A propainfotainment film from 1963 describing the development of the Minuteman ICBM.
[youtube WmSUoVJ1im0]
Point of note: 1963 is 51 years ago. With all the advances in the last half century, America still relies on the Minuteman. Since the Minuteman was developed, we also developed the Midgetman and Peacekeeper ICBMs… and got rid of them.
Also of historic note: when the Minuteman was developed, a lot of components that, were they to be developed today, would be digital were then analog. The safe-and-arm for the solid rocket motors was essentially a heavy chunk of clockwork. The S&A simply served the purpose of making sure than an accidental electrical or mechanical discharge somewhere, if it inadvertantly set off the ordnance lines leading to the motor igniter, would not actually get to the igniter. They are simple mechanical blocks that prevent the signal from getting through unless they are properly activated.
The Minuteman S&A’s worked well enough. So, when Thiokol was developing the solid rocket boosters for the Shuttle, they used the Minuteman S&As. And since once something is designed and fielded at NASA it almost never changes, the 1963-vintage S&As stayed with the RSRMs throughout the lifespan of the Shuttle. Last I knew, they were also in use on the five-segment boosters to be used on the “next generation” Space Launch System.” So *if* the SLS gets built (doubtful) and flies for decades (doubtful), the relatively ancient Minuteman S&As will probably fly with them throughout the SLS’s lifespan. If SLS flies in 2020 and lasts 20 years, the Minuteman S&A will have an 80 year operational life. Of course, by the time the SLS is retired, the Minuteman ICBM itself might still be in service.