MAGNETIC SYSTEM FOR LAUNCH TUBE LINEAR POSITION MEASUREMENTS

A MEANS IS REQUIRED TO MEASURE THE CLEARANCE BETWEEN THE SURFACE OF A MISSILE AND ITS LAUNCH TUBE DURING A LAUNCH, TO AN ACCURACY OF THE ORDER OF 2%. THE MEASUREMENT MUST REMAIN UNPERTURBED BY LARGE FLUCTUATIONS IN ENVIRONMENTAL TEMPERATURE, AND IN THE DENSITY AND ELECTRICAL CONDUCTIVITY OF THE GASES IN THE TUBE DURING LAUNCH. A REVIEW OF MEASURMENT TECHNOLOGIES SUGGESTS THAT A MAGNETIC SCHEME IS MOST LIKELY TO SATISFY ALL REQUIREMENTS. SMALL BEADS OF A HARD PERMANENT MAGNETIC MATERIAL (SUCH AS SMCO5) ARE MOUNTED IN A DISTINCTIVE PATTERN ON THE MISSILE SKIRT. A MAGNETIC SENSOR OF SUFFICIENT LOWFREQUENCY SENSITIVITY MEASURES THE MAGNETIC FIELD OF THE BEADS AS THE MISSILE PASSES BY. THE FIELD AMPLITUDE IS STRONGLY DEPENDENT UPON THE RANGE BETWEEN THE MAGNETIC SOURCE AND SENSOR. FOR PHASE I WE PROPOSE TO TEST ANALYTICAL CALCULATIONS OF SYSTEM PERFORMANCE BY CONSTRUCTING A MOCKUP TEST BED AND PERFORMING A SERIES OF MAGNETIC MEASUREMENTS AS A FUNCTION OF RANGE AND SPEED DOWN THE TUBE.