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148 pages
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Size: 1129k
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A Preliminary Study of the Structural Dynamic Behavior of the NASA Manned Spacecraft Center (MSC) Centrifuge
Institution: | Madison University - Madison, USA |
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Advisor(s): | Dr. M.R.Mousighi |
Degree: | PhD |
Year: | 2003 |
Volume: | 148 pages |
ISBN-10: | 1581122063 |
ISBN-13: | 9781581122060 |
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This dissertation involves a preliminary study into the structural dynamic
behavior of the NASA Manned Spacecraft Center (MSC), located in
the Flight Acceleration Facility, bldg 29, in Houston,
Texas. The 50-ft. arm can swing the three-man gondola to
create g-forces astronauts will experience during
controlled flight and during reentry. The centrifuge
was designed primarily for training Apollo astronauts. During
operation of the centrifuge, the astronauts can control
the motion of the gondola in two gimbal axes, while the gondola
is rotating about its principal axis, to simulate flight activity.
The result of these coupled motions lead to transient loading
functions, which arise due to rigid body kinematics.
The study is describe in three Chapters. Chapter 1 deals with the response
of a simplified model of the arm, gimbal and gondola structure
for the purpose of obtaining dynamic response factors to be associated
with the arm. Chapter 2 deals briefly with a simplified model
of the same system for the purpose of obtaining dynamic
response factors to be associated with the gimbal ring and to
justify the simplifications implicit in the model used in Chapter
1. In Chapter 3, the rigid body kinematic equations
are studied in order to develop relations
between the forcing functions utilized in Chapters
1 and 2 and the motion parameters of the kinematic
analysis. Using these relations, the dynamic response factors
tabulated in Chapters 1 and 2 in terms of the generalized forcing
functions may be interpreted in terms of the motion parameters.
The following assumptions have been made in order to obtain a solution within
a reasonable time period for the preliminary study:
1. The gondola will be considered to be a rigid body;
2. The gimbal ring will also be considered to be a rigid body in the analysis
of Chapter 1, and will be considered to be a simple spring-mass
system in the analysis of Chapter 2;
3. The arm will be studied as another simple spring-mass system, acting
as a uniform cantilever with a mass at its tip;
4. Small deflection, linear theory will be employed throughout the analysis;
5. Structural damping will be ignored for conservatism;
6. Lateral (tangential), vertical and torsional modes will be considered
to be uncoupled and studied separately.
In defense of the apparent over-simplification of the complex system, which
would be avoided if time permitted, it is to be observed
that the simplifications are not as restrictive as they appear. The
reason is that: 1) both the gondola and the gimbal ring
are relatively rigid compared to the arm. Since the forcing functions
have time durations that are not common in periodicity with
the more rigid system but more common with the arm, simplification is
permissible (as shown in Chapter 2 and Appendix 6);
2) The lumped parameter method is a conventional method
of analysis; 3) Structural damping is small and the
effect on transient motion is thus negligible; 4)
An analysis (Appendix 3) has shown that coupling
between modes does not occur; and 5) Neglecting
the extensional mode is a conventional assumption and dynamic
augmentation of centrifugal force is negligible.
The preliminary study of the structural dynamic response of the MSC centrifuge
to transient loads resulting from gimbal-controlled motions has
been completed. The results of the study are summarized
in tables of dynamic response factors for lateral, torsional
and vertical modes for three types of generalized impulsive
loading functions: 1) a square pulse, 2) a saw-tooth ramp,
and 3) a half sine pulse. In Chapter 3 of the study,
the rigid body kinematic equations have been analyzed
so that these generalized loading functions used in the analysis may
be interpreted in terms of the motion parameters.
Frederick Palmieri was educated at UCLA where he studied engineering, then at Stanford University, where he earned a B.S. degree in Mathematics, a M.S. degree in Engineering Mechanics and completed studies towards a doctoral degree under the tutorage of his principal advisor, Donovan Young. He also studied under S. Timoshenko, J. Goodier, and W. Flugge. He has been active in the engineering field for over 40 years, specializing in the field of applied mechanics with particular emphasis on structural dynamics.
148 pages
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Size: 1129k
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