5 ms·
Anyone have a sense of how the energy needed to fly something like this compares to driving an electric car the same distance?
by caditinpiscinam 3y ago
Anyone have a sense of how the energy needed to fly something like this compares to driving an electric car the same distance?
- charlieyu1 3y agoWe would have hover cars like we predicted decades ago if it is energy expensive. Lifting a vehicle and passengers is always costly in energy.
- zdragnar 3y agoIt is really a basic physics question, no? Air has little mass, and so provides poor thrust under Newton's third law of motion compared to a tire on the earth. A car on the ground will always be more efficient than something which dumps its energy into air.
- bombcar 3y agoA small plane can carry 1-4 people at 120 MPH consuming about 11 gallons an hour, for a "MPG" of about 11 (miles in the air don't exactly translate to ground because air flows but it evens out over time). Even with modern efficiencies available, I doubt they'd do more than double that, so a car would still easily win, unless the car had one person in it and the plane 4.
- amelius 3y agoTime to resurrect the zeppelin, of course with better safety measures.
- bragr 3y agoAirships never really went away, but "hydrogen go bang" is hardly their only problem sadly.
- someweirdperson 3y agoHydrogen doesn't "go bang" unless mixed with the proper amount of oxygen. Usually, it just burns nice and smooth. Not much of a difference for anyone riding the airship though.
- barelyauser 3y ago>>Usually, it just burns nice Great choice of words to calm the passengers as we lose all our air worthiness.
- merth 3y agowouldn't you recover the energy back while landing in same sense with car breaks that recharges the battery
- Ekaros 3y agoThere is constant energy expenditure to stay in air. Unlike with ground or sea vehicles that don't need it.
- bbojan 3y agoYes, the technical term for that is "lift induced drag".
- barelyauser 3y agoNo, it's just drag. Extended landing gear is also a constantly expenditure but generates no lift.
- JumpCrisscross 3y ago> Extended landing gear is also a constantly expenditure but generates no lift Negligible lift. Fluid flowing around an object generates lift. Drag is more intuitive; if there is drag, there is lift. (They're just components of the aerodynamic force relative to the direction of relative fluid flow.)
- TechBro8615 3y agoThat's about the MPG of a hummer, so it's at least the same order of magnitude of cars.
- dghughes 3y agoCars can't cross over lakes and mountains so there are advantages to having an airplane inefficient or not.
- upofadown 3y agoA Long-EZ carries 2 people and goes 1600 miles on 52 gallons of gas. So 31 MPG. That's at a cruise of 144 MPH. So more like 3 times better performance is available with a modern design... Kind of makes you wonder... https://en.wikipedia.org/wiki/Rutan_Long-EZ https://en.wikipedia.org/wiki/Rutan_Long-EZ
- adrianN 3y agoI'd assume that for very short trips lift off and landing consume a large fraction of the total fuel.
- t0mas88 3y agoNot for a typical small plane. Takeoff fuel burn isn't that much higher than cruise, and descend and approach fuel burn is similarly lower due to reduced power.
- bombcar 3y agoThere are people who hypermile on planes and they have all sorts of tricks, including using updrafts when possible. The most extreme ones fly without an engine at all (gliders).
- adrianN 3y agoI doubt that those techniques work very well in areas where you'd be able to run a successful air-taxi business.
- t0mas88 3y agoThe wind component averages out over time or is slightly in favor of the aircraft because you would aim for optimal wind by selecting a preferred altitude. But air miles and car miles are not equal. The car route is nearly always longer, even in flat terrain roads don't usually go in a straight line to the destination. Adding in mountains or water makes that worse for the car. For example driving Amsterdam to Barcelona is 1554km according to Google Maps. The flightplan route is 1236km and usually the really flown route is a bit shorter if ATC allows. That's 20% less miles for the airplane.
- palata 3y agoI think (not an expert though) that a multicopter like this is fundamentally less efficient than a helicopter. It has to do with the surface of the rotary wing (many small props cover less surface than a single big one). I know that's not answering the question about the car (btw electric or not doesn't fundamentally change the energy question, except that electric cars like Tesla tend to be heavy, I would say), but still I find it interesting.
- marcosdumay 3y ago> many small props cover less surface than a single big one Well, things change when you make a lot of small props. This one has an entire ring of them, and they fit a larger outer diameter than a helicopter would. That's quite possibly the reason they are quiet, because they have more propeller area, operating on a smaller speed. Very likely, here the amount of noise is a better guideline for efficiency than the usual characteristics of the basic design. (There is no mention of the cost. It is the first thing to suffer when increasing the propeller area.) Anyway, about the car question, the article says it is as noisy as a small grass mower... I guess an electrical car is much more silent than this.
- presentation 3y agoA friend working on this type of technology mentions that altering the frequency at which sound is emitted to those outside the human hearing range can make a big difference.
- crubier 3y agoOne small propeller is less efficient than one big propeller. What drives the efficiency really is the ratio of propeller surface area to mass. So a lot of small propellers are roughly as efficient as a big one. Actually bonus point for the propellers being twisted, which is not possible on helicopters.
- mabbo 3y agoThere are videos online of a cyclist pedaling a craft with enough energy to lift off the ground. Mind you, it was a purpose built craft in a very staged environment with an Olympic level cyclist, but you can still use that as a baseline for how much energy you need to lift a human aloft.