The CRACUNS wakes: APL team develop submersible UAV that stays on station before aerial mission

News

Researchers have revealed an unmanned aerial vehicle that can maintain its position under water and then launch into the air to perform different missions.

Developed at the Johns Hopkins University Applied Physics Laboratory (APL) in Maryland, CRACUNS - Corrosion Resistant Aerial Covert Unmanned Nautical System - is a submersible UAV that can be launched from a fixed position underwater, or from an unmanned underwater vehicle (UUV).

The system is capable of operating in the harsh littoral environment and its low cost makes it expendable, allowing for the use of large numbers of vehicles for high-risk scenarios.

A team from APL’s Force Projection Sector worked with fabrication experts in the lab’s Research and Exploratory Development Department to create CRACUNS.

“Engineers at APL have long worked on both navy submarine systems and autonomous UAVs,” said Jason Stipes of APL’s Sea Control Mission Area, project manager for CRACUNS. “In response to evolving sponsor challenges, we were inspired to develop a vehicle that could operate both underwater and in the air.”

According to APL, the most innovative feature of CRACUNS is that it can remain at and launch from a significant depth without needing structural metal parts or machined surfaces.

To make that possible, the team took advantage of advances in additive manufacturing and novel fabrication techniques available at the Laboratory’s fabrication facilities to fabricate a lightweight, submersible, composite airframe able to withstand the water pressure experienced while submerged.

The team then made sure CRACUNS could operate effectively in a corrosive saltwater environment. To do that, they sealed the most sensitive components in a dry pressure vessel. For the motors that are exposed to salt water, APL applied commercially available protective coatings. The team tested the performance of the motors by submerging them in salt water. Two months later, they showed no sign of corrosion and continued to operate while submerged.

“CRACUNS successfully demonstrated a new way of thinking about the fabrication and use of unmanned systems,” said APL’s Rich Hooks, an aerospace and mechanical engineer who was responsible for the additive manufacturing techniques used on CRACUNS.