Early concepts of Apollo had a single computer that was to be unplugged and moved between the CM and LM. This idea was soon abandoned because of contaminant buildup in the connectors:

Electrical wiring problems were experienced during the Mercury 9 flight wherein contaminants (water, urine, sweat, etc.) migrated to exposed electrical terminals in the zero-g environment. These problems led to the decision to seal all Apollo electrical wiring and connectors. However, the Block I Apollo hardware was already designed and was being built in accordance with the in-flight maintenance concept. This meant that many module-to-black-box connectors and many self-mating black-box-to-spacecraft connectors were required. The attempt to make connectors and modules humidity proof was lengthy, sometimes futile, and practically eliminated any possibility of inflight maintenance. The Block II design change involved repacking the crew compartment equipment into completely sealed units and incorporating built-in and switchable redundancy, as well as backup modes, to achieve the desired reliability and to satisfy the lunar rendezvous mission requirements.

Apollo Program Summary Report, page 4-54

How do electrical connectors on the ISS avoid humidity and contaminant problems?

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    $\begingroup$ Do not have the answers for ISS, but would assume connectors like ittcannon.com/products/ms-e-r which have a long history in aviation and marine applications and show up occasionally in shuttle era photos. $\endgroup$ Commented May 5, 2019 at 3:04
  • $\begingroup$ IFM was definitely a thing on shuttle and is on ISS as well. $\endgroup$ Commented May 5, 2019 at 4:41

1 Answer 1


I searched for "specifications for space station connectors" and found this document "Space Station Approved Electrical,Electronic, and Electromechanical Parts List."

It lists a bunch of connector specifications whose name includes "environment resisting" or "environment resistant". Here is a sample.

enter image description here

Looking up the listed specification was not too informative:

enter image description here

Since "environment resisting" seems to be a common term used when speccing these connectors, I searched for that, and found this.

Environmental sealing protects against damaging contaminants, such as water, dust, and dirt, among others. They are designed to maintain the contacts’ electrical performance. These are typically used in mobile machinery, marine and on-highway vehicles.

Environmental sealing on connectors use an interface seal to prevent contaminants from entering the intersection between the connection area. In low-temperature applications that require repeated mating and unmating, these O-ring seals are usually made from some type of rubber, with fluoropolymers and ethylene propylene rubber being the most common.

and this image.

enter image description here


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