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Pulsed Plasma Thruster
A pulsed plasma thruster (PPT), also known as a plasma jet engine, is a form of electric spacecraft propulsion. PPTs are generally 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 (Zond 2 and Zond 3) starting in 1964. PPTs are generally flown on spacecraft with a surplus of electricity from abundantly available solar energy. Operation Most PPTs use a solid material (normally PTFE, more commonly known as Teflon) for propellant, although very 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 (an anode and cathode). Since the plasma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrically Powered Spacecraft Propulsion
Spacecraft electric propulsion (or just electric propulsion) is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generate thrust to modify the velocity of a spacecraft in orbit. The propulsion system is controlled by power electronics. Electric thrusters typically use much less propellant than chemical rockets because they have a higher exhaust speed (operate at a higher specific impulse) than chemical rockets.Choueiri, Edgar Y. (2009New dawn of electric rocket'' Scientific American'' 300, 58–65 Due to limited electric power the thrust is much weaker compared to chemical rockets, but electric propulsion can provide thrust for a longer time. Electric propulsion was first successfully demonstrated by NASA and is now a mature and widely used technology on spacecraft. American and Russian satellites have used electric propulsion for decades. , over 500 spacecraft operated throughout the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Exhaust Velocity
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is exactly proportional to the effective exhaust gas velocity. A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently. In the case of a rocket, this means less propellant needed for a given delta-v, so that the vehicle attached to the engine can more efficiently gain altitude and velocity. In an atmospheric context, specific impulse can include the contribution to impulse provided by the mass of external air that is accelerated by the engine in some way, such as by an internal turbofan or heating by fuel combustion participation then thrust expansion or by external propeller. Jet engines breathe external air for both combustion and by-pass, and therefore have a much higher specific impulse than r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Observing-1
Earth Observing-1 (EO-1) is a decommissioned NASA Earth observation satellite created to develop and validate a number of instrument and spacecraft bus breakthrough technologies. It was intended to enable the development of future Earth imaging observatories that will have a significant increase in performance while also having reduced cost and mass. The spacecraft was part of the New Millennium Program. It was the first satellite to map active lava flows from space; the first to measure a facility's methane leak from space; and the first to track re-growth in a partially logged Amazon forest from space. EO-1 captured scenes such as the ash after the World Trade Center attacks, the flooding in New Orleans after Hurricane Katrina, volcanic eruptions and a large methane leak in southern California. Overview Its Advanced Land Imager (ALI) measured nine different wavelengths simultaneously, instead of the seven measured by the imager in Landsat 7. This permitted a greater flexibility ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Probe
A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or enter interstellar space. Many countries and private companies have launched probes to planets, asteroids, moons around the Solar System, including the Soviet Union, the United States, India, and many more. History On 4 October 1957, the first artificial satellite to orbit Earth was Sputnik 1, launched by the USSR. Four months later, on 1 February 1958, Explorer 1 was launched by the United States, being the first space probe. Explorer 1, collecting data on temperature, cosmic rays, and micrometeorite impacts. The first attempted lunar probe was the Luna E-1 No.1, launched on 23 September 1958. The goal of a lunar probe repeatedly failed until 4 January 1959 when Luna 1 orbited around the moon and then the sun. The success of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soviet
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national republics; in practice, both its government and its economy were highly centralized until its final years. It was a one-party state governed by the Communist Party of the Soviet Union, with the city of Moscow serving as its capital as well as that of its largest and most populous republic: the Russian SFSR. Other major cities included Leningrad (Russian SFSR), Kiev (Ukrainian SSR), Minsk (Byelorussian SSR), Tashkent (Uzbek SSR), Alma-Ata (Kazakh SSR), and Novosibirsk (Russian SFSR). It was the largest country in the world, covering over and spanning eleven time zones. The country's roots lay in the October Revolution of 1917, when the Bolsheviks, under the leadership of Vladimir Lenin, overthrew the Russian Provisional Government that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Station-keeping
In astrodynamics, orbital station-keeping is keeping a spacecraft at a fixed distance from another spacecraft or celestial body. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its target. For many low Earth orbit satellites, the effects of non-Keplerian forces, i.e. the deviations of the gravitational force of the Earth from that of a homogeneous sphere, gravitational forces from Sun/Moon, solar radiation pressure and air drag, must be counteracted. The deviation of Earth's gravity field from that of a homogeneous sphere and gravitational forces from the Sun and Moon will in general perturb the orbital plane. For a sun-synchronous orbit, the precession of the orbital plane caused by the oblateness of the Earth is a desirable feature that is part of mission design but the inclination change caused by the gravitational forces of the Sun and Moon is undesirable. For geostationary spacecraft, the inclination change ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attitude Control
Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle attitude requires sensors to measure vehicle orientation, actuators to apply the torques needed to orient the vehicle to a desired attitude, and algorithms to command the actuators based on (1) sensor measurements of the current attitude and (2) specification of a desired attitude. The integrated field that studies the combination of sensors, actuators and algorithms is called guidance, navigation and control (GNC). Aircraft attitude control An aircraft's attitude is stabilized in three directions: '' yaw'', nose left or right about an axis running up and down; ''pitch'', nose up or down about an axis running from wing to wing; and ''roll'', rotation about an axis running from nose to tail. Elevators (moving flaps on the horizontal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cubesat
A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats are put into orbit by deployers on the International Space Station, or launched as secondary payloads on a launch vehicle. , more than 1,600 CubeSats have been launched. In 1999, California Polytechnic State University (Cal Poly) professor Jordi Puig-Suari and Bob Twiggs, a professor at Stanford University Space Systems Development Laboratory, developed the CubeSat specifications to promote and develop the skills necessary for the design, manufacture, and testing of small satellites intended for low Earth orbit (LEO) that perform a number of scientific research functions and explore new space technologies. Academia accounted for the majority of CubeSat launches until 2013, when more than half of launches were for non-academic purpose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conductive Heat Transfer
Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its '' thermal conductivity'', and is denoted . Heat spontaneously flows along a temperature gradient (i.e. from a hotter body to a colder body). For example, heat is conducted from the hotplate of an electric stove to the bottom of a saucepan in contact with it. In the absence of an opposing external driving energy source, within a body or between bodies, temperature differences decay over time, and thermal equilibrium is approached, temperature becoming more uniform. In conduction, the heat flow is within and through the body itself. In contrast, in heat transfer by thermal radiation, the transfer is often between bodies, which may be separated spatially. Heat can also be transferred by a combination of conduction and radiation. In solids, conduction is mediated by the combination of vibrations and collisions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust
Thrust is a reaction force In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ... described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that system. The force applied on a surface in a direction perpendicular or normal vector, normal to the surface is also called thrust. Force, and thus thrust, is measured using the International System of Units (SI) in newton (unit), newtons (symbol: N), and represents the amount needed to accelerate 1 kilogram of mass at the rate of 1 Metre per second squared, meter per second per second. In mechanical engineering, force orthogonal to the main load (such as in parallel helical gears) is referre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Aeronautics And Space Administration
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding the National Advisory Committee for Aeronautics (NACA), to give the U.S. space development effort a distinctly civilian orientation, emphasizing peaceful applications in space science. NASA has since led most American space exploration, including Project Mercury, Project Gemini, the 1968-1972 Apollo Moon landing missions, the Skylab space station, and the Space Shuttle. NASA supports the International Space Station and oversees the development of the Orion spacecraft and the Space Launch System for the crewed lunar Artemis program, Commercial Crew spacecraft, and the planned Lunar Gateway space station. The agency is also responsible for the Launch Services Program, which provides oversight of launch operations and countdown manageme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Velocity
Thermal velocity or thermal speed is a typical velocity of the thermal motion of particles that make up a gas, liquid, etc. Thus, indirectly, thermal velocity is a measure of temperature. Technically speaking, it is a measure of the width of the peak in the Maxwell–Boltzmann particle velocity distribution. Note that in the strictest sense ''thermal velocity'' is not a velocity, since ''velocity'' usually describes a vector rather than simply a scalar speed. Since the thermal velocity is only a "typical" velocity, a number of different definitions can be and are used. Taking k_\text to be the Boltzmann constant, T the absolute temperature, and m the mass of a particle, we can write the different thermal velocities: In one dimension If v_\text is defined as the root mean square of the velocity in any one dimension (i.e. any single direction), then : v_\text = \sqrt. If v_\text is defined as the mean of the magnitude of the velocity in any one dimension (i.e. any single dire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
