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On 2015-09-22 05:58, Rafal Smigrodzki wrote:<br>
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cite="mid:CAAc1gFjRypwNb9bS8MOBOQ5Ey+O4JpR6Mm_CiNMH1=k-DAUgow@mail.gmail.com"
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<div class="gmail_quote">On Mon, Sep 21, 2015 at 8:23 AM,
Anders Sandberg <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:anders@aleph.se"
target="_blank">anders@aleph.se</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">My
calculations convinced me that there is simply no point in
sending flesh to the stars. AI/nano probes, rather thin
javellins and not superrelativistic, seems to be the way
to go. Colonizing around denser dust clouds rather than
trying to spam through them looks like a good strategy; in
many cases remote galaxies are easier to reach than stars
in the thin galactic disk.</blockquote>
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<div>### Absolutely, no flesh. But I have doubts about
nanoprobes - I am assuming you mean devices the size of
bacteria rather than beer cans. </div>
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Nope. More like beer cans, but typically rather long and narrow
(javellins). The nano is more about the building material. <br>
<br>
Nanoscale rockets don's seem to scale very nicely. Below a few mm
fission, fusion and antimatter become very tricky to contain and
use. <br>
<br>
In my scheme we used coilgun launch, and then a conventional rocket
to slow the payload. Eric's laser launch and seedship model likely
works even better. It is worth looking at magsail braking too:
interstellar magnetic fields and big conducting loops can be useful.
<br>
<br>
From relativistic speeds there is no difference between aerobraking
and lithobraking :-)<br>
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<div>There is a substantial premium to maximizing speed.
Even a 1% difference in speed translates into thousands of
years advantage in reaching targets at the other end of
the galaxy, and even more so when flying to other
galaxies. The first to arrive at a planetary system could
homestead and settle it with trillions of minds in a few
hundreds of years. Latecomers would be a minor footnote.</div>
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Yup. In our paper, we found that waiting a million years to launch
in order to get 1% closer to lightspeed was well worth it, since you
would get a lot more galaxies in the end. But it all depends on your
range and how crowded you think the universe is - and whether some
eager offshoot of your civilization may try to pre-empt your plans.
<br>
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<div>I would imagine that swarms of small but
non-microscopic probes would be launched at 2000+ g on a
single beam extended by lenses, and then coalesce into a
formation with sacrificial shielding components for the
long flight. Close to target the devices would reform to
build a laser, or ion engine, and use up 99.9% or more of
their mass to brake. The final colonizer swarm would be
tiny, possibly with bacteria-like digestor devices that
would transform matter into computational substrate for
the minds to be downloaded from distributed storage.</div>
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<br>
Sounds good. Multiple launches is a good way of getting redundancy.
In our sketch we assumed a 30g payload, but we think it is easy to
get down to the mg range. <br>
<br>
<br>
<pre class="moz-signature" cols="72">--
Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University</pre>
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