Aerodynamic Databases for the Space Launch System

Overview

NASA’s new Space Launch System (SLS) will be the first rocket since the Saturn V to carry astronauts beyond low-Earth orbit, carrying 10% more payload than Saturn V and three times the payload of the space shuttle. The SLS configuration consists of a center core and two solid rocket boosters that separate from the core when their fuel is exhausted two minutes after liftoff. During these first two minutes of flight, the vehicle powers its way through strong shock waves as it accelerates past the speed of sound, withstands strong aerodynamic loads at the maximum dynamic pressure, and is enveloped by gaseous plumes from the booster-separation motors. The SLS program relies on computational fluid dynamic (CFD) simulations to provide much of the data needed to build aerodynamic databases describing the structural load distribution, surface pressures, and aerodynamic forces on the vehicle.

Project Details

The goal of this project is to quantify the aerodynamic forces on the SLS vehicle from ascent through booster separation via CFD simulations. We use multiple CFD tools to perform the analysis, including the NASA-developed flow solvers Cart3D, OVERFLOW, and FUN3D. Results provide data to build numerous aerodynamic databases, which are used by engineers to help design and analyze the SLS systems. Previous launch systems relied almost entirely on wind tunnel testing to obtain the data to build these databases; fortunately, with the continued growth of computational resources and capabilities, it is feasible to use more modeling and simulation, and fewer expensive wind tunnel tests. Over the course of this project, NASA has continually analyzed several different SLS vehicle designs, including: multiple design iterations of the first flight Block 1 vehicle, which will launch in the unmanned Exploration Mission-1 (EM-1); designs for the crewed Exploration Mission-2 (EM-2), and the first cargo mission, the Europa Clipper; and multiple designs of the SLS Block 1B configuration, which is planned for use after the first three or four flights.

Results and Impact

We have created several different aerodynamic databases for the SLS designs, including: distributed line-loads used in structural analysis; surface pressures used in venting and other flow dynamics analysis; protuberance aerodynamic loads used in the design of the vehicle; and forces and moments on the vehicle during booster separation used to verify the booster-separation system.

Why HPC Matters

All of our CFD simulations were run on the Pleiades and Electra supercomputers at the NASA Advanced Supercomputing (NAS) facility. The project has used over 75 million core hours at the NAS facility in the past year. Depending on the configuration and flow conditions, each FUN3D simulation requires approximately 4,000 to 12,000 core hours, and the OVERFLOW runs require 10,000 to 30,000 core hours. Approximately 8000 simulations using about 125 million core hours were used to build the various databases including aerodynamic forces and moments, distributed line loads, surface pressures, protuberance air loads, etc. In addition, the project typically uses 50 to 100 terabytes of short-term disk storage at any given time.

What’s Next

The SLS CFD team will continue to provide aerodynamic analyses as the vehicle design evolves.

More Information

• Building Aerodynamic Databases for the SLS Design Process
• See the poster for this demonstration (PDF, 1.9MB). As shown in the NASA booth at SC18.