otnmbrd wrote:

Interesting .... thanks. I would have thought, considering the mass
involved that you would have had to reduce "ahead" steam first, prior to
"pulling one lever".

Recip engines have to stop before reversing simply because they rotate
in the opposite direction, so do steam turbines. In either case "ahead"
steam is secured since it is pointless and counterproductive to have
steam working on both "sides" of the engine. In the case of a recip, it
is mechanically impossible due to the valve gear geometry.

Admitting steam in the astern direction on a recip changes the side of
the piston which sees greater pressure, this first slows then stops
piston travel ... the forces are the same, the only thing that changes
is the direction of crankshaft rotation.

The turbine is locked to the reduction gear and shaft so it has to stop
before rotation can occur in the opposite direction. There is no problem
admitting steam to the astern turbine while the engine is rotating in
the ahead direction, we do it quite regularly to assist in slowing the
engine rapidly during maneuvering.

Rick