An efficient tip jet drive

A reexamination is conducted of the ideal propulsive efficiency of helicopter main rotor tipjet drives, in view of reduced tip-speed and lower jet exhaust velocity possibilities afforded by more advanced rotor designs than those contemplated in the 1950s. Relative to a hot jet-drive design, the most efficient system presently formulated inproves ideal propulsive efficiency by 62 percent, actual propulsive efficiency by 45 percent, and overall fuel efficiency by 19 percent. This vehicle, with reduced rotor speed and ibcreased rotor solidity, will result in a lighter, quieter vehicle than a turboshaft rotor-drive system, up to a gross vehicle weight of 36,400 lbs.