Large Angle Satellite Attitude Maneuvers

Two methods are proposed for performing large angle reorientation maneuvers. The first method is based upon Euler's rotation theorem; an arbitrary reorientation is ideally accomplished by rotating the spacecraft about a line which is fixed in both the body and in space. This scheme has been found to be best suited for the case in which the initial and desired attitude states have small angular velocities. The second scheme is more general in that a general class of transition trajectories is introduced which, in principle, allows transfer between arbitrary orientation and angular velocity states. The method generates transition maneuvers in which the uncontrolled (free) initial and final states are matched in orientation and angular velocity. The forced transition trajectory is obtained by using a weighted average of the unforced forward integration of the initial state and the unforced backward integration of the desired state. The current effort is centered around practical validation of this second class of maneuvers. Of particular concern is enforcement of given control system constraints and methods for suboptimization by proper selection of maneuver initiation and termination times. Analogous reorientation strategies which force smooth transition in angular momentum and/or rotational energy are under consideration

IMPLICATIONS OF POLICY REGULATIONS ON LAND APPLICATIONS OF POULTRY LITTER

The growth of the poultry industry in Arkansas has exploded in the past decade. As a result, approximately 1.5 million tons of litter are produced every year. Concerns about possible contamination of ground and surface water from land applications of poultry litter have been raised. This paper compares four policy scenarios in terms of their efficiency and practicality to manage land applications of poultry litter. The results indicate that a litter tax per ton of litter applied could achieve the same level of litter control as that of a land tax on litter applications, but at a lower tax rate.Agricultural and Food Policy,

THE FEASIBILITY OF POULTRY LITTER TRANSPORTATION FROM ENVIRONMENTALLY SENSITIVE AREAS TO DELTA ROW CROP PRODUCTION

Arkansas ranks first in broiler production in the USA with more than a billion broiler and 1.5 million tons of litter produced in 1993. Transporting litter from western to eastern Arkansas can accomplish two goals: 1) avoid potential threat to clean water in western Arkansas and 2) can increase productivity of graded lands in the Delta. This paper examines the feasibility of litter transport from areas of high poultry concentrations to the Delta for use as a soil amendment. We establish the conditions for economical litter transport from source to destinations and determine the optimal rates of litter applications. The results suggest that it is economical to transport significant portions of litter.Livestock Production/Industries,

A high pressure, high temperature combustor and turbine-cooling test facility

A new test facility is being constructed for developing turbine-cooling and combustor technology for future generation aircraft gas turbine engines. Prototype engine hardware will be investigated in this new facility at gas stream conditions up to 2480 K average turbine inlet temperature and 4.14 x 10 to the 6th power n sq m turbine inlet pressure. The facility will have the unique feature of fully automated control and data acquisition through the use of an integrated system of mini-computers and programmable controllers which will result in more effective use of operating time, will limit the number of operators required, and will provide built in self protection safety systems. The facility and the planning and design considerations are described

OBTAINING LOWER AND UPPER BOUNDS ON THE VALUE OF SEASONAL CLIMATE FORECASTS AS A FUNCTION OF RISK PREFERENCES

A methodological approach to obtain bounds on the value of information based on an inexact representation of the decision makerÂ’s utility function is presented. Stochastic dominance procedures are used to derive the bounds. These bounds provide more information than the single point estimates associated with traditional decision analysis approach to valuing information, in that classes of utility functions can be considered instead of one specific utility function. Empirical results for valuing seasonal climate forecasts illustrate that the type of management strategy given by the decision makerÂ’s prior knowledge interacts with the decision makerÂ’s risk preferences to determine the bounds.Risk and Uncertainty,

A new approach for vibration control in large space structures

An approach for augmenting vibration damping characteristics in space structures with large panels is presented. It is based on generation of bending moments rather than forces. The moments are generated using bimetallic strips, suitably mounted at selected stations on both sides of the large panels, under the influence of differential solar heating, giving rise to thermal gradients and stresses. The collocated angular velocity sensors are utilized in conjunction with mini-servos to regulate the control moments by flipping the bimetallic strips. A simple computation of the rate of dissipation of vibrational energy is undertaken to assess the effectiveness of the proposed approach

Effects of gravity on laminar gas jet diffusion flames

Zero gravity effects on laminar gas jet diffusion flame