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NEWS | June 15, 2022

Carderock Collaborates on Tow Body Dynamics Effort

By Todd Hurley, NSWC, Carderock Division Public Affairs

Naval Surface Warfare Center, Carderock Division has collaborated with Naval Undersea Warfare Center, Newport Division in Rhode Island on an ongoing tow body dynamics effort known as MOLA.

The purpose of the MOLA is to bring a tow body that can collapse in on itself so a surface vehicle can pick it up out of the water and tow it via a cable. Its name derives from the ocean sunfish, or common mola, one of the two heaviest known bony fish in the world.

“MOLA is the name of a large fish, the ocean sunfish, that looks like a swimming billboard,” Dr. Jesse Daily said, Newport Division’s primary investigator for the MOLA collaboration. “This fish is the inspiration of the project. We knew we wanted to call it MOLA because we wanted that shape of fish but with a towed body.”

This is a Naval Innovative Science and Engineering-funded project that Newport Division started in 2020. Soon thereafter they brought in Carderock for the tow body dynamics aspect. The scale model construction and tow body testing portion of the effort takes place at Carderock, while Newport handles the acoustics research and modeling, electronics and the manufacturing.

“We are trying to get to a point where we have a tow body that can tow successfully and collapse upon itself,” Daily said. “Right now we are ready to start testing at a scale level to see how the tow body can complete its full evolution — deploy the system, have it expand, then collapse on itself and bring it back on the vessel. A big challenge is how to get it to be able to collapse enough to get it onto a ship.”

Jason Morin, a mechanical engineer in Carderock’s Maritime Systems Hydromechanics Branch, is in charge of the tow model testing done at Carderock, after taking over for the recently retired Dr. David Coakley.

“Newport came here because we have done a lot of towing and are known for our expertise,” Morin said. “Over the last couple of years with this project, we have provided our expertise on hydrodynamics and have performed analysis. There are a lot of ways this work could be done — we’ve been exploring the best way possible. Some models have rigid tubes, others have flexible tubes. We are still exploring what would work best, and figuring out how to fabricate what it is made of and how it will function once it is in the water.”

Testing at Carderock has consisted of tow body stability, array stability, hydrodynamics in the tow body, tow body stability over speed ranges and how to expand and collapse a tow body.

“We started at square one — figuring out the design routes to see plausible routes,” Morin said. “In 2021, we built the big scale model array that we towed in the carriage three basin. From that work it informed the next steps. From there, Newport started building the full scale flexible tube array, and we did a scale model test here at Carderock to inform them of what to expect when they do a full-scale test.”

Four different tests have been conducted at Carderock: one in the circulating water channel and three different scale model tests in the carriage three high-speed basin.

“It’s been a lot of fun learning what will and will not work,” Daily said. “It seems quite simple, being that it is essentially a bundle of PVC pipes. But, it took us a long time and was a feat of engineering that has not yet been accomplished — it is quite significant that we were able to accomplish what we have. What can kill this project is not being able to get it on and off a vessel, but we’ve shown that we can get it down into a small enough package to be able to do it.”

Morin and Daily are hoping to be concluded with the project later this year, with an overall goal of being picked by the Office of Naval Research (ONR) for further development.

“Our goal is to get picked up by ONR or some other entity that would turn this into a program of record and fully develop the system,” Morin said. “We think it will be very beneficial to the warfighter and to the Navy in general.”