A spacecraft is a vehicle or machine designed to fly in outer space. Spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle (carrier rocket).

On a sub-orbital spaceflight, a space vehicle enters space and then returns to the surface, without having gained sufficient energy or velocity to make a full orbit of the Earth. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit (space stations) only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific research are space probes. Robotic spacecraft that remain in orbit around a planetary body are artificial satellites. To date, only a handful of interstellar probes, such as Pioneer 10 and 11, Voyager 1 and 2, and New Horizons, are on trajectories that leave the Solar System.

Orbital spacecraft may be recoverable or not. Most are not. Recoverable spacecraft may be subdivided by method of reentry to Earth into non-winged space capsules and winged spaceplanes.

Humanity has achieved space flight but only a few nations have the technology for orbital launches: Russia (RSA or "Roscosmos"), the United States (NASA), the member states of the European Space Agency (ESA), Japan (JAXA), China (CNSA), India (ISRO), Taiwan[1][2][3][4] (National Chung-Shan Institute of Science and Technology, Taiwan National Space Organization (NSPO),[5][6][7] Israel (ISA), Iran (ISA), and North Korea (NADA).

Soyuz TMA-7 spacecraft2edit1
More than 100 Soviet and Russian crewed Soyuz spacecraft (TMA version shown) have flown since 1967 and now support the International Space Station.
Space Shuttle Columbia launching
The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, Mir, and the ISS. (Columbia's first launch, which had a white external tank, shown)


The first artificial satellite, Sputnik 1. It was launched by the Soviet Union

A German V-2 became the first spacecraft when it reached an altitude of 189 km in June 1944 in Peenemünde, Germany.[8] Sputnik 1 was the first artificial satellite. It was launched into an elliptical low Earth orbit (LEO) by the Soviet Union on 4 October 1957. The launch ushered in new political, military, technological, and scientific developments; while the Sputnik launch was a single event, it marked the start of the Space Age.[9][10] Apart from its value as a technological first, Sputnik 1 also helped to identify the upper atmospheric layer's density, through measuring the satellite's orbital changes. It also provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen in the satellite's false body provided the first opportunity for meteoroid detection. Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in Kazakh SSR (now at the Baikonur Cosmodrome). The satellite travelled at 29,000 kilometers (18,000 mi) per hour, taking 96.2 minutes to complete an orbit, and emitted radio signals at 20.005 and 40.002 MHz

While Sputnik 1 was the first spacecraft to orbit the Earth, other man-made objects had previously reached an altitude of 100 km, which is the height required by the international organization Fédération Aéronautique Internationale to count as a spaceflight. This altitude is called the Kármán line. In particular, in the 1940s there were several test launches of the V-2 rocket, some of which reached altitudes well over 100 km.

Spacecraft types

Crewed spacecraft

Apollo 17 Command Module AS17-145-22261HR
Apollo 17 Command Module in Lunar orbit

As of 2016, only three nations have flown crewed spacecraft: USSR/Russia, USA, and China. The first crewed spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, and completed a full Earth orbit. There were five other crewed missions which used a Vostok spacecraft.[11] The second crewed spacecraft was named Freedom 7, and it performed a sub-orbital spaceflight in 1961 carrying American astronaut Alan Shepard to an altitude of just over 187 kilometers (116 mi). There were five other crewed missions using Mercury spacecraft.

Other Soviet crewed spacecraft include the Voskhod, Soyuz, flown uncrewed as Zond/L1, L3, TKS, and the Salyut and Mir crewed space stations. Other American crewed spacecraft include the Gemini spacecraft, Apollo spacecraft, the Skylab space station, and the Space Shuttle with undetached European Spacelab and private US Spacehab space stations-modules. China developed, but did not fly Shuguang, and is currently using Shenzhou (its first crewed mission was in 2003).

Except for the Space Shuttle, all of the recoverable crewed orbital spacecraft were space capsules.

Vostok spacecraft diagram

Soviet Vostok capsule

NASA spacecraft comparison

American Mercury, Gemini, and Apollo spacecraft

Voskhod 1 and 2

Soviet Voskhod (variant of Vostok)

Soyuz 7K-OK(A) drawing

1967 Soviet/Russian Soyuz spacecraft

Post S-7 Shenzhou spacecraft

Chinese Shenzhou

The International Space Station, crewed since November 2000, is a joint venture between Russia, the United States, Canada and several other countries.


STS-73 landing
Columbia orbiter landing

Some reusable vehicles have been designed only for crewed spaceflight, and these are often called spaceplanes. The first example of such was the North American X-15 spaceplane, which conducted two crewed flights which reached an altitude of over 100 km in the 1960s. The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963.

The first partially reusable orbital spacecraft, a winged non-capsule, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 SCA and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was Columbia, followed by Challenger, Discovery, Atlantis, and Endeavour. Endeavour was built to replace Challenger when it was lost in January 1986. Columbia broke up during reentry in February 2003.

The first automatic partially reusable spacecraft was the Buran-class shuttle, launched by the USSR on November 15, 1988, although it made only one flight and this was uncrewed. This spaceplane was designed for a crew and strongly resembled the U.S. 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 subsequently modified to allow for autonomous re-entry in case of necessity.

Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by SpaceX's Dragon V2 and Boeing's CST-100 Starliner no later than 2017. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Space Launch System and SpaceX's Falcon Heavy.

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 will build its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic was planned to begin reusable private spaceflight carrying paying passengers in 2014, but was delayed after the crash of VSS Enterprise.

Unmanned spacecraft

Mariner 10's encounter with Venus (diagram)
Mariner 10 diagram of trajectory past planet Venus

Designed as manned but flown as unmanned only spacecraft

Semi-manned – manned as space stations or part of space stations

  • Progress – unmanned USSR/Russia cargo spacecraft
  • TKS – unmanned USSR/Russia cargo spacecraft and space station module
  • Automated Transfer Vehicle (ATV) – unmanned European cargo spacecraft
  • H-II Transfer Vehicle (HTV) – unmanned Japanese cargo spacecraft
  • SpaceX Dragon – unmanned private spacecraft
  • Tianzhou 1 (spacecraft) – China's unmanned spacecraft

Earth-orbit satellites

Lunar probes

Cassini Saturn Orbit Insertion
Artist's conception of Cassini–Huygens as it enters Saturn's orbit
Phoenix landing
Artist's conception of the Phoenix spacecraft as it lands on Mars

Planetary probes

Other – deep space

Fastest spacecraft

  • Parker Solar Probe (estimated 343,000 km/h or 213,000 mph at first sun close pass, will reach 700,000 km/h or 430,000 mph at final perihelion)[12]
  • Helios I and II Solar Probes (252,792 km/h or 157,078 mph)

Furthest spacecraft from the Sun

  • Voyager 1 at 144.20 AU as of December 2018, traveling outward at about 3.58 AU/year[13]
  • Pioneer 10 at 122.48 AU as of December 2018, traveling outward at about 2.52 AU/year[13]
  • Voyager 2 at 119.34 AU as of December 2018, traveling outward at about 3.24 AU/year[13]
  • Pioneer 11 at 101.17 AU as of December 2018, traveling outward at about 2.37 AU/year[13]

Unfunded and canceled programs

Delta Clipper DC-X first flight
The first test flight of the Delta Clipper-Experimental Advanced (DC-XA), a prototype launch system

Manned spacecraft

Multi-stage spaceplanes

SSTO spaceplanes

Spacecraft under development




A spacecraft system comprises various subsystems, depending on the mission profile. Spacecraft subsystems comprise the spacecraft's "bus" and may include attitude determination and control (variously called ADAC, ADC, or ACS), guidance, navigation and control (GNC or GN&C), communications (comms), command and data handling (CDH or C&DH), power (EPS), thermal control (TCS), propulsion, and structures. Attached to the bus are typically payloads.

Life support
Spacecraft intended for human spaceflight must also include a life support system for the crew.
Shuttle front RCS
Reaction control system thrusters on the front of the U.S. Space Shuttle
Attitude control
A Spacecraft needs an attitude control subsystem to be correctly oriented in space and respond to external torques and forces properly. The attitude control subsystem consists of sensors and actuators, together with controlling algorithms. The attitude-control subsystem permits proper pointing for the science objective, sun pointing for power to the solar arrays and earth pointing for communications.
Guidance refers to the calculation of the commands (usually done by the CDH subsystem) needed to steer the spacecraft where it is desired to be. Navigation means determining a spacecraft's orbital elements or position. Control means adjusting the path of the spacecraft to meet mission requirements.
Command and data handling
The CDH subsystem receives commands from the communications subsystem, performs validation and decoding of the commands, and distributes the commands to the appropriate spacecraft subsystems and components. The CDH also receives housekeeping data and science data from the other spacecraft subsystems and components, and packages the data for storage on a data recorder or transmission to the ground via the communications subsystem. Other functions of the CDH include maintaining the spacecraft clock and state-of-health monitoring.
Spacecraft, both robotic and crewed, utilize various communications systems for communication with terrestrial stations as well as for communication between spacecraft in space. Technologies utilized include RF and optical communication. In addition, some spacecraft payloads are explicitly for the purpose of ground–ground communication using receiver/retransmitter electronic technologies.
Spacecraft need an electrical power generation and distribution subsystem for powering the various spacecraft subsystems. For spacecraft near the Sun, solar panels are frequently used to generate electrical power. Spacecraft designed to operate in more distant locations, for example Jupiter, might employ a radioisotope thermoelectric generator (RTG) to generate electrical power. Electrical power is sent through power conditioning equipment before it passes through a power distribution unit over an electrical bus to other spacecraft components. Batteries are typically connected to the bus via a battery charge regulator, and the batteries are used to provide electrical power during periods when primary power is not available, for example when a low Earth orbit spacecraft is eclipsed by Earth.
Thermal control
Spacecraft must be engineered to withstand transit through Earth's atmosphere and the space environment. They must operate in a vacuum with temperatures potentially ranging across hundreds of degrees Celsius as well as (if subject to reentry) in the presence of plasmas. Material requirements are such that either high melting temperature, low density materials such as beryllium and reinforced carbon–carbon or (possibly due to the lower thickness requirements despite its high density) tungsten or ablative carbon–carbon composites are used. Depending on mission profile, spacecraft may also need to operate on the surface of another planetary body. The thermal control subsystem can be passive, dependent on the selection of materials with specific radiative properties. Active thermal control makes use of electrical heaters and certain actuators such as louvers to control temperature ranges of equipments within specific ranges.
Spacecraft propulsion
Spacecraft may or may not have a propulsion subsystem, depending on whether or not the mission profile calls for propulsion. The Swift spacecraft is an example of a spacecraft that does not have a propulsion subsystem. Typically though, LEO spacecraft include a propulsion subsystem for altitude adjustments (drag make-up maneuvers) and inclination adjustment maneuvers. A propulsion system is also needed for spacecraft that perform momentum management maneuvers. Components of a conventional propulsion subsystem include fuel, tankage, valves, pipes, and thrusters. The thermal control system interfaces with the propulsion subsystem by monitoring the temperature of those components, and by preheating tanks and thrusters in preparation for a spacecraft maneuver.
Spacecraft must be engineered to withstand launch loads imparted by the launch vehicle, and must have a point of attachment for all the other subsystems. Depending on mission profile, the structural subsystem might need to withstand loads imparted by entry into the atmosphere of another planetary body, and landing on the surface of another planetary body.
The payload depends on the mission of the spacecraft, and is typically regarded as the part of the spacecraft "that pays the bills". Typical payloads could include scientific instruments (cameras, telescopes, or particle detectors, for example), cargo, or a human crew.
Ground segment
The ground segment, though not technically part of the spacecraft, is vital to the operation of the spacecraft. Typical components of a ground segment in use during normal operations include a mission operations facility where the flight operations team conducts the operations of the spacecraft, a data processing and storage facility, ground stations to radiate signals to and receive signals from the spacecraft, and a voice and data communications network to connect all mission elements.[15]
Launch vehicle
The launch vehicle propels the spacecraft from Earth's surface, through the atmosphere, and into an orbit, the exact orbit being dependent on the mission configuration. The launch vehicle may be expendable or reusable.

See also



  1. ^ Adams, Sam (29 August 2016). "Taiwanese navy fires NUCLEAR MISSILE at fisherman during horrifying accident".
  2. ^ "At Mach-10, Taiwan's Hsiung Feng-III 'Anti-China' Missiles could be faster than the BrahMos". Archived from the original on 2017-08-07. Retrieved 2019-01-08.
  3. ^ "Taiwanese navy sinks fishing boat with hypersonic missile fired BY MISTAKE as tensions rise". 2 September 2016.
  4. ^ Villasanta, Arthur Dominic (21 October 2016). "Taiwan Extending the Range of its Hsiung Feng III Missiles to Reach China".
  5. ^ News, Taiwan. "Taiwan's upgraded 'Cloud Peak' mi... - Taiwan News".
  6. ^ "Taiwan To Upgrade 'Cloud Peak' Medium-range Missiles For Micro-Satellites Launch".
  7. ^ Sheldon, John. "Taiwan's New Ballistic Missile Capable of Launching Microsatellites - SpaceWatch.Global".
  8. ^ Peenemünde (Dokumentation) Berlin: Moewig, 1984.ISBN 3-8118-4341-9.
  9. ^ Dougall, Walter A. (Winter 2010) "Shooting the duck", American Heritage
  10. ^ Swenson, L. Jr.; Grimwood, J. M.; Alexander, C. C. This New Ocean, A History of Project Mercury. pp. 66–62424. On October 4, 1957 Sputnik I shot into orbit and forcibly opened the Space Age.
  11. ^ "Vostok". Encyclopedia Astronautica. Archived from the original on 2011-06-29.
  12. ^ Bartels, Meghan; November 6, Space com Senior Writer |; ET, 2018 07:00am. "NASA's Parker Solar Probe Just Made Its First Close Pass by the Sun!". Retrieved 2018-12-16.
  13. ^ a b c d "Spacecraft escaping the Solar System". Retrieved 2018-12-16.
  14. ^ "Wednesday, August 03, 2011India's Space Shuttle [Reusable Launch Vehicle (RLV)] program". AA Me, IN. 2011. Archived from the original on October 22, 2014. Retrieved 2014-10-22.
  15. ^ "The Rosetta ground segment". 2004-02-17. Archived from the original on 2008-03-11. Retrieved 2008-02-11.


  • Knight, Will (January 23, 2006). "Spacecraft skin 'heals' itself". New Scientist. Retrieved February 11, 2008.
  • Wertz, James; Larson, Wiley J (1999). Space Mission Analysis and Design (3rd ed.). Torrance, California: Microcosm. ISBN 978-1-881883-10-4.

External links

Aerospace engineering

Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is similar, but deals with the electronics side of aerospace engineering.

Aeronautical engineering was the original term for the field. As flight technology advanced to include craft operating in outer space (astronautics), the broader term "aerospace engineering" has come into common use. Aerospace engineering, particularly the astronautics branch is often colloquially referred to as "rocket science".

Apollo 11

Apollo 11 was the spaceflight that landed the first two people on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin, both American, landed the Apollo Lunar Module Eagle on July 20, 1969, at 20:17 UTC. Armstrong became the first person to step onto the lunar surface six hours later on July 21 at 02:56:15 UTC; Aldrin joined him 19 minutes later. They spent about two and a quarter hours together outside the spacecraft, and collected 47.5 pounds (21.5 kg) of lunar material to bring back to Earth. Command module pilot Michael Collins flew the command module Columbia alone in lunar orbit while they were on the Moon's surface. Armstrong and Aldrin spent 21.5 hours on the lunar surface before rejoining Columbia in lunar orbit.

Apollo 11 was launched by a Saturn V rocket from Kennedy Space Center on Merritt Island, Florida, on July 16 at 13:32 UTC, and was the fifth crewed mission of NASA's Apollo program. The Apollo spacecraft had three parts: a command module (CM) with a cabin for the three astronauts, and the only part that returned to Earth; a service module (SM), which supported the command module with propulsion, electrical power, oxygen, and water; and a lunar module (LM) that had two stages – a descent stage for landing on the Moon, and an ascent stage to place the astronauts back into lunar orbit.

After being sent to the Moon by the Saturn V's third stage, the astronauts separated the spacecraft from it and traveled for three days until they entered lunar orbit. Armstrong and Aldrin then moved into Eagle and landed in the Sea of Tranquillity. The astronauts used Eagle's ascent stage to lift off from the lunar surface and rejoin Collins in the command module. They jettisoned Eagle before they performed the maneuvers that blasted them out of lunar orbit on a trajectory back to Earth. They returned to Earth and splashed down in the Pacific Ocean on July 24 after more than eight days in space.

Armstrong's first step onto the lunar surface was broadcast on live TV to a worldwide audience. He described the event as "one small step for [a] man, one giant leap for mankind." Apollo 11 effectively ended the Space Race and fulfilled a national goal proposed in 1961 by President John F. Kennedy: "before this decade is out, of landing a man on the Moon and returning him safely to the Earth."

Apollo program

The Apollo program, also known as Project Apollo, was the third United States human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), which succeeded in landing the first humans on the Moon from 1969 to 1972. First conceived during Dwight D. Eisenhower's administration as a three-man spacecraft to follow the one-man Project Mercury which put the first Americans in space, Apollo was later dedicated to President John F. Kennedy's national goal of "landing a man on the Moon and returning him safely to the Earth" by the end of the 1960s, which he proposed in an address to Congress on May 25, 1961. It was the third US human spaceflight program to fly, preceded by the two-man Project Gemini conceived in 1961 to extend spaceflight capability in support of Apollo.

Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module (LM) on July 20, 1969, and walked on the lunar surface, while Michael Collins remained in lunar orbit in the command and service module (CSM), and all three landed safely on Earth on July 24. Five subsequent Apollo missions also landed astronauts on the Moon, the last in December 1972. In these six spaceflights, twelve men walked on the Moon.

Apollo ran from 1961 to 1972, with the first manned flight in 1968. It achieved its goal of manned lunar landing, despite the major setback of a 1967 Apollo 1 cabin fire that killed the entire crew during a prelaunch test. After the first landing, sufficient flight hardware remained for nine follow-on landings with a plan for extended lunar geological and astrophysical exploration. Budget cuts forced the cancellation of three of these. Five of the remaining six missions achieved successful landings, but the Apollo 13 landing was prevented by an oxygen tank explosion in transit to the Moon, which destroyed the service module's capability to provide electrical power, crippling the CSM's propulsion and life support systems. The crew returned to Earth safely by using the lunar module as a "lifeboat" for these functions. Apollo used Saturn family rockets as launch vehicles, which were also used for an Apollo Applications Program, which consisted of Skylab, a space station that supported three manned missions in 1973–74, and the Apollo–Soyuz Test Project, a joint US-Soviet Union Earth-orbit mission in 1975.

Apollo set several major human spaceflight milestones. It stands alone in sending manned missions beyond low Earth orbit. Apollo 8 was the first manned spacecraft to orbit another celestial body, while the final Apollo 17 mission marked the sixth Moon landing and the ninth manned mission beyond low Earth orbit. The program returned 842 pounds (382 kg) of lunar rocks and soil to Earth, greatly contributing to the understanding of the Moon's composition and geological history. The program laid the foundation for NASA's subsequent human spaceflight capability and funded construction of its Johnson Space Center and Kennedy Space Center. Apollo also spurred advances in many areas of technology incidental to rocketry and manned spaceflight, including avionics, telecommunications, and computers.


Arabsat-6A is a communications satellite operated by Arabsat and owned by League of Arab States. The satellite was successfully launched by SpaceX's Falcon Heavy on April 11, 2019 at 6:35 pm EDT and was released into orbit at 7:09 PM EDT.


The Cassini–Huygens mission ( kə-SEE-nee HOY-gənz), commonly called Cassini, was a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a probe to study the planet Saturn and its system, including its rings and natural satellites. The Flagship-class robotic spacecraft comprised both NASA's Cassini probe, and ESA's Huygens lander which landed on Saturn's largest moon, Titan. Cassini was the fourth space probe to visit Saturn and the first to enter its orbit. The craft were named after astronomers Giovanni Cassini and Christiaan Huygens.

Launched aboard a Titan IVB/Centaur on October 15, 1997, Cassini was active in space for nearly 20 years, with 13 years spent orbiting Saturn, studying the planet and its system after entering orbit on July 1, 2004. The voyage to Saturn included flybys of Venus (April 1998 and July 1999), Earth (August 1999), the asteroid 2685 Masursky, and Jupiter (December 2000). Its mission ended on September 15, 2017, when Cassini's trajectory took it into Saturn's upper atmosphere and it burned up in order to prevent any risk of contaminating Saturn's moons, which might have offered habitable environments to stowaway terrestrial microbes on the spacecraft. The mission is widely perceived to have been successful beyond expectation. Cassini-Huygens has been described by NASA's Planetary Science Division Director as a "mission of firsts", that has revolutionized human understanding of the Saturn system, including its moons and rings, and our understanding of where life might be found in the Solar System.

Cassini's original mission was planned to last for four years, from June 2004 to May 2008. The mission was extended for another two years until September 2010, branded the Cassini Equinox Mission. The mission was extended a second and final time with the Cassini Solstice Mission, lasting another seven years until September 15, 2017, on which date Cassini was de-orbited to burn up in Saturn's upper atmosphere.

The Huygens module traveled with Cassini until its separation from the probe on December 25, 2004; it was landed by parachute on Titan on January 14, 2005. It returned data to Earth for around 90 minutes, using the orbiter as a relay. This was the first landing ever accomplished in the outer Solar System and the first landing on a moon other than Earth's Moon.

At the end of its mission, the Cassini spacecraft executed the "Grand Finale" of its mission: a number of risky passes through the gaps between Saturn and Saturn's inner rings. The purpose of this phase was to maximize Cassini's scientific outcome before the spacecraft was disposed. The atmospheric entry of Cassini ended the mission, but analyses of the returned data will continue for many years.

Chandra X-ray Observatory

The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched on STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, enabled by the high angular resolution of its mirrors. Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes; therefore space-based telescopes are required to make these observations. Chandra is an Earth satellite in a 64-hour orbit, and its mission is ongoing as of 2019.

Chandra is one of the Great Observatories, along with the Hubble Space Telescope, Compton Gamma Ray Observatory (1991–2000), and the Spitzer Space Telescope. The telescope is named after the Nobel Prize-winning Indian-American astrophysicist Subrahmanyan Chandrasekhar. Its mission is similar to that of ESA's XMM-Newton spacecraft, also launched in 1999.

Juno (spacecraft)

Juno is a NASA space probe orbiting the planet Jupiter. It was built by Lockheed Martin and is operated by NASA's Jet Propulsion Laboratory. The spacecraft was launched from Cape Canaveral Air Force Station on August 5, 2011 (UTC), as part of the New Frontiers program, and entered a polar orbit of Jupiter on July 5, 2016 (UTC; July 4 U.S. time), to begin a scientific investigation of the planet. After completing its mission, Juno will be intentionally deorbited into Jupiter's atmosphere.Juno's mission is to measure Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. It will also search for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere, mass distribution, and its deep winds, which can reach speeds up to 618 kilometers per hour (384 mph).Juno is the second spacecraft to orbit Jupiter, after the nuclear powered Galileo orbiter, which orbited from 1995 to 2003. Unlike all earlier spacecraft sent to the outer planets, Juno is powered by solar arrays, commonly used by satellites orbiting Earth and working in the inner Solar System, whereas radioisotope thermoelectric generators are commonly used for missions to the outer Solar System and beyond. For Juno, however, the three largest solar array wings ever deployed on a planetary probe play an integral role in stabilizing the spacecraft as well as generating power.

List of missions to the Moon

As part of human exploration of the Moon, numerous space missions have been undertaken to study Earth's natural satellite. Of the Moon landings; Luna 2 was the first spacecraft to reach its surface successfully, intentionally impacting the Moon on 13 September 1959. In 1966, Luna 9 became the first spacecraft to achieve a controlled soft landing, while Luna 10 became the first mission to enter orbit.

Between 1968 and 1972, manned missions to the Moon were conducted by the United States as part of the Apollo program. Apollo 8 was the first manned mission to enter orbit in December 1968, and was followed by Apollo 10 in May 1969. Six missions landed men on the Moon, beginning with Apollo 11 in July 1969, during which Neil Armstrong became the first man to walk on the Moon. Apollo 13 was intended to land, however it was restricted to a flyby due to a malfunction aboard the spacecraft. All nine manned missions returned safely to the Earth.

While the United States focused on the manned Apollo program, the Soviet Union conducted unmanned missions that deployed rovers and returned samples to the Earth. Three rover missions were launched, of which two were successful, and eleven sample return flights were attempted with three successes.

Missions to the Moon have been conducted by the Soviet Union, United States, European Space Agency, Japan, India, People's Republic of China and Israel. The Moon has also been visited by five spacecraft not dedicated to studying it; four spacecraft have flown past it to gain gravity assistance, and a radio telescope, Explorer 49, was placed into selenocentric orbit in order to use the Moon to block interference from terrestrial radio sources.

Moon landing

A Moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both manned and unmanned (robotic) missions. The first human-made object to reach the surface of the Moon was the Soviet Union's Luna 2 mission, on 13 September 1959.The United States' Apollo 11 was the first manned mission to land on the Moon, on 20 July 1969. There have been six manned U.S. landings (between 1969 and 1972) and numerous unmanned landings, with no soft landings happening from 22 August 1976 until 14 December 2013.

To date, the United States is the only country to have successfully conducted manned missions to the Moon, with the last departing the lunar surface in December 1972. All manned and unmanned soft landings had taken place on the near side of the Moon, until 3 January 2019 when the Chinese Chang'e 4 spacecraft made the first landing on the far side of the Moon.


The National Aeronautics and Space Administration (NASA, ) is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research.NASA was established in 1958, succeeding the National Advisory Committee for Aeronautics (NACA). The new agency was to have a distinctly civilian orientation, encouraging peaceful applications in space science. Since its establishment, most US space exploration efforts have been led by NASA, including the Apollo Moon landing missions, the Skylab space station, and later the Space Shuttle. NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the Space Launch System and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches.

NASA science is focused on better understanding Earth through the Earth Observing System; advancing heliophysics through the efforts of the Science Mission Directorate's Heliophysics Research Program; exploring bodies throughout the Solar System with advanced robotic spacecraft missions such as New Horizons; and researching astrophysics topics, such as the Big Bang, through the Great Observatories and associated programs.

New Horizons

New Horizons is an interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by S. Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow, which as of 2019 includes 2014 MU69. It is the fifth space probe to achieve the escape velocity needed to leave the Solar System.

On January 19, 2006, New Horizons was launched from Cape Canaveral Air Force Station by an Atlas V rocket directly into an Earth-and-solar escape trajectory with a speed of about 16.26 km/s (10.10 mi/s; 58,500 km/h; 36,400 mph). It was the fastest man-made object ever launched from Earth. After a brief encounter with asteroid 132524 APL, New Horizons proceeded to Jupiter, making its closest approach on February 28, 2007, at a distance of 2.3 million kilometers (1.4 million miles). The Jupiter flyby provided a gravity assist that increased New Horizons' speed; the flyby also enabled a general test of New Horizons' scientific capabilities, returning data about the planet's atmosphere, moons, and magnetosphere.

Most of the post-Jupiter voyage was spent in hibernation mode to preserve on-board systems, except for brief annual checkouts. On December 6, 2014, New Horizons was brought back online for the Pluto encounter, and instrument check-out began. On January 15, 2015, the spacecraft began its approach phase to Pluto.

On July 14, 2015, at 11:49 UTC, it flew 12,500 km (7,800 mi) above the surface of Pluto, making it the first spacecraft to explore the dwarf planet. On October 25, 2016, at 21:48 UTC, the last of the recorded data from the Pluto flyby was received from New Horizons. Having completed its flyby of Pluto, New Horizons then maneuvered for a flyby of Kuiper belt object (486958) 2014 MU69 "Ultima Thule", which occurred on January 1, 2019, when it was 43.4 AU from the Sun. In August 2018, NASA cited results by Alice on New Horizons to confirm the existence of a "hydrogen wall" at the outer edges of the Solar System. This "wall" was first detected in 1992 by the two Voyager spacecraft.

Orion (spacecraft)

The Orion Multi-Purpose Crew Vehicle (Orion MPCV) is an American-European interplanetary spacecraft intended to carry a crew of four astronauts to destinations at or beyond low Earth orbit (LEO). Currently under development by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) for launch on the Space Launch System, Orion is intended to facilitate human exploration of the Moon, asteroids and of Mars and to retrieve crew or supplies from the International Space Station if needed.The Orion MPCV was announced by NASA on May 24, 2011, and is currently under development. Its design is based on the Orion Crew Exploration Vehicle from the cancelled Constellation program. It has two main modules. The Orion command module is being built by Lockheed Martin at the Michoud Assembly Facility in New Orleans. The Orion service module, provided by the European Space Agency, is being built by Airbus Defence and Space.

The MPCV's first test flight (uncrewed), known as Exploration Flight Test 1 (EFT-1), was launched atop a Delta IV Heavy rocket on December 5, 2014, on a flight lasting 4 hours and 24 minutes, landing at its target in the Pacific Ocean at 10:29 Central (delayed from the prior day due to technical and weather problems). The first mission to carry astronauts is not expected to take place until 2023 at the earliest, although NASA officials have said that their staff is working toward an "aggressive internal goal" of 2021. However, a July 2016 Government Accountability Office report cast doubt on even the 2023 launch date, suggesting it may slip up to six months. The report gave only a 40% confidence in the 2021 launch date, and suggested the aggressive goal may be counterproductive to the program.

Project Gemini

Project Gemini was NASA's second human spaceflight program. Conducted between projects Mercury and Apollo, Gemini started in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews flew low Earth orbit (LEO) missions during 1965 and 1966, putting the United States in the lead during the Cold War Space Race against the Soviet Union.

Gemini's objective was the development of space travel techniques to support the Apollo mission to land astronauts on the Moon. It performed missions long enough for a trip to the Moon and back, perfected working outside the spacecraft with extra-vehicular activity (EVA), and pioneered the orbital maneuvers necessary to achieve space rendezvous and docking. With these new techniques proven by Gemini, Apollo could pursue its prime mission without doing these fundamental exploratory operations.

All Gemini flights were launched from Launch Complex 19 (LC-19) at Cape Kennedy Air Force Station in Florida. Their launch vehicle was the Gemini–Titan II, a modified Intercontinental Ballistic Missile (ICBM). Gemini was the first program to use the newly built Mission Control Center at the Houston Manned Spacecraft Center for flight control.The astronaut corps that supported Project Gemini included the "Mercury Seven", "The New Nine", and the 1963 astronaut class. During the program, three astronauts died in air crashes during training, including both members of the prime crew for Gemini 9. This mission was flown by the backup crew, the only time a backup crew has completely replaced a prime crew on a mission in NASA's history to date.

Gemini was robust enough that the United States Air Force planned to use it for the Manned Orbital Laboratory (MOL) program, which was later canceled. Gemini's chief designer, Jim Chamberlin, also made detailed plans for cislunar and lunar landing missions in late 1961. He believed that Gemini spacecraft could fly in lunar operations before Project Apollo, and cost less. NASA's administration did not approve those plans. In 1969, McDonnell-Douglas proposed a "Big Gemini" that could have been used to shuttle up to 12 astronauts to the planned space stations in the Apollo Applications Project (AAP). The only AAP project funded was Skylab – which used existing spacecraft and hardware – thereby eliminating the need for Big Gemini.

Project Mercury

Project Mercury was the first human spaceflight program of the United States, running from 1958 through 1963. An early highlight of the Space Race, its goal was to put a man into Earth orbit and return him safely, ideally before the Soviet Union. Taken over from the US Air Force by the newly created civilian space agency NASA, it conducted twenty unmanned developmental flights (some using animals), and six successful flights by astronauts. The program, which took its name from Roman mythology, cost $2.2 billion adjusted for inflation. The astronauts were collectively known as the "Mercury Seven", and each spacecraft was given a name ending with a "7" by its pilot.

The Space Race began with the 1957 launch of the Soviet satellite Sputnik 1. This came as a shock to the American public, and led to the creation of NASA to expedite existing US space exploration efforts, and place most of them under civilian control. After the successful launch of the Explorer 1 satellite in 1958, manned spaceflight became the next goal. The Soviet Union put the first human, cosmonaut Yuri Gagarin, into a single orbit aboard Vostok 1 on April 12, 1961. Shortly after this, on May 5, the US launched its first astronaut, Alan Shepard, on a suborbital flight. Soviet Gherman Titov followed with a day-long orbital flight in August 1961. The US reached its orbital goal on February 20, 1962, when John Glenn made three orbits around the Earth. When Mercury ended in May 1963, both nations had sent six people into space, but the Soviets led the US in total time spent in space.

The Mercury space capsule was produced by McDonnell Aircraft, and carried supplies of water, food and oxygen for about one day in a pressurized cabin. Mercury flights were launched from Cape Canaveral Air Force Station in Florida, on launch vehicles modified from the Redstone and Atlas D missiles. The capsule was fitted with a launch escape rocket to carry it safely away from the launch vehicle in case of a failure. The flight was designed to be controlled from the ground via the Manned Space Flight Network, a system of tracking and communications stations; back-up controls were outfitted on board. Small retrorockets were used to bring the spacecraft out of its orbit, after which an ablative heat shield protected it from the heat of atmospheric reentry. Finally, a parachute slowed the craft for a water landing. Both astronaut and capsule were recovered by helicopters deployed from a US Navy ship.

The Mercury project gained popularity, and its missions were followed by millions on radio and TV around the world. Its success laid the groundwork for Project Gemini, which carried two astronauts in each capsule and perfected space docking maneuvers essential for manned lunar landings in the subsequent Apollo program announced a few weeks after the first manned Mercury flight.

Soyuz (spacecraft)

Soyuz (Russian: Сою́з, IPA: [sɐˈjus], lit. Union) is a series of spacecraft designed for the Soviet space program by the Korolev Design Bureau (now RKK Energia) in the 1960s that remains in service today. The Soyuz succeeded the Voskhod spacecraft and was originally built as part of the Soviet manned lunar programs. The Soyuz spacecraft is launched on a Soyuz rocket, the most reliable launch vehicle in the world to date. The Soyuz rocket design is based on the Vostok launcher, which in turn was based on the 8K74 or R-7A Semyorka, a Soviet intercontinental ballistic missile. All Soyuz spacecraft are launched from the Baikonur Cosmodrome in Kazakhstan. Soyuz is currently the only means for manned space flights in the world and is heavily used in the International Space Station program.


Space Exploration Technologies Corp., doing business as SpaceX, is a private American aerospace manufacturer and space transportation services company headquartered in Hawthorne, California. It was founded in 2002 by entrepreneur Elon Musk with the goal of reducing space transportation costs and enabling the colonization of Mars. SpaceX has since developed the Falcon launch vehicle family and the Dragon spacecraft family, which both currently deliver payloads into Earth orbit.

SpaceX's achievements include the first privately funded liquid-propellant rocket to reach orbit (Falcon 1 in 2008), the first private company to successfully launch, orbit, and recover a spacecraft (Dragon in 2010), the first private company to send a spacecraft to the International Space Station (Dragon in 2012), the first propulsive landing for an orbital rocket (Falcon 9 in 2015), the first reuse of an orbital rocket (Falcon 9 in 2017), and the first private company to launch an object into orbit around the sun (Falcon Heavy's payload of a Tesla Roadster in 2018). SpaceX has flown 16 resupply missions to the International Space Station (ISS) under a partnership with NASA. NASA also awarded SpaceX a further development contract in 2011 to develop and demonstrate a human-rated Dragon, which would be used to transport astronauts to the ISS and return them safely to Earth. SpaceX conducted the maiden launch of its Crew Dragon spacecraft on a NASA-required demonstration flight on March 2, 2019 and is set to launch its first crewed Crew Dragon later in 2019. On 11 March at 8:45 a.m. EST, the Spacex Crew Dragon completed its first uncrewed flight that splash-landed in the Atlantic. The flight named SpX-DM1 has demonstrated the Crew Dragon's ability to safely transport crew to ISS and back..

SpaceX announced in 2011 that it was beginning a reusable launch system technology development program. In December 2015, the first Falcon 9 was flown back to a landing pad near the launch site, where it successfully accomplished a propulsive vertical landing. This was the first such achievement by a rocket for orbital spaceflight. In April 2016, with the launch of CRS-8, SpaceX successfully vertically landed the first stage on an ocean drone ship landing platform. In May 2016, in another first, SpaceX again landed the first stage, but during a significantly more energetic geostationary transfer orbit mission. In March 2017, SpaceX became the first to successfully re-launch and land the first stage of an orbital rocket.In September 2016, CEO Elon Musk unveiled the mission architecture of the Interplanetary Transport System program, an ambitious privately funded initiative to develop spaceflight technology for use in crewed interplanetary spaceflight. In 2017, Musk unveiled an updated configuration of the system, now named Starship and Super Heavy, which is planned to be fully reusable and will be the largest rocket ever on its debut, currently scheduled for the early 2020s.

Space Shuttle Challenger

Space Shuttle Challenger (Orbiter Vehicle Designation: OV-099) was the second orbiter of NASA's space shuttle program to be put into service, after Columbia. Challenger was built by Rockwell International's Space Transportation Systems Division, in Downey, California. Its maiden flight, STS-6, began on April 4, 1983. The orbiter was launched and landed nine times before breaking apart 73 seconds into its tenth mission, STS-51-L, on January 28, 1986, resulting in the death of all seven crew members, including a civilian school teacher. It was the first of two shuttles to be destroyed in flight, the other being Columbia, in 2003. The accident led to a two-and-a-half-year grounding of the shuttle fleet; flights resumed in 1988, with STS-26 flown by Discovery. Challenger was replaced by Endeavour, which was built from structural spares ordered by NASA in the construction contracts for Discovery and Atlantis.

Voyager 1

Voyager 1 is a space probe launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 was launched 16 days after its twin, Voyager 2. Having operated for 41 years, 7 months and 15 days as of April 20, 2019, the spacecraft still communicates with the Deep Space Network to receive routine commands and to transmit data to Earth. At a distance of 145 AU (21.7 billion km; 13.5 billion mi) from Earth as of February 22, 2019, it is the most distant from Earth of all known human-made objects.The probe's objectives included flybys of Jupiter, Saturn, and Saturn's largest moon, Titan. While the spacecraft's course could have been altered to include a Pluto encounter by forgoing the Titan flyby, exploration of the moon, which was known to have a substantial atmosphere, took priority. Voyager 1 studied the weather, magnetic fields, and rings of the two planets and was the first probe to provide detailed images of their moons.

After completing its primary mission with the flyby of Saturn on November 12, 1980, Voyager 1 became the third of five artificial objects to achieve the escape velocity required to leave the Solar System. On August 25, 2012, Voyager 1 became the first spacecraft to cross the heliopause and enter the interstellar medium.In a further testament to the robustness of Voyager 1, the Voyager team completed a successful test of the spacecraft's trajectory correction maneuver (TCM) thrusters in late 2017 (the first time these thrusters were fired since 1980), a project enabling the mission to be extended by two to three years.Voyager 1's extended mission is expected to continue until about 2025 when its radioisotope thermoelectric generators will no longer supply enough electric power to operate its scientific instruments.

Voyager 2

Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.

Its primary mission ended with the exploration of the Neptunian system on October 2, 1989, after having visited the Uranian system in 1986, the Saturnian system in 1981, and the Jovian system in 1979. Voyager 2 is now in its extended mission to study the outer reaches of the Solar System and has been operating for 41 years and 8 months as of 20 April 2019. It remains in contact through the NASA Deep Space Network.At a distance of 120 AU (1.80×1010 km) (about 16.5 light-hours) from the Sun as of February 25, 2019, moving at a velocity of 15.341 km/s (55,230 km/h) relative to the Sun, Voyager 2 is the fourth of five spacecraft to achieve the escape velocity that will allow them to leave the Solar System. The probe left the heliosphere for interstellar space on November 5, 2018, becoming the second artificial object to do so, and has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.

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