The book Eccentric Orbits makes the point that the Iridium satellite constellation relies heavily on the basic technologies which were devloped, in some fledgli

The book Eccentric Orbits makes the point that the Iridium satellite constellation relies heavily on the basic technologies which were devloped, in some fledgling form, for SDI. Specifically, communications satellites before that were as dumb as possible, the 'bent pipe' model -- whatever goes up on one frequency, comes down on another. The satellite neither knew nor cared about the payload. The majority of electronics were actually analog. But with SDI, satellites had to communicate with each other. They had significant processing on-board. They made their own in-space mesh network, though that term wouldn't be used until later. They had to cope with possible loss of a satellite and keep the data flowing between the others. That's exactly the fundamental concept behind Iridium and several more constellations since, Starlink perhaps most familiar to the most HN readers. Motorola did a lot of the dev work for SDI, and after the project was scrapped, Motorola went on to build Iridium. Brooks argues in the book that the fundamental R&D for Iridium wouldn't have been practical without the groundwork laid, and paid for, by SDI.