The custom-made shock-absorbing seat for the spacecraft descent module has three functions:
- It serves as a crewmember working station;
- It provides for crewmember withstanding sustained acceleration at launch, nominal or emergency (up to 30 g) reentry of the descent module in the atmosphere;
- It provides for crewmember withstanding descent module/ground impact loads at landing in the nominal and emergency modes (the impact velocity is up to 8 m/s).
Use of a special custom-made couch liner in the seat makes it possible to increase significantly a human capability to withstand G-loads acting on an occupant. The profiled couch liner makes it possible to:
Along with the profiled couch liner, the shock-absorbing seat is also equipped with an energy-absorbing device, which makes it possible to reduce the G-loads in the seat at descent module landing.
- form an optimal and compact crewmember's posture that coincides with the cabin's interior and controls;
- distribute, in a relatively even manner over a large area, static and dynamic pressure of the support on the occupant's body during acceleration;
- limit changing of the body shape under acceleration with various onset rates;
- reduce G-loads acting on the occupant and their onset rates, owing to profiled couch liner deformation.
The Elbrus and Kazbek shock-absorbing seats have passed through comprehensive tests at the Zvezda's and cooperating enterprises' facilities. The capability to withstand acceleration at spacecraft reentry and impact G-loads at landing was checked during the tests with participation of volunteer test-subjects.
The reliable performance of the seat is proved by many years of trouble-free operation in the Soyuz spacecraft and its modifications.