Helical electromagnetic launchers for acceleration calibration

Abstract

The design, construction, and testing of 300 mm barrel length × 40 mm diameter bore solid-projectile helical electromagnetic launcher (HEML) which is subsequently used to calibrate an accelerometer via the absolute calibration method is presented and discussed. The HEML barrel is constructed of G-10 epoxy-fiberglass and is able to accelerate a 600 gram projectile (consisting of projectile and accelerometer payload) to 10 meters per second. Other components of the experimental arrangement include a 19.25 kJ capacitive pulse forming network (PFN) to power the HEML, a command module (CM) to control charging and firing of the PFN, and a calibration table (CT). The HEML is evaluated in terms of peak acceleration, acceleration repeatability, and launcher lifetime. The HEML has been successfully fired over 250 times with only minimal periodic cleaning. From the 250 successful firings, a 75-shot test sequence is used to evaluate the HEML's performance, lifetime, and repeatability in this application. The mean acceleration was 500 gee with a sigma of 15 gee (3%) with standard process statistical variables remaining above 2 at ±100 gee (20%). Experimental data is compared to conventional accelerometer data. The results show that the HEML is capable of meeting the performance requirements and standards of a conventional accelerometer tester. Methods to improve this technology is also presented and discussed.