Author Topic: Elon has changed BFR design again - what does this mean  (Read 520717 times)

Offline rakaydos

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Re: Elon has changed BFR design again - what does this mean
« Reply #260 on: 11/20/2018 05:50 am »
New Prediction:

Merlin based kerlox booster results in a reduced mass to orbit, but keeps the same methalox upper stage + payload bay we've seen. Long term expectation to develop a proper carbon fiber BFB, but that's up there with RaptorVac Development.

Offline RotoSequence

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Re: Elon has changed BFR design again - what does this mean
« Reply #261 on: 11/20/2018 06:07 am »
New Prediction:

Merlin based kerlox booster results in a reduced mass to orbit, but keeps the same methalox upper stage + payload bay we've seen. Long term expectation to develop a proper carbon fiber BFB, but that's up there with RaptorVac Development.

How would that be any faster or easier?

Online Robby the Robot

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Re: Elon has changed BFR design again - what does this mean
« Reply #262 on: 11/20/2018 06:16 am »
Would grid fins front and rear work for a skydiver re-entry? SpaceX know about about grid fins, less experience with wings.

I can easily imagine Falcon 9 S2 trials adding 4 grid fins and TPS to existing launch to gain experience on paid for launches with enough margin. I can't imagine adding tail fins.

If this works, is it better to have tail higher than nose? This could be Elon's  "counterintuitive" or it could simply be that out is counterintuitive to drop the wings on a horizontal entry ship..

Upthread, there was also much talk of a dome shaped nose being OK for a skydiver entry.  If this was the case, existing fairings could be used to launch existing payloads, saving a lot of cost and time in chomper development.  Remember that by the time BFS is launched, fairings will be recovered and reused.

Dragon, or Orion with LAS could also be mounted on the dome.  NASA will not be putting astronauts on BFS without LAS any time soon.

Remember that the biggest issue with BFS is funding, and Elon plans to solve that by transferring all F9 launch revenue to BFR/BFS, including satellites and dragon launches to ISS.  So why not cut the development cost. Use proven reuseable  fairings and dragons and get there faster and cheaper.

Offline hkultala

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Re: Elon has changed BFR design again - what does this mean
« Reply #263 on: 11/20/2018 06:35 am »
New Prediction:

Merlin based kerlox booster results in a reduced mass to orbit, but keeps the same methalox upper stage + payload bay we've seen. Long term expectation to develop a proper carbon fiber BFB, but that's up there with RaptorVac Development.

They already have
1) 3.6m aluminium tooling
2) 9m carbon fiber tooling

Making an aluminium-based intermediate vehicle bigger than 3.6 meters would only slow them down.

And when they have raptor engine for BFS, they can also manufacture raptor engine for BFB. Merlin would not save anything. Also engines using different fuels would just make launch operations more complex, meaning more time for constructing the launch infrastructure.


Things that are reasonable are legs instead of cradle for the early BFB.



Offline ppb

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Re: Elon has changed BFR design again - what does this mean
« Reply #264 on: 11/20/2018 06:45 am »
"Starship" is a bit too Virgin Galactic for my taste.
Oh well, if marketing didn't work I suppose so much money wouldn't be spent on it.
We built this missile on rock and roll.....

Offline Slarty1080

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Re: Elon has changed BFR design again - what does this mean
« Reply #265 on: 11/20/2018 06:52 am »
New Prediction:

Merlin based kerlox booster results in a reduced mass to orbit, but keeps the same methalox upper stage + payload bay we've seen. Long term expectation to develop a proper carbon fiber BFB, but that's up there with RaptorVac Development.

They already have
1) 3.6m aluminium tooling
2) 9m carbon fiber tooling

Making an aluminium-based intermediate vehicle bigger than 3.6 meters would only slow them down.

And when they have raptor engine for BFS, they can also manufacture raptor engine for BFB. Merlin would not save anything. Also engines using different fuels would just make launch operations more complex, meaning more time for constructing the launch infrastructure.


Things that are reasonable are legs instead of cradle for the early BFB.
Yes and they have already started building the 9m carbon fibre tanks
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline RotoSequence

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Re: Elon has changed BFR design again - what does this mean
« Reply #266 on: 11/20/2018 06:58 am »
Maybe I'm reading too much into this, but this tweet makes me wonder.

https://twitter.com/elonmusk/status/1064741510560632832

I can't easily recall an occasion where Elon made a wholly untruthful or farcical statement about his businesses' interests or intentions. Does anyone have such a recollection to bring me back down to Earth?

Offline niwax

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Re: Elon has changed BFR design again - what does this mean
« Reply #267 on: 11/20/2018 07:23 am »
Maybe I'm reading too much into this, but this tweet makes me wonder.

https://twitter.com/elonmusk/status/1064741510560632832

I can't easily recall an occasion where Elon made a wholly untruthful or farcical statement about his businesses' interests or intentions. Does anyone have such a recollection to bring me back down to Earth?


Gwynne Shotwell has definitely shown serious ambitions for interstellar travel. It won't exactly happen on BFR 1.0, but there are intentions within SpaceX to go further than Mars. She was also the driving factor behind P2P, so I wouldn't be surprised if the company doesn't at least spin off a research arm after they have regular solar system flights.

Which booster has the most soot? SpaceX booster launch history! (discussion)

Offline OneSpeed

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Re: Elon has changed BFR design again - what does this mean
« Reply #268 on: 11/20/2018 07:26 am »
Maybe I'm reading too much into this, but this tweet makes me wonder.

I can't easily recall an occasion where Elon made a wholly untruthful or farcical statement about his businesses' interests or intentions. Does anyone have such a recollection to bring me back down to Earth?

He's a Douglas Adams fan. He wants to name the starships as they were referred to in the Hitchhiker's Guide:

The starship "Heart of Gold", the starship "Bistromath", the starship "Business End" etc.

Offline RotoSequence

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Re: Elon has changed BFR design again - what does this mean
« Reply #269 on: 11/20/2018 07:30 am »
Maybe I'm reading too much into this, but this tweet makes me wonder.

I can't easily recall an occasion where Elon made a wholly untruthful or farcical statement about his businesses' interests or intentions. Does anyone have such a recollection to bring me back down to Earth?

He's a Douglas Adams fan. He wants to name the starships as they were referred to in the Hitchhiker's Guide:

The starship "Heart of Gold", the starship "Bistromath", the starship "Business End" etc.

It's less the "starship" part that's interesting than the "later versions will [be sent to another star system]" part. There aren't too many technologies that offer prospective shots at interstellar travel in the same time spans as the remaining lifetimes of SpaceX' executives.

Offline aameise9

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Elon has changed BFR design again - what does this mean
« Reply #270 on: 11/20/2018 07:41 am »
Maybe I'm reading too much into this, but this tweet makes me wonder.

https://twitter.com/elonmusk/status/1064741510560632832

I can't easily recall an occasion where Elon made a wholly untruthful or farcical statement about his businesses' interests or intentions. Does anyone have such a recollection to bring me back down to Earth?


Well, there was the "Cyborg Dragon" tweet back in July:

https://twitter.com/elonmusk/status/1011027339210317825

The worst conceivable possibility is that Mr. Musk's tweets are not the pronouncements of a wholly rational and responsible person.

Offline Lampyridae

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Re: Elon has changed BFR design again - what does this mean
« Reply #271 on: 11/20/2018 07:51 am »
The latest public skydiver reëntry config has two hinged wings/legs in the lower position and a fixed back fin/leg in the upper position.

Well, if you ditch the wing hinges and reduce the square-footage (but not the leg length) of the back fin so it becomes sizeably smaller than the other to fins... - what would happen then?

As I see it the skydiver position would flip around, with the two bigger fins going to the rear of the skydiving BFS.

So, Musks new "delightfully counter-intuitive" configuration could perhaps be three fixed fins/legs equally spaced 120 degrees apart. The two bigger fins jutting out from the upper back of the skydiving spaceship and the third belly-mounted fin pointing straight down, covered in TPS as the rest of the underside of the ship.

I think that would create a passively stable reëntry configuration on the roll axis.

It would also be a modification that wouldn't concern the body of the BFS too much.

Or to take the train of thought even further down this track, two upper fins on the back, perhaps looking much like the Tintin design fins, and one F9-style extending leg on the belly.

My intuition (for what it's worth) says the two Tintin fins should be passively stable during reentry, and the belly leg should produce no negative aerodynamic effects during reentry, plus be significantly lighter than the third Tintin leg-fin.

Yup, was thinking this. The "Starship" name makes me think they've made a design change which makes it visually resemble a certain well-known fictional starship, ie nacelles. The header tanks could be mounted outboard. After all, they're making the tanks, TPS already for the subscale technology demonstrator.

As for counter-intuitive, maybe it really is going to come in ass-first.

I can also see how they got there with the Tintin rocket. That came in backwards for reentry with the landing pods making air spikes.

For some reason it may all make sense in terms of CoG/CoL.

The Cyborg Dragon Tesla may be a reference to equipping a Tesla with cold gas braking thrusters which he did mention at one point.
« Last Edit: 11/20/2018 07:53 am by Lampyridae »

Offline RotoSequence

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Re: Elon has changed BFR design again - what does this mean
« Reply #272 on: 11/20/2018 07:53 am »
Well, there was the "Cyborg Dragon" tweet back in July:

The worst conceivable possibility is that Mr. Musk's tweets are not the pronouncements of a wholly rational and responsible person.

He has had plenty of off-the-wall stuff to talk about before, and where those things overlap with Tesla, SpaceX, Hyperloop, and Boring Company, he tends to follow through, cancel for changes in plans, or delay due to complications. Goofy or serious, he seems to mean what he says, for a given snapshot in time, when he talks about those four projects.
« Last Edit: 11/20/2018 07:54 am by RotoSequence »

Offline Eric Hedman

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Re: Elon has changed BFR design again - what does this mean
« Reply #273 on: 11/20/2018 07:57 am »
Why do I get the feeling Elon Musk said this just to read the comments in this forum?

Offline Lampyridae

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Re: Elon has changed BFR design again - what does this mean
« Reply #274 on: 11/20/2018 08:41 am »
Why do I get the feeling Elon Musk said this just to read the comments in this forum?

"Totally_Not_Elon" liked this post.

I think he's well aware that he drives rocket fans into a frenzy whenever he drops something cryptic that's SpaceX related, and he probably does it because he gets so excited that he just can't resist sharing it himself.

I'm just hoping that he will show mercy on us and present us with new CGI but then again he is rather a busy fellow.

Offline DJPledger

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Re: Elon has changed BFR design again - what does this mean
« Reply #275 on: 11/20/2018 08:44 am »
Time to rename threads in this section to Starship (previously BFS) and Super Heavy (previously BFB) please.

Offline FutureSpaceTourist

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Re: Elon has changed BFR design again - what does this mean
« Reply #276 on: 11/20/2018 08:57 am »
Cross-posting, Elon is going all in on Starship acceleration:

Oh well

https://twitter.com/universal_sci/status/1064738867419455489

https://twitter.com/elonmusk/status/1064740532700643329

Quote
No, we’re just going to accelerate BFR

Makes me think the redesign doesn’t need the data from F9 S2 mini-BFR rentry/control like the previous TinTin design did.

Offline Star One

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Re: Elon has changed BFR design again - what does this mean
« Reply #277 on: 11/20/2018 09:01 am »
Does Musk observe the BFR/BFS nomenclature in his tweets?

We here routinely use BFR/BFS/BFB/BFC/BFD...  But I am not sure Musk always does.

Hmmm what were you saying about Elon not differentiating in his use of naming, well he certainly has now!

Offline nacnud

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Re: Elon has changed BFR design again - what does this mean
« Reply #278 on: 11/20/2018 09:09 am »
Does Musk observe the BFR/BFS nomenclature in his tweets?

We here routinely use BFR/BFS/BFB/BFC/BFD...  But I am not sure Musk always does.

Hmmm what were you saying about Elon not differentiating in his use of naming, well he certainly has now!

I dont think the BFR really had a name, just a nickname, now it's been named, possibly.

BFR > ITS > BFR > Starship (for now)

Offline Star One

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Re: Elon has changed BFR design again - what does this mean
« Reply #279 on: 11/20/2018 09:19 am »
Maybe I'm reading too much into this, but this tweet makes me wonder.

https://twitter.com/elonmusk/status/1064741510560632832

I can't easily recall an occasion where Elon made a wholly untruthful or farcical statement about his businesses' interests or intentions. Does anyone have such a recollection to bring me back down to Earth?

No doubt the internet will go nuts, or certain parts will with people going what does he know that the rest of us don’t!

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