"very cool! keep us posted on flight times!"

"Absolutely!! Its super easy to cut Sunpower cells once you get the hang of it. You can do it with a Dremel, laser cutter or any other number of methods. In terms of efficiency, the ones of Alibaba (now plenty available on ebay) are all genuine…"

"alibaba.com is a great place to get a very large, low-cost envelope. you can specify materials and envelope thickness with most of the manufacturers. add an Arduino-based blimp controller board, motors, props, maybe an internal…"

"Foldable vs non-foldable doesn't drive efficiency as much as geometry. Foldable will tend to be heavier as more structure is needed, but a good design shouldn't impact efficiency too much. "

"Srikanth, if you are looking for a quadcopter-type, that will be tough, but not impossible and you'd definitely have to build it from scratch with a super-low disc loading.  For reference at an extreme end of the scale (human-powered flight), the…"