Inverse estimation of the Kentucky Re-entry Universal Payload System (KRUPS) flight trajectory

The Kentucky Re-entry Universal Payload System (KRUPS) is a small spacecraft developed to provide flight data during atmospheric re-entry. The KRUPS capsules made a historic re-entry to the Earth’s atmosphere in 2021, and this work details the reconstruction of the flight trajectories by inverse estimation based on the flight data. A trajectory modeling program is used with a one-dimensional material response solver to generate a prediction of the stagnation wall temperature of the KRUPS capsule during the Kentucky Re-Entry Probe Experiment, the orbital flight launched from the International Space Station. These temperature results are compared to the temperature data obtained during the mission, and the initial parameters of the trajectory simulation are optimized to find the best estimated trajectories. The inverse estimation is performed in three ways; by assuming radiative equilibrium at the wall, by estimating the wall temperature after the trajectory simulations are first performed, and by coupling the trajectory and one-dimensional material response solver. Finally, the best estimated trajectories are compared against simulations performed using a computational fluid dynamics and a three-dimensional material response solver, the Kentucky Aerodynamics and Thermal-response System Fluid Dynamics and Material Response modules, and comparing the thermal response to flight data. It is observed that all approaches converge to a possible ejection of the KRUPS capsule into the Earth’s atmosphere in the range of 35 to 40 km.