Emission & Absorption Spectroscopy Sensors for Hypersonic Flight Control

The long-term goal of this ULI project is to develop flight-ready sensors for diagnosing internal and external hypersonic flows. Together with dedicated data processing and robust sensors, these sensors will enable tip-to-tail derivation of off-surface and on-surface aerodynamic parameters necessary for controlled hypersonic flight.

Our Purdue University led team includes the University of Virginia and Hampton University along with two small businesses: Sydor Technologies and Innoveering. Our team is focused on combining two complementary optical measurement techniques – optical emission spectroscopy (OES) and laser absorption spectroscopy (LAS) – into a control-ready sensor suite for hypersonic flights. The OES sensors will be used to monitor both internal and external hypersonic flow conditions, while the LAS sensors will be used for internal flow diagnostics.

One of the main goals of this project is making OES sensors flight‑ready for hypersonic vehicles. Current OES sensors are not sufficiently robust, and all of the components associated with an OES sensor will need to be miniaturized for use in hypersonic vehicles. Additionally, to gather real-time flow parameters, the OES sensors will have to process data quickly and reliably, which the project hopes to do by developing on-line data processing routines and integrating machine learning into the control software.

Another main goal of the project is to further develop LAS sensors for hypersonic flight. Existing LAS sensors employ near-infrared wavelengths, which unfortunately means that they can only detect a few species—mainly water and oxygen—and gas conditions (e.g., temperature) thereof at the scales relevant to internal flow paths. The project aims to integrate mid-infrared LAS sensors to improve the measurement sensitivity, measure additional species of interest (like carbon monoxide and carbon dioxide), measure additional hypersonic flow parameters such as temperature and air mass flow rate, and increase their measurement rates.

Both the OES and LAS sensors will be integrated and tested on a closed-loop feedback control system for internal and external hypersonic flow paths to show viability of the new sensors for measuring hypersonic flows.

The final goal of the ULI project is to improve education about hypersonic vehicles and hypersonic sensor technology. A diverse and well-trained workforce is vital to the aerospace industry, particularly for hypersonic systems. The team’s planned outreach activities include educational social events around the theme of hypersonic systems for students at all universities involved, internship and research positions for graduate and undergraduate students, and integrating a Faculty in Residence Program where professors and graduate students can work with associated universities for a summer or a semester to improve collaboration efforts throughout the project.