National Renewable Energy Laboratory
US Department of Energy
Golden, CO
www.nrel.gov

What does wave energy have to do with space exploration? It turns out, plenty. NASA is working toward launching the Artemis I mission, an uncrewed lunar test flight, in 2021. It will be the maiden flight of the Space Launch System heavy-lift launch vehicle as well as the Orion crew module (CM). Orion will orbit the Moon for multiple days before returning to Earth and landing in the Pacific Ocean.

Wave energy experts at the National Renewable Energy Laboratory (NREL) are helping to ensure the safety of Orion’s future crew between splashdown and recovery. NASA and Lockheed Martin (LM) — NASA’s prime contractor for Orion — are using the Wave Energy Converter SIMulator (WEC-Sim), an open-source code developed by NREL and Sandia National Laboratories, to ensure that the CM uprights upon landing.

During the Apollo program, the CM landed upside-down in the ocean in nearly half of all missions. When the CM is inverted or sideways, hatch doors and communications antennae can become submerged. An upside-down module can also impede recovery operations, as a submerged antenna can cut the recovery team’s communications with the CM.

The Orion CM in the desired “Stable 1” configuration with crew access hatch accessible (left) and the undesired “Stable 2” orientation with antennae and crew hatch submerged (right). (Photo courtesy of NASA)

To address this persistent challenge, NASA/LM is planning to use the Orion Crew Module Uprighting System (CMUS) that consists of five airbags intended to right the CM in the event of an inverted ocean landing and maintain the craft’s upright position for 24 hours. The team is employing the WEC-Sim tool to model the dynamics of the CM in the open ocean to aid in evaluating CMUS’s performance and loads. Knowing the dynamics of how the CM and its uprighting system will perform is critical to ensuring a swift and safe recovery operation.

NASA’s Orion program evaluates an updated design to the CMUS — the system of five airbags on top of the capsule that inflate upon splashdown — at the Neutral Buoyancy Lab at NASA’s Johnson Space Center in Houston. (Photo courtesy of NASA)

The WEC-Sim tool models the forces on floating objects and calculates their dynamic behavior including devices comprising rigid bodies, joints, power takeoff systems (PTOs), and mooring systems. In other words, WEC-Sim allows researchers to better understand how devices that convert the motion of waves into usable energy will fare in the open sea. And this improved understanding can help to replace some of the would-be physical testing with computer modeling.

“Unlike the Apollo Uprighting System that came before it, the Orion CMUS will be subjected to a much smaller number of tests, instead relying more heavily upon modeling. This is where WEC-Sim comes into play,” said Tannen VanZwieten of the NASA Engineering and Safety Center.

“WEC-Sim caught our attention as a viable option for modeling the dynamics of the CM in the open ocean since its size is similar to that of the wave energy converters that WEC-Sim was designed to simulate,” said VanZwieten. “Both require a fairly high-fidelity model of the interaction with the wave field to capture the motion of the system.”

Essentially, WEC-Sim is helping NASA/LM to credibly model forces and the motion of the CM in the ocean.

“WEC-Sim features floating-body dynamics that can be customized to fit NASA’s needs,” said NREL researcher Nathan Tom. “This tool can also help optimize wave energy converter designs to minimize the cost of energy.”

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This article first appeared in the December, 2020 issue of Tech Briefs Magazine.

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