I actually tried to build a physical model, but my limited ability with
metalwork (a teenager with hand tools) kept me from making one which
would actually turn. Years later I realised that all that would really
happen is that the device would jiggle a bit around the center of the
circle described by the shaft's center of mass, with no net momentum
transfer outside of the system....
O---------------------------------O
| Hara Ra <harara@shamanics.com> |
| Box 8334 Santa Cruz, CA 95061 |
O---------------------------------O
Eliezer Yudkowsky wrote:
>
> Okay, I've taken a look at the Lorrey drive, and I've found what appears
> to be a gaping mechanical flaw.
>
> > Imagine a centrifugal drum, like that seen edge on in the animation
> > below. If you had several masses in the drum, rotating around the
> > geometric center, they would all produce equal centrifugal force at
> > every point in their orbits, so you would essentially have the
> > workings of a gyroscope. However, if you were able to speed each
> > mass up at one point in the orbit, and slow it down again on the
> > opposite side of the centrifuge, you would have a point in the
> > centrifuge where all masses were going slowly on that side, and
> > fast on the opposite side. This would produce excess centrifugal
> > force in a direction straight out from the point of highest velocity.
> > you would also impose a large amount of torque on the drum and
> > chassis of the device.
>
> Positions | Velocities | Accelerations
> _______ | _______ | _______
> / A \ | / A-> \ | / >A \
> / B \ | / ^ B \ | / <<<<B \
> \ D / | \ D V / | \ D>> /
> \ C / | \ <-C / | \ >C /
> ^^^^^^^ | ^^^^^^^ | ^^^^^^^
>
> Take a mass M, weighing one gram. M goes around in the centrifuge
> shown. At D, M travels at 5 meters/second, at B, 10 meters/second. At
> A, M is pushed forward by an extra 5 m/s and at C, M is slowed by 5 m/s.
>
> The total system, including the centrifuge, works like this. Start at A
> before M is accelerated, assuming the whole device to have zero
> momentum. At A, M is pushed forward by 5 m/s. This transfers
> -5gm/s of momentum to the centrifuge. M goes around the centrifuge
> through B, coming out at C going -10 m/s instead of 10, transferring 20
> gm/s of momentum to the centrifuge. M is then slowed down at C,
> transferring another -5gm/s to the centrifuge. M then goes from C to A
> through D, going from -5m/s to 5m/s, transferring -10gm/s of momentum to
> the centrifuge.
>
> Net change in momentum: -5 + 20 + -5 + -10 = *0*.
>
> It does not work. It will not go. Sorry, Mike.
>
> Trust me, I know how you feel - I, too, had a cherished Great Idea, but
> luckily found the flaw *before* it was published.