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. 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.
As of 2016, only three nations have flown manned spacecraft: USSR/Russia, USA, and China. The first manned spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, and completed a full Earth orbit. There were five other manned missions which used a Vostok spacecraft. The second manned 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 manned missions using Mercury spacecraft.
Other Soviet manned spacecraft include the Voskhod, Soyuz, flown unmanned as Zond/L1, L3, TKS, and the Salyut and Mir manned space stations. Other American manned 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 manned mission was in 2003).
Except for the space shuttle, all of the recoverable manned orbital spacecraft were space capsules.
Manned space capsulesThe International Space Station, manned since November 2000, is a joint venture between Russia, the United States, Canada and several other countries.
Some reusable vehicles have been designed only for manned spaceflight, and these are often called spaceplanes. The first example of such was the North American X-15 spaceplane, which conducted two manned 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 (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight and this was unmanned. 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 Space X'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.
Zond/L1 – lunar flyby capsuleL3 – capsule and lunar landerTKS – capsuleBuran-class shuttle – Soviet shuttleProgress – unmanned USSR/Russia cargo spacecraftTKS – unmanned USSR/Russia cargo spacecraft and space station moduleAutomated Transfer Vehicle (ATV) – unmanned European cargo spacecraftH-II Transfer Vehicle (HTV) – unmanned Japanese cargo spacecraftSpaceX Dragon – unmanned private spacecraftTianzhou 1(spacecraft) – China's unmanned spacecraftExplorer 1 – first US satelliteProject SCORE – first communications satelliteSolar and Heliospheric Observatory (SOHO) - orbits the Sun near L1Sputnik 1 – world's first artificial satelliteSputnik 2 – first animal in orbit (Laika)Sputnik 5 – first capsule recovered from orbit (Vostok precursor) – animals survivedSyncom – first geosynchronous communications satelliteHubble Space Telescope – largest orbital observatoryX-37 – spaceplaneClementine – US Navy mission, orbited Moon, detected hydrogen at the polesKaguya JPN – Lunar orbiterLuna 1 – first lunar flybyLuna 2 – first lunar impactLuna 3 – first images of lunar far sideLuna 9 – first soft landing on the MoonLuna 10 – first lunar orbiterLuna 16 – first unmanned lunar sample retrievalLunar Orbiter – very successful series of lunar mapping spacecraftLunar Prospector – confirmed detection of hydrogen at the lunar polesLunar Reconnaissance Orbiter – Identifies safe landing sites & Locates moon resourcesLunokhod - Soviet lunar roversSMART-1 ESA – Lunar ImpactSurveyor – first USA soft landerChang'e 1 – China's Chang'e Lunar missionChang'e 2 – China's Chang'e Lunar missionChang'e 3 – China's Chang'e Lunar missionChang'e 4 – China's Chang'e Lunar missionChang'e 5 – China's Chang'e Lunar missionChang'e 6 – China's Chang'e Lunar missionChandrayaan 1 – First Indian Lunar missionAkatsuki JPN – a Venus orbiterCassini–Huygens – first Saturn orbiter + Titan landerCuriosity rover – Rover sent to Mars by NASA in 2012Galileo – first Jupiter orbiter+descent probeIKAROS JPN – first solar-sail spacecraftMariner 4 – first Mars flyby, first close and high resolution images of MarsMariner 9 – first Mars orbiterMariner 10 – first Mercury flyby, first close up imagesMars Exploration Rover – a Mars roverMars Express – a Mars orbiterMars Global Surveyor – a Mars orbiterMars Orbiter Mission - India's first Interplanetary probe.Mars Reconnaissance Orbiter – an advanced climate, imaging, sub-surface radar, and telecommunications Mars orbiterMESSENGER – first Mercury orbiter (arrival 2011)Mars Pathfinder – a Mars lander + roverNew Horizons – first Pluto flyby (arrival 2015)Pioneer 10 – first Jupiter flyby, first close up imagesPioneer 11 – second Jupiter flyby + first Saturn flyby (first close up images of Saturn)Pioneer Venus – first Venus orbiter+landersVega 1 – Balloon release into Venus atmosphere and lander (joint mission with Vega 2), mothership continued on to fly by Halley's CometVenera 4 – first soft landing on another planet (Venus)Viking 1 – first soft landing on MarsVoyager 2 – Jupiter flyby + Saturn flyby + first flybys/images of Neptune and UranusClusterDeep Space 1Deep ImpactGenesisHayabusaNear Earth Asteroid RendezvousStardustSTEREO – Heliospheric and solar sensing; first images of the entire SunWMAPHelios I & II Solar Probes (252,792 km/h or 157,078 mph)Pioneer 10 at 114.07 AU as of January 2016, traveling outward at about 2.54/yearPioneer 11 at 111.4 AU as of July 2015, traveling outward at about 2.4 AU/yearVoyager 1 at 135.7 AU as of August 2016, traveling outward at about 3.6 AU/yearVoyager 2 at 111.4 AU as of August 2016, traveling outward at about 3.3 AU/yearShuguang – Chinese capsuleSoyuz Kontakt – USSR capsuleAlmaz – USSR space stationManned Orbiting Laboratory – US space stationAltair – US lunar lander of Orion spacecraftX-20 – US shuttleSoviet Spiral ShuttleSoviet Buran ShuttleESA Hermes shuttleKliper Russian semi-shuttle/semi-capsuleJapanese HOPE-X shuttleChinese Shuguang Project 921-3 shuttleRR/British Aerospace HOTOLESA Hopper OrbiterMcDonnell Douglas DC-X (Delta Clipper)Roton Rotored-HybridLockheed-Martin VentureStar(US-NASA) Orion Multi-Purpose Crew Vehicle – capsule(US-SpaceX ) Dragon V2 – capsule(US-Boeing) CST-100 – capsule(US-Sierra Nevada Corporation) Dream Chaser – orbital spaceplane(US-The SpaceShip company)SpaceShipTwo suborbital spaceplane(US-Blue Origin) New Shepard – VTVL capsule(US-XCOR) Lynx rocketplane – suborbital spaceplaneChina Shenzhou 3 spacecraft CargoChina Shenzhou 4 spacecraft CargoChina Shenzhou 5 spacecraft CargoChina Shenzhou 6 spacecraft CargoChina Shenzhou 7 spacecraft CargoChina Shenzhou 8 spacecraft CargoChina Shenzhou 9 spacecraft CargoChina Shenzhou 10 spacecraft Cargo(India-DRDO) Avatar RLV -Under development, First demonstration flight planned in 2015.(India-ISRO) Orbital Vehicle – capsule(India-ISRO) RLV Technology Demonstration Programme - SpacecraftSpaceX reusable rocket(Russia-RKA) Prospective Piloted Transport System (PPTS) – capsule(Europe-ESA) Advanced Crew Transportation System – capsule(Iranian Space Agency) Orbital Vehicle – capsuleSpaceX Dragon – cargo delivery to the ISSOrbital Sciences Cygnus – cargo delivery to the ISSCNES Mars NetlanderJames Webb Space Telescope (delayed)ESA Darwin14 probeMars Science Laboratory roverChina Shenzhou 1 spacecraft CargoChina Shenzhou 2 spacecraft CargoTerrestrial Planet Finder cancelled probeSystem F6—a DARPA Fractionated Spacecraft demonstratorReaction Engines Limited Skylon (spacecraft)Largest asteroid visited by spacecraft - NASA's Dawn spacecraft; asteroid 4 Vesta, 11 August 2011.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 supportSpacecraft intended for human spaceflight must also include a life support system for the crew.
Attitude controlA 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.
GNCGuidance 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 handlingThe 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.
CommunicationsSpacecraft, 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.
PowerSpacecraft 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 controlSpacecraft 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 propulsionSpacecraft 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.
StructuresSpacecraft 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.
PayloadThe 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 segmentThe
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.
Launch vehicleThe
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.