The final frontier
The ocean has always been a subject of deep wonder and mystery. But did you know that only less than 0.05 percent of the ocean floor has been mapped so far to a level of details useful for detecting items such as the wreckage of a missing aircraft? In fact, we know more about the surface of Moon or Mars than the ocean floor.
In recent decades technology has begun to give us a glimpse of the deep-sea landscape. Submersibles can carry people to the deepest depths of the seafloor and autonomous vehicles can map a geography never seen by human eyes.
Film producer and director James Cameron garnered world attention in 2012 when he descended to the deepest part of the Mariana Trench at a depth of 10.9 km in a submersible he helped build, called the Deepsea Challenger. Humans had only made that trip once before, when Jacques Picard and Donald Walsh piloted the deep-diving vehicle Trieste there in 1960.
Operating at great pressure
For a long time, all deep-sea vehicles needed to be protected by a pressure hull made of aluminium, ceramics, high-grade steel or titanium. Because hydrostatic pressure increases with diving depth, pressure hulls need to have thick walls and become very large, heavy and expensive. The alternative is pressure-tolerant vehicles without pressure hulls, where all the systems are instead fluid compensated.
New, promising deep-sea technology
Enitech GmbH of Rostock in Germany has been working on deep-sea technology since 2000. After developing pressure-tolerant thrusters and power supply systems for Autonomous Underwater Vehicles (AUVs*) such as DeepC and others, Enitech came up with their own pressure-tolerant vehicle – the Erno2 – that has now been successfully tested on several deep-sea missions.
The novelty with Erno2 is that all the important subsystems ¬are protected with elastic silicon molds. This new technique, developed at Enitech, is set to replace the oil-filled containers that were previously used for pressure compensation, and is to become the enabling technology for compact, lightweight, robust and cost-effective unmanned deep-sea vehicles.
Erno2 – small and flexible
Erno2 is a remotely operated vehicle (ROV*) approved for dives down to 6,000 meters. It was originally designed for a project called “DNS Tiefsee” aimed at developing pressure-tolerant underwater vehicles. The project was funded by the German Federal Ministry of Economics and Technology (BMWI). Two vehicles were built and are still in use in the following project SMIS – Subsea Monitoring via Intelligent Swarms – also funded by BMWI.
Less than 1 m wide, the 420 kg Erno2 is a relatively small ROV. All the equipment takes up only a half of the standard 20-foot container, making Erno2 one of the world’s smallest deep sea ROVs. Operating depths of 6,000 meters are possible due to the vehicle’s pressure tolerant construction using buoyancy-generating syntactic foam distributed by Diab.
“The syntactic foam compensates for the weight of the equipment at the working depth”, says Gerrit Steffens, Sales Manager at Diab Germany, who’s been involved in the project. “It resists to very high seawater pressure yet keeps all buoyancy characteristics at their nominal value. Using syntactic foam means that submersible vehicles no longer need to be encumbered by thick, heavy frames made of higher density material.”
* ROVs are unmanned vessels controlled by scientists onboard a ship via a tether cable. An AUV can navigate and collect scientific data without any human control.
Read more about Enitech GmbH (in German).