1 Advantages of Heritage Atlas Systems for Human

The current Atlas V launch vehicle has been developed through evolutionary enhancements to heritage vehicles dating to the 1960s. By building on previous configurations and blending advanced and proven technologies, Atlas V has achieved 100% mission success. NASA’s commercial crew development (CCDev) program provides an opportunity to bring this established approach into the arena of crewed spaceflight. In contrast to designing a new launch vehicle, evolving a heritage vehicle requires that we develop a method to meet emerging requirements with flight-proven systems or components. Assessing potential changes involves weighing the understood benefits of a mature design against the perceived advantages of a new design. This process can be complicated by immature requirements, difficulty in quantifying the relative reliability of new and heritage hardware, and complication in identifying and evaluating all potential system-level impacts due to the change. The advantages of heritage systems, however, outweigh these challenges as illustrated with specific examples. Nomenclature CCDev = commercial crew development DER = design equivalency review EDS = emergency detection system ICBM = intercontinental ballistic missile LH2 = liquid hydrogen LO2 = liquid oxyge