Gas-Surface Interactions in Low-Earth Orbit

Moe, Kenneth; Moe, Mildred M.

doi:10.1063/1.3562825

Cited by 32 publications

(33 citation statements)

References 34 publications

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“…19 Instead, these unions expanded rapidly in the 1950s and 1960s after Democrats in various states (partly pressured by existing unions in other jurisdictions) changed collective bargaining laws in order to facilitate organizing efforts. 19 Instead, these unions expanded rapidly in the 1950s and 1960s after Democrats in various states (partly pressured by existing unions in other jurisdictions) changed collective bargaining laws in order to facilitate organizing efforts.…”

Section: Policy Structures and Organized Interestsmentioning

confidence: 99%

After the “Master Theory”: Downs, Schattschneider, and the Rebirth of Policy-Focused Analysis

Hacker¹,

Pierson²

2014

Persp on Pol

288

127

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Drawing on the pioneering work of Anthony Downs, political scientists have tended to characterize American politics as a game among undifferentiated competitors, played out largely through elections, with outcomes reflecting how formal rules translate election results into legislative votes. In this perspective, voters, campaigns, elections, and the ideological distribution of legislators merit extensive scrutiny. Other features of the political environment-most notably, the policies these legislators help create and the interest groups that struggle over these policies-are deemed largely peripheral. However, contemporary politics often looks very different than the world described by Downs. Instead, it more closely resembles the world depicted by E. E. Schattschneider-a world in which policy and groups loom large, the influence of voters is highly conditional, and the key struggle is not over gaining office but over reshaping governance. Over the last twenty years, a growing body of scholarship has emerged that advances this corrective vision-an approach we call "policy-focused political science." In this framework, politics is centrally about the exercise of government authority for particular substantive purposes. Such exercises of authority create the "terrain" for political struggle, profoundly shaping both individual and group political behavior. More important, because policies can be so consequential, they also serve as the "prize" for many of the most enduring political players, especially organized interest groups. The payoffs of a policy-focused perspective include a more accurate portrayal of the institutional environment of modern politics, an appreciation for the fundamental importance of organized groups, a better understanding of the dynamics of policy change, and a more accurate mapping of interests, strategies, and influence. These benefits are illustrated through brief examinations of two of the biggest changes in American politics over the last generation: asymmetric partisan polarization and the growing concentration of income at the top.

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Section: Policy Structures and Organized Interestsmentioning

confidence: 99%

After the “Master Theory”: Downs, Schattschneider, and the Rebirth of Policy-Focused Analysis

Hacker¹,

Pierson²

2014

Persp on Pol

288

127

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“…Satellite drag coefficients have been calculated for various satellites using on-orbit data 1 , and although this method of obtaining in-situ data is ideal, the cost prohibitive nature of on-orbit experimentation limits progress in the study of gas-surface interactions applicable to spacecraft-environment interactions. In addition to the limited availability of on-orbit experimentation, there are inherent difficulties involved in obtaining satellite drag coefficients using on-orbit accelerometer data.…”

Section: Introductionmentioning

confidence: 99%

“…The ability to measure momentum transfer and subsequent drag coefficients in a ground-based facility has the potential to allow for improved space-situational awareness in terms of accuracy of orbit determination and propagation, along with inference of atmospheric density from total satellite drag. The drag coefficient can be calculated by ( 1 ) where F D is the total drag force acting on the satellite, ρ is the atmospheric density, v is the orbital velocity of the satellite relative to the rotating atmosphere, A is the area of the satellite normal to the velocity vector, and C D is the satellite drag coefficient. Thermospheric densities have been inferred by satellites with known mass and equipped with on-board accelerometers using ( 2 ) where a drag is the acceleration due to drag, , and m is the mass of the satellite 4 .…”

Section: Introductionmentioning

confidence: 99%

Drag Measurements in a Simulated Low-Earth Orbit Environment

Maldonado

Ketsdever

2015

53rd AIAA Aerospace Sciences Meeting

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An overview of the development of a magnetically filtered atomic oxygen plasma source and the application of the source to study low-Earth orbit drag on different geometries is presented. Plasma diagnostics show that the magnetic filter plasma source produces atomic oxygen ions (O + ) with streaming energies equivalent to the relative orbital environment of approximately 5eV and can supply the appropriate density for LEO simulation. Previous research has demonstrated that momentum transfer between ions and metal surfaces is equivalent to the momentum transfer expected for neutral molecules with similar energy, due to charge exchange occurring prior to momentum transfer. Total drag measurements of aluminum cuboid geometries of varying length to diameter ratios immersed in the extracted plasma plume are presented as a function of streaming ion energy. The plasma source can be operated at a variety of discharge currents and gas flow rates, of which the plasma parameters downstream of the source are dependent. The characteristics of the generated plasma were examined as a function of these operating parameters to optimize the production of O + ions with energy relevant to LEO applications, where the ram energy of the ions due to the motion of the satellite relative to the LEO plasma is high (e.g. 7800 m/s, which corresponds to approximately 5 eV of kinetic energy for O+ ions). The plasma downstream of the source consists of streaming ions with energy of approximately 5 eV and ion species fraction that is approximately 90% O + . NomenclatureA ref = cross-sectional area a drag = acceleration due to drag AO = atomic oxygen B = magnetic field strength C D = coefficient of drag ChAOSS = Chamber for Atmospheric and Orbital Space Simulation d = separation distance E = energy e = elementary charge eV = electron volt F D = total drag force LEO = low Earth orbit MFOPS = magnetically filtered oxygen plasma source m = mass nNTS = nano-Newton thrust stand n p = particle number density ρ = density z = charge state RPA = retarding potential analyzer RGA = residual gas analyzer

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“…He had a fascination for the potential of the capacitor, and even before they established ELAB, he had started a research group in digital technology. This group applied for the funding necessary to develop and build a computer, but failed -partly due to the plans being too ambitious, and that the Norwegian Council for Technical and Scientific research (NTNF) wanted to focus its recourses on the Computer Centre in Oslo [25].…”

Section: The Birth Of Computing At Nth/sintefmentioning

confidence: 99%

“…This article presents some of the themes of this book, which will be due for release some time in 2009. I'm thankful to a number of people for kindly sharing their knowledge on the NTNU Computer history [21,22,23,24,25,26,27]. 2 A notable exception is [11].…”

Section: Introductionmentioning

confidence: 99%

Tool or Science? The History of Computing at the Norwegian University of Science and Technology

Nordal

2009

IFIP Advances in Information and Communication Technology

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Abstract. One may characterize the history of computing at the Norwegian University of Science and Technology by a tension between the computer as a tool in other disciplines and computer science as discipline in itself. This tension has been latent since the pioneering period of the 1950s until today. This paper shows how this have been expressed in the early attempts to take up computing at the University, and how it gave the Division of Computer Science a fairly rough start when it opened in 1972.

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Gas-Surface Interactions in Low-Earth Orbit

Cited by 32 publications

References 34 publications

After the “Master Theory”: Downs, Schattschneider, and the Rebirth of Policy-Focused Analysis

After the “Master Theory”: Downs, Schattschneider, and the Rebirth of Policy-Focused Analysis

Drag Measurements in a Simulated Low-Earth Orbit Environment

Tool or Science? The History of Computing at the Norwegian University of Science and Technology

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