Author Topic: Mars Precursor Vehicle  (Read 8786 times)

Online envy887

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Re: Mars Precursor Vehicle
« Reply #40 on: 06/27/2017 02:01 AM »

The trouble with a small precursor to ITS is that it doesn't benefit from the mass/volume equation in the same way, making EDL quite a different thing. Additionally, keeping cryogenic fluids cold on a trip to Mars would be much harder.

You have this backwards. Smaller vehicles have a much BETTER mass/area ratio for EDL, and big vehicles are harder to get through entry. This (and not launch vehicle capability) is why MSL is the largest thing to land on Mars to date.

The cryo problem is about the same either way.


Read my post again. I was pointing out that a mini-ITS wouldn't behave like the big chap during EDL, not specifying the difference. I also don't agree with you about the cryogenic sustainability issue being the same for a small, low-volume vehicle as a large, low surface area one - relatively speaking, the small ship suffers more heating, and must work harder to remain cool.

And why is easier EDL a 'trouble' that 'doesn't benefit'?

Passive cooling at steady state is the same for either. I think passive cooling will be the primary cooling mechanism. And it might be the only necessary mechanism, depending what pressure the tanks can hold.

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #41 on: 06/27/2017 02:10 PM »
NASA let them build a HIF right on the crawlerway. Why wouldn't they allow improvements to the pad?

The pad mound was untouched and there was no environmental impact to use the crawler way

Offline Jim

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Re: Mars Precursor Vehicle
« Reply #42 on: 06/27/2017 02:17 PM »
I think the concerns about ground support are overblown for several reasons:

1.   The changes for a methane upper stage are much less than those for the full BFS. Remember how their intro video showed stacking the second stage right on the pad with a crane?
2.   Flying with different upper stages has been done before.

3. The Atlas V is flying with multiple fairing diameters right now.

4. They might be able to afford taking 39A out for a few months, and Boca Chica is being built in the same timeframe.


The concerns for ground support are well justified unlike those "reasons"

1.  that is just a video and doesn't mean it is going to happen.  And no one is comparing this to the BFS.

2.  Not from the same pad

3. Meaningless point.  Fairings don't interface with the TEL unlike second stages

4. no, 39A is for Dragon 2 launches and others that can't move to other pads.
« Last Edit: 06/27/2017 02:18 PM by Jim »

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #43 on: 06/27/2017 03:30 PM »
RUS, the thing that I am vehemently against, is either a stock stage with methane or a wider one with methane that operates like the existing stage.  There is no point to these configurations.

An mini BFS/ITS as MG describes has some merit but......

a.  It would only operate out of LC-39A
b.  SLC-40 and/or Boco Chica have be up and running smoothly to keep the cash coming
c.  It would be after FH and Dragon 2 are flying smoothly. 
d.  DOD is not going to use F9 or FH for vertically integrated payloads
e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

Actually, I am wrong about a.  It can't operated from 39A.  A mini BFS/ITS would be incompatible with the existing TEL. It would be too disruptive for the existing FH and it would interfere with manned Dragon 2 flights.  Both these are priorities for Spacex.  It would need to go to another pad.

e.  It won't happen for 2020 because of c & d, unless LC-39B is used.

LC-39B is the SLS pad. Do you know or suspect that something bad will happen to this plan?

It is a multi user pad

Yes, I think 39B seems like probably the only plausible location for such a MiniBFR.  As Jim points out, SpaceX needs their Falcon pads launching Falcon to handle their commercial business.  39A will be launching the occasional FH, as well as crews and goverment payloads.  39B is a multi user pad.  A MLP could be purchased/leased and modified for such vehicle to be vertically integrated in the VAB. 

Depending on it's size, it could offer some favorable optics next to SLS for SpaceX, potentially giving a visual "alternative" right on the same pad.

« Last Edit: 06/27/2017 04:16 PM by Lobo »

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #44 on: 06/27/2017 04:11 PM »

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.


I think they could go the other way with it.  A new wider Raptor power booster to replace FH, with a FUS on top.  Especially for going to Mars, how would you reuse an upper stage that wasn't going there, landing, refueling, and returning to Earth?  I'm no expert in orbital mechanics but in order to have a reusable upper stage going to Mars you need to do like ITS would do, or do a 2 year orbital loop back to Earth (which would get into loiter times), or perhaps it takes Red Dragon to some sort of Mars Transfer Oribt?  But then Red Dragon would need to provide a certain amount of dV in order to get to full escape.

Personally, from some of Musk's comments over time, that the upgrades and growth of F9, along with their continuing learning about reusability, seem to have mostly worked FH out of a job by the time it flies.
Its not needed any longer for most of the EELV-heavy payloads it originally was needed for years ago with Falcon v1.0.
But, it's -is- still needed to cover that D4H payload range.  But that's a pretty small market.  I think D4H has only flown maybe 8 payloads in it's history? 
And a tri-core booster isn't very good for reuse, hence why ITS isn't a tri-core.  And to get like 70 tons to orbit, I'm pretty sure at least the center core would be expended, and perhaps the side boosters too?

So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

And 39B would be the logical location to operate the new booster, so as not to interfere with the Falcon pads that SpaceX needs to be launching Falcons.
« Last Edit: 06/27/2017 04:17 PM by Lobo »

Offline Ludus

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Re: Mars Precursor Vehicle
« Reply #45 on: 06/27/2017 05:08 PM »
If they had the money to do both, it would be compatible with plans expressed to build the full sized ITS Ship with 9 Raptor engines and use it for suborbital flights before building the ITS Booster.

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Re: Mars Precursor Vehicle
« Reply #46 on: 06/27/2017 05:53 PM »

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.


I think they could go the other way with it.  A new wider Raptor power booster to replace FH, with a FUS on top.  Especially for going to Mars, how would you reuse an upper stage that wasn't going there, landing, refueling, and returning to Earth?  I'm no expert in orbital mechanics but in order to have a reusable upper stage going to Mars you need to do like ITS would do, or do a 2 year orbital loop back to Earth (which would get into loiter times), or perhaps it takes Red Dragon to some sort of Mars Transfer Oribt?  But then Red Dragon would need to provide a certain amount of dV in order to get to full escape.

Personally, from some of Musk's comments over time, that the upgrades and growth of F9, along with their continuing learning about reusability, seem to have mostly worked FH out of a job by the time it flies.
Its not needed any longer for most of the EELV-heavy payloads it originally was needed for years ago with Falcon v1.0.
But, it's -is- still needed to cover that D4H payload range.  But that's a pretty small market.  I think D4H has only flown maybe 8 payloads in it's history? 
And a tri-core booster isn't very good for reuse, hence why ITS isn't a tri-core.  And to get like 70 tons to orbit, I'm pretty sure at least the center core would be expended, and perhaps the side boosters too?

So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

And 39B would be the logical location to operate the new booster, so as not to interfere with the Falcon pads that SpaceX needs to be launching Falcons.

The upper stage would be reusable on earth, with the nice advantage that it could also fly a one-way trip to Mars unmanned similar to the idea for Red Dragon and the first ITS.  Reusing the particular stage that flew a demonstration mission to Mars would not be a priority. 

I agree that a Raptor-powered booster smaller than the full BFR would be useful, but paring it with FUS doesn't make much sense.  You still have the drawback of different fuels, but flying a low-ISP upper stage without the ability to coast for more than a few hours wouldn't be very useful, and you still don't get any experience using Raptor in deep space - better to go to an all methalox vehicle right away. 

Online envy887

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Re: Mars Precursor Vehicle
« Reply #47 on: 06/27/2017 06:05 PM »

So - build a "Mars Precursor Vehicle" that acts like BFS - it's a second stage, but can also be a refuelable Mars vehicle.

It launches on FH, but with a RUS instead of the current Merlin, can take maybe 70 tons to orbit.


I think they could go the other way with it.  A new wider Raptor power booster to replace FH, with a FUS on top.  Especially for going to Mars, how would you reuse an upper stage that wasn't going there, landing, refueling, and returning to Earth?  I'm no expert in orbital mechanics but in order to have a reusable upper stage going to Mars you need to do like ITS would do, or do a 2 year orbital loop back to Earth (which would get into loiter times), or perhaps it takes Red Dragon to some sort of Mars Transfer Oribt?  But then Red Dragon would need to provide a certain amount of dV in order to get to full escape.

Personally, from some of Musk's comments over time, that the upgrades and growth of F9, along with their continuing learning about reusability, seem to have mostly worked FH out of a job by the time it flies.
Its not needed any longer for most of the EELV-heavy payloads it originally was needed for years ago with Falcon v1.0.
But, it's -is- still needed to cover that D4H payload range.  But that's a pretty small market.  I think D4H has only flown maybe 8 payloads in it's history? 
And a tri-core booster isn't very good for reuse, hence why ITS isn't a tri-core.  And to get like 70 tons to orbit, I'm pretty sure at least the center core would be expended, and perhaps the side boosters too?

So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

And 39B would be the logical location to operate the new booster, so as not to interfere with the Falcon pads that SpaceX needs to be launching Falcons.

At this point, the marginal effort to get and keep FH flying is tiny. compared to getting a whole new larger booster flying. A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

Eventually they will build a larger booster, but it won't be paired with the Merlin upper stage. That just makes no sense at all. If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Online envy887

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Re: Mars Precursor Vehicle
« Reply #48 on: 06/27/2017 06:09 PM »
Yes, I think 39B seems like probably the only plausible location for such a MiniBFR.  As Jim points out, SpaceX needs their Falcon pads launching Falcon to handle their commercial business.  39A will be launching the occasional FH, as well as crews and goverment payloads.  39B is a multi user pad.  A MLP could be purchased/leased and modified for such vehicle to be vertically integrated in the VAB. 

Depending on it's size, it could offer some favorable optics next to SLS for SpaceX, potentially giving a visual "alternative" right on the same pad.

Boca Chica is also plausible, as it's ideal for GTO, cis-lunar, and interplanetary flights.

Offline MickQ

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Re: Mars Precursor Vehicle
« Reply #49 on: 06/28/2017 10:08 AM »
What's the possibility / likelihood of 39C being constructed as a multi vehicle pad with 2 opposing TEL/HIF sets ?

Online envy887

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Re: Mars Precursor Vehicle
« Reply #50 on: 06/28/2017 12:01 PM »
What's the possibility / likelihood of 39C being constructed as a multi vehicle pad with 2 opposing TEL/HIF sets ?

There is only one ramp, from the south. The flame trench exhausts to the north, so they can't put a HIF there. And Jim says NASA would frown on even minor modifications to the ramp.

It would be much easier to add a HIF and TEL to the west of 40, where the old Titan service towers were. 40 was used to launch the 4 Mlbf Titan IV, so a Falcon Heavy launch wouldn't be that impractical if they approach from the right direction.

Edit: I totally thought that you said 39A, sorry.

Falcon Heavy has to approach 180 degrees away from the flame trench exhaust, so it cannot have multiple approaches to the same pad/trench. But a new pad could certainly have multiple HIFs at the bottom of a single ramp.
« Last Edit: 06/29/2017 01:20 AM by envy887 »

Offline Robotbeat

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Re: Mars Precursor Vehicle
« Reply #51 on: 06/28/2017 12:40 PM »
I seem to recall Musk or someone saying they would have two TELs on LC39a, one for Falcons and one for ITS.
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Re: Mars Precursor Vehicle
« Reply #52 on: 06/28/2017 03:37 PM »
Quote
So perhaps a new subscale Raptor powered big dumb booster that is RTLS, which starts off with an expendable FUS (perhaps with some upgrades to optimize it for this purpose)  that can start dropping Red Dragons on Mars.  After that work on developing a new reusable upper stage, a mini-BFS, that would then also be the biconic spacecraft and lander for the first crews to Mars.  Red Dragons are one way tickets, so you need something that can come back before you start sending people there.
This could be of sufficient size for the initial exploration class missions, which would only have smaller crews anyway.  Then the full ITS would come later after SpaceX has cut their teeth on a smaller vehicle.

So this new BFS like mini
1. Has multiple uses. Thats good because it isn't a throw away intermediate development step.
a. Launch constellation
b. Launch earth stuff
c. EDL mars.

2. Big problem.
Has all the development tech of BFS.
a. Raptor and LOX/CH4
b. Composite
c. autogenous pressurization
d. Combined fairing/US/Biconic reentry vehicle.

So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

So where is the saving? 

We need an intermediate step with less tech to develop that isn't throw away.

1. I still like booster first because it eliminates d. above.
With raptor and composite booster it could stage at a greater m/s and still RTLS.
With the extra boost for S2, S2 could still do reusable with Dragon tech for reentry.

2. How could we take the 2nd stage proposed in the first post and reduce the tech needed to make it?
« Last Edit: 06/28/2017 03:49 PM by rsdavis9 »
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Online envy887

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Re: Mars Precursor Vehicle
« Reply #53 on: 06/28/2017 04:03 PM »
...
So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

1) They don't have to use composites, but if they do it's definitely faster, easier and cheaper to develop a 5 or 6 meter vehicle than a 12 meter one.

2) They can use the existing demo Raptor design without scaling it up, if they want. Using a 3,500 kN engine limits the minimum size of the upper stage. And the demo engine is a lot closer to flying.

3) They can make far more use of existing manufacturing, transport, test, and launch facilities.
« Last Edit: 06/28/2017 04:04 PM by envy887 »

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Re: Mars Precursor Vehicle
« Reply #54 on: 06/28/2017 04:24 PM »
...
So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

1) They don't have to use composites, but if they do it's definitely faster, easier and cheaper to develop a 5 or 6 meter vehicle than a 12 meter one.

2) They can use the existing demo Raptor design without scaling it up, if they want. Using a 3,500 kN engine limits the minimum size of the upper stage. And the demo engine is a lot closer to flying.

3) They can make far more use of existing manufacturing, transport, test, and launch facilities.

So keep it road transportable by limiting to 3.6m.
So if they adopt all three for making it easier/faster to first flight do we still get a useful vehicle?
Sounds like it to me.
Could it only be launched on FH?
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline Lobo

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Re: Mars Precursor Vehicle
« Reply #55 on: 06/28/2017 04:31 PM »

At this point, the marginal effort to get and keep FH flying is tiny. compared to getting a whole new larger booster flying.

But it's still complex to operate (Elon has said that, and it's been said about D4H), and difficult to reuse, and really not needed by more than small number of payloads, due to the growth of F9.  Back when there was F9 v1.0, it was needed for many payloads due to F9's performance at that time.  Reusability wans't an issue then, so a tri-core 1.5 stage booster was a fine idea.  And it seemed like it'd be as easy as just strapping 3 F9 cores together and launching it.  But that has turned out to not be the case.  Cross feed went away for that reason, and it was no longer needed with the upgraded F9.  Then F9 was upgraded again and most of the need for FH at all went away.
You are correct that FH is close to flying, and as they have nothing else in that class close to ready, and they want those USAF/DoD contracts, some of which will reqire D4H performance, they still -need- it.  But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.  Shotwell said they've tested Merlin up to 190klbs, with margin for higher.  They could even upgrade F9 again, and stretch the FUS a bit more, and they may even be able to cover D4H payloads with that.   So I think they've become less and less excited about FH as it's got closer and closer to flying.  It'll almost be obsolete by the time it flies, ironically.



A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

Eventually they will build a larger booster, but it won't be paired with the Merlin upper stage. That just makes no sense at all. If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Well, my point isn't that I think a FUS on a larger Raptor booster is the new LV itself, but that a new "dumb" booster could be the first element developed.  If they put a FUS on top of that, they could have an interim vehicle that could cover the occasional payloads that would need the FH.  As well as provide testing for the booster, ahead of the development of a mini-BFS. 

A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Huh?
No, I think when you develop the booster you are maybe 20% of the way to a new upper stage.  Remember, for a mini-BFR/BFS, the upper stage will be a resuable spaceship...and lander.  It will need to be a lander at first only on Earth, but later on the Moon and Mars presumably.  It will be a biconic lifting body, with a new TPS system on ti's nose and side, and perhaps some sort of shuttle-like internal payload bay.  And likely have the ability to put a crew cabin in it later.  It'll need solar power for long loiter times, etc.
No, I think the mini-BFS will be definitely be the long pole item, IMO.  And be the much longer item to develop.  The Booster will more or less just be a larger version of F9 booster.  That's pretty well understood by SpaceX now.  Definitely the easier of the two pieces.  The biconic spaceship will be the new cutting edge difficult bit.

If they wanted to just build a larger version of FUS with Raptor power, then you might be correct.  But I'm pretty sure they aren't going to put such an expendable upper stage on a new vehicle like that as the final product.

However, they -could- put a FUS on it to get some launches under it's belt, and retire FH, while flying those payloads fully reusably, and dropping Red Dragons on Mars.

It would just be an interim configuration pending the development of a mini-BFS to mate with it.
Again, just an idea of a different way they could go about things, as opposed to using the FH booster for more uses.  They may want to move on from it as soon as it's absolutely not needed any more, for the reasons I mention above.  No idea if they'd actually go this way, but regardless I still have a hunch that FH may not have a long service life.

Online envy887

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Re: Mars Precursor Vehicle
« Reply #56 on: 06/28/2017 04:43 PM »
...
So my question is why is it easier to develop a small version?
b. Is composite easier if smaller?
a. I don't think it makes any difference to the raptor. Just more of them.
c. shouldn't be any difference for autogenous
d. Shouldn't be any different for biconic reentry vehicle

1) They don't have to use composites, but if they do it's definitely faster, easier and cheaper to develop a 5 or 6 meter vehicle than a 12 meter one.

2) They can use the existing demo Raptor design without scaling it up, if they want. Using a 3,500 kN engine limits the minimum size of the upper stage. And the demo engine is a lot closer to flying.

3) They can make far more use of existing manufacturing, transport, test, and launch facilities.

So keep it road transportable by limiting to 3.6m.
So if they adopt all three for making it easier/faster to first flight do we still get a useful vehicle?
Sounds like it to me.
Could it only be launched on FH?

Road transport isn't necessarily a limit for an upper stage, since leasing a super-large airlifter is an option up to about 7m diameter and 25m long.

It's more capable if limited to FH. Like 50 tonnes of payload to Mars surface capable. However, a mini-BFS sized for F9, which would be about the same size as the existing upper stage and fairing, would still be pretty capable and much more useful for dispensing constellation satellites thanks to F9 flight rates.
« Last Edit: 06/28/2017 04:52 PM by envy887 »

Offline Negan

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Re: Mars Precursor Vehicle
« Reply #57 on: 06/28/2017 04:49 PM »
But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.

So if F9 and FH are so different cost wise, why wasn't the circumlunar mission a lot more? Although we've never received an exact figure, it still looks to be less than $200 million, and that includes the Dragon 2 and all the support to go with it. Seems like they would have been far enough along on the development of FH when they announced this mission, they would have a handle on what would be involved.
« Last Edit: 06/28/2017 04:51 PM by Negan »

Online envy887

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Re: Mars Precursor Vehicle
« Reply #58 on: 06/28/2017 04:51 PM »

At this point, the marginal effort to get and keep FH flying is tiny. compared to getting a whole new larger booster flying.

But it's still complex to operate (Elon has said that, and it's been said about D4H), and difficult to reuse, and really not needed by more than small number of payloads, due to the growth of F9.  Back when there was F9 v1.0, it was needed for many payloads due to F9's performance at that time.  Reusability wans't an issue then, so a tri-core 1.5 stage booster was a fine idea.  And it seemed like it'd be as easy as just strapping 3 F9 cores together and launching it.  But that has turned out to not be the case.  Cross feed went away for that reason, and it was no longer needed with the upgraded F9.  Then F9 was upgraded again and most of the need for FH at all went away.
You are correct that FH is close to flying, and as they have nothing else in that class close to ready, and they want those USAF/DoD contracts, some of which will reqire D4H performance, they still -need- it.  But they'll have this complex and hard to reuse LV that will only be needed once in awhile, and is basically an evolutionary dead end.  Shotwell said they've tested Merlin up to 190klbs, with margin for higher.  They could even upgrade F9 again, and stretch the FUS a bit more, and they may even be able to cover D4H payloads with that.   So I think they've become less and less excited about FH as it's got closer and closer to flying.  It'll almost be obsolete by the time it flies, ironically.

F9 is nowhere near DIVH payloads to high energy missions and never will be with the current upper stage or any kind of reuse. While FH can likely put more payload to GTO than DIVH can, while still reusing all the boosters. I'm sure that FH with reuse will be cheaper than F9 expendable within a few years.

Also, SpaceX seems pretty excited about heavy GTO commsats, which also require expending F9, and about the lunar Dragon mission which has apparently gotten a lot of interest and also requires FH. I doubt FH is going away all that quickly

Quote


A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

Eventually they will build a larger booster, but it won't be paired with the Merlin upper stage. That just makes no sense at all. If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Well, my point isn't that I think a FUS on a larger Raptor booster is the new LV itself, but that a new "dumb" booster could be the first element developed.  If they put a FUS on top of that, they could have an interim vehicle that could cover the occasional payloads that would need the FH.  As well as provide testing for the booster, ahead of the development of a mini-BFS. 

A new booster REQUIRES a new factory and a new test facility. A sufficiently small mini-BFS might not.

If you can build a new booster you're 95% of the way to a new upper stage. And the Merlin upper stage is way too underpowered for FH already.

Huh?
No, I think when you develop the booster you are maybe 20% of the way to a new upper stage.  Remember, for a mini-BFR/BFS, the upper stage will be a resuable spaceship...and lander.  It will need to be a lander at first only on Earth, but later on the Moon and Mars presumably.  It will be a biconic lifting body, with a new TPS system on ti's nose and side, and perhaps some sort of shuttle-like internal payload bay.  And likely have the ability to put a crew cabin in it later.  It'll need solar power for long loiter times, etc.
No, I think the mini-BFS will be definitely be the long pole item, IMO.  And be the much longer item to develop.  The Booster will more or less just be a larger version of F9 booster.  That's pretty well understood by SpaceX now.  Definitely the easier of the two pieces.  The biconic spaceship will be the new cutting edge difficult bit.

If they wanted to just build a larger version of FUS with Raptor power, then you might be correct.  But I'm pretty sure they aren't going to put such an expendable upper stage on a new vehicle like that as the final product.

However, they -could- put a FUS on it to get some launches under it's belt, and retire FH, while flying those payloads fully reusably, and dropping Red Dragons on Mars.

It would just be an interim configuration pending the development of a mini-BFS to mate with it.
Again, just an idea of a different way they could go about things, as opposed to using the FH booster for more uses.  They may want to move on from it as soon as it's absolutely not needed any more, for the reasons I mention above.  No idea if they'd actually go this way, but regardless I still have a hunch that FH may not have a long service life.

At least 95% to a dumb upper stage. Certainly much more than 20% towards a mini-BFS upper stage. I'm including all the manufacturing, transport, test, integration and launch infrastructure, in addition to development costs. A FH-replacement single stick booster can't use any of the existing infrastructure.

Offline Negan

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Re: Mars Precursor Vehicle
« Reply #59 on: 06/28/2017 05:11 PM »
I'm sure that FH with reuse will be cheaper than F9 expendable within a few years.

So it has already been established that currently FH with reuse cost more than F9 expendable?
« Last Edit: 06/28/2017 05:14 PM by Negan »

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