Spaceflight Insider

Cygnus unberthed, begins weeklong free flight

OA-7 Cygnus at ISS

Cygnus, still attached to the Unity module, as seen from the International Space Station’s cupola window while the complex was flying over Florida sometime in May 2017. Photo Credit: NASA

The S.S. John Glenn Cygnus spacecraft was released from the International Space Station at 9:10 a.m. EDT (13:10 GMT), June 4, 2017, after some 44 days berthed to the outpost’s Unity module.

Cygnus carried to the ISS nearly 7,700 pounds (3,500 kilograms) of experiments, food, and crew supplies for the Expedition 51 and 52 crews. Now, with the craft loaded with unneeded equipment and trash, the spacecraft will begin the final leg of its journey: a weeklong free flight to conduct a remote fire experiment called SAFFIRE III.

While Cygnus was performing its three-minute departure burn, Expedition 52 crew member Jack Fischer said the spacecraft’s performance over the last 1.5 months was a testament to the Orbital ATK team that supported it throughout its mission.

“Every detail, from the flawless system operations to the perfectly labeled straps to a well-orchestrated symphony of cargo and science logistics, we can’t say enough about the team we have the privilege to represent here on orbit and want to send our best wishes on the final phase of [Cygnus’] mission,” Fischer said. “Godspeed and fair winds S.S. John Glenn. It has been an honor.”

Built by Orbital ATK, and launched into space on April 18 atop a United Launch Alliance Atlas V 401 rocket, the spacecraft arrived at the outpost on April 22. The 21-foot (6.4-meter) long spacecraft was subsequently captured by the robotic Canadarm2 and berthed a few hours later.

Over the course of the spacecraft’s time berthed, cargo was transferred out of the pressurized compartment and distributed throughout the outpost.

Now that the spacecraft is in its final free-flight phase, once Cygnus is at a safe distance from the outpost, teams on the ground will remotely activate the SAFFIRE III experiment. This is the third in a series of fire experiments that are designed to help researchers understand how flames spread in microgravity.

Once the experiment is conducted and all the data downlinked to Earth, Cygnus will be commanded to deorbit over the Pacific Ocean where it will burn up. What survives re-entry, if anything, will fall harmlessly into the ocean. This is expected to occur on June 11, 2017.

Video courtesy of NASA



Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity. You can find him on twitter @TheSpaceWriter.

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