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No Longer a Dream: Silicon Valley Takes on the Flying Car

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Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#51

Post by FabHK »

grenoire wrote: post #28
FabHK wrote: post #12

Earlier quoted context omitted.

Here are a few players in this market (location:firm:product): * Germany: E-volo: Volocopter * Germany: Lilium Aviation: Lilium Jet * Slovakia: AeroMobil 3.0 * EU/Silicon Valley: Airbus Urban Mobility: Vahana * Israel: Urban Aeronautics: Cormorant * China: eHang: eHang 184 * USA: zee.aero * USA: Joby Aviation: S2 * USA: Kitty Hawk * USA: Terrafugium (“legacy”): TF-X * USA: Icon (“legacy”) * USA: PAL-V (actual flying…

PAL-V is not American if I looked it up correctly.

Thanks, looks like I was wrong there indeed.

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#52

Post by [deleted] »

nradov wrote: post #46
robotresearcher wrote: post #23

Earlier quoted context omitted.

> It is a ducted fan ground effect craft, no different than what NASA and USAF have worked on since the 1950's. No, it's not. It's a modern multi-rotor, which have only been possible recently with computer control. No ducts, no (useful) ground effect. Ground effect craft have wings: https://www.google.ca/search?q=ground+effect+craft

Ground effect isn't only a factor for fixed-wing aircraft, it also impacts rotary-wing aircraft including helicopters and the Kitty Hawk Flyer. When you fly a helicopter there is a sudden noticeable loss of lift as you climb out of the ground effect. I'll bet the Kitty Hawk is staying close to the surface at least partially to take advantage of ground effect lift, although the article doesn't make that clear.

[deleted]

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#53

Post by FabHK »

wanderingjew wrote: post #35
1024core wrote: post #8

No mention of Ehang 184: http://www.ehang.com/ehang184 I don't know much about the company, but they seem to have got something airborne in the last couple of years: https://www.youtube.com/watch?v=1iyCgy1juHc

There is a mention of Ehang in the article. However, I cannot put this more succinctly: The Ehang is an abortion of aviation. Instead of going into the idiocy of an autonomously piloted passenger aircraft (which will never be legal under any sane civil aviation laws), I'm just going to go over why the current Ehang 184 doesn't make any sense. The Ehang 184 is an octocopter, with two rotors stacked on top of each othe…

Haha, fully agree - vapour ware, from a toy company. But they claim they'll be operating a taxi service in Dubai this July, in 3 months! Let's see...

The battery life issue (vis-a-vis reserve requirements) is common to all electric VTOL aircraft, and can be mitigated: Batteries will continue to improve (though probably slowly), and regulation seems to transition from strict specification-based rules ("x minutes reserve") to performance-based rules ("enough to ensure safe landing").

Yet, I dislike the eHang 184 particularly for the irresponsible marketing with lots of hype but few facts, the rotors placed to break your knees, the lack of redundancy, etc.

I'm somewhat more positive on the Volocopter (disclaimer: I've invested 1000 EUR via crowdfunding) - what do you think of it?

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#54

Post by FabHK »

beaconstudios wrote: post #45
golergka wrote: post #36

Earlier quoted context omitted.

From your description, it sounds like a solid prototype: fix the lights and other typical prototype stuff, wait for battery technology to catch up, which a LOT of companies around the globe are betting on, and here you have a flying car.

> wait for battery technology to catch up battery energy density improvements are very small and incremental. It'll take decades to go from 23 minutes airtime to something even slightly practical.

From what I gather, battery specific energy has grown by 4% to 8% per annum, so doubling every 18 to 9 years.

Applications in aviation (beyond tiny niche markets) would thus seem two to three decades away.

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#55

Post by robotresearcher »

nradov wrote: post #46
robotresearcher wrote: post #23

Earlier quoted context omitted.

> It is a ducted fan ground effect craft, no different than what NASA and USAF have worked on since the 1950's. No, it's not. It's a modern multi-rotor, which have only been possible recently with computer control. No ducts, no (useful) ground effect. Ground effect craft have wings: https://www.google.ca/search?q=ground+effect+craft

Ground effect isn't only a factor for fixed-wing aircraft, it also impacts rotary-wing aircraft including helicopters and the Kitty Hawk Flyer. When you fly a helicopter there is a sudden noticeable loss of lift as you climb out of the ground effect. I'll bet the Kitty Hawk is staying close to the surface at least partially to take advantage of ground effect lift, although the article doesn't make that clear.

I stand corrected, thanks.

Easy to understand summary of helicopter ground effect, with pictures:

http://www.copters.com/aero/ground_effect.html

I note that the rotary wing ground effect works to a height of about the rotor diameter, so it's not clear to me that this is a useful effect with these small rotors.

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#56

Post by robotresearcher »

robotresearcher wrote: post #22
bigstumpy wrote: post #10

Earlier quoted context omitted.

Why do you say ducted fan?

Or ground effect? Rotor craft have a nasty ground effect, not a nice one, IIRC. It looks like a big multi-rotor with a saddle and pontoons. These are so simple that they'll probably work well enough. Battery life is an issue that's not going away quickly.

> Rotor craft have a nasty ground effect, not a nice one, IIRC.

I was wrong about that. Thanks to nradov above for correcting me.

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#57

Post by beaconstudios »

FabHK wrote: post #54
beaconstudios wrote: post #45

Earlier quoted context omitted.

> wait for battery technology to catch up battery energy density improvements are very small and incremental. It'll take decades to go from 23 minutes airtime to something even slightly practical.

From what I gather, battery specific energy has grown by 4% to 8% per annum, so doubling every 18 to 9 years. Applications in aviation (beyond tiny niche markets) would thus seem two to three decades away.

batteries will likely see a similar drop-off to Moore's law as they approach physical or practical limitations on energy density.

Re: No Longer a Dream: Silicon Valley Takes on the Flying Car

#58

Post by FabHK »

beaconstudios wrote: post #57
FabHK wrote: post #54

Earlier quoted context omitted.

From what I gather, battery specific energy has grown by 4% to 8% per annum, so doubling every 18 to 9 years. Applications in aviation (beyond tiny niche markets) would thus seem two to three decades away.

batteries will likely see a similar drop-off to Moore's law as they approach physical or practical limitations on energy density.

Furthermore, unfortunately, they never approached Moore's-law-speeds anyway!
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