The passivation of a

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...

is the removal of any internal energy contained in the vehicle at the end of its mission or useful life. Spent

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...

s are generally passivated after their use as launch vehicles is complete, as are

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotop ...

s when they can no longer be used for their design purpose. Internally stored energy generally takes the form of unused

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

and batteries. In the past, such stored energy has sometimes led to fragmentation or

explosion An explosion is a rapid expansion in volume associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Supersonic explosions created by high explosives are known ...

, producing unwanted

space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...

. This was a fairly common outcome for many of the U.S. and Soviet rocket designs of the 1960s to the 1980s.A. Rossi et al
"Effects of the RORSAT NaK Drops on the Long Term Evolution of the Space Debris Population"
University of Pisa, 1997. It remains an occasional problem with derelict second stages left in higher Earth orbits; several U.S. rocket stages fragmented in 2018 and 2019. The

International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Union ...

(ITU) and

United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizi ...

(UN) recommend that satellites in

geosynchronous orbit A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...

be designed to move themselves to a disposal orbit some above the GEO belt, and then remove internally stored energy. Most GEO satellites conform to these recommendations, although there are no enforcement mechanisms.

Standard practices

Within national regimes, where national governments can control the

launch license The Office of Commercial Space Transportation (generally referred to as FAA/AST or simply AST) is the branch of the United States Federal Aviation Administration (FAA) that approves any commercial rocket launch operations — that is, any laun ...

s of launch vehicles and spacecraft, there are some enforceable requirements for passivation. The

U.S. government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a feder ...

has a set of standard practices for civilian ( NASA) and military ( DoD/ USSF) orbital debris mitigation that require passivation for space launches with U.S. launch licenses. "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 Payload is the object or the entity which is being carried by an aircraft or launch vehicle. Sometimes payload also refers to the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight. Depending on the nature of ...

. 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." Passivation practice on many launches in recent decades has not mitigated second-stage breakups. Upper stage deflagration/breakup events have continued even with newer rocket designs of the 2010s, long after the

negative externality In economics, an externality or external cost is an indirect cost or benefit to an uninvolved third party that arises as an effect of another party's (or parties') activity. Externalities can be considered as unpriced goods involved in either c ...

of space debris became widely considered as a much larger social problem. For example, there were three upper-stage breakups in just the late 2010s: * 30 August 2018: Atlas V Centaur passivated second stage launched on 17 September 2014 broke up, creating

. * 23–25 March 2018: Atlas V Centaur passivated second stage launched on 8 September 2009 broke up. * 6 April 2019: Atlas V Centaur passivated second stage launched on 17 October 2018 broke up.

References

{{Reflist Spaceflight concepts Spacecraft endings