Modal identities for multibody elastic spacecraft: An aid to selecting modes for simulation

The question: Which set of modes furnishes a higher fidelity math model of dynamics of a multibody, deformable spacecraft (hinges-free or hinges-locked vehicle modes) is answered. Two sets of general, discretized, linear equations of motion of a spacecraft with an arbitrary number of deformable appendages, each articulated directly to the core body, are obtained using the above two families of modes. By a comparison of these equations, ten sets of modal identities are constructed which involve modal momenta coefficients and frequencies associated with both classes of modes. The sums of infinite series that appear in the identities are obtained in terms of mass, and first and second moments of inertia of the appendages, core body, and vehicle by using certain basic identities concerning appendage modes. Applying the above identities to a four-body spacecraft, the hinges-locked vehicle modes are found to yield a higher fidelity model than hinges-free modes, because the latter modes have nonconverging modal coefficients; a characteristic proved and illustrated

Momentum accumulation due to solar radiation torque, and reaction wheel sizing, with configuration optimization

This paper has a two-fold objective: determination of yearly momentum accumulation due to solar radiation pressure, and optimum reaction wheel sizing. The first objective is confronted while determining propellant consumption by the attitude control system over a spacecraft's lifetime. This, however, cannot be obtained from the daily momentum accumulation and treating that constant throughout the year, because the orientation of the solar arrays relative to the spacecraft changes over a wide range in a year, particularly if the spacecraft has two arrays, one normal and the other off-normal to different extent at different times to the sun rays. The paper first develops commands for the arrays for tracking the sun, the arrays articulated to earth-pointing spacecraft with two rotational degrees of freedom, and spacecraft in an arbitrary circular orbit. After developing expressions for solar radiation torque due to one or both arrays, arranged symmetrically or asymmetrically relative to the spacecraft bus, momentum accumulation over an orbit and then over a year are determined. The remainder of the paper is concerned with designing reaction wheel configurations. Four-, six-, and three-wheel configurations are considered, and for given torque and momentum requirements, their cant angles with the roll/yaw plane are optimized for minimum power consumption. Finally, their momentum and torque capacities are determined for one-wheel failure scenario, and six configurations are compared and contrasted

MINAT MAHASISWA TERHADAP PENGEMBANGAN DIRI UNTUK MENGHASILKAN NILAI TAMBAH (SUATU SURVAI DI FAKULTAS ILMU KEOLAHRAGAAN UNY)

The present research aims at exploring whether the students had high interest in self development to acquire additional values (supporting skills and knowledge in work getting). The populations involved were the students of Faculty of Sport Science, Yogyakarta State University registered as students in the academic year of 2000/2001. The samples were 150 students. This study used the survey method and the data were collected using the instruments to measure students’ interest in self development to get additional values. The instruments’ validity was gained from content validity, and the reliability of the instruments was 0.854 with the status of reliable. The results show that 11.33% of the respondents had low interest, 64% of them were in fair, and 24.67% of the students had high interest in self development

Integrability and the Kerr-(A)dS black hole in five dimensions

In this note we prove that the Hamilton-Jacobi equation for a particle in the five dimensional Kerr-(A)dS black hole is separable, for arbitrary rotation parameters. As a result we find an irreducible Killing tensor. We also consider the Klein-Gordon equation in this background and show that this is also separable. Finally we comment on extensions and implications of these results.Comment: 4 pages, RevTeX. v2: minus sign typos in eq. (17) and (18) of published version correcte

A review of regulatory instruments to control environmental externalities from the transport sector

This study reviews regulatory instruments designed to reduce environmental externalities from the transport sector. The study finds that the main regulatory instruments used in practice are fuel economy standards, vehicle emission standards, and fuel quality standards. Although industrialized countries have introduced all three standards with strong enforcement mechanisms, most developing countries have yet to introduce fuel economy standards. The emission standards introduced by many developing countries to control local air pollutants follow either the European Union or United States standards. Fuel quality standards, particularly for gasoline and diesel, have been introduced in many countries mandating 2 to 10 percent blending of biofuels, 10 to 50 times reduction of sulfur from 1996 levels, and banning lead contents. Although inspection and maintenance programs are in place in both industrialized and developing countries to enforce regulatory standards, these programs have faced several challenges in developing countries due to a lack of resources. The study also highlights several factors affecting the selection of regulatory instruments, such as countries'environmental priorities and institutional capacities.Transport Economics Policy&Planning,Transport and Environment,Energy Production and Transportation,Environmental Economics&Policies,Environment and Energy Efficiency

Fiscal policy instruments for reducing congestion and atmospheric emissions in the transport sector : a review

This paper reviews the literature on the fiscal policy instruments commonly used to reduce transport sector externalities. The findings show that congestion charges would reduce vehicle traffic by 9 to 12 percent and significantly improve environmental quality. The vehicle tax literature suggests that every 1 percent increase in vehicle taxes would reduce vehicle miles by 0.22 to 0.45 percent and CO2 emissions by 0.19 percent. The fuel tax is the most common fiscal policy instrument; however its primary objective is to raise government revenues rather than to reduce emissions and traffic congestion. Although subsidizing public transportation is a commonpractice, reducing emissions has not been the primary objective of such subsidies. Nevertheless, it is shown that transport sector emissions would be higher in the absence of both public transportation subsidies and fuel taxation. Subsidies are also the main policy tool for the promotion of clean fuels and vehicles. Although some studies are very critical of biofuel subsidies, the literature is mostly supportive of clean vehicle subsidies.Transport Economics Policy&Planning,Environmental Economics&Policies,Transport and Environment,Taxation&Subsidies,Transport in Urban Areas