Exoatmospheric Intercept Guidance Based on Relative-Motion Control with Respect to Zero-Effort Orbit

Exoatmospheric intercept plays a crucial role in strategic defense. However, existing approaches for exoatmospheric intercept guidance primarily rely on either proportional navigation or Lambert’s problem solution, which needs continuous relative measurements or requires constant orbit corrections due to its sensitivity to perturbation forces. To address these limitations, this paper proposes a novel guidance scheme based on relative-motion control. First, by introducing the zero-effort orbit as a reference orbit, the intercept problem is transformed into an equivalent relative-motion control problem with respect to the zero-effort orbit. The relative-motion dynamics model is adopted to analytically solve the velocity-to-be-gained vector, which avoids the iterative computation in the Lambert routine. Then, the guidance scheme is established, which generates a command thrust vector aligned with the velocity-to-be-gained vector in each guidance period. Through feedback control, the desired velocity is incrementally achieved until the velocity-to-be-gained vector becomes zero, ensuring accurate interception. Compared with the existing exoatmospheric intercept guidance methods, the presented method improves 1 or 2 orders of guidance accuracy in the low-Earth orbit intercept mission and 3 orders of guidance accuracy in the high-Earth orbit intercept mission, which are practical options for engineering applications.