Cygnus XL Overcomes Engine Glitch to Deliver 11,000 Pounds of Supplies to the ISS

Engine hiccup and the quick fix

When the Cygnus XL lifted off on Sep 14 aboard a Falcon 9, we all expected a smooth ride to the orbital lab. The launch went off without a hitch, the solar arrays unfurled, and the spacecraft settled into its initial orbit. Then, on Sep 16, the main engine that was supposed to fire twice to raise the vehicle’s altitude shut down early.

Flight controllers at NASA and Northrop Grumman stared at the telemetry and saw a safety flag pop up. The culprit? An overly cautious software limit that told the engine to quit before it finished the burn. It wasn’t a hardware failure—just a protective trigger that acted a little too quickly.

Within minutes, engineers were crunching numbers, swapping out burn durations, and drafting a new rendezvous sequence. The revised plan added a longer, lower‑thrust burn later that day, buying the spacecraft the extra time it needed to climb to the proper altitude. The team confirmed that all other systems—power, communications, attitude control—were still green, so they pushed ahead.

That decision cost the mission a 24‑hour slip. Instead of docking on Sep 17 as scheduled, the Cygnus XL arrived on Sep 18. The delay was a reminder that even with decades of experience, spaceflight still hinges on the ability to adapt in real time.

Mission payload, docking, and what comes next

When the ISS passed over Africa on Sep 18, astronaut Jonny Kim extended the Canadarm2 and gently grappled the **Cygnus XL**. Zena Cardman was on standby, ready to assist if anything went sideways. Within a few minutes, the spacecraft was secured and berthed to the Unity module’s Earth‑facing port.

The extra‑large version of the Cygnus can carry more than any of its predecessors. This flight stowed roughly 11,000 lb (about 5 tons) of cargo, broken down into several categories:

• Food and water for the seven‑person crew, stretching their supply horizon by weeks.
• Science kits ranging from protein crystal growth experiments to new microgravity combustion studies.
• Spare parts for life‑support gear, including a replacement flush‑system component for the station’s toilet.
• Hardware upgrades for the station’s power and air‑filtration units.

Beyond the tangible goods, the mission carried a symbolic flag. Northrop Grumman named the capsule the S.S. Willie McCool, honoring the shuttle pilot who perished in the Columbia disaster. It’s a nod to the people who paved the way for today’s commercial resupply era.

This was the 23rd CRS (Commercial Resupply Services) flight for Northrop Grumman, a partnership that began when the company bought Orbital ATK in 2018. The resupply market now has four active players: Northrop Grumman’s Cygnus, SpaceX’s Dragon, Russia’s Progress, and Japan’s HTV‑X, which is slated to return later this year. The Russian Progress docked just a week earlier, delivering 2.8 tons of cargo, underscoring how a multi‑vendor approach keeps the ISS humming.

After the hatch was opened, the crew began transferring supplies, installing the new experiments, and routing spare parts to the appropriate workstations. The Cygnus will stay attached until March 2026, essentially acting as a floating storage locker. When it’s finally filled with trash and decommissioned hardware, a controlled re‑entry will let it burn up in the atmosphere, safely disposing of waste.

What does this episode teach us? First, that software settings designed to keep a spacecraft safe can also cause unexpected delays. Second, the collaboration between NASA and its commercial partners is agile enough to absorb setbacks without jeopardizing the station’s operations. And finally, the continued expansion of the Cygnus XL’s cargo capacity means future missions can bring even more science and support to the orbiting outpost.

With the ISS slated to operate into the late 2020s, and private stations on the horizon, reliable resupply will stay a cornerstone of low‑Earth‑orbit activity. The Cygnus XL’s successful recovery from an engine glitch is a small but significant proof point that the commercial model can deliver, adapt, and keep the research community moving forward.