The Search for Didemnum: Day 4 (One Good Mission, and Downhill From There)

Today we were accompanied by Rachel from the Northeast Consortium (NEC), the organization responsible for funding this trip.

We decided to survey near the outflow pipe from Boston because we figured that it would be warmer and more likely to sustain didemnum.

Deployment was rough. We immediately lost the vehicle behind the stern and had it pop up near the starboard bow. That can't be good.


However, everything seemed to have survived intact, so we started our day of testing. After a few false starts, we ran a survey mission to see if the warmer water from the outflow pipe would make a difference in our images.

It did...


Whether from the pipe or from the gale force winds during the previous night,


...the turbidity in the water made for terrible image quality.


This lobster trap was one of the few recognizable objects in all our photos.


Seth had no luck finding any fish, and the sea state didn't help.


Jellyfish, on the other hand were found in abundance


throughout


the


water


column.


So


many


jellies!


We decided to haul up the vehicle to try another location. It was especially difficult with the waves being higher than they were yesterday.

Odyssey swung quite a bit while we guided it to its cradle.

That's when things got worse.

"We're all done, guys" said Seth.

"What?"


Besides the fact that the titanium thruster guard had been hit hard enough to crack one of its welds,


and the fact that the fiberglass CTD shroud had taken a beating,


it was the broken-off oil filling port in the thruster that got our attention.

We had been oeprating with slowly-leaking oil all day! Worse, we had no way to refill and re-close the hole; the show was over.


You can see the red paint that scraped off the bottom of the boat and onto our thruster.

There was no choice but to end the day early and attempt to do some emergency repairs.

Back to the lab!


On the way back to shore, John caught a bird that had found its way into the wheelhouse (miles from shore) and turned it loose outside.

Damage Report

We took a look at how our 3D-printed thruster coupling failed.

You can see in this picture that the coupling lost a big chunk on the side opposite from the direction of thrust. Basically, it cracked under the force of the thruster alone.

The amount of empty space in this printed part is clear now, and it's an open question whether the failure was related to salt or rust buildup inside these spaces.

There is mild corrosion on other parts of the thruster, about what you'd expect for 2 weeks underwater