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VTOL On Demand Mobility

VTOLicious

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...btw, those ducted fans aka "electric jet engines" :D must be horrible inefficient, either in hover or cruise flight (fixed pitch). Most likely the reason "the jet" cannot cruise much faster than a modern helicopter.
 
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Grey Havoc

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I was wondering where all the batteries are located to achieve 1 hour of flight time @160kts... and was quite surprised that a rather small hatch for the battery unit can be found in the rear of the vehicle. I would have assumed it is installed beneath the cabin floor.
Probably to allow for quicker swaping out by ground crew, even when there are passengers on board.
 

VTOLicious

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I was wondering where all the batteries are located to achieve 1 hour of flight time @160kts... and was quite surprised that a rather small hatch for the battery unit can be found in the rear of the vehicle. I would have assumed it is installed beneath the cabin floor.
Probably to allow for quicker swaping out by ground crew, even when there are passengers on board.
Installed beneath the cabin does not prevent it to be swappable with passengers on board.
Btw, Tesla's 85kWh batt pack weighs 540kg
 

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VTOLicious

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For spotters near Munich ;)
First lift off took place at Sonderflughafen Oberpfaffenhofen: 48° 4'52.97"N / 11°17'29.90"E
 

Kuyagua

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The main issue with these proposals is that they all work in a vacuum; in other words, they're feasible as R&D projects. But the question remains, how do we add them to the National Airspace (NAS)? I'm not trying to be a party pooper, believe me, I love the idea of taking an Uber air taxi to the airport and get there in 15 minutes for an extra $40, but first we most find a solution to the issue of adding non-conventional aircraft to existing air traffic control (ATC). Once we can tackle that, with the same levels of safety as current aircraft, then the Jetson are here!
 

Grey Havoc

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I suspect the issue will be fudged, at least in most countries.
 

galgot

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Thing is, once the thing is fully developed (?) , how will they handle traffic jams … ? Imagine a dozen of these stationary waiting for a parking space at the airport, with passengers anxiously staring at the batteries level , He he he...
Well at least, maybe it will relieve cars traffic...
 

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distributed landing pads.

This is not a point to point service by essence, customer will be transported from one area to another one. Think electrical scooter: you don't know where you'll get one but you reach your destination anyway. This but on a symmetrical pattern. You are not going to take a flight to get to one specific point downtown. You'll make use of the service because you expect to cut drastically your commuting time and for this, your target is not a point but a zone (defined by your final commuting time (think CCIP - it's similar)). Then as the years goes by more pads will be available cutting final time to destination (Cities will even recompose themselves spreading on the vertical - I made an architectural model of that) in parallel with the growth of demand.
So to resume my say, there will be no "waiting time" around a landing location. The landing location will be distributed among several option according to your ETA.

It's just like if you were flying from, let say, Japan to the east coast/US and didn't care much about landing anywhere b/w Florida and Boston. Cost is the incentive and absence of delay as your total time to end-destination the services offered.

The economical model is sane. We will see a major recapitalization of our old cities.
 
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Orionblamblam

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'Flight' is rather optimistic. 'Hover' would be more appropriate. Still, a cool looking design.
Somethgin abut the video disturbed me for a bit until I thought about it: the video spent more time showing the spectators hugging each other than the vehicle itself doing it's thing. It is, I suppose, a small thing, but it's another example of "feelings" being prioritized over actual merit.
 

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“For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.”

Richard Feynman

The ENRON type “deception in plain sight” continues
 
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Grey Havoc

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Maybe not quite that bad, but caution should certainly be the watchword of the day.
 

AeroFranz

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Somethgin abut the video disturbed me for a bit until I thought about it: the video spent more time showing the spectators hugging each other than the vehicle itself doing it's thing. It is, I suppose, a small thing, but it's another example of "feelings" being prioritized over actual merit.
Because they probably only hovered for 10 seconds, i.e., the entirety of what's shown in the video.

That's a big vehicle (heavy, supposedly 4 passengers+ operator), requires lots of power because the discloading is super high. I can't imagine they have more than a 25% battery fraction. If that's the case, the discharge rate (C-rate) of the batteries in hover must be REALLY high. That is a problem, because you get better specific energy at lower C-rates, and most of the battery development is being pushed by the automotive industry, which doesn't need high C-rates.
I've heard from several quarters that the engineering team bases their performance projections on 'future' batteries with crazy specific energy - virtually unobtainium at this point.
 

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The stacked rotors are undeniably more compact, but unfortunately they don't decrease discloading (thus power required to hover) like individual rotors do. That is, what matters is the projected swept area of the rotors as seen from the top.
I thought that stacked rotors would give you roughly 1,5x thrust, while two individual ones give 2x.
 

TomcatViP

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Disc loading and invicid drag: I have no idea whre the f*** they went with long ducting and wedged outlets regarding the expected output section flow speed.

Someone has mixed Schnaps drinking and CFD.
 

AeroFranz

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The stacked rotors are undeniably more compact, but unfortunately they don't decrease discloading (thus power required to hover) like individual rotors do. That is, what matters is the projected swept area of the rotors as seen from the top.
I thought that stacked rotors would give you roughly 1,5x thrust, while two individual ones give 2x.
In actuator disc theory, the induced power depends solely on disc loading (well, that and density). This has to be divided by an empirical "figure of merit" (FOM) <1.0 (typically 0.6 to 0.8) to get the actual power required, and that's where you see differences based on rotor configuration. For example, a counter-rotating coax rotor might get rid of swirl so could get something like 5% better FOM (YMMV) compared to a single rotor.
What matters in the end, is how much air you are working with for the amount of thrust you want to produce. A closely spaced coax is pushing the same amount of air through two discs, so it doesn't get to count BOTH disc areas for the calculation of discloading. If you hypothetically get the two rotors infinitely apart (in the vertical axis), then they behave like two separate rotors, and you get to count both areas. Obviously for finite spacings between the two cases, you get intermediate results.

Just a SLIGHT correction to my statement about the closely spaced coax pushing the same air through both discs; the flow is actually contracting before and after the top rotor, so the bottom one, assuming it has the same diameter, is also drawing a narrow annulus of "fresh" air from its surroundings to fill the gap. I don't think that increases effective area a ton. Like I said, you really need to push the rotors far apart to see an effect, and for other reasons designers have been pushing for exactly the opposite trend.

The attached picture shows the power requirements of a notional helicopter with different coax rotor spacings. The more you get the rotors close to each other, the more the required power increases. The single rotor has the highest power requirement, but that's because you kept the rotor diameter the same. Normally you'd make it bigger, with much greater area.

Coaxial discloading2.png
 

VTOLicious

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Another contender presented its demonstrator recently: AutoflightX0.jpegD3y-dIfWwAAwzCE.jpgV600.pngD3y-d6CW0AIelRr.jpg
It seems to be one of the more resonable proposals. Most likely CTOL capable as well.
 

AeroFranz

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One minute analysis, i'm sure i'm missing a lot:

The wingtip props have some of the highest download area i have ever seen in a VTOL vehicle. Projected on a top view, it looks like 30+% of the swept rotor area is directly on top of the wing. Maybe that's why the mockup doesn't have rotors in those locations?

The front and second row rotors are overlapping, so they are not decreasing discloading (and power) as much as they could. It's also probably not helping with noise, the lower rotor is probably seeing all sorts of crap flow coming off the top rotor and the boom.

At this scale it's hard to get yaw control by differential torque on the opposite motors, unless you oversize them a lot (but that is heavy). See Cora and Boeing PAV, which have some degree of rotor cant to enhance yaw.

I would be surprised if the fairings under the rotors are sized to actually hold motors. See for example Vahana and Boeing PAV to get a sense of the diameter of the motors required by the class vehicle. If there are indeed small motors, like EMRAX in there, then there's no way to get cooling air to them.

Access to the vehicle is going to be hard, you have to duck under the canard (hahaha, duck...canard...get it? I crack myself up) or jump on top of the rear wing without walking into the pusher prop.

So this is a marketing tool, which is fine, except i'm sure these people are claiming intercontinental range at warp speed.:rolleyes:

My .02.
 

VTOLicious

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AeroFranz, I share all of your concerns, except the overlapping rotors. I think it's a compromise to maximize disc area for a given space... Think Chinook
 

Foo Fighter

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It's a pretty picture/render for investors. Logic and final layout have no place in it.
 

AeroFranz

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AeroFranz, I share all of your concerns, except the overlapping rotors. I think it's a compromise to maximize disc area for a given space... Think Chinook
It may very well be. With these multirotor configurations, your footprint is pretty much dictated by the stacking of the rotors. With eight rotors it's pretty easy to grow to the point where you don't fit within a certain parking constraint.
 

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So you’re flying this thing and the battery burst into flames, so you quickly put it down in a convenient place, but what do you do next? Sit in the cockpit, waiting for the props to stop and burn to death or lose a game of hoop scotch with the rotating props and bleed to death from the leg injuries;- Decisions...decisions . Of course, in this day and age someone will film all this and post it on the web;- what will that do for the investors share price?
 

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I have no background in aircraft engineering, so this is perhaps a stupid question, but why all the rotors? (I have the same question for the Lilium). Surely it is a lot simpler to have the lift generated by a single big rotor, as in the PAL-V?
 

AeroFranz

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Long story short, the multirotor configuration has the advantage that it is more survivable in the case of motor failure. With n rotors, you end up losing 1/n of the thrust, which you must compensate for with the other functioning rotors.
Then there is the fact that to control a vehicle in hover, you need to generate moments - forces at a distance from the cg. having distributed rotors gives you that by just adjusting motor RPM. Compare to the complexity of, say, a fully articulated helicopter rotor head. there's more, but these are the things that come to mind.
 

Grey Havoc

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The Alaka’i Technologies Skai eVTOL:
 

TomS

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Paywall... No further info
Confirmed various other places but no details other than that it crashed in a controlled area and caused no injuries or damage to anything except the vehicle itself.

 

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I am working Le Bourget this week so here are my photos of the Aurora Sciences (Boeing owned) Personal Air Vehicle second prototype as the first prototype kinda of got damaged during hard landing, the other week. Aurora Sciences which was in their own little chalet.

Cheers
 

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VTOLicious

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I am working Le Bourget this week so here are my photos of the Aurora Sciences (Boeing owned) Personal Air Vehicle second prototype as the first prototype kinda of got damaged during hard landing, the other week. Aurora Sciences which was in their own little chalet.
Cheers
Nice, thx for sharing! ...Is there any info about size, weight, tech specs available?
 

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VTOLicious

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Btw, it seems Vahana uses the same brand of motors
...but in combination with 3 blade/variable pitch propellers, due to its tilt-wing configuration.
 

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Grey Havoc

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Behind the somewhat underwhelming, drama-free demonstration lies a bigger ambition: Japan’s government wants the country to become a leader in flying cars after missing out on advancements in technology such as electric cars and ride- hailing services.

The country’s technological road map calls for shipping goods by flying cars by around 2023 and letting people ride in flying cars in cities by the 2030s.

“Japan is a densely populated country, and that means flying cars could greatly alleviate the burden on road traffic,” said Kouji Okada, a leader of the project at NEC.

“We are positioning ourselves as an enabler for air mobility, providing location data and building communications infrastructure for flying cars.”

For the past few years, Japan has seen the emergence of a small, passionate flying car community that believes Japan has the engineering expertise and right environment to foster a global flying car industry. Venture capitalists in the country set up a specialized fund, known as the Drone Fund, devoted to investing in autonomous aircraft in general and flying car businesses in particular.

Although the demo is among the first by a major Japanese corporation, NEC isn’t planning to mass-produce the flying car, according to Okada. Instead, project partner Cartivator will start mass producing the transportation machine in 2026, according to the startup’s co-founder, Tomohiro Fukuzawa.
 

VTOLicious

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"One of the keys to unlocking the future of Urban Air Mobility (UAM) is exploring how different technologies and configurations of aircraft will perform in the urban environment. To start gathering as much data as possible, NASA engineers are moving forward with their newest modular unmanned aerial system, the Langley Aerodrome #8"
 
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