JAXA has been working with ACSL Ltd. to convert the “Looprop” low-noise propeller developed for aviation into a drone propeller. SHIMA Eiji, who is involved in this development, relates the background and details of this project.

“Drones are currently being used in various fields such as observation, security, etc. and are being tested for use in the logistics sector, and it is expected that more and more drones will be flying close to residential areas. One issue this poses is the noise generated by drone propellers. To resolve this, we have been researching ways to reduce noise for the past few years.”

Looprop, the basis for this joint development, is a loop-shaped (figure-8) propeller developed by JAXA to reduce aircraft noise.

“The key to achieving low noise is the large curvature of the propeller. This allows the propeller to make gentle interaction with the surrounding air during rotation, resulting in a noise reduction effect. However, an ordinary slender propeller used for aviation that is curved to this degree is easily deformed at high rotational speeds and thus cannot achieve the desired performance. The unique feature of this technology is that a loop-shaped propeller is structurally formed using a proprietary technology.”

JAXA was quite proficient in low-noise propeller design but had no experience in applying this strength to drones. Collaborating with ACSL, which has the technical capability to design drones, thus made it possible to realize a low-noise propeller suitable for drones.

“In this joint development, we first created a Looprop for ACSL drones that exactly simulated the geometry parameters of the prototype propeller. However, we were unable to achieve the performance we had hoped for. The Looprop shape has the advantages of being thin and light, but its thinness made it floppy.”

Shima and his team continued their research. “For the second prototype, we modified the Looprop to be thicker while keeping the same weight and also improved the design theory, resulting in good performance.”

Shima recalled that making improvements under cost and schedule constraints was nerve-wracking. He then shared his hopes for future developments.

“In this type of propeller, a wide range of products can be fabricated using common materials, so it can be used not only for drones but in all situations where propellers are used. We hope this technology will be widely used in the future, for example, in flying cars.”

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