# Shared Flashcard Set

## Details

Spacecraft Dynamics and Control
Study guide for spacecraft test
46
Engineering
04/23/2014

Term
Definition
 Key advantages: you do not need all eigenvalues/eigenvectors, only need the maximum eigenvalue and its eigenvector, easy and fast methods for finding that eigen pair.
Term
 What are the axes of rotation? What does energy dissipation do to the axes?
Definition
 Major axis (x) stable, intermediate axis (y) unstable, minor axis (z) stable. Makes the minor axis unstable.
Term
 How did Explorer I fail?
Definition
 The reason for the failure of this satellite was it spun about its minor axis.
Term
 What is G2 stabilization?
Definition
 This method is a way of stabilizing a satellite’s orbit by using only the satellite’s mass distribution and the Earth’s gravitational field.
Term
 Is G2 stabilization accurate? Why or why not.
Definition
 This stabilization method is not accurate because spacecraft can flip over, and needs extra payload mass due to the “boom” mass.
Term
 Is the moon G2 stabilized?
Definition
 Yes
Term
 What is dual-spin stabilization?
Definition
 stabilization method of having the spacecraft contain two parts: one that spins relatively fast, and the other spins slow or not at all. It allows satellites to spin stably about its minor axis.
Term
 The name of the first satellite to be dual-spin stabilized.
Definition
 TACSAT I
Term
 What happened to Polar BEAR?
Definition
 It inverted its stabilization because of solar heating on the boom mass.
Term
 What was the first spin-stabilized satellite?
Definition
 Syncom 3
Term
 What is 3 axis stabilization?
Definition
 Three-axis stabilization is a method of keeping all 3 axes pointed in specific directions.
Term
 What is magnetic stabilization?
Definition
 Magnetic Stabilization is a method of creating a torque due to the movement through the Earth’s magnetic field to increase or decrease the spin of a satellite.
Term
 In particle model analysis, what motion(s) is/are of interest?
Definition
 only translational
Term
 In rigid body analysis, what motion(s) is/are of interest?
Definition
 translational and rotational
Term
 Inertia matrices are always...
Definition
 real and symmetric
Term
 All eigenvalues of real symmetric matrices are ____ and all eigenvectors of real symmetric matrices are _____.
Definition
 real;real and mutually orthogonal
Term
 What is the significance of inertia matrices being diagonal?
Definition
 the axes in which it is expressed are principal axes.
Term
 (T/F) If a rigid body has 3 axes of symmetry, then those are the principal axes.
Definition
 True
Term
 (T/F) A rigid body's principal axes are always its axes of symmetry.
Definition
 False
Term
 Normalizing eigenvectors makes them...
Definition
 orthonormal
Term
 What is the Change of Basis Theorem?
Definition
 It can be used to verify that for principal axes the inertia matrix is diagonal.
Term
 (T/F) Angular momentum and energy are constant for asymmetric torque free rigid body.
Definition
 True
Term
 (T/F) Longest axis corresponds to SMALLEST PMOI (principal moment of inertia).
Definition
 False
Term
 What do the directions of the orbital frame correspond to?
Definition
 o3 axis is nadir direction, o2 axis is negative orbit normal direction, o1 axis completes frame.
Term
 The motion of the satellite’s center of mass motion around Earth’s center applies to...
Definition
 Translational equation (Newton's Equation).
Term
 satellite’s rotation around satellite’s center of mass applies to...
Definition
 Rotational equation (Euler's equation).
Term
 What is required for G2 stabilization?
Definition
 A body fixed ref. frame, and a long boom.
Term
 Why are the equilibrium solutions for Euler's equations hard to solve?
Definition
 angular velocity is of the body frame with respect to the inertia frame, o3 is a column vector made by projecting o3hat onto body axes, and these equations are nonlinear.
Term
 (T/F) You need small angle assumptions to find equilibrium solutions.
Definition
 False.
Term
 (T/F) You do not need small angle assumptions to find equilibrium solutions.
Definition
 True
Term
 You do not need all eigenvalues/eigenvectors, only need the maximum eigenvalue and its eigenvector, easy and fast methods for finding that eigen pair are key advantages of what?
Definition
 minimizing J
Term
 Minor axis becoming unstable is due to...
Definition
 energy dissipation
Term
 This satellite failed due to spinning about its minor axis.
Definition
 Explorer I
Term
 This stabilization method is a way of stabilizing a satellite’s orbit by using only the satellite’s mass distribution and the Earth’s gravitational field.
Definition
 G2 stabilization
Term
 This stabilization method is not accurate because spacecraft can flip over, and needs extra payload mass due to the “boom” mass.
Definition
 G2 stabilization
Term
 This stabilization method has the spacecraft contain two parts: one that spins relatively fast, and the other spins slow or not at all. It allows satellites to spin stably about its minor axis.
Definition
 dual-spin stabilization
Term
 What is the significance of TACSAT I?
Definition
 The first satellite to be dual-spin stabilized.
Term
 What is the name of the satellite that inverted its stabilization because of solar heating on the boom mass?
Definition
 Polar BEAR
Term
 What is the significance of Syncom 3?
Definition
 It was the first spin-stabilized satellite.
Term
 What is the name of the stabilization method of keeping all 3 axes pointed in specific directions?
Definition
 3 axis stabilization
Term
 What is the name of the stabilization method of creating a torque due to the movement through the Earth’s magnetic field to increase or decrease the spin of a satellite.
Definition
 Magnetic stabilization
Term
 (T/F) If a rigid body has 3 axes of symmetry, then those are NOT the principal axes.
Definition
 False
Term
 (T/F) A rigid body's principal axes are NOT always its axes of symmetry.
Definition
 True
Term
 How do you create orthonormal eigenvectors?
Definition
 Normalize!
Term
 (T/F) Angular momentum and energy are NOT constant for asymmetric torque free rigid body.
Definition
 False
Term
 (T/F) Longest axis corresponds to LARGEST PMOI (principal moment of inertia).
Definition
 True
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