September 15, 2006
Making Space Cool
Back in 1996, I got a call from an editor at Scholastic who liked my proposal for a book about the space station. She explained that before she could offer me a contract, I needed to send her a sample chapter that she could use to persuade the marketing department that this book would sell. I wondered what topic to choose that would grab their attention and seal the deal for what would be my first book contract.
Coincidentally, I had planned to attend an NSS regional conference in Dallas that same week. Should I cancel so I’d have more time to write, or should I go and hope that I’d learn something useful for the book? I decided to go. I was not sorry! Astronaut Don Thomas’s enthusiastic description of his recent shuttle launch was perfect for a chapter on getting to the space station. But I really wanted to show this editor that the space station itself is a cool topic.
The next speaker was an engineer from Vought Systems (later Loral Vought) who described the space station radiators that his company was building. Even better, he offered to take us on a tour of the factory! You may be thinking that such a tour would only appeal to diehard space enthusiasts, and you may be right. But what I learned on that tour was so captivating that I decided to risk my future career as a children’s author by focusing my sample chapter on the space station radiator panels—the very ones that were deployed on the space station this week.
You probably are aware that space is an extreme place in terms of hot and cold. Temperatures vary about 500 degrees from sunlight to shadow. Cold is an issue for equipment outside, yet inside, getting rid of the heat is the bigger challenge. People and equipment produce lots of heat, and there is no option to open the windows.
Hot air on Earth rises because it is less dense than cold air. In freefall, they both weigh the same: nothing! So hot air stays near its source in an invisible cloud around each hot thing or person. Cabin fans move and mix the air, but do not get rid of the heat. To do that, the fans push the hot air into a cold bath called a heat exchanger.
The air/water heat exchanger on the station is shaped like a sandwich with more than 30 layers of air and water separated by metal sheets. Hot air from the cabin warms the metal that in turn warms the cool water on the other side. The cooled air exits the heat exchanger and the warmed water flows away in pipes.
The water pipes also pick up heat from cold plates that are flattened-out sections of pipe on which equipment sits. The warmed water cannot be taken “outside” to be cooled because water expands when it freezes, and burst pipes are not a good thing. So the water is cooled by giving its heat to ammonia in another heat exchanger. (The space shuttle uses Freon instead of ammonia.) Ammonia can get much colder than water before it freezes, and it doesn’t expand when it does. (Cabin heat is not directly transferred to ammonia because escaping ammonia would poison the crew. It is safer to use water as a “middleman.”)
The ammonia flows out of the module to the radiators and through hundreds of little pipes. Each one of those pipes was painstakingly hand-welded by someone at the Vought factory in Dallas. I got to see the actual panels in their pristine white condition, protected behind drapes of plastic sheeting. (Radiators on the shuttle are mirrored, but this surface does not hold up well in the space environment, so the station radiators are painted white.) I knew that someday, those “cool” pieces of hardware would be mounted perpendicular to the solar wings on the space station that I hoped to write a book about.
I have always known that space is cool. And thanks to the Dallas chapter of NSS and the workers at Vought, I learned how it stays cool, and was able to share that information with that editor at Scholastic. She said she had no idea that a subject as dull-sounding as “the thermal protection system” could be so engaging! I got my contract (for Space Station Science, now in its second edition with Windward).
Members of NSS often question if the time they spend attending and organizing conferences and tours and meetings actually makes a difference. As my experience shows, it does, and not necessarily in ways you might expect!
So I hope you will join me next May for the International Space Development Conference in Dallas (see “2007 Conference Information” link on the Home page). The conference co-chair is Carol Johnson who used to work at Loral Vought and arranged that “cool” tour. She is sure to recruit some out-of-this-world speakers and set up tours that will impress even the most skeptical editors.
Space is cool, and thanks to the addition of the new radiator by the STS-115 crew this week, getting even cooler.
Posted by m_dyson at September 15, 2006 02:33 PM