Henny J.G.L.M. Lamers and Jopseph P. Cassinelli (eds.), Introduction to Stellar Winds

Space Science Reviews -     

An approximated method of calculating the cellular insert influence in the carrying capacity of the direct-flow labyrinth seal

A method for calculating the flowrate of the gas flowing through the cellular insert cells over the labyrinth seal strip is proposed. The gas density is taken to be average with respect to the decisive section. It is assumed that jets flowing out of cells disrupt the direct flow of the labyrinth seal. A practical implementation of the method is confirmed by the known experimental data.     

Numerical study of transient interchamber processes when reaching the SPRE operational conditions

A comprehensive numerical study of transient interchamber processes occurring when reaching the SPRE operational conditions is carried out. A conjugate problem under consideration includes nonstationary operation of an igniter heating, ignition and subsequent nonstationary and turbulent burning of a solid-propellant charge; nonstationary three-phase homo-heterogeneous flow of combustion products in the combustion chamber, nozzle and downstream of the nozzle block of a rocket engine; motion of a nozzle block cover. The calculation results are presented.     

Review of numerical simulations for high-speed, turbulent cavity flows

High speed flows inside cavities are encountered in many aerospace applications including weapon bays of combat aircraft as well as landing gear. The flow field inside these cavities is associated with strong acoustic effects, unsteadiness and turbulence. With increasing emphasis on stealth operation of unmanned combat air vehicles and noise concerns near airports, cavity flows attracted the interest of many researchers in aerodynamics and aeroacoustics. Several attempts were made using wind tunnel experimentation and computational fluid dynamics analyses to understand the complex flow physics associated with cavity flows and alleviate their adverse effects via flow control. The problem proved to be complex, and current research revealed a very complex flow with several flow phenomena taking place. With the aid of experiments, CFD methods were validated and then used for simulations of several cavity configurations. The detached-eddy and large-eddy simulation methods proved invaluable for these studies and their application highlights the need for advanced turbulence simulation techniques in aerospace. The success of these methods and a summary of the current status of the experimental and computational progress over the past twenty years is summarised in this paper.     

Alice: The rosetta Ultraviolet Imaging Spectrograph

We describe the design, performance and scientific objectives of the NASA-funded ALICE instrument aboard the ESA Rosetta asteroid flyby/comet rendezvous mission. ALICE is a lightweight, low-power, and low-cost imaging spectrograph optimized for cometary far-ultraviolet (FUV) spectroscopy. It will be the first UV spectrograph to study a comet at close range. It is designed to obtain spatially-resolved spectra of Rosetta mission targets in the 700–2050 Å spectral band with a spectral resolution between 8 Å and 12 Å for extended sources that fill its ～0.05^ × 6.0^ field-of-view. ALICE employs an off-axis telescope feeding a 0.15-m normal incidence Rowland circle spectrograph with a toroidal concave holographic reflection grating. The microchannel plate detector utilizes dual solar-blind opaque photocathodes (KBr and CsI) and employs a two-dimensional delay-line readout array. The instrument is controlled by an internal microprocessor. During the prime Rosetta mission, ALICE will characterize comet 67P/Churyumov-Gerasimenko's coma, its nucleus, and nucleus/coma coupling; during cruise to the comet, ALICE will make observations of the mission's two asteroid flyby targets and of Mars, its moons, and of Earth's moon. ALICE has already successfully completed the in-flight commissioning phase and is operating well in flight. It has been characterized in flight with stellar flux calibrations, observations of the Moon during the first Earth fly-by, and observations of comet C/2002 T7 (LINEAR) in 2004 and comet 9P/Tempel 1 during the 2005 Deep Impact comet-collision observing campaign.     

Velocity Shear Induced Phenomena in Solar Atmosphere

We present a brief overview of the probable velocity-shear induced phenomena in solar plasma flows. Shear-driven MHD wave oscillations may be the needed mechanism for the generation of solar Alfvén waves, for the transmission of fast waves through the transition region, and for the acceleration of the solar wind. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of Fast Variations in Electron Fluxes in the Gap Region Using the Normalized Range Method Based on Measurement Data on the SiriusSat-1 Satellite

Cosmic Research - The use of the normalized range method for an analysis of the fast variability of electron fluxes in near-Earth space is proposed. This method makes it possible to conclude...     

Magnetic holes in the solar wind and their relation to mirror-mode structures

Data obtained by the Ulysses magnetometer and solar wind analyzer have been combined to study the properties of magnetic holes in the solar wind between 1 and 5.4 AU and to 23° south latitude. Although the plasma surrounding the holes was generally stable against the mirror instability, there are indications that the holes may have been remnants of mirror mode structures created upstream of the points of observation. Those indications include: (1) For the few holes for which proton or alpha-particle pressure could be measured inside the hole, the ion thermal pressure was always greater than in the plasma adjacent to the holes. (2) The plasma surrounding many of the holes was marginally stable for the mirror mode, while the plasma environment of all the holes was significantly closer to mirror instability than was the average solar wind. (3) The plasma containing trains of closely spaced holes was closer to mirror instability than was the plasma containing isolated holes. (4) The near-hole plasma had much higher ion (ratio of thermal to magnetic pressure) than did the average solar wind.     

Comparisons of Sensitivity Improvement Techniques for Linear Optimal Control Systems

It is well known that there are several ways to define a sensitivity function in the time domain. The results are reported of a study in which these definitions are compared. Controllers designed on the basis of these sensitivity functions are related to each other and conclusions are drawn about their usefulness in control system design.