29 April 2021

Quiet VTOL and STOL

A new VTOL and STOL family of vehicles and drones uses bladeless fans, similar to Dyson house fans, to be light, fuel efficient, low maintenance, and quiet. 

The VTOL (verticle takeoff and landing) versions have a futuristic look. The STOL (short takeoff and landing) versions have the speed of helicopters, but a much longer range, make much less noise, and can still use primitive short runways with minimal logistics support requirements compared to helicopters.

Jetoptera is more or less agnostic about where it gets its compressed air from, although it reasons battery technology will need to reach energy density figures around 1,500 Wh/kg (current state-of-the-art batteries are around 260 Wh/kg) before it'll start making sense to fit the J-2000 with an electric compressor. In the meantime, it's using gas generators, including a 75-kW turboshaft system based on the Acutronic SP75 for larger propulsion system tests.

What are the benefits? Well, according to the company, this kind of system "improves propulsive efficiency by more than 10 percent while lowering fuel consumption by more than 50 percent compared to small turbojets. The propulsion system saves approximately 30 percent in weight compared to turbofans or turboprops and also significantly reduces complexity." . . .

Jetoptera says these fluidic propulsion systems are "the most silent propulsion method in the skies." The company subcontracted to Paragrine Systems and undertook noise tests as part of a US DoD-funded research collaboration. The results showed the FPS coming in 15 dBA lower than a propeller with an internal combustion engine making the same level of thrust – and this was before any acoustic treatment. The company says once that's done, these things should be as much as 25 dBA quieter than a comparable propeller; at a distance of 300 m (984 ft), Jetoptera predicts noise levels around 50 dBA, which is equivalent to a normal home, quiet office or refrigerator on various noise charts.

No comments: