While the Orion capsule of the Artemis mission is about to skim the Moon with computers 20,000 times faster than those of the Apollo era, humanity tends to glorify the race for computing power. However, the most dizzying space feat in our history does not rely on the latest generation of microprocessors. Far, very far beyond the boundaries of our solar system, two spacecraft launched in 1977 continue to transmit invaluable data. Voyager 1 and 2, which carry the oldest still active American government computers, prove every day that engineering from half a century ago is capable of defying eternity.
A Brain from the era of cassette tapes
To grasp the technological miracle represented by the Voyager probes, one must go back to the context of their birth. When launched in 1977, the first Star Wars movie had just arrived in theaters, and personal computers were in their early stages with the Apple II. It was with this outdated technology that Voyager 1 became, in 2012, the first object made by human hands to enter interstellar space, joined by its twin six years later.
Situated over 24 billion kilometers from their home planet, these scouts navigate thanks to an outdated computer architecture that would make any modern engineer smile. Each probe is equipped with six rudimentary computers (divided into three redundant systems), custom-designed by General Electric.
Their total computing power? Barely 68 kilobytes. This memory capacity is lower than what is required to store the smallest photograph on a current mobile phone. For comparison, a mid-range modern smartphone possesses about 125,000 times more RAM than the systems of these two probes combined. And to top it off, the scientific data recording still takes place on an ancient 8-track digital magnetic tape.
A truly antique technology: the 8-track digital recorder currently aboard the Voyager probes.
The inexorable nuclear countdown
While the computers miraculously survived cosmic radiation and absolute cold for nearly five decades, the probes face another relentless enemy: energy hunger. At such a distance from the Sun, light is only a bright star among others, rendering solar panels completely useless.
The survival of Voyager relies on radioisotope thermoelectric generators (RTGs). These nuclear mini-reactors convert the heat emitted by the natural decay of plutonium-238 into electricity. Brilliantly designed without any moving parts to avoid mechanical wear, these generators, however, have an inherent limitation in nuclear physics: over the decades, the radioactive material decays and the electrical power decreases inexorably.
To delay the fatal inevitability, NASA is now forced to act like a surgeon operating billions of kilometers away. To save the last available watts, engineers must make the difficult decision to amputate the probes of their senses. They proceed with the gradual shutting down of the heating systems and certain scientific sensors, such as the famous plasma study instrument on Voyager 2, which was recently switched off.
Space debris carrying an eternal message
Despite these drastic rationing measures, the probes’ agony is mathematically programmed. By the early 2030s, the generators will no longer provide enough energy to power the communication systems. The ancient computers from 1977 will permanently shut down, and NASA will lose contact with its two explorers forever.
They will then embark on a silent drift, becoming mere metallic debris sailing in the Milky Way. But that would be forgetting their ultimate mission. Attached to the side of each probe is the Golden Record, a copper disc coated with gold. These artifacts contain images of our world, greetings spoken in 55 human languages, and a selection of musical works. Dead and mute, the Voyager probes will continue their journey for billions of years, carrying this precious message into the depths of the universe, in the faint hope that some distant intelligence will one day come across our memories.
