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  • 1
    Publikationsdatum: 2019-07-13
    Beschreibung: The design of the next generation of space access vehicles has led to a unique flight test that blends the space and flight research worlds. The new space vehicle designs, such as the X-33 vehicle and Reusable Launch Vehicle (RLV), are powered by linear aerospike rocket engines. Conceived of in the 1960's, these aerospike engines have yet to be flown, and many questions remain regarding aerospike engine performance and efficiency in flight. To provide some of these data before flying on the X-33 vehicle and the RLV, a spacecraft rocket engine has been flight-tested atop the NASA SR-71 aircraft as the Linear Aerospike SR-71 Experiment (LASRE). A 20 percent-scale, semispan model of the X-33 vehicle, the aerospike engine, and all the required fuel and oxidizer tanks and propellant feed systems have been mounted atop the SR-71 airplane for this experiment. A major technical objective of the LASRE flight test is to obtain installed-engine performance flight data for comparison to wind-tunnel results and for the development of computational fluid dynamics-based design methodologies. The ultimate goal of firing the aerospike rocket engine in flight is still forthcoming. An extensive design and development phase of the experiment hardware has been completed, including approximately 40 ground tests. Five flights of the LASRE and firing the rocket engine using inert liquid nitrogen and helium in place of liquid oxygen and hydrogen have been successfully completed.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-1998-206567 , H-2280 , NAS 1.15:206567 , Sep 15, 1998 - Sep 17, 1998; Reno, NV; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-08-15
    Beschreibung: This final report summarizes the design effort for the construction of a visible-infrared imaging spectrometer for planetary missions, funded by NASA under the Planetary Instrument Definition and Development Program. The goal was to design and develop a prototype brassboard pushbroom imaging spectrometer covering the 0.35 gm to 2.5 gm spectral region using a simplified optical layout that would minimize the size, mass and parts count of the instrument by using a single holographic grating to disperse and focus light from a single slit onto both the infrared and visible focal plane arrays. Design approaches are presented and analyzed, along with problems encountered and recommended solutions to those problems. In particular, a new type of grating, incorporating two sets of rulings and a filter in a layered structure, is presented for further development.
    Schlagwort(e): Optics
    Materialart: NASA-CR-201921 , NAS 1.26:201921
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    facet.materialart.
    Unbekannt
    Elsevier
    In:  Marine Chemistry, 65 (3-4). pp. 227-244.
    Publikationsdatum: 2017-08-21
    Beschreibung: The excretion of siderophores and the reduction of organic iron-complexes at the cell surface are common reactions of terrestrial plants, fungi and bacteria in response to low availability of iron. However, there is much less evidence for the use of these strategies by marine phytoplankton. It has been argued that siderophore excretion is inefficient in an aquatic environment due to rapid diffusion. This study examines how diffusion and chemical reactions in the microenvironment of a phytoplankton cell influence the efficiency of both strategies to increase the bioavailability of iron and to reduce iron stress. A numerical model of the cell surroundings is presented that calculates the concentration distribution for different iron species and allows to study the effect of siderophores or surface reductases. It calculates the efficiency of these mechanisms, defined as the quotient between the increase in iron uptake rate and the excretion rate of siderophores or electrons, needed to obtain this increase. The dependence of this efficiency on rates of iron coordination reactions, on diffusivity, and on the kinetics of iron uptake is discussed with the aid of some analytical calculations.
    Materialart: Article , PeerReviewed
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Unbekannt
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 29 . pp. 1666-1681.
    Publikationsdatum: 2020-08-04
    Beschreibung: Wind-driven flow in a baroclinic quasigeostrophic channel with simple bottom topography is studied in a model with reduced physics and degrees of freedom as an analogy to the Antarctic Circumpolar Current. For a sinusoidal topography an approximate analytical solution is found using a low-order spectral model. Resonance of baroclinic Rossby waves can lead to different flow regimes of which one is a blocked state, where most of the momentum, imparted to the fluid by the wind stress, is transferred to the earth by bottom form stress. For some parameter values there are both resonant and nonresonant solutions to the model equations. It is shown that these results of the low-order model apply also to a more complicated spectral model with sinusoidal but also with Gaussian ridge topography. The steady states of these models are found numerically using a continuation algorithm. In the case of the ridge topography, the resonant and nonresonant steady states coexist over a wide range of topography heights.
    Materialart: Article , PeerReviewed
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Unbekannt
    Geologisch-Paläontologisches Institut der Universität Kiel
    In:  Berichte aus dem Sonderforschungsbereich 313, Veränderungen der Umwelt - Der Nördliche Nordatlantik, 62 . Geologisch-Paläontologisches Institut der Universität Kiel, Kiel, Germany, 62 pp.
    Publikationsdatum: 2019-02-08
    Materialart: Report , NonPeerReviewed
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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