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Space Shuttle Orbiter Hydraulic System

Sat Sep 10, 2011 4:58 am

So I was wondering if there are any space shuttle buffs who might be able to answer a quick question; I've been looking at this description of some of the shuttle systems here, with specific interest in the hydraulic system-,2,3_Switches_on_Panel_R2

The shuttle is interesting in particular because it is unique is its use of a hydrazine powered APU to pressurize the hydraulics, but I was mainly wondering if anybody could tell me what type of hydraulic fluid it used? Was a special fluid developed specifically for the shuttle? Reason is, I would presume that it might just use ordinary Mil-spec red oils like MIL-H-5606, 83282.

Because of the extreme temperatures experienced by the shuttle though, given the extended cold-soak in orbit, and then extreme heating on re-entry, I think that the Shuttle engineers must have used something higher-performance than a bog-standard Mil-spec red oil fluid - and I'm very doubtful that it used skydrol, which isn't much better! (Blergh)

Red oil fluids have very poor viscosity at extreme low temps, and are flammable at extreme high temps, so did the Shuttle have it's own special fluid? Maybe a silicate ester like Concorde, or maybe even ethylene glycol?
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RE: Space Shuttle Orbiter Hydraulic System

Sat Sep 10, 2011 8:02 am

looks like it's a bit special:
MIL-H-83282 spec according to
and if you believe these guys - - looks like you can buy a bit of same fluid to use in your car, it's not that expensive..
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RE: Space Shuttle Orbiter Hydraulic System

Mon Sep 12, 2011 2:24 am

Thanks for that link kalvado - I did wonder if it was 83282 spec fluid - that's one of the higher temperature rated red oils, so it makes sense, I just wondered if there was a special 'space shuttle fluid' used, but that's a regular aircraft grade fluid.
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