Author Topic: Elon has changed BRF design again - what does this mean  (Read 5981 times)

Online docmordrid

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Re: Elon has changed BRF design again - what does this mean
« Reply #60 on: Today at 01:12 AM »
Musk needs to get the CGI people busy and schedule that AMA. Soon. Sooner than soon.
DM

Offline Rocket Science

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Re: Elon has changed BRF design again - what does this mean
« Reply #61 on: Today at 01:14 AM »
He's come to his senses and is building this...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator, Vintage auto racer

Offline robert_d

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Re: Elon has changed BRF design again - what does this mean
« Reply #62 on: Today at 01:22 AM »

Second Idea:

Upper stage will use a ring of raptor-based linear aerospike engines and the payload will be able to be unloaded on the bottom

Totally concentric construction might solve some problems and work well with the carbon composite construction.

Offline ZachF

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Re: Elon has changed BRF design again - what does this mean
« Reply #63 on: Today at 01:22 AM »
Here's what I mean:

The counter-intuitive part would be that the giant window would be facing "down" on the manned version.

it would be immeasurably easier to load and unload cargo.

could also "hot stage" with this design.

EDIT: Also when refueling you could connect the manned areas,
« Last Edit: Today at 01:25 AM by ZachF »

Offline robert_d

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Re: Elon has changed BRF design again - what does this mean
« Reply #64 on: Today at 01:26 AM »
Here's what I mean:

The counter-intuitive part would be that the giant window would be facing "down" on the manned version.

it would be immeasurably easier to load and unload cargo.

could also "hot stage" with this design.
Hard to see how aerospike could accelerate development, however. Couldn't they just put two engines in each of the fins and call it good?

Offline ZachF

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Re: Elon has changed BRF design again - what does this mean
« Reply #65 on: Today at 01:28 AM »
Here's what I mean:

The counter-intuitive part would be that the giant window would be facing "down" on the manned version.

it would be immeasurably easier to load and unload cargo.

could also "hot stage" with this design.
Hard to see how aerospike could accelerate development, however. Couldn't they just put two engines in each of the fins and call it good?

They could use a ring of SL raptors at first and upgrade to linear aerospikes later.

Offline ZachF

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Re: Elon has changed BRF design again - what does this mean
« Reply #66 on: Today at 01:29 AM »
Putting the payload bay on the bottom would probably smooth out ground operations as well.

Offline Oli

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Re: Elon has changed BRF design again - what does this mean
« Reply #67 on: Today at 01:31 AM »
Putting the payload bay on the bottom would probably smooth out ground operations as well.

Yep, it would enter bottom-first and create a nice crater on impact.  ;)

Offline daveklingler

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Re: Elon has changed BRF design again - what does this mean
« Reply #68 on: Today at 02:44 AM »
Hm. Counterintuitive...

Counterintuitive, to me, would mean they've dropped Mars as a destination, adopted plans to build O'Neill colonies, and BFR is now SSTO.

Online zodiacchris

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Re: Elon has changed BRF design again - what does this mean
« Reply #69 on: Today at 02:53 AM »
Oh boy, what have you guys been smoking??? ::)

Offline OxCartMark

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Re: Elon has changed BRF design again - what does this mean
« Reply #70 on: Today at 03:07 AM »
Rotate engines 90 degrees so that exhaust now goes out perpendicular to vertical, all engines arrayed around cylinder so as to create rotation around long axis.  Add DaVinci helicopter rotor to nose end of BFS to generate lift in lower atmosphere.  Once high enough that atmospheric lift is no longer effective the liquid propellants will be rotating around tank perimeter with enough speed that strategically placed tank vents could be opened to jet the rapidly moving fuel in the direction needed to provide the remainder of necessary thrust.  Side benefits: artificial gravity, exposes all sides to reentry heating, magnus effect steering. 

Its not intuitive.

edit: upon further reflection I see another side benefit, a significant one: centrifuged cryogenic fuel against outer skin during reentry would reduce the need for heat shielding.  I've not done the calculations but one possibility is that with cryogenic liquids on the back side of the carbon composite skin there may(?) be no need for any heat shielding at all.
« Last Edit: Today at 03:26 AM by OxCartMark »

Offline su27k

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Re: Elon has changed BRF design again - what does this mean
« Reply #71 on: Today at 03:31 AM »
I bet none of us can guess correctly what SpaceX is up to, it's the aft-cargo fiasco all over again.

1. SSTO: Too early in the prototyping process to bet on this. Besides, it's the intuitive solution, not counter-intuitive
2. Move cargo to the bottom: They already considered this option before and rejected it due to cost/complexity(?) reasons, don't see why they want to get back to it when they are "accelerating"
3. Capsule: Same as #2
4. Dome nose: This one actually makes sense and it's sort of counter-intuitive, but I don't think it's a "radical change".


Offline DanielW

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Re: Elon has changed BRF design again - what does this mean
« Reply #72 on: Today at 03:38 AM »
I take this tweet as confirmation that Musk has latched on to my idea of launching the BFS into space sideways. The raptors point in the direction of the heat shield allowing a horizontal entry and landing.

The important bit is that for a few blessed days or months all of our pet ideas are back in play, unbound by inconvenient realities.

Online kessdawg

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Re: Elon has changed BRF design again - what does this mean
« Reply #73 on: Today at 03:42 AM »
BFS now stands for Big Falcon Skyhook, and is now a rotating cable in orbit that flings payloads from the upper atmosphere into orbit?

Offline dwheeler

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Re: Elon has changed BRF design again - what does this mean
« Reply #74 on: Today at 04:19 AM »
Hope I'm wrong, but before we get too carried away there is another interpretation that should be considered:

"Btw, SpaceX is no longer planning to upgrade Falcon 9 second stage for reusability. Accelerating BFR instead. New design is very exciting! Delightfully counter-intuitive."

I think Musk means the "new" (but previously announced) 2018 version BRF tintin design is very exciting and delightfully counter-intuitive. I don't think there's been any further change. He's just commenting on the current design which is "new".

I'm leaning this way. In the Sept 2018 presentation he referred to the new skydiver design specifically as "counter-intuitive". That's the "radical" change he's talking about IMO. I would speculate there was an internal project still investigating a plan to make F9 S2 reusable and that plan is now quashed. So I think the mini-BFR F9 S2 plan is still full speed ahead (as a re-entry test bed IMO).

Online groundbound

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Re: Elon has changed BRF design again - what does this mean
« Reply #75 on: Today at 04:49 AM »
Rotate engines 90 degrees so that exhaust now goes out perpendicular to vertical, all engines arrayed around cylinder so as to create rotation around long axis.  Add DaVinci helicopter rotor to nose end of BFS to generate lift in lower atmosphere.  Once high enough that atmospheric lift is no longer effective the liquid propellants will be rotating around tank perimeter with enough speed that strategically placed tank vents could be opened to jet the rapidly moving fuel in the direction needed to provide the remainder of necessary thrust.  Side benefits: artificial gravity, exposes all sides to reentry heating, magnus effect steering. 

Its not intuitive.

edit: upon further reflection I see another side benefit, a significant one: centrifuged cryogenic fuel against outer skin during reentry would reduce the need for heat shielding.  I've not done the calculations but one possibility is that with cryogenic liquids on the back side of the carbon composite skin there may(?) be no need for any heat shielding at all.

IIRC, our own HMXHMX has more or less been-there-done-that.  :)

Online drzerg

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Re: Elon has changed BRF design again - what does this mean
« Reply #76 on: Today at 05:02 AM »
Bfs will sit on sls for nasa missions.

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