Este, the prison facility isn't a ship...it's a ground-based complex located on a rocky moon orbiting a gas giant planet. You don't have to make any modifications, just letting you know.
Also, if you yourself are interested in some of the technical reasons I made up for certain things being possible...Since the facility is in a constant regular-space existence, it can make use of an active artificial singularity for a power-source. The singularity cannot be shut down, so in the case of emergency shut-down, the best they can do is cut the power flow coming from the singularity itself. And it's not exactly an easy process. It takes two, working simultaneously, and it takes special command codes to unlock the coupling-breakers. The codes Ossanlin and Norry entered before disarming the couplings. Ships that make use of Z-Space can't use this type of power supply as Z-Space nullifies the singularity, or in some rare cases, causes a catastrophic release of energy which produces a "null" patch in Z-space...incidentally, it also decomposes all forms of physical matter within a spherical area that more than engulfs the area of the ship that it was supposed to be powering.
There are backup sources of power...for example, the computer has its own backup system, but Esarvit and Aurellia have taken care of that. The Virus that Esarvit uploaded actually locked down all rooms and levels of the facility that the Rogues don't need to access to. The loss of power to the computer locked it into its current phase. Any doors the facility Andalites need to get through will have to be cut open. Once they restore power, they can work around things, but by that time, the Rogues should be long gone with the liberated Rebels.
