Nuclear Powered Aliens

[Nereidalbel]

Originally Posted by Varyon

I'm considering having their photosynthesis have roughly 10% efficiency (a brief bit of research indicates this is somewhere near the theoretical maximum for biological photosynthesis - or at least photosynthesis based around chlorophyll),

If you gene-splice your ships to use bacteriochlorophyll in addition to chlorophyll, you'll get a significant boost to energy production from sunlight alone.

As for converting ionizing radiation into food, melanin-containing fungi are actually pretty good at that.

If you can genetically engineer most of the biological inefficiencies from natural evolution, you can probably have bio-ships powered mostly by photosynthesis and radiosynthesis, with the occasional infusion of what amounts to fertilizer. In fact, that can be a pretty good way to handle biological waste from the life forms on board...

[acrosome]

If your ships are going to be making food in any form that approaches what we are used to calling food, they will need more than "occasional fertilizer". Food is matter. So where is the mass coming from on a ship in space?

They will need some sort of bulk matter input, unless they are highly closed systems recycling waste products. (Which I guess could be what you all are trying to say, but then it would make more sense to call it a closed life-support system.) Even plants here on Earth take matter in from the ground and even more so in the form of carbon dioxide to get the carbon to make sugars.