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If you want to get into outer space, you need an energy source that packs a whopper of a punch, like combustible fuels. But if you want to stay operational in space, you need to harness power from another source, like the Sun itself.

In the 1970s, researchers anticipated that to collect that solar power, future missions would need solar panels larger than the vehicles meant to take them to space. So one space shuttle mission was tasked with testing a new kind of panel: One that could fold up. While the concept of converting solar radiation into electricity has been around since the 1800s, the first solar cells efficient enough to actually run everyday pieces of equipment weren’t developed until the mid-1950s.

And that just so happened to be just before humans started launching satellites into space. The first spacecraft to feature solar cells was Vanguard I, which the US launched in March of 1958, and for context, that’s months before NASA even formally began operations. It was only the second satellite the US had successfully launched into space.

Solar cell technology was still young, so the satellite only had six cells, which were used to run one of two radio transmitters. The other transmitter was powered by a traditional battery and died a few months into the mission. But the one running on solar power kept working into 1964, which was a pretty clear demonstration of how crucial solar power was going to be to long-term space missions.

Over the decades, NASA needed bigger and better solar panel technology to power more sophisticated and energy-consuming missions. In the 1970s, engineers designed a prototype solar array “wing” made of 84 panels connected using mechanical hinges. Not only was it about one eighth of the weight of previous panels, it could also retract like an accordion.

This feature made it easier for astronauts to repair or replace individual panel segments. They could also expose only as much of the panels to the harsh environment of space as they needed. That meant the panels could go longer between repairs.

And the less often you have to put on a spacesuit and go out into the near-vacuum of space, the better. In 1977, NASA’s Office of Aeronautics and Space Technology, or OAST, decided to test a full-scale version of this new solar array by sending it to space with a vehicle that was still a few years away from launch: the Space Shuttle. Specifically, it would be the job of the.

Space Shuttle Discovery on its maiden voyage. The mission launched on August 30, 1984, carrying the prototype wing and some other experiments all packaged into a payload called OAST-1. And while the wing was full scale, it wasn’t a full prototype, only two of the panels had active solar cells on them.

On the third day of the mission, astronaut Dr. Judith Resnik began unfurling the wing. First, it was extended to just 70 percent of its total length.

On the next day, she extended it the rest of the way. Then Discovery jiggled around a bit using its thrusters to test that the wing was secure and could handle any unexpected wobbles on future missions. After unfurling, it became a wing stretching over 31 meters long, making it the largest structure deployed from any crewed space vehicle at the time.

In comparison, the cargo bay of the shuttle was 18.3 meters long. Overall, the experiment was enough of a success that it paved the way for similarly sized, retractable solar panels to be used on future missions. For example, the panels on the International Space Station are functionally similar, although instead of wings they’re generally referred to as blankets.

They’re also a lot wider, 11.9 meters instead of 4. But they were still able to fold up inside the space shuttles, which delivered most of the ISS’s panels. In total, the ISS has over 262,000 solar cells spread across four sets of panels, which cover an area of about 2,500 square meters.

When they’re in direct sunlight, these cells convert enough energy to power more than 40 homes. Now, that’s more than the astronauts need at any given moment, so some energy gets stored for the times when the Earth is blocking the Sun. But the cells are nearing the end of their lifespan, so this year NASA plans to start using SpaceX’s Dragon capsules to send up some additional, smaller arrays based on even newer, lighter, and more flexible technology.

Only instead of folding, they’ll be rolling. The Roll-Out Solar Array, or ROSA, features a central wing supported on either side by stiff tube-like arms. When the arms are rolled up, they store the energy needed to unfurl the whole array.

In other words, there’s no motor required! ROSA was tested on the ISS back in 2017. And while the array successfully deployed, and passed all the tests it needed to, it didn’t want to roll back up.

So the astronauts had to jettison it, which is why these new technologies get tested before we implement them. But once up and running, this set of upgraded panels will increase the daytime power available on the ISS from 160 kilowatts to 215. And the technology opens up opportunities for collecting sunlight back on the ground, too.

Because finding effective, renewable sources of power is growing increasingly important here on Earth. If you’d like to bring some sunshine to your wardrobe, check out this month’s Pin of the Month, inspired by the solar powered Discovery shuttle! All August, we’ll be taking preorders, so check out the link in the description before the end of August to place your preorder.

And keep an eye out for the next pin in September! Thanks! [♪ OUTRO].