Mark Moore, Founder and CEO of Whisper Aero, is renowned for his strong views on the necessity for eVTOL quietude and this week he unveiled his company’s hybrid-powered Jet mockup, which uses a slow-spinning ducted fan with a high number of blades, claiming the aircraft is inaudible from 60 metres.
Thirty-two years at NASA focusing on advanced aircraft concepts and technologies and a co-Founder of Uber Elevate which attracted USD3.5 billion investment to establish “aerial ride sharing as a collaborative ecosystem”, Moore is a highly respected engineer within the rapidly growing Urban Air Mobility (UAM) market.
In a recent evtolinsights.com feature, he states, “Community acceptance is critical if this new (UAM) industry is to succeed. I have talked to cities about noise levels and what they will and won’t accept. The truth of the matter is, there’ll be quotas over how much noise a vertiport may accept. If noisy the aircraft will be allowed only a few operations. If really quiet, many more operations. Therefore, what revenue a company can attract is dependent on how quiet its craft is.”
Mark Moore
So, after many years telling the industry how important quiet levels of noise are, Moore has put his expertise and knowledge where his mouth is and unveiled the Whisper Aero Jet mockup alongside a series of three engineering papers, to much excitement and fervour. The papers reveal the Jet’s propulsion method and business plan which were presented at the ‘American Institute of Aeronautics and Astronautics 2023 Aviation Forum.’
The Whisper ducted fan has been “optimised for lowest noise and highest efficiency,” Moore writes in his paper, “Unlocking Low-Cost Regional Air Mobility through Whisper Aero-Propulsive Coupling.” Moore and his co-Founder, Ian Villa, presented the papers on Monday afternoon (June 12th) and the Jet mockup a day later.
Journalist, Paul Brinkmann, from aerospaceamerica.aiaa.org, who interviewed Moore, explains, “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.”
Whisper Aero Team
He goes on, “Another Whisper paper describes how the company’s propulsion technology could be installed on aircraft, theoretically, to provide regional air service in trips of 50 to 500 miles. The company envisions integrating its propulsors on the leading edge of an airplane’s wings to maximise aerodynamic efficiency and thrust, although the company has yet to build such a plane. Whisper has run various tests on its ducted fans, including flight testing of a drone powered by a single such ducted fan.”
Moore tells Brinkmann, “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. The entire disc of Whisper’s ducted fan, including the thin blades and outer rim, could be made in one piece through pressure injection of thermoplastics, or meltable plastic polymers.”
He continues, “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.”
According to Moore, the slow tip speed and high blade count results in some of the pressure waves, or noise, ending up in an ultrasonic range that is not audible to the human ear, yet not high enough to be irritating to animals. Moore remarks, “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 of noise from the company’s propulsors would be audible to humans close to the aircraft, yet still quiet enough that it couldn’t be heard from a distance of 60 metres. Surely, this is a gamechanger for the eVTOL industry?
The company doesn’t intend to produce this aircraft by itself. Moore explains, “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.” Adding, “I am not ready yet to say who that partner may be.”
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