Kalpana One

The most recent proposal for a self-sufficient space colony that I’ve seen.  Its designers looked at the earlier Bernal, Stanford and O’Neill proposals and came up with something that improved on them.  The most interesting aspect of Kalpana One to me is the way it’s only 325 m long (and 250 m in radius) -- yet can have as much as 1,142,000 square meters of living space inside!  The secret?  It’s not just one hollow cylinder but a set of concentric cylinders.

The proposal is named for Dr. Kalpana Chawla, one of the astronauts killed in the shuttle Columbia disaster.  There’s also an unrelated real-life satellite called Kalpana-1 that India launched a while back, in case you want to look this up further.