Windage losses are reduced by fitting the astern turbine in the lowest area available exhaust end of the astern casing. also by fitting hood over the last stage of astern and ahead blades also by fitting astern turbine in its own casing
It looks like in all the cases listed the "a-" comes from a shortening of the Old/Middle English "an" (on). Two other common uses of "a-" are to signify the preposition "of" or denotes the Latin "without".
A ketch is a sailboat with two sails, both fore (ahead) of the rudder. The smaller mizzen-mast (jigger) is astern of the mainmast.
The ship slowly moved astern as it pulled away from the dock.
The stern is the back end. Astern is 'toward' the stern.
The term is "astern" as opposed to "ahead" (forward) It comes from the word stern, that means the rear of the boat, as opposite to the bow The nautical term for rearward, as in the direction, would be aft.
Pitcher Valerie has written: 'Anya astern, come down from the sky' -- subject(s): Accessible book
abaft. astern.
Astern.
Going backwards.
aft
Aft or astern