Radiant-interchange configuration factors for spherical and conical surfaces to spheres
Computer program for determining geometric configuration view factors for spherical and conical surfaces of spherical radiating bodies
Campbell, J. P.↗
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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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SSM atomic oxygen reactions on Kapton and silverized Teflon
Surface morphology studies using scanning electron microscopy on Kapton and Inconel silver coated Teflon material samples retrieved from the Solar Maximum Mission spacecraft revealed significant changes attributed to orbital atomic oxygen induced reactions. The Kapton recession observed on the aluminized Kapton material samples appeared equivalent in nature with that observed on previous Space Shuttle LEO missions. SSM Teflon taped material samples, coated on the back side with films of Inconel protected silver were observed degraded on both sides. Visibly severe reactions on the back side produced total blackening, generally restricted to areas of tape with a narrow direct view-factor of the external orbital environment. High magnification scanning electron microscope views provided evidence of near total silver reaction, flaking, and subsequent erosion of the underlying Teflon itself. Only three of the extensive S.E.M. photographs illustrating the basic reactions observed are included pending further detailed investigations.
Roger Linton↗
Urban Climate Station Site Selection Through Combined Digital Surface Model and Sun Angle Calculations
Meteorological measurements within urban areas are becoming increasingly important due to the accentuating effects of climate change upon the Urban Heat Island (UHI). However, ensuring that such measurements are representative of the local area is often difficult due to the diversity of the urban environment. The evaluation of sites is important for both new sites and for the relocation of established sites to ensure that long term changes in the meteorological and climatological conditions continue to be faithfully recorded. Site selection is traditionally carried out in the field using both local knowledge and visual inspection. This paper exploits and assesses the use of lidar-derived digital surface models (DSMs) to quantitatively aid the site selection process. This is acheived by combining the DSM with a solar model, first to generate spatial maps of sky view factors and sun-hour potential and second, to generate site-specific views of the horizon. The results show that such a technique is a useful first-step approach to identify key sites that may be further evaluated for the location of meteorological stations within urban areas.
digital surface model↗
Radiative configuration factors from cylinders to coaxial axisymmetric bodies
Exact solutions are obtained for the radiative configuration factor between differential elements of arbitrary orientation and cylinders. A general method is then proposed for calculating the view factor from a cylinder to a coaxial axisymmetric body using only a single numerical integration. The method is illustrated for axisymmetric bodies with function generators described by a power law equation. The method may be useful in calculating radiative heat transfer between cylindrical bodies and high-density exhaust gases and between annular radiative fins and their bases.
Saltiel, C.↗
Space Transfer Concepts and Analyses for Exploration Missions. Technical Directive 12: Beamed Power Systems Study
Parametric models were constructed for Earth-based laser powered electric orbit transfer from low Earth orbit to geosynchronous orbit. These models were used to carry out performance, cost/benefit, and sensitivity analyses of laser-powered transfer systems including end-to-end life cycle cost analyses for complete systems. Comparisons with conventional orbit transfer systems were made indicating large potential cost savings for laser-powered transfer. Approximate optimization was done to determine best parameter values for the systems. Orbit transfer flights simulations were conducted to explore effects of parameters not practical to model with a spreadsheet. The simulations considered view factors that determine when power can be transferred from ground stations to an orbit transfer vehicle and conducted sensitivity analyses for numbers of ground stations, Isp including dual-Isp transfers, and plane change profiles. Optimal steering laws were used for simultaneous altitude and plane change. Viewing geometry and low-thrust orbit raising were simultaneously simulated. A very preliminary investigation of relay mirrors was made.
Eder, D.↗
Specular and direct radiative loads on space structure
The use of special models for trusses, and of fast graphical computational techniques, are discussed to reduce the computation times of intersurface radiation loads and specularly reflected radiation. The conditions under which the One-Dimensional approximation can be used, and the computation of the obstructed view factors for arbitrary surfaces, including the One-Dimensional surface, are considered using both contour and double area integration. The Adaptive Ray Tracing method is found to be very fast for surface configurations and obstruction densities typical of space structures, and it is shown to be best suited to views of J from I which are relatively simple and cover only a few subareas of S.
Emery, A. F.↗
Measuring the Stress Factors for Photovoltaic (PV) Backsheet Degradation
Back sheet failure has resulted in power loss and large-scale recall of photovoltaic modules, resulting in billions of dollars in lost revenue. The light exposure on the backside of a photovoltaic module comes primarily from reflected light which alters the distribution of natural sunlight. Because of this, modelling the backside exposure and duplicating the exposure is much more difficult than modeling the frontside exposure. This project aims to study how various back sheets and junction box materials degrade under different conditions and to develop Python code to help model and predict degradation. The stress factors for back-sheet degradation must be quantified to extrapolate accelerated stress tests to the field. Test samples were placed in the A3, A4, and A5 conditions, as defined in IEC 62788-7-2, to assess the temperature and humidity dependence of ultraviolet (UV) induced degradation. We are utilizing a custom chamber with exposure from 0.5 UV-suns to 5 UV-suns to understand the dependence of degradation on light intensity. A group of samples put in the A3 condition had glass filters with 50% UV cut-offs of 320 nm, 335 nm, and 360 nm to assess the wavelength dependence of UV degradation. All this data is necessary to assess the impact of non-standard UV light exposure. The material evaluation tests include gloss measurements, attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR), UV-visible reflectance/transmittance utilizing a Cary Ci7000 spectrophotometer, and a nano-indenter for surface hardness and modulus measurements. Alongside the experimental work, there is a computational effort using raytracing and Python open-source tools in PVDeg , PVLib, and Bifacial_Radiance. This code will create specific exposure scenarios and enable the evaluation of chamber degradation relative to field degradation. Equation 1 is a strawman equation used to model degradation on the backside of a PV module. We will create simplified code, based on the results of ray-tracing calculations, which uses a view factor approach to provide fast calculations for the most common exposure scenarios.
14 SOLAR ENERGY↗
Surface Heat Load Analysis Due to Plasma Thermal Radiation on Equatorial Port 09
This paper reports calculated surface heat load owing to plasma thermal radiation, which will be applied to the surfaces of Equatorial Port 09 (EP09) diagnostic shield modules (DSMs) for thermal analysis during normal operation. The calculation assumes that the thermal energy will deposit uniformly in all directions from the plasma to the adjacent components and environment (i.e. gray body radiation). Assuming the temperature for the plasma surface, calculated view factors are used to determine the allocation of thermal energy to each component. The analysis provides an initial assessment of the thermal radiation heat load on the DSMs to be checked in structural/thermal analyses to verify significance. In conclusion, the designs of the EP09 components are still in the early preliminary phase, and changes are expected in the future.
ANSYS↗
Tensorized Interior Radiative Heat Transfer for a Scalable and Calibrated Building Energy Simulator
Building energy simulation is a critical tool for developing and testing advanced control strategies, such as Reinforcement Learning (RL), to provide demand flexibility and affordable energy costs. The recently introduced Smart Buildings Control Suite (sbsim) provides a lightweight, scalable, and data-calibrated simulation environment based on a 2D finite-difference model. However, the initial model primarily focused on conductive and convective heat transfer, neglecting the significant impact of long-wave radiative heat exchange between interior surfaces. This paper presents a significant extension to the sbsim framework by incorporating a physically-grounded model for interior radiative heat transfer. Our primary contribution is the development and integration of a fully tensorized radiative heat transfer module, which preserves the computational efficiency and scalability of the original simulator. This was achieved by developing a pipeline for view factor calculation, including an algorithm to identify directly seeing surfaces within complex floor plans, and formulating the net radiation equations for efficient execution on modern hardware accelerators. We validate the numerical accuracy of our tensorized implementation by comparing its results against a traditional iterative approach, demonstrating identical outcomes. This enhancement increases the physical fidelity of sbsim, enabling more accurate training of RL agents for building energy optimization.
Ham, Sang woo↗
Thermal and Criticality Analysis of the Plasma Core Reactor
Radiative heat transfer to the propellant and reactor criticality for a fissionable gaseous rocket engine are analyzed to determine their interdependence. The necessity for propellant thicknesses of approximately 1-3 m due to poor thermal absorption properties of hydrogen significantly affects reactor critical radius and mass. The two primary adverse effects are: (1) increased absorption in the reflector- moderator for a given reflector thickness and (2) poor utilization of thermal neutrons by the core due to the lower geometrical view factor of the core for the reflector walls. In fact, there is a minimum core radius at a particular propellant thickness which allows the system to “go” critical. Engine performance is limited primarily to two regions of operation: the first, a specific impulse of approximately 1550 sec at a thrust level of 2 x 10(exp 6) lb. and second, a specific impulse of approximately 2200 sec at a thrust level of 5.3 x 10(exp 6) lb.
Rocket engine↗
Three-dimension heat transfer program
An IBM 7094, three dimensional, heat transfer program for satellite application is discussed. The program may be applied to all phases of spacecraft life, from launch to orbital quasi-steady state. Launch phase heating includes inputs by radiation from the hot fairing and free molecule flow heating after nose cone ejection. Orbital heat fluxes are accounted for by direct sunlight, earth-reflected sunlight, and earth-emitted input to the satellite. Internal heat exchange by conduction and radiation is determined, provided the appropriate conductances, radiation view factors, and effective emittances are known. A simplified analysis of an active thermal controlled spacecraft is incorporated into the program. One or more surfaces may contain shutter systems which have optical properties specified as a function of shutter opening. The program evaluates the feasibility of any configuration based upon maintaining an internal component within its tolerable temperature limits. The program employs a matrix inversion subroutine (Gauss Elimination Method) to solve the heat balance equations.
COMPUTER PROGRAM↗
Launch window definition for sky target experiments.
This paper is a brief report on the computer program developed for the Extraterrestrial Physics Barium Ion Cloud (BIC) Project. The mathematical analysis developed for the program along with its programing characteristics are pointed out to show that this program is adaptable to similar sky target projects. Definite viewing constraints are specified so that the chosen ground tracking stations can photograph the behavior of the sky target after its release. Viewing factors include the illumination of the target by the sun, the relative elevation look angle to the target from each tracking station, the solar and lunar depression angles at each tracking station, and the total sky background brightness of the target relative to each tracking station. Numeric values are assigned to each factor through program input. The program output is flexible so that the results of the window calculations can be studied to the depth required.
Michaud, N. H.↗
A laser technique for characterizing the geometry of plant canopies
The interception of solar power by the canopy is investigated as a function of solar zenith angle (time), component of the canopy, and depth into the canopy. The projected foliage area, cumulative leaf area, and view factors within the canopy are examined as a function of the same parameters. Two systems are proposed that are capable of describing the geometrical aspects of a vegetative canopy and of operation in an automatic mode. Either system would provide sufficient data to yield a numerical map of the foliage area in the canopy. Both systems would involve the collection of large data sets in a short time period using minimal manpower.
Vanderbilt, V. C.↗
Significance of vegetation in interpreting thermal radiation from a terrestrial surface
The regions between crop rows are modeled as infinitely long diffuse cavities. Geometrical view factors are calculated, accounting for reflected radiation emanating internal to the cavity and from the background sky. A 'cavity' emissivity dependent on local geometry is defined to allow for correcting apparent temperatures to true temperatures. The total emissivity appropriate for correcting aircraft thermal data is then calculated by averaging all emissivity components to account for soil, crop, and background. It is shown that even for the lowest crop and vegetation emissivities, if the crop height-to-spacing ratio is greater than unity, the composite emissivity is greatly increased, giving rise to a decreased error in remotely sensed temperature data.
Sutherland, R. A.↗
Temperature control analysis and flight results for the Viking Orbiter 1975 Mars atmospheric water detection instrument
The Mars atmospheric water detector (MAWD) instrument required a temperature of -70 C at the detector. The monochromator housing required +20 C + or - 1 C. This instrument was located on the scan platform, and slewed across two solar panels. The thermal design for the detector was an open flat plate radiator thermally isolated on four 1-in. tubes, with a flexible strap to the detector. MAWD radiator view factors and heat loads from the spacecraft were determined for the Lander on and off, for all angular positions of the scan platform. Subsystem and system tests were performed using the 25-ft diameter solar simulator. In-flight results have shown no anomalies, and no degradation has been observed. Servo-controlled heaters are used to control the temperature.
Kavanagh, H. M.↗
Assessment of shuttle payloads gaseous environment contamination and its control
A prediction is given of the in-orbit gaseous environment and the contamination it could produce on cryogenic and room temperature surfaces of payloads in the shuttle bay. The time varying environment was obtained by the superposition of the calculated shuttle environment for a discrete time and payload induced environments measured in large space chambers. Representative contaminant surface accretions were calculated for flights 1 week and 1 month long for payloads having the largest source of outgassing and an orbit of 200 km. A number of calculations were based on the magnitude of the sources, the molecular natures, the decay rate with time, the sticking coefficients, the view factors, and the temperatures of the surfaces being contaminated. Significant results are reported.
Scialdone, J. J.↗
Space shuttle main engine plume radiation model
The methods are described which are used in predicting the thermal radiation received by space shuttles, from the plumes of the main engines. Radiation to representative surface locations were predicted using the NASA gaseous plume radiation GASRAD program. The plume model is used with the radiative view factor (RAVFAC) program to predict sea level radiation at specified body points. The GASRAD program is described along with the predictions. The RAVFAC model is also discussed.
Reardon, J. E.↗
Improved materials characterization for spacecraft applications
A material outgassing test consists of an effusion cell, mass spectrometer, and thermally controlled quartz crystal microbalance (TQCM). The material sample is placed in the effusion cell at a predetermined temperature, and the sample is outgassed in a vacuum of 0.000001 torr range. The total outgassing mass as a function of time is determined with the TQCM which is cooled to LN2 temperatures. Based on the view factor of the TQCM, the total outgassed mass can be determined. The technique can be verified by comparing the results to the actual mass loss of the sample which is determined by hanging the diffusion cell from the Cohn microbalance. The mass spectrometer can be used to determine if there are any low molecular weight components outgassing, such a nitrogen which does not condense on the TQCM. After the material outgasses to a point of saturation, the effusion cell is closed off, and the TQCM is slowly heated to allow the condensed film to be broken down into its components. As the temperature is increased, the components evaporate from the surface at a different rate and can be detected with the mass spectrometer. The relative amount of each component is found by the change in frequency of the TQCM as the component evaporates. Hence, from this test, not only is isothermal kinetic data obtained, but the primary components can also be identified in terms of their molecular weight.
Cull, R.↗