Thinking Outside the Box….
…Is Inside the Box at Aurora Flight Sciences
By Douglas Nelms
Since the last comprehensive review of Aurora Flight Sciences (Vertiflite, March/April 2013), much has happened with the company. This article provides an update of the company’s innovative vertical flight programs.
On Nov. 8, 2017, The Boeing Company acquired Aurora Flight Sciences, which bills itself as “an innovative technology company which strives to create smarter aircraft through the development of versatile and intuitive autonomous systems.”
Or to put it another way, a company whose entire existence is thinking outside the box.
The Dawn of Aurora
The company was started in May 1989 by John Langford, who graduated from the Massachusetts Institute of Technology (MIT) with a PhD in Aeronautics and Public Policy. In the mid-80s, he had been a leader in programs to design and fly human-powered aircraft, including the 1988 flight flight of the Daedalus (named for the mythological Greek inventor of flight), which still holds official world records for total distance, straight-line distance and duration for a human-powered aircraft.
With the success of the Daedalus project, Langford began looking looking around for new challenges, ultimately creating the company he named Aurora. Started with two employees, the company now has about 550 employees scattered among its four main sites: its headquarters and prototyping facility at Manassas Regional Airport in Manassas, Virginia; production sites in Bridgeport, West Virginia, and Columbus, Mississippi; and a research and technology center in Cambridge, Massachusetts, adjacent to the MIT campus. The company’s European office is located in Luzern, Switzerland, supporting the development of Aurora’s electric vertical takeoff and landing (eVTOL) aircraft unveiled at the Uber Elevate Summit in April 2017.
It was the company’s success as a leader in innovative thinking that led to its acquisition by Boeing, Langford said, giving it an even greater ability to search out markets that require innovative technology.
“Aurora is an independent subsidiary of Boeing,” he said. “What that means is that it combines Aurora’s innovation with Boeing’s strength. They are the world’s largest [aerospace company] with one of the most successful product lines. But they do not build eVTOL today. No company builds eVTOL today. That is a market that does not exist. So how do you go after a market that doesn’t exist? The idea is to have Aurora explore these markets that involve very advanced technology, then do the prototyping work, then the market exploration work, and hopefully find new markets and new programs that can be fed into Boeing so that when someone wants a few thousands of those airplanes, Boeing can do it. So that’s the idea behind the merger, our innovation with their size and strength.”
Aurora has already become a leader in the design and building of autonomous, unmanned fixed-wing aircraft, and currently has under development the D8, a concept aircraft planned as a commercial airliner. Designed in conjunction with Pratt & Whitney and sponsored by NASA, the D8 “has the potential of achieving a 71% reduction in fuel burn, a 60 EPNdB reduction in noise and an 87% reduction in [landing and takeoff] NOx relative to current narrow-body aircraft in operation,” the company said.
Aurora is also heavily involved in vertical flight, with three major projects now underway: the eVTOL air taxi, the unmanned XV- 24A LightningStrike and AACUS — the Autonomous Aerial Cargo Utility System. In December, Vertiflite sat down with key members of the Aurora team to discuss developments in these programs.
The eVTOL aircraft is being designed to carry two to four passengers, a pilot and luggage. Powered lift is provided by eight vertically thrusting propellers plus a pusher propeller for high-speed forward flight. The aircraft is fully electric and can be flown manned or as a fully autonomous UAS. Aurora is developing the current prototype for the Uber Elevate competition; Uber plans flight-testing to begin in 2020 (see “Uber Elevate Summit Outlines eVTOL Flight Plan”, Vertiflite, July/Aug 2017). Uber has partnered with two cities in the US: Dallas, Texas, and Los Angeles, California; Dubai, UAE, was previously a planned city but was dropped by Uber last year and replaced by LA.
At the first Uber Elevate Summit in April 2017, Aurora revealed that its quarter-scale prototype had been conducting flight testing, and demonstrated transitions between vertical takeoffs and landings, and forward flight. The full-scale aircraft, sized at 1,760 lb (800 kg), will be about 26 ft (8 m) in length and width. Aurora expects that the noise at takeoff will blend in with background road traffic noise at a height of 60–100 ft (18–30 m), making the aircraft essentially “inaudible” from the ground when in cruise flight.
Although little has been released on Aurora’s eVTOL since the first Elevate Summit, the company is expected to provide an update at the second Summit, being held on May 8–9 in Los Angeles.
The XV-24A LightningStrike is being developed under the Defense Advanced Research Projects Agency’s (DARPA’s) VTOL X-Plane program.
Phase I of the program was a 22-month period for preliminary design of the concept. Four companies competed for the contract under Phase I of the program, with DARPA selecting Aurora over Lockheed Martin, Boeing and Karem Aircraft for Phase II. The entire program was funded at $130M.
DARPA’s objectives for the VTOL X-Plane program, as stated in 2014, were to develop a technology demonstrator that could achieve a top sustained flight speed of 300–400 kt (555–740 km/h), raise aircraft hover efficiency from 60% to at least 75%, present a more favorable cruise lift-to-drag ratio of at least 10 (up from 5 or 6 for a typical rotorcraft), and carry a useful load of at least 40% of the vehicle’s projected gross weight of 10,000– 12,000 lb (4.5–5.4 t).
The idea was to specify performance objectives with efficiency metrics “that required significant improvements over the state of the art of vertical flight, but that could be combined in future renditions to create useful capabilities,” said Dr. Ashish Bagai, the original DARPA program manager for the VTOL X-Plane program, now a researcher at the University of Maryland. (Dr. Mark Costello, formerly at Georgia Tech, is now the DARPA program manager.)
In an interview with Vertiflite last year, Bagai stated: “What we are doing is not necessarily an end-state configuration. We are demonstrating performance parameters that are rather challenging and have never been demonstrated before can actually be demonstrated on an air vehicle, that technologies can be matured and these technologies, once matured, would be available for a wider host of applications and that they could be applied to different mission spaces. What DARPA is developing now is basically the demonstration of technologies that can be expanded to the other realms.”
The VTOL X-Plane program “is a new species in the taxonomy of vertical flight,” he said. “This is genuinely what we had hoped to inspire and converge to when we formulated the problem. We wanted to avoid the repetition of history — we didn’t want to just build a better helicopter or revisit a previously investigated concept. I was actually looking for something that was completely out of the box. And you can see this is totally out of the box.”
Aurora has stated that the aircraft now being developed is not meant to be a production aircraft. It is a pure technology demonstrator. A proof of concept. That is not to say that the aircraft itself could not be productionized and moved toward something the military would need or could use in certain areas.
The LightningStrike design takes advantage of computer-based computational aerodynamics, a lot of composites, and an unconventional propulsion approach that was even more radical when it was initially proposed. The aircraft uses a hybrid-electric system with a gas turbine engine driving three electrical generators to power electric fans distributed along the lifting surfaces.
LightningStrike is, of course, an X-Plane, so the program is really a testbed for the technology, which could lead in a lot of possible future directions. It’s already led up to an eVTOL sector where companies like Uber are interested in small vehicles that could carry people that are fully electric and autonomous.
The program is now in Phase II, with a 20% scale model of the X-Plane already built and flown. The subscale vehicle demonstrator (SVD) is fully electric, while the final full-scale prototype will be a hybrid, using both electric battery power and a turboshaft engine.
Twenty-four distributed electric propulsion ducted fans provide vertical and horizontal thrust: six in the canard and 18 in the wing. Both the wing and canard tilt vertically for VTOL or horizontally for forward flight. The fans are all constant speed, variable pitch units.
“In order to get the efficiencies in full flight and in vertical flight, and execute conversion maneuvers that do not require that the aircraft give up vertical altitude, we have some pretty significant interactive aerodynamic benefits by embedding the fans within the wings in the way they are designed. The wings continue to generate lift even through a 90-degree rotation from the full vertical to the full horizontal,” Bagai said. “Any conventional wing would have stalled at any other angle above 12 degrees or 10 degrees of incidence.”
“We do that by controlling the air flow over the wing, both the upper and leading-edge surfaces between which the motors are sandwiched. This produces a significant mechanism to keep the flows attached over the wings,” he explained.
The full-scale aircraft requires three megawatts of power to run the fans. So, while the SVD is totally battery powered, the full-scale X-Plane would not be able to carry the weight of batteries sufficient to produce the three megawatts of power, thus requiring hybridization with a turbine engine.
A single 6,000 shp (4.5 MW) Rolls-Royce AE1107C engine turning a RR-built high-speed gearbox powers three Honeywell generators that each produce a megawatt of power. Those three megawatts will be phased to three banks of electric motors. Conductors, or electric wires, are routed from the three generators to each individual motor. The electric motors driving the fans are built by ThinGap, based in Ventura, California.
“Three megawatts is a very, very large amount of power,” Bagai said. “The development of the concepts to run the motors, to keep them lightweight, to transfer energy from the source to the motors, and to manage the efficiency of the system, are all very significant advancements to the technologies that we are developing here. None of this has been done before, certainly not at this level. There may be battery-powered aircraft that have a few hundred kilowatts, but not three megawatts.”
The wing and canard rotate 90 degrees for vertical lift or horizontal flight. In that regard, the LightningStrike works like other tilt-thrust aircraft. Each of the ducts has a control surface on the upper and lower surface of the wing, and moves to redistribute lift across the upper surface to provide fine control of the aircraft in both hover and forward flight.
The LightningStrike is planned as an unmanned aircraft, with an avionics package developed by Aurora. It will fly using waypoint navigation, typical of current UAS. The aircraft doesn’t have a pilot directly in the loop, although there is a pilot supervisory control, with a controller who can take over manually or reconfigure the computer to make changes in the flight plan. However, the aircraft has the ability to make a decision based on a failure mode that happens on the aircraft. For instance, if it loses its link to the ground control station, the aircraft is programmed to automatically fly to a specific waypoint and land by itself.
Concepts for manned variants are being considered. These include armed escorts for the V-22 or utility aircraft to fill the role of the UH-60.
The chief test pilot for the program is Chris Baughman, a former Air Force test pilot. He commanded the SVD and will also remotely fly the actual aircraft.
Aurora is using commercial-off-the-shelf (COTS) components from companies like L3 and Rockwell Collins. These include the landing gear, which they adapted from the Sikorsky S-76 helicopter.
As noted, Aurora was selected by DARPA for its preliminary design at the end of Phase I. Phase II will build and deliver the X-Plane, which Aurora is now in the process of completing.
A third vertical lift program Aurora has underway is the Autonomous Aerial Cargo Utility System (AACUS), developed under the US Office of Naval Research (ONR). AACUS is designed to be an agnostic system configured for basically any vertical lift aircraft to provide unmanned resupply to Marines in a forward area.
Using this system, a Marine in the field would be able to request resupply from a rear base using just a handheld tablet. The aircraft would then fly to the forward location using its own navigational system and, using on-board technology, determine a safe landing zone. All navigation and landing processes would be handled totally autonomously by the aircraft systems.
Aurora provides the human/systems interface on an AACUS-enabled UH-1H (or AEH-1) as its test bed. The system was awarded a Special Airworthiness Certificate in October by the US Federal Aviation Administration (FAA), allowing it to operate autonomously with a pilot on board solely to monitor the controls. This, in turn, led to successful demonstrations to the US Marine Corps at the USMC Quantico base in December. Those demonstrations ended the third and final phase of the program. AACUS will now transition to the Marine Corps for experimentation and potential acquisition, the company said.
If the AACUS determines that a preselected landing zone is an unsafe area, it will look for the nearest area that is safe. If the forward unit moves prior to the arrival of the resupply aircraft, the Marine simply uses a handheld tablet to put in the new coordinates.
Langford noted that the major difference between AACUS-controlled aircraft and current UAS is that current UAS are either remotely controlled — so there is a human somewhere flying them onto a runway — or they are autonomous operations where the aircraft is on its own. In the first instance, a radio linkage is required, “and if you lose the linkage, you lose the aircraft.” In the second, “it has no way of independently knowing where the runway is, or knowing if anything is on that runway. And if you put in the wrong parameters, it will try to land wherever you told it to land.”
In the case of the AACUS aircraft, “it creates its own map by scanning the area with lasers, and detects safe and unsafe areas where it flies, tells the user what it is about to do, and asks if that is okay. The user than has to authorize the landing, saying “yes, that’s okay.” Or the user can wave it off. That is a really big step in what these aircraft can do.”
Aurora has designed, produced and flown more than 30 unmanned air vehicles since its inception and has collaborated with Boeing on the rapid prototyping of aircraft and structural assemblies for both military and commercial applications during the last decade. But its pioneered technologies of long-endurance aircraft, robotic co-pilots, and autonomous electric VTOL aircraft have marked its rise to prominence.
About the Author
Douglas Nelms is a retired Army rotary-wing pilot, and previously the managing editor of Rotor & Wing magazine. He is now a freelance writer specializing in the helicopter industry.