what is the steampressure requird to move a locomotive & attain 200 miles a hour?

Question

first to slowly move itself
next to move 24 coach formation @ 200 miles per hour.

Answer 1

No steam locomotive has ever done 200mph and I do not think it would be possible: the physics would simply not allow it.

Steam locomotives built for express passenger use generally have a top speed of around 100mph, under heavy load (24 coaches were not unheard of in the heyday of steam but the usual load would be 10-15 coaches).

The fastest ever steam locomotive is the British class A4 pacific 'Mallard', which reached a top speed of 126mph, still the record for a steam locomotive. It has a boiler pressure of 250 pounds per square inch (p.s.i.) which is the maximum for a conventional steam locomotive. Experiments were carried out in the 1930's with boiler pressures higher than this (around 300 p.s.i.) but they did not work.

To travel at top speed the boiler pressure of 250 p.s.i. would have to be sustained over a long period, which would involve expert work by both driver and fireman.

At slower speeds and running light (i.e. without a train) the boiler pressure could be lower.

Answer 2

No steam locomotive has ever travelled faster than 126 mph.