A Methodology for Determination of Entry, Descent, and Landing Design Performance Margins of Spacecraft Landing on Planetary Bodies

Abstract

Design of a spacecraft and mission architecture that provide adequate performance margin is essential to successful spaceflight. This is particularly true for the Entry, Descent and Landing (EDL) phase of a landed mission. The quantification and management of performance margins is a key aspect for design of a successful EDL phase. In this research, a methodology for quantifying design performance margin, called Target Margin, is developed for EDL systems for planetary landing, using as a starting point a seed methodology utilized by NASA’s InSight Project, a Mars lander that performed a landing in 2018. The methodology presented here utilizes Monte Carlo analysis, Monte Carlo filtering and Design of Experiments (DOE) techniques to identify modeling input parameters that most influence EDL performance metrics. The methodology then provides a framework for assessing confidence in modeling parameters to feed a quantification of Target Margin that utilizes second-order, DOE-based regression modeling. Assessment of epistemic and aleatory (reducible and irreducible) uncertainty is also included, to reveal where uncertainty in modeling might be reduced during a project lifecycle. This approach is applied to the InSight EDL system and results are compared to the originating InSight seed methodology, showing that the methodology results in more conservative, more robust quantification of Target Margin than the seed methodology. Using InSight landing flight data, the Target Margin resulting from application of the methodology to InSight is compared to as-flown EDL performance margin revealing InSight landed with healthy margin, and EDL simulation modeling confidence is assessed in light of flight observations. Three sensitivity analyses were performed, the first using the methodology to establish bounding Target Margin based on low and high modeling confidence; the second is an examination of Target Margin quantification resulting from applying the methodology to a simulated InSight early project lifecycle EDL system; and the final sensitivity analysis performs a simple assessment of two modeling confidence weighting designs, showing generally low sensitivity to the designs. The methodology is successfully applied to the InSight EDL system, and in the process, findings identified for future work to improve the methodology for application to other planetary landings.