NASA Unveils Plans For Electric-Powered Plane (techcrunch.com) 55
An anonymous reader quotes a report from New York Times: A new experimental airplane being built by NASA could help push electric-powered aviation from a technical curiosity and pipe dream into something that might become commercially viable for small aircraft. At a conference on Friday of the American Institute of Aeronautics and Astronautics in Washington, Charles F. Bolden Jr., the NASA administrator, announced plans for an all-electric airplane (Warning: source may be paywalled) designated as X-57 and nicknamed "Maxwell," part of the agency's efforts to make aviation more efficient and less of a polluter. "The X-57 will take the first giant step in opening a new era of aviation," Mr. Bolden declared. Maxwell is equipped with 14 electric propeller-turning motors located along the wings, which will all be used to create sufficient thrust during take-off and landing. Only two large motors on the tips of the wings will be used once it's up in the air. The plane is a result of NASA's "New Aviation Horizons" initiative: a 10-year program to create a new generation of X-planes that will make use of greener energy, use half as much fuel, and be half as loud as commercial aircraft in use today.
We've been over this (Score:2)
Re:We've been over this (Score:5, Informative)
The main problems are batteries, not electric propulsion itself. That batteries are far heavier that fuel on a lbs/kw basis, plus you don't get the bonus of the plane getting lighter the longer it flies. And high bypass turbines on planes aren't as inefficient in use as the ICE in cars (and planes are much more weight sensitive than cars) so you can't trade weight and drivetrain efficiency for useful range like you can in electric cars.
Also, for commercial planes they spend very little time on the ground between flights; so you don't have time to recharge batteries. So you're looking at a battery swap technology as well to keep the turnaround time comparable to refueling.
That said, if the distributed electric propulsion is as efficient as NASA thinks it might still be a net win even if you have to pair up the electric motor and prop placement of this X-57 with an onboard electric generator. In which case all the downsides of batteries are irrelevant. (Then you could look into whether a hybrid design with a some batteries and a smaller generator made sense)
Re:We've been over this (Score:4, Interesting)
And meanwhile, in the real world, electric planes are a real thing [google.com], actually rather popular in the light aircraft world, and a market that's growing by leaps and bounds every year. And actually have excellent performance vs. price [wired.com] figures compared to their ICE equivalents. Ranges are usually similar to those of electric cars, 150-400km.
Can we ditch with the old battery-energy-density-versus-fuel-energy-density canard, as if a gallon of petrol is an entire vehicle? Even the long-range versions of the Model S, the batteries are only a third of the vehicle weight. There are other parts to a vehicle. An electric motor the size of a roomba has the power output of an entire typical gasoline engine in a typical passenger car. And you can ditch the transmission and a lot of other hardware as well. And it's only logical that this size difference would be the case. Electric motors have vastly less heat to dissipate - heat dissipation means mass. Electric motors have vastly fewer parts; complexity equals mass. Electric motors create force directly applied as torque on a driveshaft linkage (or even directly on the wheel), while ICEs produce it as pressurized gas, change that to linear momentum, then change that to rotational. Obviously the latter is going to cost you signfiicantly in terms of mass.
This headline makes it sound like electric airplanes are new. They're not. They're not even in the one-off-prototype stage, there are a number of serial producers out there. The market is expected to be over 22 billion a year [marketsandmarkets.com] three years from now. I'm not sure I believe it's going to scale up that fast, but it most definitely is growing. It's not even just small manufacturers, even Airbus [avweb.com] is currently tooling up to market their E-Fan.
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Energy density [wikipedia.org] is not a parameter which can be waved away. Calling it a canard merely demonstrates that you are not content with reality. Ion engines are also wonderfully efficient, and similarly limited to small scale by the same energy density problems.
The most direct path to cleaning up air and surface transport is the use of synthetic fuels, efficiently produced with high-temperature nuclear heat. Nuclear power sources are also ideal for large ships and indispensable for any serious activity in space.
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And meanwhile, in the real world, electric planes are a real thing [google.com], actually rather popular in the light aircraft world, and a market that's growing by leaps and bounds every year. And actually have excellent performance vs. price [wired.com] figures compared to their ICE equivalents. Ranges are usually similar to those of electric cars, 150-400km.
Can we ditch with the old battery-energy-density-versus-fuel-energy-density canard, as if a gallon of petrol is an entire vehicle? Even the long-range versions of the Model S, the batteries are only a third of the vehicle weight. There are other parts to a vehicle. An electric motor the size of a roomba has the power output of an entire typical gasoline engine in a typical passenger car. And you can ditch the transmission and a lot of other hardware as well. And it's only logical that this size difference would be the case. Electric motors have vastly less heat to dissipate - heat dissipation means mass. Electric motors have vastly fewer parts; complexity equals mass. Electric motors create force directly applied as torque on a driveshaft linkage (or even directly on the wheel), while ICEs produce it as pressurized gas, change that to linear momentum, then change that to rotational. Obviously the latter is going to cost you signfiicantly in terms of mass.
This headline makes it sound like electric airplanes are new. They're not. They're not even in the one-off-prototype stage, there are a number of serial producers out there. The market is expected to be over 22 billion a year [marketsandmarkets.com] three years from now. I'm not sure I believe it's going to scale up that fast, but it most definitely is growing. It's not even just small manufacturers, even Airbus [avweb.com] is currently tooling up to market their E-Fan.
I'm sure we will have electric planes but they will almost certainly remain the domain of small aircraft. The car analogy works well. Electric cars make sense but electric 18-wheelers don't and probably never will. A radical and fundamental shift in how we move cargo and people is more likely to me than an electric A330.
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You this does not make sense: http://electrek.co/2016/06/13/nikola-motor-pre-orders-worth-2-billion-electric-truck/
Seems a lot of pre-orders says otherwise.
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So, to try and counter all electric 18 wheelers you trot out a hybrid electric powered by natural gas or diesel?
Re:We've been over this (Score:4, Insightful)
Power isn't the only problem with the concept. The wing loading is too high - that plane will glide like a rock if the motors quit. I also wonder about the turbulent flow over the wing from the prop wash, it seems far from the ideal lift/drag solution.
London to paris (Score:2)
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(London to paris)
In two days.
Depending on number of factors, that in itself may not be a bad thing.
Where I can see possibilities here is possibly as propulsion for fractional-buoyancy/buoyancy-compensated mass air cargo/passenger transport craft design using gas filled cells to lessen the demands for lift and thrust.
Some thing somewhere between a dirigible, a sea-going ship, and a passenger/cargo plane. Something that could take advantage of large scale economy savings combined with lower environmental impact. Imagine a large cargo o
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Lighter than air craft have a lot of problems. The energy use isn't as as low as you might imagine - there is no drag due to drift, but the large frontal area resulst in a lot of parasitic drag except at very low speeds. Winds, ice etc can be a serious problem, and they typically can't climb above weather.
one example at http://www.zeppelinflug.de/en/ [zeppelinflug.de]
carries 16 people, 80mph, 600hp total engines, range 600 miles (they don't give detailed specs).
Compare with a 1960s beechcraft baron:
6 people, 230mph, 600HP
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Lighter than air craft have a lot of problems. The energy use isn't as as low as you might imagine - there is no drag due to drift, but the large frontal area resulst in a lot of parasitic drag except at very low speeds. Winds, ice etc can be a serious problem, and they typically can't climb above weather.
one example at http://www.zeppelinflug.de/en/ [zeppelinflug.de]
carries 16 people, 80mph, 600hp total engines, range 600 miles (they don't give detailed specs).
Compare with a 1960s beechcraft baron:
6 people, 230mph, 600HP total engines, range ~800miles
person miles / gallon seems to be in the same ballpark. The airship may be a lot more pleasant to fly in, but its isn't substantially more efficient .
Wasn't talking about lighter-than-air craft. What I'm talking about nobody has built an analog of yet that I'm aware of.
Basically a giant electric powered airliner/cargo plane/lifting body that is capable of landing/taking off from land or sea which has *some* of the lift requirements met by adjustable/controllable gas cells located inside the craft. I'm talking on the scale of one of the giant container ships or "supertanker" oil ships, maybe even much larger. I'm thinking something that uses a combination
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Ground effect planes are interesting. The Russians did a lot with those. https://en.wikipedia.org/wiki/... [wikipedia.org]
I think the biggest problem is that the low altitude environment is pretty hostile - waves, birds, floating obstructions etc. In principal though they are more efficient than airplanes.
My comment really was that using buoyancy lift seems like it should provide a major fuel savings, but in practice (I've looked at other examples as well) it doesn't seem to make a lot of difference to the overall efficie
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I think the biggest problem is that the low altitude environment is pretty hostile - waves, birds, floating obstructions etc. In principal though they are more efficient than airplanes.
That, and the high air density at sea level requires a lower cruising speed to be efficient. The military, who funds much of the world's aerospace research, values speed more than efficiency. (They are only interested in efficiency mostly because it limits range, which is also important to them.)
Jets are actually less efficient, but the lighter weight more than makes up for that.
"Efficient" is a meaningless term, unless one specifies which two metrics are being compared.
Jet engines generally have considerably better thermodynamic efficiency than piston engines: they convert a larger percent
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Its interesting (surprising) that turbine engines are actually a bit less efficient than most piston engines. See: https://en.wikipedia.org/wiki/... [wikipedia.org] Note that the 1996 turboprop engine is less efficient than the simlar size and application piston engine. The turbine engine is much lighter so the overall aircraft efficiency is better. Similarly the diesel ship engines are more efficient that turbine ship engines of similar sizes.
In turbines the maximum combustion temperature has to be within the operat
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Your analysis assumes that the purpose of an airplane engine is to produce shaft power (the subject of the Wiki article you linked). This is incorrect, especially for jets (which ought not to be confused with turboprops).
The true purpose of an airplane engine is to add kinetic energy to the airplane. The effectiveness of jets at this task relative to piston-driven propellers is far higher than your shaft-power based comparison would suggest.
First, because jets (unlike turboprops) are intended to derive a s
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For subsonic planes like airlines, the "jet" engines are high bypass and the majority of the thrust comes from the ducted fan . Ducted fans behave like propellers, the ducts improve efficiency at near sonic speeds, but otherwise there is not much difference. There is a little thrust from the jet exhaust, but that is low efficiency because its velocity is so much higher than the aircraft efficiency.
If you looked at the ISP of a prop plane it would be very high since the reaction mass is moving slowly. Thi
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If you have an external medium to move (air), you want a low exhaust velocity (about the same as the aircraft speed).
You seem to have skipped the most important parts of my posts. Even a jet that burns more fuel per unit thrust, can still be more efficient at actually moving the airplane from origin to destination, because the higher top speed means that it doesn't need to sustain that thrust as long to complete the journey.
There is a little thrust from the jet exhaust, but that is low efficiency because its velocity is so much higher than the aircraft efficiency.
Subsonic turbofans typically have a bypass ratio somewhere between [5:1] and [10:1]. Taking into account the mass of the fuel being mixed into the core air stream, this means that you are ignoring betw
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with a significant percentage of the need for lift and thrust cancelled by positive-buoyancy gas cells,
As has already been pointed out, buoyancy cells reduce the need for lift, but increase the need for thrust at a given speed. The square-cube law favours larger airships for lower drag.
most or all of the electricity coming from photo-voltaic cells covering the upper hull/fuselage and lifting/control surfaces.
The power that can be collected via solar cells scales with surface area, but the power required scales with mass (and therefore volume). Thus, the square-cube law also favours smaller airships for greater power-to-weight, if solar power is the primary energy source.
lifting-body design and surface-effect-cushion aerodynamics at just a few meters altitude above the sea, possibly, rather than lifting to a multiple-kilometers altitude?
The volume of buoyancy cell required to lift a given mass inc
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Of course, in reality, small electric aircraft tend to perform better than their ICE counterparts. Power density comes much cheaper (in terms of mass, volume, and money) with electric drive than it does with internal combustion. It's energy density that electrics perform worse in.
Some small electric aircraft have pretty crazy performance specs for surprisingly little money. Of course, if you've seen high performance drones designed for pulling tricks, you wouldn't find this surprising; you could never ge
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Indeed, research is a bit part of what NASA does - and IMHO, it should be bigger. I agree with Buzz Aldrin that NASA should revert to the earlier NACA model [arstechnica.com].
Maxwell is a micro-aggressive name (Score:1)
going the way of manned space travel? (Score:1)
let us hope nasa will waste lost of money trying out all the inefficient ways of making electric planes.
then hopefully russians will create cheap and effective electric planes that everyone (even the usa military ) can borrow, as they do with human space travel (again even usa military use russian rockets now ) .
meanwhile eion musk will blow lots of hype trying get his cronies in usa government to give him money to make electric planes too(especially ones that fly on social media to give his fanboys much ne
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The Russians are't going to do shit. They have nothing like technology to do this - the Chinese are far more likely and are closer. The Russians plod on with steam-era rockets, which are practical but are a fallback to pre-V2-technoliogy. They aren't advancing any states of any arts.
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In fact, there already are Chinese manufacturers of electric planes, like Yuneec [google.com].
As for Musk, he doesn't just want to make an electric airplane, he wants to make the first electric airplane to break the sound barrier. Ho-hum, I wish that guy would decide to try something ambitious for once ;)
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Musk, not being an engineer or scientist of any sort, is probably used to people telling him things are impossible. Most of the time, engineers in the current day tend to immediately jump to "impossible" based on their experiences trying to make something of fix something simple due to crushing bureaucracy that they assume everything is impossible. When someone tells a management type something is impossible, they just don't believe the engineer any more, because the engineers are usually overstating the di
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Building a supersonic electric airplane is certainly ambitious, but far from impossible.
On the other hand, building a practical and economically useful supersonic electric airplane with current technology is impossible. Hydrocarbon-powered supersonic planes still run out of fuel quickly, even after hundreds of billions of dollars of investment in the concept. A battery-powered model will certainly not have useful endurance.
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The Russians plod on with steam-era rockets, which are practical but are a fallback to pre-V2-technoliogy.
That's a pretty ridiculous and insulting exaggeration.
Up until SpaceX announced the Merlin 1C less than a decade ago, Russia was the unquestioned leader in Kerosene-Oxygen engine technology. There's a good reason that United Launch Alliance selected the Russian RD-180 for the Atlas V. More generally, Russian technology is competitive with (I do not say equal to) that of the West in many areas, such as rocketry, jet engines, airframes, avionics, weaponry, etc.
Dismissing all of that as "pre-V2 technology" is
Controversal design , 12 engines deadweight +drag (Score:1)
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You're forgetting that with the extra props across the wing, you need a much much smaller wing, and can have a wing with much higher aspect ratio*. The reduction in wing area and increased aspect ratio more than offsets any drag from the multiple (folded) props during cruise.
*Those props aren't there for thrust, they are for increasing flow velocity over the wings.
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RTFA. Max speed is 175KT, not exactly "high speed". NASA also admits this won't be viable for commercial service, basically a hobbyist plan for short flights with very little payload.
Bottom line though is that NASA is and has always been a PR machine. An all electric plane is a warm fuzzy story for people to read.
Howsabout variable pitch propellors??? (Score:3)
> GP also ignorantly fails to understand that props efficient in
> high speed flight are inefficient at low airspeed and vice versa,
> so stowing climb props is a very good choice for an electric airplane.
Howsabout variable pitch propellors??? They've been around since the 1920's, and have been in practical use since the 1930's https://en.wikipedia.org/wiki/... [wikipedia.org]
Rev up 2 or 4 engines (admittedly a bit inefficient) for takeoff, and then back off to more efficient speed for cruising. 2 or 4 larger engine
So many motors??? (Score:2)
So they have 12 extra motors/props just for takeoff, that add both weight and drag? Why don't they just use one motor and drive one of the wheels against the ground?
Re: (Score:2, Troll)
First off, airplanes putting electric motors in their landing gear is becoming a mainstream thing, it's a major fuel saving mechanism being employed by major manufacturers.
Secondly as has been pointed out in many comments above, there are numerous reasons for the approach, as it lets you increase air velocity across the wing (giving better wing performance) and use props more performance-optimized to their current flight environment.
Third, unlike ICE engines (the reason that this was impractical before), el
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Re:Illutrates the flaw in electric vehicles (Score:5, Insightful)
This design is different because the smaller motors have higher efficiencies and are able to direct air over the airfoil directly instead of relying solely on forward thrust to provide the same wind. That adds to lift, which reduces takeoff distance, which reduces friction losses from the wheels.
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Lots of tradeoffs. Airflow over the wings helps takeoff performance, but the disrupted airflow from the props in cruise is likely top reduce efficiency. Generally for low speed aircraft you want as few total propeller blades as you can use in order to reduce the losses from blade tip vortices. (practical effects like prop diameter will often force you to more props and more blades).
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But then again it is an X plane. That is why you build them, to see how good or bad the ideas are in the real world.
Not a hybrid and not for everyone (Score:2)
Interesting I would guess pure electric aircraft make up the majority if you include hobby quadcopters in that definition. I mention that as I think the takeaway from the article is that electric aircraft are practical in some niche areas and NASA's work w