A small but significant increase in the price of reaction and momentum wheels would not cause a significant number of customers to substitute other products. The development, production, and sale of reaction and momentum wheels for the U.S. military and commercial space industries is a line of commerce and a relevant product market within the meaning of the Clayton Act. Inertial Systems 19. A typical IMU includes three accelerometers and three gyroscopes. Accelerometers measure the linear acceleration of a vehicle, which is used to determine vehicle velocity and vehicle position.
Gyroscopes measure the angular rate of rotation of a vehicle.
From these measurements, a computer can calculate the vehicle's position and heading. Each of these gyroscopes may substitute with the others as an input into an IMU, depending on performance, cost and size requirements. MRGs include gas, spinning mass and other comparable mechanical gyroscopes. Mechanical gyroscopes are utilized in high accuracy space applications, strategic missiles, and tactical munitions. An RLG uses two laser beams housed in an optical cavity with a set of highly reflective mirrors.