Oooh, I want one, but so expensive.

The brownie edges I believe are the result of different heat transfer where the batter touches the pan -- the batter at the edges (and bottom) is subject to conductive instead of convective heating. So if there was a way to cook without a pan, I suppose it would be all "middles". A spherical pan would still have "edges" over its surface. But I suppose on the space shuttle, the liquid batter would form a sphere and theoretically be cooked without a pan if you could keep it from moving and touching the sides of the oven. However, in either case, the thickness of the sphere would probably cause difficulty cooking the batter thoroughly. (More like a cake, you'd be relying on heat to make its way deep into the batter. So it wouldn't really be "middles" either.)

This did make me realize that a pie pan or round, shallow cake pan would maximize the middle/edge ratio of standard brownies. Something to try next time.