Passivation (spacecraft)

The passivation of a spacecraft is the removal of any internal energy contained in the vehicle at the end of its mission or useful life.[1] Spent upper stages are generally passivated after their use as launch vehicles is complete, as are satellites when they can no longer be utilized for their initial design purpose.

Overview

For satellites in geosynchronous orbit, both the International Telecommunications Union (ITU) and United Nations (UN) recommends that GEO-satellites be designed such that they can, at end of life, remove themselves to a disposal orbit some 350 kilometres (220 mi) above the GEO belt, and then passivate themselves by removing any internally stored energy. "There is no [international] enforcement of these recommendations" but the majority of these GEO spacecraft are being boosted up into the recommended graveyard orbits.[1]

The largest component of internally stored energy is generally unused propellant,[1] although batteries are also important sources of stored energy that also require passivation.[2]

Empirical history has shown that stored energy that is not dissipated can often become an energy source for initiating an explosion or fragmentation, resulting in unwanted manmade space debris.[1][2]

Standard practices

Within national regimes, where national governments can control the launch licenses of launch vehicles and spacecraft, there are some enforceable requirements for passivation.

The US government has implemented a set of standard practices for both civilian (NASA) and military (DoD/USAF) orbital debris mitigation that require passivation. "All on-board sources of stored energy of a spacecraft or upper stage should be depleted or safed when they are no longer required for mission operations or postmission disposal. Depletion should occur as soon as such an operation does not pose an unacceptable risk to the payload. Propellant depletion burns and compressed gas releases should be designed to minimize the probability of subsequent accidental collision and to minimize the impact of a subsequent accidental explosion."[3][4]

See also

References

  1. 1 2 3 4 Johnson, Nicholas (2011-12-05). Livingston, David, ed. "Broadcast 1666 (Special Edition) - Topic: Space debris issues" (podcast). The Space Show. 1:03:05-1:06:20. Retrieved 2015-01-05.
  2. 1 2 Bonnal, C. (2007). "Design and operational practices for the passivation of spacecraft and launchers at the end of life". Journal of Aerospace Engineering. Retrieved 2012-12-18.
  3. ↑ "U.S. Government Orbital Debris Mitigation Standard Practices" (PDF). United States Federal Government. Retrieved 2013-11-28.
  4. ↑ "Orbital Debris – Important Reference Documents.", NASA Orbital Debris Program Office.
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