Location
Cocoa Beach, FL
Start Date
5-4-1965 8:00 AM
Description
During the prelaunch time, launch vehicles will be exposed to prevailing ground winds. When circular cylindrical structures (such as launch vehicles) are exposed to winds, vortices are shed alternately from the sides of the structure which causes alternating lift forces to act upon the sides. Under certain conditions large oscillations can occur depending on the vehicle's structural damping and the characteristics of the wind forces. Wind tunnel investigations of launch vehicles 1,2 indicate that launch vehicles do experience relatively large oscillation amplitudes.
This paper discusses the phenomenon of vortex shedding and techniques of calculating response of cylindrical structures subjected to wind. With this background, the paper moves to consider the two basic approaches to controlling the wind-induced oscillation amplitudes. The primary approach, Excitation Control Techniques, which consists of methods that either alter the nature or diminish the magnitude of the aerodynamic exciting force. The secondary approach, Response Control Techniques, includes methods that seek to reduce the systems admittance to these forces, counteract the force of the wind or dissipate the energy of the wind as the vehicle receives it. The control systems are discussed in the light of their advantages, limitations and methods of functioning; and the efficacy and economics of each of the systems is also pointed out. In the conclusions, the systems are compared, and the reasons for choosing some systems over others are discussed.
It is appropriate for the author to thank the Launch Support Equipment Engineering Division of the Kennedy Space Center who made this paper possible and the Brown Engineering Company associates who supplied background information.
Designs to Control Wind-Induced Oscillations of Launch Vehicles
Cocoa Beach, FL
During the prelaunch time, launch vehicles will be exposed to prevailing ground winds. When circular cylindrical structures (such as launch vehicles) are exposed to winds, vortices are shed alternately from the sides of the structure which causes alternating lift forces to act upon the sides. Under certain conditions large oscillations can occur depending on the vehicle's structural damping and the characteristics of the wind forces. Wind tunnel investigations of launch vehicles 1,2 indicate that launch vehicles do experience relatively large oscillation amplitudes.
This paper discusses the phenomenon of vortex shedding and techniques of calculating response of cylindrical structures subjected to wind. With this background, the paper moves to consider the two basic approaches to controlling the wind-induced oscillation amplitudes. The primary approach, Excitation Control Techniques, which consists of methods that either alter the nature or diminish the magnitude of the aerodynamic exciting force. The secondary approach, Response Control Techniques, includes methods that seek to reduce the systems admittance to these forces, counteract the force of the wind or dissipate the energy of the wind as the vehicle receives it. The control systems are discussed in the light of their advantages, limitations and methods of functioning; and the efficacy and economics of each of the systems is also pointed out. In the conclusions, the systems are compared, and the reasons for choosing some systems over others are discussed.
It is appropriate for the author to thank the Launch Support Equipment Engineering Division of the Kennedy Space Center who made this paper possible and the Brown Engineering Company associates who supplied background information.
