Multiphase Simulations of the Launch Environment at NASA’s Kennedy Space Center
Overview
To support NASA’s Artemis missions launching aboard the new Space Launch System (SLS), as well as launches by the agency’s commercial partners, the Launch Ascent and Vehicle Aerodynamics (LAVA) team in the NASA Advanced Supercomputing (NAS) Division are pushing the state of the art for numerically predicting ignition overpressure (IOP) waves in launch environments. These waves are formed during the ignition of rocket engines and pose a safety hazard by creating unwanted vibrations that may damage the vehicle or support structures. NASA launch complexes have long used water injection in the flame trench and at exhaust openings to absorb some of the powerful acoustic wave energy. Despite the widespread use of water-based sound suppression systems, engineers are still working to gain a full understanding of their effectiveness, due to the extreme complexity of the launch environment. Vital information about the IOP intensity is needed to ensure mission safety, yet achieving accurate numerical prediction of IOP intensity has been impeded by a lack of capable analysis tools.
Project Details
To address this problem, the LAVA team developed a new computational approach for simulating multiphase (gas-liquid) flows that can robustly solve the extreme flow conditions in the launch environment and still accurately capture the acoustic IOP wave propagation. In collaboration with the Launch Services Program (LSP) at NASA’s Kennedy Space Center (KSC), the LAVA team used this new capability to simulate the Space Test Program (STP)-2 mission launch, which flew on SpaceX's Falcon Heavy rocket from KSC’s Launch Complex (LC) 39A. The simulation showed excellent agreement with flight measurements and was a significant breakthrough for computational IOP prediction. The LAVA team is applying this multiphase capability to carry out challenging realistic launch simulations, in order to study acoustic wave propagation from the complex interactions of rocket engine plumes with the flame trench and water-based sound suppression systems.
Simulations of the launch environment provide rich details of the complex interactions between supersonic rocket plumes and liquid water. The LAVA multiphase solver has now been applied to other launch configurations, including the SLS Scale Model Acoustic Test (SMAT) and the full-scale SLS launch environment. As more cases are run and comparisons are made to measured data, the LAVA team continues to modify and improve their best practices to achieve the best predictions possible.
Results and Impact
The impact of this new capability is also being felt in NASA's Artemis missions. To help ensure the safety of the upcoming Artemis flights, NASA Exploration Ground Systems (EGS) engineers needed estimates of the acoustic loads on the Mobile Launcher (ML) surface during the SLS ignition. The LAVA team created full-scale simulations for the SLS at LC-39B, including the sound suppression system—providing EGS engineers with SLS acoustic IOP predictions, along with the predicted pressure field on support structures.
The impacts of this work are twofold: first, the new capability represents an achievement in fundamental research in applied mathematics; and second, these methods were able to be quickly adopted into the LAVA framework, which opened the possibility of applying these new methods to practical engineering problems. With the increasing number of NASA and commercial launch missions, the availability of a well-validated and robust multiphase CFD tool will serve the agency now and in the future.
Why HPC Matters
Each of the LAVA team’s high-resolution simulations of the launch environment at LC-39B used approximately 400–500 million grid cells and ran several weeks on 8,000 cores of either the Electra supercomputer’s Skylake processors or Aitken’s Cascade Lake processors. Because these simulations are time dependent, they generate roughly 400 terabytes of data for each run. Visualization of these results provides insight into the complicated flow conditions of the launch environment, and required reliable data storage, high-performance data I/O, and the powerful visualization tools provided by the NAS Division’s Visualization and Data Analysis team—who always strive to achieve the greatest possible utilization of complex datasets generated by NAS computational resources.
What's Next
With the Artemis I flight, new flight data will be available to further validate the LAVA solver’s predictive capability, serving as an effective ‘’blind’’ validation case for the code. Furthermore, the code is currently being modified to run on GPU accelerators to enhance turnaround time and leverage new compute architectures. The goal is to provide crucial CFD information for designs in a reasonable turnaround time to accommodate launch pad modifications, changes to the water-based sound suppression system, and new vehicle designs.
Researchers
- Jordan Angel, NASA Ames Research Center Please enable Javascript to see email address.
- Scott Neuhoff, NASA Ames Research Center Please enable Javascript to see email address.
- Michael Barad, NASA Ames Research Center Please enable Javascript to see email address.
- Cetin Kiris, NASA Ames Research Center Please enable Javascript to see email address.
