In spacecraft propulsion, a Hall-effect thruster is a type of ion thruster in which the propellant is accelerated by an electric field. Hall-effect thrusters trap electrons in a magnetic field and use the electrons to ionize propellant, efficiently accelerate the ions to produce thrust, neutralize the ions in the plume. Hall-effect thrusters are sometimes referred to Hall-current thrusters. Hall thrusters are regarded as a moderate specific impulse space propulsion technology; the Hall-effect thruster has benefited from considerable theoretical and experimental research since the 1960s. Hall thrusters operate on a variety of the most common being xenon. Other propellants of interest include krypton, bismuth, iodine and zinc. Hall thrusters are able to accelerate their exhaust to speeds between 10 and 80 km/s, with most models operating between 15 and 30 km/s; the thrust produced by a Hall thruster varies depending on the power level. Devices operating at 1.35 kW produce about 83 mN of thrust. High-power models have demonstrated up to 5.4 N in the laboratory.
Power levels up to 100 kW have been demonstrated by xenon Hall thrusters. As of 2009, Hall-effect thrusters ranged in input power levels from 1.35 to 10 kilowatts and had exhaust velocities of 10–50 kilometers per second, with thrust of 40–600 millinewtons and efficiency in the range of 45–60 percent. The applications of Hall-effect thrusters include control of the orientation and position of orbiting satellites and use as a main propulsion engine for medium-size robotic space vehicles. Hall thrusters were studied independently in the Soviet Union, they were first described publicly in the US in the early 1960s. However, the Hall thruster was first developed into an efficient propulsion device in the Soviet Union. In the US, scientists focused instead on developing gridded ion thrusters. Two types of Hall thrusters were developed in the Soviet Union: thrusters with wide acceleration zone, SPT at Design Bureau Fakel thrusters with narrow acceleration zone, DAS, at the Central Research Institute for Machine Building.
The SPT design was the work of A. I. Morozov; the first SPT to operate in space, an SPT-50 aboard a Soviet Meteor spacecraft, was launched December 1971. They were used for satellite stabilization in North-South and in East-West directions. Since until the late 1990s 118 SPT engines completed their mission and some 50 continued to be operated. Thrust of the first generation of SPT engines, SPT-50 and SPT-60 was 30 mN respectively. In 1982, SPT-70 and SPT-100 were introduced, their thrusts being 83 mN, respectively. In the post-Soviet Russia high-power SPT-140, SPT-160, SPT-200, T-160 and low-power SPT-35 were introduced. Soviet and Russian TAL-type thrusters include the D-38, D-55, D-80, D-100. Soviet-built thrusters were introduced to the West in 1992 after a team of electric propulsion specialists from NASA's Jet Propulsion Laboratory, Glenn Research Center, the Air Force Research Laboratory, under the support of the Ballistic Missile Defense Organization, visited Russian laboratories and experimentally evaluated the SPT-100.
Over 200 Hall thrusters have been flown on Soviet/Russian satellites in the past thirty years. No failures have occurred on orbit. Hall thrusters continue to be used on Russian spacecraft and have flown on European and American spacecraft. Space Systems/Loral, an American commercial satellite manufacturer, now flies Fakel SPT-100's on their GEO communications spacecraft. Since their introduction to the west in the early 1990s, Hall thrusters have been the subject of a large number of research efforts throughout the United States, Italy and Russia. Hall thruster research in the US is conducted at several government laboratories and private companies. Government and government funded centers include NASA's Jet Propulsion Laboratory, NASA's Glenn Research Center, the Air Force Research Laboratory, The Aerospace Corporation. Universities include the US Air Force Institute of Technology, University of Michigan, Stanford University, The Massachusetts Institute of Technology, Princeton University, Michigan Technological University, Georgia Tech.
A considerable amount of development is being conducted in industry, such as IHI Corporation in Japan and Busek in the USA, SNECMA in France, LAJP in Ukraine, SITAEL in Italy. The first use of Hall thrusters on lunar orbit was the European Space Agency lunar mission SMART-1 in 2003. On a western satellite Hall thrusters were first demonstrated on the Naval Research Laboratory STEX spacecraft, which flew the Russian D-55; the first American Hall thruster to fly in space was the Busek BHT-200 on TacSat-2 technology demonstration spacecraft. The first flight of an American Hall thruster on an operational mission, was the Aerojet BPT-4000, which launched August 2010 on the military Advanced Extremely High Frequency GEO communications satellite. At 4.5 kW, the BPT-4000 is the highest power Hall thruster flown in space. Besides the usual stationkeeping tasks, the BPT-4000 is providing orbit raising capability to the spacecraft. Several countries worldwide continue efforts to qualify Hall thruster technology for commercial uses.
The essential working principle of the Hall thruste
Reaction control system
A reaction control system is a spacecraft system that uses thrusters to provide attitude control, sometimes translation. Use of diverted engine thrust to provide stable attitude control of a short-or-vertical takeoff and landing aircraft below conventional winged flight speeds, such as with the Harrier "jump jet", may be referred to as a reaction control system. An RCS is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is capable of providing torque to allow control of rotation. Reaction control systems use combinations of large and small thrusters, to allow different levels of response. Spacecraft reaction control systems are used for: attitude control during re-entry; because spacecraft only contain a finite amount of fuel and there is little chance to refill them, alternative reaction control systems have been developed so that fuel can be conserved. For stationkeeping, some spacecraft use high-specific impulse engines such as arcjets, ion thrusters, or Hall effect thrusters.
To control orientation, a few spacecraft, including the ISS, use momentum wheels which spin to control rotational rates on the vehicle. The Mercury space capsule and Gemini re-entry module both used groupings of nozzles to provide attitude control; the thrusters were located off their center of gravity, thus providing a torque to rotate the capsule. The Gemini capsule was capable of adjusting its re-entry course by rolling, which directed its off-center lifting force; the Mercury thrusters used a hydrogen peroxide monopropellant which turned to steam when forced through a tungsten screen, the Gemini thrusters used hypergolic mono-methyl hydrazine fuel oxidized with nitrogen tetroxide. The Gemini spacecraft was equipped with a hypergolic Orbit Attitude and Maneuvering System, which made it the first manned spacecraft with translation as well as rotation capability. In-orbit attitude control was achieved by firing pairs of eight 25-pound-force thrusters located around the circumference of its adapter module at the extreme aft end.
Lateral translation control was provided by four 100-pound-force thrusters around the circumference at the forward end of the adaptor module. Two forward-pointing 85-pound-force thrusters at the same location, provided aft translation, two 100-pound-force thrusters located in the aft end of the adapter module provided forward thrust, which could be used to change the craft's orbit; the Apollo Command Module had a set of twelve hypergolic thrusters for attitude control, directional re-entry control similar to Gemini. The Apollo Service Module and Lunar Module each had a set of sixteen R-4D hypergolic thrusters, grouped into external clusters of four, to provide both translation and attitude control; the clusters were located near the craft's centers of gravity, were fired in pairs in opposite directions for attitude control. A pair of translation thrusters are located at the rear of the Soyuz spacecraft; these act in pairs to prevent the spacecraft from rotating. The thrusters for the lateral directions are mounted close to the center of mass of the spacecraft, in pairs as well.
The suborbital X-15 and a companion training aero-spacecraft, the NF-104 AST, both intended to travel to an altitude that rendered their aerodynamic control surfaces unusable, established a convention for locations for thrusters on winged vehicles not intended to dock in space. Those for pitch and yaw are located in the nose, forward of the cockpit, replace a standard radar system; those for roll are located at the wingtips. The X-20, which would have gone into orbit, continued this pattern. Unlike these, the Space Shuttle Orbiter had many more thrusters, as it was required to carry out docking maneuvers in orbit. Shuttle thrusters were grouped in the nose of the vehicle and on each of the two aft Orbital Maneuvering System pods. No nozzles interrupted the heat shield on the underside of the craft; the downward-facing negative pitch thrusters were located in the OMS pods mounted in the tail/afterbody. The International Space Station uses electrically powered reaction control gyroscopes for primary attitude control, with RCS thruster systems as backup and augmentation systems.
Space Shuttle RCS Jet Aerospace: Mono-fuel RCS thruster
Pulsed plasma thruster
A pulsed plasma thruster known as a plasma jet engine, is a form of electric spacecraft propulsion. PPTs are considered the simplest form of electric spacecraft propulsion and were the first form of electric propulsion to be flown in space, having flown on two Soviet probes starting in 1964. PPTs are flown on spacecraft with a surplus of electricity from abundantly available solar energy. Most PPTs use a solid material for propellant, although few use liquid or gaseous propellants; the first stage in PPT operation involves an arc of electricity passing through the fuel, causing ablation and sublimation of the fuel. The heat generated by this arc causes the resultant gas to turn into plasma, thereby creating a charged gas cloud. Due to the force of the ablation, the plasma is propelled at low speed between two charged plates. Since the plasma is charged, the fuel completes the circuit between the two plates, allowing a current to flow through the plasma; this flow of electrons generates a strong electromagnetic field which exerts a Lorentz force on the plasma, accelerating the plasma out of the PPT exhaust at high velocity.
Its mode of operation is similar to a railgun. The pulsing occurs due to the time needed to recharge the plates following each burst of fuel, the time between each arc; the frequency of pulsing is very high and so it generates an continuous and smooth thrust. While the thrust is low, a PPT can operate continuously for extended periods of time, yielding a large final speed; the energy used in each pulse is stored in a capacitor. By varying the time between each capacitor discharge, the thrust and power draw of the PPT can be varied allowing versatile use of the system; the equation for the change in velocity of a spacecraft is given by the rocket equation as follows: Δ v = v e ln m 0 m 1 where: Δ v is delta-v - the maximum change of speed of the vehicle, v e is the effective exhaust velocity, ln refers to the natural logarithm function, m 0 is the initial total mass, including propellant, m 1 is the final total mass. PPTs have much higher exhaust velocities than chemical propulsion engines, but have a much smaller fuel flow rate.
From the Tsiolkovsky equation stated above, this results in a proportionally higher final velocity of the propelled craft. The exhaust velocity of a PPT is of the order of tens of km/s while conventional chemical propulsion generates thermal velocities in the range of 2–4.5 km/s. Due to this lower thermal velocity, chemical propulsion units become exponentially less effective at higher vehicle velocities, necessitating the use of electric spacecraft propulsion such as PPTs, it is therefore advantageous to use an electric propulsion system such as a PPT to generate high interplanetary speeds in the range 20–70 km/s. NASA's research PPT achieved an exhaust velocity of 13,700 m/s, generated a thrust of 860 µN, consumed 70 W of electrical power. PPTs are robust due to their inherently simple design; as an electric propulsion system, PPTs benefit from reduced fuel consumption compared to traditional chemical rockets, reducing launch mass and therefore launch costs, as well as high specific impulse improving performance.
However, due to energy losses caused by late time ablation and rapid conductive heat transfer from the propellant to the rest of the spacecraft, propulsive efficiency is low compared to other forms of electric propulsion, at around just 10%. PPTs are well-suited to uses on small spacecraft with a mass of less than 100 kg for roles such as attitude control, station keeping, de-orbiting manoeuvres and deep space exploration. Using PPTs could double the life-span of these small satellite missions without increasing complexity or cost due to the inherent simplicity and low cost nature of PPTs; the first use of PPTs was on the Soviet Zond 2 space probe on 30 November 1964. A PPT was flown by NASA in November, 2000, as a flight experiment on the Earth Observing-1 spacecraft; the thrusters demonstrated the ability to perform roll control on the spacecraft and demonstrated that the electromagnetic interference from the pulsed plasma did not affect other spacecraft systems. Pulsed Plasma Thrusters are an avenue of research used by universities for starting experiments with electric propulsion due to the relative simplicity and lower costs involved with PPTs as opposed to other forms of electric propulsion such as Hall-effect ion thrusters.
Design of a High-energy, Two-stage Pulsed Plasma Thruster EO1 Pulsed Plasma Thruster Gas-Fed Pulsed Plasma Thrusters: From Sparks to Laser Initiation
A magnetoplasmadynamic thruster is a form of electrically powered spacecraft propulsion which uses the Lorentz force to generate thrust. It is sometimes referred to as Lorentz Force MPD arcjet. A gaseous material is ionized and fed into an acceleration chamber, where the magnetic and electrical fields are created using a power source; the particles are propelled by the Lorentz force resulting from the interaction between the current flowing through the plasma and the magnetic field out through the exhaust chamber. Unlike chemical propulsion, there is no combustion of fuel; as with other electric propulsion variations, both specific impulse and thrust increase with power input, while thrust per watt drops. There are two main types of MPD thrusters, self-field. Applied-field thrusters have magnetic rings surrounding the exhaust chamber to produce the magnetic field, while self-field thrusters have a cathode extending through the middle of the chamber. Applied fields are necessary at lower power levels.
Various propellants such as xenon, argon, hydrogen and lithium have been used, with lithium being the best performer. According to Edgar Choueiri magnetoplasmadynamic thrusters have input power 100–500 kilowatts, exhaust velocity 15–60 kilometers per second, thrust 2.5–25 newtons and efficiency 40–60 percent. One potential application of magnetoplasmadynamic thrusters is the main propulsion engine for heavy cargo and piloted space vehicles. In theory, MPD thrusters could produce high specific impulses with an exhaust velocity of up to and beyond 110000 m/s, triple the value of current xenon-based ion thrusters, about 25 times better than liquid rockets. MPD technology has the potential for thrust levels of up to 200 newtons, by far the highest for any form of electric propulsion, nearly as high as many interplanetary chemical rockets; this would allow use of electric propulsion on missions which require quick delta-v maneuvers, but with many times greater fuel efficiency. MPD thruster technology has been explored academically, but commercial interest has been low due to several remaining problems.
One big problem is that power requirements on the order of hundreds of kilowatts are required for optimum performance. Current interplanetary spacecraft power systems are incapable of producing that much power. NASA's Project Prometheus reactor was expected to generate power in the hundreds of kilowatts range but was discontinued in 2005. A project to produce a space-going nuclear reactor designed to generate 600 kilowatts of electrical power began in 1963 and ran for most of the 1960s in the USSR, it was to power a communication satellite, in the end not approved. Nuclear reactors supplying kilowatts of electrical power have been orbited by the USSR: RORSAT. Plans to develop a megawatt-scale nuclear reactor for the use aboard a manned spaceship were announced in 2009 by Russian nuclear Kurchatov Institute, national space agency Roskosmos, confirmed by Russian President Dmitry Medvedev in his November 2009 address to the Federal Assembly. Another plan, proposed by Bradley C. Edwards, is to beam power from the ground.
This plan utilizes 5 200 kW free electron lasers at 0.84 micrometres with adaptive optics on the ground to beam power to the MPD-powered spacecraft, where it is converted to electricity by GaAs photovoltaic panels. The tuning of the laser wavelength of 0.840 micrometres and the PV panel bandgap of 1.43 eV to each other produces an estimated conversion efficiency of 59% and a predicted power density of up to 540 kW/m2. This would be sufficient to power a MPD upper stage to lift satellites from LEO to GEO. Another problem with MPD technology has been the degradation of cathodes due to evaporation driven by high current densities; the use of lithium and barium propellant mixtures and multi-channel hollow cathodes has been shown in the laboratory to be a promising solution for the cathode erosion problem. Research on MPD thrusters has been carried out in the US, the former Soviet Union, Japan and Italy. Experimental prototypes were first flown on Soviet spacecraft and, most in 1996, on the Japanese Space Flyer Unit, which demonstrated the successful operation of a quasi-steady pulsed MPD thruster in space.
Research at Moscow Aviation Institute, RKK Energiya, National Aerospace University, Kharkiv Aviation Institute, University of Stuttgart, ISAS, Alta S.p. A. Osaka University, University of Southern California, Princeton University's Electric Propulsion and Plasma Dynamics Lab, NASA centers, has resolved many problems related to the performance and lifetime of MPD thrusters. An MPD thruster was tested on board the Japanese Space Flyer Unit as part of EPEX, launched March 18, 1995 and retrieved by space shuttle mission STS-72 January 20, 1996. To date, it is the only operational MPD thruster to have flown in space as a propulsion system. Hall effect thruster Ion thruster Magnetohydrodynamics Magnetic sail Pulsed plasma thruster Solar panels on spacecraft Spacecraft propulsion VASIMR
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, navigation, space colonization, planetary exploration, transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, require a launch vehicle. On a sub-orbital spaceflight, a space vehicle enters space and 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 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, 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, the United States, the member states of the European Space Agency, China, Taiwan (National Chung-Shan Institute of Science and Technology, Taiwan National Space Organization, Israel and North Korea. A German V-2 became the first spacecraft when it reached an altitude of 189 km in June 1944 in Peenemünde, Germany. Sputnik 1 was the first artificial satellite, it was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957. The launch ushered in new political, military and scientific developments. Apart from its value as a technological first, Sputnik 1 helped to identify the upper atmospheric layer's density, through measuring the satellite's orbital changes.
It 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. The satellite travelled at 29,000 kilometers per hour, taking 96.2 minutes to complete an orbit, 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 reached an altitude of 100 km, 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 crewed spacecraft: USSR/Russia, USA, China. The first crewed spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, completed a full Earth orbit.
There were five other crewed missions. The second crewed spacecraft was named Freedom 7, it performed a sub-orbital spaceflight in 1961 carrying American astronaut Alan Shepard to an altitude of just over 187 kilometers. There were five other crewed missions using Mercury spacecraft. Other Soviet crewed spacecraft include the Voskhod, flown uncrewed as Zond/L1, L3, TKS, the Salyut and Mir crewed space stations. Other American crewed spacecraft include the Gemini spacecraft, Apollo spacecraft, the Skylab space station, the Space Shuttle with undetached European Spacelab and private US Spacehab space stations-modules. China developed, but did not fly Shuguang, is using Shenzhou. Except for the Space Shuttle, all of the recoverable crewed orbital spacecraft were space capsules. Crewed space capsules The International Space Station, crewed since November 2000, is a joint venture between Russia, the United States and several other countries; some reusable vehicles have been designed only for crewed spaceflight, these are 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 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 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 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 resembled the U
Space Shuttle Atlantis
Space Shuttle Atlantis is a Space Shuttle orbiter vehicle belonging to the National Aeronautics and Space Administration, the spaceflight and space exploration agency of the United States. Constructed by the Rockwell International company in Southern California and delivered to the Kennedy Space Center in Eastern Florida in April 1985, Atlantis is the fourth operational and the second-to-last Space Shuttle built, its maiden flight was STS-51-J from 3 to 7 October 1985. Atlantis embarked on its 33rd and final mission the final mission of a space shuttle, STS-135, on 8 July 2011. STS-134 by Endeavour was expected to be the final flight before STS-135 was authorized in October 2010. STS-135 took advantage of the processing for the STS-335 Launch On Need mission that would have been necessary if STS-134's crew became stranded in orbit. Atlantis landed for the final time at the Kennedy Space Center on 21 July 2011. By the end of its final mission, Atlantis had orbited the Earth a total of 4,848 times, traveling nearly 126,000,000 mi or more than 525 times the distance from the Earth to the Moon.
Atlantis is named after RV Atlantis, a two-masted sailing ship that operated as the primary research vessel for the Woods Hole Oceanographic Institution from 1930 to 1966. Weight: 151,315 pounds Length: 122.17 feet Height: 56.58 feet Wingspan: 78.06 feet Atlantis was completed in about half the time it took to build Space Shuttle Columbia. When it rolled out of the Palmdale assembly plant, weighing 151,315 lb, Atlantis was nearly 3.5 short tons lighter than Columbia. Atlantis is the lightest shuttle of the remaining fleet, weighing 20,685 pounds less than the Space Shuttle Endeavour. Space Shuttle Atlantis lifted off on its maiden voyage on 3 October 1985, on mission STS-51-J, the second dedicated Department of Defense flight, it flew one other mission, STS-61-B, the second night launch in the shuttle program, before the Space Shuttle Challenger disaster temporarily grounded the Shuttle fleet in 1986. Among the five Space Shuttles flown into space, Atlantis conducted a subsequent mission in the shortest time after the previous mission when it launched in November 1985 on STS-61-B, only 50 days after its previous mission, STS-51-J in October 1985.
Atlantis was used for ten flights between 1988 and 1992. Two of these, both flown in 1989, deployed the planetary probes Magellan to Venus and Galileo to Jupiter. With STS-30 Atlantis became the first shuttle to launch an interplanetary probe. During another mission, STS-37 flown in 1991, Atlantis deployed the Compton Gamma Ray Observatory. Beginning in 1995 with STS-71, Atlantis made seven straight flights to the former Russian space station Mir as part of the Shuttle-Mir Program. STS-71 marked a number of firsts in human spaceflight: 100th U. S. manned space flight. S. Shuttle-Russian Space Station Mir joint on-orbit operations; when linked and Mir together formed the largest spacecraft in orbit at the time. Shuttle Atlantis delivered several vital components for the construction of the International Space Station. During the February 2001 mission STS-98 to the ISS, Atlantis delivered the Destiny Module, the primary operating facility for U. S. research payloads aboard the ISS. The five hour 25 minute third spacewalk performed by astronauts Robert Curbeam and Thomas Jones during STS-98 marked NASA's 100th extra vehicular activity in space.
The Quest Joint Airlock, was flown and installed to the ISS by Atlantis during the mission STS-104 in July 2001. The successful installation of the airlock gave on-board space station crews the ability to stage repair and maintenance spacewalks outside the ISS using U. S. EMU or Russian Orlan space suits; the first mission flown by Atlantis after the Space Shuttle Columbia disaster was STS-115, conducted during September 2006. The mission carried the P3/P4 truss segments and solar arrays to the ISS. On ISS assembly flight STS-122 in February 2008, Atlantis delivered the Columbus laboratory to the ISS. Columbus laboratory is the largest single contribution to the ISS made by the European Space Agency. In May 2009 Atlantis flew a seven-member crew to the Hubble Space Telescope for its Servicing Mission 4, STS-125; the mission was a success, with the crew completing five spacewalks totalling 37 hours to install new cameras, batteries, a gyroscope and other components to the telescope. This was the final mission not to the ISS.
The longest mission flown using Atlantis was STS-117 which lasted 14 days in June 2007. During STS-117, Atlantis' crew added a new starboard truss segment and solar array pair, folded the P6 array in preparation for its relocation and performed four spacewalks. Atlantis was not equipped to take advantage of the Station-to-Shuttle Power Transfer System so missions could not be extended by making use of power provided by ISS. During the STS-129 post-flight interview on 16 November 2009, shuttle launch director Mike Leinbach said that Atlantis beat Space Shuttle Discovery for the record low amount of Interim Problem Reports, with a total of just 54 listed since returning from STS-125, he continued to add "It is due to the hardware processing. They just did a great job; the record will never be broken again in the history of the Space Shuttle Program, so congratulations to them". During the STS-132 post-launch interview on 14 May 2010, Shuttle launch director Mike Leinbach said that Atlantis beat its own previous record low amount of Interim Problem Reports, with a total of 46 listed between STS-129 and STS-132.
Atlantis went through t
Stellar engines are a class of hypothetical megastructures which use a star's radiation to create usable energy. Some variants use this energy to produce thrust, thus accelerate a star, anything orbiting it, in a given direction; the creation of such a system would make its builders a Type-II civilization on the Kardashev scale. There are three variant classes of this idea. One of the simplest examples of stellar engine is a Class A stellar engine; such an engine is a stellar propulsion system, consisting of an enormous mirror/light sail—actually a massive type of solar statite large enough to classify as a megastructure by an order of magnitude—which would balance gravitational attraction towards and radiation pressure away from the star. Since the radiation pressure of the star would now be asymmetrical, i.e. more radiation is being emitted in one direction as compared to another, the'excess' radiation pressure acts as net thrust, accelerating the star in the direction of the hovering statite.
Such thrust and acceleration would be slight, but such a system could be stable for millennia. Any planetary system attached to the star would be'dragged' along by its parent star. For a star such as the Sun, with luminosity 3.85 × 1026 W and mass 1.99 × 1030 kg, the total thrust produced by reflecting half of the solar output would be 1.28 × 1018 N. After a period of one million years this would yield an imparted speed of 20 m/s, with a displacement from the original position of 0.03 light-years. After one billion years, the speed would be 20 km/s and the displacement 34,000 light-years, a little over a third of the estimated width of the Milky Way galaxy. A Class B stellar engine is a Dyson sphere—of whichever variant—built around the star, which uses the difference in temperature between the star and the interstellar medium to extract usable energy from the system using heat engines or photovoltaic cells. Unlike the Shkadov thruster, such a system is not propulsive. A Class C stellar engine combines the two other classes, employing both the propulsive aspects of the Shkadov thruster, the energy generating aspects of a Class B engine.
A Dyson shell with an inner surface covered by a mirror would be one incarnation of such a system, as would be a Dyson swarm with a large statite mirror. A Dyson bubble variant is a Shkadov thruster. In Olaf Stapledon's 1937 science fiction novel Star Maker, some advanced galactic civilizations attempt to use stellar engines to propel their planetary systems across the galaxy in order to physically contact other advanced galactic civilizations. However, it turns out that the stars are life forms with a consciousness of their own, their consciousnesses are upset by this happening to them, because it violates the canon of the galactic ballet dance the stars feel they are a part of and which the stars feel is the primary focus and most sacred ritual of their lives. So, those stars whose surrounding civilizations attempt to force them to move in a different direction take revenge by committing suicide by exploding as supernovae, thus destroying their attendant worlds; this initiates the War of Stars and Worlds, lasting millions of years, which becomes a pivotal event in the history of the galaxy.
The war only ends when the galactic civilizations figure out how to telepathically communicate with the stars and arrange a truce. The novel Manifold: Space by Stephen Baxter has a Shkadov thruster being built around a neutron star, destined to collide with another neutron star; the novel Bowl of Heaven by Larry Niven and Gregory Benford describes a bowl shaped megastructure that uses magnetic fields to cause its star to emit a plasma jet, which moves the star accompanied by the megastructure. The film Avengers: Infinity War in the Marvel Cinematic Universe has a series of scenes that take place at Nidavellir, a stellar engine used as a weapons forge. Dyson spheres in popular culture