[ExI] Physical limits of electromagnetic launchers

[Keith Henson]

On Fri, Jun 1, 2012 at 5:00 AM,  Anders Sandberg <anders at aleph.se> wrote:

> What are the physical limits to launching long-range relativistic
> payloads with electromagnetic launchers?
>
> Let us ignore the energy and material access constraints, we have a
> Dyson sphere and fairly mature nanotechnology. Obviously there is going
> to be some limit on acceleration tolerance of the payload, so based on
> that one can make longer launch tubes for slower acceleration.

v = at.  for v =1/10th c, 30,000,000m/s for a =~10g, 100 m/s^2, t
=300,000 seconds or about 3.5 days of acceleration.

s =1/2, at^2, 4,500,000,000 km, 15,000 light-seconds, 250 light
minutes or 30 times the distance from the sun to the earth.  Keeping
it straight is going to be an interesting problem.

if the tube mass was a t/m, the mass would be 4.5 x 10^15 kg.  The
asteroid 1986 DA is 2×10^13 kg so it would take ~225 of them.

And you don't even want to think about the power this takes for
constant acceleration near the end.

If you need to get physical objects between stars, light sails and
using the stars to power propulsion lasers seems to be a better idea.
(Forward's idea.)

Keith