[Turing_Machine]

> Also I never understood why steam engines release all the hot stream into the air?

They don't. All practical steam engines have condensers that recover most of the water and as much of the heat as current technology and the laws of thermodynamics allow.

[m4rtink]

In steam trains it is often injected to the chimney to increase draft, forcing more air through the firebox, improving combustion. This of course uses up a massive amount of water.

For this reason most steam engines in ships and elsewhere generally did have condensers & reused the steam as feedwater, as you describe.

[cryptica]

I was thinking that if the steam had to travel up 10km to the surface, that would give it more time to cool down. Maybe in cold countries, they could use outside air temperature to cool rising steam before it reaches the top of the hole.