Those orbital numbers are sobering, but there may still be plenty of reason to investigate a launch mechanism where the "fuel" comes from an external source. I

Those orbital numbers are sobering, but there may still be plenty of reason to investigate a launch mechanism where the "fuel" comes from an external source. I haven't run the numbers, but a quick look at typical delta-V budgets [1] (which calculate atmospheric losses as 1.5 to 2 km/s of delta-v), if one could accelerate something fast enough that it escapes most of Earth's atmosphere (and only then burn for orbital velocity), you'd be saving ~17 to 20% on the delta-v requirements. Due to the nature of the Tsiolkovsky equation, that could be a very substantial saving. That said, I'm also wondering why a centrifuge would be better than say, some kind of low pressure tube / rail, but I'm sure these guys have done their maths and believe in it. [1] https://en.wikipedia.org/wiki/Delta-v_budget https://en.wikipedia.org/wiki/Delta-v_budget