Friday, March 4, 2016

A new development in vertical takeoff and landing?

I was very interested to learn that Aurora Flight Sciences has won the Phase 2 award of DARPA's X-Plane vertical takeoff and landing project.  Here's an artist's concept of its proposal.

DARPA said in a press release:

DARPA has awarded the Phase 2 contract for VTOL X-Plane to Aurora Flight Sciences.

“Just when we thought it had all been done before, the Aurora team found room for invention—truly new elements of engineering and technology that show enormous promise for demonstration on actual flight vehicles,” said Ashish Bagai, DARPA program manager. “This is an extremely novel approach,” Bagai said of the selected design. “It will be very challenging to demonstrate, but it has the potential to move the technology needle the farthest and provide some of the greatest spinoff opportunities for other vertical flight and aviation products.”

VTOL X-Plane seeks to develop a technology demonstrator that could:

  • Achieve a top sustained flight speed of 300 kt to 400 kt
  • Raise aircraft hover efficiency from 60 percent to at least 75 percent
  • Present a more favorable cruise lift-to-drag ratio of at least 10, up from 5-6
  • Carry a useful load of at least 40 percent of the vehicle’s projected gross weight of 10,000-12,000 pounds

Aurora’s Phase 2 design for VTOL X-Plane envisions an unmanned aircraft with two large rear wings and two smaller front canards—short winglets mounted near the nose of the aircraft. A turboshaft engine—one used in V-22 Osprey tiltrotor aircraft—mounted in the fuselage would provide 3 megawatts (4,000 horsepower) of electrical power, the equivalent of an average commercial wind turbine. The engine would drive 24 ducted fans, nine integrated into each wing and three inside each canard. Both the wings and the canards would rotate to direct fan thrust as needed: rearward for forward flight, downward for hovering and at angles during transition between the two.

The design envisions an aircraft that could fly fast and far, hover when needed and accomplish diverse missions without the need for prepared landing areas. While the technology demonstrator would be unmanned, the technologies that VTOL X-Plane intends to develop could apply equally well to manned aircraft. The program has the goal of performing flight tests in the 2018 timeframe.

There's more at the link.  Here's a video demonstration of the concept.

This is a fascinating proposal for several reasons.  It uses ducted fans in a new way, relying on lots of small fans rather than a couple of big ones.  If that works in the X-plane, the next step will be to scale it up to operational size.  Furthermore, the fans are electrically powered, rather than driven by a motor. That means, if battery power packs continue to develop at their present rate, in the not too distant future such an aircraft might not need an engine on board at all.  Its batteries could be charged on the ground, topped up in flight by solar panels along the wings and fuselage, and fully recharged from an external source once it reaches its destination or returns to its point of departure.

I'll be watching this project with a great deal of interest.  Good luck to Aurora and its partners.



Jacquejet said...

Color me skeptical. The drag index on that thing will be yuge (huge). Reminds me of some of these.

J G Pelham said...

We are working on hybrid electric propulsion at Cranfield. Not my department but I understand the problem is efficiently converting the power and getting it to the fan motors. A colleague who is doing his PhD in this kept muttering about needing superconductors as the losses are very high. That was for a flying wing without VTOL using reasonably large fans. This uses an array of small fans and would be much less efficient. Could it fly? Maybe. Would it be able to carry a useful payload a decent range? Maybe. But for the same money you could have several conventional aircraft that could carry more and go further.

JL Domingo said...

There has been some research done in aircraft with turboelectric propulsion before:

Anonymous said...

It will never work. It obviously need 4 more propellers.


Jacquejet said...

It's the new B-52. 52 engines

Anonymous said...

Total mass of batteries would be greater than the mass of an engine and fuel. But again it's DARPA so it doesn't have to be viable, it just has to be cool!


Bob said...

Back to the days of the biplane! Propellers and everything! No room for anything but batteries. Next phase will have solar panels on those wings.

Just another grab for funds from the sucker taxpayers pocket. Like anonymous said: "... it doesn't have to be viable, it just has to be cool!"

Bob said...

Wasn't finished...

400kt = 460mph. Hell yes... those wings would rip right off at over 450 miles per hour. And to rotate those wings? Well Bell is still trying to certify their flying brick after three decades a billions of dollars.
DARPA should be renamed to DABRA, the B for bullsh*t.

Eisenhower warned us.

montieth said...

One wonders what sort of lift advantage they're getting with the ducted fans blowing over the top of the wings in the lower box. Makes me think of the Custer Channel Wing which has substantial powered lift.

Jonathan H said...

I agree with the others above - a bunch of small fans on what is essentially a biplane involved LOTS of drag and extra weight; I doubt this thing will ever fly and if it does it won't do much. There are some things that can be done at small scale that don't scale up (for example, see anything with more than 2 rotors).

I've seen Aurora propose 'out there' solutions in the past, and a review of their website seems to show that what they have implemented is considerably more conventional than their initial plans.

There are reasons that most aircraft are similar - because it is what works, is affordable, and controllable. Look at the time and money the US military put into getting the Osprey fielded and the F-35 developed and they are more conventional than things like this. (From what I've seen, the original Osprey proposal was more unique and ultimately unworkable).