Static and dynamic characteristics of end-loaded beams with specific application in square solar sails

Solar sails have recently received renewed interest from the scientific community. One particular solar sail design, the four-quadrant square sail, has received particular focus from the National Aeronautics and Space Administration (NASA). This design consists of a central hub and four long booms rigidly attached to it. One specific concept for a four-quadrant square solar sail utilizes the remaining stiffness in post-buckled booms to tension the sail membranes as well as the pre-buckled axial stiffness. This removes the requirement of minimum axial stiffness and allows for even further weight reduction of the sail.;Because a square solar sail is a double-symmetric system, a large amount of insight can be gained by studying a single boom instead of the entire system. The post-buckled dynamic characteristics of a boom loaded by cable passing through a fixed point is studied employing both numerical shooting methods and experimental structural dynamics techniques.;The results show that post-buckled frequencies increase near bifurcation, but approach a maximum and begin to decrease as the structure becomes highly deflected and resembles a loop. In addition, varying the attachment point of the cable away from the beam has a similar result on static and dynamic behavior as introducing initial imperfections into the beam itself. The post-buckled statics and dynamics of tapered beams are also explored. Both experiments and numerical analyses are performed on beams with different taper ratios, and the effect of the tapering compared to the uniform system. The tapered systems result in very different static deflection characteristics and dynamic behavior, in addition to different mode shapes.;Finally, the effect of gravity, multiple booms and a different cable attachment is studied. The results show that gravitational loading does not dramatically change the dynamic characteristics of the unloaded system, but magnifies the mode splitting of symmetric and anti-symmetric modes in multiple beam systems.