A Laser-Interferometric Trajectory-Following System for Determining Forces on Freely-Flying Models in a Shock-Tunnel

摘要

A pair of simple Michelson interferometers with a He-Ne laser as light source were used in a prototype two-point trajectory-following system. Each interferometer provided a measurement arm for following the motion of a reference point on the model, generating a fringe-cycle when the point moved to half-wavelength along the beam incident on the model. Frequency-modulated pulse trains were detected by photodiodes and recorded by a transient recorder. The stored information was played back to a two-pen recorder, enabling displacements versus time and accelerations of the reference points to be determined. The system was used for following motions in the pitch-plane of ridge-delta models flying under weak restraint in a shock tunnel.