Human space mission architecture risk analysis

A human space flight mission is extremely dynamic in nature. A spacecraft faces multiple physical environments and is exposed to dramatically different hazards over the typical phases of a mission: from a minutes-long ascent phase, to a months-long orbital phase, and then an hours-long entry, descent and landing phase. The space transportation vehicle´s configuration also changes as each of the stages of the launch vehicle´s engines are ignited, burned, turned off, and jettisoned, with new stages and engines taking over the thrusting of the vehicle until the spacecraft is separated from the launch vehicle. Once in orbit, the spacecraft performs its orbital tasks and then returns to earth for safe landing of the astronauts. All the changes in the physical environments encountered during the mission and the response of the system to failures or changes in the configuration of the vehicle call for a modular, dynamic probabilistic risk model that integrates the modeling pieces and faithfully tracks the entire mission timeline in order to understand the risks to the crew across all mission phases. Using a flexible modeling framework that is capable of incorporating various levels of data fidelity, modeling inputs, and timescales allows for a risk analysis methodology that grows with the maturity of the system´s design definition while capturing the risk drivers at the right levels throughout the mission.