Spacelab was a reusable laboratory that could be carried in the Space Shuttle's cargo bay, providing lab space for astronauts and experiments.1 Because Spacelab was a European project, it used a French-built minicomputer, the Mitra 125 MS,2 rather than the Shuttle's main computers, IBM-built AP-101 systems. For storage, the Spacelab computer contained 128 kilobytes of RAM. Rather than silicon memory, the computer used magnetic core memory, with each bit stored in a tiny ferrite ring. In this article, I take a close look at this computer's core memory system. The core stack from the Spacelab computer. I removed the top...