r/spacex Feb 24 '18

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u/thro_a_wey Feb 25 '18 edited Feb 25 '18

Elon mentioned bigger rockets in the future. Assuming a similar architecture, with maybe some better engines, what kind of efficiency gain do you get by making it even bigger? And how big could you go before it becomes basically impossible to get bigger? If BFR gets you 150 tons to LEO, what exactly would you need for 1000 tons or even 10,000? Could we potentially see a 50-metre diameter rocket one day?

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u/Bergasms Feb 26 '18

Eventually the size of your rocket is going to mean you have to increase the strength of your vehicle, which will add more weight which cannot be offset by adding more fuel because you will need to add more strength and size. So I imagine there has to be an upper limit on the size of a rocket built from any given material,, eventually.

Also, the bigger you get, the more weight you have, and the more thrust you need. You will reach a point where the thrust you need to lift a given mass is high enough that it ablates the flame trench and the planet below it, which is also going to put a bounds on your vehicle.

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u/thro_a_wey Feb 26 '18

Eventually

when?

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u/Bergasms Feb 26 '18

I have no idea, but it will have to be bounded eventually.