SpaceX Mega-Starship

What comes next after a rocket with 3X the power of Saturn V

Starship is a prodigiously powerful vehicle, with three times the thrust of a Saturn V moon rocket and twice the payload – plus fully reusable! However, even this enormous vehicle lacks the lifting power necessary to create a city on Mars, Elon Musk’s enduring vision. Hence he is already planning the next evolutionary step in SpaceX’s rocket building program.

“Starship will lengthen in the next few years. 10 years from now, there will probably be a much wider diameter Starship too.” ~ Elon Musk/X

“Probably 18m [diameter] for next gen [launch] system” ~ Elon Musk/X

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Elon has yet to name this behemoth vehicle, although ‘Starlifter’ seems appropriate considering its capabilities and antecedence. An 118m high x 18m diameter vehicle could carry four times more than Starship, putting it at ~1,000 tons payload with 4,000 cubic meters of pressurized volume. This would allow extremely large pieces of equipment to be launched fully assembled, e.g. a full scale propellant production plant or nuclear reactor core, significantly reducing the installation work required on Mars. More importantly it would reduce the launch cadence from 135 per month for Starship, down to 33 for Starlifter, a far more manageable figure.

Of course engineering such a beast would be challenging to say the least. For example Starship will have 44 Raptor engines in total, which suggests Starlifter would need 176, if the same engines were used. SpaceX always seeks to reduce the complexity of their systems, so it seems likely they will produce a significantly more powerful engine specifically for the Starlifter vehicle.

“Raptor [version] 2 has significant improvements in every way, but a complete design overhaul is necessary for the engine that can actually make life multiplanetary. It won’t be called Raptor.” ~ Elon Musk/X

Ideally this new engine would be around ten times more powerful than Raptor, i.e. produce ~2,800 tons of thrust, reducing the engine count to roughly 17 in total. This would provide adequate redundancy in case of an engine out, plus minimize the amount of pipework, hence reduce the overall complexity and increase reliability. Conventional wisdom suggests big engines suffer from combustion instability, certainly the case for the F1, the main engine used on Saturn V. Fortunately SpaceX employs powerful computational fluid dynamics to model the combustion process and will likely use some form of staged combustion to help minimize any instability. While the technical challenges are enormous for Starlifter, it would raise the bar for what is possible in space, opening myriad new possibilities...