490. A Single Point Center of Gravity and Weight Measuring System for Airborne Ejection Launched Missiles
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Paper
Abstract
This paper describes and discusses a new system of center of gravity and weight determination for missiles. An order of magnitude improvement in center of gravity location accuracy is achieved. A new moment measuring device using semiconductor strain gauges is the most important factor in achieving the increased accuracy.
The center of gravity locating and weight measuring systems with which the author is currently most familiar serve to establish the center of gravity position and weight of airborne missiles which are in the general size of 800 to 1200 pounds. These missiles are supported on, and ejection launched from, an airplane at two points. The pitch rate is critical for safe separation and is very sensitive to small variations in center of gravity location. The flight test program includes establishing an acceptable tolerance of variation in missile center of gravity.
The new system discussed in this paper provides separate and independent measurements of missile unbalanced moment and missile weight. A ‘conventional approach’ system which has been in use for some time employs four load cells, spaced 10 inches apart in a square pattern, connected to an automatically summing readout instrument.
Because of the fact that separate direct and independent readings of missile unbalanced moment and missile weight are provided in the new system the sources of error can be isolated and analyzed more thoroughly, and the center of gravity effect of errors in the weight measurement is reduced to a negligible amount. To provide numerical simplicity in the error analysis in this paper, it is assumed that the true weight of missiles being measured is 1000.00 pounds.
