Small-unit infantry forces using small UAV’s

[HiloHawaiian]

OFFSET “Sprinters” to Pursue State-of-the-art Solutions for Second Swarm Sprint

I was wondering when this would happen. XSP-sized UAV’s can do a lot more than the tiny ones already in use. This size, if made quieter, could do so much more, and for a longer time...

 

[Cori]

Whether it be a full-sized airplane, or an RC plane/drone, the majority of 'noise' is generated off of the tips of the props. In fact, as the tips of a prop reach the speed of sound (which is very common for any prop) small sonic booms are created by the tips of the prop. Obviously, you can't slow the prop down, and, you can't disrupt airflow over the airfoil. It's a challenge that has it's limitations - due to the task that you are asking of it (to propel air). The tips of airplane wings are now being angled up as it has been found that doing so reduces vorticies and turbulence at the tips of the wing. But, when a wing is 'turned' (as it is with a helicopter, or any propeller), bending the end of the wing upwards is not as effective. Simply put, the best way to make any propeller as quiet as possible is to make it as efficient as possible; thereby reducing the need to turn the prop faster, which, in turn, causes minor sonic booms.

 

[Cori]

The military is using smaller drones, but DJI is not one of them; nor will it be.

 

[HiloHawaiian]

Yea I know, heck, the US Government is now warning agencies not to use routers made with Chinese chips...

There is some very secret prop technology to reducing noise from tips, and all sources, but I doubt Master Airscrew will be selling them anytime soon!

 

[Jagerbomb52]

Silence of the drones: How to quiet that annoying aerial buzz

 

[HiloHawaiian]

Very, very interesting! Ingenious solution to multi-prop noise. Unfortunately, it doesn’t sound like it would apply to helicopers, the scourge of the skies. We will be moving from Hawaii to Arizona by the end of the year, solely because of helicoper noise pollution. Most of my friends and family already left, 80% for that same reason...

 

[KentA]

Silence of the drones: How to quiet that annoying aerial buzz

The future is beginning to look better!

 

[Cori]

Good article Augustine. It also follows the criteria (for noise) that I stated above; particularly that faster moving props (and tips of props) and the amount of air that a prop must move, contributes to noise. By using more props, and even varying the speed of the props, the speed of each prop, and the amount of air it must move, is reduced - thus reducing speed. Note though that the amount of energy to move a given amount of air remains the same, and can even be higher with the additional weight of the additional props. There are no simple trade off's. For the military, they may be willing to expend more energy to attain a quieter aircraft. But, for a hobbyist or even a pro photographer, flight time is usually more desirable than the reduction of a few decibels in sound. Again, there are no easy trade-offs.