1. Iterate.

I asked Dodd point blank: Is Voyager special, or just first? Could any NASA probe have crossed the heliopause into interstellar space, simply by aiming it in the right direction and waiting long enough? In short, no. "The Voyager project learned a lot from the Pioneer missions who went ahead of voyager to study Jupiter," Dodd says. "They found this very strong radiation environment at Jupiter that adversely affected the probe's electronics. Because of that, NASA added more shielding and redesigned some of the Voyager probes' components so that they could survive Jupiter's radiation."

2. Simplify.

Obviously, NASA is not in the business of sending superfluous equipment into space. Every craft is designed to execute its primary mission as efficiently as possible. Still, Dodd acknowledges, In some important ways the older spacecraft are simpler." For one, Voyager 1's onboard computer has just 68 kilobytes of memory: 1/240,000th of the computing power in your smartphone, according to Dodd. That didn't seem so piddly back in 1976, when Voyager launched, but 36 years later, "there's a simplicity to it that lets you not get into trouble, especially when it comes to commanding and operating," she says. "You could make an analogy to a car. Nowadays the engines are all computerized and more likely to break down than an old car that you could just pop the hood and understand every piece of. That's important, since of course we can't take Voyager to the shop when something goes wrong."

3. Back up.

Redundancy and automation are a given in spacecraft design, especially when creating objects to explore environments that are literally alien. "Voyager was the first spacecraft to use onboard fault protection," says Dodd. "Without a command from the ground, it could sense the state that it was in, and turn something off if there was a problem. We are so far away: The roundtrip light time [for exchanging electronic signals] is over 34 hours, so you can't do anything in real time." Voyager also has a "backup mission" installed, which ensures that the craft will continue to execute and transmit science measurements if it doesn't receive command signals from Earth. "Voyager was one of the first probes to have this," Dodd says. "They're much more sophisticated now, but it was a big deal in the 1970s."