Leading enginemaker Rolls-Royce is pursuing its own hydrogen engine designs and recently patented a fuel system for a gas turbine engine configured to combust hydrogen fuel. This novel approach to hydrogen power could help solve one of the major problems of using liquid hydrogen as a fuel source, namely its extremely cold temperature. Rolls-Royce's idea is to use a fuel turbine to heat the hydrogen fuel before it reaches the engine, creating a more stable combustion process.