[FPSPACE] The Soyuz avionics toroidal tank - a theory (David Anderman)

[Mark Wade]

The toroidal tank was specifically described as being used for housing
rendezvous system electronics. In the original Soyuz A design it was
to have been jettisoned after docking with the Soyuz B trans-lunar or
high-orbit stage (source: Korolev i evo delo, summarized at:)

http://www.astronautix.com/craft/soyuza.htm

The 7K-OK initial design conserved this approach, although there was
no need to jettison the tank since it was just used for LEO tests
(although maybe there was a thought it would have been jettisoned in
case of some possible circumlunar scenarios using the Block D stage -
e.g. podsadka, using an L1 equipped with the toroidal tank for the
Igla electronics and a docking collar). It is also possible that it
was retained to allow easy changeout with Kontakt system electronics
in the endless Igla vs Kontakt controversy (which seems to have run
through at least 1965, with both systems then being developed in
parallel, but Igla selected for the initial OK flight version).

When the Soyuz ferry derivative was designed for DOS, with the docking
tunnel forward, the design was committed to Igla. There was no need to
strip all possible mass for a translunar injection. So the electroncis
were moved in the pressurized section of the Soyuz instrument module,
and the toroidal tank deleted...

Toroidal tanks to provide the necessary pressurized compartment for
Soviet avionics appear in quite a number of unmanned spacecraft as
well.

I wonder when, in the design process, the Soyuz received its base
flange. Soyuz A lacks it - one wonders if the original design was for
a tight Voskhod-type shroud, without the 'hammerhead' adapter on the
last stage of the launch vehicle.



-- 
Mark Wade
Encyclopedia Astronautica
http://www.astronautix.com/
astronautix at gmail.com