I was wondering if there were a way to calculate the mass of an object given only its velocity relative to its primary and the radius of its orbit, assuming an eccentricity of 0. (Or given its mean orbital radius, where

*e*< 1.)

This would be useful as a quicker way of discovering the mass of a cluster of docked vessels in Orbiter, so long as I needed an accuracy no better than 4 significant digits.