Rocket motor company ATK has made the final required burn test to qualify a new nozzle for the GEM-60 solid rocket motor, which powers the United Launch Alliance (ULA) Delta IV Medium+ configuration.
The 6 September test, the second of two, tested nozzle performance in cold weather, requiring the nozzle to be cooled to -1.1 degrees Celsius (30F).
"Periodically we have changes in materials that happen, either a supplier elects to use a different material or stops building the component," says Hal Murdock, ATK programme manager. "In this particular case we had a company that supplied the nozzle as a supply item to us, and that was Hitco. And they are no longer making the nozzle. So we did some internal trades and looked at manufacturing [the nozzles] ourselves, and it turns out that's the way to do it."
ATK will produce two versions of the nozzles at its Nozzle Center of Excellence in Promontory, Utah, one fixed and one gimbaled. The gimbaled version was last tested in June.
"Part of it is certifying that yes, ATK can make the nozzle using existing procedures and so forth.the other is the materials are using a new source of material." Rayon, a heat-resistant material, is now sourced from Enka, as opposed to former supplier Narc.
©ULA: Two GEM-60s assist a launch
"We may have got away without a static test moving the manufacturing, but with a new material in there you have to static test it," says Murdock.
The GEM-60 solid rockets are used to augment the Delta IV's liquid-fueled Rocketdyne RS-68 core engine, giving the launch vehicle an initial boost and detaching once the solid rocket fuel is spent. The Delta IV Medium+ requires either two or four GEM-60s, depending on the required lift performance.