gerald-weinberg managed operating systems development for NASA's Project Mercury (1959-1963) at ibm-federal-systems-division. Mercury was the United States' first human spaceflight program, putting astronauts into orbit. The software demands — reliability, real-time performance, life-critical consequences — gave Weinberg direct experience with the gap between how programming was theorized and how it actually happened under pressure. These observations became the empirical foundation for psychology-of-computer-programming-1971.