The Europan trans-crust cable.

The Europa Clipper is the most exciting probe, so far, in the search for extraterrestrials. Some people don't seem to know why. Why not send a lander? A flyby probe in orbit of Jupiter is not very flashy, surely Europa Clipper is overrated.

Europa's crust is estimated to be 10.7 km thick. A nice submarine probe that can drop in and swim will have to burrow through that and hopefully have some range left when it gets through. 10.7 kilometers is a good estimate; but no engineer in the world would set to work without a much better estimate. They don't want to make a cable plus or minus half a kilometer. Any fraction of a meter is a big deal to those who have to make and launch it. Communication between the depths of Europa and Earth is going to require a hardline. This IMRAD is about what the tether will have to be capable of. Europa Clipper must locate an ideal place for the tether and the future probe that uses it.

In the introduction many hardships are discussed. Among those not already mentioned, faulting, tidal flexing, communication angles, cold, and thermal gradient, increasing pressure, salinity, and refreezing after melt. 

There is a lot of interesting engineering nuance in the methodology section. Fiberoptic tethers have known properties such as how they stretch and how signals degrade over distance. Detailed illustrations for each test come with. This is effectively the meat of the IMRAD and there is a lot of it. For example, if the tether is suddenly pulled on by an Europaquake, accounting for pressure and cold, will it snap? The results section is obviously the results of each of these engineering tests. I didn't read anything crazy in the results, but the images are really cool.

In the discussion the first thing to note is that the tether for sure is expected to make the ice more unstable at that point. It's safe to say now that if a failure in the ice happens near the tether, it will be at the tether. How effective the long tether communicates was a little vague, but it's safe to say a reinforced tether will outperform a minimalist tether. The tether itself can be used at a sensor, glitches in communication can infer stuff about stress and temperature, and even fault vectors along it's length.

If you stretched the tether at all, it was permanently damaged. How brittle the ice is at a given temperature will depend on salinity. I didn't see any finicky points about tether length, probably in large part because Europa Clipper hasn't told us what that length should be yet.