After a postponement, imposed by the doctors of the TzUP (the Moscow flight control center), to allow cosmonauts Dmitri Petelin and Sergei Prokopiev more rest, at 21:30 UTC on May 3, 2023, the spacewalk n. 57 began from the Russian segment of the ISS.
This activity, which lasted about six hours, allowed the movement of the ShK (Russian Shluzovaja Kamera) airlock, parked next to the Rassvet module, in its final position hooked to one of the side hatches of the Nauka module.
During the EVA, Commander Prokopiev took the opportunity to throw 5 kg of equipment into space for scrap. The package with the waste material will burn without danger on re-entry into the upper atmosphere.
Spacewalker Sergey Prokopyev jettisons a 5-kilogram bundle of obsolete hardware into the vacuum of space to harmlessly burn up in the Earth's atmosphere. Watch now… https://t.co/yuOTrYNGst pic.twitter.com/mpnwm2woNO— International Space Station (@Space_Station) May 4, 2023
A real move
The two cosmonauts, with the help of the ERA robotic arm, maneuvered from inside the ISS by their colleague Andrei Fedyaev, first disconnected the ShK connections from the Rassvet module. Then, they freed the airlock docking hatch and the relative docking system from thermal protective covers and dropped the ShK from the Rassvet.
At this point, the ERA arm, remotely guided, first hooked up to the ShK and then, transporting it to the new position, attempted docking. But an alignment error during the final docking procedure required the unlocking of the mechanical arm joints and, with the manual intervention of Petelin and Prokopiev, it was possible to consolidate the coupling to the Nauka module by restoring the wired connections of the airlock.
A whole new docking system… Or maybe not?
Together with the peculiarities of the ShK, which we discussed in another article of ours, this operation sees the debut of a hybrid coupling system, never used until now, which arises from the experience gained with the Apollo-Soyuz and Shuttle-Mir missions.
The system used on US and Chinese spacecraft, the International Docking System, derives from the APAS-89 created for the Shuttle-Mir program. It is an androgynous system that allows each of the parts to be hooked in a stable way to perform the function of the active or passive vehicle. It was born, at the time, to meet any rescue needs for a damaged spacecraft.
An androgynous system does not need to have a vehicle equipped with a passive adapter and another with an active adapter, as, for example, happened for the Apollo or still happens today for the Soyuz or the Progress. To hook up the ShK it was decided to simplify the APAS-89 system, eliminating the components of the actuators which allow the docking ring to perform the active or passive function indifferently.
The petal structure which serves as a guide for a probe, called ASA-M ( Agregat Stykovochny Aktivny – Modifitsirovanny, Active coupling apparatus – Modified) simplified compared to that of the Soyuz, hooks a cone, called ASP-M Agregat Stykovochny Aktivny – Modifitsirovanny, Active coupling apparatus – Modified) also similar but simplified to the one used in Russian ships.
To switch from an active to a passive configuration, simply replace the disc inside the docking ring. An androgynous system with hybrid characteristics, for the benefit of less weight, fewer moving parts, and maximum simplification.