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Farewell, Pirs; ISS module decommissioned, set for destructive reentry - NASASpaceFlight.com - NASASpaceflight.com
Jul 25, 2021 3 mins, 21 secs
July 25, 2021.

April 21, 2021.

April 21, 2021

After nearly 20 years in orbit serving as a docking port and airlock for the Russian segment of the International Space Station (ISS), the Pirs module — also called Stykovochny Otsek 1, or Docking Compartment 1 (DC-1) — has become the first habitable element of the station to be decommissioned and permanently removed from the orbital complex. 

Pirs was undocked from the nadir port of the Zvezda service module at 06:55 EDT / 10:55 UTC on Monday, July 26 ahead of a planned fiery destruction in Earth’s atmosphere at 10:51 EDT / 14:51 UTC later that day

Pirs’ time at the ISS came to a close after the successful launch of the Nauka multipurpose laboratory module which, after some initial issues post-launch, is on its way to a docking on Thursday, July 29

Following the collapse of the Soviet Union in December 1991, Mir-2 emerged the following year as a four-module station — including a Docking Module, which would become Pirs.  In 1993, Mir-2 officially merged with the long-delayed NASA/European/Japanese/Canadian space station Freedom project to become the building blocks of the International Space Station

At the time of the ISS’s inception, Pirs was meant to be a temporary addition to solve an immediate issue of a lack of docking locations on the Russian side.  The main nadir and zenith ports on the Zvezda service module were designed for the larger, main modules Russia originally planned. 

They were not meant for Soyuz and Progress dockings, significantly limiting and complicating resupply and crew mission scheduling.  Pirs would help alleviate that issue by adding a third Soyuz/Progress docking port by attaching itself to Zvezda’s nadir port

Following the successful launches of the Zarya control module and the Zvezda service module, Pirs was launched on September 14, 2001 at 23:34:55 UTC atop a Soyuz-U booster from the Baikonur Cosmodrome in Kazakhstan

After being placed in an initial parking orbit, a modified Progress power and propulsion section attached to the base of Pirs deployed its solar arrays and began maneuvering the module up to the ISS’s orbital altitude following a two-day rendezvous profile

Pirs successfully performed an automated docking to Zvezda nadir at 01:05 UTC on September 17, 2001.  The Progress power and propulsion module was disconnected from Pirs on September 26, clearing the passive Soyuz/Progress docking port

At the time of its arrival, the original plan called for Pirs be removed and replaced in 2006 with the Universal Docking Module, a much larger and multifunctional component of the ISS

After Pirs’ arrival at the station, three spacewalks were performed by the three-person Expedition 3 crew to finalize electrical and data connections between Pirs and Zvezda.  Two additional Strela cranes were also delivered for the module via Space Shuttles Discovery and Atlantis on the STS-96 and STS-101 missions, respectively

The first spacecraft to dock with Pirs was the Soyuz TM-33 crewed vehicle, which relocated from the Zarya nadir port over to Pirs nadir on April 20, 2002.  Physical docking took place at 09:37 UTC that day

A series of two spacewalks in November 2020 and June 2021 to begin the process of disconnecting Pirs from the ISS saw cosmonauts reroute cables and data lines, move Strela cranes, and temporarily stow items from the module that needed to stay on exterior platforms

On Saturday, July 24, Russian crewmembers Oleg Novitsky and Peter Dubrov closed and locked the hatches of Pirs and the Zvezda nadir ports, performing subsequent leak checks to ensure a good seal ahead of physical separation of the module

On Monday morning, July 26, at 06:53 EDT / 10:53 UTC, commands were sent to physically remove the bolts that mated Pirs to Zvezda 20 years ago.  This three minute, automated process culminated at 06:55 EDT / 10:55 UTC with physical separation of the Pirs module from Zvezda

That moment marked the first time a module of the International Space Station was permanently removed from the complex

At the moment of separation, springs pushed the Pirs/Progress MS-16 vehicle away from the station.  Progress MS-16 docked with Pirs on February 17, 2021 at 06:27 UTC as part of a resupply mission with an added twist: Progress MS-16 would never undock from Pirs if all went well with Nauka’s launch

(Lead image. Pirs leaves the ISS on July 26, 2021. Credit: NASA)

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