Editing Human spaceflight (section)

===== Radiation =====
{{See also|Health threat from cosmic rays}}
[[File:PIA17601-Comparisons-RadiationExposure-MarsTrip-20131209.png|thumb|right|Comparison of Radiation Doses – includes the amount detected on the trip from Earth to Mars by the [[Radiation assessment detector|RAD]] on the [[Mars Science Laboratory|MSL]] (2011–2013)<ref name="SCI-20130531a">{{cite journal |last=Kerr |first=Richard |title=Radiation Will Make Astronauts' Trip to Mars Even Riskier |date=31 May 2013 |journal=[[Science (journal)|Science]] |volume=340 |issue=6136 |page=1031 |doi=10.1126/science.340.6136.1031 |pmid=23723213 |bibcode=2013Sci...340.1031K}}</ref>]]

Without proper shielding, the crews of missions beyond low Earth orbit might be at risk from high-energy protons emitted by [[solar particle event]]s (SPEs) associated with [[solar flare]]s. If estimated correctly, the amount of radiation that astronauts would be exposed to from a solar storm similar to that of the most powerful in recorded history, the [[Carrington Event]], would result in [[acute radiation sickness]] at least, and could even be fatal "in a poorly shielded spacecraft".<ref>{{cite web |url=https://www.newscientist.com/article/dn7142 |title= Superflares could kill unprotected astronauts|work=New Scientist |date=21 March 2005 |first=Stephen |last=Battersby}}</ref>{{better source needed|reason=Citation does not differentiate between solar flares and solar particle events.|date=December 2021}} Another storm that could have inflicted a potentially lethal dose of radiation on astronauts outside Earth's protective [[magnetosphere]] occurred during the [[Space Age]], shortly after [[Apollo 16]] landed and before [[Apollo 17]] launched.<ref>{{cite journal |author1 = Mike Lockwood |author2 = M. Hapgood |title = The Rough Guide to the Moon and Mars |journal = Astron. Geophys. |volume = 48 |issue = 6 |pages = 11–17 |date = 2007 |doi = 10.1111/j.1468-4004.2007.48611.x |bibcode = 2007A&G....48f..11L |doi-access = free }}</ref> This solar storm, [[August 1972 solar storm|which occurred in August 1972]], could potentially have caused any astronauts who were exposed to it to suffer from acute radiation sickness, and may even have been lethal for those engaged in [[extravehicular activity]] or on the lunar surface.<ref>{{cite journal |author1 = Jennifer L. Parsons |author2 = L. W. Townsend |title = Interplanetary Crew Dose Rates for the August 1972 Solar Particle Event |journal = Radiat. Res. |volume = 153 |issue = 6 |pages = 729–733 |date = 2000 |doi = 10.1667/0033-7587(2000)153[0729:ICDRFT]2.0.CO;2 |pmid = 10825747 |bibcode = 2000RadR..153..729P |s2cid = 25250687 }}</ref>

Another type of radiation, galactic [[cosmic ray]]s, presents further challenges to human spaceflight beyond low Earth orbit.<ref>{{cite book|isbn=978-0-309-10264-3|url=http://www.nap.edu/catalog.php?record_id=11760 |title=Space Radiation Hazards and the Vision for Space Exploration |publisher=NAP |date=2006| doi=10.17226/11760 }}</ref>

There is also some scientific concern that extended spaceflight might slow down the body's ability to protect itself against diseases,<ref>{{cite journal|doi=10.1189/jlb.0309167 |title=Could spaceflight-associated immune system weakening preclude the expansion of human presence beyond Earth's orbit|date=2009|last1=Gueguinou|first1=N.|last2=Huin-Schohn|first2=C.|last3=Bascove|first3=M.|last4=Bueb|first4=J.-L.|last5=Tschirhart|first5=E.|last6=Legrand-Frossi|first6=C.|last7=Frippiat|first7=J.-P.|journal=Journal of Leukocyte Biology|volume=86|issue=5|pages=1027–1038|pmid=19690292|doi-access=}}</ref> resulting in a weakened [[immune system]] and the activation of dormant [[virus]]es in the body. [[Radiation]] can cause both short- and long-term consequences to the bone marrow stem cells from which blood and immune-system cells are created. Because the interior of a spacecraft is so small, a weakened immune system and more active viruses in the body can lead to a fast spread of infection.<ref>{{cite web |last1=Sohn |first1=Rebecca |title=How do viruses affect astronauts in space? |url=https://www.space.com/viruses-in-space-astronaut-health-impacts |website=Space.com |date=7 March 2022 |publisher=Future US |access-date=20 October 2022}}</ref>