WASHINGTON — As the deadline nears for an Air Force competition to fund development of new launch vehicles, Orbital ATK announced Nov. 7 what it called an “important milestone” for its proposed launcher.

In a statement, the company said it successfully tested a new composite case for the solid rocket motors that it plans to use in its proposed Next Generation Launch (NGL) rocket, stressing the case to 110 percent of loads and pressures it would experience in flight.

NGL will use solid motors similar in design to those used on the shuttle and Space Launch System, but with the improved composite case like the one tested as well as a different propellant formulation. The rocket’s first stage will use either a two- or four-segment motor, depending on performance requirements, while the second stage will use a single-segment motor. An upper stage will be powered by an engine using liquid hydrogen and oxygen propellants. The NGL would also be able to use strap-on boosters.

The company has identified NGL as one of its major projects, and as of earlier this year said it had spent $200 million on the effort using a combination of Air Force and company funds. NGL is expected to remain a priority even after Northrop Grumman’s acquisition of Orbital ATK closes in the coming months.

“NGL is one of Orbital ATK’s top growth initiatives,” said Scott Lehr, president of Orbital ATK’s Flight Systems Group, in a statement about the test. “This milestone clearly shows the progress being made by the hundreds of engineers and technicians in Utah and Arizona who are developing the NGL system.”

The company will seek additional funding for the program through the Air Force’s Launch Services Agreement competition, which plans to make up to three awards next year to support development of new launch vehicles in the Evolved Expendable Launch Vehicle class to ultimately replace the Atlas 5 and Delta 4. The Air Force issued a request for proposals for the program Oct. 5, with proposals due Nov. 20.

Both SpaceX and United Launch Alliance are expected to also submit proposals for the competition, but Orbital ATK is confident it will receive an award that will allow it to continue development of the NGL through test flights of the vehicle. In the statement, the company said if expected to receive a Launch Services Agreement award in mid-2018.

“I think we’re pretty confident we’re going to make the LSA downselect,” Mike Laidley, vice president of the NGL program at Orbital ATK, said in an April interview. “We have a high degree of confidence that we provide value to the Air Force.”