The dynamic phenomena of a tethered satellite: NASA's first Tethered Satellite Mission, TSS-1

The tethered satellite system (TSS) was envisioned as a means of extending a satellite from its base (space shuttle, space station, space platform) into a lower or higher altitude in order to more efficiently acquire data and perform science experiments. This is accomplished by attaching the satellite to a tether, deploying it, then reeling it in. When its mission is completed, the satellite can be returned to its base for reuse. If the tether contains a conductor, it can also be used as a means to generate and flow current to and from the satellite to the base. When current is flowed, the tether interacts with the Earth's magnetic field, deflecting the tether. When the current flows in one direction, the system becomes a propulsive system that can be used to boost the orbiting system. In the other direction, it is a power generating system. Pulsing the current sets up a dynamic oscillation in the tether, which can upset the satellite attitude and preclude docking. A basic problem occurs around 400-m tether length, during satellite retrieval when the satellite's pendulous (rotational) mode gets in resonance with the first lateral tether string mode. The problem's magnitude is determined by the amount of skiprope present coming into this resonance condition. This paper deals with the tethered satellite, its dynamic phenomena, and how the resulting problems were solved for the first tethered satellite mission (TSS-1). Proposals for improvements for future tethered satellite missions are included. Results from the first tethered satellite flight are summarized

Augmentation of information in educational objects: Effectiveness of arrows and pictures as information for actions in instructional objects

The use of information and communication technology (ICT) in education is now central to facilitating links between learners, resources and instructors. Regardless of whether it is used in distance education or educational objects, ICT enables educators to package education opportunities in an increasing number of alternative ways so as best to meet the varying needs of the end user. Currently, one of the challenges that face instructors is to develop materials that enhance the learner-content interaction by reducing extraneous cognitive load while at the same time facilitating learning. This study explored the effectiveness of pictorial information and augmentation in instructions and educational objects. Dual coding theory is used to suggest that information that can be processed via separate but interconnected systems will facilitate faster processing and deeper learning of the information. University students were randomly assigned to six experimental conditions to perform a novel task using six different instruction manuals. A 3 (text, text-pictorial, text-pictorial-arrows) X 2 (picture of object vs. no picture of object) design was used to test whether augmenting text with pictorial information provided additional valuable information in instructional settings. Results partially support this multimedia effect; participants exhibited superior performance in a Text-Pictorial and Text-Pictorial-Arrows format over Text format. A picture of the object also facilitated superior performance on both the assembly and operating tasks, especially in a text format. Overall, combinations of text-pictorial and text-pictorial-arrows facilitated faster assembly and operation; they reduced errors, extra procedures, and unsuccessful assemblies (uncorrected errors). Results also support the idea that arrows convey unique types of information and function. In particular, arrows may attune people to important information and/or convey information movement that guides actions during tasks. Practical implications are discussed in relation to the type of information combinations that may lead to superior instructional design of instructional objects and research, including how to reduce errors of omission

Energy expenditure analysis of redesigned mechanical assists for medium girder bridge

U.S. Army bridge crew soldiers perform tough manual material handling (MMH) tasks during the assembly of a Medium Girder Bridge (MGB). The bridge parts are very heavy and are manually lifted from pallets, carried to the construction site and assembled with other bridge parts. An energy expenditure study on the soldiers handling the bridge parts revealed that the energy expenditure rate of the soldiers exceeds the NIOSH prescribed safety limit of 3.5 Kcal/min. This leads to high risk of musculoskeletal disorders. The study deals with modifying the first redesign of mechanical assists for medium girder bridge (MGB) and studying the energy expended by soldiers during MGB construction while using the modified assists and comparing it to the energy expended by soldiers while using the current assists. The first redesign required minor modification to improve usability and performance. An effort was put to address these issues. The approach for this research involved redesign based on a field test performed with the first redesigned assists and observation of the bridge building process using recorded video tapes. The thesis research involved design modifications, prototype manufacturing and energy expenditure study using Energy Expenditure Prediction Program (EEPP). The EEPP study revealed that the redesigned mechanical assists reduced the average energy expenditure rate of soldiers by 33%. The average team energy expenditure was reduced by 50% --Abstract, page iii

Development of assembly and joint concepts for erectable space structures

The technology associated with the on-orbit assembly of tetrahedral truss platforms erected of graphite epoxy tapered columns is examined. Associated with the assembly process is the design and fabrication of nine member node joints. Two such joints demonstrating somewhat different technology were designed and fabricated. Two methods of automatic assembly using the node designs were investigated, and the time of assembly of tetrahedral truss structures up to 1 square km in size was estimated. The effect of column and node joint packaging on the Space Shuttle cargo bay is examined. A brief discussion is included of operating cost considerations and the selection of energy sources. Consideration was given to the design assembly machines from 5 m to 20 m. The smaller machines, mounted on the Space Shuttle, are deployable and restowable. They provide a means of demonstrating the capabilities of the concept and of erecting small specialized platforms on relatively short notice

Evaluating Optimum Levels Of Detail For 3d Interactive Aviation Maintenance Instructions

With the aviation industry shifting from paper based maintenance instructions to digital maintenance instructions, there needs to be a standard for what goes into creating the digital instructions. This study was done to determine what the optimum level of detail for 3D interactive aviation maintenance instructions. The definition of optimum for this study was: lowest amount of geometrical data with lowest rendering needed for comprehension and ease of use

Interaktiiviset kokoonpano-ohjeet

Industrial products are increasingly varying, and the assembly of customized or unique products is slow, expensive, and prone to errors. Conventional static assembly drawings and instructions are suboptimal in supporting complex and dynamic assembly operations. The main objective of the study was to investigate if interactive assembly instructions could substitute the current documents instructing assembly in the case company. Two approaches, 3D instructions and augmented reality (AR) instructions, were developed based on literature review. 3D instructions presented the assembly procedure in steps in which the assembly of the parts is animated. The instructions were based directly on the 3D model of the assembly object. AR instructions utilized the same assembly sequence as 3D instructions. AR instructions were viewed using a head-mounted display, which presented the assembly step animations spatially overlaid on the physical assembly. The developed instructions were evaluated in a user study. The tests were observed by the author, and the participants answered to a post-study questionnaire that concerned subjective efficiency and user acceptance. Both AR instructions and 3D instructions received positive feedback and were evaluated more efficient than the currently used assembly drawings. The features of the interactive assembly drawings address directly the problems of the current assembly documents. Hence, it was concluded that interactive assembly instructions could be used instead of the current assembly drawings and work instructions. However, the complexity of the case company products require that the instructions must be configurable to enable their implementation.Teolliset tuotteet kehittyvät jatkuvasti monipuolisemmin muunneltaviksi, ja samalla niiden kokoonpano muuttuu hankalammaksi ja kalliimmaksi. Perinteiset kuviin ja tekstiin perustuvat kokoonpanokuvat ja työohjeet ovat monin tavoin riittämättömiä ohjeistamaan monimutkaisia ja dynaamisia kokoonpanotehtäviä. Tässä työssä tavoitteena oli tutkia, voisiko interaktiivisilla kokoonpano-ohjeilla korvata kohdeyrityksessä nykyisin käytössä olevat työohjeet ja kokoonpanokuvat. Työssä kehitettiin aikaisempien tutkimusten pohjalta kaksi erilaista interaktiivista ohjeistustapaa. 3D-ohjeet opastavat kokoonpanoa vaihe vaiheelta näyttäen jokaisen osan asennuksen animoidusti. 3D-ohjeet luodaan suoraan kokoonpanon 3D-mallin pohjalta. Toiseksi menetelmäksi valikoitui lisättyä todellisuutta (augmented reality, AR) hyödyntävät ohjeet. AR-ohjeet perustuvat 3D-ohjeita varten luotuihin vaiheistuksiin sekä animaatioihin. AR-ohjeita katsotaan silmikkonäytöllä, joka näyttää ohjeiden virtuaaliset komponentit todellisen kokoonpanon päällä. Ohjeiden toimivuutta testattiin käyttäjäkokeissa. Testeissä havainnoitiin koehenkilöiden toimintaa, ja lisäksi he vastasivat kyselyyn. Kyselyllä selvitettiin, miten tehokkaana koehenkilöt pitivät testattuja ohjeita verrattuna heidän tavallisesti käyttämiin kokoonpanokuviin. Sekä AR- että 3D-ohjeet saivat positiivista palautetta, ja koehenkilöt kokivat niiden toimivan tavallisia kokoonpanokuvia paremmin. Interaktiiviset ohjeet ja niiden tärkeimmät ominaisuudet vastaavat nykyisten kokoonpanokuvien ja työohjeiden ongelmakohtiin. Työn johtopäätöksenä voidaankin todeta, että interaktiiviset kokoonpano-ohjeet sopisivat korvaamaan nykyiset kokoonpanokuvat sekä työohjeet. Tuotteiden monimutkaisuus kuitenkin edellyttää, että ohjeet pitää pystyä konfiguroimaan varianttikohtaisesti

Design, fabrication and test of prototype furnace for continuous growth of wide silicon ribbon

A program having the overall objective of growing wide, thin silicon dendritic web crystals quasi-continuously from a semi-automated facility is discussed. The design considerations and fabrication of the facility as well as the test and operation phase are covered; detailed engineering drawings are included as an appendix. During the test and operation phase of the program, more than eighty growth runs and numerous thermal test runs were performed. At the conclusion of the program, 2.4 cm wide web was being grown at thicknesses of 100 to 300 micrometers. As expected, the thickness and growth rate are closely related. Solar cells made from this material were tested at NASA-Lewis and found to have conversion efficiencies comparable to devices fabricated from Czochralski material

Self-replicating systems: A systems engineering approach

A first approach to conceptualize self-replicating systems was developed from past and present abstract theories. The engineering elements of self-replicating systems are defined in terms of a basic reference system. A number of options are investigated. The growth characteristics and their problems are analyzed, the mathematics of various exponential growth options are outlined, and the problems of universal parts production and systems closure are discussed. Selected areas of further study are defined and a 20 year development and demonstration program is presented