With the announcement of the BFS with slight revisions for the circumlunar flight. Could you stick 3 to 5 Merlin SL engines to the F9 upper stage and use the external exhaust nozzle like on the revised BFS? At least as a prototype for the BFS.
That depends on the design.If you increase the area enough, you can end up with the deceleration happening very very high
There are so many ways inflatables can help with reentry varying from complex fragile designs to really quite dumb, and we have almost no indication what SpaceX may be trying.
Quote from: Zed_Noir on 09/14/2018 05:33 amWith the announcement of the BFS with slight revisions for the circumlunar flight. Could you stick 3 to 5 Merlin SL engines to the F9 upper stage and use the external exhaust nozzle like on the revised BFS? At least as a prototype for the BFS."external exhaust nozzle"? Major BFS conjecture alert, here. Raptor is a significantly higher performing engine (more like SSME than M1D), which may make losing the extended nozzle less of an issue than it would be for Merlin.Besides, putting 3-5 merlins on a F9 upper stage... The single M-Vac already has to throttle down before burnout to reduce G-loads on payloads. Now imagine 4x more power. No.
Quote from: Zed_Noir on 09/14/2018 05:33 amWith the announcement of the BFS with slight revisions for the circumlunar flight. Could you stick 3 to 5 Merlin SL engines to the F9 upper stage and use the external exhaust nozzle like on the revised BFS? At least as a prototype for the BFS.'yes'.And there is a thread for that!If the aimed at Mars date is in fact 2022, the value of prototypes may be small, as it's very much not a gradual program.A crash program on BFR, plus a backup program to make second stages reusable may make more sense than trying to build a vehicle whose purpose will go away.BFS can be quite bad and still get to Mars
Quote from: Lars-J on 09/14/2018 06:50 amBesides, putting 3-5 merlins on a F9 upper stage... The single M-Vac already has to throttle down before burnout to reduce G-loads on payloads. Now imagine 4x more power. No.Of course the overall thrust of the upper stage have to throttle down near burnout. But if you have like 3 Merlins when the upper stage ignites. Then it will only be about 3G acceleration to began with. So a shorter burn time and shorter transit time to the targeted orbit. Presuming there is some method to maintain the engine exhaust ISP near the Merlin Vac's ISP.
Besides, putting 3-5 merlins on a F9 upper stage... The single M-Vac already has to throttle down before burnout to reduce G-loads on payloads. Now imagine 4x more power. No.
Quote from: Zed_Noir on 09/14/2018 05:33 amWith the announcement of the BFS with slight revisions for the circumlunar flight. Could you stick 3 to 5 Merlin SL engines to the F9 upper stage and use the external exhaust nozzle like on the revised BFS? At least as a prototype for the BFS.I really don't get it. What benefit are they supposed to get from that?It seems like a distraction to me that would be an enormous amount of work (think Falcon Heavy -- it's just putting three first stages together, but it turned out to be far more work than even SpaceX had thought) and tell them almost nothing useful.The best way to prototype to learn something to help BFS development is build the first BFS. Anything else is just a distraction.
https://twitter.com/elonmusk/status/1060253333116473344https://twitter.com/elonmusk/status/1060253755315118080This makes sense for two reasons:1. FCC has denied a waiver for shorter deployment timeline. So SpaceX has to launch thousands of satellites in the next 6 years. They need reusable second stage and more powerful stage for FH would be welcome.2. They can use this as a BFS prototype.
Well that was 933 posts for nothing.
Quote from: TrevorMonty on 11/17/2018 08:09 pmWell that was 933 posts for nothing.What did you expect? This is Elon Musk we are talking about.
Quote from: woods170 on 11/17/2018 08:12 pmQuote from: TrevorMonty on 11/17/2018 08:09 pmWell that was 933 posts for nothing.What did you expect? This is Elon Musk we are talking about.It's also NSF. This forum could spend 933 posts discussing if the next BFR will be chicken-powered.
Quote from: niwax on 11/17/2018 08:20 pmQuote from: woods170 on 11/17/2018 08:12 pmQuote from: TrevorMonty on 11/17/2018 08:09 pmWell that was 933 posts for nothing.What did you expect? This is Elon Musk we are talking about.It's also NSF. This forum could spend 933 posts discussing if the next BFR will be chicken-powered.Chicken power confirmed!