If you're using a real steam engine, with pistons and beams and things rather than these new-fangled turbines, I don't believe you could get it up to pressure from cold in a couple of hours; something would crack. Eight hours would be more like it. So a military ship on active service (like a steam train on a regular schedule) would probably never be allowed to cool down completely. You could always use the steam to run a bilge pump, or make tea.
You wouldn't want too much steam in your smoke; as far as possible, at least on modernish steam power plants, you'd be condensing it so you didn't waste water. Yes, I know you're surrounded by the stuff as far as the eye can't see (because of all that smoke) but you're not going to put sea water into your boilers unless you're really desperate. So, along with the coal (or firewood or compressed straw or egyptian mummies) to burn you have to carry fresh water.
And a big ship in water goes an enormous distance before slowing to a halt, what with all that weight and fluid friction. Turning it sidewazs on would probably be faster than reversing the screw (if you've got enough searoom) and they take slightly more than forever turning (and stopping turning when they've got turned). Propellers just start to cavitate and their efficiency drops off drastically outside their designed range, so just reversing the spin (ignoring the reduction in time between replacements of engine parts) is not very effective.
Parachute braking (the sea achor technique) invoves an incredibly strong winch system attached to a bit of chassis which is really well attached to the ship's basic structure; there are lots and lots of tonnes of force involved. Still, this is at a fairly easy to replace point on the ship, relative to the main gears or the propeller shaft.
You wouldn't want too much steam in your smoke; as far as possible, at least on modernish steam power plants, you'd be condensing it so you didn't waste water. Yes, I know you're surrounded by the stuff as far as the eye can't see (because of all that smoke) but you're not going to put sea water into your boilers unless you're really desperate. So, along with the coal (or firewood or compressed straw or egyptian mummies) to burn you have to carry fresh water.
And a big ship in water goes an enormous distance before slowing to a halt, what with all that weight and fluid friction. Turning it sidewazs on would probably be faster than reversing the screw (if you've got enough searoom) and they take slightly more than forever turning (and stopping turning when they've got turned). Propellers just start to cavitate and their efficiency drops off drastically outside their designed range, so just reversing the spin (ignoring the reduction in time between replacements of engine parts) is not very effective.
Parachute braking (the sea achor technique) invoves an incredibly strong winch system attached to a bit of chassis which is really well attached to the ship's basic structure; there are lots and lots of tonnes of force involved. Still, this is at a fairly easy to replace point on the ship, relative to the main gears or the propeller shaft.
From 12 knots ahead stopping and reversing engines.
