Editing Mir (section)

===Safety aspects===

====Ageing systems and atmosphere====
In the later years of the programme, particularly during the Shuttle-''Mir'' programme, ''Mir'' suffered from various systems failures. It had been designed for five years of use, but eventually flew for fifteen, and in the 1990s was showing its age, with frequent computer crashes, loss of power, uncontrolled tumbles through space and leaking pipes. [[Jerry Linenger]] in his book about his time on the facility says that the cooling system had developed tiny leaks too small and numerous to be repaired, that permitted the constant release of [[coolant]]. He says that it was especially noticeable after he had made a spacewalk and become used to the bottled air in his spacesuit. When he returned to the station and again began breathing the air inside ''Mir'', he was shocked by the intensity of the smell and worried about the possible negative health effects of breathing such contaminated air.<ref name="OffPlanet"/>{{page needed|date=February 2021}}

Various breakdowns of the Elektron oxygen-generating system were a concern; they led crews to become increasingly reliant on the backup [[Vika oxygen generator|''Vika'']] [[chemical oxygen generator|solid-fuel oxygen generator]] (SFOG) systems, which led to a fire during the handover between EO-22 and EO-23.<ref name="SSSM"/><ref name="Dragonfly"/>{{page needed|date=February 2021}} (see also [[ISS ECLSS#Vika|ISS ECLSS]])

====Accidents====
[[File:Mir after Fire.jpg|thumb|A charred panel in [[Kvant-1|''Kvant''-1]] following the ''Vika'' fire]]
Several accidents occurred which threatened the station's safety, such as the glancing collision between ''[[Kristall]]'' and [[Soyuz TM-17]] during proximity operations in January 1994. The three most alarming incidents occurred during [[Mir EO-23|EO-23]]. The first was on 23 February 1997 during the handover period from [[Mir EO-22|EO-22]] to EO-23, when a malfunction occurred in the backup [[Vika oxygen generator|''Vika'']] system, a [[chemical oxygen generator]] later known as solid-fuel oxygen generator (SFOG). The ''Vika'' malfunction led to a fire which burned for around 90 seconds (according to official sources at the TsUP; astronaut [[Jerry M. Linenger|Jerry Linenger]] insists the fire burned for around 14 minutes), and produced large amounts of toxic smoke that filled the station for around 45 minutes. This forced the crew to don respirators, but some of the respirator masks initially worn were broken. Some of the [[fire extinguisher]]s mounted on the walls of the newer modules were immovable.<ref name="Dragonfly"/>{{page needed|date=February 2021}}<ref name="OffPlanet"/>{{page needed|date=February 2021}}
[[File:Mir collision damage STS086-720-091.JPG|thumb|Picture of the damage caused by the collision with [[Progress M-34]]. Picture was taken by [[Space Shuttle Atlantis|Space Shuttle ''Atlantis'']] during [[STS 86]]]]
The other two accidents concerned testing of the station's [[TORU]] manual docking system to manually dock [[Progress M-33]] and [[Progress M-34]]. The tests were to gauge the performance of long-distance docking and the feasibility of removal of the expensive [[Kurs (docking system)|''Kurs'']] automatic docking system from Progress spacecraft. Due to malfunctioning equipment, both tests failed, with Progress M-33 narrowly missing the station and Progress M-34 striking ''[[Spektr]]'' and puncturing the module, causing the station to depressurise and leading to ''Spektr'' being permanently sealed off. This in turn led to a power crisis aboard ''Mir'' as the module's solar arrays produced a large proportion of the station's electrical supply, causing the station to power down and begin to drift, requiring weeks of work to rectify before work could continue as normal.<ref name="SSSM"/><ref name="Dragonfly"/>{{page needed|date=February 2021}}

====Radiation and orbital debris====
[[File:Space Debris Low Earth Orbit.png|thumb|right|[[Space debris]] in [[low Earth orbit]]]]
Without the protection of the Earth's atmosphere, cosmonauts were exposed to higher levels of [[radiation]] from a steady flux of [[cosmic ray]]s and trapped protons from the [[South Atlantic Anomaly]]. The station's crews were exposed to an [[absorbed dose]] of about 5.2&nbsp;[[Gray (unit)|cGy]] over the course of the [[Mir EO-18]] expedition, producing an [[equivalent dose]] of 14.75&nbsp;[[Sievert|cSv]], or 1133&nbsp;μSv per day.<ref>{{cite journal |title=Biodosimetry Results from Space Flight Mir-18 |journal=Radiation Research |year=1997 |volume=148 |issue=5 |pages=S17–S23 |doi=10.2307/3579712 |author=Yang TC |display-authors=etal |jstor=3579712|bibcode=1997RadR..148S..17Y}}</ref><ref>{{cite journal |doi=10.1016/S0273-1177(98)01070-9 |title=Radiation environment on the Mir orbital station during solar minimum |journal=[[Advances in Space Research]] |year=1998 |volume=22 |issue=4 |pages=501–510 |author=Badhwar GD |pmid=11542778 |bibcode=1998AdSpR..22..501B 
|display-authors=1 |last2=Cash |last3=Petrov |last4=Akatov |last5=Tchernykh |last6=Shurshakov |last7=Arkhangelsky}}</ref> This daily dose is approximately that received from natural [[background radiation]] on Earth in two years.<ref>{{cite report|title=Report of the United Nations Scientific Committee on the Effects of Atomic Radiation to the General Assembly|date=26 July 2000|url=http://www.unscear.org/docs/reports/gareport.pdf|access-date=6 February 2011|archive-date=5 February 2009|archive-url=https://web.archive.org/web/20090205040744/http://www.unscear.org/docs/reports/gareport.pdf|url-status=live}}</ref> The radiation environment of the station was not uniform; closer proximity to the station's hull led to an increased radiation dose, and the strength of radiation shielding varied between modules; ''Kvant''-2's being better than the core module, for instance.<ref>{{cite journal|title=Measurement of the Depth Distribution of Average LET and Absorbed Dose Inside a Water – Filled Phantom on Board Space Station MIR|journal=Physica Medica|year=2001|volume=17|issue=Supplement 1|pages=128–130|pmid=11770528|url=http://www.ati.ac.at/~vanaweb/papers/Arona.pdf|access-date=6 February 2011|author=Berger T|display-authors=etal }}</ref>

The increased radiation levels pose a higher risk of crews developing cancer, and can cause damage to the [[chromosome]]s of [[lymphocyte]]s. These cells are central to the [[immune system]] and so any damage to them could contribute to the lowered [[immunity (medical)|immunity]] experienced by cosmonauts. Over time, in theory, lowered immunity results in the spread of infection between crew members, especially in such confined areas. To avoid this only healthy people were permitted aboard. Radiation has also been linked to a higher incidence of [[cataract]]s in cosmonauts. Protective shielding and protective drugs may lower the risks to an acceptable level, but data is scarce and longer-term exposure will result in greater risks.<ref name="JCB"/>{{page needed|date=February 2021}}

At the low altitudes at which ''Mir'' orbited there is a variety of [[space debris]], consisting of everything from entire spent [[rocket stage]]s and defunct [[satellite]]s, to explosion fragments, paint flakes, slag from solid rocket motors,<ref>{{Cite web|title=Space Debris Basics {{!}} The Aerospace Corporation|url=http://www.aerospace.org/cords/space-debris-basics/|website=aerospace.org|access-date=28 November 2015|archive-url=https://web.archive.org/web/20151208141911/http://www.aerospace.org/cords/space-debris-basics/|archive-date=8 December 2015|url-status=dead}}</ref> coolant released by [[RORSAT]] nuclear powered satellites,<ref>{{Cite book|title=Space Debris: Models and Risk Analysis|url=https://archive.org/details/spacedebrismodel00klin_663|url-access=limited|last=Klinkrad|first=Heiner|publisher=Praxis Publishing Ltd.|year=2006|isbn=978-3540376743|page=[https://archive.org/details/spacedebrismodel00klin_663/page/n91 83]|bibcode=2006sdmr.book.....K}}</ref> [[Project West Ford|small needles]], and many other objects. These objects, in addition to natural [[micrometeoroid]]s,<ref>{{cite journal|author=F. L. Whipple|year=1949|title=The Theory of Micrometeoroids|journal=Popular Astronomy|volume=57|page=517|bibcode=1949PA.....57..517W}}</ref> posed a threat to the station as they could puncture pressurised modules and cause damage to other parts of the station, such as the solar arrays.<ref>{{cite web|author=Henry Nahra|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890016664_1989016664.pdf|title=Effect of Micrometeoroid and Space Debris Impacts on the Space Station Freedom Solar Array Surfaces|date=24–29 April 1989|publisher=NASA|access-date=7 October 2009|archive-date=6 June 2011|archive-url=https://web.archive.org/web/20110606043107/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890016664_1989016664.pdf|url-status=live}}</ref> Micrometeoroids also posed a risk to [[Extra-vehicular activity|spacewalking]] cosmonauts, as such objects could [[Space exposure|puncture their spacesuits]], causing them to depressurise.<ref>{{cite news|url=http://www.space.com/missionlaunches/junk_iss_020107.html|title=Space Junk and ISS: A Threatening Problem|access-date=13 July 2011|work=Space.com|date=7 January 2002|author=Leonard David|archive-url=https://web.archive.org/web/20090523163656/http://www.space.com/missionlaunches/junk_iss_020107.html|archive-date=23 May 2009}}</ref> Meteor showers in particular posed a risk, and, during such storms, the crews slept in their Soyuz ferries to facilitate an emergency evacuation should ''Mir'' be damaged.<ref name="SSSM"/>
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