Only a mecha equipped with space skin (see Miscellaneous Equipment) can operate in outer space. However, the mecha's operator takes a -4 penalty on all attack rolls and skill checks unless she has the Zero-G Training feat or has equipped her mecha with a zero-g stabilizer.
In outer space, mecha fly just like they do in the atmosphere, with three exceptions. First, all flying mecha improve by one maneuverability category (clumsy becomes poor, poor becomes average, average becomes good, and so on). Second, all mecha can ascend and descend regardless of the limitations on Table: Flight Maneuverability, and their speed is unchanged if they do so. Finally, all mecha can hover in space and need not maintain a minimum forward speed.