Computational fluid dynamics (CFD) simulations aided critical early SLS design decisions, when wind tunnel data was not yet available, and continue to support more complex SLS design analyses. Power-on simulations of the Space Launch System (SLS) were performed to analyze the base pressure and nozzle hinge moments. The plot shows contours of pressure coefficient on the cutting plane and streamlines that indicate the velocity flow patterns. The plume structure displays rich shock diamond structures generated by the underexpanded SRB jets, and the bow shock from the SRB nose interacts with the boundary layer along the core stage. Image credit: NASA Ames / Jeffrey Houseman / Cetin Kiris
Computational Fluid Dynamics (CFD) simulations are being performed to support the design of NASA's next generation launch vehicle, the Space Launch System (SLS). Modeling and simulation support includes characterizing the aerodynamic performance of the vehicle for a suitable ascent trajectory, determining the distributed aerodynamic line loads along the vehicle for structural analysis, and providing surface pressure signatures to assist in venting design for components of the vehicle.
During the early design of the SLS, focus is placed on the stability and control of the vehicle during ascent and maintaining structural integrity throughout the mission. Characterization of the aerodynamic environments plays a key role in providing the necessary inputs for the Guidance Navigation and Control and the Structural Loads groups. In order to determine these environments before the vehicle is built, CFD simulations of SLS are performed at select points over the ascent trajectory and multiple angles of attack. The integrated and distributed aerodynamic loads on the vehicle are then extracted from the CFD solution and provided as input data for trajectory and structural analysis which are used to improve the design of the vehicle. In addition to providing information to modify the exterior shape and the interior structural components of the SLS, surface pressures over specific components of the vehicle are extracted and provided to the Venting group. This data is then used to determine were proper venting should occur along the vehicle.
Results and Impact
CFD simulations have been used to aid in critical design decisions for SLS early in the design cycle when wind tunnel data was not yet available. The ongoing modeling and support effort is having a large impact on import design decisions including:
- Down selecting from several vehicle shapes
- Outer Mold Line (OML) of the vehicle
- Structural analysis of the core-stage and protuberances
- Core-stage main engine hinge moment analysis
br> br> CFD support for SLS will continue to advance as the vehicle matures and will make major impacts on:
- Booster separation analysis
- Core-stage fairing and main engine layout
br> Role of High-End Computing Resources and Services
NASA's Advanced Supercomputing facilities enable fast and efficient turnaround time for CFD simulation support of SLS. The Pleiades machine allows viscous aerodynamics databases including several hundreds of simulations to be completed in under a week using 300 cores and 40 hours of wallclock time per simulation.
Researchers: Jeffrey Housman and Cetin Kiris, NASA Ames Research Center