DARPA's unmanned X-Plane packs electric fans aplenty for vertical take-off and landing

DARPA's unmanned X-Plane packs...
DARPA’s Vertical Takeoff and Landing Experimental Plane (VTOL X-Plane) program seeks to combine fixed-wing and rotary-wing technologies
DARPA’s Vertical Takeoff and Landing Experimental Plane (VTOL X-Plane) program seeks to combine fixed-wing and rotary-wing technologies
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Artist's concept of the VTOL X-Plane taking off
Artist's concept of the VTOL X-Plane taking off
DARPA’s Vertical Takeoff and Landing Experimental Plane (VTOL X-Plane) program seeks to combine fixed-wing and rotary-wing technologies
DARPA’s Vertical Takeoff and Landing Experimental Plane (VTOL X-Plane) program seeks to combine fixed-wing and rotary-wing technologies

If there was a competition for the oddest looking aircraft, then DARPA's VTOL Experimental Plane (VTOL X-Plane) would have to be in the running for the main prize. With a modularized, cellular wing design that looks like a flying set of cupboards, the unmanned aircraft is a hybrid of fixed-wing and rotary wing technologies designed to create a vertical take-off and landing (VTOL) aircraft that boasts greater range and speed capabilities.

VTOL aircraft have been around in one form or another for over a century, but even the best of them have been notorious for their inferior payload, stability, range, and speed capabilities when compared to traditional fixed wing aircraft. DARPA's VTOL X-Plane program is looking to overcome this problem with a new modular design that it's claimed will provide radical improvements in both vertical and horizontal flight capabilities.

The goal is to build a demonstrator aircraft that can reach a top sustained speed of 300 to 400 knots (345 to 460 mph, 555 to 740 km/h), hover with an efficiency of at least 75 percent instead of the current 60 percent, reduce the cruise lift-to-drag ratio from five or six to 10, and carry a payload equal to 40 percent of the X-Plane's 10,000 to 12,000 lb (4,536 to 5,443 kg) gross weight.

The VTOL X-Plane is the result of Aurora Flight Sciences Corporation's Phase 2 design contract for the program and is aimed at addressing both vertical and horizontal flight requiements. DARPA says that by calling on over half a century of advanced air vehicle and aeromechanics design and testing, adaptive and reconfigurable control systems, and highly integrated designs, the VTOL X-Plane does away with conventional mechanical drive systems in favor of a modular approach.

Artist's concept of the VTOL X-Plane taking off
Artist's concept of the VTOL X-Plane taking off

What this means is that instead of a single powerplant directly powering one or two rotors by way of a shaft, the VTOL X-Plane has two large rear wings and two smaller front canards. These are made up of cells carrying 24 ducted fans – nine integrated in each wing and three in each canard. These each have their own electric motor and all 24 are powered by a turboshaft engine off a V-22 Osprey tiltrotor aircraft, which cranks out 4,000 hp (3 MW) of electrical power.

To control this arrangement, the VTOL X-Plane has power distribution systems for multiple fans in a "transmission-agnostic air vehicle design." That means no gearbox, so the flight control system must be able to alter the thrust of each fan independently for efficiency as well as for changing from vertical to horizontal flight and back.

"This VTOL X-plane won't be in volume production in the next few years but is important for the future capabilities it could enable," said Ashish Bagai, DARPA program manager. "Imagine electric aircraft that are more quiet, fuel-efficient and adaptable and are capable of runway-independent operations. We want to open up whole new design and mission spaces freed from prior constraints, and enable new VTOL aircraft systems and subsystems."

Flight tests are scheduled for 2018 and DARPA says that the VTOL X-Plane technology is also suitable for manned aircraft.

The animation below shows the DARPA VTOL X-Plane in action.

Source: DARPA

VTOL X-Plane Phase 2 Concept Video

Way too complicated. These guys have it:
@DennisBuller - Would that Arcturus UAV scale up to a larger size and weight though? I think the Darpa vehicle is intended to carry a large payload of either missles, supplies for ground troops, or actual passengers. I don't think you can just make everything 3 times bigger on a quadcopter and have it carry 3 times the load. You'll probably see more drones like the Arcturus UAV for small reconnaissance missions in the future though.
Bill Jackson
Bill Jackson · University of Toronto There seems nothing wrong with the DARPA approach that asks for submissions, analyzes them, and then selects one(or more) to proceed to a later stage. Do not forget that many smaller props are better than the huge swept area of 2 props, as we have seen. The enclosure of the prop will increase thrust (mass efficiency), and not add excess mechanical complexity, as AC powered, digital controlled motors are 1000 times as reliable as piston engines, and ~100 time as re;iable as the power turbines. So I expect this to be tried and if found worth, to proceed, and if failed, to know why for the next step. I recall large 2 fan machines, with similar objectives being mechanical monstrosities
Robert Bernal
This, and the drones, together will meld into the "car" of the future. Imagine very little road repair and nature returning to the "land", as must be, for the biosphere to survive the Anthropocene. Solar and batteries will be "printed" much cheaper than they are today, to enable at least a few trends of miles of flight. A generation later, fusion on a chip aught to do the long range trick. Self flying pods will be easier to program than self driving cars because there will be no human psychology issues (one unpredictable driver, foods, etc, could cause problems for ground base self driving vehicles.
I think that is really neat. It would be - IMO - cooler if it could carry a person. Perhaps use it from carrying things or people?
That large frontal area suggests a great deal of drag would occur. I don't think it will get much range as the fuel required will be limited. In short, it looks like a boondoggle project to me.
It looks to be an interesting concept. The small multi-fan idea would follow the 'dont put all your eggs in one basket' principle. However keeping the power generation to one central unit would reduce complexity of maintenance and servicing. The fan units could be simply 'plug-in' components. The transition from vertical to horizontal flight could be tricky. I think a lot of models will need to be built before real money is spent on a full size version.