Research

Research Focus: Our group pursues a broad portfolio of research efforts leveraging photonics, lasers, optics and atomic physics to solve contemporary challenges in space propulsion and power, to develop novel sensors for supersonic and hypersonic flight, and to understand plasmadynamics relevant to propulsion and high-speed flow control. Below you will find more detailed descriptions and highlights of our work.

Space Power & Propulsion

Emerging photonic technologies — such as laser and beam-driven propulsion, cavity-enhanced thrust generation, and directed energy — have the potential to transform how we power and maneuver spacecraft across Earth orbit, the Moon, and beyond. Our group is also working to understand how lasers can facilitate in-situ resource utilization through laser ablation, propulsion, reducing reliance on conventional propellants and enabling more sustainable and flexible operations in space. Together, these new technology paths can provide a foundation for the next generation of agile satellite networks and proliferated mission architectures for space exploration.

A rendering of the self-guided beam propulsion technology concept developed by our group under funding from the NASA NIAC and Lockheed Martin.

C.M. Limbach and H.P. Morgan, “Phenomenology and Capabilities of Mutually Guided Laser and Neutral Particle Beams for Deep Space Propulsion,” Acta Astronautica 197, 298-309 (2022) https://doi.org/10.1016/j.actaastro.2022.04.006
A. Castillo, P. Kumar, C.M. Limbach, K. Hara, “Mutually Guided Light and Particle Beam Propagation,” Scientific Reports 12, 4819 (2022). https://doi.org/10.1038/s41598-022-08802-z
H.P. Morgan, W.L. Hodges, R.D. Jillapalli, C.M. Limbach, “Characterization of an Effusive Rubidium Atomic Jet Source by Tunable Diode Laser Absorption Spectroscopy,” AIAA SciTech 2021 Forum, Virtual (AIAA 2021-0048). https://doi.org/10.2514/6.2021-0048

Laser and Optical Sensing

Hypersonic flight and atmospheric entry constitute some of the most challenging flight environments ever pursued, where extreme thermophysical conditions lead to flow phenomena such as intense shock waves, shock-turbulence interaction, surface ablation, and thermochemical non-equilibrium that push the limits of both modeling and experimentation. Accurately capturing and understanding these interactions requires advanced simulations and experiments that are often costly and technically complex. To address these hurdles, our research group develops and deploys cutting-edge high-speed and non-intrusive diagnostic techniques to reveal the underlying physics of high-enthalpy flows—measuring velocity distributions, species concentrations, and thermal and chemical non-equilibrium in shock layers, near surfaces, and within intricate 3D geometries.

Mie scattering from an under-expanded carbon dioxide jet imaged at a rate of 250,000 fps.

J.C. Pehrson, B.S. Leonov, R.B. Miles, M.T. Lakebrink, C.M. Limbach, “Wall-normal FLEET Velocimetry in a Canonical Hypersonic Inlet,” AIAA SciTech 2023, National Harbor, MD, AIAA 2023-0220. https://doi.org/10.2514/6.2023-0220
B.S. Leonov, T.S. Dean, R.D. Bowersox, C.M. Limbach, R.B. Miles, “High-Speed Planar Laser Induced Fluorescence Investigation of Nitric Oxide Generated by Hypersonic Mach Reflection for CFD Validation,” Physics of Fluids 35, 066102 (2023) https://pubs.aip.org/aip/pof/article/35/6/066102/2893918

Postdoctoral researcher Rishav Choudhary and Professor Limbach working on the Michigan Laser Atmospheric Sensing Experiment (M-LASE) on the roof of the François-Xavier Bagnoud Building.

Optical Air Data and Remote Sensing

The flight environment is constantly changing due to local weather and atmospheric dynamics in the troposphere and stratosphere. During flight, variations in the wind speed and direction, gusts, and turbulence can perturb the flight vehicle and pose challenges to vehicle guidance, navigation and control. Our group investigates the design and testing of novel optical and laser sensors to probe the flight environment and provide real-time measurements of flight conditions (air data) for a range of applications include vehicle control, sonic boom mitigation, and flight test experiments. In addition to bench testing, our group utilizes an outdoor bistatic LIDAR known as the Michigan Laser Atmospheric Sensing Experiment (M-LASE).

M. Hetlage, C.M. Limbach, “"Experimental and Analytical Evaluation of an Active Barium Vapor Notch Filter Functioning at 355 nm," Applied Optics. 61, 4591-4601 (2022). https://doi.org/10.1364/AO.457971

Aero-Optics and High-Speed Imaging

Flight sensors and imaging systems always look through the airflow surrounding the vehicle, which can be characterized by unsteady shock structures and turbulence. To better understand these effects and their influence on active laser sensors, our group uses numerical beam propagation tools and advanced experimental techniques to quantify aero-optic effects in both low and high-speed flow, including high enthalpy flow. As part of this effort, our group is developing new approaches for multi-dimensional, time-resolved imaging of density perturbations which affect optical propagation and imaging.

A 50,000 fps video of five simultaneous view angles of an under-expanded jet obtained through a technique we call HiFleye based on the similarity with a fly's eye.

C.M. Limbach, “Wavefront Retrieval from Irradiance Measurements using Inverse Design Methods,” AIAA SciTech 2023 Forum, National Harbor, MD, AIAA 2023-0164. https://doi.org/10.2514/6.2023-0164
Kuldinow, D., Hara, K., Morales, D., Limbach, C.M., “Numerical Simulation of Laser and Particle Coupled Beam Propagation,” 2019 AIAA Propulsion and Energy Forum and Exposition, Indianapolis, IN (AIAA 2019-3803). https://doi.org/10.2514/6.2019-3803
G.E. Erickson, J. Creel, F. Koelling, R.B. Miles, C.M. Limbach, “Laser Scintillation Measurement in a Controlled Turbulent Environment,” AIAA SciTech 2022 Forum, San Diego, CA & Virtual, AIAA 2022-0985. https://doi.org/10.2514/6.2022-0985

Fluorescence from a laser-guided electrical discharge in Mach 5.8 flow for applications to flow control. Laser is focused vertically on the left, upstream of the diamond channel.

Optically Controlled Plasmas for Flow Control and Combustion

High speed vehicles designed for high maneuverability are inherently flown at the limits of stability. Therefore, rapid aerodynamic control is needed to maintain stability and enable rapid maneuvering and compensation for changes in the flight environment such as gusts and crosswind. The short residence time of fuel in air-breathing propulsion - such as ramjets and scramjets - also requires fast control of the flame and shock train dynamics, including the avoidance of unstart. This work investigates the use of localized, energetic, and high rate optically controlled discharges to study the excitation of flow instabilities, bistability, transition control, flame holding and aerodynamics relevant to hypersonic flight and propulsion.

C.M. Limbach, L. Martinelli and R.B. Miles. “Adjoint Optimization of Sources in Steady, Supersonic Flow: Energy Addition,” AIAA Journal, Vol. 51, No. 10 (2013). https://doi.org/10.2514/1.J052357
C.M. Limbach and R.B. Miles. “Adjoint Optimization of the Spatial Profile of Steady Energy Deposition for Supersonic Drag Reduction,” 45th AIAA Fluid Dynamics Conference, AIAA Aviation, (AIAA 2015-2466). https://doi.org/10.2514/6.2015-2466
K.T. Ruggles, R.B. Miles, N.R. Tichenor, C.M. Limbach, "Dual-Mode Energy Deposition for Hypersonic Aerodynamic Control," AIAA Aviation Forum, AIAA 2024-4596 https://doi.org/10.2514/6.2024-4596

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