When the relevant numbers for the Ymir retrieval mission were jacked into the Tsiolkovskii equation, the result was a mass ratio of about seven, meaning that for every kilogram of stuff—Markus, Dinah, other personnel, miscellaneous robots, etc.—that they wanted to arrive safely at the docking port of Ymir, they needed to allow for six kilograms of propellant at the moment of departure from Izzy. This wasn’t all that difficult to achieve, especially for a vehicle that would never be exposed to the rigors of passage through the atmosphere.