Energy storage system for a hybrid power system

An electric circuit of an energy storage system, the electric circuit comprising:

• a propulsion power bus configured to provide a power signal from a main battery to an electric propulsion machine, the electric propulsion machine configured to power a propulsor for an aircraft, the electric propulsion machine further configured to be powered by a gas turbine engine;
• a non-critical bus configured to provide electric power to a hotel load on the aircraft;
• a critical bus configured to provide electric power supplied by the main battery to a critical load on the aircraft;
• and
• an engine starter bus configured to provide electricity supplied by the main battery to an electric starter, the electric starter configured to startup the gas turbine engine.

A method comprising:

• supplying electrical power from a battery to an electric propulsion machine of an aircraft via a propulsion power bus, wherein the electric propulsion machine provides propulsion for the aircraft and the electric propulsion machine is alternatively powered by a gas turbine engine;
• supplying electrical power from the battery to a hotel load on the aircraft via a non-critical bus;
• supplying electrical power from the battery to a critical load on the aircraft over a critical bus;
• and
• starting the gas turbine engine by providing electrical power from the battery to an electric starter via an engine starter bus, wherein the gas turbine engine powers the electric propulsion machine after the gas turbine engine is started.