Dynamic Inertia Measurement Method (DIM)

Critically important inertia measurements are complex and expensive to obtain due to the extensive fixturing and custom instrumentation of conventional techniques. This research effort has validated a more efficient, less risky, and faster inertia measurement technique for aerospace vehicles. The dynamic inertia measurement method is based on conventional ground vibration testing methods, which are routinely performed in other types of aircraft testing. The basic concept is to compute the inertia properties and center-of-gravity location of an object by measuring all forces acting on the object and the rigid body motion caused by these forces. Work to date: All testing has been completed and two technical papers describing the results have been published. The DIM method was implemented to measure the mass properties of the test article, as were then the conventional pendulum oscillation methods, to compare results, level of effort, and costs. The DIM method showed favorable results for the center of gravity and moments of inertia; however, the products of inertia showed appreciable disagreement with analytical predictions. Looking ahead: he next project phase, testing on an aerospace vehicle, has not yet been funded. Partner:  ATA Engineering, Inc. provided software and support for the testing. Benefits Less risky: Does not require the vehicle to be suspended, reducing risk and equipment needs Less expensive: Eliminates the complex and expensive fixturing and equipment used in conventional measurement techniques Faster: Dramatically decreases testing and approval times by weeks or even months Applications Airplanes and space vehicles (capsules and lifting body spacecraft) Automobiles and other large terrestrial vehicles