Research
Research Focus: Applications of photonics, lasers, optics and atomic physics to space propulsion and power, high-repetition rate data-rich diagnostics and sensors for hypersonic flight, and plasmadynamics relevant to propulsion and flow control.
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.
The flight environment is constantly changing due to local weather and atmospheric phenomenology in the troposphere and stratosphere. During flight, variations in the wind speed and direction, gusts and turbulence can perturb the flight platform and make vehicle control and guidance challenging. 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. Much of our work relies on analysis of backscattered light with atomic and molecular vapors, focusing on methods that increase the rate and precision of velocimetry and aerosol characterization. In addition to bench testing, the group utilizes our ourdoor bistatic LIDAR capability known as the Michigan Laser Atmospheric Sensing Experiment (M-LASE).
Light carries both energy and momentum, enabling complex interactions with both solid and gas-phase media. Our group explores new methods that amplify and extend the reach of optically-based space propulsion and power for applications such as station keeping, precision formation flying, cislunar and deep space propulsion, and in-situ resource utilization. In its simplest form, light pressure is simply equal to twice the incident laser power divided by the speed of light. We are developing concepts that promise to enhance this by 3 - 5 orders of magnitude to produce transformational capabilities for moving and operating in space, even without propellant!
A rendering of the self-guided beam propulsion technology concept developed by our group under funding from the NASA NIAC and Lockheed Martin.
Mie scattering from an under-expanded carbon dioxide jet imagined at a 250 kHz rate.
Atmospheric reentry and hypersonic environments present incredible challenges for modeling, ground experiments, and operational flight. The quickly changing and highly non-equilibrium state of the flow requires complex and expensive modeling solutions that are only validated through experiments with great difficulty. As part of this effort, our research group develops and applies new high speed diagnostic capabilities aimed at providing a better understanding of hypersonic and reentry phenomenology, including high-speed measurements of thermal and chemical non-equilibrium behind shocks, near surfaces, and in complex 3D geometries.
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, high enthalpy flow. As part of this effort, we have developed new approaches for multi-dimensional, time-resolved imaging of density perturbations which affect optical propagation and imaging.
An image of intensity fluctutions due to beam propagation through a turbulent jet.
Fluorescence from a laser-guided electrical discharge in Mach 5.8 flow for applications to flow control.
High speed vehicles designed for high maneuverability are inherently flown at the limits of stability. Therefore, rapid aerodynamic control is needed to maintai stability and enable rapid maneuvering and compensation for changes in the flight environment such as gusts and crosswind. This work investigates the use of localized, energetic, and high rate optically controlled discharges to study excitation of flow instabilities, bistability, transition control, flameholding and aerodynamics relevant to hypersonic flight.