Author Topic: A new upper stage design for the Falcon family  (Read 91112 times)

Offline nadreck

Re: A new upper stage design for the Falcon family
« Reply #20 on: 09/13/2015 03:26 pm »
I wouldn't be surprised to see horizontal landing based upon Shuttle, X-37B, and Dreamchaser technology... would also be way to protect the vac engine and nozzle.  Sierra Nevada would jump at a partnership.

I would not be surprised, I would be shocked. This is SpaceX and they use landing tech they can use on Mars. No way they do horizontal landing.

By this logic if a  Methalox FH reusable upper stage is developed I expect it to have methane RCS and super RCS (ie landing engines).
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 philw1776

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Re: A new upper stage design for the Falcon family
« Reply #21 on: 09/13/2015 03:32 pm »
I just hope that SX has sufficient R&D money to develop its satellite constellation, re-useable cores and Raptor engine never mind extra for exotic F9 2nd stages.  Hardware engineering & prototyping is expensive.
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Offline guckyfan

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Re: A new upper stage design for the Falcon family
« Reply #22 on: 09/13/2015 03:53 pm »
By this logic if a  Methalox FH reusable upper stage is developed I expect it to have methane RCS and super RCS (ie landing engines).

Yes, absolutely. Though initially they may use cold gas thrusters like on the Falcon 9 upper stagae.

The landing engines: That's the biggest hole in my mental picture. It could be Super RCS as you call them. I still have the hope they can find a way to deep throttle the main engine with retracted or dropped nozzle extension to use it for landing.

Offline nadreck

Re: A new upper stage design for the Falcon family
« Reply #23 on: 09/13/2015 03:54 pm »
In the 1950's von Braum and many others foresaw a slower approach to space exploration that involved first orbiting the Earth and successfully returning, then building one or more orbital habitats, then assembling lunar and Martian expeditions at these stations and having those expeditions in turn start by digging in and setting up bases. While the actual cost to do this would have been high it would have seen an economy of scale with the numbers of common systems being built.

Musk has a stated goal that includes making that economy of scale exist so that his goal of sustainable of Earth settlement happens. If there is to be a new 2nd stage for the Falcon family, it needs to be part of that, and any development that happens for it would also have to translate to the next family.  Falcon 1 saw the Merlin (and saw it evolve fairly significantly - 3 versions). While I can't rule out a Raptor FH 2nd stage, nor can I rule out a ~5meter Raptor 1st stage, statements by SpaceX (Musk, Shotwell, etc) all suggest I should.
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 Burninate

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Re: A new upper stage design for the Falcon family
« Reply #24 on: 09/13/2015 03:59 pm »
In the 1950's von Braum and many others foresaw a slower approach to space exploration that involved first orbiting the Earth and successfully returning, then building one or more orbital habitats, then assembling lunar and Martian expeditions at these stations and having those expeditions in turn start by digging in and setting up bases. While the actual cost to do this would have been high it would have seen an economy of scale with the numbers of common systems being built.

Musk has a stated goal that includes making that economy of scale exist so that his goal of sustainable of Earth settlement happens. If there is to be a new 2nd stage for the Falcon family, it needs to be part of that, and any development that happens for it would also have to translate to the next family.  Falcon 1 saw the Merlin (and saw it evolve fairly significantly - 3 versions). While I can't rule out a Raptor FH 2nd stage, nor can I rule out a ~5meter Raptor 1st stage, statements by SpaceX (Musk, Shotwell, etc) all suggest I should.

Credible estimates of the Raptor sea level nozzle diameter are 1.6-1.8m from the previous thread.  5 meters is not big enough for seven such nozzles;  Nine nozzles would require something on the order of 7-8m.

A 2-nozzle or 3-nozzle launch vehicle would, as I understand it, not be able to land on its main engines.
« Last Edit: 09/13/2015 04:03 pm by Burninate »

Offline guckyfan

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Re: A new upper stage design for the Falcon family
« Reply #25 on: 09/13/2015 04:01 pm »
I just hope that SX has sufficient R&D money to develop its satellite constellation, re-useable cores and Raptor engine never mind extra for exotic F9 2nd stages.  Hardware engineering & prototyping is expensive.

When they have a viable concept they will have no problem getting development money for the satellite constellation.

For Raptor and BFR/MCT they already have very capable engineering teams. Cost will start to rise when they need to build the factory, tooling and launch pad for such a huge launch vehicle.

Development of the new upper stage I see as part of the development effort for their Mars architecture. Developing it will cost a lot less and reduce the development risk of MCT. And it may earn the money spent on it.

Offline nadreck

Re: A new upper stage design for the Falcon family
« Reply #26 on: 09/13/2015 04:13 pm »
In the 1950's von Braum and many others foresaw a slower approach to space exploration that involved first orbiting the Earth and successfully returning, then building one or more orbital habitats, then assembling lunar and Martian expeditions at these stations and having those expeditions in turn start by digging in and setting up bases. While the actual cost to do this would have been high it would have seen an economy of scale with the numbers of common systems being built.

Musk has a stated goal that includes making that economy of scale exist so that his goal of sustainable of Earth settlement happens. If there is to be a new 2nd stage for the Falcon family, it needs to be part of that, and any development that happens for it would also have to translate to the next family.  Falcon 1 saw the Merlin (and saw it evolve fairly significantly - 3 versions). While I can't rule out a Raptor FH 2nd stage, nor can I rule out a ~5meter Raptor 1st stage, statements by SpaceX (Musk, Shotwell, etc) all suggest I should.

Credible estimates of the Raptor sea level nozzle diameter are 1.6-1.8m from the previous thread.  5 meters is not big enough for seven such nozzles;  Nine nozzles would require something on the order of 7-8m.

A 2-nozzle or 3-nozzle launch vehicle would, as I understand it, not be able to land on its main engines.

Scaling up to say 5.2m while maintaining V1.1 fineness and going to methalox propellant would suggest a take off mass around 1,200 - 1,400t which would be best served by 7 Raptors in the 225t thrust range.  As long as you were not planning on strapping 3 of these together to make a 'heavy' version the 7 engines could be arranged similar to the 9 on an F9 with the outboard engines having about half their diameter outside the cross section of the core.
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 Burninate

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Re: A new upper stage design for the Falcon family
« Reply #27 on: 09/13/2015 04:20 pm »
In the 1950's von Braum and many others foresaw a slower approach to space exploration that involved first orbiting the Earth and successfully returning, then building one or more orbital habitats, then assembling lunar and Martian expeditions at these stations and having those expeditions in turn start by digging in and setting up bases. While the actual cost to do this would have been high it would have seen an economy of scale with the numbers of common systems being built.

Musk has a stated goal that includes making that economy of scale exist so that his goal of sustainable of Earth settlement happens. If there is to be a new 2nd stage for the Falcon family, it needs to be part of that, and any development that happens for it would also have to translate to the next family.  Falcon 1 saw the Merlin (and saw it evolve fairly significantly - 3 versions). While I can't rule out a Raptor FH 2nd stage, nor can I rule out a ~5meter Raptor 1st stage, statements by SpaceX (Musk, Shotwell, etc) all suggest I should.

Credible estimates of the Raptor sea level nozzle diameter are 1.6-1.8m from the previous thread.  5 meters is not big enough for seven such nozzles;  Nine nozzles would require something on the order of 7-8m.

A 2-nozzle or 3-nozzle launch vehicle would, as I understand it, not be able to land on its main engines.

Scaling up to say 5.2m while maintaining V1.1 fineness and going to methalox propellant would suggest a take off mass around 1,200 - 1,400t which would be best served by 7 Raptors in the 225t thrust range.  As long as you were not planning on strapping 3 of these together to make a 'heavy' version the 7 engines could be arranged similar to the 9 on an F9 with the outboard engines having about half their diameter outside the cross section of the core.
Huh!

Could I get a second opinion on whether this 'outboard engine' arrangement, with nozzles protruding beyond the edge of the vehicle, is workable?  It would make a separate design exercise I've been doing that much easier.

Offline guckyfan

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Re: A new upper stage design for the Falcon family
« Reply #28 on: 09/13/2015 04:22 pm »
Huh!

Could I get a second opinion on whether this 'outboard engine' arrangement, with nozzles protruding beyond the edge of the vehicle, is workable?  It would make a separate design exercise I've been doing that much easier.

Falcon 9 1.0 with the tic tac toe engine arrangement did just that, if not so extreme.

Offline nadreck

Re: A new upper stage design for the Falcon family
« Reply #29 on: 09/13/2015 04:30 pm »

Could I get a second opinion on whether this 'outboard engine' arrangement, with nozzles protruding beyond the edge of the vehicle, is workable?  It would make a separate design exercise I've been doing that much easier.

Look at the F1 arrangement on the Saturn V
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 Burninate

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Re: A new upper stage design for the Falcon family
« Reply #30 on: 09/13/2015 04:40 pm »
Huh!

Could I get a second opinion on whether this 'outboard engine' arrangement, with nozzles protruding beyond the edge of the vehicle, is workable?  It would make a separate design exercise I've been doing that much easier.

Falcon 9 1.0 with the tic tac toe engine arrangement did just that, if not so extreme.
Doesn't seem like they protruded beyond the lower fairing

Could I get a second opinion on whether this 'outboard engine' arrangement, with nozzles protruding beyond the edge of the vehicle, is workable?  It would make a separate design exercise I've been doing that much easier.

Look at the F1 arrangement on the Saturn V
Similarly, there is external fairing structure shielding the engines.  They're not exposed to the airstream much.

I guess my own issue would be addressed by adding these fairing bumps, so long as they can be attached one by one without much superstructure.
« Last Edit: 09/13/2015 04:42 pm by Burninate »

Online Brovane

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Re: A new upper stage design for the Falcon family
« Reply #31 on: 09/13/2015 04:49 pm »

1) Having two different fuel types on one rocket complicates launch operations.


The majority of LV use two different types of fuel on each stage. 


2) Having a completely new engine type for just one upper stage would mean considerable cost increases, due:
2.1) Cost to design an engine they would not otherwise need
2.2) Cost to prepare the manufacturing of an engine they would not otherwise need
2.3) Manufacturing only small number of those new upper stage engines and not being able to share most parts with first stage engine would mean considerably higher unit costs for the engines(compared to Merlin 1dVac)

SpaceX is already developing a methane engine.  It isn't a huge leap to expect that SpaceX might want to switch to a Methane upper stage engine.  If you combine 3rd printing, Modern CNC machines, and 2nd stage re-usability,  a different upper stage from the boost stage engine doesn't have to equal considerable higher costs. 
"Look at that! If anybody ever said, "you'll be sitting in a spacecraft naked with a 134-pound backpack on your knees charging it", I'd have said "Aw, get serious". - John Young - Apollo-16

Offline Jim

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Re: A new upper stage design for the Falcon family
« Reply #32 on: 09/13/2015 06:09 pm »

Could I get a second opinion on whether this 'outboard engine' arrangement, with nozzles protruding beyond the edge of the vehicle, is workable?  It would make a separate design exercise I've been doing that much easier.

Look at the F1 arrangement on the Saturn V

And classic Atlas

Offline Impaler

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Re: A new upper stage design for the Falcon family
« Reply #33 on: 09/13/2015 08:14 pm »
Why is everyone assuming reusability?  I thought that had been given up on Falcon S2. 

Maybe the goal is to maximize expendable performance which could be done with Metho-Lox and or weight shaving on a stage which had previously been designed with intended reuse and is thus over-built for an expendable.

Or maybe the design changes are entirely oriented to making the S2 cheaper and faster to manufacture, more then half of Space-X innovation is oriented towards manufacturing rather then vehicle performance.  With impending S1 reuse the manufacturing bottleneck will move into making the S2 as well as most of the potential for cost savings.

Offline guckyfan

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Re: A new upper stage design for the Falcon family
« Reply #34 on: 09/13/2015 08:40 pm »
Why is everyone assuming reusability?  I thought that had been given up on Falcon S2. 

Because that is what Chris Bergin said, SpaceX is contemplating. Not with the present design, that will not be upgraded for reusability. But a completely new design could be developed.

SpaceX does not need upgrades. The present capability of Falcon Heavy even with a RP-1 upper stage is the largest available for anything up to Mars. For anything beyond the capability could be easily upgraded with a kick stage.

More efficient production? With all the commonality to the first stage it is hard to imagine they could improve on that. With fewer first stages produced they can increase second stage production with existing tooling.

Offline AncientU

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Re: A new upper stage design for the Falcon family
« Reply #35 on: 09/13/2015 09:52 pm »

1) Having two different fuel types on one rocket complicates launch operations.


The majority of LV use two different types of fuel on each stage. 


2) Having a completely new engine type for just one upper stage would mean considerable cost increases, due:
2.1) Cost to design an engine they would not otherwise need
2.2) Cost to prepare the manufacturing of an engine they would not otherwise need
2.3) Manufacturing only small number of those new upper stage engines and not being able to share most parts with first stage engine would mean considerably higher unit costs for the engines(compared to Merlin 1dVac)

SpaceX is already developing a methane engine.  It isn't a huge leap to expect that SpaceX might want to switch to a Methane upper stage engine.  If you combine 3rd printing, Modern CNC machines, and 2nd stage re-usability,  a different upper stage from the boost stage engine doesn't have to equal considerable higher costs.

Could also be that the MCT would be best served by a mini-Raptor design, matched to the demands of landing that upper stage.  This smaller engine could be purposed for the FH high energy upper stage that has been discussed from the beginning.  MCT is itself a likely to be a reusable second stage -- technology that SpaceX would need to validate before the full-scale MCT is built.

FH has been stated to be flown lots in support of the Mars development effort.  Propellant deliveries (Methlox, of course) would only make sense with a Methlox engine and reusable second stage tanker.  Once second stage reuse has been demonstrated with "free" fuel payloads, many other reuse applications will be found for variants of that technology.
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Offline hkultala

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Re: A new upper stage design for the Falcon family
« Reply #36 on: 09/16/2015 04:46 am »

1) Having two different fuel types on one rocket complicates launch operations.


The majority of LV use two different types of fuel on each stage. 

And those are much more expensive than Falcon 9.

Many of the most cost-effective ones use only one (Soyuz, Proton-M) use only one type of fuel.

Quote

2) Having a completely new engine type for just one upper stage would mean considerable cost increases, due:
2.1) Cost to design an engine they would not otherwise need
2.2) Cost to prepare the manufacturing of an engine they would not otherwise need
2.3) Manufacturing only small number of those new upper stage engines and not being able to share most parts with first stage engine would mean considerably higher unit costs for the engines(compared to Merlin 1dVac)

SpaceX is already developing a methane engine.  It isn't a huge leap to expect that SpaceX might want to switch to a Methane upper stage engine.  If you combine 3rd printing, Modern CNC machines, and 2nd stage re-usability,  a different upper stage from the boost stage engine doesn't have to equal considerable higher costs.

You would still need to develop ANOTHER engine. Engine development still costs a LOT.

And about the manufacturing..
One of the biggest reasons why Falcon 9 has been so cheap is the mass-procuded engines.
They just mass-produce 10 engine chambers, 10 turbopumps etc. and then use different nozzle in one of those.

You cannot 3d print the whole engine. You still need some special tooling. And no matter how good you tooling is , making 120 engines/year means much lower unit costs than when making 3-12 engines per year.


This only makes sense, if they would use clusters of these smaller methane engines as upper stage engine of MCT.

Offline guckyfan

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Re: A new upper stage design for the Falcon family
« Reply #37 on: 09/16/2015 07:03 am »
No doubt two fuels bring added cost. Elon Musk has argued the same. But that was a long time ago and at that time he htought of LH as upper stage fuel, I am sure. However the added cost for methane are much lower than for LH.

Development cost for a smaller methane engine might not be too high. Subscale components for Raptor are already being tested and would be quite near to that subscale Raptor engine for a Falcon upper stage.

No doubt that such a stage would be much more expensive than the present stage. But that is acceptable for a reusable stage that can fly at least 10 times a year. For applications where the second stage is lost, they would likely still use the present upper stage unless the increased performance is needed and worth the cost. That would be for some missions beyond GTO for NASA. Like heavy payloads to lunar orbit or Earth-Moon L-points or missions beyond Mars.

But the main reason I imagine would make it worth for Elon Musk: It is a relatively cheap subscale MCT development. It would retire many risks before MCT is built.

Offline oldAtlas_Eguy

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Re: A new upper stage design for the Falcon family
« Reply #38 on: 09/16/2015 05:17 pm »
Ok a little bit of history on the discussion of CommX. (See the various SpaceX satelite threads for more details of the discussion on costs, and engineering)

1) Satelites will weigh <180kg each.
2) As many as 128 of them can be packed into a dispenser that will even fit in the current F9/FH size fairing. Weight with dispenser about 30-32mt
3) Cost of manufacture of each sat estimated at $500K
4) Target cost of launch of each sat at $500K ($70M on an FHR including cost of the expendable dispenser)
5) Cost to deploy 1st generation CommX (4096 sats and 32 launches) = $4-5B

Now for the economics of a reusable US.
1) current cost of the US is ~$16M.
2) reusing the stage will save ~$10M
3) over the deployment of using the FHR with this reusable US is $320M (32 FHR flights dispensing 128 sats each)

Question is $320M enough to equal the development cost of this reusable US?

Otherwise the business case will not close for this upgrade within the lifetime of the use of F9 and FH before the BFR/MCT take over the delivery of large quantity of sats, people and bulk cargo (including prop) at almost the same cost per flight as the FHR with 3 times the payload.

2nd generation CommX sats would be deployed in the 2025 or later timeframe by which time BFR/MCT will be flying. A 50% heavier sat with 3-4X the data rate throughput upgrade (smaller spot sizes) launch at 256 of them at a time for half the cost each $250K will reduce the cost of deployement of this 2nd generation of CommX sats to $3-5B a savings of $1B. F9R or FHR cannot compete economically with this no mater what you do to the US.

If BFR/MCT will be significantly delayed then there may be an economic incentive to make the current F9/FH US reusable. But that is the only thing that would make such a project even considerable.

Offline Ludus

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Re: A new upper stage design for the Falcon family
« Reply #39 on: 09/16/2015 06:10 pm »
Ok a little bit of history on the discussion of CommX. (See the various SpaceX satelite threads for more details of the discussion on costs, and engineering)

1) Satelites will weigh <180kg each.
2) As many as 128 of them can be packed into a dispenser that will even fit in the current F9/FH size fairing. Weight with dispenser about 30-32mt
3) Cost of manufacture of each sat estimated at $500K
4) Target cost of launch of each sat at $500K ($70M on an FHR including cost of the expendable dispenser)
5) Cost to deploy 1st generation CommX (4096 sats and 32 launches) = $4-5B

Now for the economics of a reusable US.
1) current cost of the US is ~$16M.
2) reusing the stage will save ~$10M
3) over the deployment of using the FHR with this reusable US is $320M (32 FHR flights dispensing 128 sats each)

Question is $320M enough to equal the development cost of this reusable US?

Otherwise the business case will not close for this upgrade within the lifetime of the use of F9 and FH before the BFR/MCT take over the delivery of large quantity of sats, people and bulk cargo (including prop) at almost the same cost per flight as the FHR with 3 times the payload.

2nd generation CommX sats would be deployed in the 2025 or later timeframe by which time BFR/MCT will be flying. A 50% heavier sat with 3-4X the data rate throughput upgrade (smaller spot sizes) launch at 256 of them at a time for half the cost each $250K will reduce the cost of deployement of this 2nd generation of CommX sats to $3-5B a savings of $1B. F9R or FHR cannot compete economically with this no mater what you do to the US.

If BFR/MCT will be significantly delayed then there may be an economic incentive to make the current F9/FH US reusable. But that is the only thing that would make such a project even considerable.

How good is the case for using FH vs a single stick F9R? I'd think there would be some advantage to a steady weekly launch cadence. It's a leaner process that doesn't have to queue up as many satellites. There's less to lose from a failure. It's easier to get reusability working well with a lot of single F9R launches.

If the single F9R weekly launch cadence is considered, the potential savings from reusable second stages obviously goes way up.

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