Light Field Imaging of Spectral Emissions from Particles and Gas Phases in Reacting Supersonic Flows

Missile plumes emit electromagnetic radiation that can alert adversaries to their presence, cause troublesome thermal loads to the missile, or temporarily blind the pilot of the release aircraft. Techniques are needed to measure the three-dimensional (3D) plume structure and associated spectral emission to obtain a better understanding of the physical processes governing plume radiation. A method involving plenoptic imaging is proposed for measuring volumetric distributions of scalar quantities in a missile plume that directly impact the spectral emission at near infrared, visible, and ultraviolet wavelengths. The program objectives include developing an algorithm for image reconstruction from light field data that is optimized for a continuous scalar field, constructing a prototype plenoptic imaging system for missile plumes for measuring temperature, particle mass concentration, emission intensities of the excited state radicals OH*, CH*, and C2*, and developing a multispectral version of the prototype that enables simultaneous measurements of up to three scalars. The prototype systems will be demonstrated in laboratory flames, a supersonic particle-laden afterburning plume, a small scale (~2-in. exit diameter) rocket engine, and a large scale (8-in. exit diameter) rocket engine. The effort should result in a new capability for volumetric imaging of plumes.