Outline of space science
The following outline is provided as an overview of and topical guide to space science: Space science encompasses all of the scientific disciplines that involve space exploration and study natural phenomena and physical bodies occurring in outer space, such as space medicine and astrobiology. The following outline is an overview of and topical guide to space science: Astronomy Outline of astronomy Fields of astronomy defined by approach Observational astronomy – Observatories on the ground as well as space observatories take measurements of celestial entities and phenomena Astrometry – studies the position and movements of celestial objects Amateur astronomy Theoretical astronomy – mathematical modelling of celestial entities and phenomena Fields of astronomy defined by scope Astrophysics – study of the physics of the universe. See Earth's location in the universe for an orientation. See Outline of space exploration Astronautics – science and engineering of spacefaring and spaceflight, a subset of Aerospace engineering Life in space Living organisms in space Humans in space Women in space Animals in space Dogs in space Soviet space dogs Monkeys and apes in space Microorganisms tested in outer space Plants in space Space habitation Architecture in space Space station Space Habitation Module Food in space Medicine in space Neuroscience in space Religion in space Christmas on the International Space Station Sex in space Survival in space Writing in space Human spaceflight Outline of aerospace Space Sciences Laboratory – University of California, Berkeley Space exploration – includes scientific investigations through manned spaceflight and space probes Space colonization Commercialization of space Space manufacturing Space tourism Space warfare Alien invasion Asteroid-impact avoidance Space law Remote sensing Planetarium – A synthetic observatory, used for education and presentations Centennial Challenges NASA prize contests Exploration of Mars Human spaceflight Space exploration Space architecture Space colonization Space industry Space industry of Russia Timeline of artificial satellites and space probes Batteries in space Control engineering Corrosion in space Industry in space Nuclear power in space Observatories in space Orbital mechanics Robotics Space environment – study of conditions that affect the operation of spacecraft Space logistics Space technology Space-based radar Space-based solar power Spacecraft design for launch vehicles and satellites Spacecraft propulsion Institute of Space Technology, PakistAn Space Sciences @ NASA Space Sciences @ ESA INDIAN INSTITUTE OF SPACE SCIENCE AND TECHNOLOGY Space Sciences Institute Space Science & Technology, an Iranian nongovernmental group who writes scientific articles about Space Science & Technology
A reconnaissance satellite or intelligence satellite is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The first generation type took photographs ejected canisters of photographic film which would descend to earth. Corona capsules were retrieved in mid-air. Spacecraft had digital imaging systems and downloaded the images via encrypted radio links. In the United States, most information available is on programs that existed up to 1972, as this information has been declassified due to its age; some information about programs prior to that time is still classified, a small amount of information is available on subsequent missions. A few up-to-date reconnaissance satellite images have been declassified on occasion, or leaked, as in the case of KH-11 photographs which were sent to Jane's Defence Weekly in 1984. On 16 March 1955, the United States Air Force ordered the development of an advanced reconnaissance satellite to provide continuous surveillance of "preselected areas of the Earth" in order "to determine the status of a potential enemy’s war-making capability".
There are several major types of reconnaissance satellite. Missile early warning Provides warning of an attack by detecting ballistic missile launches. Earliest known are Missile Defense Alarm System. Nuclear explosion detection characterizes nuclear explosions in space. Vela is the earliest known. Photo surveillance Provides imaging of earth from space. Images can be close-look telephoto. Corona is the earliest known. Spectral imaging is commonplace. Electronic reconnaissance Signals intelligence, intercepts stray radio waves. Samos-F is the earliest known. Radar imaging Most space-based radars use synthetic aperture radar. Can be used at night or through cloud cover. Earliest known are the Soviet US-A series. Examples of reconnaissance satellite missions: High resolution photography Measurement and Signature Intelligence Communications eavesdropping Covert communications Monitoring of nuclear test ban compliance Detection of missile launchesOn 28 August 2013, it was thought that "a $1-billion high-powered spy satellite capable of snapping pictures detailed enough to distinguish the make and model of an automobile hundreds of miles below" was launched from California's Vandenberg Air Force Base using a Delta IV Heavy launcher, America's highest-payload space launch vehicle.
On 17 February 2014, a Russian Kosmos-1220 launched in 1980 and used for naval missile targeting until 1982, made an uncontrolled atmospheric entry. Reconnaissance satellites have been used to enforce human rights, through the Satellite Sentinel Project, which monitors atrocities in Sudan and South Sudan. During his 1980 State of the Union Address, President Jimmy Carter explained how all of humanity benefited from the presence of American spy satellites:...photo-reconnaissance satellites, for example, are enormously important in stabilizing world affairs and thereby make a significant contribution to the security of all nations. Additionally, companies such as GeoEye and DigitalGlobe have provided commercial satellite imagery in support of natural disaster response and humanitarian missions. During the 1950s, a Soviet hoax had led to American fears of a bomber gap. In 1968, after gaining satellite photography, the United States' intelligence agencies were able to state with certainty that "No new ICBM complexes have been established in the USSR during the past year."
President Lyndon B. Johnson told a gathering in 1967: I wouldn't want to be quoted on this... We've spent $35 or $40 billion on the space program, and if nothing else had come out of it except the knowledge that we gained from space photography, it would be worth ten times what the whole program has cost. Because tonight we know how many missiles the enemy has and, it turned out, our guesses were way off. We were doing things. We were building things. We were harboring fears. Spy satellites are seen in spy fiction and military fiction; some works of fiction that focus on spy satellites include: The OMAC Project Enemy of the State Body of Lies Ice Station Zebra Karlsson-on-the-Roof is Sneaking Around Again Parmanu: The Story of Pokhran Defense Support Program European Union Satellite Centre List of intelligence gathering disciplines List of Kosmos satellites National Reconnaissance Office Satcom On The Move Kupperberg, Paul. Spy satellites. Rosen Publishing Group. ISBN 0-8239-3854-9 Richelson, Jeffrey.
America's Secret Eyes in Space: the U. S. Keyhole Spy Satellite Program. Harper & Row. ISBN 0-88730-285-8 Norris, Pat. "Spies in the Sky: Surveillance Satellites in War and Peace". Berlin. Retrieved 15 February 2012. FAS Intelligence Resource Program – Imagery Intelligence GlobalSecurity.org: Imagery Intelligence Iran to Launch first spy satellite Egyptsat1 Spaceports Around the World: Iraq's Al-Anbar Space Research Center Military Intelligence Satellites
In the context of spaceflight, a satellite is an artificial object, intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon. On 4 October 1957 the Soviet Union launched the world's first artificial satellite, Sputnik 1. Since about 8,100 satellites from more than 40 countries have been launched. According to a 2018 estimate, some 4,900 remain in orbit, of those about 1,900. 500 operational satellites are in low-Earth orbit, 50 are in medium-Earth orbit, the rest are in geostationary orbit. A few large satellites have been assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Venus, Jupiter, Saturn, a few asteroids, a comet and the Sun. Satellites are used for many purposes. Among several other applications, they can be used to make star maps and maps of planetary surfaces, take pictures of planets they are launched into.
Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, space telescopes. Space stations and human spacecraft in orbit are satellites. Satellite orbits vary depending on the purpose of the satellite, are classified in a number of ways. Well-known classes include low Earth orbit, polar orbit, geostationary orbit. A launch vehicle is a rocket, it lifts off from a launch pad on land. Some are launched at sea aboard a plane. Satellites are semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, attitude control and orbit control. "Newton's cannonball", presented as a "thought experiment" in A Treatise of the System of the World, by Isaac Newton was the first published mathematical study of the possibility of an artificial satellite. The first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon.
The idea surfaced again in Jules Verne's The Begum's Fortune. In 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, the first academic treatise on the use of rocketry to launch spacecraft, he calculated the orbital speed required for a minimal orbit, that a multi-stage rocket fuelled by liquid propellants could achieve this. In 1928, Herman Potočnik published The Problem of Space Travel -- The Rocket Motor, he described the use of orbiting spacecraft for observation of the ground and described how the special conditions of space could be useful for scientific experiments. In a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications, he suggested. The US military studied the idea of what was referred to as the "earth satellite vehicle" when Secretary of Defense James Forrestal made a public announcement on 29 December 1948, that his office was coordinating that project between the various services.
The first artificial satellite was Sputnik 1, launched by the Soviet Union on 4 October 1957, initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the United States. Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere; the unanticipated announcement of Sputnik 1's success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War. Sputnik 2 was launched on 3 November 1957 and carried the first living passenger into orbit, a dog named Laika. In May, 1946, Project RAND had released the Preliminary Design of an Experimental World-Circling Spaceship, which stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century." The United States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy.
The United States Air Force's Project RAND released the report, but considered the satellite to be a tool for science and propaganda, rather than a potential military weapon. In 1954, the Secretary of Defense stated, "I know of no American satellite program." In February 1954 Project RAND released "Scientific Uses for a Satellite Vehicle," written by R. R. Carhart; this expanded on potential scientific uses for satellite vehicles and was followed in June 1955 with "The Scientific Use of an Artificial Satellite," by H. K. Kallmann and W. W. Kellogg. In the context of activities planned for the International Geophysical Year, the White House announced on 29 July 1955 that the U. S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On 31 July, the Soviets announced that they intended to launch a satellite by the fall of 1957. Following pressure by the American Rocket Society, the National Science Foundation, the International Geophysical Year, military interest picked up and in early 1955 the Army and Navy were worki
Weather forecasting is the application of science and technology to predict the conditions of the atmosphere for a given location and time. People have attempted to predict the weather informally for millennia and formally since the 19th century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere at a given place and using meteorology to project how the atmosphere will change. Once calculated by hand based upon changes in barometric pressure, current weather conditions, sky condition or cloud cover, weather forecasting now relies on computer-based models that take many atmospheric factors into account. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, knowledge of model performance, knowledge of model biases; the inaccuracy of forecasting is due to the chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, the error involved in measuring the initial conditions, an incomplete understanding of atmospheric processes.
Hence, forecasts become less accurate as the difference between current time and the time for which the forecast is being made increases. The use of ensembles and model consensus help narrow the error and pick the most outcome. There are a variety of end uses to weather forecasts. Weather warnings are important forecasts because they are used to protect property. Forecasts based on temperature and precipitation are important to agriculture, therefore to traders within commodity markets. Temperature forecasts are used by utility companies to estimate demand over coming days. On an everyday basis, people use weather forecasts to determine. Since outdoor activities are curtailed by heavy rain and wind chill, forecasts can be used to plan activities around these events, to plan ahead and survive them. In 2009, the US spent $5.1 billion on weather forecasting. For millennia people have tried to forecast the weather. In 650 BC, the Babylonians predicted the weather from cloud patterns as well as astrology.
In about 350 BC, Aristotle described weather patterns in Meteorologica. Theophrastus compiled a book on weather forecasting, called the Book of Signs. Chinese weather prediction lore extends at least as far back as 300 BC, around the same time ancient Indian astronomers developed weather-prediction methods. In New Testament times, Christ himself referred to deciphering and understanding local weather patterns, by saying, "When evening comes, you say,'It will be fair weather, for the sky is red', in the morning,'Today it will be stormy, for the sky is red and overcast.' You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times."In 904 AD, Ibn Wahshiyya's Nabatean Agriculture, translated into Arabic from an earlier Aramaic work, discussed the weather forecasting of atmospheric changes and signs from the planetary astral alterations. Ancient weather forecasting methods relied on observed patterns of events termed pattern recognition. For example, it might be observed that if the sunset was red, the following day brought fair weather.
This experience accumulated over the generations to produce weather lore. However, not all of these predictions prove reliable, many of them have since been found not to stand up to rigorous statistical testing, it was not until the invention of the electric telegraph in 1835 that the modern age of weather forecasting began. Before that, the fastest that distant weather reports could travel was around 100 miles per day, but was more 40–75 miles per day. By the late 1840s, the telegraph allowed reports of weather conditions from a wide area to be received instantaneously, allowing forecasts to be made from knowledge of weather conditions further upwind; the two men credited with the birth of forecasting as a science were an officer of the Royal Navy Francis Beaufort and his protégé Robert FitzRoy. Both were influential men in British naval and governmental circles, though ridiculed in the press at the time, their work gained scientific credence, was accepted by the Royal Navy, formed the basis for all of today's weather forecasting knowledge.
Beaufort developed the Wind Force Scale and Weather Notation coding, which he was to use in his journals for the remainder of his life. He promoted the development of reliable tide tables around British shores, with his friend William Whewell, expanded weather record-keeping at 200 British Coast guard stations. Robert FitzRoy was appointed in 1854 as chief of a new department within the Board of Trade to deal with the collection of weather data at sea as a service to mariners; this was the forerunner of the modern Meteorological Office. All ship captains were tasked with collating data on the weather and computing it, with the use of tested instruments that were loaned for this purpose. A storm in 1859 that caused the loss of the Royal Charter inspired FitzRoy to develop charts to allow predictions to be made, which he called "forecasting the weather", thus coining the term "weather forecast". Fifteen land stations were established to use the telegraph to transmit to him daily reports of weather at set times leading to the first gale warning service.
His warning service for shipping was initiated in February 1861, with the use of telegraph communications. The first daily weather forecasts were published in The Times in 1861. In the following year a system was introduced of hoistin
Tracking and data relay satellite
A tracking and data relay satellite is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System used by NASA and other United States government agencies for communications to and from independent "User Platforms" such as satellites, aircraft, the International Space Station, remote bases like the Amundsen-Scott South Pole Station. This system was designed to replace an existing worldwide network of ground stations that had supported all of NASA's crewed flight missions and uncrewed satellites in low-Earth orbits; the primary system design goal was to increase the amount of time that these spacecraft were in communication with the ground and improve the amount of data that could be transferred. These TDRSS satellites are all designed and built to be launched to and function in geosynchronous orbit, 35,786 km above the surface of the Earth; the first seven TDRSS satellites were built by the TRW corporation. The three versions have been manufactured by the Boeing corporation's Satellite Systems division.
Ten satellites have been launched. TDRS-1 was decommissioned in October 2009. TDRS-4 was decommissioned in December 2011. Seven TDRSS satellites are still in service. All of the TDRSS satellites have been managed by NASA's Goddard Space Flight Center; the contract for TDRS versions L & K was awarded to Boeing on December 20, 2007. On November 30, 2011, NASA announced the decision to order an additional third-generation TDRS satellite, TDRS M; the first tracking and data relay satellite was launched in 1983 on the Space Shuttle Challenger's first flight, STS-6. The Boeing-built Inertial Upper Stage, to take the satellite from Challenger's orbit to its ultimate geosynchronous orbit suffered a failure that caused it not to deliver the TDRS to the correct orbit; as a result, it was necessary to command the satellite to use its onboard rocket thrusters to move it into its correct orbit. This expenditure of fuel reduced its capability to remain in a geostationary orbit; the second tracking and data relay satellite was destroyed along with Challenger shortly after launch during the STS-51-L mission in January 1986.
The next five TRW-built TDRSS satellites were launched on other Space Shuttles. Three follow-up Boeing-built satellites were launched by Atlas rockets in 2000 and 2002. A NASA Press Release summarized the capabilities of the system as a whole: "Working solo, TDRS-1 provided more communication coverage, in support of the September 1983 Shuttle mission, than the entire network of NASA tracking stations had provided in all previous Shuttle missions." The first generation of TDRS are planned to be retired in 2015. The two TDRSS satellite ground terminals are located at NASA White Sands Complex, in the Las Cruces area. All radioed commands and received telemetry that go to and from the tracking and data relay satellites go by way of these terminals at the White Sands Complex. At first, just one large ground terminal system for the TDRSS was built. However, some years due to increased user demand NASA ordered the design and construction of a second ground terminal system about 5 kilometres away. Thus, there are now two functionally identical and redundant satellite ground terminals there, which are known as the White Sands Complex.
Due to a Zone of Exclusion, no user support over the Indian Ocean, a ground terminal was built in Guam to support TDRS. The bilateration ranging transponder system provides tracking support for TDRS spacecraft. BRTS consists of four sites located at White Sands Missile Range, Ascension Island, Alice Springs, Australia; the communications systems of the TDRSS satellites were designed to support multiple missions at the same time. Each satellite has S band, Ku band, Ka band electronic communication systems hardware that operate at different carrier frequencies and support various data-rates; the newer Boeing satellites are able to support more communications than the older TRW-built satellites. Section source: NASA TDRSS official siteFirst generation TDRS: models A to G Second generation TDRS: models H to J Third generation TDRS: models K to M Launch site: Cape Canaveral, United States Launch vehicle: Space shuttle, Atlas II or Atlas V booster Mass: 2108.0 kg Nominal power: 1700.0 W Sub-section source: NSSDC Master Catalog Display: Spacecraft Note: while a TDRSS satellite is in the manufacturing process it is given a letter designation, but once it has achieved the correct geosynchronous orbit it is referred to with a number.
Thus, satellites that are lost in launch failures or have massive malfunctions are never numbered. Source: NASA: TDRS; the system is a concept utilizing communication satellite technology that improves and economizes the satellite tracking and telemetry operations. The base three geosynchronous satellites track and receive data from satellites for relay to a ground station; the two primary active satellites are separated in orbit by at least 130 degrees longitude. One system is used for tracking satellites with apogees below 2000 km, the other for those with higher apogees. Use of operating frequencies near 2150 (
A Mars rover is a motor vehicle that travels across the surface of the planet Mars upon arrival. Rovers have several advantages over stationary landers: they examine more territory, they can be directed to interesting features, they can place themselves in sunny positions to weather winter months, they can advance the knowledge of how to perform remote robotic vehicle control. Mars There have been four successful robotically operated Mars rovers, all managed by the Jet Propulsion Laboratory: Sojourner, Opportunity and Curiosity. On January 24, 2016, NASA reported that current studies on Mars by Curiosity and Opportunity would be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments that may have been habitable; the search for evidence of habitability and organic carbon on Mars is now a primary NASA objective. In June 2018, Opportunity went out of contact after going into hibernation mode in a dust storm.
NASA declared the Opportunity mission ended on February 13, 2019, after numerous failures to wake up the rover from the repeated signals. Mars 2, Mars 3 were physically tethered probes; as of February 2019, Curiosity is still active, while Spirit and Sojourner completed their missions before losing contact. Six rovers have been dispatched to Mars: Mars 2, Prop-M rover, 1971, Mars 2 landing failed taking Prop-M with it; the Mars 2 and 3 spacecraft from the Soviet Union had identical 4.5 kg Prop-M rovers. They were to move on skis. Mars 3, Prop-M rover, 1971, lost when Mars 3 lander stopped communicating about 20 seconds after landing. Sojourner rover, Mars Pathfinder, landed on July 4, 1997. Communications were lost on September 27, 1997. Spirit, Mars Exploration Rover, launched on June 10, 2003, landed on January 4, 2004. Nearly 6 years after the original mission limit, Spirit had covered a total distance of 7.73 km but its wheels became trapped in sand. The last communication received from the rover was on March 22, 2010, NASA ceased attempts to re-establish communication on May 25, 2011.
Opportunity, Mars Exploration Rover, launched on July 7, 2003 and landed on January 25, 2004. Opportunity surpassed the previous records for longevity at 5,352 sols and covered a total distance of 40.25 km. The rover sent its last status on 10 June 2018 when a global 2018 Mars dust storm blocked the sunlight needed to recharge its batteries. After hundreds of attempts to reactivate the rover, NASA declared the mission complete on February 13, 2019. Curiosity of the Mars Science Laboratory mission by NASA, was launched November 26, 2011 and landed at the Aeolis Palus plain near Aeolis Mons in Gale Crater on August 6, 2012; the Curiosity rover is still operational as of April 13, 2019. Rosalind Franklin, the European-Russian ExoMars rover to launch in 2020 Mars 2020, a NASA rover to launch in 2020 Mars Global Remote Sensing Orbiter and Small Rover, a Chinese project Astrobiology Field Laboratory, proposed in the 2000-2010 period as a follow on to MSL. Mars Astrobiology Explorer-Cacher, cancelled 2011 Mars Surveyor 2001 rover, Zephyr rover, would use a rigid sail for wind propulsion.
Mars Tumbleweed Rover, a spherical wind-propelled rover. In 2018, a kind of cushion-air rover was proposed, which in contrast with traditional hovercrafts does not use blowers to pressurize the gas in the chamber but rather uses stored pressurized CO2 obtained from a freezing process which does not require mechanical compression. Examples of instruments onboard landed rovers include: Alpha particle X-ray spectrometer CheMin Chemistry and Camera complex Dynamic Albedo of Neutrons Hazcam MarsDial Materials Adherence Experiment MIMOS II Mini-TES Mars Hand Lens Imager Navcam Pancam Rock Abrasion Tool Radiation assessment detector Rover Environmental Monitoring Station Sample Analysis at Mars NASA distinguishes between "mission" objectives and "science" objectives. Mission objectives are related to progress in space development processes. Science objectives are met by the instruments during their mission in space; the science instruments are designed based on the science objectives and goals. The primary goal of the Spirit and Opportunity rovers was to investigate "the history of water on Mars".
The four science goals of NASA's long-term Mars Exploration Program are: Determine whether life arose on Mars Characterize the climate of Mars Characterize the geology of Mars Prepare for human exploration of Mars NASA official Mars Rover website Mars Pathfinder Gallery
A spaceplane is an aerospace vehicle that operates as an aircraft in Earth's atmosphere, as well as a spacecraft when it is in space. It combines features of an aircraft and a spacecraft, which can be thought of as an aircraft that can endure and maneuver in the vacuum of space or a spacecraft that can fly like an airplane, it takes the form of a spacecraft equipped with wings, although lifting bodies have been designed and tested as well. The propulsion to reach space may be purely rocket based or may use the assistance of airbreathing jet engines; the spaceflight is followed by an unpowered glide return to landing. Five kinds of spaceplanes have flown to date, having reentered Earth's atmosphere, returned to Earth, safely landed — the North American X-15, Space Shuttle, SpaceShipOne, Boeing X-37. All five are considered rocket gliders; as of 2015, only these aircraft and rockets have succeeded in reaching space. Two of these five are rocket-powered aircraft, having been carried up to an altitude of several tens of thousands of feet by an atmospheric mother ship before being released, flying beyond the Kármán line, the boundary of Earth's atmosphere, under their own power.
Three are vertical takeoff horizontal landing vehicles relying upon rocket lift for the ascent phase in reaching space and atmospheric lift for reentry and landing. The three VTHL spaceplanes flew much further than the aircraft launched ones, not leaving Earth's atmosphere but entering orbit around it, which requires at least 50 times more energy on the way up and heavy heat shielding for the trip back. Of the five vehicles, three have been piloted by astronauts, with the Buran and X-37 flying unmanned missions. Significant features distinguish spaceplanes from traditional spacecraft. All aircraft utilize aerodynamic surfaces. For spaceplanes a variety of wing shapes can be used. Delta wings are common, but straight wings, lifting bodies and rotorcraft have been proposed; the force of lift generated by these surfaces is many times that of the drag that they induce. Because suborbital spaceplanes are designed for trajectories that do not reach orbital speed, they do not need the kinds of thermal protection orbital spacecraft required during the hypersonic phase of atmospheric reentry.
The Space Shuttle thermal protection system, for example, protects the orbiter from surface temperatures that could otherwise reach as high as 1,650 °C, well above the melting point of steel. A spaceplane operates as an aircraft in Earth's atmosphere. Aircraft may land on firm runways, helicopter landing pads, or water, snow or ice. To land, the airspeed and the rate of descent are reduced such that the aircraft descends at a slow enough rate to allow for a gentle touch down. Landing is accomplished by descending; this speed reduction is accomplished by reducing thrust and/or inducing a greater amount of drag using flaps, landing gear or speed brakes. Splashdown is an easier technical feat to accomplish, requiring only the deployment of a parachute, rather than aviating the atmosphere. Project Gemini's original concept design was with paraglider and wheels attached. However, this concept was abandoned in favor of parachute splashdowns, because of expensive technical failures during testing and development.
Whereas Project Gemini's splashdown parachutes took only 5 months to develop in 1963, Gemini's spaceplane concept failed to materialize after nearly 3 years of continued development. All spaceplanes to date have used rocket engines with chemical fuels; as the orbital insertion burn has to be done in space, orbital spaceplanes require rocket engines for at least that portion of the flight. A difference between rocket based and air-breathing aerospace plane launch systems is that aerospace plane designs include minimal oxidizer storage for propulsion. Air-breathing aerospace plane designs include engine inlets so they can use atmospheric oxygen for combustion. Since the mass of the oxidizer is, at takeoff, the single largest mass of most rocket designs, this provides a huge potential weight savings benefit. However, air breathing engines are very much heavier than rocket engines and the empty weight of the oxidizer tank, since, unlike oxidizer, this extra weight must be carried into space it may offset the overall system performance.
Types of air breathing engines proposed for spaceplanes include scramjet, liquid air cycle engines, precooled jet engines, pulse detonation engine and ramjets. Some engine designs combine several types of engines features into a combined cycle. For instance, the Rocket-based combined cycle engine uses a rocket engine inside a ramscoop so that at low speed, the rockets thrust is boosted by ejector augmented thrust, it transitions to ramjet propulsion at near-supersonic speeds to supersonic combustion or scramjet propulsion, above Mach 6 back to pure rocket propulsion above Mach 10. The flight trajectory required of air-breathing aerospace vehicles to reach orbit is to fly what is known as a'depressed trajectory' which places the aerospace plane in the high-altitude hypersonic flight regime of the atmosphere; this environment induces high dynamic pressure, high temperature, high heat flow loads upon the leading edge surfaces of the aerospace plane. These loads require special advanced materials, active cooling, or both, for the structures to sur