Simulation Brings Confidence For First Flight

Engineers at NASA’s Langley Research Center in Virginia are doing their part to enable NASA’s 5.5-million-pound SLS to launch the Orion spacecraft to deep space. To understand the aerodynamic forces exerted on the rocket as it flies through the atmosphere, Langley engineers recently tested a 35-inch SLS booster separation model in its Unitary Plan Wind Tunnel, with air speeds of over 2,400 mph. The engineers collected high-fidelity data from 800 runs.

Just over two minutes into the first flight of SLS, 16 booster separation motors will fire simultaneously and safely push the two solid rocket boosters away from the rocket’s core. As the core stage continues to travel at a speed greater than four times the speed of sound, the boosters reenter the Earth’s atmosphere and land in the Atlantic Ocean.

“Booster separation is a very critical phase of flight for the Space Launch System because the clearance between the core stage and the boosters is very small as they are pushed away,” said Langley engineer Jeremy Pinier. “It’s only about an inch full-scale so the boosters are almost grazing the core stage, but we can’t allow any contact whatsoever between the two in the real flight.”

The wind tunnel test, which validates an accurate clearance, was unlike any other. “It’s a pretty complex wind tunnel test,” Pinier said. “Usually we measure aerodynamic forces on a single model in the test section. Here we have three – the core and two solid rocket boosters – which makes it three times as difficult. We are also flowing very high pressure air through the booster separation motors, which is pretty unique, and an added challenge.”  

Due to the inherent complexity of the model design, test setup, tunnel operations and multi-dimensional parameter space, engineers spent four weeks installing the model into the tunnel prior to testing.

“We had to make sure we controlled exactly the positioning of the three bodies relative to each other,” Pinier explained. “At these small scales, we have to know within thousandths of an inch how well the model is positioned because when you translate it to a full scale distance, it immediately matters.”

With the successful completion of installation and testing of the SLS model, Pinier couldn’t help but reflect on how grateful he is for the opportunity.

“I have my dream job,” Pinier said with a big grin on his face. “Every day I drive through the NASA gate I know I’m helping to design the biggest rocket that has ever been built. It’s super exciting. Maybe one day I’ll even fly on this rocket, which would be even better.”

(Image provided by NASA)

FMI: www.nasa.gov