British Start-Up Tests Flying Saucers

Sabre Runner writes to mention that a new British start-up, Aesir, has acquired the assets of a defunct drone company and is working on evolving a working model from several prototypes of "flying saucer" drones. "Aesir's first prototype, named 'Embler' [...] demonstrates the so-called 'Coanda effect,' where air speeds up as it 'sticks' to a curved surface. Aesir's drones take advantage of the Coanda effect to direct air down, away from the drone, boosting lift. Aesir doesn't appear to have any paying customers yet — and is reportedly bankrolled by a single investor."

Comments

Sigh

[Kell Bengal]

I see a lot of these sorts of start-ups - people who design a VTOL UAV using some fancy lift generation device. Entecho entecho.com.au immediately springs to mind (if only because a friend works there). What these people aren't getting is that the problem with VTOL UAVs isn't the form of the lift production, it's the energy density of its power source. Think about it, the power needed to lift a mass is inversely proportional to the square root of the rotor area - that is, the more area, the less power. Things like this use a much smaller area to accelerate air than an equivalently sized helicopter rotor. Yes, they can bump into things, but their flight time will be slashed.

It's hard to make a more efficient rotor, and it's hard to make a duct light weight at large enough sizes to compete on power. So, unless I'm missing something these guys are using the same petrol/kerosine/lipo power sources as everyone else, except with higher power consumption. It's the same problem quadrotors and jet VTOLs have - they simply can't compete with helicopters on hover efficiency.

That's bad news for startups, though, because the helicopter space is already crowded with heavy hitters like Sikorski and the like.

Where does this leave UAVs? It leaves us with incremental improvements (my PhD involved making freaky aeroelastic UAV rotors that were fiercly optimised for the hover regime, just to squeeze out more flight time) with no real long-term flight performance in sight.

Why do these start-ups appear and disappear so quickly? Because they're trying to 'solve' a hard laws-of-physics style problem that isn't bounded by UAV technology, but rather power technology.

YIAAUHETYVM (Yes I Am A UAV Helicopter Engineer, Thank You Very Much)

The Truth About the Coanda Effect

[thepainguy]

The point of the Coanda effect is NOT that the flow speeds up. Rather, and as Wikipedia correctly points out, the point of the Coanda effect is that the flow stays attached to the curved surface, which allows you to redirect it...

The CoandÄf effect is the tendency of a fluid jet to stay attached to an adjacent curved surface of a specific radius. The principle was named after Romanian aerodynamics pioneer Henri CoandÄf, who was the first to recognize the practical application of the phenomenon in aircraft development.

FYI, the Coanda effect is what makes leafless gutter systems work. It allows the water to turn the corner and enter the gutter while the leaves shoot over the side.