 Building a computer with the required performance, size and weight demanded the use of transistors, which were at that time very expensive and not very reliable.Earlier efforts to use transistorized computers for guidance, BINAC and the system on the SM-64 Navaho, had failed and were abandoned.The Air Force and Autonetics spent millions on a program to improve transistor and component reliability 100 times, leading to the "Minuteman high-rel parts" specifications.