Since the first two-hour excursion into space by Yuri Gagarin in 1961, the lure of manned space travel has proved irresistible to scientists, entrepreneurs, and entertainers alike. Today, as technology becomes more capable of enabling manned travel to Mars and Hollywood’s imagination runs wild with notions of humanity’s spaceflight-steeped future (with recent blockbusters like Star Trek, Prometheus, Star Wars, and even Wall-E), many fallacies about space have emerged. Outer space is often depicted in film as a cold, inhospitable place, where exposure to the perpetual vacuum will make your blood boil and your body burst; alternatively, if neither of those things happen, you’re bound to instantly freeze into a human-popsicle. Meanwhile, many of these same films conveniently ignore the slightly more subtle, yet highly relevant hazards of prolonged spaceflight even in an enclosed vessel at normal atmospheric pressure.
- If you do die in space, your body will not decompose in the normal way, since there is no oxygen. If you were near a source of heat, your body would mummify; if you were not, it would freeze.
- The only one with a rescue-ready air-locked compartment—the Space Shuttle—is in retirement. So your only choice is to orbit, waiting for your roughly 7.5 hours of breathable air to run out.
Acute exposure to the vacuum of space: No, you won’t freeze (or explode)
There is a type of amazing animal that is known to be able to survive the near vacuum of space for as many as 10 days with no ill effect, and that includes being able to handle direct exposure to solar radiation during that span. These tiny animals, growing to about 1.5 mm, are called Tardigrades (also “water bears”). “Tardigrades” means “slow walker”. The biggest totally free game fix & trainer library online for PC Games https://gamecopyworld.com. Google allows users to search the Web for images, news, products, video, and other content.
One common misconception is that outer space is cold, but in truth, space itself has no temperature. In thermodynamic terms, temperature is a function of heat energy in a given amount of matter, and space by definition has no mass. Furthermore, heat transfer cannot occur the same way in space, since two of the three methods of heat transfer (conduction and convection) cannot occur without matter.
What does this mean for a person in space without a spacesuit? Because thermal radiation (the heat of the stove that you can feel from a distance, or from the Sun’s rays) becomes the predominant process for heat transfer, one might feel slightly warm if directly exposed to the Sun’s radiation, or slightly cool if shaded from sunlight, where the person’s own body will radiate away heat. Even if you were dropped off in deep space where a thermometer might read 2.7 Kelvin (-455°F, the temperature of the “cosmic microwave background” leftover from the Big Bang that permeates the Universe), you would not instantly freeze because heat transfer cannot occur as rapidly by radiation alone.
The absence of normal atmospheric pressure (the air pressure found at Earth’s surface) is probably of greater concern than temperature to an individual exposed to the vacuum of space [1]. Upon sudden decompression in vacuum, expansion of air in a person’s lungs is likely to cause lung rupture and death unless that air is immediately exhaled. Decompression can also lead to a possibly fatal condition called ebullism, where reduced pressure of the environment lowers the boiling temperature of body fluids and initiates transition of liquid water in the bloodstream and soft tissues into water vapor [2]. At minimum, ebullism will cause tissue swelling and bruising due to the formation of water vapor under the skin; at worst, it can give rise to an embolism, or blood vessel blockage due to gas bubbles in the bloodstream.
Our dependence on a continuous supply of oxygen is the more limiting factor to the amount of time a human could survive in a full vacuum. Contrary to how the lungs are supposed to function at atmospheric pressure, oxygen diffuses out of the bloodstream when the lungs are exposed to a vacuum. This leads to a condition called hypoxia, or oxygen deprivation. Within 15 seconds, deoxygenated blood begins to be delivered to the brain, whereupon unconsciousness results [1]. Data from animal experiments and training accidents suggest that an individual could survive at least another minute in a vacuum while unconscious, but not much longer [3,4].
Long-term effects of space travel
While the effects of space suit malfunction or decompression on the human body are important to recognize, long-term consequences of spaceflight are perhaps more relevant (Figure 1). Many of the immediate physiological impacts of spaceflight are attributed to microgravity, a term that refers to very small gravitational forces. Because life on Earth has evolved to function best under Earth’s gravity, arguably all human organ systems are affected by gravity’s absence. The body is highly adaptive and can acclimatize to a change in gravitational environment, but these physiological adaptations may have pathological consequences or lead to a reduction in fitness that challenges a space-traveler’s ability to function normally upon return to Earth.
Figure 1. Physiological hazards associated with space travel. Exposure to an environment in space with microgravity and ionizing radiation can perturb the cardiovascular, excretory, immune, musculoskeletal, and nervous systems. (Illustration by Mark Springel, edited by Hannah Somhegyi)
On Earth, the cardiovascular system works against gravity to prevent blood from pooling in the legs, thus microgravity results in a dramatic redistribution of fluids from the legs to the upper body within only a few moments of weightlessness [5]. This phenomenon is colloquially known to astronauts as “puffy face” or “bird legs”, referencing the prominent facial swelling and 10-30% decrease in leg circumference. Although fluids return to a somewhat normal distribution within 12 hours, astronauts often complain of nasal stuffiness and eye abnormalities after extended stays in space [6], which are likely symptoms of the increased intracranial pressure, or pressure within the skull. Furthermore, there is a reduction of blood volume, red blood cell quantity, and cardiac output due to lower demands on the cardiovascular system to counteract gravity. This acclimation is physiologically normal and presents no functional limitations in space, but upon return to Earth’s gravity, one of every four astronauts are unable to stand for 10 minutes without experiencing heart palpitations or fainting [5,7].
Because more than half of the muscles of the human body resist gravitational force on Earth, musculoskeletal acclimation to microgravity results in profound muscle atrophy, reaching up to 50% muscle mass loss in some astronauts over the course of long-term missions [5]. The muscular atrophy seen in astronauts closely mirrors that of bedridden patients, and upon return to Earth, some astronauts experience difficulty simply maintaining an upright posture. Diminished burden in space on load-bearing bones, such as the femur, tibia, pelvic girdle, and spine, also causes demineralization of the skeleton and decreased bone density, or osteopenia. Calcium and other bone-incorporated minerals are excreted through urine at elevated levels, thus the microgravity environment puts individuals at risk not only for bone fracture, but for kidney stones as well [8].
The vestibular and sensorimotor systems, our bodies’ sensory networks that contribute to sense of balance and motor coordination, respectively, are also impacted by microgravity. The majority of astronauts experience some level of space motion sickness or disorientation for the first few days in space, and these symptoms generally subside as the body acclimates [5]; however, some astronauts still feel wobbly months after returning to Earth [9]. Furthermore, normal sleep cycles appear to be affected, as astronauts consistently sleep less and experience a more shallow and disturbed sleep in space than on Earth [10]. This may be due to a combination of microgravity or an altered light-dark cycle in space. Many astronauts complain of bright flashes that streak across their vision while trying to sleep, attributed to high-energy cosmic radiation [11].
The Earth’s atmosphere acts as a shield to block many harmful types of space radiation, but humans are dangerously exposed to this radiation in outer space (Figure 2). Ultraviolet (UV) radiation from the sun is largely absorbed by the Earth’s atmosphere and never reaches its surface, but a human unprotected in space would suffer sunburn from UV radiation within seconds. UV rays can be blocked with specially designed fabric in spacesuits and shielding on spacecraft, but higher energy ionizing radiation and cosmic rays—high-energy protons and heavy atomic nuclei from outside our Solar System—can penetrate shielding and astronauts’ bodies alike, potentially having severe health implications [6]. Damaging radiation of this type can cause radiation sickness, mutate DNA, damage brain cells, and contribute to cancer [12]. Several studies also suggest that cosmic radiation increases risk of early-onset cataracts [13], and contributes to astronauts’ increased likelihood of acquiring viral and bacterial infections due to immune system suppression [5].
What does this mean for future space missions?
The prospect of interplanetary missions compounds known health concerns regarding space travel. With our current technology, a manned mission to Mars would take more than two years, and by conservative estimates, simply getting to Mars might take 6 to 8 months. Radiation measurements recorded by NASA’s Curiosity rover during its transit to Mars suggest that with today’s technology, astronauts would be exposed to a minimum of 660 ± 120 millisieverts (a measure of radiation dosage) over the course of a round trip [14]. Because NASA’s career exposure limit for astronauts is only slightly greater at 1000 millisieverts, this recent data is cause for great concern.
Figure 2. Approximate radiation dose in several scenarios on Earth and in space. The radiation exposure associated with a round trip to Mars is extrapolated from recent data from the Mars Space Laboratory (MSL) / Curiosity rover. DOE, Department of Energy; ISS, International Space Station [14]. (Image adapted from NASA/JPL Photojournal: PIA02570 & PIA02004; http://photojournal.jpl.nasa.gov)
The recent radiation data aside, the longest consecutive stay by a human in space is only 438 days [15], and it’s not completely understood how the human body might respond to a trip to Mars and back. The effects of long-term spaceflight may be very nuanced, and this calls for new disciplines that can address the issue of adapting humans to conditions that we were not intended to endure. Frequent exercise, proper nutrition, and pharmacological therapy are three strategies used to combat the deconditioning process, yet some reduction in fitness is inevitable.
One of the fundamental challenges facing scientists who design future space missions is to develop new technologies that can accommodate the physiological limitations of humans traveling in space for indefinite periods of time. Much emphasis on research today is to develop technologies to get to Mars faster, generate artificial gravity, and reduce radiation exposure. While pop culture’s depiction of space travel may largely be fictitious, it may be science fiction that one day enables humans to venture deeper into “the final frontier.”
Mark Springel is a research assistant in the Department of Pathology at Boston Children’s Hospital.
References:
[1] Kanas N, Mansey D. “Basic Issues of Human Adaptation to Space Flight.” Space Psychology and Psychiatry, Dordrecht,: Springer Netherlands, 2008. 15-30. Print.
[2] Czarnik, TR. Ebullism at 1 Million Feet: Surviving Rapid/Explosive Decompression. http://www.sff.net/people/Geoffrey.Landis/ebullism.html”
[3] Shayler DJ. Disasters and Accidents in Manned Spaceflight, Springer-Praxis Books in Astronomy and Space Science: Chichester UK, 2000.
[4] Roth EM (1968). Rapid (Explosive) Decompression Emergencies in Pressure-Suited Subjects. NASA CR-1223.NASA Contract Rep NASA CR., Nov: 1-125.
[5] Williams D, Kuipers A, Mukai C, Thirsk R (2009). Acclimation during space flight: effects on human physiology. CMAJ 180(11): 1317-1323.
[6] Setlow RB (2003). The hazards of space travel. Embo Rep, 4(11): 1013-1016.
[7] Mader TH, Gibson CR, Pass AF, Kraimer LA, et al. (2011). Optic disc edema, globe flattening, choroidal folds, and hyperopic shifts observed in astronauts after long-duration space flight. Ophthalmology 118(10): 2058-2069.
[8] Pietrzyk RA, Jones JA, Sams CF, Whitson PA (2007). Renal stone formation among astronauts. Aviat Space Environ Med 78(4 Suppl): A9-13.
[9] Astronaut Says He’s Still Wobbly After Months of Weightlessness. New York Times, February 2, 1998. http://www.nytimes.com/1998/02/02/us/astronaut-says-he-s-still-wobbly-after-months-of-weightlessness.html”
[10] Wide awake in outer space (NASA): http://science.nasa.gov/science-news/science-at-nasa/2001/ast04sep_1/
[11] Narici L, Bidoli V, Casolino M, De Pascale MP, et al. (2004). The ALTEA/ALTEINO projects: studying functional effects of microgravity and cosmic radiation. Adv Space Res 33(8): 1352-7.
[12] Townsend LW (2005). Implications of the space radiation environment for human exploration in deep space. Radiat Prot Dosimetry 115(1-4): 44-50.
[13] Chylack LT, Peterson LE, Feiveson AH, Wear ML, et al. (2009). NASA study of cataract in astronauts (NASCA). Report 1: Cross-sectional study of the relationship of exposure to space radiation and risk of lens opacity. Radiat Res 172(1): 10-20.
[14] Zeitlin C, Hassler DM, Cucinotta FA, Ehresmann B (2013). Measurements of energetic particle radiation in transit to Mars on the Mars Science Laboratory. Science 340(6136): 1080-1084.
[15] Staying Put on Earth, Taking a Step to Mars by Michael Schwirtz. New York Times. March 30, 2009. http://www.nytimes.com/2009/03/31/science/space/31mars.html
Additional Resources:
Race to Mars: Known effects of long-term space flights on the human body (Discovery Channel): http://www.racetomars.ca/mars/article_effects.jsp
Kerr RA (2013). Radiation will make astronaut’s trip to Mars even riskier. Science 340(6136): 1031
Spaceflight bad for astronauts’ vision, study suggests (Space.com): http://www.space.com/14876-astronaut-spaceflight-vision-problems.html
Study shows that space travel is harmful to the brain and could accelerate onset of Alzheimer’s (SpaceRef): http://spaceref.com/news/viewpr.html?pid=39650
Cherry JD, Liu B, Frost FL, Lemere CA, et al. (2012). Galactic cosmic radiation leads to cognitive impairment and increased Aβ plague accumulation in a mouse model of Alzheimer’s disease. PLoS One 7(12): e53275
Buckey JC. Space Physiology, New York: Oxford University Press, 2006. Print.
Clément G. Fundamentals of Space Medicine, Microcosm Press, Dordrecht ; Boston: Kluwer Academic, 2003. Print.
Meet Nidhi Mayurika, a class IX student studying at Narayana Olympiad School in Bengaluru who, with her incredible innovations like a three-layered space colony and a satellite to launch another satellite, has been winning the NASA Ames Space Settlement Contest for three years now. She is full of energy and the sky is the limit for her imagination and calculations. While many of us have to open the dictionary to search for the meaning of space-related terminology, she has all of them on the tip of her tongue. After so much of groundwork about space and its elements, she aims to become a cosmologist and represent India on an international platform.
How Long Survive In Space
When Nidhi was 11, she felt that the creation of the universe was a strange phenomenon and this curiosity led her to find out and learn more about it. She says, 'When I was in class V, I’d always take part in the science competitions held at the school level. Considering my interest, my school principal told me about the NASA Ames Space Settlement Contest. I had two reasons for participating in this contest. Firstly, this was a platform for me to express myself, my ideas about space and its elements. The other reason is that I wanted to represent my country. After all, we Indians have been able to prove many theories with the power of imagination alone like the Theory of Parmanu(atom), solar systems and many more.'
My parents and elder brother played a major role in my success. We have had discussions every day on the information to be added to my project. While my mother named all the three projects, my father edited and animated the space colony models for all the three years. I was also guided by N Chandrashekar Rao who is our physics HOD
Nidhi Mayurika
Survive In Space Cracked
In 2016, when the organisers of the NASA contest announced that the students must design something on the lines of the virtual space colonies in which settlers can live inside a gigantic spacecraft, Nidhi spent more than two hours a day, after school, working on a project called Saikatam — which translates to a new home away from home. 'Saikatam is a three-layered space colony for human settlement at Earth-Moon Lagrange Point 5 situated at 3,85,000 km. It is a space colony for humans to survive, evolve and self-sustain. The space colony is akin to Earth with life gases, artificial gravity, water, and food,' she explains.
Needless to say, Nidhi’s efforts and the time she spent paid off. She won the first prize for Saikatam. In the 2017 NASA contest, she participated again and her project bagged the first prize again. This time it was for the project Soham, which is used to launch satellites. She says, 'Soham is a habitable space colony located 350 km away from Earth at LEO, to build and launch satellites, comprising of an Inflatable Space Station.'
How Long Can You Survive In Space
SPACE VIEW: Nidhi Mayurika has won the NASA Ames Space Settlement Contest thrice for her innovative projects on space
Nidhi’s third project, which she presented this year, was Swastikam — a place for creation. 'Swastikam is a space colony built for synthetically designed and created organisms to adapt, evolve and be independent in the new ecosystem. This helps organisms adapt to change in conditions such as radiation, heat, continuous daylight and lack of gravity,' she explains patiently.
It is not just the books and the hours Nidhi spent after school that has helped her come this far at such a young age. She has taken up online programmes relating to the universe from The University of Edinburgh, the Australian National University, Boston University and many more. She says, 'The lectures gave me a lot of information, helped me with innovative ideas about space colonies and also gave me problem statements to do the project every year.'
With Nidhi's innovations, it feels like India will have its youngest cosmologist by 2020 and who knows, we might even create an artificial place to live in space — designed by a girl from namma Bengaluru!