Exploration of the Steamer Tahoe ShipwreckMarch 30 2014
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I made a few small modifications to my OpenROV so it could fly deeper:
-A 1/4" tube to replace the 1/8" standard tube
-Thicker endcaps. A 1/2" core replaces the 1/4" standard core. To make room for the thicker cores, I permanently glued one endcap which then did not need the inner portion. I also thinned the e-chassis to make even more room.
-I used a thicker material for the battery tubes and the battery tube endcaps.
Those are all the changes made to increase depth, but I also added lights to the ends of the battery tubes. I wanted to move them further from the camera and outside the e-tube. Unfortunately, as you could see from the video, placing them on the lowest part of the ROV was problematic. They lit the wrong things and in addition, they added buoyancy to the front, which is awkward.
Thanks to the tests and trials this weekend, I now have a new list of modifications to make. Hooray!
After bringing the ROV up from a depth of 93 meters (over 300 ft) we believe we have determined the cause of the failure. The endcaps on this ROV are similar to the traditional endcaps but there is one layer that is aluminum instead of plastic. As the ROV descended and the pressure increased, these layers delaminated (seen on the right side of the image) causing water to flood into the electronics tube. We believe that this happened at a depth of just over 50 meters after analyzing the video and the rate of decent. With the endcaps failed, there was a tremendous amount of pressure on the electronics chassis and the shock of hitting the bottom of the lake caused the chassis, including the electronics board, to snap (as seen in the middle of the image). Once the electronics board snapped communication with the ROV was lost.
I'm getting really excited to try out this new long-range wireless system. We got a (very fancy) house right on the shoreline of Glenbrook Bay, just over 1km away from the wreck of the SS Tahoe. Our plan is to deploy the ROV from a small inflatable boat but have it be commanded from a control station in the house on shore. Here's a diagram...
We just bought all the communication equipment for this weekend's deployment! Because the cabin we're considering is up on a hill, we may be able to make a straight shot to a boat above the Tahoe in Glenbrook Bay some 5.4km away. If this works, we could control the ROV in extreme comfort!
Our dive next week is in the middle of Lake Tahoe's "off" season. Because snow storms and cold temperatures are still common in April, most of the large boats around Tahoe are still winterized and won't be on the water until May. Since more then 15 people are likely to be participating in this preliminary expedition, we'll need some way to do the dive from shore.
The SS Tahoe is more then a kilometer off shore, so we've come up with a deployment plan that utilizes a long-range wireless Ethernet bridge to communicate from shore to a small inflatable boat that could be stationed above the wreck. With only two or three people in the boat (to manage tether, communicate with the shore, and keep the boat on station) the rest of the party should be able to command the ROV from a station set up on the shore or even the cabin we're all planning to stay at.
Here's the system architecture we're considering:
Next weekend, we plan to do a preliminary dive on the SS Tahoe in order to gather information about the wreck, experiment with deployment methods, and test equipment.
Because the SS Tahoe lies at a depth well beyond what the OpenROV submarine was designed for (the deepest part of the wreck is more then 150m underwater), we'll need to a thicker main tube and reinforced endcaps to withstand the pressure.
Using a waterjet at TechShop in San Jose, I've crafted some special endcap flanges out of 1/4" aluminium which should make the them much stronger. Using the pressure chamber at OpenROV HQ, we were able to test the endcaps to a depth of about 130m, but the only way we'll know if they can handle the full depth of the ship will be to dive there!
In 1940, the 50m long "Steamer Tahoe" was skuttled in Glenbrook Bay on the east side of Lake Tahoe in Nevada. The owners of the steamship intended for it to sink in shallow enough water for tourists to see it from a glass-bottom boat, but the ship was sunk too far from shore and ended landing on a slope and sliding do a depth between 110 and 150m. Because of its great depth in a high-altitude lake, very few divers have ever been able to see the sunken ship, and no footage has been recorded of the ships interior. Our mission is to find the SS Tahoe using OpenROV submarines and record video of its hull and interior.