Challenges in the development of the orbiter radiator system

Major technical challenges which were met in the design and development of the Space Shuttle Orbiter Radiator System are discussed. This system rejects up to 30 kW of waste heat from eight individual radiators having a combined surface area of 175 sq m. The radiators, which are deployable, are mounted on the inside of the payload bay doors for protection from aerodynamic heating during ascent and re-entry. While in orbit the payload bay doors are opened to expose the radiators for operation. An R21 coolant loop accumulates waste heat from various components in the Orbiter and delivers the heat to the radiators for rejection to space. Specific challenges included high acoustically induced loads during lift-off, severe radiating area constraints, demanding heat load control requirements, and long life goals. Details of major design and analysis efforts are discussed. The success of the developed hardware in satisfying mission objectives showed how well the design challenge was met

Non-equilibrium electromagnetic fluctuations: Heat transfer and interactions

The Casimir force between arbitrary objects in equilibrium is related to scattering from individual bodies. We extend this approach to heat transfer and Casimir forces in non-equilibrium cases where each body, and the environment, is at a different temperature. The formalism tracks the radiation from each body and its scatterings by the other objects. We discuss the radiation from a cylinder, emphasizing its polarized nature, and obtain the heat transfer between a sphere and a plate, demonstrating the validity of proximity transfer approximation at close separations and arbitrary temperatures.Comment: 4 pages, 2 figures, published version, minor changes (e.g. typos

Spatiotemporal Infrared Measurement of Interface Temperatures During Water Droplet Evaporation on a Nonwetting Substrate

High-fidelity experimental characterization of sessile droplet evaporation is required to understand the interdependent physical mechanisms that drive the evaporation. In particular, cooling of the interface due to release of the latent heat of evaporation, which is not accounted for in simplified vapor-diffusion-based models of droplet evaporation, may significantly suppress the evaporation rate on nonwetting substrates, which support tall droplet shapes. This suppression is counteracted by convective mass transfer from the droplet to the air. While prior numerical modeling studies have identified the importance of these mechanisms, there is no direct experimental evidence of their influence on the interfacial temperature distribution. Infrared thermography is used here to simultaneously measure the droplet volume, contact angle, and spatially resolved interface temperatures for water droplets on a nonwetting substrate. The technique is calibrated and validated to quantify the temperature measurement accuracy; a correction is employed to account for reflections from the surroundings when imaging the evaporating droplets. Spatiotemporally resolved interface temperature data, obtained via infrared thermography measurements, allow for an improved prediction of the evaporation rate and can be utilized to monitor temperature-controlled processes in droplets for various lab-on-a-chip applications

Probing non-Gaussianities in the CMB on an incomplete sky using surrogates

We demonstrate the feasibility to generate surrogates by Fourier-based methods for an incomplete data set. This is performed for the case of a CMB analysis, where astrophysical foreground emission, mainly present in the Galactic plane, is a major challenge. The shuffling of the Fourier phases for generating surrogates is now enabled by transforming the spherical harmonics into a new set of basis functions that are orthonormal on the cut sky. The results show that non-Gaussianities and hemispherical asymmetries in the CMB as identified in several former investigations, can still be detected even when the complete Galactic plane (|b| < 30{\deg}) is removed. We conclude that the Galactic plane cannot be the dominant source for these anomalies. The results point towards a violation of statistical isotropy.Comment: 9 pages, 13 figures, accepted by Physical Review

Influence Of Interactions Between Turbulence And Radiation On Transmissivities In Hypersonic Turbulent Boundary Layers

In the current paper, a high-fidelity large eddy simulation solver is coupled to our modified line-by-line radiative transport equation solver to study the effects of absorption turbulence-radiation interations in a hypersonic turbulent boundary layer, representative of the Orion CEV entering Earth\u27s atmosphere, at peak heating condition. The turbulent and radiation fields represent extreme conditions typical of Orion, as the simulated boundary layer represents the region of high turbulence coupled to region of highest incident radiation. A simplification in the calculation of molecular spectra with a single temperature property database in allows for tractable calculation of spectral properties. A comparison of wall directed intensities show the effects of absorption turbulence-radiation interactions due to radiation emitted in the shock layer is minimal, although a slight decrease in boundary layer transmissivities is predicted. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc

Study Of Turbulence-radiation Interaction In Hypersonic Turbulent Boundary Layers

In the paper, we conduct direct numerical simulations (DNS) to investigate the effect of turbulence-radiation interaction (TRI) in hypersonic turbulent boundary layers, representative of the Orion crew exploration vehicle (CEV) at peak heating condition during reentry. The radiative transfer equation (RTE) is solved using the tangent slab approximation. 1 The RTE solver is line-by-line (LBL) accurate, making use of a developed efficient spectral database 2 for spectral modeling. A multi-group full-spectrum correlated-k-distribution (FSCK) method 3 is used to reduce the number of RTE evaluations while preserving LBL accuracy. A nondimensional governing parameter to measure the significance of TRI is proposed, and the DNS fields with and without radiation coupling are used to assess TRI. Both the uncoupled and coupled results show that there is no sizable interaction between turbulence and radiation at the hypersonic environment under investigation. An explanation of why the intensity of TRI in the hypersonic boundary layer is smaller than that in many combustion flows is provided. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc

Study Of Turbulence-radiation Interaction In Hypersonic Turbulent Boundary Layers

Direct numerical simulations are conducted to investigate the effect of turbulence-radiation interaction in hypersonic turbulent boundary layers, representative of the Orion crew exploration vehicle at the peak heating condition during reentry. Both the effects of emission and absorption are considered by solving the radiative transfer equation using the tangent slab approximation and a spectral model with line-by-line accuracy. Nondimensional governing parameters to measure the significance of turbulence-radiation interaction are proposed, and the direct numerical simulation fields with and without radiation coupling are used to assess turbulence-radiation interaction. Is it found that the fluid medium within the boundary layer is optically thick with local emission largely counterbalanced by the absorbed irradiation, which results in much weaker overall radiative source termr- qR, and the thermal radiation has minimal backward influence on the turbulence flow field. In addition, both the uncoupled and coupled results show that there is no sizable interaction between turbulence and radiation at the hypersonic environment under investigation. An explanation for small turbulence-radiation interaction intensity is also provided. Copyright © 2011 by the authors

Study Of Emission Turbulence-radiation Interaction In Hypersonic Boundary Layers

Direct numerical simulations are conducted to study the effects of emission turbulence-radiation interaction in hypersonic turbulent boundary layers, representative of the Orion Crew Exploration Vehicle at peak-heating condition during reentry. A nondimensional governing parameter to measure the significance of emission turbulence-radiation interaction is proposed, and the direct numerical simulation fields with and without emission coupling are used to assess emission turbulence-radiation interaction. Both the uncoupled and coupled results show that there is no sizable interaction between turbulence and emission at the hypersonic environment under investigation. An explanation of why the intensity of emission turbulence-radiation interaction in the hypersonic boundary layer is smaller than that in many combustion flows is provided. Copyright © 2010

Deterministic Partial Differential Equation Model for Dose Calculation in Electron Radiotherapy

Treatment with high energy ionizing radiation is one of the main methods in modern cancer therapy that is in clinical use. During the last decades, two main approaches to dose calculation were used, Monte Carlo simulations and semi-empirical models based on Fermi-Eyges theory. A third way to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. Starting from these, we derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free-streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on [BerCharDub], that exactly preserves key properties of the analytical solution on the discrete level. Several numerical results for test cases from the medical physics literature are presented.Comment: 20 pages, 7 figure