Researchers at Johns Hopkins University’s Applied Physics Laboratory (APL) in Laurel, Maryland, have developed an innovative unmanned aerial vehicle (UAV) that can be stationed underwater, then launch into the air to perform a variety of aerial missions.
This new submersible UAV, called Corrosion Resistant Aerial Covert Unmanned Nautical System (CRACUNS) can be launched from a fixed position underwater, or from an unmanned underwater vehicle (UUV). The team from APL’s Force Projection Sector worked with fabrication researchers in the University’s Research and Exploratory Development Department (REDD), to create a new type of unmanned vehicle that can operate with equal effectiveness as a UUV and a UAV, underwater or in the air, two very different environments.
CRACUNS is a true game changer, enabling new capabilities not possible with any existing UAV or UUV platforms. Its ability to operate in the harsh shore environment, the littoral region between the open sea and the shore, as well as its payload flexibility, enables a wide array of potential missions. Parts of CRACUNS are 3D printed to create a light, watertight body, and other parts are coated in commercial sealant, to keep water out of its motors.
Jason Stipes of APL’s Sea Control Mission Area is the project manager for CRACUNS. He and his team were inspired to develop a vehicle that could operate both underwater and in the air in response to evolving sponsor challenges. The resulting CRACUNS prototype system was developed and tested using internal research and development funding.
According to the Johns Hopkins team, CRACUNS low cost makes it expendable, and therefore cost effective, but its most innovative feature is that it can remain at, and launch from, a significant depth without needing structural metal parts or machined surfaces. In tests, it survived two months under water, and was still able to launch and fly afterwards.
In creating such a unique vehicle, the team defined its two major challenges. First, the unprecedented fabrication techniques they needed. At the Laboratory’s extensive fabrication facilities, the team had to create a lightweight, submersible, composite airframe able to withstand the water pressure it would experience while submerged.
The second major challenge was to ensure CRACUNS could survive and operate effectively in corrosive saltwater. To test this, the APL team sealed the most sensitive components in a dry pressure vessel. They applied common, commercially available protective coatings to the motors that were exposed to salt water. Then, they submerged the motors in saltwater for two months. Amazingly, at the end of the test period, the motors showed no sign of corrosion and continued to operate while submerged.
APL’s Rich Hooks, an aerospace and mechanical engineer, was responsible for the novel additive manufacturing techniques used on CRACUNS. He believes that CRACUNS successfully demonstrated a new way of thinking about the fabrication and use of unmanned systems.
CRACUNS gives sponsors and researchers access to possibilities that were previously unavailable. Its low-cost expendability allows for the use of large numbers of vehicles in high-risk scenarios.