A Laser-Interferometric Trajectory-Following System for Determining Forces on Freely Flying Models in a Shock-Tunnel,
QUEEN MARY COLL LONDON (ENGLAND) DEPT OF AERONAUTICAL ENGINEERING
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A prototype, two-point trajectory-following system is described, which uses a pair of simple Michelson interferometers having the same He-Ne laser as a light source. Each interferometer provides a measurement arm which is used to follow the motion of a reference point on the model, a fringe-cycle being generated when the reference point moves a half-wavelength along the beam incident on the model. Each set of frequency-modulated pulse trains is detected by a photodiode and recorded by a transient recorder. The stored information is then played back to a two-pen recorder from which the displacements versus time and hence the accelerations of the reference points can be determined.