Scaling Up Internal Mass Drivers?

Internal mass drivers are a potentially useful space drive, due to the ready availability of reaction mass (you can use anything from spare parts to literal dirt as a propellant, assuming you have a ferromagnetic bucket that you decelerate and retrieve at the end). However, on long trips on which in situ resource utilization may not be available, especially interstellar generation-ship trips, one would want a higher exhaust velocity, to maximize the fuel efficiency of the drive.

The excellent Atomic Rockets site contains this set of stats for a mass driver, but the exhaust velocity of 30 km/s isn't quite up to scratch for an interstellar spacecraft, even if you simply strap your craft to a convenient small asteroid to use for fuel. If we were to multiply the length of the drive by ten, according to the equation $v_f^2 = v_i^2 + 2a \Delta d$ (relativistic effects are negligible at these velocities, so we can ignore them), for a mass driver with the same acceleration, but ten times longer, we get an exhaust velocity of a bit under 95km/s, which is quite a bit nicer, even though we had to increase the mass of the drive and its power source by a factor of ten to increase the exhaust velocity by a factor of a bit over three. However, I don't know if it's actually possible to scale up a mass driver in the way I've described.

Would it be possible to scale up a Mass Driver by simply making it longer? Are there any factors that would require the mass to increase more than would be assumed from a simple "make it longer" perspective? Are there any other factors I'm not considering here?

posted almost 6 years ago

Gryphon‭

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