Detecting things underwater?

[MasterGwydion]

Are there rules anywhere for detecting things 10km underwater from a ship that is flying above the water or in orbit?

 

[collins355]

Use a densitometer? (if your preferred Trav edition has such things - they were introduced by DGP in MegaTrav.)

 

[hopsnbaer]

I have not seen any. maybe look at the Gas Giant rules in the Companion for inspiration.

 

[MasterGwydion]

Use a densitometer? (if your preferred Trav edition has such things - they were introduced by DGP in MegaTrav.)

Do these have different ranges when used in space versus when used in an atmosphere? Or underwater? Or through several kilometers of rock? Or do I just assume that it functions out to whatever range it says and don't overthink it?

 

[hopsnbaer]

Unless it is going to be a core mechanic in your game, I would suggest not overthinking it and do what you think fits.

 

[shirgall]

Do these have different ranges when used in space versus when used in an atmosphere? Or underwater? Or through several kilometers of rock? Or do I just assume that it functions out to whatever range it says and don't overthink it?

On page 160 of the Core Rulebook (2022) it does have effectiveness and range bands for the densitometer, and it should work with liquids because it's using a planet's gravity differences to do its sensing. "Full" capability looks limited to 10km.

 

[ProfGrizzlyJon]

Absolutely. A ton of stuff in the Seastrike article in JTAS Volume 4.

"The general underwater hubbub will affect shipboard sensors only slightly, imposing DM-1 on sensor operations, but attempting to use sensors across the water/atmosphere interface presents a number of problems. Radar and similar sensors are scattered by the surface layer, making it hard to detect and track a target above the surface from underneath it and even more difficult the other way around.

The result is DM-2 on all sensor operations crossing the surface. In addition, there is DM-2 on attempts to detect a submerged vehicle or spacecraft plus the DM-1 for using sensors underwater. Thus a ship above the surface attempting to detect one beneath it suffers DM-4 on Electronics (sensors) checks and the submerged vessel suffers DM-3 to track the airborne target."

and

"Densitometers and neural activity sensors work normally underwater but are of limited combat use. NAS units may be swamped by the amount of neural activity going on in a typical body of water – fish are not smart but there may be a lot of them."

 

[Condottiere]

So much for going to school.

 

[MasterGwydion]

Absolutely. A ton of stuff in the Seastrike article in JTAS Volume 4.

"The general underwater hubbub will affect shipboard sensors only slightly, imposing DM-1 on sensor operations, but attempting to use sensors across the water/atmosphere interface presents a number of problems. Radar and similar sensors are scattered by the surface layer, making it hard to detect and track a target above the surface from underneath it and even more difficult the other way around.

The result is DM-2 on all sensor operations crossing the surface. In addition, there is DM-2 on attempts to detect a submerged vehicle or spacecraft plus the DM-1 for using sensors underwater. Thus a ship above the surface attempting to detect one beneath it suffers DM-4 on Electronics (sensors) checks and the submerged vessel suffers DM-3 to track the airborne target."

and

"Densitometers and neural activity sensors work normally underwater but are of limited combat use. NAS units may be swamped by the amount of neural activity going on in a typical body of water – fish are not smart but there may be a lot of them."

Awesome! Thank you!