variable drive

[jacobmuller]

I don't know if this is covered somewhere but I do know I don't know how to figure it out:)

A reactionless drive with thrust that varies with local gravity, eg low orbit 1G, 50,000 miles out 0.005G, per drive.

Problem for me being, there's formulae there for #G and distances etc but what happens to the math when G varies according to distance to/from a source?

I don't want a fixed reactionless drive system but if the math gets too painful I might settle for a "only works in significant G" fiat, ie only surface to orbit.