Technology
The challenging conditions at 372 m water depth require specific equipment. The elements of the system have been designed after studies of deep sea research gear, engineering fundamentals and underwater photography.
Bottom Lander
The photographic system consists of three tubes which are connected through aluminium profiles to a triangular structure. Two tubes contain light system, the third a camera. The system should allow a deployment of several hours.
Pressure housing
At 372 m depth the water exerts a pressure of 38.4 bar. A housing made of steel tubing was designed and constructed. The tubing has a wall thickness of 2 mm, the rear wall of 5 mm, all stainless steel (Stainless steel tubing, 76 mm diameter, 300 mm L, 2 mm wall, 1,1 kg).
The front closures are made of acrylic glass, with a thickness of 20 mm. They are held in place by 6 mm stainless steel screws. The sealing is done by a rubber gasket of 93 (i.d.) 199 (o.d.) diameter.
Camera
Initial test will be made with a GoPro 4 camera (GoPro hero 4 black, size: 59 x 41 x 29 Millimeter). The camera will be set-up for still shots in a fixed intervall.
Light
2 LED wide angle bulbs and lithium-ion batteries (2 Ampere, 12 V).
Recovery system
A fishing reel (WFT Offshore LW, LC 30 RH, Line counter) with 600 m 0.25 diameter braided line (WFT new strong, 0.25 mm) will be used for guiding and recovery of the system. The reel is mounted on a wooden support with a guiding roll at the front. An exact balancing of the system will allow a slow guided decend, whereas the ascent will occurr via the dropping of a small amoubnt of ballast through a dedicated release system.
Release system
The deployment of the system for several hours will require an autonomous release system which provides negative buoyancy through a deployable weight and releases the weight after a predetermined time, allowing the system thewn to surface.
Options for release system:
- Remote pin release - triggered by pulling at fishing line (mechanical release)
- Electromagnetic release - electric magnet neutralises magnet and releases weight
- Galvanic/corrosion triggered release - corrosion of calibrated wire releases weight (salt water)
- Acoustic release system - acoustic signal is transmitted, received and triggers a motor driven weight release)
- Burn wire release - relais switched a currnet to a constatan wire which heats up and melt fishing line for release of weight
- Salt based release system
System development
After showing the feasibility of the approach and discovering interesting features of the lake bottom, next steps should provide some additional possibilities:
Therefore from 2019, a microcomputer based system was developed, assembled and functionalities dry-tested.
Microcomputer based camera system
After showing the feasibility of the approach and discovering interesting features of the lake bottom, next steps should provide some additional possibilities:
- Improved image quality by using a different camera type
- Enabling system start with closed housing
- Potential recording of data (e.g. temperature, depth)
Therefore from 2019, a microcomputer based system was developed, assembled and functionalities dry-tested.
Microcomputer based camera system