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Using Gold Wire to Thread 1600 Needles ...Twice

by Russell Hall, SSEC Publications
Building space flight hardware sounds pretty glamorous to a lot of us: working with state-of-the-art equipment to create instruments that will fly in outer space, enhancing humankind's understanding of the universe. But when you get down to the nitty gritty reality, it can be far less glamorous.

Space Flight HardwareAsk Tony Wendricks about spending an evening in a Chicago motel room spreading wires so they could be properly plated. Ask Dave Jones about threading those same wires, 1600 of them, one by one through a tiny grid

Tony and Dave are down in the trenches of an engineering project that will fly on a satellite gathering information about X rays from outer space. They're building a high-tech refrigerator of sorts to keep detectors working at peak efficiency.

Don't Say Impossible

The project has been daunting from the start. When the group, which also includes Mike Dean and Mark Mulligan, first met with the Principal Investigator, Dan McCammon of the Physics Department, Tony says his first thoughts were "can we even do this?" The refrigerator uses a magnetic field and salt crystals to supercool gold wires. 1600 gold wires had to be strung, without touching, in a container the size of a soda can. "In the spirit of this place [SSEC]," Tony continues, "I wasn't going to say it was impossible."

The ADR under construction.
The magnetic salt-crystal cooling element (ADR) under construction. The 1600 gold wires are exposed while they are strung and connected to the four copper rods that will cool one of the Astro-E satellite’s X-ray detectors.

The task for SSEC's Space Flight Hardware group was to build an Adiabatic Demagnetization Refrigerator (ADR). This small unit will fly on the Astro-E satellite, a joint Japanese-NASA X-ray astronomy project. The ADR will be used to cool one of the satellite's X-ray detectors down to almost absolute zero. By keeping the temperature low, the heat generated by a single X-ray photon can be detected and measured. Gathering information about X rays will tell us more about things like black holes, white dwarves, supernovae, and a myriad of other far-flung phenomena.

After much trial and error, the team finally hit on a way to string the wires using a perforated disk, which looks more than anything else like a piece cut from a colander with very small holes. The other major component of the project was developing the method to be used for growing the salt crystals. The salt solution includes sulfuric acid and is highly corrosive, forcing the use of some rather expensive materials for the rest of the ADR's components. Only gold, along with stainless steel, isn't eaten by the caustic soup used to grow the crystals.

[Part II, A Plate of Overcooked Pasta]
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