Here is the Full Report from the ERGOnaut I Expedition on 24Nov12:
We built up the ERGOnaut diving instrument with a housing made from 12mm-thick 250mm-diameter aluminum tubing, a 25mm-thick aluminum plate on one end, and a 100mm-thick clear acrylic (plexiglas) cover on the other end. We went with the clear window so we could have a camera inside to take pictures during the dive. Lighting was provided by an external underwater LED flashlight filled with mineral oil (to prevent collapse of its housing). Battery power was from a 4000 mA-Hr 11.1V LiPo battery, which can run the ERGO for 11 hours.
During the dive, energetic-particle event data would be recorded on the micro-SD card of the datalogger, so we could analyze the data when the ERGOnaut was brought back up to the surface. The Geiger-Muller detector and ERGO timestamp generator board were exactly the same as the 115 units we have sent out around the world.
Our plan was to drop the ERGOnaut on a 200-lb-test fishing line (spectra fiber) to a depth of 2580 feet, approximately 30 miles east of Miami. When we got to that location, we found the seas too rough to attempt the drop (8-10ft seas!), so we relocated to a calmer location east of Elliot Key (latitude 25.50981889N; longitude 80.06057306W, 470 ft depth). We put the ERGOnaut into the water at that location, but a failure in the winching system caused the instrument to descend to the bottom rather than hovering above the bottom. When it got to the bottom it became snagged on something, and none of our efforts to dislodge it were successful. Our last-ditch attempt was to pull on the line as hard as possible; the ERGOnaut didn’t budge, and the line broke.
We built up the ERGOnaut diving instrument with a housing made from 12mm-thick 250mm-diameter aluminum tubing, a 25mm-thick aluminum plate on one end, and a 100mm-thick clear acrylic (plexiglas) cover on the other end. We went with the clear window so we could have a camera inside to take pictures during the dive. Lighting was provided by an external underwater LED flashlight filled with mineral oil (to prevent collapse of its housing). Battery power was from a 4000 mA-Hr 11.1V LiPo battery, which can run the ERGO for 11 hours.
During the dive, energetic-particle event data would be recorded on the micro-SD card of the datalogger, so we could analyze the data when the ERGOnaut was brought back up to the surface. The Geiger-Muller detector and ERGO timestamp generator board were exactly the same as the 115 units we have sent out around the world.
Our plan was to drop the ERGOnaut on a 200-lb-test fishing line (spectra fiber) to a depth of 2580 feet, approximately 30 miles east of Miami. When we got to that location, we found the seas too rough to attempt the drop (8-10ft seas!), so we relocated to a calmer location east of Elliot Key (latitude 25.50981889N; longitude 80.06057306W, 470 ft depth). We put the ERGOnaut into the water at that location, but a failure in the winching system caused the instrument to descend to the bottom rather than hovering above the bottom. When it got to the bottom it became snagged on something, and none of our efforts to dislodge it were successful. Our last-ditch attempt was to pull on the line as hard as possible; the ERGOnaut didn’t budge, and the line broke.
What we learned:
1. Make the ERGOnaut II slightly buoyant
2. Make it big enough for the circuit boards to go in edgewise (parallel to the long axis of the cylinder) rather than flat, so the status indicator lights are visible
3. Completely seal up the diver prior to the voyage and use the bluetooth link (through the acrylic cover) to verify and record the ERGO data until the moment of release.
4. Mount the weights (30 pounds seems fine) on the bottom with a line much weaker than the lift line (50-60 pound test). Make the connection between the ERGOnaut and the weights out of something that will dissolve or otherwise separate in a few hours to assure the ERGOnaut returns to the surface.
5. Never allow the diver to get close to the bottom
6. Use an entirely different kind of winch, one that’s able to hold a cable that will lift 500 pounds. The electric reel that we used on this dive was just big enough to hold 4500 feet of very thin 200-pound-test spectra line; the new winch will be sized to hold 5km of 500-pound-test stainless steel cable.
7. Try a much shallower dive to a depth that we can dive to with scuba before going to greater depths, then work our way up to 500ft, 2500ft, and finally 15,000 feet (east of the Bahamas, in the “tongue of the ocean”).
So, we’ll start building ERGOnaut II soon. It will have a longer cylindrical section to allow the boards to mount on end rather than flat, and so that it will have some positive buoyancy. We’re looking for ideas on making the connection between ERGOnaut and the weights so that the weights will automatically drop in three hours or so.
2. Make it big enough for the circuit boards to go in edgewise (parallel to the long axis of the cylinder) rather than flat, so the status indicator lights are visible
3. Completely seal up the diver prior to the voyage and use the bluetooth link (through the acrylic cover) to verify and record the ERGO data until the moment of release.
4. Mount the weights (30 pounds seems fine) on the bottom with a line much weaker than the lift line (50-60 pound test). Make the connection between the ERGOnaut and the weights out of something that will dissolve or otherwise separate in a few hours to assure the ERGOnaut returns to the surface.
5. Never allow the diver to get close to the bottom
6. Use an entirely different kind of winch, one that’s able to hold a cable that will lift 500 pounds. The electric reel that we used on this dive was just big enough to hold 4500 feet of very thin 200-pound-test spectra line; the new winch will be sized to hold 5km of 500-pound-test stainless steel cable.
7. Try a much shallower dive to a depth that we can dive to with scuba before going to greater depths, then work our way up to 500ft, 2500ft, and finally 15,000 feet (east of the Bahamas, in the “tongue of the ocean”).
So, we’ll start building ERGOnaut II soon. It will have a longer cylindrical section to allow the boards to mount on end rather than flat, and so that it will have some positive buoyancy. We’re looking for ideas on making the connection between ERGOnaut and the weights so that the weights will automatically drop in three hours or so.