All Quiet on the Start-Up Front

Founded by former NASA engineer and Uber Elevate co-founder Mark Moore, Crossville, Tennessee-based Whisper Aero claims its ducted fan propulsion system—which comprises a large number of rotor-blades turning at a relatively low rotational-rate—is wholly inaudible from distances of greater than sixty-meters.

Mr. Moore described his company’s propulsion architecture and business plan in three papers presented at 2023’s American Institute of Aeronautics and Astronautics Aviation Forum.

“The Whisper ducted fan has been optimized for lowest noise and highest efficiency,” Moore wrote in one of the papers, “unlocking low-cost regional air mobility through Whisper Aero-Propulsive Coupling.”

Moore continued: “The high efficiency is achieved with a very high blade-count fan. The blades are tensioned to an outer shroud, similar to the spokes of a bicycle wheel, for sustained rigidity throughout operation.”

Another Whisper paper described the manner in which the company’s propulsion technology could be installed on aircraft, thereby providing, theoretically, regional air-service over trips ranging from fifty to five-hundred-miles. Notwithstanding the inconvenient fact they’ve yet to build such a contraption, Moore and his boffins posit integrating Whisper Aero’s so-called propulsors into the leading-edges of airplanes’ wings would serve to maximize aerodynamic efficiency and thrust. Whisper Aero has, however, run various tests on its ducted fans, including flight-testing of a drone powered by a single iteration of such a ducted fan.

Moore, who asserts the number of blades within his company’s ducted fan system is proprietary, has conceded “Our blades are just like spokes on a bicycle wheel, with a rim so that they are very stiff. They have to be very rigid.”

Moore divulged, also, that the entire disc of Whisper’s ducted fan, including the thin blades and outer rim, could be produced as a single piece by dint of pressure injection of thermoplastics, or meltable plastic polymers.

“We spin substantially slower—way, way slower—than any propeller or turbofan. We’re not going to say the precise number, but we spin so slowly that the centrifugal forces on this rim aren’t that significant that it would tear apart,” Moor asserted.

According to Mr. Moore, the slow tip-speed and high blade-count of his company’s propulsion scheme results in a number of the pressure waves resultant of the rotor’s rotation ending up in the ultrasonic range—wavelengths inaudible to the human ear but perceptible to animals.

Nevertheless, Moore alleged: “Whisper’s campus in Tennessee is dog friendly. We’ve had five dogs in physical close proximity to our fan tests, and they don’t react at all to them.”

Some frequencies produced by the company’s propulsors would be audible to humans close to aircraft impelled by such, but still sufficiently quiet to be imperceptible beyond distances of sixty-meters—so stated Moore.

Whisper Aero revealed a mockup of its Whisper Jet, complete with 16 mockups of its ducted fans, at the Tuesday, 13 June exhibition. The company does not, however, intend to produce the aircraft autonomously.

“We’re convinced we can be faster by partnering with an established player, like a GKN or a Honda or Cirrus, rather than trying to do it all ourselves,” Moore remarked—albeit without disclosing the name of the company or companies with which Whisper Aero is considering collaborating.

FMI: www.whisper.aero