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Control Moment Gyroscope
A control moment gyroscope (CMG) is an attitude control device generally used in spacecraft attitude control systems. A CMG consists of a spinning rotor and one or more motorized gimbals that tilt the rotor’s angular momentum. As the rotor tilts, the changing angular momentum causes a gyroscopic torque that rotates the spacecraft. Mechanics CMGs differ from reaction wheels. The latter apply torque simply by changing rotor spin speed, but the former tilt the rotor's spin axis without necessarily changing its spin speed. CMGs are also far more power efficient. For a few hundred watts and about 100 kg of mass, large CMGs have produced thousands of newton meters of torque. A reaction wheel of similar capability would require megawatts of power. Design varieties Single-gimbal The most effective CMGs include only a single gimbal. When the gimbal of such a CMG rotates, the change in direction of the rotor's angular momentum represents a torque that reacts onto the body to which t ... [...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 (rotation), 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. Elevator (aeronautics), Elevat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skylab
Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations included an orbital workshop, a solar observatory, Earth observation, and hundreds of experiments. Unable to be re-boosted by the Space Shuttle, which was not ready until 1981, Skylab's orbit eventually decayed, and it disintegrated in the atmosphere on July 11, 1979, scattering debris across the Indian Ocean and Western Australia. Overview Skylab was the only space station operated exclusively by the United States. A permanent station was planned starting in 1988, but funding for this was canceled and replaced with United States participation in an International Space Station in 1993. Skylab had a mass of with a Apollo command and service module (CSM) attached and included a workshop, a solar observatory, and several hundred life sc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zero-propellant Maneuver
A zero-propellant maneuver (ZPM) is an optimal attitude trajectory used to perform spacecraft rotational control without the need to use thrusters. ZPMs are designed for spacecraft that use momentum storage actuators. Spacecraft ZPMs are used to perform large angle rotations or rate damping (detumbling) without saturating momentum actuators, and momentum dumping (from storage) without thrusters. Background Spacecraft rotational operations, such as turning to point in a new direction, are usually performed by angular momentum storage devices such as reaction wheels or control moment gyroscopes. It is generally preferable to use these devices instead of traditional thrusters, as they are powered by renewable electricity instead of by propellant; firing thrusters uses up the fixed amount of propellant on the spacecraft. Propellant is very costly because it must be carried from earth; once it is used up, the spacecraft's life is over. Therefore, the operational life of the spacecraft i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Pressure
Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is absorbed, reflected, or otherwise emitted (e.g. black-body radiation) by matter on any scale (from macroscopic objects to dust particles to gas molecules). The associated force is called the radiation pressure force, or sometimes just the force of light. The forces generated by radiation pressure are generally too small to be noticed under everyday circumstances; however, they are important in some physical processes and technologies. This particularly includes objects in outer space, where it is usually the main force acting on objects besides gravity, and where the net effect of a tiny force may have a large cumulative effect over long periods of time. For example, had the effects of the Sun's radiation pressure on the spacecraft of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Drag
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or between a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, the drag force depends on velocity. Drag force is proportional to the velocity for low-speed flow and the squared velocity for high speed flow, where the distinction between low and high speed is measured by the Reynolds number. Even though the ultimate cause of drag is viscous friction, turbulent drag is independent of viscosity. Drag forces always tend to decrease fluid velocity relative to the solid object in the fluid's path. Examples Examples of drag include the component of the net aerodynamic or hydrodynamic force acting opposite to the dire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Gradient
Gravity gradiometry is the study and measurement of variations ( anomalies) in the Earth's gravity field. The gravity gradient tensor is the spatial rate of change of gravitational acceleration; as acceleration is a vector quantity, with magnitude and three-dimensional direction, the full gravity gradient is a 3x3 tensor. Gravity gradiometry is used by oil and mineral prospectors to measure the density of the subsurface, effectively by measuring the rate of change of gravitational acceleration due to underlying rock properties. From this information it is possible to build a picture of subsurface anomalies which can then be used to more accurately target oil, gas and mineral deposits. It is also used to image water column density, when locating submerged objects, or determining water depth (bathymetry). Physical scientists use gravimeters to determine the exact size and shape of the earth and they contribute to the gravity compensations applied to inertial navigation systems. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ISS Gyroscope
The International Space Station (ISS) is the largest Modular design, modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), European Space Agency, ESA (Europe), and Canadian Space Agency, CSA (Canada). The ownership and use of the space station is established by intergovernmental treaties and agreements. The station serves as a microgravity and space environment research laboratory in which Scientific research on the International Space Station, scientific research is conducted in astrobiology, astronomy, meteorology, physics, and other fields. The ISS is suited for testing the spacecraft systems and equipment required for possible future long-duration missions to the Moon and Mars. The International Space Station programme, ISS programme evolved from the Space Station Freedom, Space Station ''Freedom'', a 1984 American proposal to constr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kristall
The Kristall (russian: Кристалл, , Crystal) (77KST, TsM-T, 11F77T) module was the fourth module and the third major addition to ''Mir''. As with previous modules, its configuration was based on the 77K (TKS) module, and was originally named "Kvant 3". It was launched on May 31, 1990 on Proton-K. It docked to Mir autonomously on June 10, 1990. Description Kristall had several materials processing furnaces. They were called Krater 5, Optizon 1, Zona 2, and Zona 3. It also had a biotechnology experiment called the Aniur electrophoresis unit. These experiments were capable of generating 100 kg of raw materials for use on Earth. Located in the docking node was the Priroda 5 camera which was used for Earth resources experiments. Kristall also had several astronomy and astrophysics experiments which were designed to augment experiments that were already located in Kvant-1. Kristall's solar panels were also different from others on Mir. They were designed to be "collapsible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kvant-2
Kvant-2 (russian: Квант-2; English: Quantum-II/2) (77KSD, TsM-D, 11F77D) was the third module and second major addition to the Mir space station. Its primary purpose was to deliver new science experiments, better life support systems, and an airlock to Mir. It was launched on November 26, 1989 on a Proton rocket. It docked to Mir on December 6. Its control system was designed by the NPO "Electropribor" (Kharkiv, Ukraine). Description Kvant-2 was the first Mir module based on the TKS spacecraft (77k module). Kvant-2 was divided into three compartments. They were the EVA airlock, the instrument/cargo compartment, and the instrument/experiment compartment. The instrument/cargo compartment could be sealed off and act as an extension or a back-up to the airlock. Before Kvant-2 docked to the station, EVAs had to be carried by depressurizing the docking node on the Core Module. Kvant-2 also carried the Soviet version of the Manned Maneuvering Unit for the Orlan space suit. It de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kvant-1
Kvant-1 (russian: Квант-1; English: Quantum-I/1) (37KE) was the first module to be attached in 1987 to the Mir Core Module, which formed the core of the Soviet space station ''Mir''. It remained attached to ''Mir'' until the entire space station was deorbited in 2001. The Kvant-1 module contained scientific instruments for astrophysical observations and materials science experiments. It was used to conduct research into the physics of active galaxies, quasars and neutron stars and it was uniquely positioned for studies of the Supernova SN 1987A. Furthermore, it supported biotechnology experiments in anti-viral preparations and fractions. Some additions to Kvant-1 during its lifetime were solar arrays and the ''Sofora'' and ''Rapana'' girders. The Kvant-1 module was based on the TKS spacecraft and was the first, experimental version of a planned series of '37K' type modules. The 37K modules featured a jettisonable TKS-E type propulsion module, also called the Functional Servi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salyut 6
Salyut 6 (russian: Салют-6; lit. Salute 6), DOS-5, was a Soviet orbital space station, the eighth station of the Salyut programme. It was launched on 29 September 1977 by a Proton rocket. Salyut 6 was the first space station to receive large numbers of crewed and uncrewed spacecraft for human habitation, crew transfer, international participation and resupply, establishing precedents for station life and operations which were enhanced on Mir and the International Space Station. Salyut 6 was the first "second generation" space station, representing a major breakthrough in capabilities and operational success. In addition to a new propulsion system and its primary scientific instrument—the BST-1M multispectral telescope—the station had two docking ports, allowing two craft to visit simultaneously. This feature made it possible for humans to remain aboard for several months. Six long-term resident crews were supported by ten short-term visiting crews who typically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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