SSVP docking system

SSVP was initially conceived in 1967 by the TsKBEM design bureau for use on the then-planned OIS military space station. Though OIS never flew, in 1970 the design was selected for use on the Salyut and Almaz space stations. This led to a number of redesigns to reduce damage from accidental loads.) The modern version of SSVP is SSVP-G4000. An upgraded version, designed for reusability and to provide a wider tunnel, is planned for use on the next-generation Orel spacecraft. ==Design==

SSVP consists of two components; an active probe, and a passive drogue. The probe enters the drogue, and its tip is grasped by soft-capture latches which are then retracted using electrically driven motors to provide close alignment. Eight hard-capture locks then firmly attach the two spacecraft. After hard docking, the pressure between spacecraft is equalized using the Interface Leak Check System. The port contains a transfer tunnel, with an internal diameter of . The ring surrounding this tunnel also includes a number of connectors, providing for transfer of power, data, and fuel between two docked vehicles. ==Hybrids==

A "hybrid" version, combining the design of SSVP and APAS-95, is also available, used for permanent docking of space station modules. This version uses the probe-and-drogue design of the standard SSVP, but with a hard-dock collar from APAS-95. The APAS-95 collar has twelve latches instead of the eight of standard SSVP. This variant is known as SSVP-M8000. ==Adapter Ring==

It converts passive Hybrid SSVP-M8000 Docking System to passive SSVP-G4000. The docking ring initially used for Soyuz MS-18 and Progress MS-17 docking on Nauka until detached by Progress MS-17 inflight for Prichal module arrived on ISS. This adapter is termed as SSPA-GM. It was made for the Nauka nadir and Prichal nadir ports of the International Space Station, where Soyuz and Progress spacecraft had to dock to a port designated for modules. Before removal of SSPA-GM, the docking ring is in diameter; that becomes after removal. ==See also==