also, S2 will not be reusable the instant they try the development. Like on S1, it may take a year or two to get right. So you have to expend quite a lot of S2s anyway. And with the added delay to BFR/BFS, this becomes not worthwile very fast.

Does a reusable S2 accelerate the deployment of the constellation? I dont think so. F9 will more likely be launch pad limited instead of production limited once the production of S1 is reduced in favour of S2. The cadence on A39 shows that the 2 weeks turnaround is required for satellite processing. To get something like 50 launches a year, things have to move towards more parallel processing of payloads. There is also the range that can not support that many launches at moment. There are many many things that need to change in order to get the launch cadence for the constellation and I fear that the least of the problem is the production of S2 (non-reusable).

It seems that a larger vehicle, that can launch more sats at once is advantageous to many smaller launches on more than just launch cost kind of ways. It can also cope much better with weather delays and technical delays.

Considering that a super-heavy lift spacecraft is a monumental financial and engineering effort predicated on a primary market that does not exist (trips to mars and/or dozens of commercial satellites a month), any delay in that program is disappointing, but perhaps even advisable. An incremental program to prove out a fully reusable architecture on the F9 is fairly sensible, and as meekGee pointed out, potentially economical below GTO. I'd hate to see SpaceX attempt to iterate on a multi-hundred million dollar space dreadnought based only on simulations and fever dreams. They likely don't even have enough revenue to build and launch even one BFR so it isn't clear when it will ever pay for itself.

Secondly, SpaceX's plans are for most of their flights to be to MEO for their own internet constellation. Whatever the infrastructure requirements, they are filing that they intend to put up 1.7 million kg and over 1600 sats up in space over 6 years. We can take that as evidence that they plan to process satellites in parallel. That they need to solve an infrastructure problem doesn't mean that a reusable second stage doesn't help. Those two things are mostly independent. Either way, they will need to be launching hundreds of satellites per year long before BFR gets a static fire and the economics of the BFR are also based on a high flight rate.
« Last Edit: 07/19/2017 07:55 AM by dante2308 »

Online oldAtlas_Eguy

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Re: F9 Second Stage Reusability
« Reply #521 on: 07/19/2017 02:55 PM »
If SpaceX eliminates the HotFire test on the pad, then the recent demonstration on LC39A is that the minimum turnaround for a pad is 6 days. Ops(Launch) to Ops(HotFire). That makes the launch rate from a single pad with used boosters 1 per week. With 4 pads the max launch rate for the pads recently demonstrated for F9 is a total of 200+/yr. I do not think there will be a limitation because of pads but a limitation because of range scheduling.

Offline IanThePineapple

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Re: F9 Second Stage Reusability
« Reply #522 on: 07/19/2017 02:58 PM »
...but a limitation because of range scheduling.

I REALLY hope that the range is updating their system to make it faster to book and have more opportunities during the outage
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Online oldAtlas_Eguy

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Re: F9 Second Stage Reusability
« Reply #523 on: 07/19/2017 04:03 PM »
...but a limitation because of range scheduling.

I REALLY hope that the range is updating their system to make it faster to book and have more opportunities during the outage
The key for a fully reusable vehicle is that the limitation is a "soft" one not a "hard" system design (this includes the pads refurbishment requirements between launches and vehicle logistics getting it ready with a payload to launch). The other limitation which is addressed by full reusability is lack of hardware as in US. Without full reusability it will be difficult to do more than 70 per year without greatly expanding the manufacturing infrastructure (this includes plant floor space).

Offline deruch

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Re: F9 Second Stage Reusability
« Reply #524 on: 07/22/2017 08:19 AM »
If SpaceX eliminates the HotFire test on the pad, then the recent demonstration on LC39A is that the minimum turnaround for a pad is 6 days. Ops(Launch) to Ops(HotFire). That makes the launch rate from a single pad with used boosters 1 per week. With 4 pads the max launch rate for the pads recently demonstrated for F9 is a total of 200+/yr. I do not think there will be a limitation because of pads but a limitation because of range scheduling.

That assumes that all 4 pads are equally able to support such a sustained, fast turnaround pace.  Based on current designs, this doesn't appear to be so.  IMO, LC-39A is the only pad currently run by SpaceX that is so able, though Boca Chica is likely to as well.  Mostly, this is based on T/E and water suppression system capabilities.  But, also the HIF at LC-39A being wide enough to support fully parallelized integration flows.  Of course, should SpaceX actually run into their launch rate limits, they'll just upgrade those elements that they can/need.
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Offline guckyfan

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Re: F9 Second Stage Reusability
« Reply #525 on: 07/22/2017 10:01 AM »
We know that they have decided to upgrade LC-40 with the same type of TEL as used on LC-39A, except not FH capable. I think the HIF at LC-40 can house 2 cores. Also cores will come largely flight ready from the service facility. Second stages can be prepared elsewhere. So it would be mostly integration at the pad. The calculated 50 a year are likely in reality no more than 35, given a lot of external influences. Less on LC-39A with a lot of government launches. They could still exceed 100/year assuming a sufficiently staffed pad crew.

Online douglas100

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Re: F9 Second Stage Reusability
« Reply #526 on: 07/25/2017 03:51 PM »
We know that they have decided to upgrade LC-40 with the same type of TEL as used on LC-39A, except not FH capable...

That would be desirable especially if the strongback had throw back to reduce blast damage. But do we actually know this?
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Offline guckyfan

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Re: F9 Second Stage Reusability
« Reply #527 on: 07/25/2017 05:53 PM »
We know that they have decided to upgrade LC-40 with the same type of TEL as used on LC-39A, except not FH capable...

That would be desirable especially if the strongback had throw back to reduce blast damage. But do we actually know this?

Sorry I have no link. But I am positive it was mentioned in one of the threads.

Offline john smith 19

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Re: F9 Second Stage Reusability
« Reply #528 on: 08/28/2017 07:44 AM »
The key for a fully reusable vehicle is that the limitation is a "soft" one not a "hard" system design (this includes the pads refurbishment requirements between launches and vehicle logistics getting it ready with a payload to launch).
Indeed. The lessons of "single digit hour" swapping of dies on car production lines should inspire everyone in this subject.  It was less what could be done, than what people thought could be done. Once they had an incentive to try, things started to change. Not overnight, but eventually across the whole industry. Thanks to Jon Goff for that (very salient) example.

Quote from: oldAtlas_Eguy
The other limitation which is addressed by full reusability is lack of hardware as in US. Without full reusability it will be difficult to do more than 70 per year without greatly expanding the manufacturing infrastructure (this includes plant floor space).
Excellent point. While US's remain expendable that's really a hard limit, unless SX is prepared for step change in building out their factory (assuming they have space available, otherwise "acquire new factory space" becomes another line item.  :(  )

I like to recall that Shotwells background is in the mass car market, where 400 engines a year is not a record, it's a production failure that needs fixing.  :(
« Last Edit: 08/28/2017 07:46 AM by john smith 19 »
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