Big Week For Drones: Dubai Permits Passenger-Carrying Drone; Kenya Finally Approves Commercial Use (apnews.com) 47
It's shaping up to be a major week for drone enthusiasts. A pilot-less drone designed to carry one passenger at a time is set to start making regular trips in Dubai later this year. In some other news, Kenya has joined the neighbor Rwanda in opening up its skies for commercial drone use. From an AP report: Up, up and away: Dubai hopes to have a passenger-carrying drone regularly buzzing through the skyline of this futuristic city-state in July. The arrival of the Chinese-made EHang 184 -- which already has had its flying debut over Dubai's iconic, sail-shaped Burj al-Arab skyscraper hotel -- comes as the Emirati city also has partnered with other cutting-edge technology companies, including Hyperloop One. The question is whether the egg-shaped, four-legged craft will really take off as a transportation alternative in this car-clogged city already home to the world's longest driverless metro line. From a Quartz report: Flying a drone will soon be legal in Kenya, which has effectively banned the use of unmanned aerial vehicles for anyone outside of the military for the past two years. A spokesperson for the Kenya Civil Aviation Authority (KCAA) said that draft regulations for the commercial use of drones had been approved by security officials. The agency said details of the law would be released soon. The approval comes as regulators elsewhere in Africa have tightened restrictions on UAVs. In Ghana, flying an unregistered drone is punishable by up to 30 years in jail. In Nigeria, operators require permits from the aviation authority as well as the office of the National Security Adviser (the process of getting a permit costs up to $4,000).
I don't like the EHang 184 design (Score:2)
Those rotors ought to be in enclosures, and over the pod instead of below it.
Actually, they ought to be on the end of vertically offset stub wings for added lift during forward flight, increasing efficiency, and able to tilt forward to provide more thrust as the wings provide more lift.
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But seriously: how is the EHang "drone" any different than a crappy little helicopter?
Stability. A quadcopter is inherently more stable than a traditional helicopter with a single main rotor and a stabilizer rotor on the tail. The reason for the traditional design is that a human doesn't have four arms and the mental flexibility to control four rotors at once. But with a computer, that is not a problem.
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Quads are good in small scale due to propeller eff (Score:4, Informative)
Because of the physics of propellers, quads are workable in small scale (toys) but the efficiency is horrendous in large scale. Experimental helicopters have been built with two and four propellers for many, many years, but never commercially because they are horribly inefficient.
The thrust of a prop is proportional to SQUARE of blade length. In other words, it's proportional to the swept disk area. A 10 foot prop makes over ten times as much thrust as a 3 foot prop, so having four props of 3 feet each is very inefficient compared to a single 10 foot prop.
On a toy sized example, you can live with the inefficiency to get lower mechanical complexity due to another issue with scaling. Basically, for each dimenaion to scale linearly, weight is cubed. Consider a boom that is 1cm X 1cm x 10cm on the small craft. We want to scale it by a factor of ten. It becomes ten times as long, 10cm X 10cm x 100cm. Not only is is ten times as long, it's also ten times as thick and ten times as wide - a thousand times as much total mass, a thousand times as heavy.
Because of that cube calculation as you scale up and down, very small (toy size) craft can have phenomenal power-to-weight ratios and get away with stuff that's not possible in full-sized craft. For a full-sized craft, power-to-weight is a very significant issue. You can't have tiny, inefficient props on a full-size craft, you need a long prop which cubes the thrust.
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A 10 foot prop makes over ten times as much thrust as a 3 foot prop, so having four props of 3 feet each is very inefficient compared to a single 10 foot prop.
But I bet that quadcopters have less blade-vortex interaction interaction noise, or at least it is at a less annoying frequency than "whop whop".
Ceiling fan versus hair dryer (Score:3)
About noise:
A ceiling fan moves about ten times as much air as a hair dryer. The hair dryer is far louder because smaller is louder, for the same airflow (or even 90% less airlfow).
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Quadcopters are *not stable at all*. Without the flight controller and its gyro sensors they would immediately crash. This goes way beyond the computer turning a human's movements of the two sticks into throttle inputs for four or more motors -- it also makes sure that when the human isn't telling it to do something that it doesn't do anything. Turn this off and the craft would flip over and crash in a few instants.
That said, these flight controllers can be used on traditional helicopters too, making the
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>how is the EHang "drone" any different than a crappy little helicopter?
It's easier to fly on autopilot.
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The Ehang is an octocopter -- so it can lose somewhere between 1 and 4 motors/props and still fly properly. (Exactly how many can be lost depends on which ones are lost and how much thrust it needs to maintain altitude.)
That said, if it loses power completely, or the computer crashes or something ... it might as well be a brick for how well it'll fly. There will be no autorotation.
That said, I see no reason why they couldn't equip it with a ballistic parachute in case something does go horribly wrong.
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Lose one motor and the remaining motors can get you all the way to the crash site; so quickly and efficiently, in fact, that you'll probably beat the ambulance by a good 1/2 hour or so.
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Are you making a joke, or are you not familiar with multicopters?
If one motor dies or its prop breaks or something, the computer detects that and turns that motor off, and the motor on the opposite side of the craft (which will be spinning in the opposite direction.) This will keep the forces balanced.
Then you speed up the remaining motors to make up for the lost lift. Given that you've only lost/turned off 25% of your motors, the thing would almost certainly still be able to maneuver normally. Performan
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Those rotors ought to be in enclosures,
they ought to have rings around them, anyway.
and over the pod instead of below it.
That doesn't really matter. It's not that relevant to stability even where you put the battery on say a 250 size quad.
Actually, they ought to be on the end of vertically offset stub wings for added lift during forward flight, increasing efficiency, and able to tilt forward to provide more thrust as the wings provide more lift.
The beauty of quadcopters is how simple they are. Not having any control surfaces to go wrong is a massive win.
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Quad copters are not more stable then helicopters, in fact it is the opposite. Quad-copters require constant small adjustments several times a second and connot be flown entirely manually. Quad copters are like the F117. they are inherently unstable and thus highly maneuverable. Also Quadcopters rarely have variable pitch propellers and thus cannot auto-rotate making them far more dangerous for passenger transport.
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>having 4 motors where one failure is catastrophic.
Solution: add a ballistic chute that fires off in the event of emergency.
Even with just four rotors you can lose one rotor and go into a slow descent with the rotor opposite the failed one dedicated to maintaining balance and the other two remaining rotors at near-maximum thrust.
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Even with just four rotors you can lose one rotor and go into a slow descent with the rotor opposite the failed one dedicated to maintaining balance and the other two remaining rotors at near-maximum thrust.
Unless the rotor opposite the failed one can *reverse* ... that's not going to work, and even if it can, the odds are pretty good that it can't switch between going forward and backwards quickly enough to overcome the instability on the axis between the two working props that this mode would have.
*Maybe* this could be made to work better (and without reversing) if the center of gravity was shifted towards the motor/prop dedicated to maintaining balance. (Tell the passengers to lean to the front right!)
Also
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No, just having 4 motors where one failure is catastrophic.
Not necessarily entirely catastrophic. If it has enough excess thrust it's theoretically possible for a drone to sustain controlled flight with three out of four props out of action.
I mean, it's not pretty, and if it's scaled up to passenger size it would probably kill the occupants anyway even if it didn't fling itself apart, but still...
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No, just having 4 motors where one failure is catastrophic.
Actually, some designs can descend on 2 motors, if they are opposing. And if you use 8 motors on 4 booms, you can lose any 2 motors and still descend.
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Quad-copters require constant small adjustments several times a second and connot be flown entirely manually.
So what? That's cheap now, and it's toy technology. You can do it with an Arduino. A $3 one.
Also Quadcopters rarely have variable pitch propellers and thus cannot auto-rotate making them far more dangerous for passenger transport.
Whole-aircraft parachutes are a thing these days. I didn't do the work to figure out if these guys are using four motors for their eight props, or if they have eight motors, but I'd want to use eight motors, at least two redundant control systems, independent motor controllers...
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I didn't do the work to figure out if these guys are using four motors for their eight props, or if they have eight motors, but I'd want to use eight motors, at least two redundant control systems, independent motor controllers...
Motors are small and cheap -- there's little advantage to one big one per boom driving two props over two smaller ones, one for each prop ... and some big disadvantages.
I'm pretty sure they'd design it exactly as you said, including a ballistic chute in case everything goes wrong. Anything less for a human carrying craft would bankrupt the company the first time one crashed.
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>>and over the pod instead of below it.
>That doesn't really matter. It's not that relevant to stability even where you put the battery on say a 250 size quad.
Well, it's easier to duck under something that's 5' off the ground than something 2' off the ground...
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The design is very compact and simple. Wings would block air flow, unless they tilt (along with the motors), which adds addition complexity and weight. Possibly making it less efficient than skipping the wings all together.
Rotors in enclosures are much less efficient. Maybe you're thinking it's a safety issue. The rotors can be electronically braked on landing to stop them almost instantaneously. Like wise, the control system can ensure the rotors are not powered up until the doors are closed and latch
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Rotors in enclosures are much less efficient.
But then you say:
This isn't a long range endurance vehicle. It doesn't even have to be efficient.
Surprised (Score:2)
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Unlike self driving cars that need to integrate with unpredictable human drivers, a fully automated system takes humans out of the equation.
Now we just have to worry about unpredictable Canadian Geese or Sandhill Cranes, in my area at least...
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It's not possible at a decent price (either cost or risk):
* Hovering will always require more energy than driving.
* Hovering will always be more sensitive to weather conditions than driving.
* Hovering will always have more dangerous consequences to equipment failure or operator error than driving.
* Hovering won't solve end-point congestion, since we're all rushing to the same places. (Check out your average parking lot!)
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Weather can play to air when roads are iced. There is no operator, equip failure is not much different than a car. A self driving car that runs into another car is just as dangerous as a single man copter that loses altitude. Parking could get better. These things are pilotless so after the dropoff they could go park elsewhere. And not everyone is going to the same endpoint. I know people in the south part of town that work up north and vice versa. Those extra lanes in the sky would significantly reduce roa
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* Hovering will always require more energy than driving.
A personal Zeppelin would be a good solution to solve this problem.
* Hovering will always be more sensitive to weather conditions than driving.
Maybe but having 200 lanes of traffic versus 4 lanes of traffic means that even if you have to travel a little slower, you never get into a traffic jam.
* Hovering will always have more dangerous consequences to equipment failure or operator error than driving.
Computerized flight in the air has limited obstacles. You don't have to worry about deer, road closures, children playing ball, etc... Much easier than a self driving car.
* Hovering won't solve end-point congestion, since we're all rushing to the same places. (Check out your average parking lot!)
Sure it will. Vertical takeoff and landing in a parking lot eliminate most of the end-point congestion.
Arab engineering (Score:2)
Vancouver has the longest driverless metro line (Score:2)
Dubai used to hold that record, but since last year Vancouver's Skytrain is the world's longest driverless transit system. https://en.wikipedia.org/wiki/... [wikipedia.org]