After Four-Month-Plus Stay, NG-19 Cygnus Cargo Ship Leaves Space Station

After more than four months spent moored at the International Space Station (ISS), Northrop Grumman Corp.’s NG-19 Cygnus cargo ship—named in honor of Dr. Laurel Clark, a Navy flight surgeon, deep-sea diver and crew member on shuttle Columbia’s final voyage, STS-107 in early 2003—departed the sprawling orbital complex early Friday, bound for a January deorbit and destructive re-entry. Separation of NG-19 occurred at 8:05 a.m. EST and now leaves the Earth-facing (or “nadir”) port of the station’s Unity node free for its next resident: the NG-20 Cygnus, due to arrive late next month.

Ahead of NG-19 lies several weeks of autonomous science and technology research, including the sixth and final iteration of the Spacecraft Fire Safety (SAFFIRE-VI) experiment, developed by NASA’s Glenn Research Center (GRC) in Cleveland, Ohio. This long-ranging series of investigations sought to understand combustion, smoke behavior and flame-spreading characteristics and their impact upon spacecraft habitability.

On five prior Cygnus missions between June 2016 and January 2021, SAFFIRE observations occurred after the cargo ship had departed the ISS and the station’s crew was exposed to no danger. Its experiments were conducted inside self-contained modules, measuring 3 feet (0.9 meters) x 5 feet (1.5 meters), divided into a sensor-filled avionics bay, high-definition video cameras and signal-processing hardware and a combustion chamber in which samples were burned.

On SAFFIRE-I in June 2016, a piece of Solid Inflammatory Boundary at Low Speed (SIBAL) cloth—a cotton blend on a fiberglass substrate—was ignited by a hot wire, marking the largest in-space fire ever conducted. Five months later, in the final phase of the OA-5 Cygnus mission, the envelope was pushed further by burning nine samples, including SIBAL and Plexiglas and Nomex specimens; the latter typically are used on spacecraft for windows and as fire-retardant materials.

Higher fuel-flow velocities were explored in the SAFFIRE-III burns in June 2017. And in May 2020, SAFFIRE-IV began the first of three final missions to run at lower atmospheric pressures of 8.2 psia and a 34-percent oxygen level, significantly higher than conditions available on Earth.

It will mark a dramatic closure to a mission which got underway last 1 August, with a rousing 8:31:14 p.m. EDT liftoff atop Northrop Grumman’s 133-foot-tall (40.5-meter) Antares 230+ booster from ocean-hugging Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va. The Cygnus cargo ship was laden with more than 8,200 pounds (3,700 kilograms) of equipment, payloads and supplies for the space station’s incumbent Expedition 69 and upcoming Expedition 70 crews.

Waiting on-orbit were Expedition 69 astronauts Warren “Woody” Hoburg and Frank Rubio, who respectively fulfilled prime and backup roles for the robotic capture and installation of NG-19. At 5:52 a.m. EDT on 4 August, the duo oversaw Cygnus’ capture using the station’s 57.7-foot-long (17.6-meter) Canadarm2, after which Mission Control remotely commanded the robotic arm to rotate the cargo ship into position and install it onto Unity’s nadir port interface.

Within days, NG-19’s hatches were open for business as the Expedition 69 crew set about unpacking cargo and supplies. Its suite of experiments ran the gamut from studies of neuron cell cultures to Japanese children’s artwork and from ongoing fire safety investigations, via SAFFIRE-VI, to ionospheric plasma physics.

On 11 August, Cygnus even pulled double duty as an orbit-lifting spacecraft, firing its thrusters for 22 minutes and 48 seconds to boost the ISS altitude by about 0.3 miles (0.5 kilometers) at its orbit’s high point (or “apogee”) and 2.8 miles (4.5 kilometers) at its low point (or “perigee”). The end result nudged the space station slightly higher to 258 miles (422 kilometers) x 262 miles (414 kilometers).

Preparations for NG-19’s departure got underway in October, when Expedition 70 crew members began packing unneeded hardware and trash aboard the cargo ship. Overseeing Thursday’s departure were astronauts Jasmin Moghbeli and Satoshi Furukawa, who closed the hatches yesterday to definitively end its long mission. The SAFFIRE-VI experiments will occupy a sizeable chunk of Cygnus’ remaining time in orbit, with the spacecraft targeted to perform a destructive dive into Earth’s atmosphere next month.

It will mark the figurative return of Laurel Clark, a crew member on Columbia’s ill-fated final mission, more than two decades ago. Honoring Clark continues a longstanding Cygnus tradition, which has seen each consecutive cargo ship named for a figure who played a substantial role in human space exploration.

Prior honorees included Challenger’s Ellison Onizuka, Columbia’s Rick Husband and Kalpana “K.C.” Chawla, moonwalkers Gene Cernan, John Young and Al Bean and Apollo 1’s Roger Chaffee. Added to that list are five other shuttle flyers, legendary “Original Seven” Mercury and Apollo-Soyuz Test Project (ASTP) astronaut Deke Slayton, “Hidden Figures” mathematician Katherine Johnson, former NASA Deputy Administrator James “J.R.” Thompson and Manned Orbital Laboratory (MOL) astronaut selectee Robert Lawrence. Most recently, the NG-18 Cygnus—launched last November—offered a nod to America’s first woman in space, astronaut Sally Ride.

Clark thus becomes the third STS-107 veteran to be honored with a Cygnus name. “We bonded over our shared Midwestern roots and fond connection to Scotland,” said Clark’s former classmate, astronaut Dan Tani, now Northrop Grumman’s director of business development. “I remember, as a new mother herself, Laurel naturally took on a maternal role in our class, always looking out for everyone else and making sure we were all doing well.”

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