I was thinking that lettuce production could be made a "mass production" system relatively easy with 3 systems. I wanted to run my thoughts through here and see what people think.
First system is the seed starting system. It will be a virtical stack of rails each with an NFT/spray system. (similar to the one I have on my first system) The rows will only be about 6 inches apart from eachother (virtical spacing) to let you put a large number of rows on top of eachother. The water will be able to get more airation through the splashing of the spray. And you can have a single Flouresent fixture on a hing to fold down to provide light to young seedlings. and you can get small plastic trays from your local garden shop to serve as humidity domes over each plant.
Second system would be similar. Probably slightly higher spacing virtically. The
lights can be mounted just below the rail above, or still be able to hing towards the rear of the unit to allow more functional space when moving plants in and out. This system would be running the light strength
nutrients, and would be for the mid ranged plants.
The third system would be the production system. This is where the mature plants will be and could have a few different designs... I would think an angled rail would be more space efficient with the roots being developed by this point. You could have this one with natural or supplimental lighting as needed.
This wouldnt take much room and could probably be downsized to a few 2ft wall spaces (with 2ft flourescent lights) with ease, and would let you produce much more lettuce than a single family could eat in most cases :P
This is just a thought. Let me know what you think and I might make a set for the personal entertainment value :P