Second MoD Airbus Zephyr spy drone crashes on Aussie test flight A second Airbus Zephyr high altitude pseudo-satellite (HAPS) drone, built for the UK's Ministry of Defence, has crashed in Australia while on a test flight. The 25m-wingspan aircraft reportedly crashed after encountering turbulence, according to a local news story. It was being flown from Wyndham, a remote airstrip in a …
Man 1: "We had to make the frame ultra-light, so it doesn't handle turbulence well, might crash."
Man 2: "But it's weather-tight otherwise?"
Man 1: "Of course. However, rain tends to weigh it down and performance decreases, might crash."
Man 2: "Can't get it wet and keep it out of the wind. Can't imagine that will be a problem. So what's the cost?"
Man 1: "4.1 million Pounds each, might crash."
Man 2: "We're paying for this out of an MoD account, so we'll take fifty."
Man 1: "Excellent. That will give you superb coverage of all of Afghanistan."
Man 2: "Oh no. These are for post-BREXIT border enforcement in Northern Ireland.
synchronous motors are for AC current (the rotating shaft is synchronised with the alternating phases, thus the name), and solar panels give DC current, so I think that's wrong. But 2 engines of 0.45kW (450W) sound more realistic than a 300W motor.
Getting closer. I bet they are 3-phase brushless outrunners
I remember overhearing many years ago from my electrical tutor at university, that synchronous motors are the most efficient. DC to AC conversion is very good these days. Maybe the efficiency of a synchronous motor with a DC to AC converter just wins the maths....?
(though I would also imagine that one speed props have their limitations unless they are variable pitch)
Old style synchronous motors used brushes to supply the rotor windings with current - the rotor's magnetic field would sync up with the stator windings' rotating magnetic field (typically 3 phase induction motor style windings). If the rotor's magnetic field became too low, or the load on the shaft too high, synchronous motors can "slip a pole" which results in a current spike, which can trip the motor offline.
Brushless / permanent magnets are ably to supply a constant rotor magnetic field without slip rings (which is good, as slip rings require brushes and maintenance). Hopefully, the magnets are strong enough to not slip a pole.
Most likely, speed is controlled by changing the frequency of the incoming 3 phase AC - something like 20 Hz to 200 Hz - which would be handled by the static inverter. Chances are, each motor would have it's own static inverter aka speed controller.
I'd go with 100% yes and frankly even if you hit it with a modern jet it would cause less damage than a bird strike.
The flightglobal site says it can travel around 1000km per day, that gives it a cruise speed about 40km/h, at its operating height I'd think anything more than slight buffeting will cause it to drop out of the sky as it overstresses the frame.
Looking at the pictures it seems clingfilm is being used as the aerodynamic surface covering. If you tried to make anything substantially more robust than this you'd soon be looking at a design not unlike a U2.
From the military PoV, $4.1m for a 100 days of use makes these throw-away technology.
Unfortunately for Airbus, the £4.3m Zephyr surveillance drone encountered "clear turbulence" while climbing away from the airstrip which caused it to tumble out of control
Does it mean that the software was not able to control the movement of the plane in the turbulence? I wouldn't be surprised, flying a glider is a lot more difficult than a normal plane. However there might be some missing, not so small, details in the article. It would be interesting to know whether at least the structure is strong enough to sustain some turbulences or it is fragile as an old zeppelin.
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