Specification for a Program for an Interative Aeroelastic Solution (PIAS)

An engineering and software specification which was written for a computer program to calculate aeroelastic structural loads including the effects of nonlinear aerodynamics is presented. The procedure used in the program for an iterative aeroelastic solution (PIAS) is to alternately execute two computer codes: one to calculate aerodynamic loads for a specific wing shape, and another to calculate the deflected shape caused by this loading. A significant advantage to the design of PIAS is that the initial aerodynamic module can be replaced with others. The leading edge vortex (LEV) program is used as the aerodynamic module in PIAS. This provides the capability to calculate aeroelastic loads, including the effects of a separation induced leading edge vortex. The finite element method available in ATLAS Integrated structural analysis and design system is used to determine the deflected wing shape for the applied aerodynamics and inertia loads. The data management capabilities in ATLAS are used by the execution control monitor (ECM) of PIAS to control the solution process

PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 2: User's manual (version 3.0)

A comprehensive description of user problem definition for the PAN AIR (Panel Aerodynamics) system is given. PAN AIR solves the 3-D linear integral equations of subsonic and supersonic flow. Influence coefficient methods are used which employ source and doublet panels as boundary surfaces. Both analysis and design boundary conditions can be used. This User's Manual describes the information needed to use the PAN AIR system. The structure and organization of PAN AIR are described, including the job control and module execution control languages for execution of the program system. The engineering input data are described, including the mathematical and physical modeling requirements. Version 3.0 strictly applies only to PAN AIR version 3.0. The major revisions include: (1) inputs and guidelines for the new FDP module (which calculates streamlines and offbody points); (2) nine new class 1 and class 2 boundary conditions to cover commonly used modeling practices, in particular the vorticity matching Kutta condition; (3) use of the CRAY solid state Storage Device (SSD); and (4) incorporation of errata and typo's together with additional explanation and guidelines

PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 4: Maintenance document (version 1.1)

The Maintenance Document is a guide to the PAN AIR software system, a system which computes the subsonic or supersonic linear potential flow about a body of nearly arbitrary shape, using a higher order panel method. The document describes the over-all system and each program module of the system. Sufficient detail is given for program maintenance, updating and modification. It is assumed that the reader is familiar with programming and CDC (Control Data Corporation) computer systems. The PAN AIR system was written in FORTRAN 4 language except for a few COMPASS language subroutines which exist in the PAN AIR library. Structured programming techniques were used to provide code documentation and maintainability. The operating systems accommodated are NOS 1.2, NOS/BE and SCOPE 2.1.3 on the CDC 6600, 7600 and Cyber 175 computing systems. The system is comprised of a data management system, a program library, an execution control module and nine separate FORTRAN technical modules. Each module calculates part of the posed PAN AIR problem. The data base manager is used to communicate between modules and within modules. The technical modules must be run in a prescribed fashion for each PAN AIR problem. In order to ease the problem of supplying the many JCL cards required to execute the modules, a separate module called MEC (Module Execution Control) was created to automatically supply most of the JCL cards. In addition to the MEC generated JCL, there is an additional set of user supplied JCL cards to initiate the JCL sequence stored on the system

PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 4: Maintenance document (version 3.0)

The Maintenance Document Version 3.0 is a guide to the PAN AIR software system, a system which computes the subsonic or supersonic linear potential flow about a body of nearly arbitrary shape, using a higher order panel method. The document describes the overall system and each program module of the system. Sufficient detail is given for program maintenance, updating, and modification. It is assumed that the reader is familiar with programming and CRAY computer systems. The PAN AIR system was written in FORTRAN 4 language except for a few CAL language subroutines which exist in the PAN AIR library. Structured programming techniques were used to provide code documentation and maintainability. The operating systems accommodated are COS 1.11, COS 1.12, COS 1.13, and COS 1.14 on the CRAY 1S, 1M, and X-MP computing systems. The system is comprised of a data base management system, a program library, an execution control module, and nine separate FORTRAN technical modules. Each module calculates part of the posed PAN AIR problem. The data base manager is used to communicate between modules and within modules. The technical modules must be run in a prescribed fashion for each PAN AIR problem. In order to ease the problem of supplying the many JCL cards required to execute the modules, a set of CRAY procedures (PAPROCS) was created to automatically supply most of the JCL cards. Most of this document has not changed for Version 3.0. It now, however, strictly applies only to PAN AIR version 3.0. The major changes are: (1) additional sections covering the new FDP module (which calculates streamlines and offbody points); (2) a complete rewrite of the section on the MAG module; and (3) strict applicability to CRAY computing systems

Calculating Cross Sections of Composite Interstellar Grains

Interstellar grains may be composite collections of particles of distinct materials, including voids, agglomerated together. We determine the various optical cross sections of such composite grains, given the optical properties of each constituent, using an approximate model of the composite grain. We assume it consists of many concentric spherical layers of the various materials, each with a specified volume fraction. In such a case the usual Mie theory can be generalized and the extinction, scattering, and other cross sections determined exactly. We find that the ordering of the materials in the layering makes some difference to the derived cross sections, but averaging over the various permutations of the order of the materials provides rapid convergence as the number of shells (each of which is filled by all of the materials proportionately to their volume fractions) is increased. Three shells, each with one layer of a particular constituent material, give a very satisfactory estimate of the average cross section produced by larger numbers of shells. We give the formulae for the Rayleigh limit (small size parameter) for multi-layered spheres and use it to propose an ``Effective Medium Theory'' (EMT), in which an average optical constant is taken to represent the ensemble of materials. Multi-layered models are used to compare the accuracies of several EMTs already in the literature.Comment: 29 pages, 6 figures, accepted for publication in the Astrophysical Journal (part 1, scheduled in Vol. 526, #1, Nov. 20

The Ammount of Interstellar Carbon Locked in Solid Hydrogenated Amorphous Carbon

We review the literature and present new experimental data to determine the amount of carbon likely to be locked in form of solid hydrogenated amorphous carbon (HAC) grains. We conclude on the basis of a thorough analysis of the intrinsic strength of the C-H stretching band at 3.4 micron that between 10 and 80 ppM H of carbon is in the form of HAC grains. We show that it is necessary to know the level of hydrogenation (H/C) of the interstellar HAC to determine more precisely the amount of carbon it ties up. We present optical constants, photoluminescence spectroscopy, and IR absorption spectroscopy for a particular HAC sample that is shown to have a 3.4 micron absorption feature that is quantatively consistent with that observed in the diffuse interstellar medium.Comment: This paper is 14 pages long with 5 figures and will appear in the 1 December 1999 issue of Ap

TranAir: A full-potential, solution-adaptive, rectangular grid code for predicting subsonic, transonic, and supersonic flows about arbitrary configurations. User's manual

The TranAir computer program calculates transonic flow about arbitrary configurations at subsonic, transonic, and supersonic freestream Mach numbers. TranAir solves the nonlinear full potential equations subject to a variety of boundary conditions modeling wakes, inlets, exhausts, porous walls, and impermeable surfaces. Regions with different total temperature and pressure can be represented. The user's manual describes how to run the TranAir program and its graphical support programs

GIADA: its status after the Rosetta cruise phase and on-ground activity in support of the encounter with comet 67P/Churyumov-Gerasimenko

GIADA (Grain Impact Analyser and Dust Accumulator) on-board the Rosetta mission to comet 67P/Churyumov-Gerasimenko was designed to study the physical and dynamical properties of dust particles ejected by the comet during the encounter. In this paper we report the results of the analysis of data collected by GIADA during the past seven years of the cruise phase. During this period the GIADA detection subsystems were switched on for periodic in-flight payload checkouts to monitor their state of-health including potential changes in its performance that could affect its data collection. Only slight variations in sensitivity and dynamical range were identified that will not affect the GIADA measurement capability during the Rosetta comet encounter and rendezvous phase. The GIADA microbalance system detected the presence of low-volatility material over a period of about 169 days when the GIADA cover remained partially opened. It is highly probable that this material originated from the spacecraft itself, as a spacecraft’s outgassing was observed by the ROSINA mass spectrometer (on-board Rosetta) during the cruise phase. The identification of the low-volatility mass deposited on the microbalances as self-contamination will allow us to evaluate the mass rate background to be subtracted from the GIADA science data. These results obtained from GIADA cruise data analysis coupled with laboratory calibration data obtained from measurements using the GIADA spare model for selected cometary dust analogs will be the basis for the interpretation of the GIADA scientific data

Mid-Infrared Spectropolarimetric Constraints on the Core-Mantle Interstellar Dust Model

In the framework of the silicate core-carbonaceous organic mantle interstellar dust model, the bulk of the visual/near-IR extinction and the entire polarization are from nonspherical and aligned core-mantle grains. The 3.4 micron C-H and 9.7 micron Si-O absorption features, respectively arising from the hydrocarbon mantle and the amorphous silicate core, are expected to be polarized to a modestly different degree. Spectropolarimetric observations toward the same lines of sight both in the 3.4 micron region and in the 9.7 micron region would be of great value to test the core-mantle dust model. The fact that the 3.4 micron feature is not polarized along the line of sight toward the Galactic center source IRS 7 is not yet sufficient to reject the core-mantle model due to the lack of spectropolarimetric observation of this region in the 9.7 micron region.Comment: 11 pages, 2 figues, submitted to The Astrophysical Journal Letter

67P/C-G inner coma dust properties from 2.2 au inbound to 2.0 auoutbound to the Sun

GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the Rosetta space probe is designed to measure the momentum, mass and speed of individual dust particles escaping the nucleus of comet 67P/Churyumov-Gerasimenko (hereafter 67P). From 2014 August to 2016 June, Rosetta escorted comet 67P during its journey around the Sun. Here, we focus on GIADA data taken between 2015 January and 2016 February which included 67P's perihelion passage. To better understand cometary activity and more specifically the presence of dust structures in cometary comae, we mapped the spatial distribution of dust density in 67P's coma. In this manner, we could track the evolution of high-density regions of coma dust and their connections with nucleus illumination conditions, namely tracking 67P's seasons. We also studied the link between dust particle speeds and their masses with respect to heliocentric distance, i.e. the level of cometary activity. This allowed us to derive a global and a local correlation of the dust particles' speed distribution with respect to the H2O production rate. © 2016 The Authors.Peer Reviewe