Cygnus Arrives at ISS Despite Damaged Solar Array

Northrop Grumman’s Cygnus cargo spacecraft is safely berthed to the International Space Station today even though one of its two solar arrays was damaged during launch. NASA astronaut Nicole Mann used Canadarm2 to capture the spacecraft early this morning and ground controllers later installed it onto a docking port allowing its more than 8,200 pounds of equipment and supplies to be offloaded.

The 18th Cygnus cargo resupply mission, NG-18, was launched on a Northrop Grumman Antares rocket on Monday morning from Wallops Island, VA  The launch appeared to go smoothly, but NASA soon announced that one of the two circular UltraFlex solar arrays did not deploy.

Cygnus does not dock to ISS using its own propulsion system like SpaceX’s Cargo Dragon and Russia’s Progress, but berths with it like Japan’s HTV, the original version of SpaceX’s Dragon, and the discontinued European Space Agency’s ATV. All of those get close enough to ISS to be within range of Canadarm2. Astronauts use the arm to grapple the spacecraft and move it over to a docking port where ground controllers take over and install it onto the port. When the mission ends, the process is reversed and the spacecraft is released to continue its mission. All except Dragon are used for trash disposal and burn up reentering the atmosphere.

NASA had to weigh the risks of berthing Cygnus with one array in an undetermined state as Dina Contella, ISS operations integration manager, explained on Monday: “So if [the array] ends up partially deployed, then, you know, it could jiggle upon capture or berthing or it could come open. So those are the types of things and risk assessment that we’ll be doing if necessary.”

They decided to go ahead and Mann grappled Cygnus without incident at 5:20 am ET this morning. As it turned out, the array’s boom was deployed, but the fan-shaped panels did not unfurl.

Northrop Grumman said in a press release this afternoon that the array didn’t open because debris from an acoustic blanket on the Antares rocket became lodged in one of its mechanisms when the rocket and spacecraft separated.

“During a rocket stage separation event, debris from an Antares acoustic blanket became lodged in one of the Cygnus solar array mechanisms, preventing it from opening,” said Cyrus Dhalla, vice president and general manager, Tactical Space Systems, Northrop Grumman. “Successful berthing was achieved thanks to Cygnus’s robust design and the resilience and ingenuity of the NASA and Northrop Grumman teams.”

Cygnus is delivering 8,265 pounds of equipment, scientific experiments, food and other supplies. During a pre-launch press conference on Saturday, Northrop Grumman’s Steve Krein, Vice President for Civil and Commercial Space Programs, said the spacecraft was filled to the brim with just “one pound of margin” left.

Among the cargo is a bracket, or “mod kit,” needed for a spacewalk scheduled for next Tuesday, so that now can go ahead as planned. It is the first of three spacewalks over the next several weeks to install ISS Roll Out Solar Arrays (iROSAs) to increase the space station’s power supply.