[ExI] No mirrors, was Deceleration mirrors

Anders Sandberg anders at aleph.se
Tue Sep 22 09:41:40 UTC 2015

On 2015-09-22 05:58, Rafal Smigrodzki wrote:
> On Mon, Sep 21, 2015 at 8:23 AM, Anders Sandberg <anders at aleph.se 
> <mailto:anders at aleph.se>> wrote:
>     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.
> ### Absolutely, no flesh. But I have doubts about nanoprobes - I am 
> assuming you mean devices the size of bacteria rather than beer cans.

Nope. More like beer cans, but typically rather long and narrow 
(javellins). The nano is more about the building material.

Nanoscale rockets don's seem to scale very nicely. Below a few mm 
fission, fusion and antimatter become very tricky to contain and use.

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.

 From relativistic speeds there is no difference between aerobraking and 
lithobraking :-)

> 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.

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.

> 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.

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.

Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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