DIY Podcast: Solar Arrays Audio Clips Transcript
 
International Space Station Expedition 12 Commander Bill McArthur discusses how electricity generated by solar arrays is used on the station. The following text is the transcript of McArthur's audio clips.

Bill McArthur: 1-a. Hi. Welcome on board the International Space Station. I'm Bill McArthur, commander of Expedition 12. I'd like to talk to you today about something that we think is pretty important.

2-a. As y'all are aware, there are certain things on Earth that are essential for life. I mean we all know that we have to have air to breathe, food to eat, water, fluids to drink. Well, in space there's something else that's also essential to life, and that's electricity.

3-a. So, where do we get electricity from? Of course we don't have a power company that runs lines to our house and that we can get electricity from as you do on the ground. The primary source on the International Space Station is something we call solar arrays. There are many terms that we'll use -- photovoltaic arrays, solar panels. We even sometimes call them solar wings.

4-a. On the U.S. segment, each solar array wing consists of two solar blankets or solar panels. Each panel consists of 16,400 little photovoltaic modules, little photovoltaic receptors. The sunlight -- when it shines on these photovoltaic modules, these photovoltaic arrays -- produces electricity. And then we use that electricity throughout the space station.

5-a. Why would we command the solar arrays? Well, we've all been out in the sun and know that if you turn and close your eyes and turn your face up to the sun, how warm it feels. But if it's a little too hot, you turn away and get a little shading on your face, and it's cooler. Well, in order to generate as much electricity as possible, we always need to point our solar arrays so that the sun can shine directly on them. And so that's what we use the computer for -- to command the solar arrays.

6-a. All that information is to tell us that the solar arrays are -- how much electricity they're generating, where the electricity is going and how the solar arrays are tracking the sun.

7-a. I mentioned just as food, air and water are essential to life on Earth, electricity is also essential to life on board the space station because we use the electricity that's generated on board the space station to manage our food, air and water.

8-a. We use electricity to circulate the oxygen -- the air -- throughout the space station. Unlike on Earth where you can just go outside and there's plenty of fresh air, we have only the air that we have brought and we maintain inside the space station. And there are no natural winds to circulate the air, so we have to use fans to move the air around. We have special filters to clean the air so it stays nice and fresh.

9-a. We also have to condition the air. Since we can't go outside and since we can't open any windows, any humidity in the air would just begin to accumulate. So we have to have air conditioners to make sure there's not too much humidity in the air.

10-a. And of course we like electricity to warm our food up so that it just tastes a little better.

11-a. We use electricity to purify the water. I mentioned that we take humidity -- we take moisture -- out of the air. Well, we collect that. We make sure we purify it. And then we break that water down into oxygen and hydrogen, and that's where some of the oxygen comes from that we use when we breathe.

12-a. In addition to the life support systems, of course you know that the purpose of the space station is to conduct scientific research on orbit. So, of course, we need electricity for our experiment.

13-a. We have a couple of racks, which are designed to study the human lung function. We have what's called a refrigerated centrifuge, and again, it's designed to help us conduct experiments on orbit. All of this equipment requires electricity.

14-a. Just like in your house, we have outlets along the wall where we can plug equipment in. We don't use exactly the same types of plugs that you would in your house. Ours are very, very secure. We don't want things to become unplugged by accident. And so we have to screw the connectors in.

15-a. We utilize all our electrical outlets all the time. And so it's very rare that we can actually turn the outlet off itself. So our extension cord has its own switches, and we can use those to turn equipment on and off.

16-a. Now you know. We really think electricity is a big deal. It's a little bit different here than it is on Earth. We use direct current instead of alternating current. We use 120 volts in the U.S. segment, 28 volts in the Russian segment.

17-a. You know where we get our electricity -- from the sun. We go around the Earth once every 90 minutes. Well, 45 minutes is in darkness. So what do we do when we're in darkness? Well, we use batteries. The electricity charges batteries. And when we're in darkness, we use the batteries to provide all the electrical power we need. The batteries on the U.S. segment are located outside where the solar arrays are. However, in the Russian segment we have 14 of these batteries mounted internally. They weigh about 200 pounds apiece. How would you like to see that in your car?

18-a. Just to sum it up, for us, electricity is life on board the space station. Without our solar panels, we wouldn't be able to fly. And, by golly, we sure have a good time up here. And so we're very grateful for the wonderful work that our solar panels do for us.

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