Origin of Orbiter Docking System

(Explorer8939) wrote in
om:

Specifically, what portion of the ODS is actually Russian built? Is it
the upper segment, outfitted with the APAS? Is the entire system
designed and built in Russia? What about the tunnel from the mid-deck
to the ODS? Is this also Russian?

Only the actual APAS docking mechanism, and its associated avionics and
control panel, was built in Russia. The airlock, the truss, the transition
between the airlock and the APAS, and the tunnel adapter were all built in
the US, by Rockwell International (whose space/defense business was later
acquired by Boeing).

Originally, Russia wanted to sell NASA its entire Buran docking system,
which included its own airlock and truss[1]. But many problems arose.
First, the APAS docking ring extended above the moldline of the payload
bay, requiring pyros to jettison it if it didn't retract. Second, the
truss only had one longeron trunnion pin on each side. This was possible
because the Buran keel was hardened against shear loads from the keel
trunnion pin. The US orbiter is not designed to take shear loads through
the keel pin, so two longeron trunnion pins are a requirement. Finally, the
airlock worked on different voltages than the US airlock and would have
been a pain to integrate. It was easier to integrate the APAS with a US
airlock and isolate the voltage changes to the ODS itself.

You will also hear another acronym, APDS (Androgynous Peripheral Docking
System), associated with the APAS. Technically:

ODS = APAS + transition + airlock + truss + APAS avionics

APDS = APAS + APAS avionics + flight deck control panels (A6L and A7L)

Or, in less technical language, ODS = "the stuff out in the payload bay"
while APDS = "the stuff we got from Russia" (which isn't completely
accurate, since only the A7L control panel was Russian; A6L was built by
Rockwell).

[1] - I consider the Buran docking mechanism an important piece of evidence
in the "Buran is a shuttle copy" vs "Buran and shuttle are examples of
convergent evolution" debate, in favor of the former. While the structural
load paths were different, the truss *would*have*fit* in the shuttle
payload bay, *down*to*the*millimeter*! While convergent evolution can
account for the airframe shape, such details prove beyond doubt that the
Russians simply copied many details when they saw no need to change them.
It is ludicrous to argue that Buran is not a shuttle copy, when it
resembles the final US shuttle design far more strongly than many of the
preliminary US designs resembled the final design.
--
JRF

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