Author Topic: F9 Second Stage Reusability  (Read 99763 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.

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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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).

Online 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.

Offline 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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Offline Hotblack Desiato

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Re: F9 Second Stage Reusability
« Reply #529 on: 12/23/2017 09:05 AM »
Just as a fun idea...

It's still somewhat unknown what SX wants to do with the FH demo launch (yes, a Tesla Roadster to Mars...). There have been somewhat cryptic tweets from Musk about second stage recovery, well discussed in this thread.

If SX wanted to hide a test of the second stage recovery hardware, they'd need a launch of a F9 rocket in expendable mode, so there is enough margin to carry the extra mass of the second stage. Just like the Iridium-4 launch yesterday.

Of course, it would be useless for F9, since they'd have to decide whether they should discard the first or the the second stage, and could only be done for the block III first stage in a reflight (as they'd get retired after that anyways). But there is Falcon Heavy around the corner.

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Re: F9 Second Stage Reusability
« Reply #530 on: 12/23/2017 01:57 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.

We know it's true now.

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.  :(

S2 is smaller than S1. It is not clear to me that more floor space is required, just some reorg. As the number of S1s built goes down, the number of S2 should be able to go up by far more than 1:1...
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Offline Cheapchips

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Re: F9 Second Stage Reusability
« Reply #531 on: 01/04/2018 09:37 AM »

Once the BFR chomper is flying you could use a single BFR launch to recover multiple Falcon S2's.  Park the S2's in a common orbit and collect them in a batches of three.  I think that fits.  It's certainly within the return weight limits.

It would save money against the projected BFR launch cost if they were reused.

Quite why you'd be flying the Falcon at that point I'm not sure.  I like the perverse nature of it though.  :)


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Re: F9 Second Stage Reusability
« Reply #532 on: 01/04/2018 04:04 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.

We know it's true now.

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.  :(

S2 is smaller than S1. It is not clear to me that more floor space is required, just some reorg. As the number of S1s built goes down, the number of S2 should be able to go up by far more than 1:1...
As a BTW note:
The 70 flights per year assumes the following conditions:
10 total flights per booster
max production of 20 S2 and 20 S1
ratio of 4 S2 for every S1 not built
and 6 FH flights (these cause the used booster flights to increase without requiring additional S2s
=68 flights total

If you could reuse the S2 just once for a total of 2 flights per every S2 and fly each booster 20 times then the total flights possible exactly double to 136. But even if the booster flights is 10 times each the flights could be 100 with 12 FH flights.

So unless the production line increases capability or the S2 is able to be reused the ability to reach above 100 flights per year with F9/FH is not possible.
This points out just how limiting non-fully reusability is hampering flight rate.

Added:
The perspective of using the same manufacturing resource (manpower) as currently on F9 for BFR/BFS where each BFR and BFS flies each 20 times and the manufacturing resource is able to manufacture almost 7 of each per year then the flight rate of BFR/BFS could be as high as 140.

This points further to it not being cost effective to pursue S2 reusability but to hasten the operational status of the next gen system BFR/BFS.
« Last Edit: 01/04/2018 04:27 PM by oldAtlas_Eguy »

Offline speedevil

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Re: F9 Second Stage Reusability
« Reply #533 on: 01/04/2018 05:39 PM »

Once the BFR chomper is flying you could use a single BFR launch to recover multiple Falcon S2's.  Park the S2's in a common orbit and collect them in a batches of three.  I think that fits.  It's certainly within the return weight limits.

It would save money against the projected BFR launch cost if they were reused.

Quite why you'd be flying the Falcon at that point I'm not sure.  I like the perverse nature of it though.  :)
F9 second stage fits into the BFS door.
The only situation I can see this being meaningful is if BFR is delayed to the point that BFS testing stalls, and BFS can't quite do SSTO with recovery. Unlikely.

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