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
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.
Quote from: ZachF on 11/18/2018 01:22 amHere'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?
Putting the payload bay on the bottom would probably smooth out ground operations as well.
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".
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.