GAS TURBINE ENGINES HAVING CRYOGENIC FUEL SYSTEMS

Turbine engine systems (200; 300; 400) and aircraft having such systems are described. The turbine engine systems (200; 300; 400) include a combustor (210; 306) arranged along a core flow path of the turbine engine (200; 300; 400), a drive shaft (220; 312) having at least a compressor section (206, 208; 304) and a turbine section (212, 214; 308) coupled thereto, a cryogenic fuel tank (224; 318; 404) configured to supply a fuel to the combustor (210; 306), and an expansion turbine (234; 326; 412) mechanically coupled to the drive shaft (220; 312), the expansion turbine (234; 326; 412) configured to receive fuel from the cryogenic fuel tank (224; 318; 404) and expand said fuel, wherein expansion of said fuel by the expansion turbine (234; 326; 412) drives rotation of the expansion turbine (234; 326; 412) to provide power input to the drive shaft (220; 312).