NASA charges up 18-prop electric X-plane NASA is working towards getting an electric-powered multiprop experimental aircraft off the ground, with an eye to future "greater fuel efficiency, improved performance and ride quality and aircraft noise reduction". The Sceptor (Scalable Convergent Electric Propulsion Technology and Operations Research) project will …
I find it difficult to believe that a gazillion of propellers do not create a hell of a drag.
Granted, you can play with the boundary layer around the wing this way which you can do only to a very limited extent with a normal prop, but still... this looks like a contraption from a Studio Gibli flick
"Tests so far show the distribution of power among the 18 motors creates more than double the lift at lower speeds than traditional systems."
Shouldn't that be expected since essentially the entire wing now experiences a higher airflow over the wing due to it being almost entirely in the propwash?
I look forward to the results of this research as I expect the asynchronous thrust across the wing to produce interesting data.
"To put that in perspective, 500 kilowatts (nearly 700 horsepower) is about five times as powerful as an average modern passenger car engine."
Actually better than 15 times more powerful, based on your average 1-litre 30 kW engine. Of course these are American engines they're talking about, but even so 140 hp is one heck of a motor. You could put it in a light aircraft.
I think it's a reasonable comparison. A good modern family car has at least 100kW.
A 1 litre 30kW car is a low-end vehicle for teenagers, pensioners and people who can't afford to run a proper car. It's a thoroughly miserable driving experience that struggles to pull its own weight up any kind of hill in any gear.
140hp maybe have been considered "one heck of a motor" back in 1982. But a normal 1.6 or 1.8 litre hatchback will do that nowadays. My wife picks the kids up from school in an ordinary family estate car with 240hp.
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So the definition of "average modern passenger car" obviously depends on which country you're in when you ask the question. But the "modern" part excludes a lot of old and hilariously underpowered junk.
However, if you ask an Average Australian what an Average Car is, they'll rightly say "Toyota Corolla" (Auris to you Europeans), which here has 103kW.
QED!
(They might say Holden Commodore though, which starts at 185kW, but let's forget about that one.)
Also, no modern naturally aspirated 1L engine should have much less than 75kW.
? "Toyota Corolla" (Auris to you Europeans)
Wot? What is this Europe that you speak of? Autotrader is full of Corollas, but I've never heard of an Auris. However, I see that Autotrader is also full of Aurises. I conclude that an Auris is not a Corolla. Disclosure: I'm in the UK, which has been part of Europe since time immoral.
@x7 "as far as I'm aware, most Corollas are built at Sunderland"
I'm looking hard at this trying to get the joke, but it's flying over my head I think.
Are you saying Toyota Corollas are built at a Nissan Factory ? Or is there a hidden joke?
Toyota UK manufacturing is Burnaston, Derbyshire for cars, and North Wales for engines.
? "Toyota Corolla" (Auris to you Europeans)
"Wot? What is this Europe that you speak of? Autotrader is full of Corollas, ..."
I'm sure he made a mistake, it's not a Corolla, but a "creamed-over". Lil'l things like that, like a stone in your tyre ,a "Fit", "Smart", or a "Leaf" make that unforgettable sound.. tick.. tick.. tick.. thunk, when it finally flies out...
(still drivin' the '91 Cheby 3500 4x4 w/5.7l [350 c.i.] {with MAYBE 20 BHP, down hill, with a tail wind} gas guzzlin, oil eatin, grease drippin, anit-freeze spewing, brake-line leakin', pay-check robbin, winter-beater, POS...[can't find ONE panel that's not rotted out])
Hydrogen is a stupid chemical fuel, but at least it is chemical.
Lithium batteries have a 60:1 energy density problem compared to chemical fuels. Even with the relatively high efficiency of electric motors you are left with a worse than 10:1 problem (you use more fuel to carry more fuel).
Electric planes will have less than 1/10th the range or carry more than 10 times more fuel. Being mostly charged with coal they are not green and unlikely to be for years. All round stupid.
"this plane could be powered by a compact reactor."
Or it could be charged by a much bigger reactors driving a Haber process that makes synfuels.
Making a compact nuclear reactor was always easy. The hard part in aircraft has always been making radiation shielding effective enough to keep the meatsacks alive whilst light enough to allow the aircraft to actually leave the ground.
the russkies did actually have a bomber flying with a nuclear power plant fitted as a trial installation, though I don't believe it powered the aircraft
As you say, shielding was an issue, as also apparently was premature fatigue of the airframe structure due to the irradiation
"Being mostly charged with coal they are not green .."
Totally agree with you, BUT, the US uses mostly "Black Gold" to run the spinning parts in electrical generation. The other part of "mostly" is natural gas, and hydro (Niagara, Hoover)
"Lithium batteries have a 60:1 energy density problem compared to chemical fuels. Even with the relatively high efficiency of electric motors you are left with a worse than 10:1 problem (you use more fuel to carry more fuel)."
Maybe it needs to be a multi stage aircraft? Have a bigger "lifter" to get the whole lot into the air, then the smaller part can separate off and do the actual flying and landing part. NASA have form with this type of design. They might want to have a word with Elon Musk about getting the 1st "lifter" section back on the ground in a way that it can be re-used again though.
NOTE: See icon. I'm not being serious. I know about White Knight, modified 747s carrying shuttles, B52's carrying/launching rocket "X" planes and even biplanes launching from airships.
" but even so 140 hp is one heck of a motor."
I'd imagine it's about high-ish average-ish even in the UK . But more to the point where are they going to get 500 kW of battery power that will get them a reasonable range as well. It's about 5/6 Tesla batteries at ~500kg each for about 1 hrs duration flight ( I know doubtless cruise will be much lower consumption )
I think it depends on the motor. A 750cc sports bike engine producing 140hp is definitely one heck of a motor, but you probably wouldn't put that motor in a car. Could make fun out of a kei or supermini though.
But a 140hp motor in a normal car built in the last 30 years is not likely to be one heck of a motor.
Blowing against your own sail does actually work if it's done right. The comic interpretation is to blow directly into the sail in an attempt to derive force from drag alone which obviously doesn't work. What does work is if the sail is angled and treated like an airfoil which provides force, effectively lift, in a direction largely orthogonal to the prevailing wind. Of course some of the wind has to actually fill the sail so it forms an airfoil but the principle is the same. It actually works a treat on wingsails of the type used in the America's Cup.
Most of what I've seen talks about actual use of this is in a hybrid configuration. Use batteries to power the motors for takeoff, then switch to conventional turbofans for cruise at which time they can also recharge the batteries.
Or use both electric motors and turbofans for takeoff. That allows the turbofans to be optimized for cruise without the high-power requirements that takeoffs currently require. The idea being improved fuel burn and less noise.
And probably coming to commuter planes a long time before you see an electric A-380.
1) An asynchronous motor is a specific type of induction motor, nothing to do with them being independent.
See
http://machinedesign.com/motorsdrives/whats-difference-between-asynchronous-and-synchronous-motors
and
http://www.groschopp.com/synchronous-vs-asynchronous/
Quite common on railway locomotives. Its basic technology that a tech journal should be aware of.
2) With that number of props, I'm surprised there's enough clean air going over the wing to generate lift. I really would have expected the airflow to be too turbulent to be any use
LEAPTech:
"In this design, eighteen electric motors are mounted in nacelles regularly spaced spanwise along the wing leading edge and drive propellers that increase the dynamic pressure over the wing during takeoff and landing. The propellers spin at relatively low tip speeds to minimize noise. Propulsion in cruise flight is outside the scope of this analysis, but is intended to be fulfilled by a combination of some of these propellers, separate propellers mounted on the wingtips to take advantage of the wingtip vortex, and/or a separate propeller mounted on the tail boom to take advantage of the fuselage boundary layer. Any of the leading edge-mounted propellers not required for cruise propulsion fold at against the respective nacelles to minimize drag."
...
"One distributed electric propulsion (DEP) configuration that shows great potential is named Leading Edge Asynchronous Propellers Technology (LEAPTech) and features many small propellers distributed spanwise along the wing that blow the wing during takeoff and landing. This increases the dynamic pressure over the wing, facilitating lower stall speeds and/or reduced wing area without the need for structurally complex traditional multi-element high-lift systems. If the stall speed requirements are retained, a significantly smaller wing may be employed, because the wing is typically sized to meet takeoff and landing constraints. This smaller wing can result in a large reduction in cruise drag as well as substantially improved ride quality due to decreased gust sensitivity."
Aviation Technology, Integration, and Operations Conference, 16-20 June 2014, Atlanta, Georgia
"Drag Reduction Through Distributed Electric Propulsion"
See: http://www.jobyaviation.com/LEAPTech%28AIAA%29.pdf
Me too... weirder things have cruised the skies:
http://www.aviation-history.com/articles/nuke-american.htm
http://www.scientificamerican.com/article/nuclear-powered-aircraft/
or may be someday:
http://www.businessinsider.com/boeing-just-patented-a-jet-engine-powered-by-lasers-and-nuclear-explosions-2015-7?IR=T
It reminds me of the old pilot joke about how many engines a plane should have. The captain says well if there is an engine failure, I want the co-pilot to tell me that it was engine number 9, and then I'll ask is it number 9 on the left or right wing?
Still not keen on flying anything batter powered though.
"And, that reminds me of something" - with the prospect of using leftover batter, to fuel flying machines, for the high-tech Orstrarlean space programme, there is the special, northcoreen high density rocket fuel - "the intergalactic laxative will get you from here to Mars"...
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