[extropy-chat] FW: The Drake Equation and Spatial Proximity

[Eugen Leitl]

On Tue, Oct 24, 2006 at 03:08:39PM +0000, Robert Bradbury wrote:

>    We solved this problem during the debate about the dumb flyby probe
>    being sent to Pluto.

I don't remember that debate, but there are several ways to skin
a cat. A circumsolar cloud of gossamer PV platforms doubling as
a phased array pushing a gray sail has the advantage of being
low-tech, the self-rep thing being the only secret sauce
required. I don't know how many km^2 you'll need, but not a lot,
if we're accelerating a very small payload.

>    You have nested mass drivers (or nested guns) -- anything such that
>    something larger can launch something smaller which can launch
>    something smaller ...  Oriented such that each nested launching is in

Photon momentum is free, and 3 g for months is nothing to sneeze at.

>    the direction opposite to that of the direction of travel.  An

The nice thing about a phased array is that the reconfiguration is
all in timing, and hence realtime. You could push several probes with
one assembly, by aiming in space or in time.

>    alternate approach would be a relatively large ablative heat shield
>    targeted through the upper atmosphere of the star.  The problem gets

If we're talking about bootstrap, an antimatter-catalyzed fusion
drive for deceleration might work. It's a lot of mass, though.
I don't know whether sacrificial sails can be used for braking,
since I don't know how small a spot a phased array a lighthour
wide could focus over several lightyears.

>    much smaller when you remove weak human bodies from the equation and
>    only have to produce a few mg of nano-seeds as the final "package".

You need a seed pod which decelerates, maps the system and deploys
the seed in the right location. Whether this whole assembly, including
the sail is kg or a ton doesn't really matter that much.

>    It also true that because we will have *much* better observational
>    data regarding target systems that you could do things like targeted
>    landings -- things like flying into the tail of a comet in the target
>    system and using that material to help with the deceleration.

Comets have almost no mass, braking via stellar atmospheres might be
an option, but not at relativistic speeds.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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