Engineering topics
Tien, J.
Publications and source records attributed to Tien, J..
An overview of formation flying technology development for the Terrestrial Planet Finder mission
The objective of the Terrestrial Planet Finder (TPF) mission is to find and characterize earth-like planets orbiting other stars. Three architectural options are under consideration for this mission: a formation-flying interferometer (FFI), a structurally-connected interferometer, and a coronagraph.
TPF formation acquisition sensor testbed
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Formation acquisition sensor for the TPF mission
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Autonomous formation flying sensor for the Star Light Mission
The StarLight Mission, an element of NASA's Origins Program, was designed for first-time demonstration of two technologies: formation flying optical interferometry between spacecraft and autonomous precise formation flying of an array of spacecraft to support optical interferometry. The design overview and results of the technology effort are presented in this paper.
The instrument on NASA's GRACE Mission: Augmentation of GPS to achieve unprecedented gravity field measurements
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The instrument on NASA's GRACE Mission: Augmentation of GPS to achieve unprecedented gravity field measurements
This paper will describe the design and on-orbit performance of the GRACE Instrument Processing Unit (IPU) that integrates most of the critical science functions required by the GRACE mission to perform its gravity science and atmospheric radio occultation tasks.
Autonomous formation flying sensor for the Starlight Mission
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From AFF to CCNT: JPL's evolving family of multi-function constellation transceivers
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microGPS: On-orbit Demonstration of a New Approach to GPS to Space Applications
In February 1998 Student Nitric Oxide Explorer (SNOE) was successfully launched and began scientific observations.
Superalloy composition modeling
Development of a predictive method for determination of the gamma/gamma prime phase fields, i.e., gamma prime volume fraction as a function of the multicomponent composition, is described. The cluster variation method used for binary alloys in which the precipitated phase is coherent with the matrix phase is extended for application to the multicomponent coherent gamma/gamma prime nickel-based superalloys. It is shown that the cluster variation method can accurately describe the equilibrium (incoherent) gamma/gamma prime phase fields in the binary Ni-Al phase diagram. The gamma/gamma prime phase field for the Ni-Cr-Al ternary phase diagram is computed as a function of temperature. A reasonable fit results between the calculated and the experimental diagrams. The modeling of the six-component Ni-Cr-Al-Co-Mo-Ti base superalloy and the effect of Ni substitution of Co are discussed.
Role of cobalt in nickel base superalloys
The effect of cobalt or substituting for cobalt on the mechanical properties of nickel-based superalloys is discussed. Waspaloy, UDIMET 700, and NIMONIC 115, which are representative of Ni-Cr-Co-Al-Ti-Mo superalloys having different gamma prime contents which are strengthened by a heavily alloyed matrix, coherent gamma prime precipitates, and carbides at the grain boundaries. Microstructure and in situ and extracted phase STEM micro-analysis were used to evaluate the three alloys.