Environmental control system utilizing shoestring cycle to maximize efficiency

An environmental control system of an aircraft that utilizes recirculation air, comprising:

• an inlet configured to supply bleed air at a first energy from a source to the environmental control system,
• wherein the environmental control system supplies the bleed air at a second energy to a chamber;
• and
• an air cycle machine comprising a compressor and a turbine,
• wherein the air cycle machine receives the recirculation air from the chamber,
• wherein the recirculation air is bleed air at a third energy flowing from the chamber to the air cycle machine,
• wherein, during a ground operation of the aircraft, the bleed air drives the air cycle machine and the compressor receives the recirculation air flowing from the chamber to the air cycle machine, and
• wherein, during a flight operation of the aircraft, a first portion of the recirculation air drives the air cycle machine and the compressor receives a second portion of the recirculation air,
• wherein the first portion of the recirculation air expands across the turbine to drive the air cycle machine,
• wherein the second portion of the recirculation air received by the compressor is compressed based on the first portion of the recirculation expanding across the turbine to produce compressed recirculation air, and
• wherein the environmental control system passes the compressed recirculation air back to the chamber,
• wherein the environmental control system passes the first portion of the recirculation air to an outlet after the first portion of the recirculation air expands across the turbine,
• wherein the environmental control system passes the compressed recirculation air from the compressor to a second heat exchanger, from the second heat exchanger to a second turbine of the air cycle machine, and from the second turbine back to the chamber.