Re: Lasers and Scoops

[Brian Mansur <bmansur@oc.edu>]

Brian Here.

In addition to my other questions, this one about our ionizing laser for a 
ramscoop is troubling.  How much power will it take to effectively cover an 
area of space, perpendicular to the direction of the ship, with a laser 
blanket beam that is strong enough to ionize iron?  If the numbers are too 
obscene for sensitive readers, how about for hydrogen?

By the way, I already know that shining your beams ahead of the ship like a 
flashlight won't work.  I though that we could run the lasers through some 
mirror aparatus.  Those mirrors would diverge and reflect the beam to shine 
radially from the ship's bow in all directions perpendicular to the ship's 
direction.  It would be like an ionizing blanket.

Aren't there more efficient ways to ionize something besides use of lasers. 
 I hear they are only 10% efficient.  Isn't that the same deal with masers?

Brainstorming

I just thought up of a way to make a wire mesh scoop (roughly 200 tons in 
overall weight as depicted in the Explorer design) and not have it collapse 
under 1g accel.  We could put a advance ion rocket, a small one perhaps 1 km 
long, in the center ahead of the open end of the scoop's cone.  It would be 
tethered to the ends of the wire mesh and accelerate at the same rate as the 
main engine of the Asimov.  Thus, it could act like a tug to keep the cone 
from collapsing from the g force.  Big problem: how to fuel it and give it 
enough RM without running into the same mass ratio problems we've had from 
the beginning.

Another idea that I have for this is to replace the tug with a mirror 
aparatus that is supported by  the photonic pressure from the ionizing laser 
beams.  The mirror would have to be angled so that the beams could be 
reflected into the aparatus.  My concern is whether or not we can generate 
the power to do this and still ionize some gas.  Maybe with power from a 
maser.  Tim, I think, suggested that we use a maser beam directly from Sol 
to ionize the fuel.

Another idea.  Build a REALLY tall tower to support the mesh cables.  I hate 
this idea because it will be very flimsy and add quite a bit of weight.

I toyed with the idea of rigging the scoop like a parachute.  The ions would 
be gathered into a catchbox at the bottom.  When it filled up, the box could 
be haulded up a 2000 km long cable to the fuel tanks.  Unfortunately, this 
idea creates more problems that it seems to solve.  True that, since the 
scoop is tethered to the ion drive up ahead, the scoop won't collapse. 
 Unfortunately, the drag is attrocious.  Also, the ion drive couldn't run 
half the time because the catchbox would be in the way.  And what happens if 
the cable breaks?  Urgh.