Lab-built components bound for outerspace
Chances are pretty good that Jerry Hand and Jim Safly will never travel to outer space. Fishing trips to Canada or winter excursions to Florida are more likely destinations for the two Ames Laboratory machinists who grew up as neighbors on nearby farms.
Yet the two are involved in a project that could eventually see some of their handiwork make the trip into space aboard the Shuttle, the International Space Station, or future space flights to Mars. Hand and Safly have been busy the last month fabricating components for equipment designed to test and monitor the quality of spacecraft drinking water.
The problem NASA faces in extended space flights is being able to carry sufficient amounts of water to support space crews. As a result, every drop of water is precious and most, if not all of it, needs to be recycled, through filtering and treatment with iodine and silver, into potable water.
Because of its expertise in electrochemical sensing and microelectronics, Iowa State University's Microanalytical Instrumentation Center received a three-year NASA grant to help solve the problem. Marc Porter, MIC director and ISU chemistry professor, and his research team came up with a method for testing samples using a small, portable chromatograph.
But what works here on Earth won't necessarily "fly" in the zero-gravity environment of space. The team needed a way to ensure the water test samples are contained and that the chromatograph be held firmly in place. With help from CIRAS engineer John Roberts, designs for a two-piece plastic coupling and a mounting bracket were developed. That's where Hand and Safly enter the picture. Hand went to work on the coupling, while Safly started on the bracket.
Starting with a solid blank of Delrin, a tough, high-density plastic, Hand had to mill the intricate shape of the coupling, including grooved seats for rubber O-rings only a few thousandths of an inch in size. Unable to make such precise cuts with conventional milling tools, he turned to a relatively new piece of equipment in the Metals Development Machine Shop, the Robofil 290 Wire Electrical Discharge Machine - EDM for short (see the related story directional).
"I had to make a separate cutting tool for each of the profiles," Hand says, showing how the cutting edge of the tool perfectly matched the lathe-turned profile of the coupling. "The EDM gives us capabilities we've never had."
Outfitted with the rubber seals and a thin membrane, the coupler fits into a port in the chromatograph. The water sample, collected in a syringe, is injected into the system, and a reading is taken to determine the amount of iodine present. After the initial coupling design proved to be too difficult to separate, Hand modified the pieces to come apart with a squeeze and a slight twist.
Meanwhile, in the Sheet Metal Fabrication Shop, Safly started turning a flat piece of 16-gauge stainless steel into the U-shaped mounting bracket for the chromatograph. Once it was cut out, the bracket required precision drilling for the mounting screws. Then Safly had to carefully bend the metal to its final form using the shop's large sheet metal brakes.
"Normally, we don't receive plans with this amount of detail," Safly said of the computer-generated drawings spread out on his workbench. "And most of the time we don't get to see how the pieces we fabricate actually work. We simply move on to the next project."
The components got a preliminary test this month when Porter and visiting scientist Matteo Arena traveled to Houston and made test flights on NASA's KC-135 turbo jet. Nicknamed the "vomit comet," the plane makes a series of parabolic climbs and dives, providing a brief zero-gravity environment during the steep dive.
"It was an intense sensation for us, but the experiment went very well," Arena said, adding that the components made by Hand and Safly worked perfectly.
Not bad for a couple of local farm boys.