Slashdot Mirror
NASA Unveils Plans For Electric-Powered Plane (techcrunch.com)
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.
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)
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.
"There are a dozen opinions on a matter until you know the truth. Then there is only one." - CS Lewis (paraprhase)
And meanwhile, in the real world, electric planes are a real thing, 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 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 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 is currently tooling up to market their E-Fan.
Monkeywrench Ex Machina.
The distributed motors are a feature, not a bug. With current designs, manufacturers can't go with more smaller engines due to efficiency losses. The engines installed on aircraft now are used to provide thrust and the resulting wind across the airfoil from that forward movement is what provides lift.
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.
Sig not found.
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 nonsensical propaganda: facing off against a military limited to actual pre-V2 tech, the Russian military would absolutely dominate.
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.
When all you have is a hammer, every problem starts to look like a thumb.
> 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/...
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 engines are cheaper and more efficient than 14 smaller ones. A bonus feature is that many "variable pitch propellors" can change pitch to *REVERSE* thrust. This is useful for backing up out of a hangar, as well as providing braking during landing on short airstrips.
I'm not repeating myself
I'm an X window user; I'm an ex-Windows user