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The Atlas and Delta Launch Vehicle Families have enjoyed a rich history as trusted vehicles for launch of critical NASA Space Exploration missions. During that course of space launch development, the Atlas and Delta Expendable launch vehicles have matured well beyond the early days of spaceflight. This paper addresses the attributes of the Atlas V and Delta IV Heavy Expendable launch vehicles that makes them distinctively qualified to be highly reliable, robust earth-to-orbit transportation solutions for Crew launch to Low Earth Orbit (LEO). This paper details the Evolved Expendable launch vehicle system compliance to Human Rating requirements defined by NASA Standard 8705.2B "Human-Rating Requirements for Space Systems." In addition, the paper compares and contrasts various requirement options, some of which may drive highly complex, unreliable, and costly design solutions.Both Atlas and Delta have the unique capability to demonstrate the implementation of Human Rating requirements by validating designs on numerous uncrewed launches. The EELV flight rate of uncrewed missions quickly builds sufficient history to rely on flight demonstrated reliability, rather than paper reliability. Demonstrating these systems has the benefit of increasing reliability through commonality with commercial and government launches, in addition to continuing vehicle characterization due to the experience gained from higher flight and production rates. The Atlas and Delta EELVs are mature systems with demonstrated design robustness and processes discipline that provides a highly reliable, robust solution for Crew launch to LEO.

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The Atlas Expendable Launch Vehicle Program has been studying safe abort requirements and is being considered as the logical choice to provide flight-proven, low risk, low cost Earth to Orbit transportation for a number of commercial human spaceflight applications. Key to the success of these commercial entrepreneurial endeavors is to ensure that the Atlas system provides the utmost abort safety by providing insight into the performance and health of the launch vehicle systems. Atlas has designed key aspects of an Emergency Detection System (EDS) and has a test plan in place to begin demonstration of this system. This Paper describes the rationale that was used to baseline the set of safety critical measurements that are required that make it a critical addition to the flight-proven Atlas system to enable commercial human spaceflight.The EDS will be added as a bolt-on kit to the standard Atlas and will be used to detect imminent vehicle failures and to initiate an abort. The EDS will monitor the launch vehicle, detect anomalous conditions, safe the vehicle, and send the abort signal. As a bolt-on kit, the EDS will not affect the proven Atlas V vehicle design. The Paper will provide insight into the detailed fault coverage assessment process that was performed to identify the safety critical failure modes, the time for those failures to result in a catastrophic situation, and the primary, backup & corroborating measurements that would be monitored for those failure modes. This analysis formed the set of measurements that will be monitored by the EDS. This analysis was not unusual for Atlas, as the building blocks of an EDS system for Atlas are flying today. For example, Atlas currently uses extensive RD-180 engine health checks that occur prior to liftoff. There are Pogo detection and correction algorithms and propellant utilization optimization software in place today.