Keeping Cool in Space

When Pink Floyd sang about meeting you “On the Dark Side of the Moon,” do you think they considered the temperature???

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Because there is no atmosphere to retain heat when it’s dark or blocks the sunlight, space exhibits extreme temperature variations —?which was a major consideration when designing the International Space Station (ISS) Thermal Control Systems. The temperature outside can range from?-250° F on the shady side to + 250° F on the sunny side.?However, because objects in orbit spend more time in partial sunlight than in complete opposition to the sun, the temperature outside the ISS averages around 50° F.??

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Inside the ISS’ habitation modules, the temperature stays at a comfortable 72° F thanks to the station’s two thermal control units. These units also create the correct environment to cool the electrical components, thermal batteries, and experimental components.??

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Needless to say, the approximately 1,500 Class A welds on the cooling systems are critical. The ISS orbits at an altitude of 250 miles and at a speed of 17,500 MPH, so it isn’t exactly on the service route of a? Navy Veteran, Hull Maintenance Technician. Paraphrasing the famous Apollo 13 mission quote, Ernest Levert Sr. says, “Weld Failure is not an Option.”??

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Levert worked at Lockheed Martin Missiles and Fire Control, Dallas, TX for 37 years, including roles as the corporate welding engineering and materials joining subject matter expert supporting the International Space Station Thermal Control Units Program, as well as other components. He will share details on the welding program in his keynote presentation, titled “Keeping Cool in Space,” at the AWS Welding Summit 2024 at The Woodlands Resort, Texas (just north of Houston), held August 7 – 9.?

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“When we manufacture parts here on earth, they have to work up in space. You have to take your time and do it right,” says Levert. To make it even more challenging, much of the GTA welding required was on small diameter, thin wall tubing (e.g., 0.125 – 1.0” diameter, 0.028” wall thickness) made from materials such as INCONEL? ALLOY 718 and 625. These nickel-chromium alloys are notoriously difficult to weld because the heat from the welding arc tends to stay localized.?

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“Every weld is inspected five times to be sure we did it right, including visual inspection by CWI, X-ray, proof pressure, helium detection, dye penetrant inspection and using a borescope to inspect the ID,” says Levert. “In fact, the manual welders had to pass a weld test every single day before they could work these quarter-million-dollar components.”??

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For more on upcoming AWS events and conferences, visit American Welding Society Community and Events (aws.org)