Space station rotational equations of motion

Dynamic equations of motion are developed which describe the rotational motion for a large space structure having rotating appendages. The presence of the appendages produce torque coupling terms which are dependent on the inertia properties of the appendages and the rotational rates for both the space structure and the appendages. These equations were formulated to incorporate into the Space Station Attitude Control and Stabilization Test Bed to accurately describe the influence rotating solar arrays and thermal radiators have on the dynamic behavior of the Space Station

Numerical simulations of mass loading in the tails of Bow Shock Pulsar Wind Nebulae

When a pulsar is moving through a partially ionized medium, a fraction of neutral Hydrogen atoms penetrate inside the pulsar wind and can be photo-ionized by the nebula UV radiation. The resulting protons remains attached to the magnetic field of the light leptonic pulsar wind enhancing its inertia and changing the flow dynamics of the wind. We present here the first numerical simulations of such effect in the tails of bow shock nebulae. We produce a set of different models representative of pulsars moving in the interstellar medium with different velocities, from highly subsonic to supersonic, by means of 2D hydrodynamic relativistic simulations. We compare the different tail morphologies with results from theoretical models of mass loading in bow shocks. As predicted by analytical models we observe a fast sideways expansion of the tail with the formation of secondary shocks in the ISM. This effect could be at the origin of the head-and-shoulder morphology observed in many BSPWNe.Comment: 7 pages, 5 figures, 1 tabl

Use of an Inertia Sphere to Damp the Angular Motions of Spinning Space Vehicles

A theoretical study was made of a device which might be used to damp the angular motions of spin-stabilized space vehicles with constant moments of inertia. the device was assumed to consist of a rate gyro, a servo control, and a rotor mounted in a single gimbal. The investigation was conducted by considering the general equations of motion of the vehicle-damper system and noting that simplification would result if the damper had a spherical inertia distribution. Such a distribution was assumed thereafter, and a control command was defined so that the gimbal angle would be proportional to the angular velocity of the vehicle about the gimbal axis. The resulting equations were linearized, and the Routh-Hurwitz criterion was applied to determine the conditions for stability. The study included two numerical examples showing possible application of inertia-sphere rate dampers. The general conditions for stability were found to be feasible for practical applications. A simplified stability criterion covers a large class of practical problems

On the dynamics of the general Bianchi IX spacetime near the singularity

We show that the complex dynamics of the general Bianchi IX universe in the vicinity of the spacelike singularity can be approximated by a simplified system of equations. Our analysis is mainly based on numerical simulations. The properties of the solution space can be studied by using this simplified dynamics. Our results will be useful for the quantization of the general Bianchi IX model.Comment: 20 pages, 5 figures, minor change

A survey of the theory of the Earth's rotation

The theory of the Earth's rotation and the geophysical phenomena affecting it is examined. First principles are reviewed and the problem of polar motion and UT1 variations is formulated in considerable generality and detail. The effects of Earth deformations and the solid Earth tides are analyzed

21st Century Welfare Provision is more than the "social insurance state": A reply to Paul Pierson

This article reflects on the important lecture The Welfare State Over the Very Long Run, delivered by Paul Pierson, at the London School of Economics on 8 November 2010, on the occasion of the launch of Oxford Handbook of the Welfare State. Pierson's explanation for what he sees as the surprising stability of the welfare state over the past three to four decades of permanent austerity is largely rooted in fears of electoral ret-ribution and organized interest opposition against social reform (cf. Pierson 2011). While, in a nutshell, Pierson's lecture was a restatement of his famous new politics thesis with a nod to rival theoretical accounts, the present paper tries to go beyond Pierson's account of change-resistant welfare states by adding a number of empirical as-pects and theoretical dimensions to the debate on the long-term transformation of the welfare state. Empirically, on the one hand, the paper highlights several significant qualitative changes in social insurance provision, macroeconomic policy priorities, la-bor market policy and regulation, industrial relations, old age pension, social services and social policy administration, that are largely absent from Pierson's portrayal, also given his choice of data. The observation of profound social reform raises important theoretical issues for the comparative study of welfare state development. Here the pa-per points to underappreciated theoretical mechanisms, especially dynamics of policy learning in mature welfare state. In sum, the paper observes more profound change on the dependent variable requiring both a softening and updating of the theoretical biases to path-dependent institutional inertia. If policy makers, contrary to received wisdom, do engage in major reforms in spite of many institutional obstacles and negative political incentives, what distin-guishes these actors and the institutional conditions under which they operate, from the seemingly more general case of welfare inertia? In conclusion, the article argues that the readiness to use information feedback from past performance, new ideas and expertise and the inspiring reforms successes in many countries, should count as important con-duits or mechanisms explaining reforms. -- Dieser Artikel beschäftigt sich mit dem bedeutenden Vortrag The Welfare State Over the Very Long Run, den Paul Pierson anlässlich der Herausgabe des Oxford Handbook of the Welfare State am 8. November 2010 an der London School of Economics gehalten hat (vgl. Pierson 2011). Piersons Erklärung für die seiner Meinung nach bemerkenswerte Stabilität des Wohlfahrtsstaates in den von permanenter Austerität geprägten vergangenen drei bis vier Jahrzehnten basiert im Wesentlichen auf der Angst der politischen Eliten vor der Abstrafung an der Wahlurne und dem Widerstand organisierter Interessen gegen Sozialreformen. Vorliegender Aufsatz beleuchtet sowohl die empirischen als auch die theoretischen Grenzen dieser These eines wandlungsresistenten Wohlfahrtsstaates. In empirischer Hinsicht weist er auf eine nicht unerhebliche Anzahl von qualitativen Veränderungen hin, etwa auf der Ebene der Sozialversicherung, makroökonomischer Politikprioritäten, der Arbeitsmarktpolitik und -regulierung, der Beziehungen von Arbeitgebern und Arbeitnehmern, Renten, sozialen Dienstleistungen und der Sozialverwaltung. Die Beobachtung grundlegender Sozialreformen werfen wichtige theoretische Fragen für das vergleichende Studium wohlfahrtstaatlicher Entwicklung auf: Was unterscheidet politische Entscheidungsträger und die institutionellen Bedingungen, unter denen sie agieren, von dem anscheinend weitaus üblicheren Fall von Reformträgheit, wenn diese Akteure - entgegen der landläufigen Meinung - trotz einer Vielzahl institutioneller Hindernisse und negativer politischer Anreize umfassende Reformen anstoßen? Als Schlussfolgerung argumentiert dieser Aufsatz, dass die Lehren vergangener Performanz, neue Ideen und Expertisen sowie anregende Reformerfolge in vielen Ländern als wichtige Mechanismen gelten müssen, mit denen sich wohlfahrtstaatliche Veränderungen erklären lassen.