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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Orbital transfer vehicle engine technology: Baffled injector design, fabrication, and verification

New technologies for space-based, reusable, throttleable, cryogenic orbit transfer propulsion are being evaluated. Supporting tasks for the design of a dual expander cycle engine thrust chamber design are documented. The purpose of the studies was to research the materials used in the thrust chamber design, the supporting fabrication methods necessary to complete the design, and the modification of the injector element for optimum injector/chamber compatibility.

Schneider, J. A.↗
NASA NTRS1938

Principles involved in the cooling of a finned and baffled cylinder

An analysis of the cooling problems for a finned cylinder is made on the basis of the known fundamental principles of heat transfer from pipes. Experimental results that support the analysis are presented. The results of previous investigations on the problem are evaluated on the basis of the analysis and the results. An illustration of the application of these principles to a specific problem is included.

Brevoort, M J↗
NASA NTRS1994

Impact of Optical Baffle on Antenna Pattern

One of the major concerns of antenna design for spacecraft applications is the effect of surrounding structures which can reflect and diffract the antenna's radiated energy and cause degradation in the antenna directivity, beam shape, and sidelobe levels.

Earth Observing System (EOS)↗
NASA NTRS2010

Vortex Shedding Inside a Baffled Air Duct

Common in the operation of both segmented and un-segmented large solid rocket motors is the occurrence of vortex shedding within the motor chamber. A portion of the energy within a shed vortex is converted to acoustic energy, potentially driving the longitudinal acoustic modes of the motor in a quasi-discrete fashion. This vortex shedding-acoustic mode excitation event occurs for every Reusable Solid Rocket Motor (RSRM) operation, giving rise to subsequent axial thrust oscillations. In order to better understand this vortex shedding/acoustic mode excitation phenomena, unsteady CFD simulations were run for both a test geometry and the full scale RSRM geometry. This paper covers the results from the subscale geometry runs, which were based on work focusing on the RSRM hydrodynamics. Unsteady CFD simulation parameters, including boundary conditions and post-processing returns, are reviewed. The results were further post-processed to identify active acoustic modes and vortex shedding characteristics. Probable locations for acoustic energy generation, and subsequent acoustic mode excitation, are discussed.

Davis, Philip↗
NASA NTRS2011

Study of Anti-Vortex Baffle Effect in Suppressing Swirling Flow in LOX Tank

Experimental results describing the hydraulic dynamic pump transfer matrix (Yp) for a cavitating J-2X oxidizer turbopump inducer+impeller tested in subscale waterflow are presented. The transfer function is required for integrated vehicle pogo stability analysis as well as optimization of local inducer pumping stability. Dynamic transfer functions across widely varying pump hydrodynamic inlet conditions are extracted from measured data in conjunction with 1D-model based corrections. Derived Dynamic transfer functions are initially interpreted relative to traditional Pogo pump equations. Water-to-liquid oxygen scaling of measured cavitation characteristics are discussed. Comparison of key dynamic transfer matrix terms derived from waterflow testing are made with those implemented in preliminary Ares Upper Stage Pogo stability modeling. Alternate cavitating pump hydraulic dynamic equations are suggested which better reflect frequency dependencies of measured transfer matrices.

Yang, H. Q.↗
NASA NTRSDate not supplied

Effects of Confinement on Flame Spread in Microgravity

Solid fuel combustion experiments aboard the ISS examine the effects of confinement on a concurrent, purely-forced-flow flame spread in microgravity environment. The results for a thin, cotton-fiberglass-blended textile fabric fuel are presented. Flat baffles of differing materials are used to alter the radiative boundary conditions with transparent polycarbonate, black anodized aluminum (reflectance ~ 0), and highly polished aluminum (reflectance ~ 1). The baffles are parallel to the fuel sheet and placed symmetrically on each side. The inter-baffle distance is varied to change the boundary conditions for the flow. In all tests, samples are ignited at the upstream leading edge and allowed to burn to completion. Results show that the flame reaches a steady length and spread rate at low flow speeds (< 15 cm/s) for all tested inter-baffle distances. As the distance decreases, the flame length and spread rate first increase then decrease showing an optimal inter-baffle distance. For all baffle types, the flame either fails to ignite or extinguishes before reaching the end of the sample when the inter-baffle distance is too small (~ 1 cm). This is attributed to the reduction of oxygen supply to the flame zone and heat loss to the baffles. The results also show at the same inter-baffle distance, flame length and spread rate are highest for polished aluminum baffles, and lowest for transparent polycarbonate baffles. The differences are most prominent at intermediate tested baffle distances. While the radiative heat feedback from the baffles is expected to increase when the baffle distance decreases, the combustion is limited by the reduced oxygen supply. Near this limit, flame lengths and spread rates are similar for all baffle types.

Microgravity↗
NASA NTRS1993

AXAF-I ghost ray study: On orbit case

The problem of baffles for control of singly reflected (and nonreflected) ghost rays is considered. The theory of baffle design for Wolter Type I grazing incidence optics is reviewed, and a set of sample baffle parameters is obtained subject to the assumptions of nominal mirror figures and perfect manufacture and alignment of baffles. It is found that baffles forward of the optics (in the thermal precollimator) and between the mirror elements (at the CAP) are sufficient to allow the simultaneous ghost image and vignetting requirements to be satisfied for HRMA shells P1H1, P3H3, and P4H4. However, these baffles are not sufficient for the innermost shell P6H6; at best the requirements are slightly violated and there is no margin for tolerances. The addition of a baffle interior to the P6 space at an axial station about one third of the way forward from the aft end of the paraboloid will allow the ghost ray and vignetting requirements to be met. The minimum ghost ray angles and the vignetting angles are sensitive functions of the baffle positions and radii; tolerances of considerably better than 1 mm will be required. The sensitivities are coupled and correlated; further investigations should be undertaken in order to obtain baffle parameters which, combined with likely achievable tolerances, will minimize the risk of the vignetting/ghost ray requirements not being met. The lightweight carbon-epoxy composite used for thermal baffles has insufficient X-ray opacity to be a suitable material for construction of the controlling X-ray baffles; further study is needed to determine an appropriate material and to investigate its thermal and mechanical implications.

Gaetz, T. J.↗
NASA NTRS2003

Investigating Morphological Stability of Faceted Interfaces with Axial Heat Processing (AHP) Technique

Successful processing of homogeneous semiconductor single crystals from their melts depends strongly on precise control of thermal and fluid flow conditions near the solid/liquid interface. In this project, we utilize a novel crystal growth technique called Axial Heat Processing (AHP) that uses a baffle, positioned inside the melt near the interface, to supply and/or conduct heat axially to the interface. The baffle, which may or may not have a heater encased in it, can promote more stable and planar growth as well as reduce buoyancy driven convection. The latter is because the baffle reduces the aspect ratio of the melt as it separates the melt into three sections, above the baffle, in the feed gap between the baffle and the crucible wall, and below the baffle between the baffle base and the interface. AHP also enables a close monitoring and/or control of thermal boundaries near the solid/liquid interface during crystal growth by means of thermocouples placed in the baffle. The interface is kept planar when a heating element in the baffle is used. However, a proper choice of melt height is necessary to keep the interface planar when using the baffle without a heater. This study addresses the influence of melt height and growth velocity on the segregation profile of AHP-grown Sb doped Ge single crystals.

Abbaschian, Reza↗
NASA NTRS1972

Neutral-particle wake method for measuring the atmospheric temperature from a satellite.

Description of a method that would permit a satellite-borne neutral mass spectrometer to measure the atmospheric temperature. The spectrometer examines the partial pressure variations that occur as the wake of a small rectangular baffle is swept across the entrance orifice of the spectrometer. For a given baffle size and for a mounting distance from the orifice, the depth of the resulting pressure minimum depends only on the thermal velocity or temperature of the observed species. The validity of the method can be checked by measuring the wake characteristics of more than one species and/or by employing each of several baffle sizes. The theory includes the effect of a finite orifice size, finite baffle length, and the backscattering of particles from the baffle into the orifice. It is found that a suitable baffle arrangement can be achieved that will permit the temperature to be measured over at least the range normally encountered in the thermosphere (200 to 2000 K) and, depending on the sensitivity and background pressure of the spectrometer, over an altitude range of about 140 to 600 km.

Brace, L. H.↗
NASA NTRS1985

Some unique experiments on receptivity

The objective of this study is to determine whether or not a solid trailing edge is required to produce efficient coupling between sound and instability waves in a shear layer. Instability waves in the shear layer of a subsonic jet, excited externally by a point sound source, were first visualized by using a phase-locked flow visualization technique. Various means were adopted to shield the sound reaching the nozzle lip. It was found that the low frequency sound couples more efficiently at distances downstream of the nozzle exit. To substantiate the findings further, a supersonic screeching jet was tested such that it passed through a small opening in a baffle placed parellel to the exit plane. The measured feedback or screech frequencies, and also the excited flow disturbances, were found to change drastically on traversing the baffle axially. Similar conclusions were reached when a second baffle was placed downstream of the first baffle, and the effects of moving the first baffle on the feedback frequency of sound generated by flow impingement on the second baffle were examined. It is argued that sound waves passing through the mixing layer of a jet can excite flow instability without the benefit of assistance and coupling at the trailing edge.

Ahuja, K. K.↗
NASA NTRS2001

Microgravity Science Glovebox Investigations SUBSA

Solidification Using a Baffle in Sealed Ampoules (SUBSA) is a Microgravity Science Glovebox Investigation manifested for the UF2 flight, on the U.S. Orbiter 111, to the International Space Station (ISS). SUBSA complements the "parent" flight investigation CG13 (Space-and Groundbased Crystal Growth Using a Baffle). During directional solidification, the disk-shaped baffle acts as a partition, creating a small melt zone at the solid-liquid interface. As a result, the level of buoyancy-driven convection at the interface is significantly reduced. In space, the baffle will reduce convection driven by residual micro acceleration. The baffle reduces the Rayleigh number (Ra) of the melt by a factor of 103. The combined effect of the baffle and microgravity will yield a reduction in Ra by a factor of 107 to 109 approaching effectively the acceleration conditions in "nanogravity". The results of ground based tests and numerical modeling will be presented. The furnace for directional solidification (flight hardware and the ground unit) was developed by Tec-Masters Inc. The flight ampoules were produced jointly at Rensselaer, Tec-Masters Inc. and Crystallod Inc.

Ostrogorsky, A.↗
NASA NTRS1987

Development of response models for the Earth Radiation Budget Experiment (ERBE) sensors. Part 3: ERBE scanner measurement accuracy analysis due to reduced housekeeping data

The accuracy of scanner measurements was evaluated when the sampling frequency of sensor housekeeping (HK) data was reduced from once every scan to once every eight scans. The resulting increase in uncertainty was greatest for sources with rapid or extreme temperature changes. This analysis focused on the mirror attenuator mosaic (MAM) baffle and plate and scanner radiometer baffle due to their relatively high temperature changes during solar calibrations. Since only solar simulator data were available, the solar temperatures were approximated on these components and the radiative and thermal gradients in the MAM baffle due to reflected sunlight. Of the two cases considered for the MAM plate and baffle temperatures, one uses temperatures obtained from the ground calibration. The other attempt uses temperatures computed from the MAM baffle model. This analysis shows that the heat input variations due largely to the solar radiance and irradiance during a scan cycle are small. It also demonstrates that reasonable intervals longer than the current HK data acquisition interval should not significantly affect the estimation of a radiation field in the sensor field-of-view.

Choi, Sang H.↗
NASA NTRS2008

Subscale Injector Testing to Support J-2X Engine Development

The J-2X engine being pursued for the Ares I will be a derivative of the J-2 engine developed by Pratt & Whitney Rocketdyne (PWR). As part of the engine development, a subscale injector was fabricated by PWR and hot-fire tested at NASA s Marshall Space Flight Center (MSFC) to evaluate performance data. This subscale injector had a reduced injector diameter and fewer elements than the full scale design, but the element density (#elements / injector area), and element geometries nearly identical to the full scale design. Three different materials were used for the LOX posts in order to test for durability. The subscale injector included 46 standard elements and 6 baffle elements, corresponding to the ratio of baffled elements to core elements in the full scale design. The baffle elements were included to demonstrate thermal compatibility of the baffles and to more closely represent the full scale performance. Fifteen hot-fire tests were conducted totaling over 200 seconds of mainstage time on the injector. Chamber pressures with oxygen/hydrogen propellants ranged from 870-1380 psig with mixture ratios ranging from 4.8-6.1. Fuel manifold inlet temperatures were varied from 190 to 300 R. Modular, water cooled, calorimeter chamber assemblies were used to provide heating rate data and evaluate the effects of characteristic length (L*). Performance was evaluated relative to the resulting characteristic velocity (C*) efficiency. Performance met the value required in order to proceed with this design for the full scale hardware. Hardware inspections show no evidence of cracking at the tip of the LOX post for any of the materials tested. Minor erosion of the baffle element tips was observed in the early testing. A design change was quickly implemented and tested, and this change resolved the issue. Development of the J-2X is continuing with this element density and design.

Protz, Christopher↗