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Photograph of model of SLS Block 1 vehicle and launch tower installed in the NASA LaRC 14-by 22-Foot Subsonic Wind Tunnel.
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... other table contains increments of the effects due to the presence of the launch tower as the height of the vehicle from the launch pad increases immediately after liftoff. A photograph of the SLS model mounted next to the launch tower is shown in Figure 1 and illustrates the test setup for measuring the effects of the launch tower on the vehicle. ...
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... and the results plotted versus wind azimuth angle and h/L. As an example, the tower effects repeatability for CYF is plotted versus relative height (h/L) in Figure 9, and plotted versus wind azimuth angle in Figure 10. Note in Figure 10 that there are no data for azimuth angles between 80 and 100due to the previously mentioned physical limitations of the turntable. ...
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... an example, the tower effects repeatability for CYF is plotted versus relative height (h/L) in Figure 9, and plotted versus wind azimuth angle in Figure 10. Note in Figure 10 that there are no data for azimuth angles between 80 and 100due to the previously mentioned physical limitations of the turntable. ...
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... was done for each force and moment coefficient. Figures 11-13 show summaries of the SLS ascent repeatability and experimental uncertainty bounds for CNF, CAF, and CYF, respectively. The solid red lines in the figures represent the 3-sigma experimental uncertainty bounds for each coefficient. ...
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... SLS transition database modeling residuals were computed for each aerodynamic coefficient and 3-sigma bounds were estimated. Plots of the modeling residuals and subsequent database modeling uncertainty bounds are presented in Figures 14-19. The residuals varied with total angle of attack for all coefficients except CAF ( Figure 15). ...
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... of the modeling residuals and subsequent database modeling uncertainty bounds are presented in Figures 14-19. The residuals varied with total angle of attack for all coefficients except CAF ( Figure 15). For the other five coefficients, the residuals were pooled over ranges of total angle of attack and the bounds estimated for each region. ...
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A combined experimental and numerical study was conducted on a generic projectile configuration with low-aspect-ratio fins. The main objectives of this study were to characterize the aerodynamic behavior and validate numerical simulations for a range of Mach numbers (0.4–4) to facilitate an understanding of major flow features such as forebody and fin-generated shock waves, crossflow shear layer vortex, and fin vortex interactions. Measurements included forces and moments, surface oil flow visualization, and high-speed shadowgraph imaging. Numerical simulations were performed using the CFD++ solver. The results showed an excellent match between the experimental and numerical force and moment data. Pressure contours obtained using numerical simulations were integrated to obtain the contributions of individual components toward the total normal force on the body. Flow visualization results show a few complex and interesting flow features, such as shear layer roll-up, crossflow and fin tip vortex interactions, and shock-wave–boundary-layer interactions. The effects of vortex strength and location were analyzed to determine their contributions to the overall forces on the model. The database generated will be very useful for further validation of the numerical tool and a better understanding of vortex-dominated supersonic flows.
View Video Presentation: https://doi.org/10.2514/6.2022-1335.vid Complex computational simulations are required to support the Space Launch System (SLS) program, and the fidelity of the computational results must be defensible. More specifically, a number of databases are produced for the transition phase of flight, which occurs after the rocket clears the launch tower but before reaching transonic speeds. In an effort to reduce computational uncertainty, many of the computational parameters were analyzed to determine the sensitivity of the results to the value of the parameter and then updating the best practice procedures. The baseline routines were developed over many years through the maturation of the SLS program, and this paper delivers a detailed discussion of these baseline results. This section is followed by demonstration of perturbing some of the more significant parameters, including time step and turbulence model, and concluded with a summary of the currently held best practices for such analysis.
