The absence of natural light in spacecraft may have significant effects on humans, too. Gravitropism is the way plants grow in response to the pull of gravity. When placed near a window, plants exhibit phototropism bending toward the light source. This behavior can be easily observed by placing a plant on its side; within minutes the roots and stem begin to reorient themselves in response to both gravity and light.
Credit NASA If the only effect of light on humans was to generate subjective brightness, then this artificial light spectrum might be adequate. It has become clear, however, that light has numerous additional physiological and behavioral effects. For example, light exerts direct effects on chemicals near the surface of the body, photoactivating vitamin D precursors and destroying circulating photoabsorbent compounds melanin. It also exerts indirect effects via the eye and brain on neuroendocrine functions, circadian rhythms, secretion from the pineal organ, and, most clearly, on mood.
Many people exhibit major swings in mood seasonally, in particular toward depression in the fall and winter when the hours of daylight are the shortest. While not yet proved, it seems highly likely that prolonged exposure to inadequate lighting that is, the wrong spectrum, or too low an intensity, or too few hours per day of light may adversely affect mood and performance.
The effects of spaceflight on biological specimens might also be related to other factors. Even the gentlest of launch vehicles produces 8 Fundamentals of the Space Medicine enormous amounts of noise and vibration, plus elevated g forces, until orbital velocity is achieved, or during the reentry into Earth atmosphere. Once in orbit, machines and astronauts continue to produce vibrations that are difficult to control. The space environment also exposes animals and individuals to high-energy radiation unlike anything they experience on Earth see Chapter 2, Section 5.
Some scientists fear that sending humans to the Moon and Mars might preclude the pursuit of high quality science. On the other hand, some proponents of human exploration are concerned that doing as much science as possible using robots would diminish interest in sending humans.
Nevertheless, humans will always be in command. The question is where would they most effectively stand? Space exploration should be thought of as a partnership to which robots and humans each contribute important capabilities. Opposing robotics versus human crews is like comparing apples and oranges. The discussion must be framed in terms of relative strengths of humans and robots in exploring the Moon and Mars. For example, robots are particularly good at repetitive tasks.
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In general, robots excel in gathering large amounts of data and doing simple analyses. Hence, they can be designed for reconnaissance, which involves highly repetitive actions and simple analysis. Although they are difficult to reconfigure for new tasks, robots are also highly predictable and can be directed to test hypotheses suggested by the data they gather. However, robots are subject to mechanical failure, design and manufacturing errors, and errors by human operators. Also, before robots can explore and find evidence of life on Mars, their functional capabilities, particularly their mobility, need to be radically improved and enhanced.
In addition, the delay in communication between Mars and Earth in the order of 40 minutes round trip poses a serious problem for tele-operation maneuvers. People, on the other hand, are capable of integrating and analyzing diverse sensory inputs and of seeing connections generally beyond the ability of robots. Humans can respond to new situations and adapt their strategies accordingly. In addition, they are intelligent operators and efficient endeffectors. They may easily do better than automated systems in any number of Introduction to Space Life Sciences 9 situations, either by deriving a creative solution from a good first hand look at a problem or by delivering a more brainless kick in the right place to free a stuck antenna.
Finally, only humans are adept at field science, which demands all of these properties. Obviously, humans would have a clear role in doing geological field work and in searching for life on Mars. On the other hand, humans are also less predictable than robots and subject to illness, homesickness, stress from confinement, hunger, thirst, and other human qualities. They need protective space suits and pressurized habitats. Hence, they require far greater and more complicated and expensive support than robots. A direct comparison is unjust, however. Automatic probes have indeed returned spectacular results, but it is wrong to compare these directly with human flights.
Historically, space life sciences are a rather recent discipline. For instance, large clinical trials are needed to determine the efficacy of a new drug. Before the relief, the tension was very high in Mission Control, especially when looking at the signals of the accelerometers mounted on the antenna! But with all this, it is likely that the life sciences data obtained in low Earth orbit studies will be practically utilized for going further such as establishing a Mars base or for improving our knowledge of clinical and aging disorders on Earth, long before information on the magnetic field of Neptune Barratt It is true that the cost of human-based space infrastructures, such as the International Space Station ISS , is much higher than unmanned missions.
However, the primary purpose for the ISS was a political one. The ISS is a major accomplishment for all countries involved even in its current incomplete state. It is the largest on-orbit structure ever built and the largest multi-national cooperative project in history. In building the ISS infrastructure and research equipment, aerospace companies are acquiring unique capabilities that make them recognized world players in areas such as space structures, automation, robotics, avionics, fluid handling, advanced life support systems and medical equipment.
Both in view of the need to develop advanced technologies and by virtue of the research carried out on board, the ISS can have a significant impact on the competitiveness of aerospace industry. In the same way that one would not charge the cost of a road-system to a single car or even the first dozen cars , the cost of the ISS cannot be endorsed by the scientific return of its first experiments. The opportunities for in-depth studies in space life sciences have indeed been sparse.
This is simply the nature of the current space program, with much to do and a few flight opportunities that must be shared. Experiments that might take weeks on Earth take years to plan and execute in space. Limitations of the spaceflight environment also have limited control experiments and often kept the number of specimens studied far from statistically ideal. Often space studies are paralleled by Earth-based simulation studies using centrifuges or clinostats, but results in actual microgravity are somewhat different.
Another argument often proposed against space life sciences is that no Nobel prizes have been given in this field of research. Although a true statement, there are several instances, however, of Nobel Prizes formerly delivered in life sciences related fields which would presumably not have been presented based on the recent results obtained in space. During this test, irrigation of the external auditory ear with water or air above or below body temperature generates rhythmic eye movements nystagmus and the subject experiences slight vertigo.
A space experiment carried out on board Spacelab in proved this Introduction to Space Life Sciences 11 theory to be wrong since caloric nystagmus was also observed in microgravity, where no heat current convection is generated. Later studies revealed that it is more likely the changes in pressure or temperature that are at the origin of the eye movement response Scherer et al.
Frequency of manned spaceflight as a function of flight duration from to Most flights were of short duration, with a mean value of 28 days. The median value, however, is in the order of 10 days. Adapted from Reschke and Sawin 1. As I write these lines, the total number of days spent in space is about 26, crew days. This number might sound large, but it corresponds to only about 71 years, that is less than a lifetime for a single individual. Actually, these 71 years are the cumulative time spent by all astronauts and cosmonauts who have flown in space to date. If we include the re-flights, the number of flown individuals goes up to However, most of these individuals have spent less than 30 days in space, even by cumulating 3 or 4 flights.
The mean duration of all spaceflights to date is about 28 days, but the median time in orbit is close to 10 days Figure Flight duration longer than 6 months is limited to about 40 individuals, and only four individuals have experienced spaceflights longer than one year Figure Had all the astronauts and cosmonauts been the subjects of space life sciences investigations during their spaceflight, the total amount of collected data would be limited to a very small period of a human lifetime 71 years. Yet, since life sciences investigations were not conducted on all astronauts 12 Fundamentals of the Space Medicine and cosmonauts, and since most of them have flown more than once, the limited number of individuals and observations makes the significance of this data very low.
This simple arithmetic is to illustrate how little research time—on how few space flyers—is currently available to determine the effects of spaceflight on the human body. A comparison between space research and extreme environment research would undoubtedly show that much more has been accomplished on Mt. Everest or during polar expeditions during the same period. Cumulative histogram showing the astronauts and cosmonauts count as a function of flight duration.
Therefore, no data is gained anymore during very long more than 6 months spaceflights. The record of spaceflight duration is currently held by Dr. Valery Polyakov, a Russian physician, who spent days during a single mission on board the space station Mir in see Figure This was his second spaceflight, though. In , he had already spent days on board Mir, so his total time spent in space actually is days, or about 22 months.
But this is not the longest duration in space for a single individual. Sergey Avdeyev has logged days during 3 stays on board Mir in days , days and days and he currently holds the all-time cumulative total for days in space. About expeditioners have explored successfully the Arctic or Antarctic with or without outside assistance between and Source: www. Introduction to Space Life Sciences 13 to microgravity that will be experienced during a mission to Mars. However, although we know that humans can survive to long duration in space, the data collected on two individuals is extremely limited.
There is a general perception that since a small number of cosmonauts have survived in low Earth orbit for as long as a year or so, there are no major physiological problems likely to preclude longer-term human planetaryexploration missions. One must admit that, over the years, there has been only access to anecdotal data from the Russian space program. This anecdotal information is, while interesting, not sufficiently reliable for drawing conclusions for a number of reasons.
There are differences in the scientific method, the experimental protocols and the equipment, and the results are not published in peer-reviewed international scientific journals. Fortunately, the increased recent cooperative activities between Russia and its partners of the International Space Station allow a standardization of experimental procedures and better data exchange. Historically, Icarus was the first victim of a flying adventure, when he and his father Daedalus tried to escape their prison on the island of Crete by flying using waxed feathers.
The legend says that Icarus, ignoring both advice and warning, flew too close to the Sun. The heat softened the wax and the feathers detached, precipitating Icarus in a dreadful fall. However, there were no witnesses of Icarus and Daedalus flight. This was not the case for the second human flight in the history though.
In June , two brothers, Jacques Etienne and Joseph Michel Montgolfier, sent a large, smoked-filled bag 35 feet into the air. This first balloon flight was recorded by the French Academy of Sciences. Three months later, a duck, a rooster, and a sheep became the first passengers in a balloon, since no one knew whether a human could survive the flight.
All three animals survived the flight, although the duck was found with a broken leg, presumably due to a kick from the sheep after landing. Finally on November 21, , a human flight was attempted before a vast crowd that included the King and Queen of 14 Fundamentals of the Space Medicine France, and recognized scientists Tillet et al.
After this event, ballooning became quite popular for over half a century in Europe. Ten days after the first manned hot air flight, a French physicist named J. Charles made the first human flight in a hydrogenfilled balloon. When he reached an altitude of m, he began to experience physiologically some of the realities of this new environment. He complained of the penetrating cold at this altitude and a sharp pressure pain in one ear as he descended. This is the first description of symptoms experienced in aerospace medicine.
In in England, after several animals were used in free flight tests, Mrs. Tible became the first woman to fly a balloon, and JeanPierre Blanchard became the first to cross the Channel from England to France. Feeling outdone, Pilatre de Roziers built a new balloon, using a combination of hot air envelope and a small hydrogen balloon, to fly from France to England. Ironically, the first to fly in a balloon became the first balloon casualty. The hazards of high altitude flight were demonstrated in following flights, where balloonists experienced and described for the first time the symptoms of hypoxia altitude sickness, increase in heart rate, fatigue DeHart First, a human would be sent into space as a passenger in a capsule Projects Vostok and Mercury.
Second, the passengers would acquire some control over the space vehicle Projects Soyuz and Gemini. Third, a reusable space vehicle would be developed that would take humans into Earth orbit and return them. Next, a permanent space station would be constructed in a near-Earth orbit through the utilization of the reusable space vehicle. Finally, lunar and planetary flights would be launched from the space station using relatively low-thrust and reusable and thus lower cost space vehicles. Just like for balloon flights, animals were sent up in rockets before humans to test if a living being could withstand and survive a journey into space Figure The first successful spaceflight for live creatures came on September 20, , when the former Soviet Union launched a sounding rocket with a capsule including a monkey and eleven mice.
A few attempts to fly animals had been made before in fact, since in the nose cones of captured German V-2 rockets during U. These attempts were made with one main purpose: to study the effects of exposure to solar radiation at high altitude, and to determine the effects, if any, of weightlessness Lujan and White This was an unmanned satellite, but before the end of the year a second satellite, Sputnik-2, was launched carrying the first living creature into orbit, a dog named Laika.
Laika had been equipped with a comprehensive array of telemetry sensors, which gave continuous physiological information to tracking stations.
The cabin conditioning system maintained sea-level atmospheric pressure within the cabin, and Laika survived 6 days before depletion of the oxygen stores caused 16 Fundamentals of the Space Medicine asphyxiation. Twelve other dogs, as well as mice, rats and a variety of plants were then sent into space for longer and longer duration between and In , a Soviet biosatellite Cosmos mission carried two dogs in orbit for 23 days. The dogs were observed via video transmission and biomedical telemetry. Their spacecraft landed safely.
In , one rhesus and one squirrel monkey rode in the nose cone of a U. Although one of the monkeys died from the effects of anesthesia given to allow the removal of electrodes implanted for the spaceflight, a subsequent autopsy revealed that the monkey had suffered no adverse effects from the flight. Between and , three other monkeys made suborbital flights in Mercury capsules, and one monkey flew two orbits around Earth in a Mercury capsule in preparation for the next, human flight Figure These experiments paved the way for human expeditions.
Credit NASA While these animals were in space, instruments also monitored various physiological responses as the animals experienced the stresses of launch, reentry, and the weightless environment. The results of these animal flights showed that: - Pulse and respiration rates, during both the ballistic and the orbital flights, remained within normal limits throughout the weightless state. Cardiac function, as evaluated from the electrocardiograms and pressure records, was also unaffected by the flights; - Blood pressures, in both the systemic arterial tree and the low-pressure system, were not significantly changed from preflight values during 3 hours of the weightless state; - Performance of a series of tasks of graded motivation and difficulty was unaffected by the weightless state; Introduction to Space Life Sciences 17 - Animals trained in the laboratory to perform during the simulated acceleration, noise, and vibration of launch and reentry were able to maintain performance throughout an actual flight.
The objectives were threefold: to place a human spacecraft into orbital flight around Earth, observe human performance in such conditions, and recover the human and the spacecraft safely. At this early point in the U. Could a human perform normally as a pilot-engineer-experimenter in the harsh conditions of weightless flight? If yes, who were the right people with the right stuff for this challenge?
In January , NASA received and screened service records of a group of talented test pilots, from which candidates were assembled. One month later, through a variety of interviews and a battery of written tests, the NASA selection committee brought down this group to 32 candidates. Each candidate endured even more stringent physical, psychological, and mental examinations, including total body X-rays, pressure suit tests, cognitive exercises, and a series of unnerving interviews. Of the 32 candidates, 18 were recommended for Project Mercury without medical reservations.
The following year, the Soviet Union announced that 20 fighter pilots had been selected for its space program. In , 5 female parachutists joined this first group of 20 male cosmonauts. On April 12, , Yuri Gagarin became the first human to orbit the Earth. Six weeks later, U. President Kennedy would announce as a national objective an accelerated space program to accomplish a landing on the Moon in the period.
Variations in cardiac rhythm had been recorded in one chimpanzee during a three-orbit mission Stringly It was found that the problem came from faulty instrumentation, and that the data were therefore invalid. Titov into orbit. The following day, August 7, Titov successfully landed after 17 orbits in 25 hours and 18 minutes.
This was the first human flight of more than one orbit, and the first test of human responses to prolonged weightlessness. Two years later, Valentina Tereshkova became the first woman in space Figure She remained in space for nearly three days and orbited the Earth 48 times. Unlike earlier Soviet spaceflights, Tereshkova was permitted to operate the controls manually. Although her spaceflight was announced as successful, it was 19 years until another woman flew in space, Svetlana Savitskaya, aboard Soyuz T-7 in Apparently, something went so wrong during Tereshkova's flight that no further flight included women.
Savitskaya must have turned out all right, since she flew twice, and during her second mission on board Soyuz T in July , was the first woman to ever perform a space walk. Soviet Cosmonaut Aleksei Leonov made the first space walk during the Voskhod-2 mission on March 18, He was followed by Astronaut Edward White who stepped out of Gemini-4 for 20 minutes. White propelled himself away from the spacecraft with a special gun that gushed out compressed oxygen to move him in any direction.
However, because his propulsion gun ran out of fuel, he had to pull on his life support system umbilical line to maneuver around and reenter the spacecraft. Russian cosmonaut Valentina Tereshkova after returning from a threeday spaceflight. Credit CNES 2. A more complex set of in-flight medical studies was carried out during the Introduction to Space Life Sciences 19 Gemini missions, which served as precursors to the lunar missions Figure Among those missions, Gemini-7 December primary objective was to conduct a two-week mission and evaluate the effects of long-term exposure to weightlessness on its crew.
Many medical experiments were conducted in-flight, including on vision and sleep. Extensive testing, for example on balance, was also performed just after landing. Blood and urine samples were collected throughout the mission for analysis, and astronauts exercised twice daily using rubber bungee cords. This experiment used a visual acuity goggle combined with measured optical properties of ground objects and their natural lighting, as well as the atmosphere and spacecraft window. The results failed to show that the visual acuity was improved while in space.
Also interesting is the Gemini flight, where artificial gravity was involuntarily first tested in space. The Gemini spacecraft was tethered to an Agena target vehicle by a long Dacron line, causing the two vehicles to spin slowly around each other. Comparison between the Mercury, Gemini, and Apollo manned spacecrafts.
Mercury could accommodate only one crewmember, Gemini two, and Apollo three crewmembers. Credit NASA 20 Fundamentals of the Space Medicine Significant orthostatic hypotension and weight loss were observed in the crewmembers of Gemini-3, -4, -5, and -6 immediately after flight see Chapter 4. Scientists were concerned that spaceflight might affect the balance of body fluids and electrolytes since fluid losses can contribute to both of these symptoms. This led to a series of ground-based studies to simulate some of the conditions of spaceflight. These studies utilized bed rest and water immersion as a means of simulating microgravity.
In addition, Biosatellite-3 was launched in , three weeks before the first men were to land on the Moon, with a monkey passenger. The flight was planned for a full month, but the monkey was brought down, ill from loss of body fluids, after only nine days. It died shortly after landing. Despite the concern that the same problem could occur to humans, the Apollo missions to the Moon proceeded as planned. During the Apollo missions, a medical program was developed which would make provision for emergency treatment during the course of the mission in case a serious illness occurs.
Indeed, during the orbital flights of Mercury and Gemini, it was always possible to abort the mission and recover the astronaut within a reasonable time should an in-flight medical emergency occur. This alternative was greatly reduced during Apollo. The events of Apollo showed that this medical program proved effective. Biomedical findings of the Apollo program revealed a decreased in postflight exercise capacity and red blood cell number, a loss of bone mineral, and the relatively high metabolic cost of extra-vehicular space walk activity.
Credit NASA. Introduction to Space Life Sciences 21 In addition, symptoms of space motion sickness such as nausea and vomiting, earlier described by Soviet cosmonauts, were experienced. The U. Skylab Figure and the Soviet Salyut space stations allowed scientists to conduct investigations on board large orbiting facilities during missions lasting up to 3 months.
They gave a basic picture of how the body reacts and adapts to the space environment. The number of subjects was, however, still limited. Also, as the first spacecraft that could be used again and again, the Space Shuttle has provided space life scientists with a more regular opportunity to conduct experiments, and to repeat and refine those experiments.
However, with the Space Shuttle, other concerns appeared. The Space Shuttle was remarkably different from the previous spacecrafts because it returned to Earth by landing on a runway Figure Critical issues existed concerning the ability of crews to perform the visual and manual tasks involved in piloting and landing the Shuttle, and their capacity to achieve unaided egress after long exposure to weightlessness.
It was later found that the astronauts-pilots were able to pilot and manually land the Space Shuttle, as long as the flight duration did not exceeded two weeks.
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In fact, astronauts returning from Shuttle missions reported that the simulations were so accurate they felt they had flown the mission many times. Space Shuttles also conducted crew exchanges and delivered supplies and equipment. Comparison between the sizes of the Russian Mir space station dark gray and the International Space Station in its final configuration light gray. More than four times as large as the Russian Mir space station Figure , the completed International Space Station will have a mass of about tons and more than m3 of pressurized space in six state-of-the-art laboratories Table The United States will provide two laboratories United States Laboratory and Centrifuge Accommodation Module and a habitation module for four crewmembers.
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An ISPR, about the size of a home refrigerator, holds research equipment and experiments. Additional research space will be available in connecting nodes and the Russian modules. The experiments will be set outside using a small robotic arm on the JEM. There are also four attached payload sites on the truss and two spaces on the COF for mounting external experiments. Once completed, the ISS will house an international crew of up to seven for stays of approximately three months.
Emergency crew-return vehicles will always be docked with the ISS while it is inhabited, to assure the return of all crewmembers. A Russian Soyuz spacecraft, which has a crew capacity of three, is presently used. It is important to realize that the ISS is far more than a science platform alone. The ISS constitutes a highly visible signature in the sky for human endeavor, courage, spirit, and international peaceful collaboration, and it is the greatest technological challenge the human race has tackled so far.
To a large part this was the early political motivation that led to its conception. In addition, and looking more towards the future the ISS provides the gateway for human exploration of the solar system. The ISS has also the potential for becoming an ideal tool to support educational activities. In particular, educational programs encouraging and supporting the study of science, mathematics, technology and engineering can be implemented on board the ISS, making use of its facilities and resources.
Other education projects can be implemented that focus not only on science and technology, but also on a larger variety of subjects, such as languages, composition and art. For this reason, the crew on board ISS is currently limited to two persons. Fundamentals of the Space Medicine 24 approval, in return for a promise by the Russians to meet new standards for paying visitors in the future. The objective is to launch a spacecraft carrying three or more people to a height of at least km and then repeat the process within two weeks.
Note added for this 2nd revision: In its preliminary attempt to claim the X-Prize, the first private manned space vehicle flew to the edge of space and back on June 21, The SpaceShipOne craft, built by aviation pioneer Burt Rutan, went over space's km boundary, and landed safely after a minute flight. Introduction to Space Life Sciences 2. The predictions made by scientists about the ability of humans to endure spaceflight were indeed dire.
Despite groundbased studies proving the contrary, there was true concern that the g forces of launch and reentry 6 to 8 g for the earliest spacecraft would render human passengers unconscious, severely impaired or even dead. The mystique of this alien environment was so great that many feared a psychotic breakdown when humans would find themselves disconnected from and looking down on mother Earth.
The first space missions showed, however, with the proper protection, humans could survive a journey into space. Biomedical changes have been observed during spaceflight, due to the effects of microgravity, but also to other phenomenon, such as high launch and reentry gravitational forces, radiation exposure, and psychological stress. To illustrate of what we do know at this point, my colleague and friend Susanne Churchill, in one of her lectures at the International Space University, used to describe the space journey of an hypothetical space traveler who experiences all of the known problems.
I will use the same approach below. So, let us take a journey with our hypothetical astronaut. She is in excellent health and fully trained for the rigors of her 3-month increment on board ISS. Launch occurs as anticipated: a couple of hours before launch she had joined the others lying down in the seats of the Space Shuttle, strapped in, feet above head, as in the early Mercury, Gemini, or Apollo launches.
But there, the similarity ends. For during Shuttle lift-off she does not undergo the unpleasant gravity load, which went as high as 8 g on earlier flights. Instead, she experiences 3 g only twice. The first time comes and goes quickly near the two-minute mark, just before the two solid rocket boosters burn out and drop by parachute into the Atlantic Ocean.
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Less than ten minutes from lift-off, she finds herself floating in the weightlessness of space. Without warning, however, she suddenly vomits and is overwhelmed with intense symptoms of motion sickness: nausea, a sense of dizziness, and disorientation. Her symptoms become worst when she moves about in the cabin or sees one of her fellow crewmembers floating upside-down.
She is unable to keep food down and rejects even water to drink, so she quickly dehydrates. She is concerned that she could not help the rest of her crew with the rendez-vous procedures of the Shuttle with the ISS, since looking out of the windows triggers more symptoms.
She takes some pills and is getting ready for sleep. However, when looking in the mirror above the wash basin, she realizes that her eyes seem smaller, her face is round and puffy Figure , and her neck veins bulging. The good news is that her wrinkles have disappeared and she looks younger. When undressing, she notices that her legs look like sticks. She tries to sleep but has a persistent backache, a definite feeling of sinus congestion, and keeps waking to discover that her arms are floating above her head.
So disconcerting! The normal face of the astronaut of Earth left is contrasted with the swollen-looking face of the astronaut in space right. Because of the absence of perceived gravity, her vertebrate disks are less compressed, making her height increase by cm Figure and causing continuing back pain. Her shoes have also become too loose. Within a couple of days, the motion sickness symptoms begin to subside, through her face and legs remain changed. Her posture too, is different, but not for the better.
Joints go to their midpoint in zero gravity so that the hips and knees are bent into a slight crouch. Her arms tend to float in front of her unless she consciously holds them down. When she sits at a workbench, she has to strap herself in place. Even so, her seated posture is to lean back. Nevertheless, she learns to move around in weightlessness by gently pushing and pulling her body with her fingertips.
Introduction to Space Life Sciences 27 Figure Diagram showing the increase in the height of an astronaut during the first hours of a spaceflight. Adapted from Thornton and Moore Rendezvous and transfer to the ISS occur without incident and she starts to settle for a 3-month stay on board with her two fellow crewmates. There are experiments to monitor and several hours of exercise daily on the treadmill or cycle ergometer. After a few weeks, however, the routine is boring and it becomes harder and harder to keep up with the exercise. The more she looks out of the window, the more she longs for the sounds of rain and wind, and the smells of flowers.
However, when she closes her eyes, she experiences light flashes, especially when the ISS flies over the South Atlantic Anomaly. The crew starts to argue about the smallest things. One planned space walk has to be cancelled because of a persistent irregular heartbeat in one of the crewmember. Since that incident, this crewmember seems to be withdrawing from the others.
The weekly videoconferences with family and friends are eagerly anticipated, but she wonders why there has been no communication from her youngest child for several weeks. Has something happened? Anxiety arises and she has a persistent pain in her lower abdomen, which, if it continues, might prompt an emergency evacuation to Earth. But at last the time to return approaches. An interesting mixture of excitement and anxiety pervades the crew. Visions of favorite foods and what to do first are the main topics of conversation.
Yet, the group has become so firmly a part of each other that the thoughts of reintegrating into Earth society are intimidating. But at last the crew is on its way home. When donning her reentry space suit, she realizes it is too tight because she has grown up of a few centimeters. During the reentry into the Earth atmosphere our traveler experiences disorientation again when she tilts or rolls her head.
Her heart is beating fast; she sweats and almost faints. Even after several days of rehabilitation, balance is poor and walking uncoordinated. Fundamentals of the Space Medicine 28 Muscle weakness is very evident; she quickly feels short of breath and is constantly thirsty. Weight loss that occurred in space is rapidly disappearing, but her physician tells her that she had lost much of bone density in her hips and that her immune system seems to be impaired. Now she is concerned because she remembers that the various bacterial colonies they were studying on board the ISS laboratories showed explosive growth rates!
Several months later though, all her body functions seem to have readapted to Earth gravity. This story is not meant to discourage anyone from wanting to be an astronaut. In reality, not all people experience all of the adverse effects of spaceflight. The interpretations for the observed physiological and psychological changes during spaceflight will be detailed in Chapters 3, 4, 5, 6, and 7 of this book. Protecting humans from these harmful conditions requires the use of life support equipment and technologies such as space suits, pressurized and isolated living quarters, and radiation shielding.
In addition, certain basic physiological needs must be met in order for human beings to stay alive.
On Earth, these needs are met by other life forms in conjunction with chemical processes that effectively use human waste products in conjunction with energy from the Sun to produce fresh supplies of food, oxygen and clean water. When the point is reached where it is no longer cost effective or logistically possible to re-supply the spacecraft or habitat with water, atmosphere, and food, ways must be found to recycle all these components.
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Think of the human body as a sealed box with one pipe in and one pipe out. In go oxygen O2 , water and food; out come solid and liquid wastes, bacteria, and carbon dioxide CO2. The outlet pipe is fed into a second sealed box, the controlled ecological life support system CELSS. Introduction to Space Life Sciences 29 Figure A controlled ecological life support system CELSS employs biological components and uses higher plants. Higher plants are easily digestible and are customary sources of human food. Besides producing food they also remove carbon dioxide from the atmosphere, produce oxygen, and purify water through the process of respiration.
Trying to recreate the cycles of nature in a relatively small volume is a great technical challenge. But in nature the nutrients, air, water, and energy are freely available. For example: How far can we reduce reliance on expendables? How well do biological and physic-chemical life support technologies work together over long periods of time?
How do various contaminants accumulate and what are the long-term cleanliness issues? Eventually, in the case of planetary missions, is it possible to duplicate the functions of the Earth in terms of human life support, without the benefit of the Earth's large buffers—oceans, atmosphere, land masses? How small can the requisite buffers be and yet maintain extremely high reliability over long periods of time in a hostile environment? Eckart has addressed most of these questions. We will summarize them in Chapter 7 Section 5. One of the primary objectives of space life sciences is to ensure the health of crewmembers working on board the spacecraft and in the hostile environment outside their vehicles.
Responsibilities of the operational medicine program include preflight activities such as screening and selecting new astronaut candidates, health stabilization , in-flight activities such as the administration of countermeasures and medical care , and postflight procedures such as rescue after an emergency landing or rehabilitation for a prompt return of crewmembers to flight status.
Based on the knowledge of specific health risk factors associated with spaceflight, appropriate and proven tests are utilized in selecting the astronauts. Annual medical evaluations are then performed to identify and correct medical risks to maintain health, provide certification for flight duties, and ensure career longevity. These tests may include further clinical evaluation e. Both selection and periodic medical evaluations rely on the accepted ground-based standards of preventive medicine, health maintenance, and medical practice.
These standards are revised on a periodic basis to ensure that they are fair and appropriate to meet the needs of human spaceflight. During preflight training, the primary emphasis of medical support is on prevention. For example, the purpose of the Crew Health Stabilization program is to prevent flight crews from exposure to contagious illness just before launch.
A preflight quarantine limits access to flight crew during seven days just prior to launch. Even before this period, the health of an active duty crewmember family is of critical importance, and factors such as infectious disease and stress affecting a crewmember family may have serious adverse Introduction to Space Life Sciences 31 effects on the crewmember health and performance, as well as the health and performance of other crew members.
Crewmembers are also trained in the use of special countermeasures to spaceflight physical deconditioning and in medical monitoring and clinical practice procedures. Medical training for the crew, medical supervision of mission planning, schedules, payloads, exercise training, and conditioning, and other health maintenance activities are all part of the preflight period. Astronaut during a spacewalk or extra-vehicular activity EVA in the vacuum of space. Health monitoring and medical intervention, countermeasures to body functions deconditioning, and environmental monitoring enable a comprehensive program tailored to crew and mission needs and for the periodic assessment of crew medical status, including the identification of potential and unexpected health risks.
Among these potential health risks are the levels of acceleration, vibration, and noise during launch, the exposure to toxic substances and pressure changes, and the risk due to radiation. With the possible exception of the immune system, body changes that occur after entering microgravity represent normal homeostatic responses to a new environment. In-flight, typical adaptive and patho-physiological 32 Fundamentals of the Space Medicine changes occur in the heart and blood vessels dysrhythmias , muscles strength , bones fractures, renal stones , nervous system disorientation and nausea , and in the immune system infection.
Space-walks or extravehicular activity EVA Figure can also be responsible for strain on muscles and bones, and decompression-related disorders. Psycho-sociological issues become increasingly more important as space missions become longer, and spaceflight teams become larger and more heterogeneous. The isolated, confined, and hazardous environment of space create stress beyond that normally encountered on Earth, even when training for a space mission.
Extended duration missions place an even greater stress on individuals, interpersonal, and group relations for astronaut crews, between astronaut crews and ground control, and on astronaut families. Current countermeasures focus primarily on the individual, mission crew, and to some extent the families of mission crews, by providing psychological training and support through in-flight communications. Finally, for spaceflight missions, emphasis is not only on health maintenance, disease prevention, and environmental issues, but also on the provision of medical care to manage possible illnesses and injuries.
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Comparison of the direction and amplitude of g forces experienced during the landing between a Soyuz capsule left and the Space Shuttle right. Less g forces are tolerated when directed along the body longitudinal axis Gz , in a direction parallel to the big blood vessels see Chapter 4, Table During return to Earth, piloting tasks are challenged by the presence of g forces in deconditioned individuals Figure These difficulties could prove dramatic in the case of a non-nominal landing where the crew may be required to egress in emergency the vehicle with no help from ground support.
Astronauts must have career longevity, normal life expectancy, with rehabilitation and recovery capabilities available upon their return from spaceflight. After landing, health monitoring and physical rehabilitation are performed to accelerate the return of crewmembers to normal Earth-based duties. An important factor to take into account is the return to flight status for pilot astronauts.
There is a large catalog of reported postflight symptoms captured in the mission medical debriefs which are collected after a space mission through interviews between the astronauts and crew flight surgeon. After every Shuttle mission, a NASA flight surgeon holds a medical debrief with each crewmember on the day of landing and then three days later.
Standardized debrief forms are utilized during these meetings, at which time the physician and crewmember discuss pre-, in-, and postflight medical issues. The crewmembers are interviewed about their experiences, utilizing both open-ended and specific questions. Such studies are particularly relevant regarding the issues of radiation exposure.
Spacecrafts are closed compartments, and therefore standards for air, water, microbiology, toxicology, radiation, noise, and habitability must be established. In-flight environmental monitoring systems are available to prevent crew exposure to toxicological and microbial contamination of internal air, water, and surfaces; to radiation sources from within and external to the spacecraft; to vibration and noise.
These systems must have near realtime and archival sampling, and provide a mechanism to alert crewmembers when measured values are outside acceptable limits. Habitability issues regarding human presence in space includes human factor design considerations colors, equipment layout, and hardware design , adequate and ergonomically correct work and living volume, with similarly adequate stowage volume. Areas must be designed that allow for restful sleep and personal space, with adequate lighting and exterior views.
Schedules must produce interesting work, with sufficient rest and recreation periods to avoid chronic fatigue. Time and resources are set aside for personal hygiene and sanitation see Chapter 7, Section 5. In addition, healthy, palatable variety of food and beverage is provided Table The daily food supply totals a high calories, plus snacks. Irradiated Foods preserved by exposure to ionizing radiation and packed in flexible foil laminated pouches.
Intermediate Moisture Dried foods with low moisture content such as dried apricots. Packed in flexible pouches. Freeze Dried Foods that are prepared to the ready-to-eat stage, frozen and then dried in a freeze dryer that removes the water by sublimation. Freeze-dried foods such as fruits may be eaten as is while others require the addition of hot or cold water before consumption. Re-Hydratable Dried foods and cereals that are re-hydrated with water produced by the Shuttle Orbiter's fuel cell system.
Packed in semi-rigid plastic container with septum for water injection. Natural Form Foods such as nuts, crunch bars, and cookies. Packed in flexible plastic pouches. Beverages Dry beverage powder mixes packed in re-hydratable containers. Table The Space Shuttle menu currently features more than 70 food items and 20 beverages.
Shuttle crewmembers have a varied menu every day for six days. Each day, three meals are allowed, with a repeat of menus after six days. The pantry also provides plenty of foods for snacks and between meal beverages and for individual menu change. Nowadays, attention is given to individual crewmember preference with regard to palatability and nutritional adequacy of food items during missions. Medical and psychological personnel have also an opportunity to review all design considerations early in the design process to ensure that spacecraft design and support systems meet medical and psychological requirements.
Only cooperation in the realization of such a multi-billion dollar program with a corresponding distribution of tasks and costs appears to be a viable option. A human Mars mission can also be regarded as an important cultural task for humankind with the objective to globalize the view of our home planet Earth, thereby contributing to the solution of local conflicts.
In any case, a human Mars mission would meet the natural human need to explore and expand to new regions. Obviously, for a cost-effective Mars exploration, an appropriate combination of unmanned and manned activities supplementing each other in a logical way will be developed e.
In this context the development and test of technologies for in-situ resources utilization e. According to conventional spacecraft configurations that have mainly been designed until , the total departure mass of a manned spacecraft in low Earth orbit is around tons. That is if the mission is carried out in one-shot with a 4-stage expendable vehicle on a low energy transfer, using oxygen and hydrogen propellants for the main propulsion systems.
Using the current rocket technology, traveling between Earth and Mars will require lots of fuel and good timing. The first leg will take days. Astronauts must wait on Mars for their launch toward home until Earth is in alignment. Total mission duration is then days Figure One possible scenario for a Mars mission. Top: Schematic of the orbits of Earth and Mars showing their position for a more fuel-efficient trajectory during launch.
Bottom: The respective positions of the Earth and Mars determine both the duration of travel and stay on the Mars surface. Adapted from National Geographic Luckily, the Mars gravity of 0. However, landing maneuvers on Mars and Earth are characterized by maximum g-loads of up to 6 g due to the atmospheric drag. If the interplanetary cruise is carried out a zero gravity level i. The crew needs to be protected against the occasional solar flare. Cosmic rays are a different story. They are constantly present, coming from all directions.
The radiation consists of heavy, slow moving atomic nuclei that can do far more damage to more cells than alpha and beta particles. Introduction to Space Life Sciences 37 This radiation requires several meters of shielding for complete blockage, and since the nuclei come from all directions at all times, unlike the brief solar flares that last only a few hours or days, a storm shelter would be insufficient to protect the crew. Even if such a system proves difficult to engineers, some scientists believe that the cosmic ray doses can simply be endured. Sign up to the hive. Discover bookshops local to you.
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