A propulsion system includes at least two propulsors. The at least two propulsors each comprising a fan having a plurality of fan blades. A controller includes memory and one or more processors. The memory stores instructions that when executed by the one or more processors cause the system to perform the following: determine a pairwise phase difference between one propulsor of the at least two propulsors and another propulsor of the at least two propulsors; generate a reference phase angle; determine a target phase shift for each propulsor of the at least two propulsors; and adjust a speed of each propulsor of the at least two propulsors based on the target phase shift until the pairwise phase difference is equal to the reference phase angle.

A fuel system for a gas turbine engine configured to combust hydrogen fuel. The fuel system includes a main fuel conduit, a fuel pump configured to operate on hydrogen within fuel conduit to provide pressurised fuel to core combustor of gas turbine engine, an auxiliary combustor downstream in fuel flow of fuel pump, and configured to combust a portion of fuel diverted from main fuel conduit and to heat remainder of fuel in main fuel conduit, and a fuel turbine downstream in fuel flow of the auxiliary combustor. The fuel turbine is configured to be driven by heated fuel from auxiliary combustor and configured to power the fuel pump. The fuel system comprises a turbine inlet valve provided upstream in hydrogen fuel flow of the fuel turbine and configured to control mass flow rate and/or pressure of fuel flowing into fuel turbine. 1. A method of operation is also described.

The present disclosure relates to gas recovery systems and methods, and systems including gas recovery systems. In some embodiments, a gas recovery system includes a gas inlet, a compressor, a buffer tank, a variable speed microturbine, one or more sensors, and a control system. A gas input into the gas inlet can be output from a processing tool, and the gas can include hydrogen or ammonia gas. The gas can be used to produce electrical power using the first variable speed microturbine. The sensor, for example, a gas analyzer, a flow meter, or a pressure sensor, can be between the gas inlet and the variable speed microturbine. The control system can be configured to control a speed of the variable speed microturbine in response to a measurement from the sensor.