US Patent 11014677 Reverse bootstrap air cycle machine

Disclosed is a cooling circuit for cooling a heat load in an aircraft system, having: a compressor; a turbine connected to the compressor by a shaft, the turbine configured to drive the compressor via the shaft when RAM air pressure into a turbine inlet is above a first threshold; and a motor connected to the shaft configured to drive the compressor when RAM air pressure at the turbine inlet is below the first threshold to cause the compressor to draw air into the turbine inlet, through the turbine, a heat exchanger in fluid communication with the heat load, the compressor, and out of a compressor outlet.