Modification of the one-dimensional REKAP program to allow for charring in three material layers Final report

Modified one-dimensional reaction kinetics program to allow for charring in three material layers of rocket nozzle throat insert cas

Structures and proton-pumping strategies of mitochondrial respiratory enzymes

Enzymes of the mitochondrial respiratory chain serve as proton pumps, using the energy made available from electron transfer reactions to transport protons across the inner mitochondrial membrane and create an electrochemical gradient used for the production of ATP. The ATP synthase enzyme is reversible and can also serve as a proton pump by coupling ATP hydrolysis to proton translocation. Each of the respiratory enzymes uses a different strategy for performing proton pumping. In this work, the strategies are described and the structural bases for the action of these proteins are discussed in light of recent crystal structures of several respiratory enzymes. The mechanisms and efficiency of proton translocation are also analyzed in terms of the thermodynamics of the substrate transformations catalyzed by these enzymes

Computer simulation program is adaptable to industrial processes

The Reaction kinetics ablation program /REKAP/, developed to simulate ablation of various materials, provides mathematical formulations for computer programs which can simulate certain industrial processes. The programs are based on the use of nonsymmetrical difference equations that are employed to solve complex partial differential equation systems

Detonation Diffraction Through a Mixture Gradient

A simple one-dimensional model of a self-propagating gaseous detonation consists of a shock wave tightly coupled to a reaction zone, propagating through a combustible gas mixture as shown in Fig. 1 (Strehlow 1984). A feedback mechanism exists in that the shock wave generates the thermodynamic conditions under which the gas combusts, and the energy release from the reaction zone maintains the strength of the shock This is in contrast to a flame, or deflagrative combustion, in which thermal and species transport processes dominate. Given a particular set of initial conditions, a self-propagating detonation wave travels at a constant Chapman-Jouguet velocity (VCJ) on the order of a few thousand meters per second, with associated pressures and temperatures of tens of bar and several thousand degrees, respectively. A detonation is actually a three-dimensional shock-reaction zone complex with a dynamic wavefront composed of curved incident, mach stem, and transverse shock waves as depicted in Fig. 2 (Strehlow 1970). The transverse shocks sweep across the wavefront and the triple-point paths form a diamond-shaped cellular pattern. The cell width [Greek lambda] is a characteristic length scale of detonations, indicative of the coupling between gasdynamic and chemical processes

On-line digital computer control of the NERVA nuclear rocket engine

The problem of on-line digital computer control of the NERVA nuclear rocket engine is considered. Proposed is a method of State Dependent State Variable Feedback (SDSVF) as a practical approach to the control of NERVA and other complex nonlinear and/or time-varying systems. The difficulties inherent in other design methods are avoided by defining the optimal closed loop system in terms of a desired transfer function, rather than a performance index to maximize or minimize

Analytical comparisons of ablative nozzle materials final report, jun. 20, 1963 - nov. 20, 1964

Reaction kinetics ablation program to predict ablation performance of rocket nozzle heat protection material

Oblique impact: Projectile richochet, concomitant ejecta and momentum transfer

Experimental studies of oblique impact indicate that projectile richochet occurs for trajectory angles less than 30 deg and that the richocheted projectile, accompanied by some target material, are ejected at velocities that are a large fraction of the impact velocity. Because the probability of occurrence of oblique impact less than 30 deg on a planetary body is about one out of every four impact events, oblique impacts would seem to be a potential mechanism to provide a source of meteorites from even the largest atmosphere-free planetary bodies. Because the amount of richocheted target material cannot be determined from previous results, additional experiments in the Ames Vertical Gun laboratory were undertaken toward that purpose using pendulums; one to measure momentum of the richocheted projectile and concomitant target ejecta, and a second to measure the momentum transferred from projectile to target. These experiments are briefly discussed

Impacts of free-floating objects: Unique space station experiments

The transfer of momentum and kinetic energy between planetary bodies forms the basis for wide ranging problems in planetary science ranging from the collective long term effects of minor perturbations to the catastrophic singular effect of a major collision. Although the collisional transfer of momentum and energy was discussed over the last two decades, major issues remain that largely reflect current limitations in Earth based experimental conditions and 3-D numerical codes. Two examples with potential applications in a Space Station laboratory, are presented: asteroid spin rates and orientations, and planetary disruption/spin rates. Asteroid spin rate and orientation experiments are needed wherein free floating nonspining and spining objects of varying strength, porosity, and volatility are impacted at varying velocities and angles. A space station platform also could provide an opportunity to test important facets of planetary disruption/spin rate models by allowing freely suspended spherical targets of varying viscosities, internal density gradients, and spin rates

Experimental evidence for non-proportional growth of large craters

Evidence from laboratory impact experiments is indicating that increasing crater aspect ratios (diameter:depth) can result from increasing both velocity and projectile size without invoking unusual impactor conditions. An extensive data base of experimental impact cratering was analyzed for a variety of impactors and impact velocities for low strength targets. These data indicate a change in cratering efficiency that appears to be related to the onset of projectile deformation or rupture. When all projectile types and sizes are considered, one finds two contrasting relationships between crater aspect ratio and impactor parameter. These relationships are briefly considered

Momentum transfer from oblique impacts

A completely satisfactory experiment would be in a low gravity environment where the effect of momentum imparted by ejecta impacting the surface can be removed or controlled from momentum transfer during impact. Preliminary estimates can be made using a ballistic pendulum. Such experiments were initiated at the NASA-Ames Vertical Gun Range in order to examine momentum transfer due to impact vaporization for oblique impacts. The preliminary results indicate that momentum from oblique impacts is very inefficient: decreasing with increasing impact velocity and perhaps size; increasing with decreasing density; and increasing with increasing impact angle. At face value, such results minimize the effect of momentum transfer by grazing impact; the more probable impact angles of 30 deg would have a greater effect, contrary to the commonly held impression