• 01 Jan 2018 02:29 AM
• 0

ARL Looks to the Future of Vertical Flight

By John M. Doyle
Vertiflite, Jan/Feb 2018

 The US Army Research Lab Reaches Out to Industry, Academia

The ARL Vehicle Technology Directorate is busy working on numerous vertical flight technology projects, and it’s looking out for new ideas from young scientists, collaborative regional campuses, and partners in academia and industry.

Since 1917, researchers at the Aberdeen Proving Ground, home of the US Army Research Laboratory (ARL) in northeast Maryland, have worked on everything from World War I gas masks to ENIAC, the first digital computer. But, in recent years, vertical lift has been getting increased attention as the US Department of Defense (DOD) plans to replace its existing fleet of rotary-wing aircraft in coming decades.

“Over the last five or six years we have grown quite a lot in vertical lift research,” said Dr. Rajneesh K. Singh, acting Chief of the Vehicle Applied Research Division in ARL’s Vehicle Technology Directorate (VTD). “We are now very well positioned to take it up to the next level,” he added.

In an interview with Vertiflite, Singh discussed some of the many vertical lift-related areas being investigated at ARL, a part of US Army Research, Development and Engineering Command (RDECOM). Vertical takeoff and landing (VTOL) research includes technologies to make manned helicopters and other vertical flight aircraft bigger, faster and capable of flying farther distances and with heavier payloads.

Open Campus

Since 2014, ARL has sought to build a science and technology (S&T) network that encourages groundbreaking advances through its “Open Campus” construct. ARL scientists and engineers work side by side with visiting scientists in ARL facilities, and as visiting researchers at collaborating facilities like the University of Texas at Austin’s J.J. Pickle Research Center. Platform mechanics for rotorcraft and unmanned aircraft systems (UAS) are among the research areas where ARL is seeking collaborators.

According to ARL’s Open Campus website, “the project is developing a diversified national ‘hub-and-spoke’ infrastructure to more effectively partner across the national and international S&T ecosystem.” UT Austin serves the ARL South hub, and University of Southern California is the headquarters for ARL West (ARL Central and ARL Northeast are still under development). Each hub has a specific technological focus and also works to “leverage expertise and facilities throughout [that] region to accelerate discovery, innovation and transition of science and technology” in support of DOD and Army S&T development goals.

“ARL is uniquely positioned to provide cutting edge S&T solutions for current and future rotorcraft and autonomous systems,” said Edward C. Shaffer, acting director of VTD. “In addition to the new VTD research facilities that have been established at Aberdeen, ARL’s Open Campus construct has encouraged more robust and flexible engagement with partners. For example, we are hiring ARL post-docs to perform work at offsite locations, hand-in-hand with industry and academic partners, opening up the aperture for ARL’s access to outside research capabilities, as well as further exposing the broader community to specific research challenges of concern to ARL,” he said.

Developing Knowledge

In addition to manned rotorcraft, ARL researchers also are studying technologies to improve the performance and capabilities of drones, from the smallest micro air vehicles, to ones weighing up to 1,320 lb (600 kg). VTD, where Singh works, is exploring ways soldiers can make mission-specific, small UAS in a hurry through additive manufacturing — aka 3D printing. Singh’s unit also is researching small drones that can transition from powered lift vertical flight to wingborne forward flight. As part of the Army’s Future Vertical Lift (FVL) program, the directorate also has explored innovative technologies that one day may boost helicopter forward flight speed to more than 300 kt (555 km/h).

Nevertheless, ARL is focused on basic research, Singh cautioned. “We don’t develop products. We develop knowledge,” he said. The goal is “to develop enabling technologies and enabling knowledge that could create these kinds of platforms.” While the research may be basic, the technology is not. VTD teams use high-performance computing (HPC) modeling and simulations for computational aeromechanics research. That includes developing algorithms, methods and tools for flight mechanics, dynamics predictions, performance assessments, and visualizations of the impact that various technologies can have on rotorcraft.

With support from VTD’s Dr. Hao Kang, Singh used high-performance computing to develop models for aeromechanic evaluation as part of the modeling and simulation used by an Army team to assess the four industry designs for the Joint Multi-Role Technology Demonstration (JMR-TD) initiative. The JMR-TD is the preliminary “art of the possible” stage that will inform aircraft and system design for the Pentagon’s joint-service FVL program (see “Getting Smart for FVL,” Vertiflite, Nov/Dec 2016). The Army has budgeted $350M for the JMR-TD, with industry probably also investing a total of twice that much.

Future Vertical Lift

FVL was established by the DOD in 2009 to replace the US military services’ current helicopter fleet with higher-speed and longer-range aircraft for the next 25 to 40 years. The first step in that enormous task was exploring and testing designs and technologies promising to deliver the speed, lift and maneuverability sought by the Army. As the precursor to FVL, the JMR-TD program — administered by RDECOM’s Aviation and Missile Research, Development and Engineering Center (AMRDEC) — will examine and demonstrate transformational vertical lift capabilities proposed by Bell Helicopter’s V-280 Valor tiltrotor and the Sikorsky-Boeing team’s SB>1 Defiant coaxial compound rotorcraft.

Traditional helicopter configurations, such as the Army’s AH- 64 Apache and UH-60 Black Hawk, are incapable of reaching the speeds of 230 kt (425 km/h) and greater sought for FVL. But designing high-speed vertical flight aircraft presents numerous technical challenges with regards to vibration, loads and stability, Singh said. One example is the instability of tiltrotor designs at high speed. Tiltrotor aircraft are subject to aeroelastic instability that limits the forward maximum speed they can fly (the V-22 has a 23% very thick wing to overcome this). To study the problem, ARL is building a test rig that would allow wind tunnel experiments in the Transonic Dynamics Tunnel (TDT) at NASA’s Langley Research Center in Hampton, Virginia. The TDT is a closed-circuit, continuous flow, variable pressure wind tunnel, designed to identify and solve aeroelasticity issues confronting fixed-wing, helicopter and tiltrotor configurations. The test rig will generate data that could help engineers overcome the instability problem. “That would allow us to improve prediction capabilities for modeling and simulation,” Singh said.

Drones, Big and Small

Some of the VTD’s latest work involves small UAS (sUAS). One is a drone just over half a pound (250 g) that can tilt its propellers to go from hovering like a helicopter to flying horizontally like an airplane. The small tiltpropeller drone was developed by Dr. Steve Nogar, a postdoctoral researcher in VTD.

Another project uses 3D printing to deliver mission-specific sUAS practically overnight to troops in the field. Called Tactical 3D Printing, or Tac3D, the project is a collaborative effort between the Army’s RDECOM, and the Marine Corps’ Installations and Logistics Division. The Marines’ Next Generation Logistics Cell supports efforts to provide small troop units with mission-tailored quadcopters when and where they are needed. ARL collaborated with the Marines to learn how such mission-tailored sUAS might be employed in the field for a tactical advantage. Applying their expertise in additive manufacturing, human factors engineering, UAS design, analysis, prototyping and experimentation, ARL engineers updated a baseline sUAS design by eliminating nearly all mechanical fasteners, standardizing mechanical interfaces, innovating quick-connect arms and landing gear, reducing print time, and improving structural integrity.

In late September, ARL technicians and engineers demonstrated quadcopters made through additive manufacturing for the Marines at Camp Lejeune, North Carolina. To demonstrate the usefulness and convenience of custom-made sUAS for a variety of tasks, troops from the 2nd Marine Division with different occupational specialties were invited to fly the 3D drones. “At this point we are focusing on intelligence, surveillance and reconnaissance [ISR] missions,” Eric Spero, a team leader in the VTD told the Marines. The tiny drones can carry a variety of cameras from infrared to streaming video, he added.

ARL has developed a digital catalog to help sUAS users select the most mission-appropriate vehicle. Once their choice is made, a digital technical data package is downloaded, a kit of electronics is taken off the shelf, structural components are manufactured using 3D printing technology, assembly instructions are followed, and an sUAS is fabricated and then flown — all within 24 hours. This approach speeds up and simplifies the process of obtaining a small drone in the field. Instead of waiting for delivery of the aircraft, or spare parts from a rear area, users can make them almost entirely in the field. The approach also could make missions more efficient and successful by fitting the UAS to the mission instead of the other way around. The plan avoids parts obsolescence through a modifiable library of components. “I think 3D-building an electric motor is still a few years away” Singh said, so users still will have to obtain some parts, like motors from the digital catalog. “But in the future, we see a day where all parts could be designed and manufactured in the field,” Singh added.

Hoverbike and Transformer

ARL researchers are also working on Group 3 drones, which range from 55 lb (25 kg) to 1,320 lb (600 kg). Eventually they may have the payload capacity of a few hundred pounds, “which is perfect for cargo resupply — or even someday, a flying platform for soldiers,” Singh said. VTD has made significant contributions to the initial feasibility evaluation of the joint tactical aerial supply vehicle (JTARV), also known as the “hoverbike.” The rectangular-shaped, unmanned quadcopter may one day make it possible for troops on the battlefield to order and receive supplies rapidly.

Researchers envision a future JTARV flying low to the ground or thousands of feet in the air, at speeds of 60 mph (95 km/h) or more. The prototype vehicle is electrically powered, but researchers are looking at hybrid propulsion to increase the JTARV’s range. ARL began exploring the JTARV concept in 2014. The lab identified a manufacturer, Malloy Aeronautics, based in Berkshire, England, and a systems integrator, SURVICE Engineering, of Belcamp, Maryland; entered a contract; and moved quickly from concept to full-scale prototypes. Malloy Aeronautics’ Hoverbike utilizes two pairs of side-by-side overlapping propellers in a quadrotor configuration. (For more on Malloy’s electric Hoverbike, go to www.evtol.news/malloy-hoverbike.)

The JTARV is now a joint effort with the Marine Corps, led by researchers at the Army’s Armament Research, Development and Engineering Center (ARDEC) at Picatinny Arsenal, New Jersey. However, VTD has worked on the sub-system technologies that may lead to multiple design concepts, Singh noted.

ARL researchers are also studying technology that would enable a UAS operator to transform a single vehicle’s shape to fit the mission. A general challenge in vertical flight research, Singh said, is the contradictory power requirements between taking off and landing vertically and flying horizontally in cruise flight mode. ARL researchers are exploring how to make a reconfigurable platform that could change its shape depending on the task. Singh said the concept would be more like a flying Swiss army knife than a small, unmanned version of the V-22 tiltrotor aircraft. An Osprey has basically two form-designs, one for hover and one for forward flight, he said, adding, “In the future, we could think of a vehicle that has infinite forms.”

ARL has widened its quest for shape-shifting drone concepts by sponsoring the 2018 AHS student design competition (see www.vtol.org/sdc). It is the first time ARL, or any DOD agency, has sponsored the AHS student competition. The goal of this year’s competition is to design a Group 3-sized unmanned VTOL aircraft that can achieve high-speed forward flight and efficient hover, using novel, reconfigurable propulsive and lifting devices. The vehicle should have superior performance over a comparably sized aircraft that does not have reconfigurable systems, according to the AHS competition guidelines.

In addition to rules governing takeoff weight, operating altitude, airspeed and payload capability, the competition requires all entrants’ aircraft to be capable of operating in a megacity-type environment and fitting in narrow streets and confined spaces. When in hover configuration, the aircraft’s maximum horizontal dimension is limited to no more than 3 meters (9.8 ft).

The latest student design competition isn’t ARL’s only outreach to the vertical flight community. In 2016, the Army lab established a local AHS chapter for the Aberdeen Proving Ground, which is celebrating its 100th birthday this year. Its scientists and engineers wanted to start a local chapter of AHS because of the high concentration of researchers in the Aberdeen area. In addition to the Proving Ground’s North and South campuses, there are a lot of companies and organizations researching technologies to advance the capabilities of helicopters and other vertical lift platforms.

More than 40 aviation engineers, researchers and enthusiasts from across the mid-Atlantic region turned out for the chapter’s first meeting in August 2016 (see www.vtol.org/aberdeen). VTD’s Singh, who has been chosen as the AHS Aberdeen Chapter’s first president, hopes chapter activities will help inform students in the area about ARL’s internship program. This year, two interns worked on high-fidelity computational fluid dynamics (CFD) research on tiltrotor aeroelastic stability.

“We want to reach out even more than we have about this internship program,” said Singh. “Our hope is that through AHS we can publicize some of those opportunities and reach out to the best of the best.”

About the Author

John M. Doyle spent 27 years as a writer and editor with the Associated Press and Aviation Week & Space Technology. As a freelance defense and aviation journalist, he writes frequently about the manned and unmanned vertical lift aircraft needs of the military, homeland security and private sector. His website is http://4GWAR.wordpress.com.

Doyle authored the article on cyclocopters in the July/Aug 2017 issue of Vertiflite, “Paddlewheel Propulsion Is Now Vertical and Multi-Modal” — this research was primarily sponsored by ARL’s Micro Autonomous Systems Technology Collaborative Technology Alliance (MAST-CTA).