Keith:

First of all there is no trajectory to a torpedo..........

It is a self-propelled weapon (automobile torpedo) that maintains a preset depth and a gyro-controlled course to the target.

Inside the U.S. Navy's MK 13 (aerial) MK 14 (submarine) and MK15 (surface craft) torpedoes, there is a gear train (main engine)
made up of a spindle casing with an upper, middle, and lower
bearing. These brearings have an inner and outer race. The steel
balls for each bearing are hand-placed (individually) into these machined races, and tightened to exact clearances. The inner and outer counter-rotating shafts use floating grooved bronze
bushings at the crosshead, as do the inner and outer propellor shafts in the tail section.

You can get an idea of what I'm talking about by going to:

[www.eugeneleeslover.com]
[www.eugeneleeslover.com]

All three aforementioned torpedoes use a similar gear train, bearings, bronze bushings and sleeves.

Hope this helps,

ROBERT M.