53 research outputs found

    Proceedings of the NASA Workshop on Atomic Oxygen Effects

    Get PDF
    A workshop was held to address the scientific issues concerning the effects of atomic oxygen on materials in the low Earth orbital (LEO) environment. The program included 18 invited speakers plus contributed posters covering topics such as LEO spaceflight experiments, interaction mechanisms, and atomic oxygen source development. Discussion sessions were also held to organize a test program to evaluate atomic oxygen exposure facilities. The key issues raised in the workshop were: (1) the need to develop a reliable predictive model of the effects of long-term exposure of materials to the LEO environment; (2) the ability of ground-based exposure facilities to provide useful data for development of durable materials; and (3) accurate determination of the composition of the LEO environment. These proceedings include the invited papers, the abstracts for the contributed posters, and an account of the test program discussion sessions

    Fifth Annual Workshop on Space Operations Applications and Research (SOAR 1991), volume 2

    Get PDF
    Papers given at the Space Operations and Applications Symposium, host by the NASA Johnson Space Center on July 9-11, 1991 are given. The technical areas covered included intelligent systems, automation and robotics, human factors and life sciences, and environmental interactions

    Eighteenth Space Simulation Conference: Space Mission Success Through Testing

    Get PDF
    The Institute of Environmental Sciences' Eighteenth Space Simulation Conference, 'Space Mission Success Through Testing' provided participants with a forum to acquire and exchange information on the state-of-the-art in space simulation, test technology, atomic oxygen, program/system testing, dynamics testing, contamination, and materials. The papers presented at this conference and the resulting discussions carried out the conference theme 'Space Mission Success Through Testing.

    NASA Tech Briefs, Spring 1984

    Get PDF
    Topics include: NASA TU Services: Technology Utilization services that can assist you in learning about and applying NASA technology. New Product Ideas: A summary of selected innovations of value to manufacturers for the development of new products; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Life Sciences; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences

    Research and Technology, 1994

    Get PDF
    This report selectively summarizes the NASA Lewis Research Center's research and technology accomplishments for the fiscal year 1994. It comprises approximately 200 short articles submitted by the staff members of the technical directorates. The report is organized into six major sections: Aeronautics, Aerospace Technology, Space Flight Systems, Engineering and Computational Support, Lewis Research Academy, and Technology Transfer. A table of contents and author index have been developed to assist the reader in finding articles of special interest. This report is not intended to be a comprehensive summary of all research and technology work done over the past fiscal year. Most of the work is reported in Lewis-published technical reports, journal articles, and presentations prepared by Lewis staff members and contractors. In addition, university grants have enabled faculty members and graduate students to engage in sponsored research that is reported at technical meetings or in journal articles. For each article in this report a Lewis contact person has been identified, and where possible, reference documents are listed so that additional information can be easily obtained. The diversity of topics attests to the breadth of research and technology being pursued and to the skill mix of the staff that makes it possible

    Development and Implementation of Diagnostics for Unsteady Small-scale Plasma Plumes

    Get PDF
    This research seeks to increase the applicable range and sensitivity of Triple Langmuir Probes (TLPs) and Retarding Potential Analyzers (RPAs) in the characterization of sub-centimeter scale, unsteady plasmas found in micropropulsion and other non-propulsive applications. The validation of these plasma diagnostics is accomplished by their implementation in the plume of a Micro Liquid-fed Pulsed Thruster (MiLiPulT) prototype developed and MEMS fabricated by the Johns Hopkins University Applied Physics Laboratory. A current-mode TLP (CM-TLP) theory of operation for the thin-sheath and the transitional regimes is expanded to include the Orbital Motion Limited regime applicable to low density plasmas. An optimized CM-TLP bias circuit employing operational amplifiers in both a differential amplifier configuration as well as a voltage follower configuration has been developed to adequately amplify current signals in instances where traditional current measuring techniques are no longer valid. This research also encompasses novel sub-microampere signal amplification in the presence of substantial common-mode noise as well as several a priori electromagnetic interference elimination and filtering techniques. The CM-TLP wires used in the experiments were designed with a radius of 37.5 micron and a length of 5 mm. Measurements were taken in the plume of the MiLiPulT at 2.0 cm, 6.0 cm and 10.0 cm downstream of the exit using a linear translation stage. Reduced electron temperature and electron number density profiles for a set of filtered CM-TLP raw currents are presented. The results indicate increased accuracy due to successful amplification of CM-TLP current signals at the risk of op-amp saturation due to inherent electrical noise of the plasma source. This research also includes the experimental validation of two new and distinct collimating RPA design types. Specifically, these design improvements include a 406 micron diameter single channel bore and a multi-channel plate (MCP) consisting of sixty-four 2 micron diameter bores, respectively. Both of these collimators relax the Debye length constraints within the electrode series and increase the instrument\u27s range while minimizing the presence of space charge limitations. The single channel needle also has the added advantage of providing a relatively small cross-section to the incident plasma, thus minimizing pressure gradients and shock effects inherent to bulkier instrumentation. Experimental results obtained in the plume of the MiLiPulT are benchmarked against those of a traditional gridded RPA (having a 650 micron grid wire gap) and are reduced using an iterative fuzzy logic algorithm. Modifications to the classical RPA current collection theory include a thorough treatment of geometrical flux limitations due to an electrically floating cylindrical channel of high diameter to length aspect ratio. The differences between true and effective RPA collimating channel transparencies in the presence of a Maxwellian plasma are also addressed

    Laser Atmospheric Wind Sounder (LAWS) phase 1. Volume 2

    Get PDF
    This report summarizes and documents the results of the 12-month phase 1 work effort. The objective of phase 1 was to establish the conceptional definition of the laser atmospheric wind sounder (LAWS) sensor system, including accommodations analyses to ensure compatibility with the Space Station Freedom (SSF) and the Earth Observing System (EOS) Polar Orbiting Platform (POP). Various concepts were investigated with trade studies performed to select the configuration to be carried forward to the phase 2 Preliminary Design Definition. A summary of the LAWS system and subsystem trade studies that were performed leading to the baseline design configuration is presented in the appendix. The overall objective of the LAWS Project is to define, design, and implement an operational space based facility, LAWS, for accurate measurement of Earth wind profiles. Phase 1 addressed three major areas: (1) requirements definition; (2) instrument concepts and configurations; and (3) performance analysis. For the LAWS instrument concepts and configurations, the issues which press the technological state of the art are reliable detector lifetime and laser performance and lifetime. Lag angle compensation, pointing accuracy, satellite navigation, and telescope design are significant technical issues, but they are considered to be currently state of the art. The primary issues for performance analysis concern interaction with the atmosphere in terms of backscatter and attenuation, wind variance, and cloud blockage. The phase 1 tasks were formulated to address these significant technical issues and demonstrate the technical feasibility of the LAWS concept. Primary emphasis was placed on analysis/trade and identification of candidate concepts. Promising configurations were evaluated for performance, sensitivities, risks, and budgetary costs. Lockheed's baseline LAWS configuration is presented

    Solar powered electric propulsion spacecraft study Final report

    Get PDF
    Mission capability improvement for unmanned planetary exploration spacecraft by using solar photovoltaic power systems with electric propulsion thrustor system
    corecore