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Exoatmospheric Intercepts Using Zero Effort Miss Steering For Midcourse Guidance
Brett Newman*
Abstract
The suitability of proportional navigation, or an equivalent zero effort miss formulation, for exoatmospheric intercepts during midcourse guidance, followed by a ballistic coast to the endgame, is addressed. The problem is formulated in terms of relative motion in a general, three dimensional framework. The proposed guidance law for the commanded thrust vector orientation consists of the sum of two terms:1) along the line of sight unit direction and 2) along the zero effort miss component perpendicular to the line of sight and proportional to the miss itself and a guidance gain. If the guidance law is to be suitable for longer range targeting applications with significant ballistic coasting after burnout, determination of the zero effort miss must account for the different gravitational accelerations experienced by each vehicle. The proposed miss determination techniques employ approximations for the true differential gravity effect and thus, are less accurate than a direct numerical propagation of the governing equations, but more accurate than a baseline determination, which assumes equal accelerations for both vehicles. Approximations considered arc constant, linear, quadratic, and linearized inverse square model. Theoretical results are applied to a numerical engagements scenario and the resulting performance is evaluated in terms of the miss distances determined from nonlinear simulation.
*Dr Newman is a Plight Dynamics and Control Engineer with Orbital sciences Corporation/Space Data Division, 3380 South Price Chandler. Arizona 85248 Member AIAA.