Author Topic: BFR or BFS first or both?  (Read 11220 times)

Offline maitri982

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BFR or BFS first or both?
« on: 01/01/2018 01:08 AM »
Sorry if I missed this, but which of these is SpaceX building/testing first?

Offline ZachS09

Re: BFR or BFS first or both?
« Reply #1 on: 01/01/2018 01:29 AM »
I think the Big Falcon Rocket (BFR) will be tested first before the Big Falcon Spaceship (BFS).

Don't why, but it's my personal opinion. You don't have to agree if you think differently.
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Offline speedevil

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Re: BFR or BFS first or both?
« Reply #2 on: 01/01/2018 01:32 AM »
Sorry if I missed this, but which of these is SpaceX building/testing first?

There has been no absolutely unambiguous announcement.
Arguments can be made for both - BFR is 'simpler', being 'just a scaled up F9', BFS is smaller, and allows testing of some components before developing BFR.

In order to get to Mars in 2022, you need to launch Sep 2022, with 2 BFS, at least 1 BFR, and at least one other BFS or tanker - as an absolute minimum.
Statements were made by Gwynne Shottwell at the national space council that they'd test suborbital hops first, which I take to mean that they'll be testing BFS first, in the context they were made.

Everything else depends on funding, and how development goes.

In the other thread, my optimistic prediction was:

Quote
2020/1 BFS hopper is constructed with no TPS to work on landing and initial airframe assurance, followed by the first BFS  Second flight of BFS after a month, then once a week for a couple of months, then once a day for a month.

2021 with the first BFS, after some test flights, SpaceX offers the ability for any relatively small sat to be launched to LEO, nearly any day you want, with the ability to check it out in orbit for a short period before release, and if not, land. (this would be before deployment). Starlink launches begin.

2022, Starlink launches  accelerate as BFR comes online, in time to launch several BFS to Mars in September.

A rapid ramp of BFR cadence finishes the full Starlink constellation rather sooner than expected.
The first crewed launches occur.

On to musings more important than mine.
Gwynne Shotwell testifying (speaking?) before the national space council said
Quote

    BFR is planned to fly hundreds of people, both to low Earth orbit, our ultimate destination is Mars, but that system is being designed also to do Earth hops. And those are some of the first tests that you’ll actually see with the Falcon spaceship.
Her words seem entirely consistent with ship testing first.
In the context of the question, about passenger transport, it might even imply that it can do significant passenger service-capable hops.

From Elon - from reddit
Quote
Will be starting with a full-scale Ship doing short hops of a few hundred kilometers altitude and lateral distance. Those are fairly easy on the vehicle, as no heat shield is needed, we can have a large amount of reserve propellant and don't need the high area ratio, deep space Raptor engines.

Next step will be doing orbital velocity Ship flights, which will need all of the above. Worth noting that BFS is capable of reaching orbit by itself with low payload, but having the BF Booster increases payload by more than an order of magnitude. Earth is the wrong planet for single stage to orbit. No problemo on Mars.
(bold mine).

This implies to me that the payload for BFS-SSTO is >>1.5 tons, and <15 tons, or he would have said 'two orders of magnitude'.

If he in fact meant it can do this and land, which is somewhat plausible with the right assumptions, or that this was a theoretical capacity which would therefore never happen before BFR development is again arguable. The first opens many interesting possibilities.

« Last Edit: 01/01/2018 01:46 AM by speedevil »

Offline meekGee

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Re: BFR or BFS first or both?
« Reply #3 on: 01/01/2018 01:53 AM »
Sorry if I missed this, but which of these is SpaceX building/testing first?

There has been no absolutely unambiguous announcement.
Arguments can be made for both - BFR is 'simpler', being 'just a scaled up F9', BFS is smaller, and allows testing of some components before developing BFR.

In order to get to Mars in 2022, you need to launch Sep 2022, with 2 BFS, at least 1 BFR, and at least one other BFS or tanker - as an absolute minimum.
Statements were made by Gwynne Shottwell at the national space council that they'd test suborbital hops first, which I take to mean that they'll be testing BFS first, in the context they were made.

Everything else depends on funding, and how development goes.

In the other thread, my optimistic prediction was:

Quote
2020/1 BFS hopper is constructed with no TPS to work on landing and initial airframe assurance, followed by the first BFS  Second flight of BFS after a month, then once a week for a couple of months, then once a day for a month.

2021 with the first BFS, after some test flights, SpaceX offers the ability for any relatively small sat to be launched to LEO, nearly any day you want, with the ability to check it out in orbit for a short period before release, and if not, land. (this would be before deployment). Starlink launches begin.

2022, Starlink launches  accelerate as BFR comes online, in time to launch several BFS to Mars in September.

A rapid ramp of BFR cadence finishes the full Starlink constellation rather sooner than expected.
The first crewed launches occur.

On to musings more important than mine.
Gwynne Shotwell testifying (speaking?) before the national space council said
Quote

    BFR is planned to fly hundreds of people, both to low Earth orbit, our ultimate destination is Mars, but that system is being designed also to do Earth hops. And those are some of the first tests that you’ll actually see with the Falcon spaceship.
Her words seem entirely consistent with ship testing first.
In the context of the question, about passenger transport, it might even imply that it can do significant passenger service-capable hops.

From Elon - from reddit
Quote
Will be starting with a full-scale Ship doing short hops of a few hundred kilometers altitude and lateral distance. Those are fairly easy on the vehicle, as no heat shield is needed, we can have a large amount of reserve propellant and don't need the high area ratio, deep space Raptor engines.

Next step will be doing orbital velocity Ship flights, which will need all of the above. Worth noting that BFS is capable of reaching orbit by itself with low payload, but having the BF Booster increases payload by more than an order of magnitude. Earth is the wrong planet for single stage to orbit. No problemo on Mars.
(bold mine).

This implies to me that the payload for BFS-SSTO is >>1.5 tons, and <15 tons, or he would have said 'two orders of magnitude'.

If he in fact meant it can do this and land, which is somewhat plausible with the right assumptions, or that this was a theoretical capacity which would therefore never happen before BFR development is again arguable. The first opens many interesting possibilities.

That last quote by Musk is detailed and complete - I don't think it leaves much for debate.

You can add to it that a stand-along BFS doesn't require the high-thrust pad that BFR does.

Looking forward to seeing it...
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Re: BFR or BFS first or both?
« Reply #4 on: 01/01/2018 02:01 AM »
I think they will build BFS first for a couple of reasons.

1. Gwynne and Elon have both hinted that the ship will be developed first. And according to Elon it can reach orbit by itself with a small payload.

2. BFS will have life support, solar panels, and a huge TPS. None of those are going to be very easy to develop even with the data they have now. Developing the ship first might be more efficient so they can get the "difficult" stuff out of the way early. BFR should be easier since its basically a scaled up Falcon 9 first stage.

Online hkultala

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Re: BFR or BFS first or both?
« Reply #5 on: 01/01/2018 08:47 AM »
1. Gwynne and Elon have both hinted that the ship will be developed first. And according to Elon it can reach orbit by itself with a small payload.

No, Elon has not said that for sure BFS can reach orbit with a small payload.

He has said something along the line that it might reach some orbit with a small payload.

And that orbit might not be a usable orbit for any commercial/institutional payload.

« Last Edit: 01/01/2018 08:50 AM by hkultala »

Offline Robotbeat

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Re: BFR or BFS first or both?
« Reply #6 on: 01/01/2018 11:23 AM »
The 2016 schedule for ITS showed the BFS almost 6 months before BFR.

The 2016 and 2017 schedule have the same dates for Initial Mars missions for BFR/BFS, 2022 for uncrewed and 2024/2025 for crew, so stands to reason other dates would be similar.
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Offline speedevil

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Re: BFR or BFS first or both?
« Reply #7 on: 01/01/2018 01:55 PM »
1. Gwynne and Elon have both hinted that the ship will be developed first. And according to Elon it can reach orbit by itself with a small payload.

No, Elon has not said that for sure BFS can reach orbit with a small payload.

He has said something along the line that it might reach some orbit with a small payload.

And that orbit might not be a usable orbit for any commercial/institutional payload.

See the above quotes - he said literally these words. 'Worth noting that BFS is capable of reaching orbit by itself with low payload''.

That's not a might.
However, it may mean that any payload would need to self-ferry out of a 150km (or whatever) orbit.
Or it may mean that it can do SSTO with payload and land.
Or it may mean it can do SSTO with payload and you get to pick either payload or landing fuel.
Or running the engines hotter than ideal, compromising reliability.
It might even mean which of these it can do is unknown, so he chose the form of words he did.

Small payloads that can self-ferry to their designed orbit would remove the issues of 'usable orbit', as would ones with 'small' kick stages. If you can get ten Starlink satellites out as part of your weekly or daily test program, that helps a lot.

Note that the full-up weight of BFS seems to be quoted with ECLSS and passenger cabins, and long-term solar, and ...
Removing - or not installing all of these features would make the craft more capable - both for small cargo if it can in fact do that, and as a tanker fitted to BFR.

I am unsure if anyone has made a credible estimate on delta-v to go from LEO to ground in BFR.

« Last Edit: 01/01/2018 02:01 PM by speedevil »

Offline aero

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Re: BFR or BFS first or both?
« Reply #8 on: 01/01/2018 02:32 PM »
It seems reasonable to note here that the upper stages of the Saturn 5 were developed first. There were reasons for this, some of which might be common to the BFR/BFS development.

One commonality is that the upper stages of the Apollo moon rocket were capable of reaching orbit without the first stage booster.
A second commonality is that the Apollo capsule and service module were more challenging (longer time) to develop than the booster as is the BFS more challenging than the BFR.
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Offline the_other_Doug

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Re: BFR or BFS first or both?
« Reply #9 on: 01/01/2018 02:44 PM »
It seems reasonable to note here that the upper stages of the Saturn 5 were developed first. There were reasons for this, some of which might be common to the BFR/BFS development.

One commonality is that the upper stages of the Apollo moon rocket were capable of reaching orbit without the first stage booster.
A second commonality is that the Apollo capsule and service module were more challenging (longer time) to develop than the booster as is the BFS more challenging than the BFR.

Umm... not really.  The F-1 engine started development as early as 1955, well before there was a Saturn program.  Heck, well before there was a NASA.  It was a DoD program at the time.

The first Saturn V stage to be developed was the S-IC, but the S-IVB flew first.  However, the version of the S-IVB that flew first was not compatible with the Saturn V, being specifically tailored to function as the second stage of a Saturn IB.

The very last Saturn V stage to be developed, and ready for flight, was one of the upper stages, the S-II.  In fact, this upper stage was the pacing item in Saturn V development for most of its development cycle.

So, umm... not really.
-Doug  (With my shield, not yet upon it)

Offline philw1776

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Re: BFR or BFS first or both?
« Reply #10 on: 01/01/2018 04:51 PM »
So,
Elon has stated that BFS will fly/be tested first before BFR
Elon's schedule chart in his IAC presentations shows BFS first.
There should be no question at this time that BFS flies first, pending future contradicting statements or events.

Why BFS first?
1. BFS has more new, unproven tech, e.g. BOTH types of Raptor engines, TPS, flight path, etc. so de-risk the program before the rest is set in stone.

2. BFS can start test flights with only the 3 sea level Raptors, thereby proving the full thrust Raptor engines and getting Raptor ECO design modifications into the factory before scads of Raptors get built and need to be modified at expense.

3. BFS also allows Rvac testing, not available on BFR.

4. BFS with its legs can be used serendipitously to pre-qualify the landing software at a precision needed for BFR cradle landings.

5. Likely Musk & his Musketeer engineering staff have additional good reasons for BFS first.

I think the first BFR test flights will fly with less than 31 engines but that is only an opinion, likely to be wrong.
« Last Edit: 01/01/2018 04:53 PM by philw1776 »
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Offline meekGee

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Re: BFR or BFS first or both?
« Reply #11 on: 01/01/2018 07:35 PM »
So,
Elon has stated that BFS will fly/be tested first before BFR
Elon's schedule chart in his IAC presentations shows BFS first.
There should be no question at this time that BFS flies first, pending future contradicting statements or events.

Why BFS first?
1. BFS has more new, unproven tech, e.g. BOTH types of Raptor engines, TPS, flight path, etc. so de-risk the program before the rest is set in stone.

2. BFS can start test flights with only the 3 sea level Raptors, thereby proving the full thrust Raptor engines and getting Raptor ECO design modifications into the factory before scads of Raptors get built and need to be modified at expense.

3. BFS also allows Rvac testing, not available on BFR.

4. BFS with its legs can be used serendipitously to pre-qualify the landing software at a precision needed for BFR cradle landings.

5. Likely Musk & his Musketeer engineering staff have additional good reasons for BFS first.

I think the first BFR test flights will fly with less than 31 engines but that is only an opinion, likely to be wrong.

+ a biggie:

BFS's testing (and development) will require prolonged time in orbit.  The mission profile is hugely complex and includes many phases of operation. 

Meanwhile BFR's mission profile is analogous to that of any reusable first stage out there (ha!) - launch, land, repeat.

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Offline Robotbeat

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Re: BFR or BFS first or both?
« Reply #12 on: 01/02/2018 12:46 PM »
The big thing for BFR is the launch cradle.
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Offline jpo234

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Re: BFR or BFS first or both?
« Reply #13 on: 01/02/2018 01:17 PM »
The big thing for BFR is the launch cradle.
I don't think cradle landing is strictly required. If it can't be made to work, SpaceX can fall back to landing legs. This would make relaunch a little bit more expensive, but I don't think it would be a show stopper.
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Offline Patchouli

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Re: BFR or BFS first or both?
« Reply #14 on: 01/02/2018 04:23 PM »
I think the Big Falcon Rocket (BFR) will be tested first before the Big Falcon Spaceship (BFS).

Don't why, but it's my personal opinion. You don't have to agree if you think differently.

I think BFR could be used with an interim upper stage if needed but BFS really needs BFR to be useful.

In theory BFS could be made use F9 cores as boosters early on but it would require a lot of structural differences from the inline vehicle on BFS.
The forces would be different and it could have issues with of plume impingement from the separation motors on the TPS.

The big thing for BFR is the launch cradle.
I don't think cradle landing is strictly required. If it can't be made to work, SpaceX can fall back to landing legs. This would make relaunch a little bit more expensive, but I don't think it would be a show stopper.

The cradle not working out would not be a deal killer in fact I think it's kinda a bad idea as it increases the risk of a mishap destroying the launch facilities.

A botched landing of BFR with a separate landing site you only loose the vehicle but a botch landing with the cradle you damage the launch facilities.
« Last Edit: 01/02/2018 04:30 PM by Patchouli »

Offline dglow

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Re: BFR or BFS first or both?
« Reply #15 on: 01/02/2018 10:55 PM »
The cradle not working out would not be a deal killer in fact I think it's kinda a bad idea as it increases the risk of a mishap destroying the launch facilities.

A botched landing of BFR with a separate landing site you only loose the vehicle but a botch landing with the cradle you damage the launch facilities.

Inclined to agree.

SpaceX /could/ design a level of resilience for a shared launch+landing mount. Perhaps a modular cradle, ready to be swapped out in the event of an unexpectedly crunchy landing. But still, if a tipsy booster bumps the tower then your launch campaign is well and screwed.

Returning to a dedicated landing pad risks so much less, and costs... well, what? 1) a means of transport back to the launch pad, 2) a second booster, for optimal launch cadence.

It seems likely SpaceX will already have both of those.

And a separate landing pad does not necessitate the addition of legs to the booster. It's just another cradle, located safely apart from the tower and GSE. Win-win.
« Last Edit: 01/02/2018 11:16 PM by dglow »

Offline hamerad

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Re: BFR or BFS first or both?
« Reply #16 on: 01/02/2018 11:15 PM »
Hmm maybe too much cost to bother. But could a BFS be put up into orbit under it's own power and then a FH send up landing propellent? Im thinking cost of developing the tank might make it a non starter  but throwing it out there.

Offline Dave G

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Re: BFR or BFS first or both?
« Reply #17 on: 01/03/2018 02:38 AM »
The big thing for BFR is the launch cradle.

Yes.

By contrast, for BFS, they would just need some flat concrete to launch and land it, someplace where they'll allow it, and somewhere near an ocean port, something like Landing Zone 1.

Offline octavo

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Re: BFR or BFS first or both?
« Reply #18 on: 01/03/2018 03:29 AM »
Hmm maybe too much cost to bother. But could a BFS be put up into orbit under it's own power and then a FH send up landing propellent? Im thinking cost of developing the tank might make it a non starter  but throwing it out there.
I can't remember the numbers exactly, but I'm not sure BFS could land with only 60 tons of prop (based on FH leo throw + some for tankage, thrusters, avionics).

Offline meekGee

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Re: BFR or BFS first or both?
« Reply #19 on: 01/03/2018 05:23 AM »
The cradle not working out would not be a deal killer in fact I think it's kinda a bad idea as it increases the risk of a mishap destroying the launch facilities.

A botched landing of BFR with a separate landing site you only loose the vehicle but a botch landing with the cradle you damage the launch facilities.

Inclined to agree.

SpaceX /could/ design a level of resilience for a shared launch+landing mount. Perhaps a modular cradle, ready to be swapped out in the event of an unexpectedly crunchy landing. But still, if a tipsy booster bumps the tower then your launch campaign is well and screwed.

Returning to a dedicated landing pad risks so much less, and costs... well, what? 1) a means of transport back to the launch pad, 2) a second booster, for optimal launch cadence.

It seems likely SpaceX will already have both of those.

And a separate landing pad does not necessitate the addition of legs to the booster. It's just another cradle, located safely apart from the tower and GSE. Win-win.
Just pointing out that because of the "divert" strategy, a botched landing that hits the cradle is by definition one with practically zero fuel and very low velocity.

The pad is already designed to survive a launch.  Could it be designed to withstand a botched landing 10-15 minutes later?
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Offline JamesH65

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Re: BFR or BFS first or both?
« Reply #20 on: 01/03/2018 09:59 AM »
The big thing for BFR is the launch cradle.

Yes.

By contrast, for BFS, they would just need some flat concrete to launch and land it, someplace where they'll allow it, and somewhere near an ocean port, something like Landing Zone 1.

I'm expecting the first BFR to have legs, as grasshopper did, until they get its landing accuracy good enough. Seems like a big ask to get the whole cradle thing working right from the initial prototype stage.

Offline Robotbeat

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Re: BFR or BFS first or both?
« Reply #21 on: 01/03/2018 12:49 PM »
The cradle not working out would not be a deal killer in fact I think it's kinda a bad idea as it increases the risk of a mishap destroying the launch facilities.

A botched landing of BFR with a separate landing site you only loose the vehicle but a botch landing with the cradle you damage the launch facilities.

Inclined to agree.

SpaceX /could/ design a level of resilience for a shared launch+landing mount. Perhaps a modular cradle, ready to be swapped out in the event of an unexpectedly crunchy landing. But still, if a tipsy booster bumps the tower then your launch campaign is well and screwed.

Returning to a dedicated landing pad risks so much less, and costs... well, what? 1) a means of transport back to the launch pad, 2) a second booster, for optimal launch cadence.

It seems likely SpaceX will already have both of those.

And a separate landing pad does not necessitate the addition of legs to the booster. It's just another cradle, located safely apart from the tower and GSE. Win-win.
Oh, not this argument again!

You can address this by just making landing reliable and making two pads, which gives you the further advantage of making throughput even higher.
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Offline Dave G

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Re: BFR or BFS first or both?
« Reply #22 on: 01/03/2018 01:51 PM »
I'm expecting the first BFR to have legs, as grasshopper did, until they get its landing accuracy good enough. Seems like a big ask to get the whole cradle thing working right from the initial prototype stage.

To clarify, there were two Grasshopper versions:  v1.0 and v1.1 (a.k.a. F9R Dev1), shown side-by-side below.

Grasshopper v1.0 had metal legs, which were much heavier than the final carbon-fiber legs on Grasshopper v1.1.
Grasshopper v1.0 also used the much shorter F9 v1.0 booster, and lacked grid fins. In other words, Grasshopper v1.0 was just a quick mock-up for SpaceX to get their feet wet on landing a booster.

For BFR tests, if they used metal legs like Grasshopper v1.0, it would make the BFR booster very bottom-heavy, so I'm not sure how useful that would be, especially now that SpaceX has a lot of experience landing boosters.

If they used carbon-fiber legs for early BFR test landings, that would make it less bottom-heavy, but those legs would be HUGE, so the tooling to make them would probably be very expensive.  Also, just designing legs that big may be a significant engineering challenge.

For early BFR booster test landings, it may be cheaper and easier to temporarily place a BFR landing collar on an existing landing pad, like Landing Zone 2.

In addition, they may intentionally destroy some BFR boosters by landing them in the ocean (i.e. without ASDS), like they did on the first few F9R flights.
« Last Edit: 01/03/2018 01:57 PM by Dave G »

Offline speedevil

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Re: BFR or BFS first or both?
« Reply #23 on: 01/03/2018 03:34 PM »
Hmm maybe too much cost to bother. But could a BFS be put up into orbit under it's own power and then a FH send up landing propellent? Im thinking cost of developing the tank might make it a non starter  but throwing it out there.

Yes, it can.
I was in the process of more fully developing this silly idea with actual numbers, but as it's been raised, and I'm not up to it right now:

Assuming the BFR can get to orbit, but cannot land, as it needs ~20 tons more fuel (1000m/s, ISP 365), you can do the very silly thing of making a basically cylindrical tank 3.6m diameter, possibly reusing the F9 tooling, in place of the payload.
This would have along side it basically a matching bottom to the BFR, and some attitude thrusters.

If you are feeling particularly silly, you can then load the second stage from F9H and the vented tank into the BFR, and recover them, for a completely reusable solution.

I will leave sillier solutions such as suborbital refuelling and how many F9Hs you need to get BFS with 150t cargo to mars (about 20 F9H, and 20 BFS, with 2 BFS craft)  alone for now.

This is a theoretically possible thing that can be done, does not involve much new tankage - will involve considerable modifications to cryo load the methane and oxygen on the transporter erector on F9H, some clamps inside BFR, a small robot arm.

As a side-benefit, such a cryogenic methane/oxygen third stage would make small payloads go very, very fast indeed.

Offline Steve D

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Re: BFR or BFS first or both?
« Reply #24 on: 01/03/2018 04:18 PM »
Alot of people here seem to have trouble with the basic concept of BFR/BFS. It is much cheaper to fly this huge rocket then to fly ANYTHING else. They will not use falcon/falcon heavy to support BFS. Doing so would cost millions of dollars more then using another BFR/BFS for support. Every Falcon launch still throws millions of dollars of hardware into the ocean. Second stage, interstage and fairings are all lost. BFR loses nothing! Everything is recovered! No lost hardware! Dumping money into falcon or heavy is just wasted.Spacex is moving on from Falcon. Just accept that fact.
Steve

Offline speedevil

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Re: BFR or BFS first or both?
« Reply #25 on: 01/03/2018 05:02 PM »
Alot of people here seem to have trouble with the basic concept of BFR/BFS. It is much cheaper to fly this huge rocket then to fly ANYTHING else. They will not use falcon/falcon heavy to support BFS. Doing so would cost millions of dollars more then using another BFR/BFS for support.
If, and only if BFR is flying at the time you want to do tests with BFS, I wholly agree.

It also only costs many many millions if you expend the second stage.
« Last Edit: 01/03/2018 05:16 PM by speedevil »

Offline JamesH65

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Re: BFR or BFS first or both?
« Reply #26 on: 01/03/2018 05:08 PM »
Alot of people here seem to have trouble with the basic concept of BFR/BFS. It is much cheaper to fly this huge rocket then to fly ANYTHING else. They will not use falcon/falcon heavy to support BFS. Doing so would cost millions of dollars more then using another BFR/BFS for support. Every Falcon launch still throws millions of dollars of hardware into the ocean. Second stage, interstage and fairings are all lost. BFR loses nothing! Everything is recovered! No lost hardware! Dumping money into falcon or heavy is just wasted.Spacex is moving on from Falcon. Just accept that fact.
Steve

Really? I not seeing that in the conversation above. AFAICT, most people here are fully versed in the proposed cheapness of the BFR/BFS combination compared with Falcon.

However, what I also see is huge optimism that the BFx combination will be fully working and operational within a 5 year timescale. That is a very short amount of time to develop something like this.

Offline Negan

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Re: BFR or BFS first or both?
« Reply #27 on: 01/03/2018 05:58 PM »
Alot of people here seem to have trouble with the basic concept of BFR/BFS. It is much cheaper to fly this huge rocket then to fly ANYTHING else. They will not use falcon/falcon heavy to support BFS. Doing so would cost millions of dollars more then using another BFR/BFS for support. Every Falcon launch still throws millions of dollars of hardware into the ocean. Second stage, interstage and fairings are all lost. BFR loses nothing! Everything is recovered! No lost hardware! Dumping money into falcon or heavy is just wasted.Spacex is moving on from Falcon. Just accept that fact.
Steve

Really? I not seeing that in the conversation above. AFAICT, most people here are fully versed in the proposed cheapness of the BFR/BFS combination compared with Falcon.

However, what I also see is huge optimism that the BFx combination will be fully working and operational within a 5 year timescale. That is a very short amount of time to develop something like this.

So where do you think they'll be in development in 5 years?

Offline JamesH65

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Re: BFR or BFS first or both?
« Reply #28 on: 01/03/2018 06:12 PM »
Prototypes launched, some failures, not yet ready to take over from F9/H. 

Offline Dave G

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Re: BFR or BFS first or both?
« Reply #29 on: 01/03/2018 06:26 PM »
They will not use falcon/falcon heavy to support BFS. Doing so would cost millions of dollars more then using another BFR/BFS for support. Every Falcon launch still throws millions of dollars of hardware into the ocean.
Agreed.

Second stage, interstage and fairings are all lost.
Inter-stage comes back with booster. 

SpaceX has already recovered fairings from the SES-10 launch.  At Stanford, Gwynne said they expect to start reusing previously flown fairings sometime in the first half of 2018.

So only the second stage is lost.

And this is a really important concept: Once SpaceX is reusing fairings, they can take the carbon fiber people that used to manufacture the fairings and use them to build BFR.


Offline Dave G

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Re: BFR or BFS first or both?
« Reply #30 on: 01/03/2018 06:34 PM »
So where do you think they'll be in development in 5 years?
Prototypes launched, some failures, not yet ready to take over from F9/H.
I agree.  Like most things Elon is involved with, BFR will probably be late.

But that's the point: Other SpaceX projects will probably be delayed as well (e.g. Starlink).

So in the end, I suspect BFR will be delayed no more than anything else.

Offline Negan

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Re: BFR or BFS first or both?
« Reply #31 on: 01/03/2018 07:32 PM »
Prototypes launched, some failures, not yet ready to take over from F9/H.

So what kind of failures do you see happening?

Offline speedevil

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Re: BFR or BFS first or both?
« Reply #32 on: 01/03/2018 11:00 PM »
<snip - of F9H-refuelling>
So only the second stage is lost.

The F9 second stage is a cylinder generally 3.6m*15m. A methane/oxygen tank filling much of the rest of the fairing at the same diameter as the second stage is 3.6*10m or so.

The BFS, if the 'crew' compartments are not fitted (or as I have speculated elsewhere are intentionally easily removable) has enough cargo space and downmass capacity and door dimensions to be able to fit these size of cylinders through the ~3.8m opening of the hatch. (measured off the IAC presentations). They are slid directly in, and then tilted for the last portions.
They can then be secured to the side by clamps.

This of course assumes that F9 second stage recovery doesn't happen in the imagined way.

There are many ways for BFR+BFS to come into being.

The above monstrosity only has a point if BFR is delayed behind BFR sufficiently that BFS testing possibilities are exhausted, and a narrow 5- 20 ton delta-v range exists between SSTO and SSTO+landing.

Other scenarios I prefer might occur, such as BFR following on rapidly enough the above is irrelevant, or even BFR first or if BFS-SSTO works reusably with small payload.


Offline Ronsmytheiii

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Re: BFR or BFS first or both?
« Reply #33 on: 01/04/2018 04:25 PM »
Minor question, instead of BFS for the spacecraft and BFR for the booster, why not use orbiter for the former and booster for the latter? That way it distinguishes the booster from the overall system, BFR.
« Last Edit: 01/04/2018 04:26 PM by Ronsmytheiii »
And this is a good reminder that just because one of your fellow space enthusiasts occasionally voices doubts about the SpaceX schedule announcements or is cautious about believing SpaceX has licked a problem before actually seeing proof that's true, it doesn't mean they hate SpaceX.

Offline speedevil

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Re: BFR or BFS first or both?
« Reply #34 on: 01/04/2018 04:38 PM »
Minor question, instead of BFS for the spacecraft and BFR for the booster, why not use orbiter for the former and booster for the latter? That way it distinguishes the booster from the overall system, BFR.
Because inventing our own names for things that spacex has named never generally ends well.

Offline Dave G

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Re: BFR or BFS first or both?
« Reply #35 on: 01/04/2018 04:48 PM »
Minor question, instead of BFS for the spacecraft and BFR for the booster, why not use orbiter for the former and booster for the latter? That way it distinguishes the booster from the overall system, BFR.

Elon has been using the terms "BFR" and "BFS" since at least 2015, probably earlier. 

We know this from his GQ magazine interview:
Quote from: Elon Musk's GQ interview
The rocket that they are working on is referred to internally by the code name BFR. And it doesn't stand for some arcane, smarty-pants science term. It stands for Big frakking Rocket.

I ask Musk whether he really calls it that; his answer is both delightfully nerdy, and not.

"Well, there's two parts of it—there's a booster rocket and there's a spaceship... So, technically, it would be the BFR and the BFS." As in "Big frakking Spaceship."

Online FutureSpaceTourist

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Re: BFR or BFS first or both?
« Reply #36 on: 02/06/2018 06:22 AM »
From the transcript of Elon’s pre-FH demo launch press conference:

Quote
And then the ship, which is the hardest part, just by far the hardest part of the vehicle, of the BFR system, or interplanetary transport system. Because the ship has to have a heatshield that's capable of re-entering from very high velocities. From velocities way higher than... Basically interplanetary velocities, as opposed to orbital velocities. It's got to control itself through a wide regime, from everything from vacuum, to rarefied gas. Everything from thin atmosphere to thick atmosphere. Hypersonic, supersonic, transonic, subsonic. Different types of atmosphere, from different planets. And then land on unimproved terrain, and be able to take off from unimproved terrain. That's a pretty ridiculous set of requirements for the ship. That's why we're focusing on the ship first, because it's kind of the hard part.

Quote
So our focus is on the ship, and we expect to hopefully do short flights on the ship, with the ship next year. You know, aspirational.

Offline Giovanni DS

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Re: BFR or BFS first or both?
« Reply #37 on: 02/06/2018 06:46 AM »
Personally I see BFR landing on the launch pad as the weakest link. This landing concept is the one thing I would remove from the architecture and return to the proven F9 concept.

Even if you achieve a 95% perfect landing rate (to be demonstrated) then you are going to destroy or severely damage the pad one out 20 launches, the required launch rate would make this a real risk considering they have one pad usable for this.

This is why BFR should be first, to retire this risk.

Offline Cheapchips

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Re: BFR or BFS first or both?
« Reply #38 on: 02/06/2018 06:55 AM »

They don't have to land back at the launch pad.  A dedicated landing pad+cradle near the launch site would work for test/maturity phase.

Offline meberbs

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Re: BFR or BFS first or both?
« Reply #39 on: 02/06/2018 07:16 AM »
Personally I see BFR landing on the launch pad as the weakest link. This landing concept is the one thing I would remove from the architecture and return to the proven F9 concept.

Even if you achieve a 95% perfect landing rate (to be demonstrated) then you are going to destroy or severely damage the pad one out 20 launches, the required launch rate would make this a real risk considering they have one pad usable for this.

This is why BFR should be first, to retire this risk.
As Musk was quoted above there are a lot more really hard parts on the ship than the single one you pointed out on the booster. Plus the ship testing already starts giving them experience landing using Raptors. The requirements listed for the ship are absolute requirements, or the architecture simply will not work. On the other hand, the cradle landing can be simply worked around if it is too hard by landing on a pad 100 meters away and getting transported back.

The first thing you ever want to test is the dealbreakers if at all possible. Also, discussion is kind of moot, because it has now been stated from multiple sources both that the ship will be first, and exactly why.

Offline JamesH65

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Re: BFR or BFS first or both?
« Reply #40 on: 02/06/2018 08:53 AM »
Prototypes launched, some failures, not yet ready to take over from F9/H.

So what kind of failures do you see happening?

Carbon fibre tanks are going to take some work to get right (and I am sure they will figure it out), so I expect some ruptures. Probably during ground testing but they could still lose a vehicle in flight - after all, there is a lots of new stuff (to them) in the BFx system.

Offline Norm38

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Re: BFR or BFS first or both?
« Reply #41 on: 02/07/2018 01:26 AM »
The BFS is a truck. It's got to be reliable and be able to take a beating. It's got to land on rough terrain on Mars so you'd better believe it'll do the same here. Later they should launch in New Mexico and land in a random patch of desert.
They only have to place the three landing engines. They can use heavy legs as ballast for the vacuum engines and launch with partially full tanks. Work their way up, just as Grasshopper did.

Offline meekGee

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Re: BFR or BFS first or both?
« Reply #42 on: 02/07/2018 06:14 AM »
It's very basic...

BFS is unlike anything that's ever been done before. An actual interplanetary ship, and a surface-to-surface one at that. Straight out of sci fi.

BFR is merely a larger rocket.

So of course they have to stat with BFS.
ABCD - Always Be Counting Down

Offline Lar

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Re: BFR or BFS first or both?
« Reply #43 on: 02/07/2018 06:31 AM »
I think this thread is closeable. SpaceX have said multiple times, including Elon himself more than once, BFS first.

While we could play "let's outsmart SpaceX engineers and the CTO", let's not.
"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 speedevil

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Re: BFR or BFS first or both?
« Reply #44 on: 02/07/2018 02:23 PM »
Perhaps appropriate to let Elon have the last word.

From the transcript at https://forum.nasaspaceflight.com/index.php?topic=43154.msg1784964#msg1784964  edited for clarity and topic

Quote
if we get lucky, be able to do short hop flights with the spaceship part of BFR maybe next year.

By hopper tests I mean kind-of-like the grasshopper program for falcon 9, where we just had the rocket take take off and land in Texas at our Texas test site so we'd either do that at our South Texas launch site, near Brownsville or or do ship-to-ship. We're not sure yet whether ship-to-ship or Brownsville, but most likely it's gonna happen in our Brownsville location because got a lot of land with nobody around and so if it blows up, it's cool.

By hopper test I mean it'll go up several miles then come down. The ship is capable of single stage to orbit if you fully load the tanks. So we'll do flights of increasing complexity. We really want to  test the heatshield material so,  like you know fly out turn around accelerate back real hard and come in hot to test the heat shield, because we want to have a highly reusable heat shield that's capable of absorbing heat from interplanetary entry velocities. So it's really tricky.

The ship part is by far the hardest because that's going to come in from super-orbital velocities. Mars transfer velocities these are way harder than coming in from low-earth orbit. There's some of the heating things that scale to the eighth power.  I diddn't think there's anything that scales to eight power but turns out on reentry certain elements of reentry heating scale to the 8th so just testing that ship out is the real tricky part.
The booster I think we understand reasonable boosters. Reusable spaceships that can land propulsively that's that's harder, so we're starting with the hard part first.
I think it's conceivable that we do our first full-up orbital test flight in 3-4 years including the booster.  inaudible question on moon/mars
 We'd go to low earth orbit first but it would be capable of going to the moon very shortly thereafter it's designed to do that.
« Last Edit: 02/07/2018 02:24 PM by speedevil »

Offline Lar

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Re: BFR or BFS first or both?
« Reply #45 on: 02/07/2018 03:22 PM »
Yep. Locked.
"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

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