Northrop Grumman’s first Cygnus XL vehicle was jettisoned on its way to the International Space Station following a pre-sunset launch from Cape Canaveral Sunday evening.
SpaceX’s Falcon 9 rocket thundered off the pad at Space Launch Complex 40 (SLC-40) at 6:11 a.m. EDT (2211). About 8 minutes after taking off, the booster shook the Space Coast with a sonic boom as it touched down at Landing Zone 2 at Cape Canaveral Space Force Station.
This was just the fourth flight for this booster with the tail number B1094. It previously launched a batch of Starlink satellites along with two astronaut missions to the ISS: Axiom Mission 4 and NASA’s Crew-11.
This was one of the final landings at this site as SpaceX builds a new landing pad adjacent to its launch pad at SLC-40. The company expects this new site to be operational by early 2026.
More than 14 minutes into the flight, the Cygnus XL spacecraft was released from the Falcon 9 rocket’s upper stage and it began its more than two-day journey to the space station. NASA confirmed that the two, circular UltraFlex solar arrays successfully deployed about an hour and a half after launch.
The cargo vehicle is scheduled to be berthed to the ISS by NASA astronaut Jonny Kim on Wednesday, Sept. 17. The Cygnus XL is expected to be captured by the robotic arm on the ISS around 6:35 a.m. EDT (1035 UTC) and berthing will begin around 8 a.m. EDT (1200 UTC).
“Our ISS team has worked hand-in-hand with Northrop Grumman to assess how their spacecraft changes affect ISS in our operations,” said Dina Contella, the deputy manger for NASA’s ISS Program, during a prelaunch briefing. “For example, on the ISS side, we had to consider thermal and life support impacts from having a larger vehicle berth to the ISS and we had to assess impacts to the Canadian robotic arm operations.”
The Cygnus XL has about 33 percent greater volume for cargo as compared to the predecessor Cygnus vehicle. Ryan Tinter, vice president of Civil Space Systems at Northrop Grumman, said this new spacecraft is about the size of two Apollo command modules put together.
Cygnus XL separation confirmed. The spacecraft is expected to arrive at the @Space_Station for capture in ~60 hours on Wednesday, September 17 at 6:35 a.m. ET pic.twitter.com/hnp6aqjRK3
— SpaceX (@SpaceX) September 14, 2025
The mission, called NG-23, is the 22nd flight for a Cygnus spacecraft as part of the Commercial Resupply Services 2 contract managed by Northrop Grumman.
“To date, we’ve delivered over 71,000 kg of supplies and science and beyond to the space station,” Tinter said. “Now, as a commercial contractor as well, we’re always partnered with NASA and our customers to understand what new capabilities are needed within what we’re offering.”
Keeping with tradition, Northrop Grumman named the spacecraft after an astronaut who left and impactful legacy. This vehicle was dubbed the S.S. William “Willie” C. McCool, in honor of the pilot Space Shuttle Columbia of the ill-fated STS-107 mission.
This Cygnus XL spacecraft launched with more than 11,000 pounds (4,990 kg) of science and supplies onboard. Once attached to the ISS, it’s scheduled to remain on orbit until the late-spring timeframe.
NASA is planning to un-berth the vehicle temporarily in November to clear a path for the arrival of a crewed Soyuz spacecraft on the MS-28 mission. Contella said if teams determine that they are unable to re-berth Cygnus, it will be stuffed with trash and released in November.
“(Japan’s) HTV-X is berthed during this time and it will also provide significant trash removal,” Contella said. “So, un-berthing Cygnus earlier would not be a major problem.”
New science onboard
Among the thousands of pounds of cargo onboard the Cygnus XL spacecraft are hardware and supplies that will support more than 50 differs scientific studies and research facilities, according to Dr. Liz Warren, associate chief scientist for NASA’s ISS Program Research Office.
One of those is a follow up experiment looking at how to manage a zero boil off situation for propellant storage tanks in low Earth orbit. It’s called the Zero Boil-Off Tank Noncondensables (ZBOT-NC) and it’s managed by Case Western Reserve University and NASA Glenn Research University.
“Data from this investigation will be used to validate a state of the art, two-phase computational fluid dynamics model for long-duration storage of cryogenic fluids in space, which in turn, can be used to inform engineering design currently,” Warren said.
Dr. Mohammad Kassemi, the principal investigator from Case Western Reserve University, said this work will be applied by NASA’s Science Mission Directorate to help both Blue Origin and SpaceX with their plans for on-orbit propellant transfers. That’s a key part of their proposals for returning humans to the Moon through the Human Landing System piece of the Artemis program.
“We are validating these models across gravity levels, across fluid types and across spatial dimensions, you know, from a small tank to a large tank, Kassemi said. “What allows us to do that is the model, but the key for the model is to be validated and the microgravity data that the ISS allows us to acquire is very valuable, especially when we talk with the U.S. industry, with aerospace companies.”
Bristol Myers Squibb will also be conducting a crystal growth experiment using Redwire Space’s Pharmaceutical In-space Laboratory. It’s called Pharmaceutical In-space Laboratory 11 (ADSEP-PIL-11).
“[It] continues ongoing work growing crystals of pharmaceuticals on the ISS to see whether microgravity alters their structure,” Warren said. “In this phase of the work, researchers are exploring products with potential applications in cardiovascular, immunologic, cancer and neurodegenerative diseases.
“On Earth, mixed-crystal products experience slow crystal formation, poor crystal shape, deformation. Researchers here expect that microgravity conditions will enable larger, more uniform crystals, which as been seen in many other crystallization experiments on the ISS.”
Warren said researchers are hoping to bring some of these crystals back to Earth to make larger batches of them.
Future of Cygnus
The launch of the NG-23 mission came months earlier than was originally scheduled. The Cygnus spacecraft for the NG-22 mission was damaged during transport to the Kennedy Space Center in Florida and it was deemed unable to fly during its original slot earlier in 2025.
NASA and its partners on the ISS agreed to shuttle the launch schedule and move up the SpX-32, SpX-33 and NG-23 missions to compensate for the issues.
“The exact details on the NG-22 configuration, we’re still working through that, but NG-22 will fly,’ Tinter said. “The NG-22 mission will be manifested and again, we’re working with NASA to determine, as we complete the path forward there, exactly what the timing will be.”
Because of the schedule shuffle, the flight of NG-23 was the last of three announced missions that featured a SpaceX Falcon 9 rocket carrying a Cygnus spacecraft. However, prior to launch, Tinter said NG-24 would also fly on a Falcon 9 rocket in 2026.
“I’d have to go back and see exactly when, but we are all set and have been for a little while now to make sure that we were able to launch on time for NASA here through the Falcon 9,” Tinter said when asked about the timing of this expanded contract during a prelaunch briefing.
Northrop Grumman is working on a new medium-class launch vehicle called the Antares 330 in partnership with Firefly Aerospace. The Antares 230+ was retired in August 2023 as a result of its use of Russian-built RD-181 engines. The U.S. Congress mandated an end to a reliance on Russian rocket engines as a result of Russia’s 2014 invasion of Crimea.
“We’re making great progress on the Antares 330 and that’s getting queued up to be used at some point and ready to go in 2026,” Tinter said.