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Operational performance of solar cell at low temperatures and under low illumination intensity
The results are presented of a study to determine the effect of in-situ proton irradiation upon low temperature, low intensity performance of several cell types. The cell types were selected in an attempt to distinguish variations in temperature-dependent radiation resistance which could be attributed to the n-p or p-n structure, diffused or implanted junctions, crucible grown or float-zone type base material, and high or low base resistivity. The results indicate that while expected variations of performance occur at room temperature, all cell types degrade more or less similarly at lower temperatures with normalized degradation becoming increasingly rapid as temperature is reduced. Recommendations for an optimized cell for Jupiter probe use are included along with a definition of the testing required on these cells to insure good performance characteristics.
Rotating and positive displacement pumps of various types were studied for pumping liquid fluorine for low thrust high performance rocket engines. Included in the analysis were: centrifugal, pitot, Barske, Tesla, drag, gear, vane, axial piston, radial piston, diaphragm and helirotor pump concepts. The centrifugal and gear pumps were carried through detail design and fabrication. After preliminary testing in Freon 12, the centrifugal pump was selected for further testing and development. It was tested in Freon 12 to obtain the hydrodynamic performance. Tests were also conducted in liquid fluorine to demonstrate chemical compatibility.
The present invention provides materials, devices, and methods involving new heterocyclic, shape-persistent monomeric units with internal free volume. In some cases, materials the present invention may comprise monomers, oligomers, or polymers that incorporate a heterocyclic, shape-persistent iptycene. The present invention may provide materials having low dielectric constants and improved stability at high operating temperatures due to the electron-poor character of materials. In addition, compositions of the invention may be easily synthesized and readily modified to suit a particular application.
Rotating and positive displacement pumps of various types were studied for pumping liquid fluorine for low-thrust, high-performance rocket engines. Included in the analysis were: centrifugal, pitot, Barske, Tesla, drag, gear, vane, axial piston, radial piston, diaphragm, and helirotor pump concepts. The centrifugal pump and the gear pump were selected and these were carried through detailed design and fabrication. Mechanical difficulties were encountered with the gear pump during the preliminary tests in Freon-12. Further testing and development was therefore limited to the centrifugal pump. Tests on the centrifugal pump were conducted in Freon-12 to determine the hydrodynamic performance and in liquid fluorine to demonstrate chemical compatibility.
This work examines the diffusional growth of discrete phase particles dispersed within a matrix. Engineering materials are microstructurally heterogeneous, and the details of the microstructure determine how well that material performs in a given application. Critical to the development of designing multiphase microstructures with long-term stability is the process of Ostwald ripening. Ripening, or phase coarsening, is a diffusion-limited process which arises in polydisperse multiphase materials. Growth and dissolution occur because fluxes of solute, driven by chemical potential gradients at the interfaces of the dispersed phase material, depend on particle size. The kinetics of these processes are "competitive," dictating that larger particles grow at the expense of smaller ones, overall leading to an increase of the average particle size. The classical treatment of phase coarsening was done by Todes, Lifshitz, and Slyozov, (TLS) in the limit of zero volume fraction, V(sub v), of the dispersed phase. Since the publication of TLS theory there have been numerous investigations, many of which sought to describe the kinetic scaling behavior over a 0 range of volume fractions. Some studies in the literature report that the relative increase in coarsening rate at low (but not zero) volume fractions compared to that predicted by TLS is proportional to v(sub v)(exp 1/2), whereas others suggcest V(sub v)(exp 1/3). This issue has been resolved recently by simulation studies at low volume fractions in three dimensions by members of the Rensselaer/MSFC team. Our studies of ripening behavior using large-scale numerical simulations suggest that although there are different circumstances which can lead to either scaling law, the most important length scale at low volume fractions is the diffusional analog of the Debye screening length. The numerical simulations we employed exploit the use of a recently developed "snapshot" technique, and identifies the nature of the coarsening dynamics at various volume fractions. Preliminary results of numerical and experimental investigations, focused on the growth of finite particle clusters, provide important insight into the nature of the transition between the two scaling regimes. The companion microgravity experiment centers on the growth within finite particle clusters, and follows the temporal dynamics driving microstructural evolution, using holography.
The methodology and rationale used in the development of costs for engineering, manufacturing, testing and operating a low thrust system for placing automated shuttle payloads into earth orbits are described. Cost related information for the recommended propulsion approach is included.
The costs and benefits of existing/planned systems, new propulsion concepts, and adaptations of existing/planned systems (as supported by Orbiter interface requirements and operations requirements) were quantified. Scenarios of these propulsion approaches were established which accommodate the low energy regime as defined by the new low energy payload mission model. These scenarios were screened on a cost and then a benefits basis. A propulsion approach comprising existing/planned systems and a new propulsion concept were selected as the most cost effective approach to accommodate the model payloads and the low energy regime they represent. Key cost drivers and sensitivity trends were identified. All costs were derived in 1977 dollars.
This document is the final report of NRA contract NNC16CA39C that was conducted over the period September 2016 through November2019.This study leveraged hardware developed under NRAN+3 Combustor Technology Contract (NNC14CA30C)which developed, designed and tested a N+3, low-emissions, high-OPR compact combustor for a single-aisle advanced concept aircraft
Cost effective approaches for placing automated payloads into circular and elliptical orbits using energy requirements significantly lower than that provided by the smallest, currently planned shuttle upper stage, SSUS-D, were investigated. Launch costs were derived using both NASA existing/planned launch approaches as well as new propulsion concepts meeting low-energy regime requirements. Candidate new propulsion approaches considered were solid (tandem, cluster, and controlled), solid/liquid combinations and all-liquid stages. Results show that the most economical way to deliver the 129 low energy payloads is basically with a new modular, short liquid bipropellant stage system for the large majority of the payloads. For the remainder of the payloads, use the shuttle with integral OMS and the Scout form for a few specialized payloads until the Shuttle becomes operational.
An investigation was conducted in the NASA/LaRC Low-Turbulence Pressure Tunnel on a 0.03614-scale orbiter model of a 089B configuration with a 139B configuration nose forward of F.S. 500. The tailcone was the TC sub 4 design and was instrumented with eighty-nine pressure orifices. Control surfaces were deflected and three wind tunnel mounting techniques were investigated over an angle-of-attack range from -2 deg to a maximum of 18 deg. In order to determine the sensitivity of the tailcone to changes in Reynolds number, most of the test was made at a Mach number of 0.20 over a Reynolds number range of 2.0 to 10 million per foot. A few runs were made at a Mach number of 0.30 at Reynolds numbers of 4.0, 6.0, and 8 million per foot.
Low noise amplifier design with field effect transistors, random noise characteristics, and noise measurements on commercial devices
Parametric evaluation of hydraulic, pneumatic, and electromechanical actuators for manned spacecraft tasks
Hydraulic actuation systems analysis and design, and simulated space temperature and pressure environmental testing
The development of low-profile flat conductor cable (FCC) connecting device and FCC permanent splice methods are discussed. The design goal for the low-profile connecting device was to mate and unmate FCC harness to a typical spacecraft component with a maximum height of 3/8 in. The results indicate that the design, fabrication, and processing of the low-profile connecting device are feasible and practical. Some redesign will be required to achieve the goal of 3/8 in. Also, failures were experienced subsequent to salt spray and humidity exposure. Five different FCC permanent splice methods were considered. Subsequent to evaluation of these five methods, two design concepts were chosen for development tests.
Orbital maintenance concepts were examined in an effort to determine a cost effective orbital maintenance system compatible with the space transportation system. An on-orbit servicer maintenance system is recommended as the most cost effective system. A pivoting arm on-orbit servicer was selected and a preliminary design was prepared. It is indicated that orbital maintenance does not have any significant impact on the space transportation system.
A payload mission model covering 129 launches, was examined and compared against the space transportation system shuttle standard orbit inclinations and a shuttle launch site implementation schedule. Based on this examination and comparison, a set of six reference missions were defined in terms of spacecraft weight and velocity requirements to deliver the payload from a 296 km circular Shuttle standard orbit to the spacecraft's planned orbit. Payload characteristics and requirements representative of the model payloads included in the regime bounded by each of the six reference missions were determined. A set of launch cost envelopes were developed and defined based on the characteristics of existing/planned Shuttle upper stages and expendable launch systems in terms of launch cost and velocity delivered. These six reference missions were used to define the requirements for the candidate propulsion modes which were developed and screened to determine the propulsion approaches for conceptual design.
Silicon epitaxy analysis of silane produced in the Process Development Unit operating in a completely integrated mode consuming only hydrogen and metallurgical silicon resulted in film resistivities of up to 120 ohms cm N type. Preliminary kinetic studies of dichlorosilane disproportionation in the liquid phase have shown that 11.59% SiH4 is formed at equilibrium after 12 minutes contact time at 56 C. The fluid-bed reactor was operated continuously for 48 hours with a mixture of one percent silane in helium as the fluidizing gas. A high silane pyrolysis efficiency was obtained without the generation of excessive fines. Gas flow conditions near the base of the reactor were unfavorable for maintaining a bubbling bed with good heat transfer characteristics. Consequently, a porous agglomerate formed in the lower portion of the reactor. Dense coherent plating was obtained on the silicon seed particles which had remained fluidizied throughout the experiment.