ATK and United Launch Alliance (ULA) test fired a Graphite Epoxy Motor (GEM-60) solid rocket motor that is used on ULA’s Delta IV family of launch vehicles. The ground test was conducted to verify the GEM-60’s cold temperature performance.
“This test further qualifies ATK’s in-house capabilities in manufacturing commercial nozzles as flight ready,” said Scott Lehr, vice president and general manager, ATK Aerospace Group, Defense and Commercial Division. “Utilizing ATK nozzles not only provides better value to our customer, it also helps further secure employment of our skilled workforce.”
Each GEM-60 is 60-inches in diameter and 53-feet long. The booster was chilled to a core temperature of 30°F to see how it would perform under challenging test conditions. By all accounts the GEM-60 used in today’s test performed as advertised producing some 270,000 pounds of thrust. The test lasted for approximately 90 seconds and was the second in a series to prove out the GEM-60’s fixed and vectorable (capable of being moved to guide the Delta IV launch vehicle in different trajectories).
“We did a test like today’s back in June for a similar reasons, we had a supplier that used to provide the nozzles. They are no longer producing that and ATK is producing the nozzle,” said ATK’s Director of Strategy and Business Development for the company’s Defense and Commercial Division. “Because of the reliability requirements on this solid rocket motor, so we need to validate processes revolving around the new materials used and that we were constructing the nozzles as opposed to an outside firm that we static test to ensure that remain within all of the safety and reliability margins that are built into this rocket.”
ATK used ENKA Rayon in the manufacture of this nozzle. Previous nozzles used NARC Rayon. The names refer to the name of the rayon manufacturers.
“The nozzle had to withstand pressure, temperature, etc for longer than it would during a nominal test day launch,” Murdock said. “The test today enveloped all of the possible test day conditions that United Launch Alliance might launch under. Initial indications are everything was right down the line, right where we expected them to be.”
Now, ATK will inspect the nozzle to see if any defects or issues occurred during today’s firing.
“One of the things that we have to do now is to look at the nozzle, cut the nozzle up – make sure that all of the ablative material, the phenolic material that absorbs all of that heat and mass flow had the required margins remaining after the test is done, so, that analysis has yet to be done but initial indications from all the data that was gathered indicate a good test.”
GEM-60s are strap-on boosters that were developed for ULA by ATK back in 2000 to increase the ability to deliver payloads to orbit for the Delta IV Medium+ rocket. The first Delta IV to fly with two of these boosters was launched in November 2002, and the first four-motor configuration flew in 2009.
“The payloads that the Delta IV family of launch vehicles deliver to orbit are critical to the national security of our country. While the public is more familiar with the NASA side of launch, these missions are just as important. The Gem-60 helps to launch reconnaissance satellites, comman-and-control satellites and GPS satellites as well. These are critical to the communications and other tactical data-link infrastructure of our military. It’s crucial that ULA can continue to depend on the reliability of these boosters – and we’re striving to see that this takes place.”
Video courtesy of ATK