hal@finney.org wrote:
>
> > http://news.bbc.co.uk/hi/english/sci/tech/newsid_1037000/1037730.stm
> >
> > The first microscopic "helicopters", which could one day carry out medical
> > tasks inside the body, have been built and test-driven by scientists.
> > The devices, no bigger than a virus particle, could eventually move around
> > the human body, ministering to its needs or dispensing drugs.
> >
> > The metal rotors of the tiny machines are powered by the body's natural fuel,
> > a chemical called ATP.
>
> According to the analysis in Robert Freitas' book Nanomedicine, rotors
> don't work well at the cellular scale. The fluid dynamics are wrong.
> Propellors rely on turbulence and vortices but it is hard to get that
> at the ultra-small scale.
I was under the impression that the rotors being used have very broad
chord blades, which replicate insect aerodynamics. At nanoscale, I would
imagine that any propulsion device using rotors or wings would have to
be able to work like the blades were tennis rackets, flying about in an
environment of high speed ping-pong balls. If the fluid is dense enough,
it should work.
In my terraforming paper I wrote, I came up with the concept of a large
buckeyball (C-360 or larger) molecule with no matter inside should be
bouyant in a 1 bar atmosphere, as a nano-balloon (my CO2 sequestering
nanites would have these on their bodies to float in the atmosphere
above the point where the atmosphere was too hot for the carbon to not
burn up).
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