# Re: My new site

Eliezer Yudkowsky (sentience@pobox.com)
Thu, 28 Nov 1996 10:19:16 -0600

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.

Oh, well.
Eliezer Yudkowsky.

```--
sentience@pobox.com      Eliezer S. Yudkowsky
http://tezcat.com/~eliezer/singularity.html
http://tezcat.com/~eliezer/algernon.html
Disclaimer:  Unless otherwise specified, I'm not telling you
everything I know.
```