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Spaceflight (or space flight) is an application of astronautics to fly objects, usually spacecraft, into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as in Geocentric orbit, but also includes for flights beyond Earth orbit. Such spaceflights operate either by telerobotic or Autonomous robot control. The first spaceflights began in the 1950s with the launches of the Soviet Sputnik program satellites and American Explorer and Project Vanguard missions. Human spaceflight programs include the Soyuz programme, Shenzhou, the past Apollo program and the Space Shuttle programs. Other current spaceflight are conducted to the International Space Station and to China's Tiangong Space Station.
Spaceflights include the launches of Earth observation and telecommunications satellites, interplanetary missions, the rendezvouses and dockings with , and crewed spaceflights on Space science or Space tourism missions.
Spaceflight can be achieved conventionally via multistage rockets, which provide the thrust to overcome the force of gravity and propel spacecraft onto suborbital trajectories. If the mission is orbital, the spacecraft usually separates the first stage and ignites the second stage, which propels the spacecraft to high enough speeds that it reaches orbit. Once in orbit, spacecraft are at high enough speeds that they fall around the Earth rather than fall back to the surface.
Most spacecraft, and all crewed spacecraft, are designed to deorbit themselves or, in the case of uncrewed spacecraft in high-energy orbits, to boost themselves into . Used upper stages or failed spacecraft, however, often lack the ability to deorbit themselves. This becomes a major issue when large numbers of uncontrollable spacecraft exist in frequently used orbits, increasing the risk of Space debris colliding with functional satellites. This problem is exacerbated when large objects, often upper stages, break up in orbit or collide with other objects, creating often hundreds of small, hard to find pieces of debris. This problem of continuous collisions is known as Kessler syndrome.
A space mission refers to a spaceflight intended to achieve an objective. Objectives for space missions may include space exploration, space research, and national firsts in spaceflight.
Space transport is the use of spacecraft to transport people or cargo into or through outer space. This may include human spaceflight and cargo spacecraft flight.
Where:
This equation, known as the Tsiolkovsky rocket equation, can be used to find the total , or potential change in velocity. This formula, which is still used by engineers, is a key concept of spaceflight.
Spaceflight became a practical 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. After further research, Goddard attempted to secure an Army contract for a rocket-propelled weapon in the first World War but his plans were foiled by the November 11, 1918 armistice with Germany. After choosing to work with private financial support, he was the first to launch a liquid-fueled rocket on March 16, 1926.
During World War II, the first guided rocket, the V-2, was developed and employed as a weapon by Nazi Germany. During a test flight in June 1944, one such rocket reached space at an altitude of , becoming the first human-made object to reach space. At the end of World War II, most of the V-2 rocket team, including its head, Wernher von Braun, surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency, producing missiles such as Juno I and Atlas. The Soviet Union, in turn, captured several V2 production facilities and built several replicas, with 5 of their 11 rockets successfully reaching their targets. (This was relatively consistent with Nazi Germany's success rate.)
The Soviet Union developed intercontinental ballistic missiles to carry as a counter measure to United States bomber planes in the 1950s. The Tsiolkovsky-influenced Sergey Korolev became the chief rocket designer, and derivatives of his R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957.
The U.S., after the launch of Sputnik and two embarrassing failures of Vanguard rockets, launched Explorer 1 on February 1, 1958. Three years later, the USSR launched Vostok 1, carrying cosmonaut Yuri Gagarin into orbit. The US responded with the suborbital launch of Alan Shepard on May 5, 1961, and the orbital launch of John Glenn on February 20, 1962. These events were followed by a pledge from U.S. President John F. Kennedy to go to the moon and the creation of the Gemini program and Apollo program programs. After successfully performing a rendezvous and docking and an EVA, the Gemini program ended just before the Apollo 1 tragedy. Following multiple uncrewed test flights of the Saturn IB and the Saturn V, the U.S. launched the crewed Apollo 7 mission into low Earth orbit. Shortly after its successful completion, the U.S. launched Apollo 8 (first mission to orbit the Moon), Apollo 9 (first Apollo mission to launch with both the Apollo CSM and the LEM) and Apollo 10 (first mission to nearly land on the Moon). These events culminated with the first crewed Moon landing, Apollo 11, and six subsequent missions, five of which successfully landed on the Moon.
Spaceflight has been widely employed by numerous government and commercial entities for placing satellites into orbit around Earth for a broad range of purposes. Certain government agencies have also sent uncrewed spacecraft exploring space beyond the Moon and developed continuous crewed human presence in space with a series of , ranging from the Salyut program to the International Space Station.
A launch is often restricted to certain . 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. 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. Before launch, the rocket can weigh hundreds of tons. The Space Shuttle Columbia, on STS-1, weighed 2030 metric tons (4,480,000 lb) at takeoff.
Rocket engines remain the only currently practical means of reaching space, with planes and high-altitude balloons failing due to lack of atmosphere and alternatives such as space elevators not yet being built. Chemical propulsion, or the acceleration of gases at high velocities, is effective mainly because of its ability to sustain thrust even as the atmosphere thins.
Robotic missions do not require an abort capability and require radiation minimalization only for delicate electronics, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance by limiting the boil off of cryogenic propellants. 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.
The escape velocity from a celestial body decreases as the distance from the body increases. However, it is more fuel-efficient for a craft to burn its fuel as close as possible to its periapsis (lowest point); see Oberth effect. Escape Velocity of Earth . Van.physics.uiuc.edu. Retrieved on 2011-10-05.
Non-rocket orbital propulsion methods include , , plasma-bubble magnetic systems, and using gravitational slingshot effects.
After rendezvousing with the space station, the space vehicle then docks or berths with the station. Docking refers to joining of two separate free-flying space vehicles, while berthing refers to mating operations where an inactive vehicle is placed into the mating interface of another space vehicle by using a robotic arm.
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.
The most generally recognized boundary of space is the Kármán line above sea level. (NASA alternatively defines an astronaut as someone who has flown more than above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán 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 Kármán 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.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module, Apollo Expeditions to the Moon: Chapter 10. History.nasa.gov (1969-03-03). Retrieved on 2011-10-05. since this was the only crewed vehicle to have been designed for, and operated only in space; and is notable for its non-aerodynamic shape.
The first automatic partially reusable spacecraft was the Shuttle Buran ( Snowstorm), launched by the USSR on 15 November 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
The Space Shuttle was retired in 2011 due mainly to its old age. The Shuttle's human transport role is to be replaced by the SpaceX Dragon 2 and CST-100 in the 2020s. The Shuttle's heavy cargo transport role is now done by commercial launch vehicles.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourism) in 2008, but this was delayed due to an accident in the propulsion development. Launch aircraft development continues while suborbital ship awaits investigation into fatal explosion in California, retrieved 2012-01-27.
SpaceX achieved the first vertical soft landing of a reusable orbital rocket stage on December 21, 2015, after delivering 11 Orbcomm OG-2 commercial satellites into low Earth orbit.
The first Falcon 9 reflight occurred on 30 March 2017. SpaceX now routinely recovers and reuses their first stages and fairings. SpaceX is now developing a fully reusable super heavy lift rocket known as SpaceX Starship, with the goal of drastically reducing the price of space exploration. As of April 2025, three Super Heavy boosters, the first stage of Starship, have been recovered.
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 April 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.
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 onboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life-support systems for crewed spacecraft.
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.
Participation and representation of all humanity in spaceflight is an issue of international space law ever since the first phase of space exploration. Even though some rights of non-spacefaring countries have been secured, sharing of space for all humanity is still criticized as imperialism and lacking, understanding spaceflight as a resource.
The dominating issue about access in most recent years has been the issue of space debris and space sustainability, since established spacefaring countries endanger access to outer space with their orbital space polluting activity.
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 feasible for expansion.
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To be spacefaring is to be capable of and active in the operation of spacecraft. It involves a knowledge of a variety of topics and development of specialised skills including: aeronautics; astronautics; programs to train ; space weather and forecasting; spacecraft operations; operation of various equipment; spacecraft design and construction; atmospheric takeoff and reentry; orbital mechanics (a.k.a. astrodynamics); communications; engines and rockets; execution of evolutions such as towing, microgravity construction, and space docking; cargo handling equipment, dangerous cargos and cargo storage; ; dealing with emergencies; space survival and first aid; fire fighting; life support. The degree of knowledge needed within these areas is dependent upon the nature of the work and the type of vessel employed. "Spacefaring" is analogous to seafaring.
There has never been a crewed mission outside the Earth–Moon system. However, the United States, Russia, China, European Space Agency (ESA) countries, and a few corporations and enterprises have plans in various stages to travel to Mars (see Human mission to Mars).
Spacefaring entities can be , supranational entities, and private . Spacefaring nations are those capable of independently building and launching craft into space. A growing number of private entities have become or are becoming spacefaring.
Also several countries, such as Canada, Italy, and Australia, had semi-independent spacefaring capability, launching locally built satellites on foreign launchers. Canada had designed and built satellites ( Alouette 1 and 2) in 1962 and 1965 which were orbited using U.S. launch vehicles. Italy has designed and built several satellites, as well as pressurized modules for the International Space Station. Early Italian satellites were launched using vehicles provided by NASA, first from Wallops Flight Facility in 1964 and then from a spaceport in Kenya (San Marco Platform) between 1967 and 1988; Italy has led the development of the Vega rocket programme within the European Space Agency since 1998. The United Kingdom abandoned its independent space launch program in 1972 in favour of co-operating with the European Launcher Development Organisation (ELDO) on launch technologies until 1974. Australia abandoned its launcher program shortly after the successful launch of WRESAT, and became the only non-European member of ELDO.
Reentry
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 reaching the vehicle, and the remainder heats the atmosphere.
Landing and recovery
The Project Mercury, Project Gemini, and Apollo capsules Splashdown in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Soviet/Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. like the Space Shuttle land like a glider.
Types
Uncrewed
Human
The first human spaceflight was Vostok 1 on April 12, 1961, on which astronaut 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. Vostok 1. Astronautix.com. Retrieved on 2011-10-05. As of 2020, the only spacecraft regularly used for human spaceflight are Soyuz spacecraft, Shenzhou, and Crew Dragon. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted three human suborbital space flights.
Sub-orbital
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 before reentering the Earth's atmosphere 43 hours after launch.
Point-to-point
Point-to-point, or Earth to Earth transportation, is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations.
Orbital
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 orbit.
Interplanetary
Interplanetary spaceflight is flight between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of the Solar System. Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Constellation program and Russia's Kliper/Parom tandem.
Interstellar
New Horizons is the fifth spacecraft put on an escape trajectory leaving the Solar System. Voyager 1, Voyager 2, Pioneer 10, Pioneer 11 are the earlier ones. 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. 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. Dynamic soaring as a way to travel across interstellar space has been proposed as well.
Intergalactic
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. However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel is impossible. To date several academics have studied intergalactic travel in a serious manner.
Spacecraft
Spacecraft are vehicles designed to operate in space.
Propulsion
Spacecraft today predominantly use for propulsion, but other propulsion techniques such as are becoming more common, particularly for uncrewed vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on 19 July 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on 12 April 1981. During the Shuttle era, six orbiters were built, all of which flown in the atmosphere and five of which flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
Challenges
Safety
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 away being broken by the blast.
Weightlessness
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.
Radiation
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, 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. Super Spaceships , NASA, 16 September 2002, Retrieved 25 October 2011.
Life support
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. 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
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." Space Weather: A Research Perspective , National Academy of Sciences, 1997
Environmental considerations
Exhaust pollution of rockets depends on the produced exhausts by the propellants reactions and the location of exhaustion. They mostly exhaust and sometimes toxic components. Particularly at higher levels of the atmosphere the potency of exhausted gases as greenhouse gases increases considerably. 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.
While spaceflight altogether pollutes at a fraction of other human activities, it still does pollute heavily if calculated per passenger.
Regulation
A wide range of issues such as space traffic management or liability have been issues of spaceflight regulation.
Access
Inclusion has been a national and international issue, resulting in 1967 in the Outer Space Treaty and its claim of outer space as the "province of all mankind". Furthermore social inclusion in human spaceflight has been demanded, with women to fly to space being limited, and minorities, like people with disability, only having been selected in European Space Agency's 2022 astronaut group.
Applications
Current and proposed applications for spaceflight include:
Spacefaring
[[File:List of countries by spaceflight development.svg|thumb|upright=1.8|Map showing countries with spaceflight capability
Global coordination
The United Nations Office for Outer Space Affairs (UNOOSA) has been the main multilateral body servicing international contact and exchange on space activity among spacefaring and non-spacefaring states.
Crewed spacefaring nations
Currently Russia, the United States and China are the only crewed spacefaring .
Spacefaring nations listed by date of first crewed launch:
Uncrewed spacefaring nations
The following nations or organizations have developed their own launch vehicles to launch uncrewed spacecraft into orbit either from their own territory or with foreign assistance (date of first launch in parentheses):
Suborbital
Considering merely launching an object beyond the Kármán line to be the minimum requirement of spacefaring, Nazi Germany, with the V-2 rocket, became the first spacefaring nation in 1944. Peenemünde, Walter Dornberger, Moewig, Berlin 1984. . The following nations have only achieved suborbital spaceflight capability by launching indigenous or or both into suborbital space:
See also
Further reading
(2025). 9780262536332, The MIT Press. ISBN 9780262536332
External links
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