Author Topic: What happens if BFR turns out to be too technically challenging?  (Read 15826 times)

Offline speedevil

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Yes, in the landing phase.  One of those non-intuitive discoveries that you only find out by doing (or try doing) the way the text books say.
For vehicles like F9S1, which have to take account of unpredicted winds and land on seagoing platforms.
Otherwise, this is not clear.

Offline john smith 19

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My point was that refueling doesn't "enable" landing on the Moon, and perhaps Mars. It "enhances" those landings with larger payloads and/or the ability to return. For a one-way landing of small cargo (for values of "small" that include things much larger than anyone can currently land on the Moon), a single launch is sufficient.

I don't think it's likely to happen, but if someone wanted to pay, just for example, $500 million to land 5 tonnes on the Moon, BFR/BFS could do it in a single launch with no refueling.
Things is if your big pitch is "much lower cost through full reusability" the flip side is much higher cost as you're going to throw away a whole vehicle designed for the economics of reuse.

It'd be like flying the Shuttle as an uncrewed drone with no crew on board and minimal consumables.

Possible but a massive amount of money to deliver a fairly small increase in payload.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C Apply So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline speedevil

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Things is if your big pitch is "much lower cost through full reusability" the flip side is much higher cost as you're going to throw away a whole vehicle designed for the economics of reuse.

It'd be like flying the Shuttle as an uncrewed drone with no crew on board and minimal consumables.

Possible but a massive amount of money to deliver a fairly small increase in payload.
Congress likes it though!

Offline john smith 19

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For vehicles like F9S1, which have to take account of unpredicted winds and land on seagoing platforms.
Otherwise, this is not clear.
I had thought that F9 S1 being the only booster stage that had attempted recovery (and all the other successful vehicles that had carried out first stage launches) would have framed the context.

Clearly I was not specific enough.  :(
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C Apply So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Robotbeat

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Expect a far more stripped down version of BFR/S initially. Bare minimal features for a ship to deliver a commercial satellite to orbit and return to earth with all stages reused. ...
I mean yeah, that was clear the whole time based on their presentation. Was it unclear to you? I’ve been saying it constantly: BFR really isn’t that far away.

And the fact they’ll launch it just for commsats at first (just as Musk presented in the 2017 IAC) is what will enable them to maintain pretty close to the aggressive timescale that nobody thought possible and that everyone laughed at.
...
I think it's fair to say that the BFS flying rolling out in 2019 or 20 will be a very minimal vehicle and a long way from the final Mars capable BFR. 
Oh, but now that it’s clear the goals Musk shared at IAC aren’t absurd, we gotta claim it’s not impressive, right? 😂
« Last Edit: 03/19/2018 11:55 PM by Robotbeat »
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Offline rst

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Things is if your big pitch is "much lower cost through full reusability" the flip side is much higher cost as you're going to throw away a whole vehicle designed for the economics of reuse.

This is true if reusability adds high up-front costs to building the vehicle, and it's not viable flying expendable.  But F9 was operated as an expendable booster for the first several years, so it seems SpaceX could expend them while charging market rates for the flights, and still not go broke.  And the hardware that's there to specifically support reuse -- landing legs, grid fins, extra plumbing for engine restarts, first stage avionics, RCS, and so forth -- doesn't obviously add a huge amount to the cost of the vehicle (and some of it gets left off expendable flights anyway).

There certainly can be vehicles that it makes no sense at all to expend -- Shuttle was certainly one, and BFS is very, very likely to wind up being another.  But for the generation of rockets that's currently flying, SpaceX seems to have found a way to develop reuse without betting the company's finances on quick success.

Offline Robotbeat

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SpaceX is the only maker of reusable rockets right now, and their cost per unit dry mass is LOWER than typical expendable rockets. BFR, according to SpaceX’s plans, is planned to be similar. I believe this because they’ve ALREADY achieved it with Falcon 9.

Expendable BFR would be about $300 to $450 million per launch (the latter is for 2016’s ITS, a much larger vehicle). Still a lot cheaper than SLS, not more expensive. Considering they’ve already made Raptors and carbon fiber structure, I believe their claims.
« Last Edit: 03/20/2018 03:03 AM by Robotbeat »
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Offline butters

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I don't think there's anything that's going to stop SpaceX from developing the 9m BFR or the satellite BFS. There are any number of reasons why they might struggle to land on Mars or support human colonization of Mars, but we have to frame those struggles in the context of a company which has a fully-reusable launch system with unprecedented capacity. SpaceX will be confident in SpaceX. Everybody will be confident in SpaceX. They will have a story to tell which will be very compelling for investors, and they will have a story to tell which will be very compelling for the US government.

If the first cargo BFS makes a crater on Mars, they'll have enough rope to try again. It's only if they have a fundamental problem, like an issue with header tanks / prop conditioning or unforeseen aerodynamics, that they may have to step back and rethink. Once they've successfully landed such a large vehicle on Mars, we can expect an outpouring of support for human missions. Schedules will slip to the right as more stakeholders get involved and weigh in on things such as crew safety. Progressing from cargo landers to the first human expedition will of course be the most difficult step.

It's hard to imagine a future in which a reusable BFR launches thousands of Internet satellites and we don't attempt a human landing on Mars. How we react to a loss of crew event, in transit or on the surface, is another story.

Offline Robotbeat

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And let's not forget that even basically in the simplest form, BFS will get a ton of experience as an Earth lander. And parts of the reentry will be very similar to Mars entry, in both velocity and density.
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Offline Johnnyhinbos

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And I’m gonna guess they’ll be working out the bugs using the moon as a target (I know a very different EDL profile, but between moon and earth EDLs they’ll have covered a lot of development territory) and you don’t have to wait for several years between attempts...
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Offline speedevil

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And I’m gonna guess they’ll be working out the bugs using the moon as a target (I know a very different EDL profile, but between moon and earth EDLs they’ll have covered a lot of development territory) and you don’t have to wait for several years between attempts...

The final moments of the moon landing are rather like Mars.
Near-vacuum, unprepared terrain, ...

The tanker operations, entry velocity, and injection velocity and landing of a lunar surface mission are all remarkably similar to Mars.
Coast phase to Mars is of course longer, and there is no ISRU needed, but you've got similar tanker operations, injection velocity, similar ish last phase of landing and takeoff in 'poorly mapped' unimproved reduced gravity terrain with inadequate local positioning, similar earth injection and similar entry and landing.

Even the lunar landing mass sort of matches.

Hanging out in GEO or L1/2 would be great for long durations. Hanging out just outside L1 in the umbral shadow can even match insolation and thermal near Mars, as well as providing a useful staging point for craft from earth to tank and detank propellant to, to avoid it needing to go down to the lunar surface and back.

Lots of possible incidental lunar mission possibilities as testing for Mars.

Online AncientU

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Don't get hopes up for much 'hanging out'... they'll learn all they need from trips back and forth to Moon and Mars.
« Last Edit: 03/20/2018 10:50 AM by AncientU »
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Online AncientU

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...
I think it's fair to say that the BFS flying rolling out in 2019 or 20 will be a very minimal vehicle and a long way from the final Mars capable BFR. 


...a very minimal Nova-class vehicle.
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Offline wannamoonbase

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...
I think it's fair to say that the BFS flying rolling out in 2019 or 20 will be a very minimal vehicle and a long way from the final Mars capable BFR. 


...a very minimal Nova-class vehicle.

Yes, likely something less than the ultimate goal but larger than a Saturn V!

Seems the Raptor will be less than the final target performance at first, they’ll have to scale accordingly.

Edit: I'm curious if they build the carbon fiber structure to be what they think is the final size and limit how much fuel they put in the vehicle. 
« Last Edit: 03/20/2018 12:32 PM by wannamoonbase »
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Offline Oersted

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What comforts me about the whole credo and philosophy of SpaceX is that the company is absolutely wedded to science- and engineering-based planning as well as First Principles-thinking. Whatever they are suggesting, no matter how outlandish it initially seems, it will be based on sound science and engineering. If First Principles indicate the way to go, SpaceX will take it.

I find their initial planning much more convincing than the hodgepodge that is NASA. The Shuttle was a weird compromise conditioned by budgetary constraints, divvying out contracts based on regionalism and politics, military requirements, Cold War posturing, and many similar unscientific considerations. The NASA strategy post-Shuttle... Well, I don't think we need to waste time on that mess.

SpaceX is, on the contrary, driven by a clear vision, centrally formulated, and with no regard for peripheral interests. They display great flexibility combined with a single-minded focus on a clear, visionary mission.

I agree with others that their iterative approach is a true strength. They can start out with a bare-bones model of the BFS and develop it incrementally, adding features. I think the first "BFS" we will see will be a boilerplate outer-mold line mega-Grashopper, perhaps powered by a couple of scavenged Merlins and Falcon tankage + plumbing, doing increasingly large hops on the Texas coast.

Online AncientU

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What comforts me about the whole credo and philosophy of SpaceX is that the company is absolutely wedded to science- and engineering-based planning as well as First Principles-thinking. Whatever they are suggesting, no matter how outlandish it initially seems, it will be based on sound science and engineering. If First Principles indicate the way to go, SpaceX will take it.

I find their initial planning much more convincing than the hodgepodge that is NASA. The Shuttle was a weird compromise conditioned by budgetary constraints, divvying out contracts based on regionalism and politics, military requirements, Cold War posturing, and many similar unscientific considerations. The NASA strategy post-Shuttle... Well, I don't think we need to waste time on that mess.

SpaceX is, on the contrary, driven by a clear vision, centrally formulated, and with no regard for peripheral interests. They display great flexibility combined with a single-minded focus on a clear, visionary mission.

I agree with others that their iterative approach is a true strength. They can start out with a bare-bones model of the BFS and develop it incrementally, adding features. I think the first "BFS" we will see will be a boilerplate outer-mold line mega-Grashopper, perhaps powered by a couple of scavenged Merlins and Falcon tankage + plumbing, doing increasingly large hops on the Texas coast.

I believe they have enough test seconds on Raptor to fly that engine (or a set of them) in 2019 -- in fact, there isn't a shred of evidence otherwise.  The sub-scale Raptor on the stand is still an incredibly performing FFSC methlox engine, with likely the highest power to weight ratio ever built in the US... it will be made 'light and tight' for the full production runs, but getting it flying is the near term plan (IMO). 

Same with Carbon tanks...
« Last Edit: 03/20/2018 02:03 PM by AncientU »
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Offline envy887

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My point was that refueling doesn't "enable" landing on the Moon, and perhaps Mars. It "enhances" those landings with larger payloads and/or the ability to return. For a one-way landing of small cargo (for values of "small" that include things much larger than anyone can currently land on the Moon), a single launch is sufficient.

I don't think it's likely to happen, but if someone wanted to pay, just for example, $500 million to land 5 tonnes on the Moon, BFR/BFS could do it in a single launch with no refueling.
Things is if your big pitch is "much lower cost through full reusability" the flip side is much higher cost as you're going to throw away a whole vehicle designed for the economics of reuse.

It'd be like flying the Shuttle as an uncrewed drone with no crew on board and minimal consumables.

Possible but a massive amount of money to deliver a fairly small increase in payload.

I don't think it will be much higher cost. F9 is partly reusable, but even expended is much cheaper than Atlas V. The comparable vehicle to expended BFR/BFS is SLS Block 1B. As I said elsewhere, I'd bet a nickel that an expended BFR/BFS is cheaper than a single SLS Block 1B launch.

Also, even if it is expensive, so what? Right now there are zero systems that can land 5 tonnes on the Moon, even for infinite dollars. Expended BFR/BFS would be a step-function improvement in capability and capacity compared to anything that currently exists. As I said, I doubt it will happen (because I don't think refueling is that hard), but refueling is absolutely not a hard requirement for a BFR/BFS Moon landing.

Offline philw1776

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What comforts me about the whole credo and philosophy of SpaceX is that the company is absolutely wedded to science- and engineering-based planning as well as First Principles-thinking. Whatever they are suggesting, no matter how outlandish it initially seems, it will be based on sound science and engineering. If First Principles indicate the way to go, SpaceX will take it.

I find their initial planning much more convincing than the hodgepodge that is NASA. The Shuttle was a weird compromise conditioned by budgetary constraints, divvying out contracts based on regionalism and politics, military requirements, Cold War posturing, and many similar unscientific considerations. The NASA strategy post-Shuttle... Well, I don't think we need to waste time on that mess.

SpaceX is, on the contrary, driven by a clear vision, centrally formulated, and with no regard for peripheral interests. They display great flexibility combined with a single-minded focus on a clear, visionary mission.

I agree with others that their iterative approach is a true strength. They can start out with a bare-bones model of the BFS and develop it incrementally, adding features. I think the first "BFS" we will see will be a boilerplate outer-mold line mega-Grashopper, perhaps powered by a couple of scavenged Merlins and Falcon tankage + plumbing, doing increasingly large hops on the Texas coast.

Agreed until the last sentence.  No need, much wasted effort and little gained by flying Merlins on the BFS boilerplate/prototype.  Raptor has been in development for many years.  Prototypes test fired since 2016.  Given the AF contract milestones calling for methane engine program completion next month, it would surprise, no SHOCK me if the very first BFS whatchmacallit test vehicle did not use Raptors of some scale from day one.

The major tech challenge for BFR is the robustness of the composite tanks and structure.
Mitigated by going back to the heavier aluminum tech used today and simply sacrificing payload tonnage to LEO.

IF re-useable TPS proves to be an unresolvable issue in the early years, refurbish time and costs get added on per next flights.

So the answer to the topic question posed is this.  Every new technical risk has a work around that lets the program continue with limitations on performance (tonnage to LEO, times of re-use, etc.) and/or increase in cost per flight.  Even with these limitations, the end result would be a major advance.
« Last Edit: 03/20/2018 03:36 PM by philw1776 »
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Offline speedevil

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Don't get hopes up for much 'hanging out'... they'll learn all they need from trips back and forth to Moon and Mars.
It is reasonably plausible that BFS may be ready for Mars at some time which is not immediately before a launch window.

Being able to do extended testing of life support and other things for a few months in an environment which very closely mimics transit conditions in radiation, insolation, ... might have value.
Especially if there are several BFS at this time.
Doing it with a sole unit - no.

Online RonM

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What comforts me about the whole credo and philosophy of SpaceX is that the company is absolutely wedded to science- and engineering-based planning as well as First Principles-thinking. Whatever they are suggesting, no matter how outlandish it initially seems, it will be based on sound science and engineering. If First Principles indicate the way to go, SpaceX will take it.

I find their initial planning much more convincing than the hodgepodge that is NASA. The Shuttle was a weird compromise conditioned by budgetary constraints, divvying out contracts based on regionalism and politics, military requirements, Cold War posturing, and many similar unscientific considerations. The NASA strategy post-Shuttle... Well, I don't think we need to waste time on that mess.

SpaceX is, on the contrary, driven by a clear vision, centrally formulated, and with no regard for peripheral interests. They display great flexibility combined with a single-minded focus on a clear, visionary mission.

I agree with others that their iterative approach is a true strength. They can start out with a bare-bones model of the BFS and develop it incrementally, adding features. I think the first "BFS" we will see will be a boilerplate outer-mold line mega-Grashopper, perhaps powered by a couple of scavenged Merlins and Falcon tankage + plumbing, doing increasingly large hops on the Texas coast.

Agreed until the last sentence.  No need, much wasted effort and little gained by flying Merlins on the BFS boilerplate/prototype.  Raptor has been in development for many years.  Prototypes test fired since 2016.  Given the AF contract milestones calling for methane engine program completion next month, it would surprise, no SHOCK me if the very first BFS whatchmacallit test vehicle did not use Raptors of some scale from day one.

The major tech challenge for BFR is the robustness of the composite tanks and structure.
Mitigated by going back to the heavier aluminum tech used today and simply sacrificing payload tonnage to LEO.

IF re-useable TPS proves to be an unresolvable issue in the early years, refurbish time and costs get added on per next flights.

So the answer to the topic question posed is this.  Every new technical risk has a work around that lets the program continue with limitations on performance (tonnage to LEO, times of re-use, etc.) and/or increase in cost per flight.  Even with these limitations, the end result would be a major advance.

SpaceX would like to land 150 tonnes of cargo on Mars and fly the BFS back to Earth for more. If BFS development issues reduce that to 50 tonnes it is still a big advance. NASA DSM 5.0 was 40 tonnes payload by a single use vehicle.

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