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Topic: Momentum wheel

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	Momentum wheel - Wikipedia, the free encyclopedia
		A momentum wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices.
		Typically a spacecraft will have several momentum wheels oriented along orthogonal axes, and when it wishes to change its rotation along those axes it will increase or decrease the spin of the momentum wheels in the opposite direction.
		Momentum wheels are usually implemented as special electric motors.
	en.wikipedia.org /wiki/Momentum_wheel (319 words)

	Encyclopedia: Angular momentum
		In physics the angular momentum of an object with respect to a reference point is a measure for the extent to which, and the direction in which, the object rotates about the reference point.
		In particular, if the body rotates about an axis, then the angular momentum with respect to a point on the axis is related to the mass of the object, the angular velocity and the distance of the mass to the axis.
		Under this formalism, angular momentum is the 2-form Noether charge associated with rotational invariance (As a result, angular momentum isn't conserved for general curved spacetimes, unless it happens to be asymptotically rotationally invariant).
	www.nationmaster.com /encyclopedia/Angular-momentum (1961 words)

	Tilting momentum wheel for spacecraft - Patent 5112012
		A momentum wheel (14, 142) for compensating for the adverse effects of disturbing torques on stabilized spacecraft is mounted on a base (12, 124) on the spacecraft by three circumferentially spaced supports which include at least two linear actuators (26, 118) that tilt the wheel (14, 142) in any desired direction.
		The momentum wheel is mounted on the spacecraft for rotation about an axis that is selectively oriented relative to the axes of the spacecraft, commonly orthogonal to the plane of the spacecraft's orbit.
		Momentum wheel means, including a momentum wheel rotatable about an axis of rotation, applies a torque to the spacecraft in order to compensate for the adverse affects of disturbing torques.
	www.freepatentsonline.com /5112012.html (4650 words)

	Superconductor Benefits Sat Makers
		The spinning wheels hold considerable angular momentum (inertia) and resist being reoriented.
		Fleeter critiqued the superconducting momentum wheel for UH.
		This free-spinning phenomenon is the basis of the superconducting momentum wheel.
	www.spacedaily.com /news/future-99f.html (683 words)

	Magnetically suspended angular momentum wheel - Patent 4065189
		The rotor of the momentum wheel, in the form of a circular disk whose diameter greatly exceeds its thickness, is maintained in suspension, free of physical contact with the housing, by means of magnetic fields applied between the circular flat surfaces of the rotor disk and a pair of stator plates.
		Momentum wheels are designed to exchange angular momentum with a vehicle and are particularly useful in spacecraft for attitude control.
		In the preferred embodiment, the angular momentum wheel, is in the shape of a cylinder 161/2 inches in diameter and 11/2 inches in length.
	www.freepatentsonline.com /4065189.html (4019 words)

	AMSAT - P3D Magnetic-Bearing Momentum Wheel
		Momentum wheels are frequently used for 3-axis attitude control on satellites, allowing the spacecraft to point its antennas at the Earth and the solar generator at the sun.
		The momentum of the wheels has to be dumped at a speed of 3000 rpm, which is achieved by generating an external torque at the perigee of the satellite orbit at a height of 4000 km.
		The wheel is off-centre by 0.7 mm and the magnetic flux density has risen to 1.38 T while the airgap has narrowed to 0.3 mm (at 180 degrees).
	www.amsat.org /amsat-new/archive/satellites/phase3d/wheels/index.php (3191 words)

	Momentum wheel (Site not responding. Last check: 2007-10-20)
		A momentum wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or otherreaction devices.
		Momentum wheels are usually implemented as special electric motors.Both spin-up and braking are controlled electronically by computer controls.
		Since the momentum wheel is a small fraction of the spacecraft's total mass, easily-measurable changes in its speed providevery precise changes in angle.
	www.therfcc.org /momentum-wheel-42180.html (297 words)

	Satellite Angular Momentum Control System Using Magnet-Superconductor Flywheels (Site not responding. Last check: 2007-10-20)
		--A torque/reactive momentum wheel control system for use in satellites for dynamic attitude maintenance and alteration where the flywheel of each momentum wheel is levitated by a high-temperature superconducting element repulsively interacting with permanent magnets in the flywheel.
		Each momentum wheel is cooled by a cryo-cooler and can have a total weight of about l0 Kg to a fraction of 1 Kg and delivering 3.5 Js with less than 1 W loss.
		To change the orientation and spin of the satellite the momentum of one or all of the momentum storage devices is changed which, in turn, changes the angular momentum of the satellite resulting in its orientation change.
	www.isso.uh.edu /publications/A2001/403-chu.htm (618 words)

	Ceramics Today - The Origins of the Potter's Wheel
		Until the continuous power-driven wheel arrived, the throwing technique was possible only with a low friction, fast, heavy momentum wheel.
		Like the 16th century Italian wheel, the model on the left is mostly made of wood with a strip of greased leather used as an upper bearing and a metal point and a stone or glass socket at the base.
		In China and Japan it is was usual for the potter to sit at or near ground level, not on a raised seat as in the West.
	www.ceramicstoday.com /articles/potters_wheel2.htm (1703 words)

	HT-RSI
		TELDIX momentum and reaction wheels are available in five different sizes with an angular momentum storage capacity spanning a range between 0.04 Nms and 68 Nms.
		The wheels accommodate the requirements of attitude control systems for satellites weighing less than 65 kg as well as for geostationary satellites reaching a mass of three tons and more.
		This wheel family covering the momentum range from 14 to 68 Nms features a versatile design capable of dealing with a great variety of applications in all possible satellite orbits.
	www.teldix.de /P22/ht-rsi.htm (240 words)

	Exploratorium: Science Snacks: Bicycle Wheel Gyro
		A rotating bicycle wheel has angular momentum, which is a property involving the speed of rotation, the mass of the wheel, and how the mass is distributed.
		For example, most of a bicycle wheel's mass is concentrated along the wheel's rim, rather than at the center, and this causes a larger angular momentum at a given speed.
		Unfortunately, the gyroscopic precession of the wheel hanging from the rope is not explainable in as straightforward a manner as the rotating stool effect.
	www.exploratorium.edu /snacks/bicycle_wheel_gyro.html (656 words)

	Momentum
		Code momentum Code momentum is a situation that the more places a code dependency is repeated in the code, the more stub...
		Momentum Momentum is the Minkowski, momentum isn't defined at all.
		Momentum wheel A momentum wheel is a type of rockets or other reaction devices.
	www.brainyencyclopedia.com /topics/momentum.html (119 words)

	Surrey Gives Comet Lander Attitude
		SSTL's wheel will have to survive a cruise time of 9 years through space and then be used for the last critical 20 hours during the final approach and landing on the comet.
		The wheel is similar in size to that onboard SSTL's UoSAT-12 minisatellite, launched in April 1999 and operational in low Earth orbit.
		By changing the momentum wheel's speed over a limited range (less than 10% of the nominal speed) the satellite can easily be rotated around the spin direction, thus rotational momentum can be exchanged between the wheel disc and the satellite's body.
	www.spacedaily.com /news/rosetta-00a.html (366 words)

	Momentum wheel -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-20)
		Typically a spacecraft will have several momentum wheels oriented along (Click link for more info and facts about orthogonal) orthogonal axes, and when it wishes to change its rotation along those axes it will increase or decrease the spin of the momentum wheels in the opposite direction.
		Momentum wheels are usually implemented as special (A motor that converts electricity to mechanical work) electric motors.
		The most efficient practice is probably to use high-efficiency attitude jets such as (Click link for more info and facts about ion thruster) ion thrusters, or small, lightweight (Click link for more info and facts about solar sail) solar sails on the ends of projecting masts or solar cell arrays.
	www.absoluteastronomy.com /encyclopedia/m/mo/momentum_wheel.htm (361 words)

	Venus' mysteries, another view. - Bad Astronomy and Universe Today Forum
		Note that the growing misalignment of the spin axis causes the vector sum of the angular momentums of the mantle and the core to decrease, whilst angular momentum is transferred via external gravity forces to the infering celetial body during the precession.
		The turning momentum of the inner core is of a tremendous value and the inner core grows, it’s increasing its angular momentum rapidly, to the fifth power of the radius, if I'm right.
		And presumably, this angular momentum would be somewhere between that of the mantle and that of the inner core.
	www.bautforum.com /showthread.php?t=10879&page=2&pp=20 (4853 words)

	GOES-J STATUS (Site not responding. Last check: 2007-10-20)
		GOES-J's momentum wheels became noisy in 1998, and the satellite was shut down and left orbiting in cold storage until 2002.
		In June and July of 1998, the two main momentum wheels on GOES-J began demanding high power levels to maintain their normally modest rotation rate (2900 rpm), as though the bearings were beginning to fail on both wheels.
		The buzz from the momentum wheel may be causing the coherent noise in the visible channel.
	rsd.gsfc.nasa.gov /goes/text/goesjstatus.html (1975 words)

	sci.engr.* FAQ on Failures: Mars Climate Orbiter
		The MCO featured as part of its attitude control system a momentum wheel, which spins like a top and is mounted along the spacecraft pitch axis.
		When a torque is applied to the momentum wheel, its spin rate accelerates -- and momentum is exchanged with the spacecraft, which accelerates about the pitch axis in the opposite direction.
		Pitch rate and attitude errors are fed back to govern momentum wheel torques, and the resulting momentum exchange compensates for these errors.
	www.tcnj.edu /~rgraham/failures/MCOcraft.html (479 words)

	CRAFTS : Web Exclusive: Potter's Wheels : DIY Network
		The kick wheel, or momentum wheel, is one of the oldest and simplest types of wheel used to make hand-thrown pottery.
		Wheels rated 1/4 hp will be at the lower end price range: $350 to $650.
		Wheels using a 1/3 or 1/2 hp rated motor will be priced in the $500 to $1200 range.
	www.diynet.com /diy/crafts/article/0,2025,DIY_13786_2949992,00.html (286 words)

	Lockerbie Model K Kick Wheel (Site not responding. Last check: 2007-10-20)
		Lockerbie's Model K Kick Wheel is one of the finest free momentum wheels available.
		Underneath the flywheel is a free wheeling Timkin tapered roller bearing unit, mounted in a special, self-aligning housing.
		The wheel as a whole weighs about 95 lbs, and includes 24 lbs of steel in the rim for added centrifugal effect.
	www.dickblick.com /zz300/14 (260 words)

	Reaction/Momentum Wheel
		Being a big wheel in spacecraft lingo may be detrimental if you are trying to stay competitive in the explosive world of small satellite building.
		The wheel is unique in its small size, extremely low residual imbalance, and large, highly controllable torque.
		This wheel is unique in that it features a large, highly controllable torque in a small package with low power and an extremely low residual imbalance.
	www.sti.nasa.gov /tto/spinoff1997/t3.html (568 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		They are technically not "gyroscopes", but they operate using "gyroscopic principles", in that if you apply rotation forces to a spinning wheel, you get a transfer of angular momentum from the wheel to the structure it is anchored to.
		A reaction wheel is normally at rest but can be spun up from this rest state to induce rotation in the vehicle.
		A momentum wheel, on the other hand, is constantly spinning at high speed and we either slow it down or speed it up to affect attitude control maneuvers.
	www.orbitersim.com /v2/read.asp?id=22326 (1169 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		Momentum Wheel with Magnetic Bearing ------------------------------------ Attitude Control of the AMSAT AO-40 Spacecraft Most satellites today use momentum wheels for attitude control.
		Conventional momentum wheels with ball bearings frequently caused problems since in the vacuum of space the lubrication of the bearings is very difficult.
		Furthermore it is hoped that the experience gained with magnetic levitation systems will find applications in other areas, for instance for magnetic levitation trains and in large size electromechanical projection display systems.
	www.amsat-dl.org /journal/wheels.txt (206 words)

	Gyro Chair
		As soon as you spin the bicycle wheel, it gains angular momentum (the combination of the wheel's mass and the spinning speed).
		The more angular momentum the wheel has, the harder it is to change direction.
		You, the stool and the wheel all combine to forma system which obey the law of conservation of angular momentum.
	www.exploratorium.edu /cmp/exhibits/g/gyro_chair.html (138 words)

	Cyrospace, Inc. - Featured Technologies
		Researchers at the University of Houston have devised a new momentum wheel for micro satellites.
		The invention is a momentum wheel that uses the interaction between a high temperature superconductor and a permanent magnet, to produce a totally passive levitated wheel.
		This process is better than currently used methods: (1) the wheel may be as light as 1 - 2 kg; (2) it can rotate between 3-10 thousand RPM; and (3) only a fraction of a watt is needed to keep the wheel rotating at top speed.
	www.cyrospace.com /featured/micro.htm (198 words)

	clayart - thread 'kick wheel - sore legs' (Site not responding. Last check: 2007-10-20)
		wheel slows naturally and you adapt to the rythm of the wheel.
		wheel is used far too often just for speed, as it has very little torque.
		> wheel slows naturally and you adapt to the rythm of the wheel.
	www.potters.org /subject27252.htm (682 words)

	Seth Major commentary: no hands
		An isolated, spinning wheel continues to rotate, just as it is. The wheel's axle always points in the same direction.
		Hiding in this use of the word momentum is a length and a direction.
		A gyroscope may be an obtuse character, but at its heart it is a simple, spinning wheel with a (mostly) unchanging angular momentum.
	academics.hamilton.edu /physics/smajor/Papers/no_hands.html (488 words)

	Momentum wheel : Reaction wheel (Site not responding. Last check: 2007-10-20)
		terms defined : Momentum wheel : Reaction wheel
		All is still licensed under the GNU FDL.
		Half-past one, The street lamp muttered, "Regard that woman Which opens on her like a grin.
	www.termsdefined.net /re/reaction-wheel.html (570 words)

	Spacecraft having a momentum wheel configuration that prevents zero wheel speeds page
		A momentum wheeI arrangement thаt might be used оn a spacecraft whiсh hаs a momentum bias thаt prevents zerо wheeI speeds.
		The momentum wheeIs аre оriented suсh thаt the proper momentum vectors аre nоt copIanar.
		None of the momentum wheeIs hаve the wheeI axis paraIIeI to the momentum bias direction of the spacecraft.
	www.patentalert.com /docs/001/z00101645.shtml (279 words)

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