Advanced space transportation technologies

A wide range of propulsion technologies for space transportation are discussed in the literature. It is clear from the literature review that a single propulsion technology cannot satisfy the many mission needs in space. Many of the technologies tested, proposed, or in experimental stages relate to: chemical and nuclear fuel; radiative and corpuscular external energy source; tethers; cannons; and electromagnetic acceleration. The scope and limitation of these technologies is well tabulated in the literature. Prior experience has shown that an extensive amount of fuel needs to be carried along for the return mission. This requirement puts additional constraints on the lift off rocket technology and limits the payload capacity. Consider the possibility of refueling in space. If the return fuel supply is guaranteed, it will not only be possible to lift off more payload but also to provide security and safety of the mission. Exploration to deep space where solar sails and thermal effects fade would also be possible. Refueling would also facilitate travel on the planet of exploration. This aspect of space transportation prompts the present investigation. The particle emissions from the Sun's corona will be collected under three different conditions: in space closer to the Sun, in the Van Allen Belts; and on the Moon. It is proposed to convert the particle state into gaseous, liquid, or solid state and store it for refueling space vehicles. These facilities may be called space pump stations and the fuel collected as space fuel. Preliminary estimates of fuel collection at all three sites will be made. Future work will continue towards advancing the art of collection rate and design schemes for pumping stations

Current rate flash of carbon fibers

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Touch Free Sintering with Superposition of Magnetic Fields

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Confluence of Flash and UHS

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Memristors: The Role of Anode Interface Resistance

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Dual function polymer-derived non-oxide/oxide matrix prepared by additive manufacturing

A nanolayer-at-a-time additive manufacturing approach is employed to create a dense matrix of polymer-derived ceramics around fiber bundles of silicon carbide. Thin ultrathin films pyrolyze quickly without cracks with a cycle time of about one minute. The polymer precursor for SiCN is mixed with a precursor of hafnium oxide, which produces a matrix containing a fine dispersion of hafnium silicate. The oxide/nonoxide matrix leads to both good mechanical properties as well as remarkable oxidation resistance

Reaction flash sintering of multiphase ceramics

A new phenomenon where the application of modest electric fields can lower the sintering temperature well below 1000 oC, and the time to just a few seconds, is being called flash sintering. For example yttria stabilized zirconia which normally requires several hours at 1400 oC can be sintered in mere seconds at 800 oC with fields of about 100 V cm–1. The method has been applied to various classes of ceramics drawing from semiconductors, electronic or ionic conductors, and insulators. Flash sintering is further accompanied by intense electroluminescence and a non-linear increase in electrical conductivity. A mechanism that can explain the simultaneous rise in chemical diffusion and a change in the electronic structure remains elusive, though the generation of vacancies, interstitials, electrons and holes via Frenkel pairs appears to apply. Non-linear lattice vibrations also appear to be at play. In-situ experiments carried out at APS and NSLA-II synchrotrons at Argonne and Brookhaven National Laboratories is revealing new effects of flash related to unusual “far from equilibrium” phase transformations. Most recent work, which will be highlighted during this talk, is related to reaction flash sintering, where constituent oxides simultaneously react and sinter in mere seconds to form single phases of complex oxides, usually for functional applications. This unique feature of flash enables the synthesis of dense compounds of ceramics which are usually not accessible by conventional sintering because of low-melting and volatile constituents as well as the presence of intermediate phases. Among the examples is sintering of pure phase bismuth ferrite from bismuth oxide and iron oxide in mere seconds with flash. Other such examples, including the sintering of multiphase composites, will be described. Supported by ONR and AR

Flash Migration Velocity in Bilayers: With an Without Interdiffusion

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Lattice softening

In-situ measurements of the elastic modulus with 8YSZ in the state of flash reveal a large softening in the presence of the electric field. This discovery may explain the lowering of the energy barrier for the formation of Frenkel defects. The results also support the consequences from recent molecular dynamics calculations (Jongmann and Wolf) that reveal that Frenkels can form by the injection of phonons at a high rate, while holding the specimen above the Debye Temperature. These points will be raised for discussion

DEVELOPMENT OF A BOILING REGIME MAP AND GRAVITY SCALING PARAMETER FOR POOL BOILING HEAT TRANSFER

Virtually all data to date regarding parametric effects of gravity on pool boiling have been inferred from experiments performed in low-g, 1g, and 1.8g conditions. The current work is based on observations of boiling heat transfer obtained over a continuous range of gravity levels (0g-1.8g) and varying heater sizes under subcooled liquid (FC-72/n-perfluorohexane) conditions. Variable gravity pool boiling heat transfer measurements were made during the parabolic flight campaigns organized by the European Space Agency (ESA) and NASA. Heater size was varied by using two (2.7x2.7 mm2 and 7.0x7.0 mm2) constant temperature microheater arrays consisting of 96 platinum resistance heaters deposited in a 10x10 configuration onto a quartz substrate. The ability to selectively power a subset of heater elements (1, 4, 9, 16, 25, 36, 64, and 96) in a square pattern out of the 10x10 configuration allowed a variation in heating area from 0.27x0.27 mm2 to 7.0x7.0 mm2. A parametric study on the effects of fluid properties, wall superheat, liquid subcooling, and dissolved gas concentration on boiling heat transfer was also performed. Based on the heater sizes and the gravity levels investigated, two pool boiling regimes were identified. For large heaters and/or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. Under low gravity conditions and/or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A first ever pool boiling regime map differentiating buoyancy and surface tension dominated boiling regimes was developed. The non-dimensional ratio of heater size Lh and capillary length Lc was found suitable to differentiate between the boiling regimes. Transition between the regimes was observed to occur at a threshold value of Lh/Lc ~2.1. Pool boiling data in the buoyancy dominated boiling regime (Lh/Lc>2.1) was used to develop a gravity scaling parameter for pool boiling heat transfer. A non-dimensional temperature was defined in order to derive a gravity scaling parameter independent of dissolved gas concentrations and liquid subcooling. The power law coefficient for the gravity effect was observed to be a function of the non-dimensional wall temperature. The predicted results were found to be in good agreement with the heat transfer data over a wide range of gravity levels (0g-1.8g), dissolved gas concentrations, subcoolings, and heater surface morphologies. Use of this scaling parameter to obtain heat transfer at varying gravity levels is expected to save considerable experimental resources required to validate the performance of phase change based systems under different gravity conditions