Journal of Aerospace Engineering

In this paper, a novel methodology is developed to absorb the vibrations of relatively large-scale aircraft structures such as landing gear components. This is accomplished using a combination of active and passive controls. A system equivalent to a Boeing 747 landing gear break rod is selected as a test bed. The expected goal of this study is to dissipate the fundamental vibration mode of the tube. A beam-type dynamic absorber and a constrained layer damping treatment are used for passive vibration control. Simulations and experimental results are provided for the dynamic absorber case. In addition, full-state feedback along with state estimation based on the “reciprocal state space” method is presented. The plant responses and estimates for both the open loop and closed loop systems are shown in simulations. An optimal controller based on acceleration measurements using piezoelectric actuators is implemented using a hardware in the loop protocol for the active vibration control of the system. The integrated controller with passive and active components absorbs the fundamental mode of the system, according to the experimental results.

This paper reviews the prospects for the development of commercial hotels in space; it shows that it is increasingly accepted that this could become a lively new field of business within little more than a decade. The key enabler is the availability of low-cost access to space through the operation of reusable passenger-carrying launch vehicles, the development of which requires investment equal to no more than a few months worth of existing space budgets. When this becomes available, competition will lead to rapid development of progressively more exotic facilities in orbit as companies exploit the unique environment of space to provide guests with ever more popular services. Discussed are some of the civil engineering topics that will arise as orbital accommodation grows from assemblies of prefabricated modules to large structures assembled in orbit, including rotating structures offering “artificial gravity,” and eventually to buildings on the lunar surface.

Nonlinear finite-element models are developed that predict the load-elongation behavior of conical-head bolted lap joints, and the load-elongation predictions are compared with experimental test data. The study is conducted for several panel thicknesses with three fastener sizes and three panel materials. The model load-elongation predictions are in excellent agreement with experimental test data. Model parameters, such as part discretization, material model selection, sliding interface friction coefficients, and convergence tolerances, are discussed. A means of inducing clamp in the joint is also developed. The results show that nonlinear finite-element analysis may reliably predict the behavior of conical-head bolted joints.