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Transportation Power The Military Science Technology

Electric Vertical Take-Off Aircraft Successfully Tested By DARPA (newatlas.com) 86

Posted by EditorDavid from the up-up-and-away dept.
Slashdot reader drunkdrone tipped us off to some big aviation news: After several years of development DARPA has successfully completed flight-testing of one of the most novel, and odd-looking, aircraft designs we've seen in some time -- the sub-scale electric X-Plane. After calling for an innovative new approach to an aircraft with vertical takeoff and landing capabilities, DARPA awarded its Phase 2 contract to Aurora Flight Sciences in early 2016. Aurora's design includes 24 electric ducted fans, 18 on the main wings and six on the smaller front canards. Both the main wings and the canards are designed to tilt upwards for vertical takeoff before rotating to the horizontal for regular flight... The prototype was also used to trial a number of other technologies DARPA has been developing, such as 3D-printed plastics for flight structures and aerodynamic surfaces.
The article includes video of the test flight, and reportedly the aircraft also successfully tested "sustained hovering." DARPA will now begin officially developing a full-scale aircraft, which has been designated "the XV-24A."
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Electric Vertical Take-Off Aircraft Successfully Tested By DARPA More

Electric Vertical Take-Off Aircraft Successfully Tested By DARPA

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  • So while TFA says the full size version will go 300 knots (345mph) and be able to carry 40% of its 12,000 lb. weight as payload, it doesn't mention the range.

    If it's at all decent, the implications of these VTOL aircraft (with better batteries) should be obvious to all. Coupled with a always on autopilot (with the only user control being redirection or emergency landing) it could transform commuting (assuming a really good air traffic control system).

    The world is really looking like a blade runner future c

    • Probably limiting by the hydrocarbon based fuel carried onboard, per: "A few improvements are slated to be incorporated into the full-scale model, most notably a hybrid turboshaft engine to drive the electric generators powering the fan units, as opposed to simple batteries used in the demonstrator model."

      • Re: (Score:2)

        by swb ( 14022 )

        I'm guessing the turboshaft is meant to provide take-off power and it can cruise on batteries in a kind of winged flight mode? Otherwise I'm not seeing the advantage of a turboshaft given the energy losses associated with electric generation.

        • the transmission is the advantage. look up how large and heavy (and unreliable) helicopter gearboxes are.

          • Agree -- just don't assume that a production version of this won't be pulling up to the Jet-A dispenser to deliver reasonable operational ranges. Might we someday end up with batteries that are as energy dense (volume and weight) -- certainly that is the hope, just not necessarily reality as yet. Even when that stage is reached, time and ease of charging is still going to be a concern (i.e. "portable" military facilities for this kind of aircraft are not likely to be next to a decent sized electrical sub-st

            • Might we someday end up with batteries that are as energy dense (volume and weight) -- certainly that is the hope, just not necessarily reality as yet.

              I'm pretty sure that will never happen. That is assuming one defines a battery as we understand it currently, a device that stores electric energy directly as a reversible chemical process. What some people call "batteries" are really just capacitors or fuel cells that have a form/fit/function similar to a battery, and even then I'm not sure we'd see anything better.

              Jet-A is an incredibly dense energy source that is a liquid at temperatures and pressures that we will commonly run into. This means it can

          • As this is a tilt rotor aircraft I would think that a more appropriate analogy would be with the V-22 and aircraft like it. Or even with other VTOL aircraft, such as the V-8 (Harrier derived craft) or F-35B (lift fan variant).

            What we've had before were two classes of aircraft, helicopters and airplanes. Helicopters could take off and land on small areas but were slow and fuel hungry. Airplanes used much less fuel per mile traveled and/or mass carried but at the cost of needing a large take off and landin

        • I'm guessing as you are but the way I understood it is that the electrical power would be provided by a turbine engine driving a generator. No batteries, or at least none that drive the propellers.

          Batteries have very poor energy density compared to hydrocarbons, a difference of 2 or 3 orders of magnitude. I expect that the prototype used batteries because range is not an issue for testing but cost is.

          When it comes to the losses of electric generation we've seen the advantages of an electric drive train fo

          • Re: (Score:2)

            by swb ( 14022 )

            It sure hasn't hit the recreational marine market, though. You can get pod drives, but they are mechanically driven off of diesel engines.

            I always wondered if they could do a hybrid drive on a boat with a single engine and batteries driving electric motors. I'm only aware of one (newish) maker doing it, but I would think for a lot of the inland boating market where ranges under 25 miles and cruise speeds of 10 knots are common.

            The batteries would be a wash if you removed one of the engines and less fuel

            • The batteries would be a wash if you removed one of the engines and less fuel might offset a heavier generator.

              That does not seem likely to me. We design aircraft with multiple engines because it provides redundancy and convenience. Two engines are nice because they can derive power from a shared energy pool, the fuel tanks. With a single engine and a battery pack the loss of the engine means losing access to that pool of energy that is the fuel.

              Then there is the issue of charging up that battery. Given proper infrastructure the battery could be charged from grid power. In the case of remote locations, or emergencies, the grid power cannot be relied upon. In which case the electricity would come from diesel generators and the like. In that case the batteries would be charged from a generator as part of the ground crew tools, have to be charged from the engine on board using fuel while idle on the ground, or whatever. The energy would still come from the fuel but with the additional losses of charging and discharging the battery.

              If a battery-turbine "hybrid" plane did suffer a failure of either power plant, the turbine or battery, then parts for both would have to be kept on hand. With a two engine craft a power plant failure would typically mean replacing the engine with one that can fit in either spot. It's the low replacement part count that keeps aircraft like the A-10 in the air. The A-10 has very few parts that are unique to left or right. There is no "left wing" or "right wing" there's just "wing".

              A friend of mine worked as ground crew servicing F-16 jets, which has one main engine. A twin engine craft can use power from one engine to restart the other, but a single engine craft does not have that option. There is a battery on board of the aircraft but that is only for navigation and communication. If the engine is in need of restart in the air, or with a lack of proper ground equipment while on the ground, there is a small powerful engine on the plane that can start the main engine. I recall that it runs on hydrazine but I'm not sure about that. Even so there is only enough fuel for the auxiliary engine to attempt two or three engine starts.

              The point is that even with an electric drive system the poor energy density of batteries do not make sense to drive the engines. Electric passenger commuter cars can get away with using battery storage because ranges are short and charging stations are easy to find. Not having to get airborne, or stay afloat, helps considerably too.

              • Re: (Score:2)

                by swb ( 14022 )

                I was thinking of a specific use case -- inland lake recreational marine. A plane is a different animal, as is ocean-running boats.

                The lake I boat on is pretty big -- 22 square miles comprised of a dozen or so interlocking bays, but you would be hard pressed to run more than 30 miles of traveled distance in a single day.

                For this specific application, I don't see why a single engine hybrid, diesel-battery-electric application wouldn't work. Half the boats on the lake are single engine and a total engine fa

                • >I was thinking of a specific use case -- inland lake recreational marine.

                  There's a fun English show about these guys who travel around finding ways to use renewable energy sources to replace traditional hydrocarbon based ones. It's fun because they do the planning, building, and testing right in front of the camera. (Sorry, I can't recall the name right now).

                  Anyway, one job they did was a solar-powered water taxi. I believe the batteries ended up being ballast to counter the roof of solar panels they

                  • Re: (Score:2)

                    by swb ( 14022 )

                    The solar installs I've seen on boats amounted to flush mounted over cockpits or other roofline enclosures. Nothing to catch the wind.

                    Other than the one Greenline with 1.3kw solar, for most purposes solar on a boat is only really useful for offsetting DC consumption for house batteries -- a couple hundred watts -- not propulsion, unless you're doing some really unusual purpose-built solar boat.

                    Shore charging is fine, but you'd really want diesel generation for both higher running speeds than batteries can

    • Will there also be half-naked 1982 Darryl Hannah?

  • Yeah, but the extension cord limits range (Score:4, Funny)

    by Anonymous Coward on Sunday April 09, 2017 @10:03AM (#54201971)

    to a few hundred yards.

    • Yeah, but the extension cord limits range to a few hundred yards.

      I've got two extension cords. Twice the range! At this rate [xkcd.com] I'll have a flying car with a range that covers the city after just a few hundred dollars at the hardware store!

      • And that just brings an image of a massive Traffic "Tie-up", with dozens of miles long extension cords all balled up in a massive knot.

  • And let us hear what the damn thing sounds like.

  • For $19, the price of the "lock" + universal key, a thief can have a nice bike. Noted.

  • Just go to the source.

    newatlas sucks - if you run an adblocker, it won't let you access any of their stories.

    http://www.darpa.mil/news-even... [darpa.mil]

  • This could be a showstopper. Simple explanation...

    * when you scale up a propeller-driven aircraft by a factor of N, the area swept out by the propeller(s) increases by a factor of N^2

    * but the craft's width, height, and length each increase by N, so the aircraft's volume, and therefore weight, increases by a factor of N^3

    Double the scale of the aircraft; propellors sweep out 4 times the area, but the body weighs 8 times as much

    Triple the scale of the aircraft; propellors sweep out 9 times the area, but the

    • I agree about the volume increasing by N^3, but does that necessarily mean the weight increases by that factor? Most of the volume inside the fuselage of an aircraft is air. Empty space to be filled with systems and payload. I guess it could be argued that the most efficient aircraft are designed to transport as close to their full volume as possible of payload, but not all of it will have the same density as the structural material. I suspect you are on the correct path but I'm not sure if the ratio is a s

    • While sometimes that can work against you it can also work for you. When it comes to things like efficiency in heat engines then making them larger can mean the area of losses grows by N^2 but volume of power production grows by N^3.

      Sometimes bigger is better.

  • Comment removed based on user account deletion

  • This aircraft (which is hard to find an actual picture of) seems like a really inefficient design.

    Each engine introduces substantially more weight and drag than does simply increasing the propeller diameter, so usually designers choose to minimize the number of nacelles and engines to what is required to accommodate an engine failure in flight.

    This prototype seems to be taking the opposite approach. While it looks interesting, it also seems like it would have a lot of drag when it transitions into horizont

  • The wings remind me of the gull winged WT715 in H.G. Well "Things to Come" but without the ducts.

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