Up in the Air


For Hovakimyan, safe personal aviation is the ultimate goal

W. Grafton and Lillian B. Wilkins Professor Naira Hovakimyan has manifested her passion for aviation in a number of diverse projects.

Naira Hovakimyan
W. Grafton and Lillian B. Wilkins Professor Naira Hovakimyan 

Over the last 20 years, she has worked to develop the L1 adaptive control system. As the only controller cleared by pilots for stall and post-stall fight regimes in NASA’s Aviation Safety program from 2007 to 2010, hers was the first adaptive controller to be tested on manned aircraft – which she did several times between 2015 and 2018, including on Learjet and F-16 platforms at Edwards Air Force Base. The controller’s performance was always verified according to its theoretical predictions, making it an invaluable approach for safety-critical systems.

“As a team, we are now working on advancing the L1 adaptive controller through technology transition and maturation phases,” said Hovakimyan, who noted that researchers from MIT, Georgia Tech, University of Nevada, Reno, and North Carolina Agricultural and Technical State University collaborate with her group on the NASA University Leadership Initiative – alongside industry partners Lockheed Martin and Sierra Nevada Corporation – to enable the technology transition to urban aerial vehicles (UAVs).

“We are focused on the verification and validation tools and frameworks for the L1 adaptive controller, augmented with robust perception and learning-enabled components, that can safely and securely fly humans in urban areas. Ideally, one should be able to continue living in their affordable house in Urbana-Champaign, have a fancy dinner in Chicago and maybe consider working in Ohio. With UAVs this should be easy to do.”

Graduate students in the aviation lab testing drones.
Hovakimyan's research assistants test their drones in the Advanced Controls Research Laboratory.

Some of Hovakimyan’s past projects include parcel delivery with drones and at-home elderly care with small aerial vehicles. She is cofounder and chief scientist of Intelinair. Her vision for the future of her work centers around the idea of personal aviation. With the L1 adaptive control framework’s capability to support the development of autonomous solutions for a broader class of airborne vehicles, she anticipates that flying cars will become a reality—and with them, improved accessibility for housing, transportation, and job opportunities. She now co-directs the Center for Autonomous Vehicles in Air Transportation Engineering (AVIATE), supported by NASA.

Hovakimyan is also excited about her growing number of PhD students and graduates. “In the next 5-7 years, I will have graduated 50 students,” she reflected. “That’s 50 models of this research going out into the world and carrying on the legacy.”











Bei Tse Chao and May Chao Professor Tonghun Lee

Novel UAV technologies for a secure future

The Center for UAS Propulsion (CUP), a research cohort established to advance the next generation of Unmanned Aircraft Vehicles (UAVs) and systems, has been steadily expanding since its advent in 2018.

Led by Bei Tse Chao and May Chao Professor Tonghun Lee, CUP’s research thrusts are primarily focused on ignition, surface materials, battery technology, and power management for UAVs at subsonic and supersonic speeds in variable atmospheres, with projects such as extreme fuel ignition characterization, tribological materials for extreme low viscosity, and high-pressure compact air management. At Illinois, roughly 10 students and two postdocs work on various aspects of CUP projects in Lee’s Advanced Energy and Propulsion Laboratory.

M1 combustor
Shown is the M1 combustor, a laboratory-scale single-sector cumbustor designed to replicate a single swirl cup of a gas turbine engine. The M1 combustor has up to 4-side optical access for implementing a wide array of advanced laser and optical diagnostics. It has been utilized to study various aspects of swirl-stabilized spray flames including spray breakup, spray droplet distribution, flame structure and flame dynamics.  

“We’re developing new combustors to look at different types of combustion strategies for the Department of Defense, and also contributing to alternative fuel integration within the Federal Aviation Administration,” Lee said of the group’s current work.

Lee’s team visited Argonne National Laboratory in April 2023 to collect experimental data from a combustor built specifically to test a range of fuels intended for turbine engines. They used the lab’s advanced photon source, a high-energy X-ray source facility, to resolve droplet formation and break down processes occurring inside the combustor during fuel injection.

The data will be used to inform computer-simulated visualizations developed by collaborating researchers from Argonne. Accurate depictions of the fuel’s behavior throughout the combustion process will better inform the development of engines that can accommodate a different range of aviation fuels, including new, sustainably sourced fuels supported by the FAA.

The center includes collaborators from Illinois, University of Illinois Chicago, Northwestern University, University of Wisconsin-Madison, University of Minnesota, University of Michigan, Texas A&M University, and University of North Texas, and is also partnered with the Office of Naval Research, the Air Force Office of Scientific Research, and the Army Research Laboratory’s Vehicle Technologies Directorate, which serves as the government lead and primary funder for the cohort.

“Managing a multi-university effort has been challenging in terms of time and effort,” Lee said. “But it has been rewarding to see continued support from the Department of Defense as well as Congress, and to be part of novel technical breakthroughs in our first five years.”

“I think CUP will leave two legacies. It will have pioneered many of the key technologies that will power the next generation of UAVs for our military, many of which may trickle down to the civilian sector. Equally important is that we will have contributed to establishing a domestic infrastructure for production of these technologies for a secure future.”

Tonghun Lee

Sustainable Aviation Fuels

Alternative fuels are one method scientists are exploring in the quest for greater sustainability. Alex Solecki, a graduate student in Lee’s lab, is using the FAA’s Alternative Jet Fuels Test Database to compile, track and analyze trends in sustainable fuels, with the goal of accelerating their certification, scaling and adoption.

She said sustainable fuels present significant potential for supplementing the use of conventional petroleum-derived jet fuel in the commercial aviation sector and, in fact, are already doing so in small volumes. While these alternative fuels are chemically diverse, they can achieve the same standards as conventional Jet A fuel (a kerosene civil aviation fuel). However, it will take more research and analysis before these synthetic fuels – which are currently certified at blending ratios of 50% or less with conventional kerosene – are accepted by governing bodies, aviation companies and consumers.

“The aviation sector is highly safety oriented. Large-scale changes to something as influential as fuel type will not be seen until an overwhelming amount of scientific support is presented for its suitability,” Solecki said.



Students in lab working on computer

Stephani and the future of hypersonics

Associate Professor and Kritzer Faculty Fellow Kelly Stephani continues to lend her voice to the field of hypersonics. As a recognized expert, she spoke last fall on a panel regarding the future of hypersonic technology and was appointed to the National Academies of Sciences, Engineering, and Medicine Board on Army Research and Development in April of 2022. She also participated in an experts panel that discussed hypersonic weapon capabilities.

Kelly Stephani
Associate Professor and Kritzer Faculty Fellow Kelly Stephani. 

“Once we get students trained in areas of facility operations, instrumentation, diagnostics, analysis, [then] when they are ready to enter the workforce, they bring that to bear and can help to transition academic innovations to enable new capabilities and hypersonic systems,” she said at the time of preparing new generations of engineers to contribute to the field.

Stephani serves as associate director of the Center for Hypersonics and Entry Systems Studies (CHESS), which has project thrusts such as aerothermodynamics, gas-surface interactions, material response, thermal protection systems, and hypersonic environments. She also co-directs the University Consortium for Applied Hypersonics (UCAH), a collaborative network of universities that work with public and private entities to advance hypersonic systems.

Stephani’s research in hypersonics focuses on material behavior—specifically, the quality of response to hypersonic conditions. Her group is particularly interested in materials that can be made to resist forms of degradation, such as oxidation, face transformation, and warping, commonly experienced in high-temperature environments.

Stephani is currently serving as a visiting fellow at Stanford University’s Hoover Institution, an interdisciplinary public policy think tank.

“We need to think about how our own developments and innovations finally play out in how policy is formed and how states decide to maneuver,” she said. “We’re learning a lot from observing what the U.S. is doing with other world leaders and from how those leaders are responding.”

An energy-efficient and fast deicing method for electric aircraft

Electric aircraft in flight

New research from MechSE Professor Nenad Miljkovic shows promising findings for the future of electrified aircraft capability.

Snow and ice removal is crucial for maintaining aerodynamic lift and energy efficiency. Ice buildup on the wings’ edges can disrupt lift while creating additional drag, potentially causing the aircraft to stall. Similarly, ice buildup on propellers can imbalance the blades, leading to excess vibration and reduced thrust.

Nenad Miljkovic
Founder Professor Nenad Miljkovic.

Internal combustion engine (ICE) aircraft are typically equipped with rubber boots that inflate and deflate pneumatically to break up snow and ice accumulation on critical surfaces. Some ICE aircraft also route engine heat to prevent ice from forming. However, electrified aircraft do not have the same onboard mitigation strategies available.

One deicing method Miljkovic is pursuing for electric aircraft – called pulse interfacial deicing (PID) –  involves a localized “pulse” of thermal heat applied directly to the interfacial layer adhering to the ice and frost.

His team is also developing a coating that synergistically combines PID with surface wettability to accelerate ice, frost, and snow removal. The combination of these fundamentally different removal mechanisms proved to be ultraefficient, using 50% less energy input and taking less than five seconds to complete. They plan to scale their strategy to full-sized electrified aircraft.










3D printed phononic materials use geometry to control vibrations and wave propagation.

Metamaterials could revolutionize how aircraft respond to turbulence

Researchers from Illinois, CalTech, University of Pennsylvania, and Boston University are embarking on a new study to determine how various mechanical metamaterials interact with the dynamics of turbulence. Their findings are expected to result in transformative changes to the energy requirements and flight envelope of air-vehicle operation.

Katie Matlack
Associate Professor and Richard W. Kritzer Faculty Scholar Katie Matlack.

Mechanical metamaterials are engineered structures that have unique properties that are not possible with natural materials. However, their effects on turbulent flows around air vehicles is currently unknown.

MechSE Professor Katie Matlack is the PI on the project which was awarded a highly competitive Multidisciplinary University Research Initiative (MURI) grant from the Air Force Office of Scientific Research (AFOSR).

“Many mechanical metamaterials exhibit mechanical and dynamic properties that actually have quite complementary features to fundamental challenges in passive flow control. But this is a highly complex domain that involves many disparate disciplines, so there’s been very few efforts to push that forward until now,” Matlack said.

Concept of FMI of bespoke materials to enable optimal aircraft performance.
Concept of FMI of bespoke materials to enable optimal aircraft performance.

In the process, her team will also establish a new multidisciplinary field – fluid-metamaterial interaction (FMI) – and aim to discover new fluid-structure coupling between innovative materials and critical aerodynamic flows to enable passive control of transition delay, drag reduction, and separation.

Their work will enable vehicles that can safely and efficiently maneuver through complex environments and the researchers ultimately aim to jumpstart the FMI field to enable novel aircraft designs. For the Department of Defense, this research will result in surface/subsurface structural systems to make passive, dynamic flow control within next-generation air vehicles a reality.

Share this story

This story was published October 23, 2023.