Here on Earth, solar power is one of the ultimate sources of off-grid electricity. Unless you’re in the far north and don’t get sunlight half the year or you’re somewhere that’s frequently cloudy, it’s a very dependable source of electricity that can be used to charge batteries and power everything from a phone, to a small refrigerator ice chest, to a whole house or EV. So, it’s a great alternative.
In space, you have less of a choice. Even as close to earth as the International Space Station or China’s Tiangong Space Station, you can’t exactly drive to town to get more fuel for your trusty Honda generator. Not only are you always at least 250 miles from the nearest town, but getting things into earth orbit takes a lot of energy. Even if your old lawnmower-engined generator could work in space (it can’t run without oxygen), bringing fuel for the thing would be prohibitively expensive.
So, solar or forms of nuclear energy are about your only choice. When it comes to nuclear power, the only choice for small probes is a Radioisotope Thermoelectric Generator (or RTG). These aren’t a typical nuclear reactor, but do use heat shed by radioactive materials to make a few hundred watts of electricity and run spacecraft sensors and radios.
These days, RTGs are mostly used for space missions that will venture out too far from the sun for solar panels to be useful. They’re dangerous to humans, so a launch mishap or failed slingshot around Earth would be more dangerous. They’re costly. Perhaps most importantly, there just isn’t that much of the fuel left in the United States or Russia to make many more of them, so we avoid using them when we can do something else.
NASA’s Lucy spacecraft is pretty much an ideal fit for using solar panels instead of an RTG. It’s going to spend the next few years working up energy making loops around Earth, and then fly off toward the orbit of Jupiter where gravity has collected up a bunch of very ancient asteroids both in front of and behind Jupiter in its orbit (the L4 and L5 Lagrange points). Along its route, it will get images of several asteroids, including one pair of them that might have originally come from the outer solar system.
To get sufficient power to run the science instruments, cameras, and radios, Lucy’s solar panels have to be bigger than they need to be near Earth. The further you go from the sun, the less power you get, and they’re going out a ways. The problem is that big panels like that won’t fit inside the rockets they use to put these probes in space. So they made Lucy’s solar panels in such a way as to fold up for launch and then fold out once it’s in space and ready to start collecting power.
Sadly, one of the solar panels didn’t deploy all of the way. It did fold out enough to give enough power for the mission, but it didn’t get out as far it needs to go to lock into place. So, when they hit the main rocket and send it off deeper into space, it could end up folding back up and not giving enough power or getting broken, which would obviously ruin the mission. They think a rope-like “lanyard” has hit a snag, and that if they turn both the primary and backup motors on at the same time, they’ll tug the lanyard enough to pull it out of its snag and lock the solar panel into place, fully folded out and safe for nailing that rocket.
All of this is going to start happening on May 9th, with the first step being a lighter tug to pull the lanyard taut and make sure the problem is what they think it is. Then, if it checks out, they’ll give it the harder tug it needs to latch up and be ready to go.
Anyone who has had trouble with solar panels can probably appreciate how much easier it is just to climb on the roof and fix them, or otherwise walk over and solve the problem. Being on Earth has its advantages!
Featured image by NASA.
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