Russia ditches 20-year-old space station module to clear way for lab’s arrival

A Russian Progress cargo ship undocked from the International Space Station early Monday, taking with it the two-decades-old Pirs airlock and docking compartment to clear the way for Thursday’s arrival of Russia’s new Nauka multipurpose lab module.

With the Progress MS-16/77P supply ship firmly locked to Pirs, hooks and latches holding the docking compartment to the Zvezda service module’s Earth-facing port were commanded open, and the Progress backed away at 6:55 a.m. EDT.

The flight plan called for the Progress to fire its thrusters at 10:01 a.m., setting up a destructive plunge into the atmosphere 41 minutes later. The braking burn was planned to make sure any debris that might survive reentry heating would fall harmlessly into the southern Pacific Ocean.
Undocking originally was planned for last Friday, two days after Nauka’s launch from the Baikonur Cosmodrome in Kazakhstan, but problems with the lab’s navigation and propulsion systems prompted Russian flight controllers to delay Pirs’ departure.

Finally, after several anxious days of troubleshooting, Nauka’s propulsion system was restored to normal operation, and two successful tests of its KURS navigation and rendezvous system were carried out. While few details were provided, Russian mission managers then cleared Pirs and Progress for departure.

Pirs was launched on September 14, 2001, three days after the 9/11 attacks. It served as a docking port for visiting Soyuz crew ships and Progress freighters for nearly 20 years and as an airlock for Russian spacewalks.

The much larger 44,000-pound Nauka module features an airlock and docking port, expanded crew quarters, research space, an additional toilet, oxygen generator, solar arrays and a European Space Agency-built robot arm. Nauka’s thrusters also will help provide roll control to keep the station properly oriented.