Lecture

Attitude Control Systems: Gyro vs CMG

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Description

This lecture discusses methods for gyro-based attitude control systems, starting with reaction wheels used on Hubble and then moving on to Control Moment Gyros (CMGs) used on the International Space Station. It explains how the conservation of angular momentum affects the vehicle's reaction to changes in the spinning wheel's angular velocity, and how CMGs work by changing the orientation of the gyroscope to control the spacecraft's orientation. The lecture also covers the cluster of four CMGs used on the US segment of the International Space Station to maintain its attitude and orientation.

In MOOC

Space Mission Design and Operations

Space exploration is a very exciting subject. Consider the achievements of Sputnik 1, Yuri Gagarin's first flight in space, the Apollo missions to the Moon, followed by the Shuttle program, the Hubble Space Telescope launch and maintenance on orbit, and finally the assembly and exploitation of the International Space Station. These were challenging undertakings involving space agencies and industrial teams of several nations, and private companies as well. Space telescopes are in service, and several compon

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Related concepts (31)

Angular momentum

In physics, angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity – the total angular momentum of a closed system remains constant. Angular momentum has both a direction and a magnitude, and both are conserved. Bicycles and motorcycles, flying discs, rifled bullets, and gyroscopes owe their useful properties to conservation of angular momentum.

Spacecraft attitude control

Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle or satellite) 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.

Gyroscope

A gyroscope (from Ancient Greek γῦρος gŷros, "round" and σκοπέω skopéō, "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotation (spin axis) is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum.

Relativistic angular momentum

In physics, relativistic angular momentum refers to the mathematical formalisms and physical concepts that define angular momentum in special relativity (SR) and general relativity (GR). The relativistic quantity is subtly different from the three-dimensional quantity in classical mechanics. Angular momentum is an important dynamical quantity derived from position and momentum. It is a measure of an object's rotational motion and resistance to changes in its rotation.

Angular momentum operator

In quantum mechanics, the angular momentum operator is one of several related operators analogous to classical angular momentum. The angular momentum operator plays a central role in the theory of atomic and molecular physics and other quantum problems involving rotational symmetry. Such an operator is applied to a mathematical representation of the physical state of a system and yields an angular momentum value if the state has a definite value for it.

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