Holographic interferometry can be used to visualise transparent flows. The interference fringes (light and dark bands) bend where there are gradients in the flow density. This image shows hypersonic flow over a simulated space craft (the sphere to the left of the image) followed by an attached “ballute” balloon parachute used to slow the vehicle as it enters a planetary atmosphere. The original image was recorded holographically in the X2 Expansion Tube. White light is used to reconstruct the image which is then recorded on a digital camera. 

School of Maths and Physics