NASA Spaceflight.com by Pete Harding April 5, 2021
The SpaceX Crew-1 Dragon Resilience performed a relocation to a new docking port aboard the International Space Station on Monday in order to make way for future crew and cargo vehicles on the U.S. side (which includes Canada, Japan, and Europe) of the orbital complex.
This type of move from one docking port to another, whilst common for the Russian Soyuz vehicles, is a first for a U.S. crew vehicle — as the Space Shuttle previously has no need to relocate ports as it was the sole U.S. human and cargo vehicle requiring docking ports until the Crew Dragon system came online in 2019.
Dragon Resilience’s relocation began at 06:30 EDT/10:30 UTC, whereupon the craft undocked from International Docking Adapter-2 (IDA-2) / Pressurised Mating Adapter-2 (PMA-2) on the forward port of the Harmony module.
The 45-minute procedure saw Resilience back away from the Station to 60 meters before commanding its Draco thrusters to perform an automated flyaround, which involved maneuvering through a 90-degree arc to align with PMA-3/IDA-3 on the zenith (space-facing) side of Harmony.
Dragon Resilience then initiated the final approach, using its rendezvous systems to guide itself and its four occupants back toward the Station for a re-docking at 07:15 EDT/11:15 UTC.
All four of Resilience’s crewmembers – NASA astronauts Victor Glover, Mike Hopkins and Shannon Walker and JAXA astronaut Soichi Noguchi – were onboard the spacecraft during the relocation to protect against the unlikely scenario of a failed redocking.
If the crew were not onboard their spacecraft during a relocation, and the craft failed to re-dock, it could leave them stranded on the Station awaiting rescue.
Therefore, crews are always placed aboard their spacecraft during port relocation operations as the craft they launched with is usually their emergency evacuation vehicle as well as their ride back to Earth.
For today’s relocation, the Dragon crew also wore their tailor-made SpaceX pressurize suits to protect them from a highly unlikely depressurisation of the capsule in the event of an off-nominal approach and a contact between Dragon and the Station.
Relocations are usually timed, as well, so that if an off-nominal situation occurs and the need to come home somewhat immediately arises, the craft and crew are in a good position — both physically from an orbital mechanics standpoint and temporally from a timeline perspective — to return home within a few orbits if needed.
The immediate purpose of the relocation was to clear the PMA-2/IDA-2 port for the arrival of the Crew-2 Dragon Endeavour capsule, which is set to launch to the ISS on April 22 with its crew of NASA astronauts Shane Kimbrough and Megan McArthur, ESA astronaut Thomas Pesquet, and JAXA astronaut Aki Hoshide.
This will be followed on April 28 by the undocking and return to Earth of Crew-1 Dragon Resilience, which will vacate the PMA-3/IDA-3 port and clear the way for the docking of the CRS-22 Cargo Dragon in June – which is the ultimate purpose of Resilience’s relocation.
More:
https://www.nasaspaceflight.com/2021/04/dragon-resilience-performs-port-relocation/
