Titan sub might explore Kraken Mare.

[brdavis]

3 pages and the only thing that was mentioned is whether the atmosphere can "kaboom" and how to drill europa ice?

Agreed. It might be handy to read the actual proposal, which I haven't seen linked here as yet (sorry if it has and I missed it):

http://www.hou.usra.edu/meetings/lpsc2015/pdf/1259.pdf

Why choose that large fin that works as an omnidirectional antenna? Why not a directional dish?

I suspect because a phased-array antenna has the advantage of no moving parts, and a low drag penalty (compare to a dish-shaped, targetable antenna). The plan is for this to "talk" directly back to Earth, not through an intermediate like Huygens-Cassini.

Power source, 1 kw radiothermal energy…

I've not found a power listing for it, but they are planning to base it on a Stirling cycle engine which would be great (much higher efficiency than RTG's for example). Yes, they recognize that these seas are "near boiling" already, and the idea is to reject heat at the stern while running things like the sonar from the bow to avoid just those sorts of cavitation issues. It still could be interesting, given how little we know about condition there.

The paper (presentation? Extended abstract?) also mentions that buoyancy control might be tricky, as nitrogen gas would have condensation issues. So either you have to heat it (that seems possible, to me… not like you won't have waste heat) or use a non-condensing gas & piston-based system to vary buoyancy control.

Maybe the second purpose of the antenna fin is to act as radiator…

They don't mention that, but I can't think of any reason why it couldn't; phased-array systems are pretty robust, and it would likely only be used on the surface (perhaps… I guess it could[i/] be used under-ethane, as it probably doesn't block radio much, but then you'd have to worry about cavitation… not sure)

Submarine size?

They targeted a known re-entry vehicle: the X-37 as a rough estimate of a carrier. Submarine would be in the neighborhood of a ton, and 7' long by 4' high/wide or thereabouts. Not that that's (to my mind) remarkably doable. Physically it's smaller than Cassini, and not too far off Cassini's mass.

Note that the pressure hull… doesn't need much. 300 m under the surface of a lake of methane on a world with Titan's gravity is like 16 m deep on Earth's oceans… heck, my watch can survive significantly better than that, in a much nastier liquid like water. Admittedly at a different temperature, but still…

[Robotengineer]

Wouldn't the large fin-antenna be used for stability as well?

[AngelLestat]

Agreed. It might be handy to read the actual proposal, which I haven't seen linked here as yet (sorry if it has and I missed it):

http://www.hou.usra.edu/meetings/lpsc2015/pdf/1259.pdf

Thanks, that is helpful, but is kinda brief, it seems that this idea is like a pre-concept work to review if worth to be study in deeper or not.

I suspect because a phased-array antenna has the advantage of no moving parts, and a low drag penalty (compare to a dish-shaped, targetable antenna). The plan is for this to "talk" directly back to Earth, not through an intermediate like Huygens-Cassini.

Yeah, you may be right. moving parts equal to possible malfunctions.

The paper (presentation? Extended abstract?) also mentions that buoyancy control might be tricky, as nitrogen gas would have condensation issues. So either you have to heat it (that seems possible, to me… not like you won't have waste heat) or use a non-condensing gas & piston-based system to vary buoyancy control.

Yeah, is something that I never throght. I dont know if it is another gas with lower condensing temperatures.. ah yes.. hellium..

They don't mention that, but I can't think of any reason why it couldn't; phased-array systems are pretty robust, and it would likely only be used on the surface (perhaps… I guess it could[i/] be used under-ethane, as it probably doesn't block radio much, but then you'd have to worry about cavitation… not sure)

I guess they will transmit always from the surface.

They targeted a known re-entry vehicle: the X-37 as a rough estimate of a carrier. Submarine would be in the neighborhood of a ton, and 7' long by 4' high/wide or thereabouts. Not that that's (to my mind) remarkably doable. Physically it's smaller than Cassini, and not too far off Cassini's mass.

Is bigger than I imagine. It seems that they plain to "land" on the sea with that.

Note that the pressure hull… doesn't need much. 300 m under the surface of a lake of methane on a world with Titan's gravity is like 16 m deep on Earth's oceans… heck, my watch can survive significantly better than that, in a much nastier liquid like water. Admittedly at a different temperature, but still…

The most amazing about titan is that surface pressure due atmosphere is 1.5 times earth.

Wouldn't the large fin-antenna be used for stability as well?

nah is not needed, in fact it will complicate any kind of maneuver