CES, the Consumer Electronics Show, is in full swing. Just for a second, let’s take a step back and assess the zeitgeist of the tech literati. Drones – or quadcopters, or UAVs, or UASes, whatever you call them – are huge. Self-driving cars are the next big thing. Flying cars have always been popular. On the technical side of things, batteries are getting really good, and China is slowly figuring out aerospace technologies. What could this possibly mean for CES? Self-flying drone cars.
The Ehang 184 is billed as the first autonomous drone that can carry a human. The idea is a flying version of the self-driving cars that are just over the horizon: hop in a whirring deathtrap, set your destination, and soar through the air above the plebs that just aren’t as special as you.
While the Ehang 184 sounds like a horrendously ill-conceived Indiegogo campaign, the company has released some specs for their self-flying drone car. It’s an octocopter, powered by eight 106kW brushless motors. Flight time is about 23 minutes, with a range of about 10 miles. The empty weight of the aircraft is 200 kg (440 lbs), with a maximum payload of 100 kg (220 lbs). This puts the MTOW of the Ehang 184 at 660 lbs, far below the 1,320 lbs cutoff for light sport aircraft as defined by the FAA, but far more than the definition of an ultralight – 254 lbs empty weight.
In any event, it’s a purely academic matter to consider how such a vehicle would be licensed by the FAA or any other civil aviation administration. It’s already illegal to test in the US, authorities haven’t really caught up to the idea of fixed-wing aircraft powered by batteries, and the idea of a legal autonomous aircraft carrying a passenger is ludicrous.
Is the Ehang 184 a real product? There is no price, and no conceivable way any government would allow an autonomous aircraft fly with someone inside it. It is, however, a perfect embodiment of the insanity of CES.
The first scary bit are the 4 blades whirling on 106kw motors right about the door. Get to the destination, pop the door open and want to run inside, but you want to use your legs to go home.
But as I will always point out, people in quad (octo) copters have no plan B. If there is a power failure of any kind, the occupant will be having a funeral next saturday.
According to what they’ve said, the thing can survive the failure of a motor or propeller, since there are eight of them (two on each boom). They imply that it will immediately land in case of failure, so the loss of thrust from a failed engine is probably going to be a lot like when a helicopter loses power and autorotates to the ground. Not exactly a crash, but not something you want to do, especially over challenging terrain.
Of course, there are tons of scenarios when you might lose both props on a boom (or multiple booms), such as a birdstrike involving a flock of birds. You might mitigate that somewhat by adding an automatically-deployed ballistic parachute. But that adds weight and complexity. It also requires the public to get comfortable with the idea of these things raining down from the sky in parachutes if there’s a major issue.
Assuming they’re somewhat smart, the top and bottom rotors will be completely independent systems with enough spare power to soft land solo. Add in a ballistic recovery parachute, and it would be pretty safe to fly in. Wonder if it folds up small enough to fit in a standard parking space.
It needs to fold up into the standard briefcase.
-George Jetson
Interlock on the door until rotors stop turning would protect the passenger. Still have to worry about excited hosts prematurely running up to you…
There’s actually a surprising amount of redundancy in an octo-copter. All 8 motors (should) have their own ESC. They could even have dedicated battery packs. Based on this video, in theory you could lose up to 5 systems and still walk away from the landing (albeit rather dizzily) https://www.youtube.com/watch?v=bsHryqnvyYA
AIUI, you can fly a quad with just 3 of the rotors (or 6 of the 8) turning, although performance is going to suffer. Should be enough to get you to the ground though.
It is a bit worrying to see the blades unprotected, but then again helicopters manage fine. If a helicopter blade is damaged, you just die, but they’re still pretty safe.
As far as the leg-shearing, perhaps have the booms telescopic, so they normally stow retracted until takeoff. Also means it’d be easier to load on the back of a truck or whatever. Then once the pilot’s onboard, an onboard sonar checks for free space around the vehicle, and then extends the booms.
The booms can use some sort of failsafe technology, where they lock in place if power or a mechanism fails, something like an electric screw-drive.
Among the many issues – my first thought was: Is that 23 minutes total, or usable? Don’t FAA requirements specify 15 minute reserve after landing (under VFR conditions; IFR its like 45 minutes after rerouting to an alternate, right?)?
So if it’s 23 minutes total, that leaves 8 minutes of usable flying time – on a good day. Grounded before you start the rest. Don’t know of too many airports that are 8 minutes apart….
Oh, and I think they screwed up the nav lights, no? Red in front, green in the rear?!?! Shouldn’t it be red on left, green on right?
Either I know less than I thought about aircraft (and given how little that is, I’m fully prepared to be corrected), or this is vaporware.
Isn’t this like a tech demo from a chinese company? I don’t think they made it with the FAA in mind.
Might be the Chinese government, who are pretty unassailable, and very keen on technology, would allow something like this, including lower restrictions on power reserve. Possible a separate battery and power system would be good for the reserve. Could cause a boom, after a few rich, brave showoffs start using them, leading to popular takeup.
Then once the first few Chinese fall out of the sky, and they fix the bugs, people will be pushing Western governments to allow them.
I dunno, it could happen. Personal helicopter might be a game-changer, we’ve been due them for 16 years now.
It really really needs to be able to do a fixed wing conversion and operate that way (I realize there’s associated complexity and weight and costs and…). At least then there’s the possibility of usable flight time and a limp home mode. There’s no point to the maneuverability of a copter setup except at the endpoints.
A fabric delta wing that opens? Like the triangular ultralights…
That would add more complexity, more cost, more chance of pilot fuckup / computer fuckup.
Might be that something horribly inefficient, but cheap and does the job, would be the way. Worked for the incandescent light bulb, long since past better options were available. Economics / people are funny, and rarely coincide with the best technical solution.
Why would you have to start and end at airports? My commute might be 8 minutes as the crow flies with zero traffic, this thing is supposed to average 100Km/hr. Now if only my commute wasn’t under class B airspace…
I guess that makes sense since we’re talking about a fantasy world where this thing would actually be allowed to fly. But until then, you are not (legally) taking off / landing inside any metropolitan area, except at an airport.
Yeah but legally you couldn’t even fly this from an airport. May as well consider fantasy world / different air traffic regulations.
This is going to fly much lower than any aircraft, for one thing it’s not pressurised. Keep an exclusion zone around airports, and it wouldn’t interfere. Then it just has to deal with it’s own problems.
“Oh, and I think they screwed up the nav lights, no? Red in front, green in the rear?!?! Shouldn’t it be red on left, green on right”
Just fly it sideways B^)
I’ve heard the takeoff and landing of helicopters is the most dangerous part by far. I wonder whether automating the process would make it more or less dangerous.
Helicopters != multirotor craft.
The problems that helicopters have aren’t necessarily the same problems multirotor craft have.
IME, with tiny RC helis, the takeoff and landing is hard because of the downwash/ground effects that the heli creates. With 4 little rotors rather the one big one this effect is lessened. At least, that’s how it feels when I’m flying them.
Not to answer your question, assuming a decent autopilot and a decent pilot, I’d say the autopilot is safer. A computer can make millions of tiny adjustments a second. Adjustments to the tiniest of inputs that a human wouldn’t even notice. If you are talking about a shitty chinese made autopilot vs a well trained human, or, a decent autopilot vs someone who has never flown but has more money than brains….. Well, then the calculus changes a wee bit.
Actually, the tiny RC helicopters I’ve flown don’t really have issues with takeoff (landing might actually require skill, it’s been so long since I learned how to do it I don’t remember). Takeoff is Ludicrously easy in the RC heli world thanks to insane power to weight ratios. You don’t have to deal with the downwash because simply jamming the throttle stick to full launches the helicopter like a missile hundreds of feet into the air. Mine is a bone stock trex450 but my logo10 HV setup would do the same thing with a higher head speed (it’s setup for AP and flight time) Hmm. Now I’m going to have to look up the acceleration forces involved, I’m sure someone has measured it. I’m guessing if it were sized up to full size it would easily cause a blackout.
The shitty Chinese autopilot is likely to use open-source stuff, if it’s available. So just needs some chaps who know what they’re doing to write some, the Chinese aren’t going to spend money on software if they don’t need to.
Question to people that know better than I do:
It has 8 106kw motors, so 850kw total. Right? If you wanted to power it with fossil fuels or hybrid electric rather than purely from batteries, what would that take? Going to Home Depot buying a >850kw generator and lugging it in?
850kW is ~ 1200hp. Oh, and ICE engines are only 30% efficient, so 3,600 hp ICE engine.
(I’m betting the power output is peak output to sound impressive – A Robinson R22 personal helicopter by way of comparison only has a 160hp engine – https://en.wikipedia.org/wiki/Robinson_R22)
Peak, then multiply by 10. Same with Chinese electronics.
You’d want to go up one small step from 850kW to be sure of enough power to run the various other comfort and control electronics. 850kW is almost 1200 Hp, so you’ll need an engine of about 1200hp output at the generator. And no, just because engines are not amazingly efficient doesn’t mean you need to triple the rated output power to have the output power you want.
If you wanted 1800hp output from a reliable generator, you’re looking at something like a Detroit 24v71. Almost 30L total displacement and is going to be quite heavy, not counting the weight of cooling, electrical controls, fuel, and the generator unit itself.
The issue becomes the question of if the unit can even lift the power supply.
I wrote a blog post a while ago about why we haven’t seen more flying cars. It comes down to energy. We stopped growing our energy supply(US) in the 70s.
http://blog.bitheat.io/why-we-dont-have-flying-cars/
self flying cars? ever tried to fly legally anywhere with any class of license?
1. Electric engines are much more safer than fossil fuel engines
2. IMHO these will be much safer to fly than helicopters or ultralites
2. 23 mins flying time @100km/hr less ramp up/down speed, so lets say 18 mins @ 100km/hr = 30km range.
3. Lands easily on a lawn / backyard / parking area / street / etc.
Now, add the battery improvements while production starts, and I would expect 50km range. This puts it within many commuters range to/from the workplace. For the right price, I would expect demand to outstrip supply!
FAA’s around the world, lookout! Rules need to be thought about quickly here – it won’t be long now ;)
BTW – be careful of those dreaded overhead wires :)
I’m pretty sure it’s 106kW total power, distributed over 8 motors. This means 13.25kW per motors, which makes a lot of sense for the size of these on the render. I’ve installed 50HP (38kW) motors before and it’s almost half the size of the cabin itself…
Wizzboy is right. 106kW total power make a lot more sense. I did some quick calculations with the same spreadsheet I used to design Goliath. Making some assumptions about the rotor RPM (2500), chord (5 in) and air density (sea level, 70F), I calculated the hover power required for 660 lbs to be 46 kW (66 Hp). 106 kW peak would be reasonable to account for altitude density and maintain maneuverability.
I added a spreadsheet to the Goliath repository with the calculations if anyone wants to take a closer look:
https://github.com/mccloudaero/goliath-quadcopter/blob/master/drive_system/ehang_184_disc_loading.ods
It’s says 14.4KWh on the page, but 23 minutes fly time seems a bit too much, it would mean flying at 38KW.
Did you also see any bridges for sale at CES?
In theory “staying at the same place” does not require any energy. How much energy does it take to keep a rock at 1000m Above Sea Level? None. Put it on a mountain.
The efficiency of hoovering depends on how fast the air is moving that you “throw” downwards. If the air that you’re “throwing downwards” is already moving, That’ll cost you in efficiency. Accelerate 1kg of air in one second from 1m/s to 2m/s requires 3J and gives you 1N of lift (for one second). But start with 4m/s air, and the energy requirement is 9J but still givves you only 1N of lift.
So putting one prop in the downwash of another will reduce efficiency. Similarly, smaller props are less efficient of themselves, but also, the larger the prop, the slower the “exhaust” air is moving and the more efficient you are.
interesting, but then why do we see so many (pro) multirotors with props (and motors) mounted on the top and bottom of each arm ?
While efficency goes down, the alternative would be a bigger and more complex frame. Eigth arms instead of four or four longer arms and bigger props but then you would lose redundancy wich is no fun If you are the one ridning it. Stacking the engines is the easiest way to increase lift and adding redundancy without increasing the size of the machine
the units in the spec sheet are so inconsistent i wouldn’t trust a sandwich made by these guys
200KG, 100km/h, 106kw, ..
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