Takane Imada

IMU-DM Integrated Navigation and Terminal Reentry Guidance for Accurate Guided Reentry Flight

High-accuracy reentry guidance has become increasingly important for reentry capsule spacecraft. For example, in an advanced concept study of the Japanese manned reentry capsule, an attempt has been made to land the capsule on the Japanese mainland. For this purpose, the targeted reentry guidance accuracy is to within 1 km at the point of parachute deployment. To meet this high requirement, we have been developing accurate real-time prediction guidance using numerical integration for reentry spacecraft. This guidance method is an explicit guidance law using real-time numerical integration to predict the accurate range during reentry flight, which already includes IMU-GPS integrated navigation, on-orbit alignment by star tracker and measured wind information utilization for range prediction. However, reentry guidance error analyses we did using those guidance methods showed that we need to made more effort to meet the targeted reentry guidance accuracy of 1 km, particularly given the considerable residual alignment error of inertial navigation and unpredictable upper-level wind variation. Accordingly we added the IMUDM (Drag Measurement) integrated navigation and improved terminal reentry guidance to the accurate real-time prediction guidance using numerical integration for reentry spacecraft. This paper outlines the real-time prediction guidance using numerical integration (REPNI Guidance), describes the methods and performances of IMU-DM integrated navigation and improved terminal reentry guidance and shows guidance accuracy using those methods by guidance error analyses and Monte Carlo simulations.

Aerodynamic Oscillation and Attitude Control Analysis for Reentry Capsule using OREX Flight Data and Wind Tunnel Data

Stable attitude control is essential for accurate reentry capsule guidance, and aerodynamic instability of a transonic region has been recognized as a key issue. To address this issue, we have been studying stable attitude control for lifting reentry capsule during reentry flights. As the first step of the study, we evaluated the aerodynamic stability and controllability of the Japanese ballistic reentry capsule named OREX (Orbital Re-entry EXperiment). The study compares reentry flight results with simulation results base on aerodynamic coefficients obtained from wind tunnel tests and aerodynamic damping coefficients modeled from wind tunnel tests and existing aerodynamic data-bases. We have also been analyzing the aerodynamic stability and controllability of a lifting reentry capsule by conducting attitude control simulations using aerodynamic damping coefficients estimated from the wind tunnel tests for dynamic stability characteristics. This paper describes the OREX system configuration, aerodynamic damping coefficients, reentry flight results, and a comparison of results obtained from flight data and simulations. Moreover we present the lifting reentry capsule model, aerodynamic damping coefficients estimated from wind tunnel tests, and comparison of results from wind tunnel test data and simulations.