Space environments Effect of spaceflight on the human body

1 space environments

1.1 vacuum
1.2 temperature
1.3 radiation

space environments

the environment of space lethal without appropriate protection: greatest threat in vacuum of space derives lack of oxygen , pressure, although temperature , radiation pose risks.

vacuum

this painting, experiment on bird in air pump depicts experiment performed robert boyle in 1660 test effect of vacuum on living system.

human physiology adapted living within atmosphere of earth, , amount of oxygen required in air breathe. minimum concentration, or partial pressure, of oxygen can tolerated 16 kpa (0.16 bar). below this, astronaut @ risk of becoming unconscious , dying hypoxia. in vacuum of space, gas exchange in lungs continues normal results in removal of gases, including oxygen, bloodstream. after 9 12 seconds, deoxygenated blood reaches brain, , results in loss of consciousness. death gradually follow after 2 minutes of exposure—though absolute limits uncertain.

humans , other animals exposed vacuum lose consciousness after few seconds , die of hypoxia within minutes. blood , other body fluids boil when pressure drops below 6.3 kpa (47 torr), vapor pressure of water @ body temperature. condition called ebullism. steam may bloat body twice normal size , slow circulation, tissues elastic , porous enough prevent rupture. ebullism slowed pressure containment of blood vessels, blood remains liquid. swelling , ebullism can reduced containment in flight suit. space shuttle astronauts wore fitted elastic garment called crew altitude protection suit (caps) prevented ebullism @ pressures low 2 kpa (15 torr). spacesuits necessary prevent ebullism above 19 km. spacesuits use 20 kpa (150 torr) of pure oxygen, enough sustain full consciousness. pressure high enough prevent ebullism, simple evaporation of blood, or of gases dissolved in blood, can still cause decompression sickness (the bends) , gas embolisms if not managed.

a short-term exposure vacuum of 30 seconds unlikely cause permanent physical damage. animal experiments show rapid , complete recovery normal exposures shorter 90 seconds, while longer full-body exposures fatal , resuscitation has never been successful. there limited amount of data available human accidents, consistent animal data. limbs may exposed longer if breathing not impaired. rapid decompression can more dangerous vacuum exposure itself. if victim not hold breath, venting through windpipe may slow prevent fatal rupture of delicate alveoli of lungs. eardrums , sinuses may ruptured rapid decompression, soft tissues may bruise , seep blood, , stress of shock accelerates oxygen consumption, leading hypoxia. injuries caused rapid decompression called barotrauma, , known scuba diving accidents. pressure drop small 100 torr (13 kpa), produces no symptoms if gradual, may fatal if occurs suddenly.

most of information known way human body reacts due accidental decompression, during experimental spaceflight projects. 1 such case discussed in nasa technical report: rapid (explosive) decompression emergencies in pressure-suited subjects:

@ nasa s manned spacecraft center (now renamed johnson space center) had test subject accidentally exposed near vacuum (less 1 psi) [7 kpa] in incident involving leaking space suit in vacuum chamber in 65. remained conscious 14 seconds, time takes o2 deprived blood go lungs brain. suit did not reach hard vacuum, , began repressurizing chamber within 15 seconds. subject regained consciousness @ around 15,000 feet [4600 m] equivalent altitude. subject later reported feel , hear air leaking out, , last conscious memory of water on tongue beginning boil.

there has been 1 recorded incident of death decompression in spaceflight, soyuz 11 decompression accident in 1971, resulted in death of 3 cosmonauts on board.

temperature

in vacuum, there no medium removing heat body conduction or convection. loss of heat radiation 310 k temperature of person 3 k of outer space. slow process, in clothed person, there no danger of freezing. rapid evaporative cooling of skin moisture in vacuum may create frost, particularly in mouth, not significant hazard.

exposure intense radiation of direct, unfiltered sunlight lead local heating, though distributed body s conductivity , blood circulation. other solar radiation, particularly ultraviolet rays, however, may cause severe sunburn.

radiation


comparison of radiation doses – includes amount detected on trip earth mars rad on msl (2011–2013).

without protection of earth s atmosphere , magnetosphere astronauts exposed high levels of radiation. year in low earth orbit results in dose of radiation 10 times of annual dose on earth. high levels of radiation damage lymphocytes, cells heavily involved in maintaining immune system; damage contributes lowered immunity experienced astronauts. radiation has been linked higher incidence of cataracts in astronauts. outside protection of low earth orbit, galactic cosmic rays present further challenges human spaceflight, health threat cosmic rays increases chances of cancer on decade or more of exposure. nasa-supported study reported radiation may harm brain of astronauts , accelerate onset of alzheimer s disease. solar flare events (though rare) can give fatal radiation dose in minutes. thought protective shielding , protective drugs may lower risks acceptable level.

crew living on international space station (iss) partially protected space environment earth s magnetic field, magnetosphere deflects solar wind around earth , iss. nevertheless, solar flares powerful enough warp , penetrate magnetic defences, , still hazard crew. crew of expedition 10 took shelter precaution in 2005 in more heavily shielded part of station designed purpose. however, beyond limited protection of earth s magnetosphere, interplanetary manned missions more vulnerable. lawrence townsend of university of tennessee , others have studied powerful solar flare ever recorded. radiation doses astronauts receive flare of magnitude cause acute radiation sickness , possibly death.

a video made crew of international space station showing aurora australis, caused high-energy particles in space environment.

there scientific concern extended spaceflight might slow down body s ability protect against diseases. radiation can penetrate living tissue , cause both short , long-term damage bone marrow stem cells create blood , immune systems. in particular, causes chromosomal aberrations in lymphocytes. these cells central immune system, damage weakens immune system, means in addition increased vulnerability new exposures, viruses present in body—which suppressed—become active. in space, t-cells (a form of lymphocyte) less able reproduce properly, , t-cells reproduce less able fight off infection. on time immunodeficiency results in rapid spread of infection among crew members, in confined areas of space flight systems.

on 31 may 2013, nasa scientists reported possible manned mission mars may involve great radiation risk based on amount of energetic particle radiation detected rad on mars science laboratory while traveling earth mars in 2011–2012.

in september 2017, nasa reported radiation levels on surface of planet mars temporarily doubled, , associated aurora 25-times brighter observed earlier, due massive, , unexpected, solar storm in middle of month.