It is my understanding that BFS Mars reentry from Earth-Mars transit will require a nose DOWN (but still positive AOA) attitude in order to generate a lift component towards Mars. This is to prevent BFS from re-exiting the atmosphere, because the incoming velocity will be higher than LMO velocity. OTOH, I am assuming reentry from LMO (or LEO) will be done nose UP, ala STS. Are these assumptions correct?
Sure, it's might have only a limited time of usage, since BFR/BFS will be there soon. But still, SpaceX needs to learn a few things, and if they can learn while somebody else is paying for it... that'd be great.
Quote from: Hotblack Desiato on 11/10/2018 05:41 pmSure, it's might have only a limited time of usage, since BFR/BFS will be there soon. But still, SpaceX needs to learn a few things, and if they can learn while somebody else is paying for it... that'd be great.And SpaceX would be subject to a whole new round of NASA paperwork... BFR would be retired by the time that thing took crew to the ISS.
Quote from: Robotbeat on 11/10/2018 12:06 amQuote from: JamesH65 on 11/09/2018 12:12 pmI seriously doubt any customers would be happy for a completely different and untested 2nd stage to be used for their very expensive payload launch. Especially one with aero surfaces poking out....The first flight of Falcon 9 with legs folded up occurred on CRS-5 with Dragon.This is almost the same kind of thing, depending on how exactly they design the recovery system.No, it really isn't. Taking musk at his word this is like a mini bfs. A major change to the current second stage. With fins and an entirely different payload deployment mechanism. ...
Quote from: JamesH65 on 11/09/2018 12:12 pmI seriously doubt any customers would be happy for a completely different and untested 2nd stage to be used for their very expensive payload launch. Especially one with aero surfaces poking out....The first flight of Falcon 9 with legs folded up occurred on CRS-5 with Dragon.This is almost the same kind of thing, depending on how exactly they design the recovery system.
I seriously doubt any customers would be happy for a completely different and untested 2nd stage to be used for their very expensive payload launch. Especially one with aero surfaces poking out....
Quote from: indaco1 on 11/10/2018 02:08 pmNo, I don't mean de-orbit burn. I mean use engine during re-entry to follow a trajectory that put less stress on TPS.No, it will use the RCS and fins to pitch, bank, and roll to manage the energy and heating until the velocity is bled off for controlled free fall...
No, I don't mean de-orbit burn. I mean use engine during re-entry to follow a trajectory that put less stress on TPS.
So the problem is, the structure will be bottom-heavy because the engine is there, and everything else is mostly an empty tank.
Quote from: Rocket Science on 11/10/2018 02:33 pmQuote from: indaco1 on 11/10/2018 02:08 pmNo, I don't mean de-orbit burn. I mean use engine during re-entry to follow a trajectory that put less stress on TPS.No, it will use the RCS and fins to pitch, bank, and roll to manage the energy and heating until the velocity is bled off for controlled free fall...Then pretty much a Shuttle style re-entry - hopefully lighter.John
Quote from: John-H on 11/10/2018 09:52 pmQuote from: Rocket Science on 11/10/2018 02:33 pmQuote from: indaco1 on 11/10/2018 02:08 pmNo, I don't mean de-orbit burn. I mean use engine during re-entry to follow a trajectory that put less stress on TPS.No, it will use the RCS and fins to pitch, bank, and roll to manage the energy and heating until the velocity is bled off for controlled free fall...Then pretty much a Shuttle style re-entry - hopefully lighter.JohnAs others have said, very different. To start with, STS had a L/D ratio that in very round numbers was 1 (ish). This beast will have a L/D that is close to a much rounder number (zero.)
Don't get too fixated on L/D, you can get creative with entry profiles such as Apollo IV "double dip'" entry. I'm sure SpaceX is bound to do some surprising with this unique vehicle...
Quote from: Rocket Science on 11/11/2018 02:08 pmDon't get too fixated on L/D, you can get creative with entry profiles such as Apollo IV "double dip'" entry. I'm sure SpaceX is bound to do some surprising with this unique vehicle...Quite. However, people seem fixated on 'belly flop' - and assuming it has absolutely no lift, which is absolutely false.The potential entries from over low orbital speed are varied.The potential entries that keep under 6G or so all require some degree of lift. (or of course propulsion to provide that lift, which is not part of the baseline BFR)