The World could be a different place concerning aircraft propulsion, if German scientists and engineers had choose a different way to use turbine power than a pure jet gas turbine.
During the 30's, several Countries (USSR, Germany, U.K, U.S.A., Sweden, France, Italy and Japan) had technical people working on some kind of steam turbine applied to aviation. In those days, if they had been asked, they had answered that, in the future, long transatlantic flights could be performed with some special steam engine instead of the Diesels or petrol engines of the then current flying boats.
I designed this conceptual aircraft based on steam turbine power; the steam is generated in special, very high temperature boilers placed in the two rear nacelles, one upper and the other under the main wing / fuselage.
These boilers burn sequentially solid thermite bars, and must be regeneratively cooled by water that instantly boils into high temperature steam. Rear facing openings are for releasing the entire boiler in an emergency situation.
Contrail is formed by the steam turbine exhaust, and the propellers are moved by the turbine through a reduction gear.