Re: Cheap Shots,

From: Michael S. Lorrey (
Date: Tue Jun 13 2000 - 05:51:01 MDT

Damien Broderick wrote:
> At 05:21 PM 12/06/00 -0400, Mike wrote:
> >I would stipulate that at sub-relativistic speeds it violates commonly
> accepted
> >principles of conservation of momentum. For anything else, I personally would
> >take the word of Prof. Cramer over most anyone on this list.
> Yes, but since you're not telling us enough to judge what's being said by
> Cramer, this is perilously close to argument from authority.
> The rough sense I get of the process can be modeled like this (forgive me
> if I'm way wrong):
> You have a one-tonne ingot of steel down the back of the starship in
> freefall, aimed up an electromagnetic launcher. You turn on your power
> source and the coils click into brief action one after another, dragging
> the ingot ever faster toward the prow.
> When it gets to the nose of the ship, the lump is moving at 0.9999 c, say,
> and masses 2.2 million megatonnes. It hits the plate at the end of the ship
> and recoils, shoving the ship the hell forward (but the ship has meanwhile
> been flying backward, hasn't it, impelled by this internal mass driver
> effect?), and as it recoils down the launcher its energy and momentum are
> sucked back into the ship, pushing it the other way, balancing the books.
> Except that by the time it's slowed completely and reached the aft storage
> container, it's back to massing a single tonne. So the books are *not*
> balanced, there's been a net impulse forward when the ingot was *really
> really heavy*, its m having been pumped up by all that injected e from the
> batteries.
> This doesn't make a *hell* of a lot of sense to me, but is that something
> like your story?
> (Bearing in mind that there's no striker plate, because your asymmetrical
> mass is actually rotating, all working parts being made from some
> supernatural material, and that it isn't zillions of klicks long, and all
> that pesky detail stuff...)

Essentially correct. Frankly I was ready to give up on the whole thing
until I heard this from Cramer, and I'm still not sure I understand
totally why he thinks it would work in those conditions. And you are
right, under normal conditions you'd need some hellaciously cool
materials to keep the centrifuge together under those relativistic
velocities. The two possibilities that intrigue me though are a) using
photons or other subatomic particles as the working 'mass' within the
centrifuge, and b) usinge fluids that have a very very low internal
speed of light.

With possibility (a), as opposed to using the laser/maser/particle beam
as a linear reaction device (i.e. throwing away that energy/mass), you'd
be recycling some of it, and with possibility (b) if the effect only
depends upon the speed of light for particles within the working media,
then you can use much lower velocities to attain this relativistic
effect. As I recall we now have materials that have an internal speed of
light of 30 meters per second or so. If these can be used in fluid form,
in the centrifuge, can you move these through the device at or near 30
meters per second to get this effect? I don't know, but I'm interested
enough to want to test it. People that sit on their armchairs making up
excuses why something is impossible don't interest me. If I prove it
doesn't work by experiment, then oh well, it was a nice idea.

As for those that compare my designs to a Dean drive, I can say that
there are significant design flaws in the Dean drive.

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