Cygnus NG-23

NG-23 is a cargo resupply mission to the International Space Station (ISS) under NASA's Commercial Resupply Services (CRS) contract. Operated by Northrop Grumman, the flight successfully launched on September 14, 2025, aboard a Falcon 9 Block 5 rocket. The spacecraft is named S.S. William "Willie" C. McCool in honor of the NASA astronaut who died in the Space Shuttle Columbia disaster in 2003.^[2]

NG-23

NG-23 approaching the ISS
Names	CRS NG-23
Mission type	ISS resupply
Operator	Northrop Grumman
Mission duration	18 days and 5 hours (in progress) 6 months (planned)
Spacecraft properties
Spacecraft	S.S. William "Willie" C. McCool
Spacecraft type	Cygnus XL
Manufacturer	Northrop Grumman Thales Alenia Space
Start of mission
Launch date	September 14, 2025, 22:11:49 UTC (6:11:49 pm EDT)
Rocket	Falcon 9 Block 5 (B1094‑4)
Launch site	Cape Canaveral, SLC‑40
Contractor	SpaceX
Orbital parameters
Reference system	Geocentric orbit
Regime	Low Earth orbit
Inclination	51.66°
Berthing at ISS
Berthing port	Unity nadir
RMS capture	September 18, 2025, 11:24 UTC
Berthing date	September 18, 2025, 14:10 UTC
Unberthing date	November 2025 (planned)
Time berthed	14 days, 13 hours and 2 minutes (in progress)
Reberthing with ISS
Reberthing port	Unity nadir
Reberthing date	November 2025 (planned)
Unreberthing date	March 2026 (planned)
RMS release	March 2026 (planned)
Cargo
Mass	4,911 kg (10,827 lb)[1]
Mission patch Commercial Resupply Services ← SpaceX CRS-33 SpaceX CRS-34 → Cygnus flights ← NG-21 NG-22 →

The mission debuted the Cygnus XL spacecraft configuration, featuring a pressurized cargo module measuring 7.89 meters (25.9 ft) in length, with a payload capacity of 5,000 kilograms (11,000 lb), an increase of 19.5%, and a pressurized cargo volume of 36 cubic metres (1,300 cu ft), an increase of 15.5%.^[3][4]

It is the third Cygnus launch on a Falcon 9, arranged after Northrop Grumman's Antares 230+ was retired in 2023 due to supply chain disruptions stemming from the Russian invasion of Ukraine. A successor, the Antares 300, is under development with no Russian or Ukrainian components.^[5]

Background

Main article: Cygnus (spacecraft)

The Cygnus cargo spacecraft was developed by Orbital Sciences Corporation with partial funding from NASA's Commercial Orbital Transportation Services (COTS) program. It pairs a pressurized cargo module built by Thales Alenia Space—derived from the Multi-Purpose Logistics Module used on the Space Shuttle—with a service module based on Orbital's GEOStar satellite bus.

The first Standard Cygnus flew in 2013, followed by the larger Enhanced Cygnus in 2015. Orbital Sciences became Orbital ATK in 2015 and was acquired by Northrop Grumman in 2018. Since then, Northrop Grumman has continued CRS operations. NG-23 is the eleventh Cygnus mission under the CRS-2 contract.^[6]

Mission

The Pressurized Cargo Module (PCM) was manufactured by Thales Alenia Space in Turin, Italy and assembly of the service module for the NG-23 spacecraft took place at Northrop Grumman's facility in Dulles, Virginia. The service module was integrated with the pressurized cargo module at the Space Systems Processing Facility at the Kennedy Space Center.^[6]

The flight marks the first launch of the Cygnus XL configuration, designed to increase cargo capacity and volume for future Commercial Resupply Services (CRS) missions.^[3] NASA and Northrop Grumman conducted additional certification work to assess the thermal and life-support impacts of the larger design, as well as to evaluate how the Canadarm2 could best accommodate the heavier and longer vehicle.^[7]

NG-23 lifted off on September 14, 2025, at 22:11:49 UTC (6:11:49 pm EDT) aboard a Falcon 9 Block 5 rocket from Space Launch Complex 40 at the Cape Canaveral Space Force Station.^[5] After reaching orbit, the Cygnus XL spacecraft began its planned engine burns to rendezvous with the International Space Station, but two burns shut down early due to a conservative software safeguard. NASA postponed the September 17 docking while engineers worked on an alternate plan, keeping Cygnus at a safe distance.^[8][9] On September 18, astronaut Jonny Kim, with help from Zena Cardman, captured the spacecraft using Canadarm2 at 11:24 UTC. Ground teams at Northrop Grumman's control center in Dulles and NASA's Johnson Space Center in Houston, Texas completed berthing a few hours later.^[7][10]

NG-23 is planned to remain at the station for 200 days, until March 2026. However, the spacecraft will need to be unberthed in mid-November 2025 and held on Canadarm2 away from the docking port, as its position would otherwise interfere with the approach corridor for Soyuz MS-28 at the Rassvet nadir docking port. If this maneuver cannot be carried out, NG-23 would be required to depart in November.^[7]

The Cygnus XL is equipped with "Extend the Lab" capabilities, allowing experiments to be conducted within the spacecraft by delivering power to the experiments, enabling science to take place without unloading them. Cygnus is also capable of performing ISS reboosts if requested by NASA. After unberthing, but before its controlled destructive reentry, the Cygnus XL will conduct a secondary mission to test the PALOMINO electrospray thruster subsystem developed by Revolution Space.^[11]

Manifest changes

NG-23 was advanced in the launch schedule by four months after the indefinite delay of Cygnus NG-22, whose pressurized cargo module was damaged during transportation to the launch site in early 2025. Following inspections, NASA and Northrop Grumman replaced NG-22 with the next available vehicle, NG-23, which launched in September 2025.^[12][13][14]

See also

• Uncrewed spaceflights to the International Space Station