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Generic Default wrote:I'm glad you noticed the math too! I wouldn't call them inventors since they made a relatively low quality animation of a flying car. Most attack helicopters have two turboshaft engines, each providing around 1500 to 2500 horsepower. They use two in case one fails or gets blown up ect.

A flying car, assuming it's unarmored and made from carbon fiber or glass fiber (instead of cannon-proof glass and sheet metal) would need a lot less power to stay in the air. For quadrotors and small RC aircraft that don't have efficient wings, you need about 1 watt of power per ounce of weight. Which is convenient for us, just multiply the weight of the flying car in pounds by 16.

Assuming similar efficiency, a 1000lb flying car would only need 16,000 watts to hover, which is surprisingly do-able. A regular hydrocarbon fueled engine and tank would be more than capable of powering a lightweight flying car for hours at a time. The power not used for downward thrust could be used for forward propulsion (assuming the car has that). At higher velocities, wings could increase the efficiency.

Does my 16,000 watt estimate seem reasonable? I got the watt-per-ounce estimate from known values of power consumption vs weight in quadrotors. It just seems like a small amount of power needed to make something fly.

Your not going to get the weight down to 1000 lb. The tesla, which does not have a 300hp gas motor or a Megawatt of total electric motors weighs in at 4650 empty, add two adults and your getting near 5000 lb, without any of the parts to make it fly, or any of the 300hp gas motor stuff. And the Tesla has an aluminum frame to save weight.

I would go by their number of 1 Megawatt required to fly, seems on par with a civilian helicopter. Your 16kW number /1000 lb ( 80kW for 5000 lb) still seems low - you could maybe get it in the air if it has big wings and that much power, but forget the vertical takeoff and landings.

There are other problems, too. Rules of thumb like the quadcopter power loading assumptions typically only apply when a very specific set of assumptions are valid, and scaling up from a model quadcopter to a human-carrying air vehicle inherently breaks several of those assumptions.

If you take the form of the power equation that relates it to thrust (which must be greater than weight by enough to allow for losses, a reasonable rate of climb, and forward flight), power is proportional to thrust to the 3/2 power (adding weight requires disproportionately more power). The highest power loading Raymer cites for civil/utility helicopters is 8 lb/hp. Even if you could manage to hold the vehicle to 1,000 pounds maximum gross (which would be a mighty tall order), that would be 125 horsepower or 93,250 watts.

If you're stuck on the idea of calling it a flying car, there's a lot of overhead in safety and emissions regulations that will add weight and reduce efficiency. Making it a trike and tagging it as a motorcycle would circumvent much of that, but it's still not realistic to expect 1000 pounds. My non-flying motorcycle weighs about that with a tank of gas...And that's without me on it. There are lighter bikes, but when you consider fuel, operator, additional hardware and structure to make it fly (never mind hover), it would be a tall order.

There is typically a 1320-pound limit for aircraft registered in the Light Sport Aircraft category. Terrafugia has already gotten an exception for their Transition to 1430 pounds and requested a further exception to 1800 pounds to allow for street-legal systems. The additional equipment to make it VTOL capable would be even heavier.

93,250 watts seems a lot more realistic than the 16,000 in the last post, from the specs I've been reading on military helicopters it seems to be a ratio of at least 375 watts per kilogram, and that's just to get off the ground. I found commercial boat engines that weight around 500 lb for 300 hp. So that leaves around 1000 lb for people, the entire airframe, fuel tanks, and other stuff if the flying car is going to stay in the range of 1500 lb.

I don't know how dense airframes typically are, but it seems like most new aircraft are being built with composites and plastics as a preference to sheet metal.


Sorry for everyone who isn't familiar with these measurement units. I'm too lazy to convert and write both units for every number above.

Thank you Generic Default for making sense out of what it would take to make a real flying car, I knew the one I found on Utube had to be CGI.
But wait, I just thought of something! They could use the anti-gravity generators that were found on the crashed UFO at Roswell and all the
numbers go out the window. If you believe that our government lied to us and they really did find a UFO and many more after Roswell.

SCREEEEEECH is the sound I make as I land in my nest to think all this out and the only conclusion is that this UFO crap is a figment of peoples
imagination!

Now I will settle down and use my fiber optics, my laser, my integrated circuits, my night vision goggles, my kevlar suit and my stealth tecnologies wings.
You all have a good one while I enjoy my mouse sandwich!

I like the concept and would love to see a flying car one day in mass, for those who have a pilots license.

Besides the power issues already discussed, I have two other issues the video failed to explain, well maybe only one. First is how to you enter and exit the vehicle for four people. I waited till the very end, hoping to see them open the front somehow but it didn't happen. From the design it would be pretty awkward as a car to get in and out stepping over seats to exit, I think it would be worse trying to get in. Second was the reason for the ducted fan for propulsion. They already have two rotary props. I assume they are both static and can not be rotated for directions but that would seem a better use of additional weight than another engine and the room is requires on the back.

Little more feasible,



[youtube]http://www.youtube.com/watch?v=0Yn2uyQJ1jc[/youtube]

Eaglezsoar wrote:Thank you Generic Default for making sense out of what it would take to make a real flying car, I knew the one I found on Utube had to be CGI.
But wait, I just thought of something! They could use the anti-gravity generators that were found on the crashed UFO at Roswell and all the
numbers go out the window. If you believe that our government lied to us and they really did find a UFO and many more after Roswell.

SCREEEEEECH is the sound I make as I land in my nest to think all this out and the only conclusion is that this UFO crap is a figment of peoples
imagination!

Now I will settle down and use my fiber optics, my laser, my integrated circuits, my night vision goggles, my kevlar suit and my stealth tecnologies wings.
You all have a good one while I enjoy my mouse sandwich!

Forgot to take your medication again today I see...

BenTheRighteous wrote:

Eaglezsoar wrote:Thank you Generic Default for making sense out of what it would take to make a real flying car, I knew the one I found on Utube had to be CGI.
But wait, I just thought of something! They could use the anti-gravity generators that were found on the crashed UFO at Roswell and all the
numbers go out the window. If you believe that our government lied to us and they really did find a UFO and many more after Roswell.

SCREEEEEECH is the sound I make as I land in my nest to think all this out and the only conclusion is that this UFO crap is a figment of peoples
imagination!

Now I will settle down and use my fiber optics, my laser, my integrated circuits, my night vision goggles, my kevlar suit and my stealth tecnologies wings.
You all have a good one while I enjoy my mouse sandwich!

Forgot to take your medication again today I see...

Thanks for the reminder, I am feeling better now!