WASHINGTON — A Cygnus cargo spacecraft is set to launch to the International Space Station on the final flight of a version of an Antares rocket with Russian and Ukrainian components.

NASA and Northrop Grumman completed a launch readiness review July 30 for the NG-19 mission, approving plans to launch the spacecraft on Aug. 1 at 8:31 p.m. Eastern from the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia. Forecasts project an 80% chance of acceptable weather for the scheduled liftoff.

The Cygnus is carrying nearly 3,750 kilograms of cargo to the station, including experiments, hardware and crew supplies. An on-time launch would allow the spacecraft to arrive at the station early Aug. 4 and remain there at least three months.

This is the first Cygnus mission since the launch of NG-18 in November 2022. On that mission, one of two solar arrays on the Cygnus failed to deploy, but the spacecraft was able to carry out its mission with the single array.

The solar array did not deploy because debris that lodged in the hinge of the array, preventing it from unfolding, said Steve Krein, vice president of civil and commercial space at Northrop Grumman, during a July 30 briefing. “There’s really no redesign of modifications required” to the spacecraft, he said.

That debris came from acoustic blankets in the interstage portion of the Antares during stage separation. “It wasn’t a clean separation and we created some debris, and unfortunately a piece of the acoustic blanket became lodged in one of the Cygnus solar arrays,” said Kurt Eberly, director of space launch programs at Northrop Grumman. He said the company implemented unspecified corrective actions that have been reviewed by NASA ahead of the NG-19 launch.

The NG-19 launch will be the last of the current version of the rocket, called Antares 230+. That version of the rocket uses a first stage manufactured by Ukraine’s Yuzhnoye State Design Office and Yuzhmash Machine Building plant, with RD-181 engines from Russian company NPO Energomash.

When Russia invaded Ukraine in February 2022, triggering sanctions that largely cut off Russia’s space industry from the West, Northrop Grumman said it had components for two more Antares launches, the NG-18 and -19 missions. In August 2022, Northrop announced it was partnering with Firefly Aerospace to develop a new version of the rocket, Antares 330, using a domestically manufactured first stage and engines.

Eberly said the companies have completed critical design reviews (CDRs) for the structure of the first stage as well as Firefly’s Miranda engines that will power it. A system-level CDR is scheduled for September, and Firefly plans to start hot-fire tests of Miranda this fall.

When Northrop and Firefly announced their partnership last August, they expected to start launching the Antares 330 by late 2024. That has now slipped to the summer of 2025, he said.

While Antares 330 is in development, Northrop will launch three Cygnus missions on SpaceX Falcon 9 rockets. Despite the delay in the introduction of the new Antares, Eberly said Northrop doesn’t anticipate buying additional Falcon 9 launches. “We’re planning NG-20, -21 and -22 missions on Falcon 9, and then the plan is to return to Wallops” for NG-23 and beyond on Antares 330.

The new first stage is more powerful than the existing one, increasing payload performance for the rocket from 8,120 kilograms for Cygnus ISS missions to 10,500 kilograms. “We think that opens the doors for other markets for us,” Eberly said.

The Antares 330 also serves as a transition for a future rocket, currently known simply as the Medium Launch Vehicle, where the solid-fuel upper stage will be replaced by one using a version of the Miranda engine. That will further increase the vehicle’s payload capacity to 16,000 kilograms.

“With that increased capability, coupled with the domestic supply chain, we think we’re going to be able to address other markets, including NASA civil and DOD markets, as well as commercial, in addition to cargo resupply,” he said.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...