  As an initial step towards in-situ exploration of the interiors of Ocean
Worlds to search for life using cryobot architectures, we test how various
communication tethers behave under potential Europa-like stress conditions. By
freezing two types of pretensioned insulated fiber optic cables inside ice
blocks, we simulate tethers being refrozen in a probe's wake as it traverses
through an Ocean World's ice shell. Using a cryogenic biaxial apparatus, we
simulate shear motion on pre-existing faults at various velocities and
temperatures. These shear tests are used to evaluate the mechanical behavior of
ice, characterize the behavior of communication tethers, and explore their
limitations for deployment by a melt probe. We determine (a) the maximum shear
stress tethers can sustain from an ice fault, prior to failure (viable/unviable
regimes for deployment) and (b) optical tether performance for communications.
We find that these tethers are fairly robust across a range of temperature and
velocity conditions expected on Europa (T(K) = 95 to 260; velocity (m/s) = 5 x
10-7 to 3 x 10-4). However, damage to the outer jackets of the tethers and
stretching of inner fibers at the coldest temperatures tested both indicate a
need for further tether prototype development.
  Overall, these studies constrain the behavior of optical tethers for use at
Ocean Worlds, improve the ability to probe thermomechanical properties of
dynamic ice shells likely to be encountered by landed missions, and guide
future technology development for accessing the interiors of (potentially
habitable / inhabited) Ocean Worlds.
