Running a day late because of a software issue, Northrop Grumman’s Cygnus XL cargo ship caught up with the International Space Station early Thursday and then stood by while the lab’s robot arm latched onto a grapple fixture to wrap up a successful, if extended, rendezvous.
The capture came after Northrop Grumman engineers adjusted the sensitivity of main engine fault detection software that prematurely triggered shut downs during two rendezvous thruster firings Tuesday.
As it turned out, the main engine was healthy all along and once the software was adjusted, the spacecraft was able to press ahead with the rendezvous, pulling up to a point just below the station so robot arm operator Jonny Kim, assisted by Zena Cardman, could capture the ship.
“A big congratulations to the NASA and Cygnus teams for a successful Cygnus launch, rendezvous and capture,” Kim radioed mission control. “Adapting and overcoming unforeseen challenges is something we do at NASA, and I’m very proud to be a part of this team.”
Unlike SpaceX’s cargo Dragon and Russian Progress freighters, which carry out autonomous dockings at their respective ports, the Cygnus was designed to be captured by the station’s arm and pulled in for berthing.
After locking onto the Cygnus XL at 7:24 a.m. EDT, Kim handed off arm operations to flight controllers at the Johnson Space Center in Houston so the ship could be pulled in for berthing at the Earth-facing port of the central Unity module.
Northrop Grumman names its cargo ships after notable figures in the space community. The Cygnus XL was named in honor of shuttle pilot William “Willie” McCool, who lost his life in the 2003 Columbia disaster.
Space station astronaut Mike Fincke, a member of the 1996 astronaut class along with McCool, said he was “a gifted pilot, a devoted crewmate and a man of deep humility, his life continues to inspire us.”
“To see a ship bearing his name safely arrive at the station is a reminder that his courage and kindness are still circling our beautiful planet Earth.”
On board: more than 5 tons of needed spare parts, research material and crew supplies, including holiday treats for the station crew.
“The (Cygnus) is packed with consumables, like nitrogen, oxygen, food and toilet parts, and it has a large number of spare parts that are required for systems like, for example, our urine processor,” said Dina Contella, deputy manager of the space station program at the Johnson Space Center.
“We’re stocking up on these items since we were short over the past year, and we’d like to have a good reserve for the future.”
That shortfall was caused, in part, by damage an earlier Cygnus suffered during shipment from a sub-contractor in Europe to Cape Canaveral. That vehicle is still grounded pending analysis and repairs.
Sunday’s launch of the Cygnus XL marked the maiden flight of an upgraded version of the cargo ship, which is about 5 feet longer than the original, allowing it to carry about 2,600 pounds of additional cargo.
NASA pays for cargo delivery flights using Cygnus and Dragon spacecraft. To date, SpaceX has successfully carried out 32 Dragon resupply missions while Northrop Grumman has executed 21 successful flights, including the current mission.
Bill Spetch, operations integration manager for the space station, said the resupply flights, “and especially this great capability that Cygnus brings and the amount of cargo that it brings to us, is critical to keep us running smooth and doing the things that we need … to do the research.”
