Two Cygnus XL missions to the ISS—NG-23 and NG-24—have been documented in full: from the first mission's departure to the second's launch, journey, and arrival.
First Cygnus XL Mission (NG-23)
The first Cygnus XL spacecraft, designated NG-23 and named the S.S. William "Willie" McCool, launched on September 14, 2025, atop a SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida. This marked the debut flight of the larger, more cargo-capable Cygnus XL variant.
The spacecraft experienced an engine anomaly during its journey to the ISS but resolved the issue, arriving at the station on September 18, 2025, one day later than planned. It delivered approximately 11,000 pounds (4,990 kilograms) of scientific equipment and supplies—a significant increase from previous Cygnus versions, which transported around 8,500 pounds (3,856 kg).
The Cygnus XL departed the ISS on Thursday, March 12, 2026. Ground flight controllers commanded the station's Canadarm2 robotic arm to detach the spacecraft from the Unity module's Earth-facing port. The release occurred at 7:06 a.m. EST (1105 GMT). ESA astronaut Sophie Adenot monitored the Cygnus' systems during its departure.
The spacecraft was scheduled to deorbit on Saturday, March 14, 2026, disposing of several thousand pounds of trash during a controlled reentry into Earth's atmosphere, where it was expected to burn up.
Second Cygnus XL Mission (CRS-24 / NG-24)
Launch
The second Cygnus XL mission, designated NG-24 under NASA's Commercial Resupply Services (CRS-24) contract, was initially scheduled for April 8, 2026, but launched on Saturday, April 11, 2026.
- Launch Time: 7:41 a.m. EDT (1141 GMT)
- Launch Site: Space Launch Complex 40, Cape Canaveral Space Force Station, Florida
- Launch Vehicle: SpaceX Falcon 9 rocket
- Booster: The Falcon 9 first stage completed its seventh flight and landed at Cape Canaveral Space Force Station approximately 8 minutes after liftoff. This booster had previously launched Northrop Grumman's NG-23 mission, NASA's Crew-11 astronaut flight, the Axiom Space Ax-4 astronaut flight, and three Starlink missions.
The Cygnus XL spacecraft separated from the Falcon 9 upper stage about 14 minutes after launch. It was named the S.S. Steven R. Nagel in honor of former NASA astronaut Steven R. Nagel, who flew on four space shuttle missions and died in 2014.
Cargo and Science
The spacecraft carried approximately 11,000 pounds (4,990-5,000 kg) of science equipment, supplies, and logistics for the ISS Expedition 73/74 crew.
Key research and technology demonstrations included:
- Cold Atom Lab Module: A new module for the Cold Atom Lab designed to advance quantum science, with potential applications in improving computing technology and aiding in the search for dark matter. This research aims to enhance understanding of general relativity, planetary composition, and dark matter.
- Therapeutic Stem Cell Production (InSPA-StemCellEX-H2): Hardware intended to increase the production of therapeutic stem cells for research into treatments for blood diseases and cancer.
- Gut Microbiome Study (CBIOMES): Model organisms intended for studying the relationship between organisms and their gut microbiome in a microgravity environment. Researchers will observe changes to identify methods for maintaining microbiome stability.
- Space Weather Prediction (Nanoracks-ITSI): A receiver designed to enhance space weather models by measuring how radio signals from Earth change when passing through the upper atmosphere. This data could refine models that predict the impact of solar activity on critical space infrastructure such as GPS and radar systems.
Additional mission hardware included:
- European Enhanced Exploration Exercise Device: A compact exercise system developed jointly by NASA and ESA, designed to preserve muscle mass and bone health in microgravity. It offers a range of resistance exercises, combining cycling, rowing, resistance training, and rope-pulling/climbing movements.
- Supplemental Heat Rejection Evaporative Cooler: Provides heat rejection for the ISS in case of thermal control system failures, using water evaporation through hollow fiber membranes.
- Ocular Coherence Tomography: A noncontact medical imaging device for producing detailed cross-sectional and 3D images of the eye, replacing a degraded unit in orbit to track changes in crew eye health.
Essential supplies included:
- 8 hatch seal covers
- 2 batteries for the Zarya module
- 3 resupply water tanks
- 1 nitrogen tank and 1 oxygen tank for spacesuit recharging and station pressurization
- 1 pretreat and water dispenser, a spare unit for the Waste and Hygiene Compartment
Journey and Arrival at ISS
- Solar Array Deployment: Scheduled to occur approximately one hour after liftoff.
- Arrival and Capture: The Cygnus XL arrived at the ISS on Monday, April 13, 2026. It was captured by the station's Canadarm2 robotic arm at 1:20 p.m. EDT (1720 GMT).
- Crew Operations: NASA astronaut Chris Williams, an Expedition 74 flight engineer, operated the Canadarm2 for the capture, with assistance from fellow NASA astronaut Jack Hathaway. NASA astronauts Jack Hathaway and Chris Williams oversaw the spacecraft's approach and rendezvous.
- Berthing: Flight controllers on the ground subsequently berthed the spacecraft to the Earth-facing port of the station's Unity Node 1 for cargo unloading.
Mission Duration
The Cygnus XL is scheduled to remain docked at the ISS until October 2026. Upon departure, it will carry several thousand pounds of trash before undergoing a controlled reentry, where it will burn up in Earth's atmosphere.
Context
- Cygnus Program: The Cygnus spacecraft, built by Northrop Grumman, is one of four robotic cargo spacecraft that service the ISS. The others are SpaceX's Dragon, Russia's Progress, and the Japan Aerospace Exploration Agency's (JAXA) HTV-X. While the Dragon capsule is reusable, Cygnus, Progress, and HTV-X are designed to burn up in Earth's atmosphere upon mission completion.
- Mission Numbers: The NG-24 mission is Northrop Grumman's 24th commercial resupply flight to the ISS for NASA.
- International Space Station: The ISS measures approximately 356 feet (109 meters) end-to-end and weighs close to 925,000 pounds (420 metric tons). It orbits Earth at a speed of 17,500 mph (28,000 km/h) at an altitude of approximately 260 miles (420 km). The station has continuously housed humans for over 25 years and is described by NASA as a testbed for long-duration spaceflight challenges and for expanding commercial opportunities in low Earth orbit.