The Turbo Rocket Jet Cycle – A 68:1 Thrust-To-Weight Combined Cycle Air-Breathing Propulsion System Using Storable Propellants

A new rocket-augmented afterburning turbofan propulsion system is introduced that achieves peak thermal efficiency at 30% of maximum thrust and a 65:1 thrust to weight ratio for aircraft use cases. The ability to segregate operational regimes into high thrust/high specific consumption and low thrust/low specific fuel consumption increases aircraft design flexibility, including use cases like vertical take-off/landing and fast climb to efficient cruise. Prior work has described single stage to orbit rocket combined cycle systems using cryogenic propellants, but application to aircraft use cases requires propellants compatible with existing ground infrastructure – namely Jet-A fuel and Hydrogen Peroxide oxidizer. These propellants are classified as storable, meaning they require no special handling and remain stable through a broad range of environmental conditions, primarily ambient temperature and pressure. The turbofan is arranged with LP/HP compressors and HP turbines on one spool, and the thrust fan on a second in-line spool driven by LP turbines. When higher thrust is required a rocket combustor powers a second LP turbine whose exhaust exits through trailing edge nozzles in the fan stator. The fuel-rich rocket exhaust ignites aft of the fan, creating afterburning thrust in addition to rocket thrust. A notional 508mm diameter, 4.9:1 bypass ratio thrust fan example is described with 14kN of turbofan thrust, 4.3kN of rocket thrust and 53kN of total rocket-augmented afterburning thrust at 81kg installed mass.