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Fidd · 11-01-23, 06:06 AM

73. Sea bed composition

Hitting the sea bed may, or may not, generate loud noise and/or damage "subject" to both how hard it is struck, and by the composition of the sea-bed at that locale. So soft silt or sand will create one one set of outcomes, and rock quite another. Rather than go to all the trouble of mapping it manually, if it could be done at all, I suggest a simple algorithm is used whereby the rate of change of depth away from any x/y location is used to determine the sea-bed composition. If the rate of change of depth is very small, then the sea-bed is more likely to be silt/sand, if high, then more likely to be rocky and injurious to the u-boat if it struck?

I suggest that different advantages and disadvantages be applied for impacting the sea-bed. Possibilities might be:

Rock - considerable noise to listening hydrophones on escorts, some damage to hull/u-boat hydrophones/planes/single propeller. Difficulty for asdic getting a firm fix on the u-boat.
Might lead to prolonged, but inaccurate depth-charging if under 180m depth?

Sand/silt: quieter impact, sound related to both forward and vertical speed. Possibility of damage to hydrophones, once stopped no enemy hydrophone detection possible. Asdic detection possible, but at less range than a u-boat in the water-column without the sea-bed being proximate? Of use in shallow-seas.

11-01-23, 06:06 AM	#89
Fidd XO Join Date: Apr 2005 Location: Blighty! Posts: 438 Downloads: 10 Uploads: 0	73. Sea bed composition Hitting the sea bed may, or may not, generate loud noise and/or damage "subject" to both how hard it is struck, and by the composition of the sea-bed at that locale. So soft silt or sand will create one one set of outcomes, and rock quite another. Rather than go to all the trouble of mapping it manually, if it could be done at all, I suggest a simple algorithm is used whereby the rate of change of depth away from any x/y location is used to determine the sea-bed composition. If the rate of change of depth is very small, then the sea-bed is more likely to be silt/sand, if high, then more likely to be rocky and injurious to the u-boat if it struck? I suggest that different advantages and disadvantages be applied for impacting the sea-bed. Possibilities might be: Rock - considerable noise to listening hydrophones on escorts, some damage to hull/u-boat hydrophones/planes/single propeller. Difficulty for asdic getting a firm fix on the u-boat. Might lead to prolonged, but inaccurate depth-charging if under 180m depth? Sand/silt: quieter impact, sound related to both forward and vertical speed. Possibility of damage to hydrophones, once stopped no enemy hydrophone detection possible. Asdic detection possible, but at less range than a u-boat in the water-column without the sea-bed being proximate? Of use in shallow-seas. Last edited by Fidd; 11-02-23 at 12:09 PM.