It's been over 20 years since the Great Pacific Waste Spot was first discovered 04.30 The Great Pacific Garbage Patch. And it was in September last year that the very first cleaning technology was launched - System 001, a project that is mainly publicly funded by the non-profit organization The Ocean Cleanup. During the testing of System 001, nicknamed Wilson, some expectations were met. But not others.
In particular, the public was made aware of the fact that System 001 had to be towed to Hawaii for repair in January due to a structural defect. Three months later, The Ocean Cleanup published the results of a System 001 analysis and data analysis provided by the facility during a rigorous test and this forced "downtime."
As the first prototype, a team of developers and engineers led by Boyan Slate, who helped form Wilson (he got his name from fans during a lightning campaign on Twitter), released the device with some uncertainty they had to admit. Everyone knew that only sharp tests would bring accurate data.
Despite the fact that the first introduction of System 001 was preceded by a series of thorough simulations and mathematical predictions, the sharp operation in the harsh conditions in the middle of the Pacific, it was said to be polite. Namely, at the end of December, due to material fatigue, an 18-meter section broke off on one side of a 600-meter-long device. The incident forced the developer to download it immediately to the port of Hilo in Hawaii and begin repairs.
Developers have begun investigating the root cause of the break. The original predictions regarding the attachment of stabilizers were not confirmed, so they focused on dovetail joints that are welded to Wilson's main body (a tubular float made of high density polyethylene). They hold the submerged retaining walls. It was found that due to the high load in the place between the two welds holding this joint, an initial crack was formed. It then expanded further into the material until it was completely broken off. Mechanical engineers might be interested in the measured stress concentration in the "epicenter" of the fracture, which was up to 24 MPa.
Such a high stress, which was cyclically generated in the wall of the float, subsequently significantly shortened the durability of the material used. Most of the end parts of Wilson resisted higher mobility. And this was paradoxically inadvertently increased by the weight of the stabilizer frames. The combination of mainly these factors led to the breaking of the end part from the system.
Slat in the accompanying video published on the company's website and on YouTube, which expands the content of the above-mentioned analysis from the end of March, describes this defect as follows: "Although the problem of system design problems gained most of the attention of the media and the public, this was actually the clear and simple nut to do with material fatigue. Similar challenges arose in the development of the first railways or aircraft. And we are currently facing them with the first technology for cleaning the oceans. "
(Non) retention ability
"On the other hand," says Slat, "The functioning of such a system is something completely different and extremely complicated. And understanding why he failed to contain floating waste is a much more tricky problem. ”
In other words, it must have been a great disappointment for the whole team when it was observed that even though Wilson was able to accumulate plastic, he could not keep it on his (desired) concave side. And what more? The floating rubbish was seen adjacent to the outer (convex) side.
"In such a chaotic environment, you face waves, wind, currents, or various types of waves and currents. This is a huge measure of the different effects that the ocean has on the behavior of the system and the floating waste. It's a kind of huge, pool of chaos. And from such 'noise' we now have to distill some kind of signal that would show us the right direction, " adds Slat.
It is described in more detail that, for example, very little is known about the velocity profile of the "flows" of vertical winds occurring immediately above the surface or between waves. The speed of the winds at such a low position is usually not very relevant for most technologies that traverse the waters of the world's oceans. It follows, therefore, that there are virtually no relevant measurements (and data) to help adjust Wilson's mobility to floating waste. A similar situation concerns the velocity of currents in the first half meter from the water surface, where most of the plastic resides.
That is, due to the sufficiently efficient functioning of the system, it needs to be able to retain the collected waste for several weeks or months. If we imagine a situation where there could be a whole fleet of Wilsons in the Pacific (each unit will probably bear a different name), it is crucial that their retention works perfectly, because on such a large area, the actual collection of waste and their subsequent resetting will be time consuming.
Comparing the original predictive simulations and the data obtained from the sharp test, it was found that, simply described, Wilson simply could not move faster than the floating waste. In other words, the plastic is moving faster than expected. Design modifications await Wilson, which eliminates these fundamental shortcomings.
The good news
Given the turbulent conditions in Pacific waters, the U-shaped system configuration remained unchanged throughout the mission. Another positive finding was that Wilson was able to shoot and orient himself according to the wind. In order to perform its function well, it is necessary that its concave side be constantly turned in the direction of movement. Despite the above-mentioned finding that the trapped plastic tended to escape again in the vast majority, Wilson is able to collect plastic waste quite efficiently.
The protection of marine life is a priority of the project, which is also the main theme of skeptics opposing it. Marine biologists from The Ocean Cleanup and external experts confirmed that during the rigorous tests, Wilson's mission was not observed to have a negative impact on the surrounding fauna and flora.
These days, work on upgrading the design is being completed and the system is being prepared for re-launch. Wilson was given the designation System 001 / B, which demonstrates a number of modifications. Let's look at the most important ones.
Viability is key to survival in the wild conditions of the Pacific. The dovetail joints that caused the break have been completely removed and the submerged wall is moved further forward in the direction of movement. Anchoring is done using steel ropes and loops. This eliminates the need for welding along the entire length of the body. Originally heavier measuring and monitoring devices were replaced by smaller and lighter ones, which led to the complete removal of stabilizers. These two main modifications should now provide greater Wilson's resistance to the vagaries of the Pacific Ocean.
The second major problem was movement during collection. "Finding a solution to this problem turned out to be a bit tricky," says Slat. It turned out that it doesn't really matter if Wilson moves slower or faster than floating garbage. The key is to keep the movement constant. Developers will try to secure this with durable inflatable buoys. These are placed at the front in order to pull it behind you while they are driven by the wind. But the team kept Plan B up their sleeves if the buoys failed. So far, the so-called sea anchor with a diameter of 20 meters is dormant in the reserve. Which is basically an underwater "parachute" that should shoot and slow down Wilson so that the plastic has a chance to enter the capture zone.
Last but not least, the System 001 / B version is smaller and more modular. Above all, this allows modifications to be made on site without having to drag it back to shore. In the coming weeks, a team of developers is preparing to drag Wilson back to the ocean and launch a second mission.
Do you think the mission of The Ocean Cleanup makes sense? If so, and you want to help this bold plan, you can do so, for example, in the form of a monetary donation directly to them pages
In order for the system to function sufficiently efficiently, it needs to be able to retain the collected waste for several weeks or months
The protection of marine life is a priority of the project