[bumby]

>You can put an arbitrary amount of cable in a given hole diameter by making the spool taller.

Wouldn't this be limited to the tensile strength of the material and the weight of the cable? Granted, Europa has much less gravity, but 25km is a lot of cable weight.

Consider something as small as fishing line; one online estimate gives it .245g/m. At 25km, that's over 3 tons of line weight hanging down a hole on Earth or nearly 800 lbs on Europa.

[potato3732842]

The probe bears on the ice below it and the cable gets held by the ice that's re-frozen above the hole.

What you have to worry about is the ice shifting and severing the cable.

[bumby]

I think there are still mechanics at play that would have to be considered.

>The probe bears on the ice below it

This implies it is bearing the weight of the entire cable above it. So instead of the tensile stress being the limiting factor, it's not the compressive stress. If you're intent is to retract the spool, it would still be in tensile stress as it comes up. (And you'd need enough torque to do so. But maybe you the plan would be to abandon in place).

>What you have to worry about is the ice shifting and severing the cable.

I agree, that's a pretty big concern.

[russfink]

Could you embed a series of metallic needles as you melted your way down, then communicate via radio waves that travel needle to needle? They would not need to be connected. Just close by.