The first of these was started by Junkers Moteren (Jumo) in 1940. The turbine ran on the test bench in 1941, but the project was shelved in 1942 in favour of gas turbines.
The specs for the Jumo turbine were:
Power - 3000hp
Turbine speed: 8000rpm
Propellor Speed: 950rpm
Weight: 800kg (I presume this only applies to the turbine itself and the reduction gearing, not the boiler and other required equipment).
Intake Pressure: 100atm
Intake Temperature: 550°C
Exhaust Pressure: 0.15atm
A further steam turbine design was also being undertaken by Professor Lösel and Dipl-Ing Pauker at the Technische Hochschule. This was to be rated at 4000hp. Not much in the details for this turbine, except that the turbone would be roughly 1/2 the length and 2/3 the height of the Jumo 213 aero engine (ie about 1225mm long x 565mm high). It was also cancelled in 1942.
Steam turbines re-emerged in 1944 when Messerschmitt were looking for suitable engines for their long range Me264 "Amerika bomber". The first prototype Me264 flew with 4 x 1250hp Jumo 211s, taken straight from the Junkers Ju88, and the second prototype used 4 x 1750hp BMW 801 radials. Both were considered underpowered. The original concept called for 1750hp Daimler-Benz DB603s, but these were in short supply.
Various alternatives, including mixing piston engines and jet engines, turboprops and turboprop and jet combinations were investigated. Steam turbines were also investigated, with Professor Lösel's Osermaschinen company being asked to design and manufacture a suitable steam turbine.
The specificatiosn for the engine were:
Turbine speed: 6000rpm
Propellor RPM: either 400-500rpm using a 5.3m diameter prop or 6000rpm using a 2m diameter prop.
Power to weight: 0.7kg/hp = 4200kg (I presume this is for the complete installation).
Specific Fuel Consumption: 190g/hp/hr = 0.42lb/hp/hr
Due to the shortages of aviation fuels in Germany in late 1944 it was thought that the steam turbine could use a 65% pulverised coal/35% petrol fuel mix until sufficient quantities of petrol were available. Many of the components had been manufactured prior to VE day, but the turbine had not run.
The advantages of the steam turbine (compared to piston engines) were thought to be:
Constant power at all altitudes.
Capacity for 100% overloading, even for extended periods.
Full steam output achieved in 5-10s.
Not sensative to low temperatures.
Long life and simple servicing requirements.
Simple and quick control.
The expected life of the steam turbine was between 4000 and 6000 hours between overhauls, as compared with less than 500 for most high powered piston engines - Merlins were less than 300 for some versions.
I would presume that the rated powers of these turbines were for continuous use. The Jumo 213 was rated at 1750hp at takeoff and at rated altitude, but this was a 3-5 minute rating. Continuous rating was less. The Jumo 213 weighed 940kg dry, not including radiator and oil cooler.
The similar Daimler-Benz DB603 was also rated to 1750hp, and 920kg dry. It's maximum continuous power was 1500hp (from Wiki: DB603. Two DB603s, therefore, should be able to produce the same continuous power as the Jumo steam turbine (ie 3000hp) for 1840kg (without coolers). If the power to weight of 0.7kg/hp was achieved for the Jumo turbine it would weight approximately 2100kg.
One of the obvious disadvantages to using a steam turbine in a combat aircraft is its susceptibility to battle damage - particularly the condenser and boilers.
How big would the condenser have to be for the 3000hp unit? Would it be much larger than for a piston engine(s) with 3000hp continuous power, whose coolant would be at about 120°C?
The 100% overloading would mean a normal 3000hp unit would produce 6000hp? What would limit the time for its use? How would this be achieved - extra steam mass flow/consumption?
The first US gas turbine/jet project, the Lockheed L1000/J37 also began from a steam turbine project Wiki: Lockheed J37.
In 1930 Nathan C. Price joined Doble Steam Motors, a manufacturer of steam engines for cars and other uses. Over the next few years he worked on a number of projects and starting in autumn 1933 began working on a steam turbine for aircraft use. The engine featured a centrifugal compressor that fed air to a combustion chamber, which in turn fed steam into a turbine before exiting through a nozzle, powering the compressor and a propeller. The engine was fitted to a test aircraft in early 1934, where it demonstrated performance on par with existing piston engines but maintaining power to higher altitudes due to the compressor. Work on the design ended in 1936 after Doble found little interest in the design from aircraft manufacturers or the Army.
The Besler brothers demonstrated a steam powered aircraft in 1933.
Besler steam plane
But this used a 2 cylinder piston engine rather than a turbine.