So of course in September we finally launched our first ocean cleanup system from San Francisco.
We successfully deployed the system,
and then we had to wait to see what happens,
and how does the plastic interact with the system.
Very quickly what we saw was that plastic started to be caught, but then, not soon after,
we also saw that plastic was leaving the system again.
So basically, the catching and concentrating part we were able to confirm,
but then the retention part, of actually holding the catch – that’s where we saw an issue.
And then suddenly, I think it was two days before the end of the year,
a second issue was discovered.
When an 18-meter long end-section of the cleanup system disconnected from the rest of the system;
basically a fracture had occurred.
Full priority for the whole team became to analyze the results
and to understand what is truly the root cause of these issues that we saw.
And looking at the structural failure,
pretty quickly after receiving the photos of the fracture
it became clear where the origin of this fracture was.
It was right at the edge where there is an interface between two dovetails.
They're the interface between the screen and the floater.
What happened is that these sections had been welded in one-meter sections
so they weren’t extruded all the way along the pipe,
which caused there to be these tiny notches in between every dovetail section.
What happened there was that it creates this imperfection
where you get this very high concentration of stresses.
This tiny stress concentration causes this tiny crack to start.
And then this tiny crack becomes a slightly bigger crack, and then an even bigger crack,
and on the pictures you just see this propagation of the crack
all the way through the entire 1.2 meter pipe.
So, while the structural failure got most of the attention from the outside world,
this was actually the easy issue.
It's very straightforward: fatigue issues - they were here with the first railways,
they were there with the first airplanes, now they are here with the first cleanup system.
So – it is not completely new science.
Of course, applying it to this material and this environment is new,
but it is relatively well understood.
The behavior of the system on the other hand, is extremely complicated,
and simply understanding why the system was not able to retain the plastic,
that has been a much more complicated question.
And that is because it is such a chaotic environment; you have waves, winds, currents,
you have short waves, long waves, different drift forces,
you have the plastic behaving in a certain way,
you have the system behaving in a certain way, you have large-scale effects of how the ocean behaves,
you have very local effects of how the system influences
the local patterns of currents and wind and waves.
So, it is just a big pool of chaos and from all that noise you have to distill some kind of signal
that points you in the right direction.
We’re doing a drifter test at the moment,
and I am the eye in the sky, looking out for the drifters.
We started with some 27 different hypotheses,
that we thought could be responsible, or have contributed
to the cause of the system not retaining plastic.
So you start off really, really broad.
Brainstorming, making hypotheses,
maybe this is the reason, maybe this went wrong, maybe we overlooked this….
And then you start building a case,
you start collecting evidence for what you think is the hypothesis.
We have the data from the human observations,
the people that were actually out there observing the system.
We have the data from the AutoNaut, the robotic vessel that was tracking the system
and was measuring the environmental conditions.
We have the data from the system itself and the strain gauges on the system
and the cameras on the system.
We did GPS tracker tests, we did dye tests
to look at the behavior of the system relative to the water and to the plastic.
The trick is to really find those high-leverage pieces of data that increase your understanding by a lot.
One thing that was observed by each crew was that we saw plastic accumulating on the outside of Wilson
which lead us, and strengthens our hypothesis to the fact that Wilson was not fast enough,
and that plastic in certain conditions is overtaking the system.
What we see is that on one hand Wilson is going slower than we thought,
because the waves are partly shielding the system from the wind
and the wave drift force is lower than thought,
while on the other hand the plastic is actually moving faster than thought,
because of the Stokes drift effect being stronger as well as a wind shear effect of the upper water layer
causing the current for the plastic to be faster than the current that the system feels.
And then the question becomes: How to speed it up?
So many things did go well, and there were definitely no guarantees that they would go well,
so reflecting on that,
combined with now having an understanding of the things that didn’t go well,
and seeing a probable path towards solving those.
That means we are back on track and I can’t wait to have the system back out again.