Suspect a small gas turbine could be used to drive a generator in a system similar to Honda iMev. They are generally most efficient at @ 85-95% max rpm. As an engine to provide thrust could be deemed a tad antisocial as EGT – exhaust gas temp – usually exceeds 500 deg C. On a GE 90 powered 777 out of mile high Denver once saw 1050 deg C. On take off.