The Search for Didemnum: Day 2 (Double Success, Double Failure)

On our second day out, we went a few miles further offshore to try some surveys in roughly 100 feet of water. From this far out, we could see the Boston skyline relatively clearly.


The day's first deployment went smoothly.

The goals for our second day out were to find out what altitude is best for taking pictures, and to see if Justin's changes to the survey behavior could help straighten out the tracklines when the vehicle is at depth.


In this test, we stepped through altitudes from 1.8 meters to 1.1 meters in increments of 10 centimeters. The results are exactly what we had hoped for: consistently good images, and a better idea of what range of altitudes will produce them.

Notice the difference in the amount of red channel as the vehicle approaches the bottom. To get good information from red light, we have to fly very close to the bottom. A difference of a few tens of centimeters makes a big difference in light quality!

We also had one flash misfire, the cause of which is unknown.

Overall, this set of images is a huge success; we can start doing image surveys in earnest now that we know the physical focus and aperture settings are in the right place.


The new survey behavior also worked well... mostly. The tracklines are much straighter, but what happened at the 4th corner?

Before we could wonder too much, Justin noticed that the vehicle was running in circles under remote control and had a problem with rolling over.

Uh oh.


Mike and Seth sprang into action to check it out.


Both thruster cables were still attached. So, we decided that recovering Odyssey would be the only way to fully determine the cause of the problem. Kyle got to try his hand at recovery.


Once the vehicle was on deck, the problem was fairly evident. We had lost one of the ninja pins that holds the thruster in proper orientation on the RTU shaft, and the thruster had worked its way to the opposite direction.

Only 3/4" of the thruster was still within the coupling. Had it worked its way fully loose, we would have lost it permanently!

Unfortunately, there was a second problem as well: the RTU had fallen out of alignment, and was unable to produce adequate torque on the shaft to properly position the thrusters. This is a game ender; we have to take the RTU back to the lab for disassembly.


Catching a dogfish lifted our spirits somewhat. We threw it back.


On the steam back to the harbor, I was able to put together a small mosaic of a few good images using the hugin panorama stitcher (not to be confused with the Hugin AUV).

When the RTU is fixed, we should be in very good shape to get more like this!

Battery Scare in the 11th Hour!

While we were re-installing the battery into its glass sphere (after replacing the under-performing cell #10), there was a soft pop, a crackle, and then a hiss as clouds of tan smoke filling the air.

Some part of the battery had short circuited; something was seriously wrong!

We had to take the battery apart again to see what happened and to try and fix it. We are especially under the gun to fix this, because we are supposed to deploy on Monday to look for didemnum! Yikes!


The source of the crackle became apparent; it was the sound of a wire sparking and melting itself out of its jacket. You can see the bits of melted black jacket on the red wire.


There were some burn marks on the outside of the battery too.


But, the real damage was on the corner of the cell where the smoke forced its way out.

We count ourselves very lucky that only one supercell was damaged and that nothing caught on fire. In the end, we had to use the supercell that had been removed as the replacement for the one that was damaged (although we recharged it). A net gain in the end, but only a small gain.

Nantucket Sound Testing, Day 2

In the morning, the crane operator moved Odyssey onto the boat -- it was a matter of minutes. Life is easy with a giant crane truck.


The crane on the boat was also really convenient for putting Odyssey in the water.


Taking the vehicle out of the water was also fairly painless, which is good because we had to do this a few times while adjusting the trim.



Mike operates the crane, Mike and Seth fend the vehicle off of the gunwales, and Noah guides both the crane and the quick release. We're still getting the hang of this part.


Noah is about to pop the quick release.


As the vehicle pops free, we have to work to keep it off the side of the boat while Justin takes the controls.


We do a good bit of manual control to maneuver the vehicle in tight situations, and to get it set up for missions. This will get a little easier as we get the control system and behaviors set up.


While Justin and I work on some simple missions to test the control system (goal: good yaw control without vertical stabilizing fins), Seth tests whether fish are attracted to bits of hot dog.


Then something familiar happens...

The vehicle starts going in circles when it should be going straight. Have we lost a thruster again? Seaweed? Mike and Seth check it out in the zodiac... apparently the cable got wrapped around the thruster and had disconnected.


So, Seth grabbed a handful of zip ties and went to secure the cable.


Unfortunately, the thruster cable had been damaged internally... so the day was over early. Meanwhile, Mike Ryan and Noah had upgraded the refrigerator on board to a model with a freezer. We debated putting an outboard on it and having a boat race.


But the day wasn't a total loss! Seth caught a fish with the hot dog after all, which he filleted and stuck in the new refrigerator. Possibly for lunch tomorrow!

Disaster Strikes!

Our 3-D printed mechanical fuse for the RTU coupling cracked and broke, taking our thruster to the bottom of Gloucester harbor.

Justin: Mike, the vehicle is going in circles instead of forward. Can you check the connection to the thruster?
Mike: Sure.
(Pause)
Mike: What thruster?

It would have ordinarily been retained by the electrical cable but ... we had just set it up to unplug rather than put strain on the other cable. "Whoops" doesn't quite capture the disappointment.

There's Your Problem...

This image fails to accurately capture the cause of our non-functioning camera: the grey and purple wires being crushed in the threads of the housing.

Since this was largely the result of wires and plugs being crowded near the top of the bottle, I drilled a hole in the mounting plate for the PC boards and routed some of the wires to the back side.

Dead Battery

Our battery has failed.

After 3 years of faithful service, our battery was accidentally allowed drain far below the acceptable minimum voltage for Li-ion cells, effectively ruining its capacity. In fact, it would be unsafe to recharge this battery in its present under-voltage state.

We will have to build a new battery. This is unfortunate, but since these cells lose 20% of their capacity per year in perfect storage conditions, it was inevitable.

This will push our schedule back a bit...