Design Engineering

Submersible drone can hide underwater then launch to perform aerial missions


General Defense uav

The design team had to overcome two significant challenges of adapting an aerial vehicle for underwater use.

Researchers at the Johns Hopkins University Applied Physics Laboratory (APL) have successfully designed a reliable sea-to-air unmanned aerial vehicle (UAV). Dubbed CRACUNS, the Corrosion Resistant Aerial Covert Unmanned Nautical System is able to stay stationed underwater and then launch into the air for flight.

CRACUNS submersible John Hopkins

The Corrosion Resistant Aerial Covert Unmanned Nautical System — or CRACUNS — is a submersible UAV that can be launched from a fixed position underwater, or from an unmanned underwater vehicle (UUV). Credit: Johns Hopkins APL

The John Hopkin’s drone operates in two very different arenas, air and water, which posed some significant design challenges.

The team from APL’s Force Projection Sector worked with fabrication experts in the Research and Exploratory Development Department to create a new type of unmanned vehicle that can be launched from a fixed position underwater or from an unmanned underwater vehicle (UUV).

“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. “We were inspired to develop a vehicle that could operate both underwater and in the air.”


The resulting CRACUNS prototype system was developed and tested using internal research and development funding.

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.

This was a challenge for the design team that needed to overcome some factors restricting the project. First, the APL team leveraged advances in additive manufacturing and novel fabrication techniques available at the Laboratory’s extensive fabrication facilities. The team fabricated a lightweight, submersible, composite airframe able to withstand the water pressure experienced while submerged.

The second significant challenge was to ensure CRACUNS could operate effectively in a corrosive saltwater environment. The APL team 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 novel additive manufacturing techniques used on CRACUNS.


Stories continue below

Print this page

Related Stories