  The 'Ocean Worlds' of our Solar System are covered with ice, hence the water
is not directly accessible. Using melting probe technology is one of the
promising technological approaches to reach those scientifically interesting
water reservoirs. Melting probes basically consist of a heated melting head on
top of an elongated body that contains the scientific payload. The traditional
engineering approach to design such melting probes starts from a global energy
balance around the melting head and quantifies the power necessary to sustain a
specific melting velocity while preventing the probe from refreezing and stall
in the channel. Though this approach is sufficient to design simple melting
probes for terrestrial applications, it is too simplistic to study the probe's
performance for environmental conditions found on some of the Ocean's Worlds,
e.g. a lower value of the gravitational acceleration. This will be important,
however, when designing exploration technologies for extraterrestrial purposes.
We tackle the problem by explicitly modeling the physical processes in the thin
melt film between the probe and the underlying ice. Our model allows to study
melting regimes on bodies of different gravitational acceleration, and we
explicitly compare melting regimes on Europa, Enceladus and Mars. In addition
to that, our model allows to quantify the heat losses due to convective
transport around the melting probe. We discuss to which extent these heat
losses can be utilized to avoid the necessity of a side wall heating system to
prevent stall, and introduce the notion of the 'Critical Refreezing Length'.
Our results allow to draw important conclusions towards the design of melting
probe technology for future missions to icy bodies in our Solar System.
