Measurements of density fields in micro nozzle plumes in vacuum by using an enhanced tomographic Background Oriented Schlieren (BOS) technique

The measuring principle of BOS is based on light ray deflection along density gradients normal to the lines of sight. For high precision BOS measurements in a small field of view around a micro nozzle exit a long-distance microscope (LDM), a DMD projector, a high resolution CCD camera and evaluation software based on crosscorrelation for determining displacement vector fields have been used in the propulsion laboratory of ESA-ESTEC in Noordwijk. The density distribution inside a micro nozzle free jet of nitrogen into a vacuum chamber has been investigated using optical tomography for measurement data achieved with BOS.