Simulated Rocket Research Articles

Simulation of anticoagulation in atrial fibrillation patients with rivaroxaban-from trial to target population.

The populations included in the randomized controlled clinical trials and observational studies were different. The effectiveness and safety of rivaroxaban for stroke prevention in patients with atrial fibrillation (AF) varied among studies. This study aimed to estimate the real-world outcomes of rivaroxaban in patients with AF accurately. A discrete event simulation (DES) was used to predict the counterfactual results of the ROCKET AF study. The hypothetical cohorts of patients were generated using Monte Carlo simulation according to the baseline covariate distributions that matched the marginal distribution of covariates reported in the ROCKET AF and three observational studies. The DES model structure was constructed based on a priori knowledge about disease progression and possible outcomes of patients with AF. The DES model accurately replicated the overall results of the ROCKET AF study. Both predicted stroke/systematic embolism (SE) and major bleeding rates were lower in the three observational studies than in the simulated ROCKET AF study. The risk difference of stroke/SE and major bleeding was not significant among the predicted outcomes of the three observational studies. Although some differences existed in the absolute rates of stroke/SE and major bleeding between observed and simulated studies, the results confirmed that rivaroxaban was noninferior to warfarin for the prevention of stroke/systematic embolism with no significance in the risk of major bleeding in large AF populations, which was similar to the results of ROCKET AF.

Corrosion of 310S Austenitic Stainless Steel in Simulated Rocket Combustion Gas

High temperature corrosion of 310S austenitic stainless steel in simulated rocket combustion gas at 900 degree Celsius was investigated and discussed in this paper. 310S austenitic stainless steel was chosen because it was used for building some components of a rocket launcher. The corrosive atmosphere was prepared by mixing of hydrochloric acid and distilled water with 5.5 mole per liter then, boiling that solution and feeding into a corrosion testing chamber. The chamber was set up at 900 degree Celsius with duration 210 hrs. After testing, the corroded specimen was microscopically characterized by OM and SEM/EDS techniques. The corrosion layer was classified into three main sublayers: peeling-off scale, external corrosion sublayer, and internal corrosion sublayer. The local chemical information was analyzed by XRD (in case of peeling-off scale) and SEM/EDS (in case of external and internal corrosion sublayers). The peeling off scale mainly comprised Fe2O3 and Fe21.3O32 ferrous oxides because they needed much oxygen consumption to exist. In case of external and internal sublayers, there were a lot of pore tunnels and corrosion products. Chlorine and/or hydrogen chloride would penetrate through a passive film and, then, metal chlorides was formed on both external and internal corrosion sublayers. Metal chlorides would volatile because of their lower evaporation temperature than the testing temperature. Moreover, they were oxidized by oxygen in wet condition and resulted metal oxides mostly remaining on the external corrosion sublayer.

CFD Modelling of a Quadrupole Vortex Inside a Cylindrical Channel for Research into Advanced Hybrid Rocket Designs

This study relies on computational fluid dynamics (CFD) tools to analyse a possible method for creating a stable quadrupole vortex within a simulated, circular-port, cylindrical rocket chamber. A model of the vortex generator is created in a SolidWorks CAD program and then the grid is generated using the Pointwise mesh generation software. The non-reactive flowfield is simulated using an open source computational program, Stanford University Unstructured (SU2). Subsequent analysis and visualization are performed using ParaView. The vortex generation approach that we employ consists of four tangentially injected monopole vortex generators that are arranged symmetrically with respect to the center of the chamber in such a way to produce a quadrupole vortex with a common downwash. The present investigation focuses on characterizing the flow dynamics so that future investigations can be undertaken with increasing levels of complexity. Our CFD simulations help to elucidate the onset of vortex filaments within the monopole tubes, and the evolution of quadrupole vortices downstream of the injection faceplate. Our results indicate that the quadrupole vortices produced using the present injection pattern can become quickly unstable to the extent of dissipating soon after being introduced into simulated rocket chamber. We conclude that a change in the geometrical configuration will be necessary to produce more stable quadrupoles.

An Improved Initial Alignment Method for Rocket Navigation Systems

This paper proposes an algorithm for the initial alignment method for rocket navigation systems. It uses the inertial freezing alignment to resolve the attitude matrix with respect to its fast and robust characteristics. Due to disturbances from the swaying base environment, such as people walking and wind effect, which would consequently result in a great lever arm effect, a Finite Impulse Response (FIR) filter is utilized to decrease the noise in the accelerometers' measurement. In addition, there are sensor errors in the system; the online estimation of gyroscopes' drift with a Kalman filter is adopted to achieve compensation. Numerical results from a simulated rocket initial alignment experiment are reported to demonstrate the effectiveness of the method.

Effect of Aluminum on Heat Flux from a Simulated Rocket Propellant Flame

Aluminum particles have been shown to enhance the performance in propellant systems by reacting and releasing significant chemical energy that contributes to the overall heat release. However, the heat transfer characteristics from a propellant to a target are not well understood. In this study, impinging flow geometries of a simulated propellant flame seeded with aluminum particles were investigated. Although the contribution of aluminum was the main focus of this study, inert powders of alumina-titania and yttria stabilized zirconia were also used to compare and quantify the heat flux contributions of reacting, melting, and nonmelting powders, respectively. An oxygen-acetylene torch seeded with aluminum, alumina-titania, or yttria stabilized zirconia was used to analyze the different heat transfer characteristics from each material. Copper coupons captured and quenched reacting particulates from the flame. A scanning electron microscope with energy dispersive spectroscopy and a differential scanning calorimeter were used to examine the degree of completion of aluminum oxidation. Results show that yttria stabilized zirconia experience a 1.9% increase in heat flux compared with gas-only flames. Flames seeded with alumina-titania showed an 80.2% increase in heat flux, whereas aluminum particles provide a 232.7% gain over gas-only flames. Results from the differential scanning calorimeter show that aluminum consumption percentages for flames with a 2.5 oxygen-fuel ratio are an average of 8.6% higher than those for a 1.5% oxygen-fuel ratio. The percent of aluminum consumed in the reaction generally increases with standoff distance.

Forward masking in young children: Rocketship psychophysics

A three-alternative forced choice forward masking procedure was embedded in an arcade-style rocketship video game. Human subjects were categorized into five groups; adults and 5-, 6-, 7-, and 8-year-old children. The masker was a 500-msec noise that simulated rocket engines and the 20-msec, 500-Hz sinusoidal signal was achirp from agremlin. The gremlin hid, at random, in one of the three rockets. Subjects responded and interacted with the game by touching the rocket hiding the gremlin. Results revealed that masked thresholds decreased for all groups as a function of the interstimulus interval. The reliability of the psychophysical approach was confirmed and a developmental trend lends support to the hypothesis that auditory processing improves as a function of age. Children’s auditory filters were suggested to be functionally larger than those of adults.

Inversion techniques for recovering two-dimensional distributions of auroral emission rates from tomographic rocket photometer measurements

In this paper we demonstrate how the spatial distribution of optical emission rates within an auroral arc may be recovered from rocket photometer measurements made in a tomographic spin scan mode. We describe the tomographic inversion procedures required to recover this information and the implementation of two inversion algorithms that are particularly well suited for dealing with the problem of noise in the observational data. These algorithms are based upon the algebraic reconstruction technique and utilize "least-squares" and "maximum-probability" iterative relaxation methods. The performance of the inversion algorithms and the limitations of the rocket tomography technique are assessed using various sets of simulated rocket measurements that were generated from "known" auroral emission-rate distributions. The simulations are used to investigate how the quality of the tomographic recovery may be influenced by various factors such as noise in the data, rocket penetration of the auroral form, background sources of emission, smearing due to the photometer field of view, and temporal variations in the auroral form.

Free-Flight Rocket's Initial Trajectory as Affected by Massive Blowby

An experimental program has been conducted to determine the unbalanced forces on a tube-launched rocket due to the choking and the subsequent reversal (or blowby) of the exhaust flow. An underexpanded jet of unheated air was exhausted into a nontipoff launch tube. The surface of the simulated rocket was instrumented with static pressure orifices, located in diametrically opposed pairs. The differential pressure measurements were used to compute the rocket's trajectory in a three-degree-of-freedom program. Relatively large asymmetric pressure differentials were measured on the surface of the simulated rocket. Although the lateral displacement of the rocket was relatively insensitive to these pressure differentials, they caused large, oscillatory variations in the pitch angle and in the pitch rate.

Measurements of a simulated rocket exhaust plume near the Prandtl-Meyer limiting angle

Abstract : Direct measurements of the mass flux level and estimates of the mass velocity have been made in the side flow field of a small axisymmetric rocket nozzle operated in hard vacuum. A shock tube provided nitrogen and simulated rocket propellant (nitrogen tetroxide and Aerozene 50) sources for the nozzle. Data were recorded in the plume far field, for angles ranging from 0 to 90 degrees relative to the nozzle centerline. In all cases, substantial mass flux levels were observed in the neighborhood of the limiting Prandtl-Meyer characteristic. At an angle of 90 degrees to the nozzle centerline, the density levels were typically three orders of magnitude below centerline values and the mass velocities were approximately one-half of the centerline values. (Modified author abstract)

Non-symmetric flow in Laval type nozzles

The equations of the steady state, compressible inviscid gaseous flow are linearized in a form suitable for application to nozzles of the Laval type. The procedure in the supersonic phase is verified by comparing solutions so obtained with those derived by the method of characteristics in two and three dimensions. Likewise, the solutions in the transonic phase are com pared with those obtained by other investigators. The linearized equation is then used to investigate the nat re of non-symmetric flow in rocket nozzles. It is found that if the flow from the combustion chamber into the nozzle is non-symmetric, the magnitude and direction of the turning couple produced by the emergent jet is dependent on the profile of the nozzle and it is possible to design profiles such that the turning couples or lateral forces are zero. The optimum nozzle so designed is independent of the pressure and also of the magnitude of the non-symmetry of the entry flow. The formulae by which they are obtained have been checked by extensive static and projection tests with simulated rocket test vehicles which are described in this paper.

Measurement of individual particle velocities in a simulated rocket exhaust

Measurement of individual particle velocities in a simulated rocket exhaust

THE OXIDATION OF ZIRCONIUM CARBIDE IN HIGH-TEMPERATURE COMBUSTION GASES

The reactions of sintered zirconium and titanium carbides have been studied in simulated rocket combustion gases at surface temperatures of about 2250° C. Under these conditions zirconium carbide is oxidized according to a parabolic law owing to the formation of an adherent oxide film. No oxide film is formed on titanium carbide under the same conditions, and it decreases in weight and dimensions at a relatively rapid rate.