this month's issue of scientific american has a couple articles which may be of interest to extropians. there is one on nanomotors with a good explanation of why feynman suggested such a thing could not extract heat from a medium without violating the laws of thermodynamics.
another article is a sober summary of our future rides into orbit including an old fave on this list the roton.
on the subject of rotons: i notice they are still concentrating on the helicopter reentry systems. what if they skipped that part, used the weight delta to lift the entire craft into an orbit that will be stable for 20 years, then use the empty vehicles for raw materials in orbit? seems like that would be much more valuable up there than bringing it all back each time. if they accomplish true single stage to orbit, even if it is expendable, we can manufacture the things by the zillions and still get payload to orbit for less than 5k$/kg. spike