Hi Adam,

Yes, we actually DID consider solar sails and the like, but then decided that for
a Nature paper we did not want to lob a large engineering target at reviewers.
That is, energy can't be argued (except of course as to why you'd use energy
as a metric in the first place :) ).

So we tried to be as simplistic as possible and stick only to the physics where
possible. Hence clumsy things like the big rock shielding -- thought
it's kind of grown on me since :)

But being able to exploit local energy and do some sort of sailing only
makes things better (from the perspective of matter transport) as you
point out. And I'm sure there are a variety of clever methods using the
target star for deceleration too. But again, the reviewers would have
attacked that from all sorts of angles.

For instance, I was at one
point analyziing "smart particles" which could change their reflectivity
and slow themselves down near a star (from c/100 or c/1000). And
I'd have pursued it more vigorously if I had a nice information theoretic
answer to the message corruption (cosmic rays) problem. That is,
you might be able to engineer particles which could slow themselves down enough to
enter a target star solar orbit, but the transit times would be long and
the "smallish" particles could be readily corrupted. I also liked the idea
that perhaps one could use VERY small particle hoards and using
something like a linear accelerator to push them up to pretty useful
speeds without all the rocketry overhead (a launcher of sorts). I say hoards
since I'd figure there's a need for navigation and perhaps a hoard
could collectively navigate even with "stupid" constituents.

But now I'm talking science fiction, really :)

Nonetheless, we are thinking about various ways to get "stuff" from here
to there and either park it or "deliver" it (as in the case of bio material).
Along the latter tack -- there was a recent paper that considered what
happens to bacteria embedded in clay/ceramic when it's smashed
into something at high speed. The authors claim that the
bacteria survive in amounts that could colonize. So "gentle"
delivery may not be so terribly important :) Of course, I doubt
even bacteria could survive a c/1000 to zero impact well -- not
to mention the target!!!! :)

This matter delivery stuff could be rather antisocial :)

I've got to get on the road (reunion at alma mater) but as a parting
shot, I really am interested in exploring various methods of intersteller
FedExing. I'm also increasingly interested in the biological history
of our planet among other things. Right now I'm at sea in
both areas -- but hope to learn fast :)

So, any and all serious (and not so serious :) ) suggestions are welcome.
I may be incapable of putting it in a tight technical framework (owing to
ignorance), but this area seems open enough that a skunk works mentality
seems reasonable :)

And once again, my particular bias is "colonization" though one
has to be open to the possibility of "civilization survival" messages
(as opposed to biological ones). I've never really understood
the "hi I'm here" motive, but I do know we as a species have an
irrepressible urge to do so anyway (even if it's just an Ozymandias
moment :) ) -- so why not others

Cheers,

Chris

PS: I've got a web site up which has some collateral info which might
be of interest. http://www.winlab.rutgers.edu/~crose/cgi-bin/cosmic.html .
I think you already have it, but it's changed a little since 9/2/04 . As more
info/analysis pops up/occurs, I'll be posting it. But don't hold your breath :)