Actually, way back in 1980 or 1981, one of the science magazines had a cover with silent propellers for big passenger jets. The propellers were pushers, at the rear of the wing engines. They had kinda twisted blades (like drill bits, sorta) that fanned out behind the main part of the propeller itself. They produced as much thrust as jet engines, even though they only turned at 900 rpm.
I haven't been able to find the magazine that had a jet on its cover, with the propellers on the trailing part of the wing. But look here for a bunch of kinda humorous pictures of science mag covers of the past -
https://duckduckgo.com/?q=science+and+mechanics+magazine+1981&iax=images&ia=images.
"Quiet" Thrusters For 'Flying Cars' Comes Out Of Stealth Development
https://www.zerohedge.com/technology/quiet-thrusters-flying-cars-comes-out-stealth-developmentThe new eVTOL has thruster technology developed by the National Aeronautics and Space Administration via a multi-million dollar grant from Defense Advanced Research Projects Agency.
Applied eVTOL Concepts revealed the "Epiphany Transporter" last week, described as a "new mode of personal mobility."
The company released specs on the new aircraft, indicating it's capable of 160 mph with a 300-plus mile range but generates less than 55 decibels of noise at 50 feet.
"The Epiphany Transporter can accommodate two people, their luggage, plus golf clubs! Intended to be simple and safe to operate, and about the size of a Tesla Model 'S' automobile, it fits into a standard one-car garage with its thrusters folded up, Applied eVTOL Concepts said.
...
