Agreed. We don’t really know what happened on the previous attempts except that the rope first snagged and then broke. But both these failures may both be down to the fact that this massive bouy is being wound into an even more massive ship whilst both are being affected by the ocean swell. The complication is that they are not affected equally; the ship is relatively free to move, but the buoy is anchored to the seabed by both its moorings and the umbilicals.
This means that the relatively delicate thread connecting the two has to either stretch to accommodate the mismatch in movement or exert enough force to lock these two giants together.
Wire rope will stretch to some extent but as the length of rope reduces, so does the amount of stretch available to accommodate the mismatch. Consequently as the buoy is wound in the load increases as the moorings and umbilicals are lifted from the seabed, but the transient loads due to the relative movement also increase.
The solution to this engineering challenge is to build into the system some flexibility so that at least the transient loads are smoothed out. The ideal is for the winching mechanism to be able to wind and unwind so as to maintain enough tension to hoist the buoy in, but no more.
Another way is to incorporate a
spring' which will accommodate the difference in movement without exceeding the breaking stress of the rope, but thisspring’ will absorb a lot of energy as it compresses and this could be dangerous if it is accidentally released.
But both the above will result in relative movement between boat and buoy and this increases the chance of damage as the two are almost mated, so the third approach is probably the best:
Wait until it really is flat calm and only then make the attempt. Even then, it will be well worth having some flexibility in the system, this is the North Atlantic after all, so there may always be some long wavelength movement which, although not apparent to the eye, is exactly the sort of wavelength to which the AM will