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Spaceflight (also written space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, " " (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.

Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper "A Method of Reaching Extreme Altitudes". His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space[specify]; nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany.

Nonetheless, Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler . Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]

Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]

At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.

Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.

A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.

A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles.

The most commonly used definition of outer space is everything beyond the Krmn line, which is 100 kilometers (62mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80km) in altitude.

Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.

For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of catastrophic failures.

Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.

However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.

Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171km by 169km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.

Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.

Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.

Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.

Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.

Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.

The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]

Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle and the heat energy instead ends up in the atmosphere.

The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively slow speeds. Russian capsules for Soyuz make use of braking rockets as were designed to touch down on land. The Space Shuttle and Buran glide to a touchdown at high speed.

After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.

Unmanned spaceflight is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Unmanned spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of unmanned spaceflight are robotic spacecraft (objects) and robotic space missions (activities). A robotic spacecraft is a unmanned spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.

Unmanned space missions use remote-controlled spacecraft. The first unmanned space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where animals but no humans are on-board are considered unmanned missions.

Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.

Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400 ms round trip delays which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]

The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] The international rules for aviation records stated that "The pilot remains in his craft from launch to landing".[citation needed] This rule, if applied, would have "disqualified" Gagarin's spaceflight. Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.

On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746mi) before reentering the Earth's atmosphere 43 hours after launch.

The most generally recognized boundary of space is the Krmn line 100km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Krmn line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Krmn line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.

Point-to-point sub-orbital spaceflight is a category of spaceflight in which a spacecraft uses a sub-orbital flight for transportation. This can provide a two-hour trip from London to Sydney, which would be much faster than what is currently over a twenty-hour flight. Today, no company offers this type of spaceflight for transportation. However, Virgin Galactic has plans for a spaceplane called SpaceShipThree, which could offer this service in the future.[10] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[11] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.

A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.

Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.

Five spacecraft are currently leaving the Solar System on escape trajectories. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[12] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.

Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.

Spacecraft are vehicles capable of controlling their trajectory through space.

The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[13] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.

Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.

Launch systems are used to carry a payload from Earth's surface into outer space.

All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16km) away being broken by the blast.[15]

Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.

In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[16]

In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.

Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[17]

In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[18] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.

Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[19]

Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.

Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.

In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.

Current and proposed applications for spaceflight include:

Most early spaceflight development was paid for by governments. However, today major launch markets such as Communication satellites and Satellite television are purely commercial, though many of the launchers were originally funded by governments.

Private spaceflight is a rapidly developing area: space flight that is not only paid for by corporations or even private individuals, but often provided by private spaceflight companies. These companies often assert that much of the previous high cost of access to space was caused by governmental inefficiencies they can avoid. This assertion can be supported by much lower published launch costs for private space launch vehicles such as Falcon 9 developed with private financing. Lower launch costs and excellent safety will be required for the applications such as Space tourism and especially Space colonization to become successful.

Media related to Spaceflight at Wikimedia Commons

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Spaceflight - Wikipedia, the free encyclopedia

A few hundred years ago, traveling over the Earths surface was a risky adventure. Early explorers who set out to explore the New World went by boat, enduring fierce storms, disease and hunger, to reach their destinations. Today, astronauts exploring space face similar challenges.

All About Space Travel: One space shuttle launch costs $450 million

Space travel has become much safer as scientists have overcome potential problems, but its still dangerous. Its also very expensive. In order for a space shuttle to break free of Earths gravity, it has to travel at a speed of 15,000 miles per hour. Space shuttles need 1.9 million liters of fuel just to launch into space. Thats enough fuel to fill up 42,000 cars! Combine the high speed, heat and fuel needed for launching and youve got a very potentially dangerous situation.

In 1949, Albert II, a Rhesus monkey went to space. Keep reading to find out more all about space travel.

Re-entering the atmosphere is dangerous too. When a space craft re-enters the atmosphere, it is moving very fast. As it moves through the air, friction causes it to heat up to a temperature of 2,691 degrees. The first spacecrafts were destroyed during re-entry. Todays space shuttles have special ceramic tiles that help absorb some of the heat, keeping the astronauts safe during re-entry.

In 1957, the Russian space dog, Laika, orbited the Earth.

In 1959, the Russian space craft, Luna 2, landed on the moon. It crashed at high speed.

Russian astronaut, Yuri Gagarin, was the first human in space. He orbited the Earth in 1961.

On July 20, 1969, Neil Armstrong and Buzz Aldrin became the first men to walk on the moon and return home safely a journey of 250,000 miles.

Check out this cool video all about space travel:

A video about the N.E.X.T. mission for space travel by NASA.

Enjoyed the Easy Science for Kids Website all about Space Travel info? Take the FREE & fun all about Space Travel quiz and download FREE Space Travel worksheet for kids. For lengthy info click here.

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Space Travel Facts for Kids

Human spaceflight (also referred to as manned spaceflight) is space travel with a crew or passengers aboard the spacecraft. Spacecraft carrying people may be operated directly, by human crew, or it may be either remotely operated from ground stations on Earth or be autonomous, able to carry out a specific mission with no human involvement.

The first human spaceflight was launched by the Soviet Union on 12 April 1961 as a part of the Vostok program, with cosmonaut Yuri Gagarin aboard. Humans have been continually present in space for 700849902926700000015years and 297days on the International Space Station. All early human spaceflight was crewed, where at least some of the passengers acted to carry out tasks of piloting or operating the spacecraft. After 2015, several human-capable spacecraft are being explicitly designed with the ability to operate autonomously.

Since the retirement of the US Space Shuttle in 2011, only Russia and China have maintained human spaceflight capability with the Soyuz program and Shenzhou program. Currently, all expeditions to the International Space Station use Soyuz vehicles, which remain attached to the station to allow quick return if needed. The United States is developing commercial crew transportation to facilitate domestic access to ISS and low Earth orbit, as well as the Orion vehicle for beyond-low Earth orbit applications.

While spaceflight has typically been a government-directed activity, commercial spaceflight has gradually been taking on a greater role. The first private human spaceflight took place on 21 June 2004, when SpaceShipOne conducted a suborbital flight, and a number of non-governmental companies have been working to develop a space tourism industry. NASA has also played a role to stimulate private spaceflight through programs such as Commercial Orbital Transportation Services (COTS) and Commercial Crew Development (CCDev). With its 2011 budget proposals released in 2010,[1] the Obama administration moved towards a model where commercial companies would supply NASA with transportation services of both people and cargo transport to low Earth orbit. The vehicles used for these services could then serve both NASA and potential commercial customers. Commercial resupply of ISS began two years after the retirement of the Shuttle, and commercial crew launches could begin by 2017.[2]

Human spaceflight capability was first developed during the Cold War between the United States and the Soviet Union (USSR), which developed the first intercontinental ballistic missile rockets to deliver nuclear weapons. These rockets were large enough to be adapted to carry the first artificial satellites into low Earth orbit. After the first satellites were launched in 1957 and 1958, the US worked on Project Mercury to launch men singly into orbit, while the USSR secretly pursued the Vostok program to accomplish the same thing. The USSR launched the first human in space, Yuri Gagarin into a single orbit in Vostok 1 on a Vostok 3KA rocket, on April 12, 1961. The US launched its first astronaut, Alan Shepard on a suborbital flight aboard Freedom 7 on a Mercury-Redstone rocket, on May 5, 1961. Unlike Gagarin, Shepard manually controlled his spacecraft's attitude, and landed inside it. The first American in orbit was John Glenn aboard Friendship 7, launched February 20, 1962 on a Mercury-Atlas rocket. The USSR launched five more cosmonauts in Vostok capsules, including the first woman in space, Valentina Tereshkova aboard Vostok 6 on June 16, 1963. The US launched a total of two astronauts in suborbital flight and four in orbit through 1963.

US President John F. Kennedy raised the stakes of the Space Race by setting the goal of landing a man on the Moon and returning him safely by the end of the 1960s.[3] The US started the three-man Apollo program in 1961 to accomplish this, launched by the Saturn family of launch vehicles, and the interim two-man Project Gemini in 1962, which flew 10 missions launched by Titan II rockets in 1965 and 1966. Gemini's objective was to support Apollo by developing American orbital spaceflight experience and techniques to be used in the Moon mission.[4]

Meanwhile, the USSR remained silent about their intentions to send humans to the Moon, and proceeded to stretch the limits of their single-pilot Vostok capsule into a two- or three-person Voskhod capsule to compete with Gemini. They were able to launch two orbital flights in 1964 and 1965 and achieved the first spacewalk, made by Alexei Leonov on Voskhod 2 on March 8, 1965. But Voskhod did not have Gemini's capability to maneuver in orbit, and the program was terminated. The US Gemini flights did not accomplish the first spacewalk, but overcame the early Soviet lead by performing several spacewalks and solving the problem of astronaut fatigue caused by overcoming the lack of gravity, demonstrating up to two weeks endurance in a human spaceflight, and the first space rendezvous and dockings of spacecraft.

The US succeeded in developing the Saturn V rocket necessary to send the Apollo spacecraft to the Moon, and sent Frank Borman, James Lovell, and William Anders into 10 orbits around the Moon in Apollo 8 in December 1968. In July 1969, Apollo 11 accomplished Kennedy's goal by landing Neil Armstrong and Buzz Aldrin on the Moon July 21 and returning them safely on July 24 along with Command Module pilot Michael Collins. A total of six Apollo missions landed 12 men to walk on the Moon through 1972, half of which drove electric powered vehicles on the surface. The crew of Apollo 13, Lovell, Jack Swigert, and Fred Haise, survived a catastrophic in-flight spacecraft failure and returned to Earth safely without landing on the Moon.

Meanwhile, the USSR secretly pursued human lunar lunar orbiting and landing programs. They successfully developed the three-person Soyuz spacecraft for use in the lunar programs, but failed to develop the N1 rocket necessary for a human landing, and discontinued the lunar programs in 1974.[5] On losing the Moon race, they concentrated on the development of space stations, using the Soyuz as a ferry to take cosmonauts to and from the stations. They started with a series of Salyut sortie stations from 1971 to 1986.

After the Apollo program, the US launched the Skylab sortie space station in 1973, manning it for 171 days with three crews aboard Apollo spacecraft. President Richard Nixon and Soviet Premier Leonid Brezhnev negotiated an easing of relations known as dtente, an easing of Cold War tensions. As part of this, they negotiated the Apollo-Soyuz Test Project, in which an Apollo spacecraft carrying a special docking adapter module rendezvoused and docked with Soyuz 19 in 1975. The American and Russian crews shook hands in space, but the purpose of the flight was purely diplomatic and symbolic.

Nixon appointed his Vice President Spiro Agnew to head a Space Task Group in 1969 to recommend follow-on human spaceflight programs after Apollo. The group proposed an ambitious Space Transportation System based on a reusable Space Shuttle which consisted of a winged, internally fueled orbiter stage burning liquid hydrogen, launched by a similar, but larger kerosene-fueled booster stage, each equipped with airbreathing jet engines for powered return to a runway at the Kennedy Space Center launch site. Other components of the system included a permanent modular space station, reusable space tug and nuclear interplanetary ferry, leading to a human expedition to Mars as early as 1986, or as late as 2000, depending on the level of funding allocated. However, Nixon knew the American political climate would not support Congressional funding for such an ambition, and killed proposals for all but the Shuttle, possibly to be followed by the space station. Plans for the Shuttle were scaled back to reduce development risk, cost, and time, replacing the piloted flyback booster with two reusable solid rocket boosters, and the smaller orbiter would use an expendable external propellant tank to feed its hydrogen-fueled main engines. The orbiter would have to make unpowered landings.

The two nations continued to compete rather than cooperate in space, as the US turned to developing the Space Shuttle and planning the space station, dubbed Freedom. The USSR launched three Almaz military sortie stations from 1973 to 1977, disguised as Salyuts. They followed Salyut with the development of Mir, the first modular, semi-permanent space station, the construction of which took place from 1986 to 1996. Mir orbited at an altitude of 354 kilometers (191 nautical miles), at a 51.6 inclination. It was occupied for 4,592 days, and made a controlled reentry in 2001.

The Space Shuttle started flying in 1981, but the US Congress failed to approve sufficient funds to make Freedom a reality. A fleet of four shuttles was built: Columbia, Challenger, Discovery, and Atlantis. A fifth shuttle, Endeavour, was built to replace Challenger which was destroyed in an accident during launch which killed 7 astronauts on January 28, 1986. Twenty-two Shuttle flights carried a European Space Agency sortie space station called Spacelab in the payload bay from 1983 to 1998.[6]

The USSR copied the reusable Space Shuttle orbiter, which it called Buran. It was designed to be launched into orbit by the expendable Energia rocket, and capable of robotic orbital flight and landing. Unlike the US Shuttle, Buran had no main rocket engines, but used its orbital maneuvering engines to insert itself into orbit; but it had airbreathing jet engines for powered landings. A single unmanned orbital test flight was successfully made in November 1988. A second test flight was planned by 1993, but the program was cancelled due to lack of funding and the dissolution of the Soviet Union in 1991. Two more orbiters were never completed, and the first one was destroyed in a hangar roof collapse in May 2002.

The dissolution of the Soviet Union in 1991 brought an end to the Cold War and opened the door to true cooperation between the US and Russia. The Soviet Soyuz and Mir programs were taken over by the Russian Federal Space Agency, now known as the Roscosmos State Corporation. The Shuttle-Mir Program included American Space Shuttles visiting the Mir space station, Russian cosmonauts flying on the Shuttle, and an American astronaut flying aboard a Soyuz spacecraft for long-duration expeditions aboard Mir.

In 1993, President Bill Clinton secured Russia's cooperation in converting the planned Space Station Freedom into the International Space Station (ISS). Construction of the station began in 1998. The station orbits at an altitude of 409 kilometers (221nmi) and an inclination of 51.65.

The Space Shuttle was retired in 2011 after 135 orbital flights, several of which helped assemble, supply, and crew the ISS. Columbia was destroyed in another accident during reentry, which killed 7 astronauts on February 1, 2003.

After Russia's launch of Sputnik 1 in 1957, Chairman Mao Zedong intended to place a Chinese satellite in orbit by 1959 to celebrate the 10th anniversary of the founding of the People's Republic of China (PRC),[7] However, China did not successfully launch its first satellite until April 24, 1970. Mao and Premier Zhou Enlai decided on July 14, 1967, that the PRC should not be left behind, and started China's own human spaceflight program.[8] The first attempt, the Shuguang spacecraft copied from the US Gemini, was cancelled on May 13, 1972.

China later designed the Shenzhou spacecraft resembling the Russian Soyuz, and became the third nation to achieve independent human spaceflight capability by launching Yang Liwei on a 21-hour flight aboard Shenzhou 5 on October 15, 2003. China launched the Tiangong-1 space station on September 29, 2011, and two sortie missions to it: Shenzhou 9 June 1629, 2012, with China's first female astronaut Liu Yang; and Shenzhou 10, June 1326, 2013.

The European Space Agency began development in 1987 of the Hermes spaceplane, to be launched on the Ariane 5 expendable launch vehicle. The project was cancelled in 1992, when it became clear that neither cost nor performance goals could be achieved. No Hermes shuttles were ever built.

Japan began development in the 1980s of the HOPE-X experimental spaceplane, to be launched on its H-IIA expendable launch vehicle. A string of failures in 1998 led to funding reduction, and the project's cancellation in 2003.

Under the Bush administration, the Constellation Program included plans for retiring the Shuttle program and replacing it with the capability for spaceflight beyond low Earth orbit. In the 2011 United States federal budget, the Obama administration cancelled Constellation for being over budget and behind schedule while not innovating and investing in critical new technologies.[9] For beyond low earth orbit human spaceflight NASA is developing the Orion spacecraft to be launched by the Space Launch System. Under the Commercial Crew Development plan, NASA will rely on transportation services provided by the private sector to reach low earth orbit, such as Space X's Falcon 9/Dragon V2, Sierra Nevada Corporation's Dream Chaser, or Boeing's CST-100. The period between the retirement of the shuttle in 2011 and the initial operational capability of new systems in 2017, similar to the gap between the end of Apollo in 1975 and the first space shuttle flight in 1981, is referred to by a presidential Blue Ribbon Committee as the U.S. human spaceflight gap.[10]

After the early 2000s, a variety of private spaceflight ventures were undertaken. Several of the companies formed by 2005, including Blue Origin, SpaceX, Virgin Galactic, and XCOR Aerospace have explicit plans to advance human spaceflight. As of 2015[update], all four of those companies have development programs underway to fly commercial passengers before 2018.

Commercial suborbital spacecraft aimed at the space tourism market include Virgin Galactic SpaceshipTwo, and XCOR's Lynx spaceplane which are both under development and could reach space before 2017.[11] More recently, Blue Origin has begun a multi-year test program of their New Shepardvehicle with plans to test in 20152016 while carrying no passengers, then adding "test passengers" in 2017, and initiate commercial flights in 2018.[12][13]

SpaceX and Boeing are both developing passenger-capable orbital space capsules as of 2015, planning to fly NASA astronauts to the International Space Station as soon as 2018. SpaceX will be carrying passengers on Dragon 2 launched on a Falcon 9 launch vehicle. Boeing will be doing it with their CST-100 launched on a United Launch Alliance Atlas V launch vehicle.[14] Development funding for these orbital-capable technologies has been provided by a mix of government and private funds, with SpaceX providing a greater portion of total development funding for this human-carrying capability from private investment.[15][16] There have been no public announcements of commercial offerings for orbital flights from either company, although both companies are planning some flights with their own private, not NASA, astronauts on board.

Svetlana Savitskaya became the first woman to walk in space on 25 July 1984.

Sally Ride became the first American woman in space in 1983. Eileen Collins was the first female shuttle pilot, and with shuttle mission STS-93 in 1999 she became the first woman to command a U.S. spacecraft.

The longest single human spaceflight is that of Valeri Polyakov, who left Earth on 8 January 1994, and did not return until 22 March 1995 (a total of 437 days 17 h 58 min 16 s). Sergei Krikalyov has spent the most time of anyone in space, 803 days, 9 hours, and 39 minutes altogether. The longest period of continuous human presence in space is 700849902926700000015years and 297days on the International Space Station, exceeding the previous record of almost 10 years (or 3,634 days) held by Mir, spanning the launch of Soyuz TM-8 on 5 September 1989 to the landing of Soyuz TM-29 on 28 August 1999.

For many years, only the USSR (later Russia) and the United States had their own astronauts. Citizens of other nations flew in space, beginning with the flight of Vladimir Remek, a Czech, on a Soviet spacecraft on 2 March 1978, in the Interkosmos programme. As of 2010[update], citizens from 38 nations (including space tourists) have flown in space aboard Soviet, American, Russian, and Chinese spacecraft.

Human spaceflight programs have been conducted by the former Soviet Union and current Russian Federation, the United States, the People's Republic of China and by private spaceflight company Scaled Composites.

Space vehicles are spacecraft used for transportation between the Earth's surface and outer space, or between locations in outer space. The following space vehicles and spaceports are currently used for launching human spaceflights:

The following space stations are currently maintained in Earth orbit for human occupation:

Numerous private companies attempted human spaceflight programs in an effort to win the $10 million Ansari X Prize. The first private human spaceflight took place on 21 June 2004, when SpaceShipOne conducted a suborbital flight. SpaceShipOne captured the prize on 4 October 2004, when it accomplished two consecutive flights within one week. SpaceShipTwo, launching from the carrier aircraft White Knight Two, is planned to conduct regular suborbital space tourism.[17]

Most of the time, the only humans in space are those aboard the ISS, whose crew of six spends up to six months at a time in low Earth orbit.

NASA and ESA use the term "human spaceflight" to refer to their programs of launching people into space. These endeavors have also been referred to as "manned space missions," though because of gender specificity this is no longer official parlance according to NASA style guides.[18]

The Indian Space Research Organisation (ISRO) has begun work on pre-project activities of a human space flight mission program.[19] The objective is to carry a crew of two to Low Earth Orbit (LEO) and return them safely to a predefined destination on Earth. The program is proposed to be implemented in defined phases. Currently, the pre-project activities are progressing with a focus on the development of critical technologies for subsystems such as the Crew Module (CM), Environmental Control and Life Support System (ECLSS), Crew Escape System, etc. The department has initiated pre-project activities to study technical and managerial issues related to crewed missions. The program envisages the development of a fully autonomous orbital vehicle carrying 2 or 3 crew members to about 300km low earth orbit and their safe return.

The United States National Aeronautics and Space Administration (NASA) is developing a plan to land humans on Mars by the 2030s. The first step in this mission begins sometime during 2020, when NASA plans to send an unmanned craft into deep space to retrieve an asteroid.[20] The asteroid will be pushed into the moons orbit, and studied by astronauts aboard Orion, NASAs first human spacecraft in a generation.[21] Orions crew will return to Earth with samples of the asteroid and their collected data. In addition to broadening Americas space capabilities, this mission will test newly developed technology, such as solar electric propulsion, which uses solar arrays for energy and requires ten times less propellant than the conventional chemical counterpart used for powering space shuttles to orbit.[22]

Several other countries and space agencies have announced and begun human spaceflight programs by their own technology, Japan (JAXA), Iran (ISA) and Malaysia (MNSA).

There are two main sources of hazard in space flight: those due to the environment of space which make it hostile to the human body, and the potential for mechanical malfunctions of the equipment required to accomplish space flight.

Planners of human spaceflight missions face a number of safety concerns.

The immediate needs for breathable air and drinkable water are addressed by the life support system of the spacecraft.

Medical consequences such as possible blindness and bone loss have been associated with human space flight.[32][33]

On 31 December 2012, a NASA-supported study reported that spaceflight may harm the brain of astronauts and accelerate the onset of Alzheimer's disease.[34][35][36]

In October 2015, the NASA Office of Inspector General issued a health hazards report related to space exploration, including a human mission to Mars.[37][38]

Medical data from astronauts in low earth orbits for long periods, dating back to the 1970s, show several adverse effects of a microgravity environment: loss of bone density, decreased muscle strength and endurance, postural instability, and reductions in aerobic capacity. Over time these deconditioning effects can impair astronauts performance or increase their risk of injury.[39]

In a weightless environment, astronauts put almost no weight on the back muscles or leg muscles used for standing up, which causes them to weaken and get smaller. Astronauts can lose up to twenty per cent of their muscle mass on spaceflights lasting five to eleven days. The consequent loss of strength could be a serious problem in case of a landing emergency.[40] Upon return to Earth from long-duration flights, astronauts are considerably weakened, and are not allowed to drive a car for twenty-one days.[41]

Astronauts experiencing weightlessness will often lose their orientation, get motion sickness, and lose their sense of direction as their bodies try to get used to a weightless environment. When they get back to Earth, or any other mass with gravity, they have to readjust to the gravity and may have problems standing up, focusing their gaze, walking and turning. Importantly, those body motor disturbances after changing from different gravities only get worse the longer the exposure to little gravity.[citation needed] These changes will affect operational activities including approach and landing, docking, remote manipulation, and emergencies that may happen while landing. This can be a major roadblock to mission success.[citation needed]

In addition, after long space flight missions, male astronauts may experience severe eyesight problems.[42][43][44][45][46] Such eyesight problems may be a major concern for future deep space flight missions, including a crewed mission to the planet Mars.[42][43][44][45][47]

Without proper shielding, the crews of missions beyond low Earth orbit (LEO) might be at risk from high-energy protons emitted by solar flares. Lawrence Townsend of the University of Tennessee and others have studied the most powerful solar flare ever recorded. That flare was seen by the British astronomer Richard Carrington in September 1859. Radiation doses astronauts would receive from a Carrington-type flare could cause acute radiation sickness and possibly even death.[49]

Another type of radiation, galactic cosmic rays, presents further challenges to human spaceflight beyond low Earth orbit.[50]

There is also some scientific concern that extended spaceflight might slow down the bodys ability to protect itself against diseases.[51] Some of the problems are a weakened immune system and the activation of dormant viruses in the body. Radiation can cause both short and long term consequences to the bone marrow stem cells which create the blood and immune systems. Because the interior of a spacecraft is so small, a weakened immune system and more active viruses in the body can lead to a fast spread of infection.[citation needed]

During long missions, astronauts are isolated and confined into small spaces. Depression, cabin fever and other psychological problems may impact the crew's safety and mission success.[citation needed]

Astronauts may not be able to quickly return to Earth or receive medical supplies, equipment or personnel if a medical emergency occurs. The astronauts may have to rely for long periods on their limited existing resources and medical advice from the ground.

Space flight requires much higher velocities than ground or air transportation, which in turn requires the use of high energy density propellants for launch, and the dissipation of large amounts of energy, usually as heat, for safe reentry through the Earth's atmosphere.

Since rockets carry the potential for fire or explosive destruction, space capsules generally employ some sort of launch escape system, consisting either of a tower-mounted solid fuel rocket to quickly carry the capsule away from the launch vehicle (employed on Mercury, Apollo, and Soyuz), or else ejection seats (employed on Vostok and Gemini) to carry astronauts out of the capsule and away for individual parachute landing. The escape tower is discarded at some point before the launch is complete, at a point where an abort can be performed using the spacecraft's engines.

Such a system is not always practical for multiple crew member vehicles (particularly spaceplanes), depending on location of egress hatch(es). When the single-hatch Vostok capsule was modified to become the 2 or 3-person Voskhod, the single-cosmonaut ejection seat could not be used, and no escape tower system was added. The two Voskhod flights in 1964 and 1965 avoided launch mishaps. The Space Shuttle carried ejection seats and escape hatches for its pilot and copilot in early flights, but these could not be used for passengers who sat below the flight deck on later flights, and so were discontinued.

The only in-flight launch abort of a crewed flight occurred on Soyuz 18a on April 5, 1975. The abort occurred after the launch escape system had been jettisoned, when the launch vehicle's spent second stage failed to separate before the third stage ignited. The vehicle strayed off course, and the crew separated the spacecraft and fired its engines to pull it away from the errant rocket. Both cosmonauts landed safely.

In the only use of a launch escape system on a crewed flight, the planned Soyuz T-10a launch on September 26, 1983 was aborted by a launch vehicle fire 90 seconds before liftoff. Both cosmonauts aboard landed safely.

The only crew fatality during launch occurred on January 28, 1986, when the Space Shuttle Challenger broke apart 73 seconds after liftoff, due to failure of a solid rocket booster seal which caused separation of the booster and failure of the external fuel tank, resulting in explosion of the fuel. All seven crew members were killed.

The single pilot of Soyuz 1, Vladimir Komarov was killed when his capsule's parachutes failed during an emergency landing on April 24, 1967, causing the capsule to crash.

The crew of seven aboard the Space Shuttle Columbia were killed on reentry after completing a successful mission in space on February 1, 2003. A wing leading edge reinforced carbon-carbon heat shield had been damaged by a piece of frozen external tank foam insulation which broke off and struck the wing during launch. Hot reentry gasses entered and destroyed the wing structure, leading to breakup of the orbiter vehicle.

There are two basic choices for an artificial atmosphere: either an Earth-like mixture of oxygen in an inert gas such as nitrogen or helium, or pure oxygen, which can be used at lower than standard atmospheric pressure. A nitrogen-oxygen mixture is used in the International Space Station and Soyuz spacecraft, while low-pressure pure oxygen is commonly used in space suits for extravehicular activity.

Use of a gas mixture carries risk of decompression sickness (commonly known as "the bends") when transitioning to or from the pure oxygen space suit environment. There have also been instances of injury and fatalities caused by suffocation in the presence of too much nitrogen and not enough oxygen.

A pure oxygen atmosphere carries risk of fire. The original design of the Apollo spacecraft used pure oxygen at greater than atmospheric pressure prior to launch. An electrical fire started in the cabin of Apollo 1 during a ground test at Cape Kennedy Air Force Station Launch Complex 34 on January 27, 1967, and spread rapidly. The high pressure (increased even higher by the fire) prevented removal of the plug door hatch cover in time to rescue the crew. All three, Gus Grissom, Edward H. White, and Roger Chaffee, were killed.[55] This led NASA to use a nitrogen/oxygen atmosphere before launch, and low pressure pure oxygen only in space.

The March 1966 Gemini 8 mission was aborted in orbit when an attitude control system thruster stuck in the on position, sending the craft into a dangerous spin which threatened the lives of Neil Armstrong and David Scott. Armstrong had to shut the control system off and use the reentry control system to stop the spin. The craft made an emergency reentry and the astronauts landed safely. The most probable cause was determined to be an electrical short due to a static electricity discharge, which caused the thruster to remain powered even when switched off. The control system was modified to put each thruster on its own isolated circuit.

The third lunar landing expedition Apollo 13 in April 1970, was aborted and the lives of the crew, James Lovell, Jack Swigert and Fred Haise, were threatened by failure of a cryogenic liquid oxygen tank en route to the Moon. The tank burst when electrical power was applied to internal stirring fans in the tank, causing the immediate loss of all of its contents, and also damaging the second tank, causing the loss of its remaining oxygen in a span of 130 minutes. This in turn caused loss of electrical power provided by fuel cells to the command spacecraft. The crew managed to return to Earth safely by using the lunar landing craft as a "life boat". The tank failure was determined to be caused by two mistakes. The tank's drain fitting had been damaged when it was dropped during factory testing. This necessitated use of its internal heaters to boil out the oxygen after a pre-launch test, which in turn damaged the fan wiring's electrical insulation, because the thermostats on the heaters did not meet the required voltage rating due to a vendor miscommunication.

As of December 2015[update], 22 crew members have died in accidents aboard spacecraft. Over 100 others have died in accidents during activity directly related to spaceflight or testing.

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Human spaceflight - Wikipedia, the free encyclopedia

Space-A travel is a means by which members of United States Uniformed Services (United States Military, reservists and retirees, United States Department of Defense civilian personnel (under certain circumstances), and these groups' family members, are permitted to travel on aircraft under the jurisdiction of the United States Department of Defense when excess capability allows.

Space available travel is a privilege that derives, in part, from United States Code, title 10, section 4744, which states, "officers and members of the Military Departments, and their families, when space is available, may be transported on vessels operated by any military transport agency of the Department of Defense". Space available travel is defined as "travel aboard DoD owned or controlled aircraft and occurs when aircraft are not fully booked with passengers traveling under orders".

It is a privilege offered to United States Uniformed Services members. Retired members are given the privilege in recognition of their career and because they are eligible for recall to active duty. The criteria for extending the privilege to other categories of passengers is their support to the mission being performed by Uniformed Services members and to the enhancement of active duty Service members' quality of life.

There are rules and guidelines which apply to such travel. Uniformed personnel may only travel Space-A while on leave or pass for the full duration of their Space-A trip, and Space-A travel can not be used in conjunction with travel required by the service. Space A travel may not be used for personal financial gain or in connection with business enterprises or employment. Other nations' laws and policies, as well as U.S. foreign policy, may limit the ability to travel using Space-A.

Aside from members of the United States Marine Corps, travelers do not have to be in uniform for their flights.

Eligible passengers wanting to travel using DoD Space-A travel are required to sign up at the departing location and are then placed on a locally managed Space-A register. The registration process varies depending on the location, but most locations allow signups via electronic mail, fax, or postal mail.

Each location's passenger service center maintains their own Space-A register. Each person signing up is placed on this register using category of travel, signup date and signup time.

Based on status (active duty military, retired military, emergency traveler, etc.), Space-A travel applicants are assigned a category of travel from 1 to 6, which categorizes their priority of movement, 1 being the highest priority. Thus, an applicant with priority 1 will gain a place on an available aircraft over an applicant with priority 4, for example.

The number of space-available seats may not be known until the flight's "Roll Call" just prior to the flight departs. After sorting the signup register by category of travel and signup date, the passenger terminal personnel follow a selection procedure. If there is sufficient seating for everyone desiring a seat, then everyone boards; otherwise, a cutoff point is determined.

The branches of service eligible for Space-A travel are:

Space-A travel is not without its pitfalls. Unlike traditional commercial air traffic, military flights are not always assigned predictable takeoff times. Many factors go into planning a military flight, with space-required cargo and passengers forming the basis of planning. There is no consideration given to potential Space-A travelers during the planning process.

The majority of flights that passengers take occur on: C-5, C-17, C-40, C-130, KC-10, and KC-135 aircraft.

Space-A travelers might meet abrupt, sometimes even in-flight, changes in travel. This need for pre-planning has given rise to a small industry surrounding such travel. Non-governmental enterprises (for the most part, publishers) produce products, initially through books and maps, with more recent incarnations as websites which provide travelers with information regarding Space-A travel.

The following information Space-A links are hosted by volunteer retired military:

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Space-A travel - Wikipedia, the free encyclopedia