After more than four decades in space and having traveled a combined 44 billion kilometers, it’s no secret that the Voyager spacecraft are closing in on the end of their extended interstellar mission. Battered and worn, the twin spacecraft are speeding along through the void, far outside the Sun’s influence now, their radioactive fuel decaying, their signals becoming ever fainter as the time needed to cross the chasm of space gets longer by the day.

But still, they soldier on, humanity’s furthest-flung outposts and testaments to the power of good engineering. And no small measure of good luck, too, given the number of nearly mission-ending events which have accumulated in almost half a century of travel. The number of “glitches” and “anomalies” suffered by both Voyagers seems to be on the uptick, too, contributing to the sense that someday, soon perhaps, we’ll hear no more from them.

That day has thankfully not come yet, in no small part due to the computers that the Voyager spacecraft were, in a way, designed around. Voyager was to be a mission unlike any ever undertaken, a Grand Tour of the outer planets that offered a once-in-a-lifetime chance to push science far out into the solar system. Getting the computers right was absolutely essential to delivering on that promise, a task made all the more challenging by the conditions under which they’d be required to operate, the complexity of the spacecraft they’d be running, and the torrent of data streaming through them. Forty-six years later, it’s safe to say that the designers nailed it, and it’s worth taking a look at how they pulled it off.

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