I agree with you, but N1 isn't something that "speaks in favour" of having many smaller engines instead of few big engines, though.
I think Musk's talk tomorrow will follow more or less the following logic: ...7) Makes case for public-private partnerships. "Cannot do this without NASA. But NASA might not be able to do this without us." Presents clever funding scheme which will keep them running with a small fraction of what NASA invests in SLS every year. "NASA should diversify", not only SLS but also alternatives in case rocket grounded after mishap. Multiple plans, "also Blue Origin", should keep us on track to Mars.
O.K. I want to change my guess for number of engines from 31 to 27.And this isn't just because Musk informed us that the thrust is going to be higher than previously hinted at. It's also because I realized that, while 31 gives a very nice, minimum diameter packing pattern with a single center engine (like the F9), having a single center (landing) engine is probably not appropriate or desired here. It's unlikely that the BFR could land on a single engine - just too heavy. 3 centralized engines would probably be appropriate. And the nice symetrical, minimum pattern for 3 center engines comes out to be 27.We'll know in just over a day (I hope).
Quote from: Bynaus on 09/26/2016 07:02 pmI think Musk's talk tomorrow will follow more or less the following logic: ...7) Makes case for public-private partnerships. "Cannot do this without NASA. But NASA might not be able to do this without us." Presents clever funding scheme which will keep them running with a small fraction of what NASA invests in SLS every year. "NASA should diversify", not only SLS but also alternatives in case rocket grounded after mishap. Multiple plans, "also Blue Origin", should keep us on track to Mars. I like your thinking save for #7. Musk will, as usual, praise NASA as an excellent partner. But he will be wise to avoid any mention of SLS or NASA 'needing' SpaceX. I can think of many a Senator and Congressperson who will already feel threatened by the reveal of BFR. Musk's best bet is to avoid either-or comparisons between The US Govt.'s Rocket and his own. Rather, emphasize that SpaceX's system will be yet another tool available in the public/private toolbox of US Space Exploration over the years to come.Finally, I would add one to your list:2.5) Red Dragon in ~2018; emphasize SX-NASA cooperation, demonstration of ISRU on-planet.
I'm revising BFR diameter down to a range of 10 - 12 m based on Musk comment on raptor being comparable to Merlin size but carrying 3x thrust.That completely rules out 15 m diameters, a vehicle that size is approximately 9x the base area of F9, with triple thrust density of Raptor would lead to 27x the thrust of F9 or something close to 45 million pounds of thrust, 3x times what Musk has aimed for.Fundamentally the 15 m speculation was nothing more then a crude attempt to multiply the thrust of F9 by a factor of 9 while completely ignoring the thrust density improvements that come from the full-flow staged combustion cycle.
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Quote from: Impaler on 09/26/2016 09:24 pmI'm revising BFR diameter down to a range of 10 - 12 m based on Musk comment on raptor being comparable to Merlin size but carrying 3x thrust.That completely rules out 15 m diameters, a vehicle that size is approximately 9x the base area of F9, with triple thrust density of Raptor would lead to 27x the thrust of F9 or something close to 45 million pounds of thrust, 3x times what Musk has aimed for.Fundamentally the 15 m speculation was nothing more then a crude attempt to multiply the thrust of F9 by a factor of 9 while completely ignoring the thrust density improvements that come from the full-flow staged combustion cycle.The 15 m diameter speculation had little to do with individual engine thrust. 1. Various attempts have been made to optimise the BFR mass, these give least tank mass for a 13-15 m stage.2. The BFS has been said by Musk to be very large, a scaled Dragon capsule design might have to be over 23 m, which would fit much more easily on a 15 m stage. Biconic or semi-lifting body BFS designs would seem to need 12-15 m diameter to enclose the inidcated volume.3. L2 info and various leaks on reddit
but then, if they cannot do it on their own, he has to make the case why it would be a good thing for NASA to invest some money in the SpaceX plan
SpaceX has what NASA needs. SX are being paid 1.6B for it. And then there's CRS-2. That's quite some money invested by NASA into the SpaceX plan
Quote from: mfck on 09/26/2016 09:46 pmSpaceX has what NASA needs. SX are being paid 1.6B for it. And then there's CRS-2. That's quite some money invested by NASA into the SpaceX planThat's NASA purchasing services at a very good price.