Cygnus CRS-2 NG-25

Cygnus NG-25 is Northrop Grumman’s twenty-fifth resupply flight to the Station, the third launched on a Falcon 9 since the retirement of Antares 230+ left the cargo freighter without a rocket. The vehicle carries roughly 3,800 kg of food, hardware and experiments, and stays berthed at the nadir port of the Unity module for about three months before being filled with rubbish and burned up over the Pacific. The end of every Cygnus is a small bonfire seen from no window.

A spacecraft without a rocket

Cygnus was originally designed to fly on Northrop Grumman’s own Antares rocket, launching from the Mid-Atlantic Regional Spaceport at Wallops Island, Virginia. When the Antares 230+ variant was retired — its RD-181 engines, built in Russia, became unavailable — Northrop needed a ride for its freighter. The solution was straightforward: put Cygnus on a SpaceX Falcon 9 instead. The switch required adapter hardware and some software changes, but the vehicle itself is largely the same.

The arrangement is commercially unusual — Northrop is paying its competitor to launch its spacecraft — but it keeps the cargo flowing. NASA benefits from having multiple resupply providers, even if two of them now share the same rocket.

How Cygnus operates

Unlike Cargo Dragon and HTV-X, Cygnus does not dock autonomously. It approaches the Station under its own power, then parks at a predetermined distance. The crew uses the Canadarm2 robotic arm to grapple the vehicle and berth it to the Unity module’s nadir port. The capture is a manual operation — an astronaut sits at the robotics workstation in the Cupola, watching through the windows while controlling the arm.

Once berthed, the crew opens the hatch and begins transferring cargo — bag by bag, rack by rack. The process takes several days. Cygnus stays attached for roughly three months, serving as additional storage space. During that time the crew gradually fills it with waste.

The Saffire experiment

Tucked among the science racks on this flight is the Saffire-VII fire-safety payload — a deliberate burn of a fabric panel inside the vehicle after it has undocked. The experiment runs only once Cygnus is empty and on its way to disposal. Cameras inside the sealed vehicle record how flames spread in microgravity — data that is impossible to gather on the Station itself for obvious safety reasons. You set fire to the spacecraft you are about to throw away, and you film it on the way down.

The results feed into the materials testing and fire-suppression design for the next generation of crew vehicles and future space stations.

Departure

At the end of its stay, Cygnus is unberthed by the robotic arm and released. It performs a series of deorbit burns and re-enters the atmosphere over the South Pacific, where it and everything inside — the waste, the Saffire experiment results, the vehicle itself — burns up completely.