16,053 research outputs found

    Advanced expander test bed program

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    The Advanced Expander Test Bed (AETB) is a key element in NASA's Chemical Transfer Propulsion Program for development and demonstration of expander cycle oxygen/hydrogen engine technology component technology for the next space engine. The AETB will be used to validate the high-pressure expander cycle concept, investigate system interactions, and conduct investigations of advanced missions focused components and new health monitoring techniques. The split-expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust

    A row-by-row axial turbine process model based on a one-dimensional thermofluid network approach

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    A detailed turbine process model has been developed, based on a stage-by-stage discretisation using 1D flow elements. The complete turbine is represented by these flow elements in which the fundamental mass, energy and momentum conservation equations for compressible flow through 1D "stationary channels" and 1D "rotating channels" were solved. The required closure relations were obtained from the various loss coefficients for turbine stators, rotors and leakage flows which were characterised using correlations available in the literature. Several of the commonly applied loss calculation methods were investigated. A test case of a real turbine obtained in the literature was used to validate the model. Three models with different discretisation schemes were tested. In each of these schemes the stator and rotor flow passages were represented by a different number of elements along the radial direction. A number of hypothetical anomalies that often occur in industrial turbines were applied to the test case to demonstrate how the modelling approach can be applied in practice. The model agrees well with the test data for the nominal case and several of the off-design cases. For the nominal case the maximum deviation in total pressure of <2% occurs after the first stage and there is little variation between the results obtained with the three different models. The total enthalpy values are predicted within an accuracy of <1%, again with similar results obtained by the three different models. All three models predict the efficiency well for a broad range of relative mass flow rates. A slight improvement in the prediction of losses is observed in the models that use more elements to represent each stator and rotor passage

    Planck pre-launch status: HFI ground calibration

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    Context. The Planck satellite was successfully launched on May 14th 2009. We have completed the pre-launch calibration measurements of the High Frequency Instrument (HFI) on board Planck and their processing. Aims. We present the results of the pre-launch calibration of HFI in which we have multiple objectives. First, we determine instrumental parameters that cannot be measured in-flight and predict parameters that can. Second, we take the opportunity to operate and understand the instrument under a wide range of anticipated operating conditions. Finally, we estimate the performance of the instrument built. Methods. We obtained our pre-launch calibration results by characterising the component and subsystems, then by calibrating the focal plane at IAS (Orsay) in the Saturne simulator, and later from the tests at the satellite level carried out in the CSL (Liège) cryogenic vacuum chamber. We developed models to estimate the instrument pre-launch parameters when no measurement could be performed. Results. We reliably measure the Planck-HFI instrument characteristics and behaviour, and determine the flight nominal setting of all parameters. The expected in-flight performance exceeds the requirements and is close or superior to the goal specifications

    Radial turbine cooling

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    Radial turbines have been used extensively in many applications including small ground based electrical power generators, automotive engine turbochargers and aircraft auxiliary power units. In all of these applications the turbine inlet temperature is limited to a value commensurate with the material strength limitations and life requirements of uncooled metal rotors. To take advantage of all the benefits that higher temperatures offer, such as increased turbine specific power output or higher cycle thermal efficiency, requires improved high temperature materials and/or blade cooling. Extensive research is on-going to advance the material properties of high temperature superalloys as well as composite materials including ceramics. The use of ceramics with their high temperature potential and low cost is particularly appealing for radial turbines. However until these programs reach fruition the only way to make significant step increases beyond the present material temperature barriers is to cool the radial blading

    Screening of energy efficient technologies for industrial buildings' retrofit

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    This chapter discusses screening of energy efficient technologies for industrial buildings' retrofit

    Are a set of microarrays independent of each other?

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    Having observed an m×nm\times n matrix XX whose rows are possibly correlated, we wish to test the hypothesis that the columns are independent of each other. Our motivation comes from microarray studies, where the rows of XX record expression levels for mm different genes, often highly correlated, while the columns represent nn individual microarrays, presumably obtained independently. The presumption of independence underlies all the familiar permutation, cross-validation and bootstrap methods for microarray analysis, so it is important to know when independence fails. We develop nonparametric and normal-theory testing methods. The row and column correlations of XX interact with each other in a way that complicates test procedures, essentially by reducing the accuracy of the relevant estimators.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS236 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    SoK: Design Tools for Side-Channel-Aware Implementations

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    Side-channel attacks that leak sensitive information through a computing device's interaction with its physical environment have proven to be a severe threat to devices' security, particularly when adversaries have unfettered physical access to the device. Traditional approaches for leakage detection measure the physical properties of the device. Hence, they cannot be used during the design process and fail to provide root cause analysis. An alternative approach that is gaining traction is to automate leakage detection by modeling the device. The demand to understand the scope, benefits, and limitations of the proposed tools intensifies with the increase in the number of proposals. In this SoK, we classify approaches to automated leakage detection based on the model's source of truth. We classify the existing tools on two main parameters: whether the model includes measurements from a concrete device and the abstraction level of the device specification used for constructing the model. We survey the proposed tools to determine the current knowledge level across the domain and identify open problems. In particular, we highlight the absence of evaluation methodologies and metrics that would compare proposals' effectiveness from across the domain. We believe that our results help practitioners who want to use automated leakage detection and researchers interested in advancing the knowledge and improving automated leakage detection

    Space shuttle OMS helium regulator design and development

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    Analysis, design, fabrication and design verification testing was conducted on the technological feasiblity of the helium pressurization regulator for the space shuttle orbital maneuvering system application. A prototype regulator was fabricated which was a single-stage design featuring the most reliable and lowest cost concept. A tradeoff study on regulator concepts indicated that a single-stage regulator with a lever arm between the valve and the actuator section would offer significant weight savings. Damping concepts were tested to determine the amount of damping required to restrict actuator travel during vibration. Component design parameters such as spring rates, effective area, contamination cutting, and damping were determined by test prior to regulator final assembly. The unit was subjected to performance testing at widely ranging flow rates, temperatures, inlet pressures, and random vibration levels. A test plan for propellant compatibility and extended life tests is included

    Study of tooling concepts for manufacturing operations in space Final report

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    Mechanical linkage device for manufacturing operations with orbital workshop
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