An orbital replacement unit or orbital replaceable unit is a modular component of spacecraft that can be replaced upon failure either by robot or by extravehicular activity. The Hubble Space Telescope (HST) was designed with 70 such parts,[1] including scientific instruments and limited-life items such as batteries.[1]

On HST some parts were designed from the start as ORUs and all used captive bolts with a standard 7/16" double-height hex head;[2] later when it was decided to avoid returning HST to Earth for repair, more systems and modules were designated as ORUs (but used a wider variety of fasteners).[2] HST servicing mission 3A (SM3A) replaced (or added) 15 ORUs,[2]: fig 2-1  e.g. it replaced the DF-224 computer with the Advanced Computer.

The electrical system of the International Space Station also has such subsystems that provide power generation, power distribution and energy storage.[3]

See also

References

  1. 1 2 Kinard, William H. "Returned Hardware: Orbital Replacement Units". Hubble Space Telescope Archive System. NASA / Langley Research Center. Archived from the original on 19 February 2013. Retrieved 27 March 2013.
  2. 1 2 3 "Hubble Space Telescope Servicing Mission 3A Media Reference Guide" (PDF). NASA. Lockheed Martin Missiles and Space. Retrieved 21 September 2010. Section 2.2.
  3. ↑ "Glenn Leads Sustaining Engineering of Power System Hardware". NASA / Glenn Research Center. 14 February 2008. Archived from the original on 22 February 2012. Retrieved 27 March 2013.


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