Trajectory Shaping for Quasi-Equilibrium Glide in Guided Munitions

Report No. ARL-TR-8749
Authors: Luisa D Fairfax, JD Vasile, Luke S Strohm, and Frank E Fresconi
Date/Pages: August 2019; 32 pages
Abstract: The objective of this research is to extend range, increase impact velocity, decrease time-of-flight, and reduce spikes in thermal loading in long-range munitions. This is done by commanding munitions to quasi-equilibrium glide at an optimum height, which cancels out the phugoid motion. The phugoid motion is a longitudinal oscillatory mode in which the munition first pitches up as it climbs and slows in speed followed by pitching down and speeding up at a near-constant angle-of-attack. It is more pronounced in long-range flights in which the air density is lower at atmosphere, allowing the munition to reach higher altitudes before slowing down. Quasi-equilibrium glide is adapted from space entry vehicles and is typically used to reduce heating effects of entry into the atmosphere. Thermal loads and temperature effects are also explained. Monte Carlo simulations are shown on an example munition for maximal range and terminal guidance scenarios. Trajectory shaping is also used for imperfectly located targets. A worst-case scenario is shown in which the target is imperfectly located at launch. In this case, impact velocity is improved by 56.5%, and range error is decreased by 86.8% in a long-range guidance scenario to 250 km. This report is organized as follows: first, the introduction outlines past work regarding munition characterization and control and the phugoid motion control; second, the governing equations are outlined; third, GENEX and the baseline gliding and terminal guidance are outlined followed by the maximum glide height, trajectory shaping, evaluation, maximal range results, terminal guidance, and a conclusion.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2019