WASHINGTON — Aerojet Rocketdyne’s losses widened during the third quarter of 2015 compared with the same period last year due in part to its $50 million settlement with Orbital ATK stemming from last October’s failure of the latter’s Antares rocket.

In an Oct. 13 press release, Sacramento, California-based Aerojet Rocketdyne also said it has spent $24 million so far this fiscal year working on its AR1 engine, which the company has proposed as a replacement for the RD-180, the main engine on United Launch Alliance’s government workhorse Atlas 5 rocket. Congress has mandated that the Pentagon stop using Russian-made engines to launch its satellites, but ULA has made Blue Origin’s BE-4 the leading replacement candidate.

During the three-month period ending Aug. 31, Aerojet Rocketdyne reported a net loss of $38.1 million on $440.5 million in net sales. The company lost $10 million during the 2014 third quarter, owing largely to a $17.5 million loss related to its contract to supply Orbital ATK with AJ-26 engines, one of which failed on a test stand earlier that year.

The AJ-26, the main engine on Antares, has been blamed in the Oct. 28, 2014, failure of that vehicle, which destroyed a load of cargo bound for the International Space Station. Aerojet in September announced it has settled with Orbital ATK over the engine’s role in the failure, which ultimately led to Orbital ATK selecting a different Russian-made engine for Antares.

Aerojet Rocketdyne also cited a $29.5 million environmental remediation expense as a contributor its losing quarter.

Solid rocket motors, primarily for U.S. missile defense programs, continue to be Aerojet Rocketdyne’s largest source of revenue. The company booked $61.2 million and $55.6 million on the Theater High Altitude Area Defense and Standard Missile programs, respectively, during the quarter, with both figures representing substantial increases over the same period last year.

The company also reported $50.2 million in net sales from the RS-25 engine being developed for NASA’s Space Launch System heavy-lift rocket program, a 70 percent increase over the 2014 third quarter. Net sales on NASA’s Orion capsule were $20.1 million, up by more than 30 percent.

But Aerojet’s business with ULA, for which it supplies RL-10 upper-stage and RS-68 main-stage engines, was down sharply during the quarter. Net sales on the RL-10 were $26.8 million, a decline of nearly 30 percent, while for the RS-68 net sales were $24.9 million, down by more than 30 percent.

Warren Ferster is the Editor-in-Chief of SpaceNews and is responsible for all the news and editorial coverage in the weekly newspaper, the spacenews.com Web site and variety of specialty publications such as show dailies. He manages a staff of seven reporters...