**2. The desire to fly**

The humankind in this field even turned to the imagination. He always dreamed about the angels, carrying two flights on the back of them. He made stories and myths like Icarus about flying and releasing to the sky.

Problems gradually showed up themselves. The first problem was the separation from the Earth. Every time that he jumped up, he fell on the ground again, even from towers. Each time he tried to get higher, the gravity did not allow him to move away from the Earth, and he was returned. He then realized that he had to use a special force to win over and dominate the gravity. Little by little he took more serious actions, designed to make practical models of flight. The Chinese invented a rocket, which had the necessary power for overcoming the gravity. Leonardo da Vinci was a brilliant scientist, designer, and inventor of the field in the fifteenth century.

*A Journey through Space* was written by William Leitch in 1861. He was a Scottish astronomer and mathematician. He announced the theory of traveling to space with rockets [2].

Russian scientist Konstantin Eduardovich Tsiolkovsky (1857–1935) wrote about going to space using special devices in 1903 (the same year as the Wright brothers' flight) [2].

At last, the man could be separated from the Earth to fly in the sky. The German Otto Lilienthal (1848–1896) studied flying scientifically and had 200 gliding flights in the second half of the nineteenth century [3]. The Wright brothers (Orville, 1871–1948 and Wilbur, 1867–1912) as American aviation pioneers made the first piloted flights in 1903 [4]. Now it was the time to provide suitable facilities to fly longer or to reach higher.

The past Soviet Union (current Russia) sent the first human (Yuri Gagarin, 1934–1968) to the orbit on April 12, 1961. They had sent animals to space before this exciting experiment. The first animal was a Russian dog called Laika 1 month after the launch of Sputnik on November 3, 1957. Russians sent six dogs to the orbit from 1960 to 1961. A chimpanzee called Enos was the first animal sent to space by the USA on November 29, 1961. John Glenn was the first American astronaut in space on February 20, 1962 [5].

Since the flight of Yuri Gagarin, more than 500 people have flown to the orbit of the Earth. Even a few have advanced beyond the orbit, the Moon.

After starting to fly, humans realized that there would be more problems at higher altitudes. One problem became evident when he went a bit higher. The atmosphere became thinner and thinner, so he was forced to struggle for breathing. Then he had to make the flight device so sealed that it could regulate the air inside to have no respiratory problems or other problems due to lack of oxygen and hypoxia. He designed and made special balloons for flying at high altitudes (rediscovery of hot air balloon by the Montgolfier brothers) [6].

At the same time, scientists noticed that everything could not be experienced in the sky (or space) and during flight. Unfortunately, some experiences led to fall, collapse, and death. The experiments were commenced on the Earth by simulating different models (from cells to animals and finally up to human beings).

At that time, the new problems appeared one after another. The man noticed that by going farther from the surface of the Earth, there would be less gravity. Somewhat farther, he almost did not feel any gravity. Weightlessness had occurred.

Other problems were included as exposure to radiation and its resulting discomforts. So, on the one hand, the man had to think about the ways continuing to fly and perform missions successfully and, on the other hand, not to confront any physical problem himself, doing his best with maximum efficiency and power.

The efficient hypothesis was that the astronaut should be able to maintain his abilities in long-term flights up to the end and to act effectively meanwhile. In recent decades, 6-month missions have been carried out regularly in Russia's Salyut, the Mir station, and the International Space Station (ISS), respectively [7]. In addition to such missions, various studies have been done on human body changes

**65**

*Vitamin D in Space*

should be considered:

*DOI: http://dx.doi.org/10.5772/intechopen.82314*

1.Changes in acceleration at two steps:

ent amounts of oxygen)

a.When the spacecraft rises from the ground

for exploratory missions beyond the Earth's orbit [8].

conditions, although this understanding is still incomplete.

in space travels and missions, in order to grasp the practical concept of adaptive

within itself. Regular and planned efforts have been made to understand these changes and alterations in order to allow protection and countermeasures development and implementation against harmful effects. The field of optimization of human performance in every respect is provided. In this context, the following

The space environment and space travel have particular challenges and dangers

b.At landing on the surface of other planets or upon returning to the Earth

(from full extent until its complete absence during weightlessness)

3.Other features such as radiation (including ionizing radiation)

2.Different atmosphere compositions (containing variable pressures and differ-

It is nearly two decades since the establishment of the first component of ISS in 1998. It is believed to operate until 2028. Several long-term missions have been planned to accommodate astronauts. The main goal is to get the ultimate readiness

The American and Russian space programs were ambitious and, at the same time, scientific and full of research. Their main goal was the long-term deployment of systems and platforms in the Earth's orbit to make orbit stations. They intended to send astronauts to these platforms and stations for long-duration missions. Astronauts had to stay and work at space stations for a long time so that reliable research could be done in this area. Scientists achieved much more about physiological and pathological changes in the space. The complete adaptation of the human body to weightlessness would take several weeks, which could not be provided by previous spaceships [9]. Also, many experiments and researches were possible to be done in this case.

Sometimes later, the scientific thoughts looked farther, beyond the Earth's orbit. Terrestrial missions refer to those space missions that are far from the orbit, where there is no longer any protective effect of the atmosphere and the electromagnetic fields, and they will not affect the spacecraft longer. The American Apollo programs are among these series of missions that consisted of nine missions and flights to the Moon. In six missions, two astronauts landed on the surface of the Moon. Each trip lasted between 8 and 12 days, which spent 3 days traveling from the Earth to the Moon. An essential point about Apollo's trip was the ability of humans to perform physical activities in an environment with gravity much lower than on the Earth's surface, equivalent to one-sixth. It is worthy to mention that gravitational force on

With the advent of space exploration by Vostok 1 and Yuri Alekseyevich Gagarin's

the surface of Mars is twice that of the Moon and a third of the Earth [10].

journey in 1961, the man has been exposed to space-related problems including microgravity [2]. The cells, tissues, systems, and the human body as a whole are generally exposed to different physiology other than the physiology that dominates our planet and undergoes alterations. Of course, the musculoskeletal system is among those systems that have the most changes and problems, especially in the face of microgravity, such as bone mineral density decrease and muscle atrophy [11].

#### *Vitamin D in Space DOI: http://dx.doi.org/10.5772/intechopen.82314*

*Fads and Facts about Vitamin D*

rockets [2].

flight) [2].

longer or to reach higher.

on February 20, 1962 [5].

Problems gradually showed up themselves. The first problem was the separation from the Earth. Every time that he jumped up, he fell on the ground again, even from towers. Each time he tried to get higher, the gravity did not allow him to move away from the Earth, and he was returned. He then realized that he had to use a special force to win over and dominate the gravity. Little by little he took more serious actions, designed to make practical models of flight. The Chinese invented a rocket, which had the necessary power for overcoming the gravity. Leonardo da Vinci was a

*A Journey through Space* was written by William Leitch in 1861. He was a Scottish astronomer and mathematician. He announced the theory of traveling to space with

Russian scientist Konstantin Eduardovich Tsiolkovsky (1857–1935) wrote about going to space using special devices in 1903 (the same year as the Wright brothers'

At last, the man could be separated from the Earth to fly in the sky. The German Otto Lilienthal (1848–1896) studied flying scientifically and had 200 gliding flights in the second half of the nineteenth century [3]. The Wright brothers (Orville, 1871–1948 and Wilbur, 1867–1912) as American aviation pioneers made the first piloted flights in 1903 [4]. Now it was the time to provide suitable facilities to fly

The past Soviet Union (current Russia) sent the first human (Yuri Gagarin, 1934–1968) to the orbit on April 12, 1961. They had sent animals to space before this exciting experiment. The first animal was a Russian dog called Laika 1 month after the launch of Sputnik on November 3, 1957. Russians sent six dogs to the orbit from 1960 to 1961. A chimpanzee called Enos was the first animal sent to space by the USA on November 29, 1961. John Glenn was the first American astronaut in space

Since the flight of Yuri Gagarin, more than 500 people have flown to the orbit of

After starting to fly, humans realized that there would be more problems at higher altitudes. One problem became evident when he went a bit higher. The atmosphere became thinner and thinner, so he was forced to struggle for breathing. Then he had to make the flight device so sealed that it could regulate the air inside to have no respiratory problems or other problems due to lack of oxygen and hypoxia. He designed and made special balloons for flying at high altitudes (rediscovery of

At the same time, scientists noticed that everything could not be experienced in the sky (or space) and during flight. Unfortunately, some experiences led to fall, collapse, and death. The experiments were commenced on the Earth by simulating

At that time, the new problems appeared one after another. The man noticed that by going farther from the surface of the Earth, there would be less gravity. Somewhat farther, he almost did not feel any gravity. Weightlessness had occurred. Other problems were included as exposure to radiation and its resulting discomforts. So, on the one hand, the man had to think about the ways continuing to fly and perform missions successfully and, on the other hand, not to confront any physical problem himself, doing his best with maximum efficiency and power. The efficient hypothesis was that the astronaut should be able to maintain his abilities in long-term flights up to the end and to act effectively meanwhile. In recent decades, 6-month missions have been carried out regularly in Russia's Salyut, the Mir station, and the International Space Station (ISS), respectively [7]. In addition to such missions, various studies have been done on human body changes

different models (from cells to animals and finally up to human beings).

the Earth. Even a few have advanced beyond the orbit, the Moon.

hot air balloon by the Montgolfier brothers) [6].

brilliant scientist, designer, and inventor of the field in the fifteenth century.

**64**

in space travels and missions, in order to grasp the practical concept of adaptive conditions, although this understanding is still incomplete.

The space environment and space travel have particular challenges and dangers within itself. Regular and planned efforts have been made to understand these changes and alterations in order to allow protection and countermeasures development and implementation against harmful effects. The field of optimization of human performance in every respect is provided. In this context, the following should be considered:

	- a.When the spacecraft rises from the ground
	- b.At landing on the surface of other planets or upon returning to the Earth (from full extent until its complete absence during weightlessness)

It is nearly two decades since the establishment of the first component of ISS in 1998. It is believed to operate until 2028. Several long-term missions have been planned to accommodate astronauts. The main goal is to get the ultimate readiness for exploratory missions beyond the Earth's orbit [8].

The American and Russian space programs were ambitious and, at the same time, scientific and full of research. Their main goal was the long-term deployment of systems and platforms in the Earth's orbit to make orbit stations. They intended to send astronauts to these platforms and stations for long-duration missions. Astronauts had to stay and work at space stations for a long time so that reliable research could be done in this area. Scientists achieved much more about physiological and pathological changes in the space. The complete adaptation of the human body to weightlessness would take several weeks, which could not be provided by previous spaceships [9]. Also, many experiments and researches were possible to be done in this case.

Sometimes later, the scientific thoughts looked farther, beyond the Earth's orbit. Terrestrial missions refer to those space missions that are far from the orbit, where there is no longer any protective effect of the atmosphere and the electromagnetic fields, and they will not affect the spacecraft longer. The American Apollo programs are among these series of missions that consisted of nine missions and flights to the Moon. In six missions, two astronauts landed on the surface of the Moon. Each trip lasted between 8 and 12 days, which spent 3 days traveling from the Earth to the Moon. An essential point about Apollo's trip was the ability of humans to perform physical activities in an environment with gravity much lower than on the Earth's surface, equivalent to one-sixth. It is worthy to mention that gravitational force on the surface of Mars is twice that of the Moon and a third of the Earth [10].

With the advent of space exploration by Vostok 1 and Yuri Alekseyevich Gagarin's journey in 1961, the man has been exposed to space-related problems including microgravity [2]. The cells, tissues, systems, and the human body as a whole are generally exposed to different physiology other than the physiology that dominates our planet and undergoes alterations. Of course, the musculoskeletal system is among those systems that have the most changes and problems, especially in the face of microgravity, such as bone mineral density decrease and muscle atrophy [11].

Microgravity and cosmic radiation are two important dilemmas that exist in the space environment affecting human health and endangering it. They significantly affect the future of long-term space travels and would limit them [12].

In a long space trip, including a trip to Mars, astronauts are exposed to large amounts of radiation which is much higher than the magnitude permitted by the NASA's system of protection [13].

## **3. History**

In the twentieth century, spaceflight became real. The modern space exploration era begins in 1961 with Vostok 1 and Yuri Gagarin's journey because human travel to space is the most important event in this regard [2] although other measures, including the first orbital spaceflight (1957) and release of animals to space, were done earlier [5].

Nowadays in medicine and biology, Yuri Gagarin is a gene in *Drosophila* which has codes for three proteins [14].

In the USA, the National Advisory Committee for Aeronautics (NACA) became NASA on 1958 [1].

The first human who landed and walked on the Moon on July 20, 1969, was Neil Armstrong (1930–2012, American astronaut and commander of the Apollo 11). His colleagues were Michael Collins and Edwin Aldrin [1].

The deployment of ISS in the low Earth orbit (LEO) was carried out to rotate the human body around the Earth at the height of about 400 km; then another great mission was performed. Ninety percent of gravity at ground level will be endured by astronauts in LEO [9].

So far, about 90 astronauts have arrived at the ISS, with an average length of stay of about 6 months (6). The Apollo program included human missions and spaceflights above LEO. The program ended in 1972. During this program, 12 astronauts traveled to the Moon, which lasted for a few days [10].

The Chinese are trying hard to build their space station which will be built around 2020 [11].

### **4. Spaceflights, Earth, Mars, and again Earth**

Astronauts are preparing to travel to Mars now. Two and a half years are considered for this mission, part of it for spaceflight and the remaining for settlement and scheduled activities on the planet [15].

They are exposed to weightlessness in their 6-month course, which seems to make them physically very disable and inefficient at the end of the flight [7].

Most astronauts will encounter problems in spatial orientation and balance during the first few days after landing. They will be at risk for fractures and muscle tears during recovery period [9].

If the astronauts reach Mars with a weak and inadequate physical condition, having no solution to perform their basic tasks, the mission will face serious risks and will almost fail. Astronauts will endanger greater risks by sensory-motor impairment during spaceship control, off-vessel operations, or remote-controlled tasks. As long as the problems caused by weightlessness were not solved successfully, it is not wise to consider the long-term human journeys and missions like going to Mars [9].

Nowadays, human exploration missions to the Moon or Mars are considered as the next logical steps in the space era. In some cases, even human dispatch and

**67**

*Vitamin D in Space*

*DOI: http://dx.doi.org/10.5772/intechopen.82314*

• A significant number of travelers

cians should overcome [9].

• Longer flights and farther distances

**5. Types of simulation of space travel**

1.Human:

about 6°)

seconds [18].

migration, and colonization in other worlds, have also been announced. Almost all major national and international organizations in the world, as well as private investors and business plans, are currently developing roadmaps and related technologies to bring a healthy human to other planets of the solar system. Gradually, it seems that mankind is going to imagine about frequent and extended space trips, so that interplanetary traveling is equivalent to the concept of intercontinental flights. The human spaceflight perspective looks at the following to achieve in a short period:

• Sustainable deployment of humans to other planets as well as colonization

Many different challenges would be encountered that scientists and also politi-

Most of the medical challenges that were faced during humanitarian missions and related steps were mainly due to radiation and effects of microgravity (or hypogravity) as well as psychological issues [8]. In future exploratory missions for the Moon and Mars, the crew will be exposed to problems of the permanent base establishment on the planet, long-duration flights and missions, radiation intensity, microgravity, and the different impressions of constraints and isolation. It poses several health issues that may be a limiting factor during these missions. The health and performance of the crew should be ensured during journeys on the transfer and discovery of the planet's surface, external vehicle activities, and after returning to the Earth. In particular, the mission to Mars includes more challenges: the planet's distance, travel time (at least 500 days), and the impossibility of suspending the missions that necessitates an entirely stable mission. There could not be any support

a.Bed rest (prolonged bed rest protocols and head-down tilt experiments,

Head tilt is the most used space analog in scientific researches. The head is tilted down (−6° almost in all cases) during lying in a bed for different periods according to the study. There would be a cephalic fluid shift, immo-

b.Separation and isolation environments (similar to studies conducted in

c.Parabolic flight: although weightlessness will be executed only for some

An airplane has alternative flies so that there would be three phases (normal gravity, hypergravity, and microgravity) in each period. Microgravity lasts about

Antarctica or research that people live in and operate in specific environments and chambers, such as those conducted by volunteers traveling to Mars) [17]

from the Earth in the major health problem or technical one [9].

bilization, and isolation in this kind of modeling [16].

## *Vitamin D in Space DOI: http://dx.doi.org/10.5772/intechopen.82314*

*Fads and Facts about Vitamin D*

NASA's system of protection [13].

has codes for three proteins [14].

colleagues were Michael Collins and Edwin Aldrin [1].

traveled to the Moon, which lasted for a few days [10].

**4. Spaceflights, Earth, Mars, and again Earth**

scheduled activities on the planet [15].

tears during recovery period [9].

NASA on 1958 [1].

by astronauts in LEO [9].

around 2020 [11].

**3. History**

Microgravity and cosmic radiation are two important dilemmas that exist in the space environment affecting human health and endangering it. They significantly

In the twentieth century, spaceflight became real. The modern space exploration era begins in 1961 with Vostok 1 and Yuri Gagarin's journey because human travel to space is the most important event in this regard [2] although other measures, including the first orbital spaceflight (1957) and release of animals to space, were done earlier [5]. Nowadays in medicine and biology, Yuri Gagarin is a gene in *Drosophila* which

In the USA, the National Advisory Committee for Aeronautics (NACA) became

The first human who landed and walked on the Moon on July 20, 1969, was Neil Armstrong (1930–2012, American astronaut and commander of the Apollo 11). His

The deployment of ISS in the low Earth orbit (LEO) was carried out to rotate the human body around the Earth at the height of about 400 km; then another great mission was performed. Ninety percent of gravity at ground level will be endured

So far, about 90 astronauts have arrived at the ISS, with an average length of stay of about 6 months (6). The Apollo program included human missions and spaceflights above LEO. The program ended in 1972. During this program, 12 astronauts

The Chinese are trying hard to build their space station which will be built

Astronauts are preparing to travel to Mars now. Two and a half years are considered for this mission, part of it for spaceflight and the remaining for settlement and

If the astronauts reach Mars with a weak and inadequate physical condition, having no solution to perform their basic tasks, the mission will face serious risks and will almost fail. Astronauts will endanger greater risks by sensory-motor impairment during spaceship control, off-vessel operations, or remote-controlled tasks. As long as the problems caused by weightlessness were not solved successfully, it is not wise to consider the long-term human journeys and missions like going to Mars [9]. Nowadays, human exploration missions to the Moon or Mars are considered as the next logical steps in the space era. In some cases, even human dispatch and

They are exposed to weightlessness in their 6-month course, which seems to make them physically very disable and inefficient at the end of the flight [7]. Most astronauts will encounter problems in spatial orientation and balance during the first few days after landing. They will be at risk for fractures and muscle

In a long space trip, including a trip to Mars, astronauts are exposed to large amounts of radiation which is much higher than the magnitude permitted by the

affect the future of long-term space travels and would limit them [12].

**66**

migration, and colonization in other worlds, have also been announced. Almost all major national and international organizations in the world, as well as private investors and business plans, are currently developing roadmaps and related technologies to bring a healthy human to other planets of the solar system. Gradually, it seems that mankind is going to imagine about frequent and extended space trips, so that interplanetary traveling is equivalent to the concept of intercontinental flights. The human spaceflight perspective looks at the following to achieve in a short period:


Many different challenges would be encountered that scientists and also politicians should overcome [9].

Most of the medical challenges that were faced during humanitarian missions and related steps were mainly due to radiation and effects of microgravity (or hypogravity) as well as psychological issues [8]. In future exploratory missions for the Moon and Mars, the crew will be exposed to problems of the permanent base establishment on the planet, long-duration flights and missions, radiation intensity, microgravity, and the different impressions of constraints and isolation. It poses several health issues that may be a limiting factor during these missions. The health and performance of the crew should be ensured during journeys on the transfer and discovery of the planet's surface, external vehicle activities, and after returning to the Earth. In particular, the mission to Mars includes more challenges: the planet's distance, travel time (at least 500 days), and the impossibility of suspending the missions that necessitates an entirely stable mission. There could not be any support from the Earth in the major health problem or technical one [9].
