[Suicide Junkie]

My point is that the power source dosen't matter.
They need to have some energy generation in order to stay alive and operating.
If they were to have no emmissions, then the temperature of the ship would have to rise. On a temporary basis that can be handled, but these ships run on gigawatts. Lifesupport, artificial gravity, structural integrity, containment fields, doors & lifts, and all the bells and whistles. It won't take long before they have to release the waste heat or melt into a bubble of expensive goo.