Giving Rocket Science a Boost

According to a 2008 entry in the Encyclopedia Britannica blog, "it's not rocket science" is distinguished as one of the top 10 most overused and useless expressions in the English language. But as NASA pours both its brainpower and supercomputing power into developing a new heavy-lift Space Launch System (SLS) for human exploration far beyond Earth, expertise in rocket science is exactly what's needed for success.

To facilitate this notoriously difficult endeavor, modeling and simulation experts in the NASA Advanced Supercomputing (NAS) Division at Ames Research Center are performing high-fidelity simulations that supply key aerodynamic data to the agency's aerospace engineers. These cutting-edge simulations, run on NASA's Pleiades and Columbia supercomputers, will be crucial to streamlining the speed and cost of the SLS design process while also ensuring the highest possible performance and safety standards.

Computational fluid dynamics simulations of preliminary crew and cargo launch vehicle design candidates. Jeffrey Housman, NASA/Ames

NAS computational fluid dynamics (CFD) experts use specialized, NASA-developed codes to model evolving SLS vehicle designs and compute the detailed aerodynamic flows, forces, and interactions that could affect mission success and safety during launch. Their results supplement limited wind tunnel data and enable more conditions and designs to be assessed—all at a fraction of the cost and time that would be required to obtain data through testing alone.

"Results from our analyses enable designers and engineers to optimize the vehicle's shape and launch trajectory for better performance," said Cetin Kiris, chief of the NAS Applied Modeling and Simulation Branch. "They are also used to assess the amount of structural stress, heating, and vibrations that the vehicle will encounter during launch," he continued. Other key design areas that CFD results will impact include the type, number, and layout of rocket motors, and the amount of thermal protection material needed to shield the vehicle.

CFD simulations have already contributed to critical, early design decisions for the SLS, before experimental or flight data could be obtained. For example, CFD analyses helped to compare the alternate architectures that were being considered during the vehicle's preliminary concept phase, and are currently being used to assess the next round of crew and cargo launch design variations.

The team's CFD analyses are also now providing an important first stepping-stone for the SLS's initial design analysis cycles—the process by which the various design elements are successively updated, reanalyzed, and refined.

"At the beginning of each design cycle, CFD simulations quickly provide the aerodynamic data needed to support further trajectory adjustments, structural analyses, and other key studies," explained Kiris. The fast turnaround of the CFD data—which can often be generated within just a few days, thanks to NAS supercomputers and modeling expertise—greatly expedites the design cycle process and will be pivotal to meeting the agency's ambitious goal of launching the first SLS flight around the end of 2017.

As the SLS design continues to mature, increasingly high-fidelity simulations will be used to assess both more detailed design features and more complex aerodynamic phenomena, such as the effects of the vehicle's various rocket plumes.

Although the SLS is still in the early stages of development, the NAS CFD team has already laid significant groundwork for accurately analyzing these challenging problems. Over the past year, they have refined CFD codes and post-processing tools, and have studied numerous modeling techniques to established best-practices for heavy-lift launch vehicle simulations.

These high-fidelity CFD models will give SLS engineers ready access to more valuable performance data and allow them to proactively consider complex design factors with even greater acuity. While rocket science may always represent the epitome of difficulty and complexity, NASA's powerful supercomputers and simulation capabilities are helping to make the infamous discipline a little less daunting, enabling precision-engineering more easily than ever before.

Giving Rocket Science a Boost

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