Re: Europa energy fluxes

[Robert J. Bradbury]

On 3 Mar 2003, Joe Latrell wrote:

> Could someone please elaborate on what they mean by nanotech in these
> discussions?

Nanotech as currently defined by the National Science Foundation
and the National Nanotechnology Initiative is the ability to manufacture
things on the 10-100 nm scale.  This is a bit different from the definitions
that Feynman created 40 years ago [1] and Drexler expanded on 20 years ago [2].
Feynman got it wrong (in that he projected at least one motor that was
too large, put some money on the table challenging someone to create it
and lost the bet).  Perhaps one of the few mistakes Feynman *ever* made.
Drexler however got it right.

Nanotech as currently practiced involves two levels -- the microelectronics
people pushing things down towards 100nm and lower and the chemists
building up from the level of < 10 nm.

Where things get really interesting is in the middle.  A ribosome is
about 30nm.  Drexler's diamondoid nanoassembler arm has dimensions of
something like 30x100nm.  So those are the size scales you have to
talk about if you want to "assemble" something (an enzyme, etc.).

The term "robust molecular nanotechnology" is generally used to include
"nanorobots".  Nanorobots are bacteria sized machines (~1 micron (1000 nm)
in size).  They are collections/assemblies of "nanocomponents" just like
natural bacteria are.


> If you just mean miniaturization, then fine, lets use it as such.

When I use terms like "nanotech", I generally mean things along the
lines above.  Now, obviously the entire microelectronics trend
and MEMS and microfluidics trends (much more recent but on similar paths)
are driving what one could call general purpose miniaturization.

So while a Europa probe with an on-board "lab", if designed today,
would have to depend on microelectronics/MEMS/microfluidics (multi-microns
in size), one designed in a decade or more might be able to use developing
"nanotechnology" capabilities.

It isn't clear to me exactly how small you could make a probe.
But its a *lot* smaller than the probes we have been sending out
to date.

> If the definition includes nanobots and the like, I really
> think we need to start looking at a really LONG time before we can send
> packages like that anywhere.

This is the problem -- people do not realize that "biotech" *is*
"nanotech".  Want to engineer a bacteria to emit light that can be
registered by a photodetector on the absorption of a specific
molecule?  This is almost off-the-shelf technology *today*
(depends to some extent on the molecule you want to detect).
Want to engineer a bacteria that can tolerate a megarad+
of radiation for long voyages through space?  We already
have the complete genome sequence of Deinococcus radiodurans
which can pull off this trick.

One needs to expand our thinking so that we understand
"biobots" are not so different from nanorobots.

> Just to let you know where I am coming from, complete nanobots to me are
> measured as under 1/10th of an inch in size (l x w x h).

No, this is *much* too large.  This would be a "microrobot"
(or even collections of them).

Hope this helps somewhat.

Robert

1. Feynman, R. P., "There's Plenty of Room at the Bottom" (1959)
   http://www.zyvex.com/nanotech/feynman.html
2. Drexler, K. E., "Molecular engineering: An approach to the
   development of general capabilities for molecular manipulation",
   PNAS (U.S.A.) 78:5275-5278 (1981).
   http://www.imm.org/PNAS.html


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