Author Topic: What could push SpaceX to reconsider F9 second stage reusability?  (Read 17338 times)

Offline wannamoonbase

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I'm just going to throw out a simple one:
It's harder than people think.

I'd love to see a reuseable second stage on the FH but so far SpaceX has not shown any interest in varying equipment if not needed.

Also, if the first stages become reuseable there could be Merlin 1D production capacity available that would be a fix cost and sitting idle if the vacuum version was also reuseable.

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Online Eric Hedman

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Third requirement is there are not other better things that the SpaceX engineers can be working on. That is the opportunity cost.

I'd say this is it. SpaceX will move as quick as they can to achieve the ultimate goal ("enabling people to live on other planets") given the human resources they have while making just enough money to cover the expenses.
If I were on the board of SpaceX and they were trying to only make just enough money to cover expenses while going after another goal, I'd vote to fire management.  The first goal is to make as much as possible doing everything they are doing.  If any activity isn't to ultimately be as profitable as possible in their line of business, the shouldn't be doing it.  That's business 101.  The ultimate goal of any business is to make money.  If they are going to enable people to live on other planets they'd better make money at it and each step of the way or they won't get too far.

Offline pathfinder_01

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The only way I see it happening is if some major demand shows up for LEO. It would be easiest to get an second stage that only does LEO and not GEO.

Offline deruch

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From Elon's reddit AMA:

Quote from: /u/MarsColony_in10years

In your recent MIT talk, you mentioned that you didn't think 2nd stage recovery was possible for the Falcon 9. This is due to low fuel efficiency of kerosene fuel, and the high velocities needed for many payloads (high orbits like Geostationary orbit). However, you also said that full reusability would be possible for the Mars Colonial Transporter launch vehicle.

What have you learned from flights of Falcon 9 that taught you

a) that reuse of its second stage won't be possible; and

b) what you'll need to do differently with MCT to reuse its second stage.

Quote from: /u/ElonMuskOfficial
Actually, we could make the 2nd stage of Falcon reusable and still have significant payload on Falcon Heavy, but I think our engineering resources are better spent moving on to the Mars system.

MCT will have meaningfully higher specific impulse engines: 380 vs 345 vac Isp. For those unfamiliar, in the rocket world, that is a super gigantic difference for stages of roughly equivalent mass ratio (mass full to mass empty).

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Offline RocketmanUS

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Third requirement is there are not other better things that the SpaceX engineers can be working on. That is the opportunity cost.

I'd say this is it. SpaceX will move as quick as they can to achieve the ultimate goal ("enabling people to live on other planets") given the human resources they have while making just enough money to cover the expenses.
If I were on the board of SpaceX and they were trying to only make just enough money to cover expenses while going after another goal, I'd vote to fire management.  The first goal is to make as much as possible doing everything they are doing.  If any activity isn't to ultimately be as profitable as possible in their line of business, the shouldn't be doing it.  That's business 101.  The ultimate goal of any business is to make money.  If they are going to enable people to live on other planets they'd better make money at it and each step of the way or they won't get too far.
SpaceX is not just looking to lower space access just by reusable rockets. They are also looking at was to lower the production cost. That is to the point they don't need high production rates to keep the cost down. They are using 3D printing, and have flown a part on F9 1st stage already. Load material, program, and press start. It was faster and they said they had a better product than the old manufacturing method. With this method they don't need high production rates. One machine can make many different parts, each being different while being cheaper and better than the old way and not needing to make more than one of each.

When we finally get RLV then the production rates go down. In the old World the cost then would go up. With new methods they will be able to make their products at a lower rate while being at a lower cost than the old way.

There is more to lowering the cost of space access that just reusable stages. Their looking at the whole process and looking to apply their new methods to other industries here on Earth. If we are to venture of into and beyond our solar system we will need new methods from what we have been doing.

So for now focusing on the Falcon US for reuse would actually take them away from a means to increasing their profits. ( They don't have tunnel vision , focusing on just one thing. )

Offline jzjzjzj

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Third requirement is there are not other better things that the SpaceX engineers can be working on. That is the opportunity cost.

I'd say this is it. SpaceX will move as quick as they can to achieve the ultimate goal ("enabling people to live on other planets") given the human resources they have while making just enough money to cover the expenses.
If I were on the board of SpaceX and they were trying to only make just enough money to cover expenses while going after another goal, I'd vote to fire management.  The first goal is to make as much as possible doing everything they are doing.  If any activity isn't to ultimately be as profitable as possible in their line of business, the shouldn't be doing it.  That's business 101.  The ultimate goal of any business is to make money.  If they are going to enable people to live on other planets they'd better make money at it and each step of the way or they won't get too far.

As Elon has said he didn't get into space because it would have the best return on investment. Also he won't make SpaceX public for some 15 years of precisely what you wrote.
Following was the quote I was unable to find when I posted my previous post:
Quote from: /u/ElonMuskOfficial
[..] I think our engineering resources are better spent moving on to the Mars system.
Basically - their (and worlds combined) engineering resources are limited and they can't just spend it on a project because it's profitable or because it's possible. They have a goal to follow. Which also is business 101.

So for now focusing on the Falcon US for reuse would actually take them away from a means to increasing their profits. ( They don't have tunnel vision , focusing on just one thing. )

Agreed. They could do a lot of things to make more profit (e.g. produce drywall) but they have sublime goal and that's what makes them tick in the first place.

Offline AncientU

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The only way I see it happening is if some major demand shows up for LEO. It would be easiest to get an second stage that only does LEO and not GEO.

Isn't a 4025 short-lived satellite constellation a 'major demand?'
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Offline GreenShrike

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2) What technology would be needed to enable cost-effective reuse?

One tech I haven't seen mentioned on-thread yet is propellant densification.

If sub-chilling works out -- along with the Merlin 1D thrust increase -- and the F9 can get another tonne or two to LEO, that would go some way to offsetting the mass of any second stage recovery kit, while maintaining the F9's current payload lift capability.
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Online AJW

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Is there any way to flip the question around?  Instead of asking how to recover 100 M1DVacs from orbit, ask what could be done with 100 M1DVacs that are already in orbit?

Offline darkenfast

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Personally, I think they will focus on other things for now, for the reasons mentioned by others above.  But I also think that they will have to do upper stage return eventually, say for the BFR.  So, some questions: if they put a heat shield on the forward end of the stage, will they be able to keep it actively stable during re-entry without it flipping around?  Second, what do they land it with?  If they use Super Dracos on the aft end, where do they put the hypergolic fuel tanks?  Would the stage tanks support enough pressure to use pressure-fed Kestral-descended motors using residual Metholox? I'm assuming that the upper stage main engines are too powerful to use for landing.   

Offline RanulfC

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Elon Musk has stated that F9 second stage reusability was not expected -- but with qualifiers that GTO/high energy orbits were too challenging.

This is probably the KEY point in that the MAIN market and design point for the F9 has always been the GTO/GEO market and the challenge and difficulty of getting a stage back from that point is currently prohibitive. IF the market/opertations were to change to make LEO a priority this would be a significant "reason" for Elon/SpaceX to reconsider the current direction but probably not enough IMHO.

Secondly as quoted from Elon:
Quote
I don't expect the Falcon 9 to have a reusable upper stage, just because the - with a kerosene-based system, the specific impulse isn't really high enough to do that, and a lot of the missions we do for commercial satellite deployment are geostationary missions. So, we're really going very far out. These are high delta-velocity missions, so to try to get something back from that is really difficult. But, with the next generation of vehicles...

As noted while Kerolox is "ok" for most uses even with propellant densification as noted above it just doesn't have enough "energy" to be efficient enough to cover the payload penalty of GTO/GEO/High-Energy recovery mass required. My personal "bias" of course would be to use densified Cryo-Propane/Lox if the Merlin-Vac could be modifed to burn such a propellant mix simply because it "fits" in the current tanks and provides a higher ISP very close to methalox given all else is equal. But the current factors are that by using the Merlin-Vac and current manufacturing and kerolox all (pretty much) common with the first stage makes the current second stage "cheap-and-easy" to build as an expendable rather than bother with attempting to reuse/recover.

(And lets face it. "Converting" the Merlin to run on Propane/LOX is probably on par with converting it to run on Methalox. IE; Might as well just go on to develop the Raptor and keep the F9 familiy the way it is. The only engine we KNOW has run on propane is the RL10 and you'd need about 5 of them to equal a single Merlin so... :) )

And none of this actually address' the mass penalty for the required recovery/reuse gear that would have to be added to the second stage and would probably STILL require a payload hit that the F9 really can't affored.

Hmmmm... Now "win/win" might be someone ELSE developing a recoverable/reusable "second" stage to be launched on the F9R first stage and basically "hiring" SpaceX to launch that...
But that's just "me" dreaming I suppose :)

Quote
These are F9/FH questions and not about the MCT.

Actually its more about F9 because for "some" cases the FH might be able actually handle the added mass, its operations costs are going to be higher no matter what which actually doesn't help the case at hand. A reusable second stage is going to end up being a SIGNIFICANT "departure" from the economics of the current stage and it is VERY unlikely that the "simple" margin allowed by the FH is going to be enough to provide incentive for SpaceX to change its path. The higher operations cost of the FH is going to provide a dis-incentive I'd think for that matter over the F9R.
.... So, your saying no speculation on the FH being able to be the basis for a micro-mini-Mars-One-ish MCT then?
(Duck and Cover! ;) )

Quote
So the two questions are:
1) What would justify reconsideration of the expendible second F9 stage 'decision'?
2) What technology would be needed to enable cost-effective reuse?

1) Major operational/market/circumstance changes that turn the focus to an easier set of needs. AKA: a change from GTO/GEO to LEO as the main "aim" of SpaceX/Market.
2) I don't see any fundamental technological challenge to second stage recovery and reuse. The mass penalty needed to do so however makes the idea "non-viable" as it moves the F9 right out of the "market" and puts the payloads onto the more expensive FH.
"Cost-Effective" is really the main point rather than justification really. What would need to "change" to make it worth SpaceX's time and effort to achieve and sustain second stage recovery and reuse.

Quote
My perspective:
Quote
A reusable second stage that returns the fairing and dispenser would make lots of sense when there are so many identical launches.  The fairing could open on one side as done on STS, or hinge back fully and then re-close.  Expendible fairings, dispensers, second stages launched week after week will be prohibitively expensive -- and the fuel to de-orbit all of this hardware (with the exception of the fairing as currently used) will need to be in the mass budget anyway.

Note: This same argument could be made for a reusable tanker second stage...

As I understood the discussion cited this would be more orientated towards LEO operations where the recovery and reuse requirements are much less than doing so from GTO/GEO? The required hardware for such a reusable/recoverable second stage capable of returning from GTO/GEO would reduce the payload significantly which would require the use of the FH for launch. Would it be "cost-effective" for SpaceX to develop and deploy a highly different (and costly) second stage along with a "regular" expendable second stage to service the GTO/GEO market? Probably not.

On the other hand Elon has mentioned orbital fuel depots and on-orbit operations in a similar context before in passing so given ENOUGH flights (market) its possible though as long as we're "in-context" it needs to be kept in mind that he WAS talking about GTO/GEO and high-energy operations NOT LEO and low energy operations :)

From Elon's reddit AMA:

Quote from: /u/MarsColony_in10years

In your recent MIT talk, you mentioned that you didn't think 2nd stage recovery was possible for the Falcon 9. This is due to low fuel efficiency of kerosene fuel, and the high velocities needed for many payloads (high orbits like Geostationary orbit). However, you also said that full reusability would be possible for the Mars Colonial Transporter launch vehicle.

What have you learned from flights of Falcon 9 that taught you

a) that reuse of its second stage won't be possible; and

b) what you'll need to do differently with MCT to reuse its second stage.

Quote from: /u/ElonMuskOfficial
Actually, we could make the 2nd stage of Falcon reusable and still have significant payload on Falcon Heavy, but I think our engineering resources are better spent moving on to the Mars system.

MCT will have meaningfully higher specific impulse engines: 380 vs 345 vac Isp. For those unfamiliar, in the rocket world, that is a super gigantic difference for stages of roughly equivalent mass ratio (mass full to mass empty).

Thanks for pointing this out :) This is significant because it moves the F9R out of the picture and points out that such a second stage would then REQUIRE the FH to launch. This is NOT a "good" thing as many people think as you're now launching, recovering, and refurbishing THREE F9Rs on every launch instead of one JUST to get a reusable second stage...

Randy
« Last Edit: 01/22/2015 05:57 PM by RanulfC »
From The Amazing Catstronaut on the Black Arrow LV:
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Offline RanulfC

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Is there any way to flip the question around?  Instead of asking how to recover 100 M1DVacs from orbit, ask what could be done with 100 M1DVacs that are already in orbit?

100 times the orbital debris problem you had BEFORE you launched (and then kept) all that "junk" in orbit? :)

Seriously, without an on-orbit infrastructure to "salvage" and repurpose the "resources" then it IS simply "junk" and having the stuff up there does no good. You'd still need to recover, recycle/refurbish the equipment "up-there" in order to use it and you also STILL have the problem of kerolox propellant not being all that efficent to use in the first place.

Elon mentiones orbital propellant depots, but seems focused more on "Mars-Direct" type operations than orbital assembly, space docks and building up the kind of infrastructure and opertations that would use ONE M1DVac let alone 100 :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Lar

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If I were on the board of SpaceX and they were trying to only make just enough money to cover expenses while going after another goal, I'd vote to fire management.  The first goal is to make as much as possible doing everything they are doing.  If any activity isn't to ultimately be as profitable as possible in their line of business, the shouldn't be doing it.  That's business 101.  The ultimate goal of any business is to make money.  If they are going to enable people to live on other planets they'd better make money at it and each step of the way or they won't get too far.

I'm glad you're not on the board, I guess.

The maximum profit for SpaceX **over the lifetime of the company** is not necessarily given by the same strategy that gives the maximum profit **this quarter** .... I think Elon is playing a long game. If SpaceX is a dominant player in a transport market that sees thousands or even hundreds of thousands of metric tonnes moving between Earth and Mars, that is going to be huge. Far more profit than we can dream of. If you also include being a dominant solar system ISP, and a dominant mars surface transport provider, and a dominant supplier of refined raw materials on mars.... the mind boggles. Musk could be the worlds first trillionaire.

As long as they make enough money to keep the wheels turning, they're fine. Maximizing profit NOW is ... not the silicon valley way. That's OldSpace thinking.

Rant over.

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Offline Lar

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Is there any way to flip the question around?  Instead of asking how to recover 100 M1DVacs from orbit, ask what could be done with 100 M1DVacs that are already in orbit?

100 times the orbital debris problem you had BEFORE you launched (and then kept) all that "junk" in orbit? :)

Seriously, without an on-orbit infrastructure to "salvage" and repurpose the "resources" then it IS simply "junk" and having the stuff up there does no good. You'd still need to recover, recycle/refurbish the equipment "up-there" in order to use it and you also STILL have the problem of kerolox propellant not being all that efficent to use in the first place.

Elon mentiones orbital propellant depots, but seems focused more on "Mars-Direct" type operations than orbital assembly, space docks and building up the kind of infrastructure and opertations that would use ONE M1DVac let alone 100 :)

Randy

Clearly there's a market for tugs that can harvest all that junk from wherever it may be and collect it in one place for safe keeping. Or in one place... for feeding into the maws of an on-orbit recycler.  Not this year. Not this decade. But someday. (Kero may be more useful as an organic feedstock than as fuel)
« Last Edit: 01/22/2015 09:00 PM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline nadreck

Is there any way to flip the question around?  Instead of asking how to recover 100 M1DVacs from orbit, ask what could be done with 100 M1DVacs that are already in orbit?

100 times the orbital debris problem you had BEFORE you launched (and then kept) all that "junk" in orbit? :)

Seriously, without an on-orbit infrastructure to "salvage" and repurpose the "resources" then it IS simply "junk" and having the stuff up there does no good. You'd still need to recover, recycle/refurbish the equipment "up-there" in order to use it and you also STILL have the problem of kerolox propellant not being all that efficent to use in the first place.

Elon mentiones orbital propellant depots, but seems focused more on "Mars-Direct" type operations than orbital assembly, space docks and building up the kind of infrastructure and opertations that would use ONE M1DVac let alone 100 :)

Randy

Clearly there's a market for tugs that can harvest all that junk from wherever it may be and collect it in one place for safe keeping. Or in one place... for feeding into the maws of an on-orbit recycler.  Not this year. Not this decade. But someday.

[prediction/pontification mode]And the first place there will be on orbit salvage operation will be geosynchronous and the above geosynchronous graveyard orbit with already over 2,000 tons of scrap[/prediction/pontification mode]
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline go4mars

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I'm glad you're not on the board, I guess.

The maximum profit for SpaceX **over the lifetime of the company** is not necessarily given by the same strategy that gives the maximum profit **this quarter** .... I think Elon is playing a long game. If SpaceX is a dominant player in a transport market that sees thousands or even hundreds of thousands millions of metric tonnes moving between Earth and Mars, that is going to be huge. Far more profit than we can dream of. If you also include being a dominant solar system ISP, and a dominant mars surface transport provider, and a dominant supplier of refined raw materials on mars.... the mind boggles. Musk could be the worlds first trillionaire.

As long as they make enough money to keep the wheels turning, they're fine. Maximizing profit NOW is ... not the silicon valley way. That's OldSpace thinking.

Rant over.
Excellent Post.  But it needs correction.  Elon said "millions of tonnes of cargo".  It frames these questions about FH upper stages or SFR's to keep quotes like that forefront in mind so I fixed your error above.  ;)

http://shitelonsays.com/transcript/spacex-seattle-2015-2015-01-15
« Last Edit: 01/22/2015 09:13 PM by go4mars »
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Offline The Amazing Catstronaut

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Rant over.
Excellent Post.  But it needs correction.  Elon said "millions of tonnes of cargo".  It frames these questions about FH upper stages or SFR's to keep quotes like that forefront in mind so I fixed your error above.  ;)


[/quote]

BFR will not be the biggest FR, nor will generation one MTC be the largest MCT. We're talking space ships here; however, we're talking a good 20 years from now, minimum.

Under this frame, F9 upper stage re-use is a distraction. F9 isn't going to stay the mainstay for long; it may even begin to slip in relevance at the end of this year/first quarter next year with the F9H(r?)'s debut. Things are going to just keep on scaling; the rocket isn't going to have a lineage as long as Soyuz purely because by the time F9 would be as old as Soyuz is in the present day, spaceflight is going to be completely unrecognisable. That's a good thing.
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Offline RocketmanUS

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@ AncientU

What could push SpaceX to reconsider F9 second stage reusability?

Something would have to stop them from developing the next generation RLV , or delayed till much later than expected. ( SpaceX started in 2002 and F9 v1.0 first launched in 2010, that is eight years, we are in 2015 so no later than 2023 is a good date to set that we should see the next generation RLV )

There would need to be enough per year LEO launches to justify it's development and for the needed added ground infrastructure to support it's landing and turn around. To little amount of flights and that extra cost per year would take away from the savings of just making a new US. So figure just how much that extra infrastructure and standing army ( personnel ) would cost per year. That would help in figuring out just how many LEO flights they would need per year.

GSO/escape would most likely still us expendable US on F9/FH if they did make a reusable US for them.


Offline pathfinder_01

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The only way I see it happening is if some major demand shows up for LEO. It would be easiest to get an second stage that only does LEO and not GEO.

Isn't a 4025 short-lived satellite constellation a 'major demand?'

Depends on how many launches that is. They are planned to be small satellites. If they are they could tag along on other flights of disposable 2nd stages.

Offline AncientU

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The only way I see it happening is if some major demand shows up for LEO. It would be easiest to get an second stage that only does LEO and not GEO.

Isn't a 4025 short-lived satellite constellation a 'major demand?'

Depends on how many launches that is. They are planned to be small satellites. If they are they could tag along on other flights of disposable 2nd stages.

EM said a few hundred kg apiece.  As a secondary payload on every flight, every year (at today's launch rate) would take 40 years to launch -- and leave you with a total mess of dead sats in bazaar orbits.  Nope, on a $10-20B project with a potential revenue stream in the $100Bs range, you don't hitch rides like cube sats do.
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