ABSTRACTThe period since 1970 has been characterized by an intense push to develop new inertial navigation technology. Inasmuch as theperformancerequirements for nearly all of today's missions can be satisfied by instruments that were available 25 years ago, it is reasonable to ask what has driven this creative intensity. The answer to this question also points the way to the probable path of technology development in the next 25 years. The introduction and refinement of dry‐tuned two‐degree‐of‐freedom gyroscopes and the emergence of optical gyroscopes, resonator gyros, quartz resonant accelerometers, and micromachined silicon instruments have been driven by the goal of reducing the life‐cycle cost of ownership of inertial systems, and by the need for rapid convergence of the navigation system to stable operation after turn‐on. Combine these advances with the annual increases in computational power available per unit volume (which supports the compensation of calibratable sensor errors and integration with external sensors, such as GPS), and the trend to smaller, lighter, less‐expensive systems is certain to continue well into the