Boeing-Backed, Hybrid-Electric Commuter Plane To Hit Market In 2022 (reuters.com) 55
An anonymous reader quotes a report from Reuters: A Seattle-area startup, backed by the venture capital arms of Boeing and JetBlue announced plans on Thursday to bring a small hybrid-electric commuter aircraft to market by 2022. The small airliner is the first of several planes planned by Zunum Aero, which said it would seat up to 12 passengers and be powered by two electric motors, dramatically reducing the travel time and cost of trips under 1,000 miles (1,600 km). Zunum's plans and timetable underscore a rush to develop small electric aircraft based on rapidly evolving battery technology and artificial intelligence systems that avoid obstacles on a road or in the sky. In a separate but related development, Boeing said on Thursday it plans to acquire a company that specializes in electric and autonomous flight to help its own efforts to develop such aircraft. Zunum's planes would fly from thousands of small airports around big cities to cut regional travel times and costs.
Drone Technology (Score:2)
I haven't seen any good information on why drone technology can't simply be scaled up in size to carry passengers. Seems like we already have the technology to solve traffic and other problems. We just need to supersize it.
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Re: Drone Technology (Score:1)
Yeah, it's just that simple. Just make big drones. Since it's that simple, that's probably why we've seen so many companies do it already.
Man! After 20 years the quality of the commenters here at /. really has dropped off. Is there anyone else here who actually works in any sort of a technological industry?! Sometimes I think not!
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Yeah, it's just that simple. Just make big drones. Since it's that simple, that's probably why we've seen so many companies do it already.
Man! After 20 years the quality of the commenters here at /. really has dropped off. Is there anyone else here who actually works in any sort of a technological industry?! Sometimes I think not!
Moron. I didn't say it was simple. I asked for information on why it wasn't simple.
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I haven't seen any good information on why drone technology can't simply be scaled up in size to carry passengers. Seems like we already have the technology to solve traffic and other problems. We just need to supersize it.
Copter style flight requires much more energy than winged flight.
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I haven't seen any good information on why drone technology can't simply be scaled up in size to carry passengers. Seems like we already have the technology to solve traffic and other problems. We just need to supersize it.
Copter style flight requires much more energy than winged flight.
Which is why all of the long-range, long-endurance unmanned aircraft look like traditional winged aircraft rather than helicopters or quads. "Drone" does not mean "copter style".
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"Drone" does not mean "copter style".
True, but I think that is what the OP had in mind when he talked about 'scaling up'. Aircraft type drones are typically not VTOL, but Amazon was looking at a copter/wing hybrid for package delivery.
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If you mean multi-rotor aircraft without wings: It's because they need to accelerate upwards with one g all the time just to not drop out of the sky. This is cool for being able to whip around at will, but very bad for efficiency.
But yes, you could possibly build a kind of hybrid helicopter this way. Generate power with a gasoline powered motor and use it to power some electric rotors. You'd trade some efficiency losses against more control and maybe more reliability, especially if you use two redundant mot
Props don't scale because they are one-dimensional (Score:4, Informative)
Quadcopter don't scale. I assume that's what you meant - virtually all of the toy and hobby "drones" are quadcopters.
The power produced by a propeller is proportional to it's length.
The weight of a craft, however, is proportional to it's length X width X height.
Suppose we have a toy that's 1 foot X 1 X 1. It's one cubic foot. Perhaps it weighs one pound. The 1 foot prop needs to make 1 pound of thrust.
Now we scale that "ten times bigger". Now the dimensions are 10x10x10. That's 1,000 cubic feet! "Ten times the size" is about a THOUSAND times the weight. But our prop is only ten times as long, so it makes ten times the thrust, enough to lift TEN pounds, not a thousand pounds.
In other words, as the size of craft increases, weight increases with roughly the size (length) CUBED. Prop thrust only increases directly proportional to size (length).
It's therefore therefore relatively easy to lift a small craft with props, but the power requirements go up real fast as the size increases, until you basically hit a wall of impossible physics. The largest helicopters that can be physically built carry about 40 people, whereas an A380 plane seats 853 people.
Re:Props don't scale because they are one-dimensio (Score:4, Informative)
For an actuator disk of area A, with induced velocity v at the rotor disk, and with p as the density of air, the mass flow rate m through the disk area is:
m =pAv
By conservation of mass, the mass flow rate is constant across the slipstream both upstream and downstream of the disk (regardless of velocity). Since the flow far upstream of a helicopter in a level hover is at rest, the starting velocity, momentum, and energy are zero. If the homogeneous slipstream far downstream of the disk has velocity w, by conservation of momentum the total thrust T developed over the disk is equal to the rate of change of momentum, which given zero starting velocity is:
T=mw
Because tip velocity can't exceed c, w is limited to far below the transonic regime. Therefore w can't be increased beyond an easily achievable value. Meaning thrust T is limited to a (roughly) constant factor times m, mass air flow. Recall mass air flow is pAv. p, air density, we can't change. v is limited to far subsonic, so we can increase thrust T only proportionally to A, the area of the rotor disk. By middle school geometry the area of the disc is pi 2 r. Pi and 2 being constants, the area, and therefore the thrust are directly proportional to r, the radius (the length of the rotor blade),
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By middle school geometry the area of the disc is pi 2 r.
Shouldn't that be pi*r^2? So that your ten-foot drone would make 100 pounds of thrust, rather than 10? Of course. since 100 1000, your point still somewhat stands.
Yes, of course. Kinda. Explains why a single prop (Score:5, Informative)
Yes, of course you're right. It's the AREA of the disk, multiplied by the velocity, which determines how much air is moved at what rate, which equals how much thrust is created (Newton's third law). I typed it as circumference rather than area.
What I didn't go into was a consideration with real props which brings it closer to directly proportional, so the actual real-life performance is in between the area and the circumference. The inner part of the blade is of course moving slower than the tips, in terms of linear speed. In other words, if the rotor tips are moving through the air at 400MPH, halfway toward the hub it's only slicing through the air at 200MPH. So the portion of the rotor which is delivering maximum power is at the ends, measured by the circumference.
Does that make sense? The total area is proportional to r^2, but the area of blade working at full speed is proportional to just r. Meaning the total thrust is between X * r and X * r^2.
Your correction points out why large rotorcraft normally use one lifting rotor rather than multiple as hobby craft often do. A single 40 foot rotor has twice the swept area of the two 20-foot rotors which would fit on the same airframe. Of course, when you need rotor too big to build and affix to the airframe, such as a heavy-lift copter, you may end up with tandem rotors simply because a 120' rotor is Impractical.
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Also, I'm not sure about your reasoning on thrust being nearly proportional to blade length. At any given tip speed, the proportion of any blade length running within any given range of speed is the same no matter what size the rotor, and the maximum tip speed is fixed regardless of the size. In addition, the longer the blades (for a given amount of lift), the more efficient they are.
There are trade-offs am
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> Also, I'm not sure about your reasoning on thrust being nearly proportional to blade length.
By Newton's third law, thrust is equal to the force applied to the air moved through the rotor disc. That's the area of the rotor disc times the average acceleration of the air (average velocity change). There are two terms there, disc area and AVERAGE Delta V of the air.
The disc area is proportional to the square of the rotor radius. On the other hand, the portion of the rotor near the hub has nearly zero l
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Helicopters have an advancing blade (Score:2)
For fixed-wing craft (airplanes) blade tips CAN as you say, go supersonic, though that's quite rare because there is an enormous increase in drag at transonic speeds. Helicopters not only have the large increase in drag to worry about, but also in forward flight one wing is moving forward while the other wing in moving backward.
Consider the world's fastest military helicopter, the Chinook, flying forward at 315km/h. If the blade tip were moving at 1,000 km/h relative to the fuselage, the advancing blade wo
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I suppose you might be referring to the SureFly [flyer.co.uk], which is a hybrid. This looks fairly promising at the spec level given that it does not seem to rely an a new generation of battery technology.
Actually I think its biggest problem will be cabin noise. So many of these concepts never get off the ground for seemingly trivial reasons, so to speak.
Agree that autonomous drones are a natural play (Score:2)
So many problems are solved by working in three dimensions. And moving up off the ground -- where dogs, children, pedestrians, sheep and every other thing you can think of lives or stands to impede and surprise -- makes many problems trivial. Line of sight to talk with other vehicles is also a bonus. I see far fewer problems to solve with an airborne autonomy than with ground based autonomy. Although other problems do materialize, of course.
Much air travel is already autonomous truth be known. But such a c
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I haven't seen any good information on why drone technology can't simply be scaled up in size to carry passengers. Seems like we already have the technology to solve traffic and other problems. We just need to supersize it.
Then consider this:
Quadcopters are controlled by varying the speed of their individual rotors. That is all fine as long as the rotors stay small. If they are scaled up, their moment of inertia scales with the fifth power of the dimensional change. The time-to-double of an instability, however, would only scale with the square root of the dimensional change. Result: You will need massively more torque to keep the thing under control.
No, there is hard evidence why scaling up will not work. You were just t
Re:How will that impact fuel requirements? (Score:5, Informative)
I've read about how planes are required to have certain amounts of fuel at certain points relative to their trip.
You need to have 100 or 200 nmi of fuel left once you reach for destination to divert if necessary. Depends on the Part and certificate under which you operate.
More to my point I have heard that this is why planes often have to dump unused jet fuel (usually conveniently done over less-desirable neighborhoods near the airport) before landing.
Planes have to have a provision to reduce weight if the plane must land before the destination. Generally, if the maximum takeoff weight (MTOW) is greater than 105% of the maximum landing weight (MLW), there will be a fuel dump option. It is not used often, only during an abnormality or declared emergency, if the type is so equipped. Otherwise, the plane will circle, if practical, to burn fuel to reduce weight for landing. If that isn't possible, an overweight landing will happen with the air frame taken out of service for a D-level inspection.
If your fuel instead is primarily batteries, how will that change these regulations?
The air frame will be designed such that MTOW = MLW. This isn't an unusual design criterion at all.
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batteries get heavier as they discharge...
Instinctively this just sounds wrong.
I mean seriously wrong!
Even if electrons had negative mass, and were actually 'used up' in providing power, I'd still think something were wrong...
Can someone help me out here?
..."eventually be remotely piloted"... (Score:2)
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no one on board to prevent passenger problems?
The article said "remotely piloted", not "no flight attendant".
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I haven't flown on such flights myself but I've heard stories of people getting on planes and being greeted by a person they assume to be the flight attendant. This person will show them to their seats, give them their safety briefing, perhaps even hand out drinks and snacks, and then go to the flight deck and help fly the plane.
I don't know exactly what size of a plane would have only a crew of two, 40 or fewer perhaps. In those cases the flight attendant is the co-pilot. If there's something like 20 or
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Crew cost isn't the only factor, but commercial pilots make a lot more money than flight attendants even though they aren't as highly paid as they used to be. average commercial pilot salary [salary.com] is about $129K, with a range usually between $112K-$146K. Average flight attendant salary [salary.com] is about $72K, with a range usually between $58K-$89K. As the AC pointed out in his reply, the cost and added weight of a cockpit in a remotely-piloted aircraft is a much larger factor.
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Some ultralights and electric hang gliders can recover energy on descent. For example the Icaro [icaro2000.com] is similar to designs that do this. (I haven't flown one myself.)
Theoretically you can take off on a full charge to climb into soaring conditions, turn off the motor, windmill the prop, and recharge by basically capturing the energy gained in the lift of thermals. (i.e. solar energy). Then glide to the LZ and end up with a full charge.
I can't wait to try one.
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I watched the great video and was disappointed that their prices link is broken. It uses a folding prop so I don't see how it could recover energy, and anyway a powered hang glider isn't going to need to increase drag to descend.
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The models that do energy recovery have an option to fold the prop or not.
And yes most hang gliders don't really need more drag. Most pilots would rather fly longer and just recharge the battery on the ground. It isn't like it is very expensive.
There are conditions where you can get really high and you're tired and just want to get down. A speed brake would be useful then.
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It does bother me that the wing and keel are in the plane of the prop. If it sheds a blade, how much of a wing will you be left with?
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Surely energy density is still a problem (Score:1)
I could see fuel cells working. Or electric generation. Nothing wrong with electric motors. Batteries seem like a dead end though.
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The problem with heat engines for short hops is damage to engines caused by the thermal cycling. Its worst for glider tugs which are on full power for a few minutes, then nothing at all, but it does affect short distance commuter aircraft as well. This is why electric drivelines are being considered for short distance commuting, and why a gas turbine APU makes sense on these aircraft because it will be used to extend cruise.
I can imagine heavy and super heavy airliners using electric boosted fans down the t