Author Topic: BFR or BFS first or both?  (Read 4573 times)

Online 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?

Online 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 »

Online 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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Offline FutureMartian97

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 »

Online 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 »

Online 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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Online 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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Online 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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Online 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.

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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).

Online 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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