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Never occurred to me that torpedoes can be battery powered. Any idea what kind of cells they have? I got confused by the dual units here: > 65cm torpedoes hav

by tra3 7y ago

Never occurred to me that torpedoes can be battery powered. Any idea what kind of cells they have? I got confused by the dual units here: > 65cm torpedoes have enough fuel to travel in excess of 100 kilometers at 50 knots for just over an hour. Turns out 1 knot/hr is nearly 2km/h so that checks out. Weird nautical units.

extrapickles 7y ago
Probably some form of lithium primary cell as they have high energy densities and good shelf life.
- variaga 7y ago
  The article says Zinc-Oxide
jdjrirkfkfk 7y ago
From linked reference: Silver oxide-aluminium (AgO-Al) Silver oxide-zinc (AgO-Zn) Lithium-Ion (Li-Ion) Lithium-polymer Lithium-iron phosphate (LiFePO4) 1,040 Wh/kg 490 Wh/kg 600 Wh/kg 600 Wh/kg 520 Wh/kg The F21 is powered by a new generation of silver oxide-aluminium (AgO-Al) sea-water primary battery using dissolved sodium dioxide powder as electrolyte and incorporating a new electronic closed loop electrolyte circulation system. In comparison with silverzinc and other technologies, AgO-Al energy density is unrivalled. It ensures both maximum speed beyond 50 knots and endurance around 1 hour without compromising safety. TIL: A silver-oxide battery (IEC code: S) is a primary cell with a very high energy-to-weight ratio. They are available in small sizes as button cells, where the amount of silver used is minimal and not a significant contributor to the product cost.
- user5994461 7y ago
  And here we are on Hacker News with other threads on how battery density is peaking with Lithium and there is nothing better in sight. Turns out there are silver based battery that can do almost double. So what's the catch as to why it's not being adopted by phones?
  - smacktoward 7y ago
    Silver is expensive, and the Defense Department is substantially less price-conscious than the average smartphone buyer.
  - chipsa 7y ago
    They're primary batteries. Which is to say: not rechargable.
  - janekm 7y ago
    Non rechargeable phones aren't very popular, and these batteries need air so can't be easily water-proofed. Also they swell during discharge.
ken 7y ago
Knot means nautical mile per hour. It’s not a short way to say “nautical mile”.
soneil 7y ago
So fun trivia. A nautical mile is one minute of latitude (1/60th of a degree). The meter was originally 1/10,000,000th of the equator to the north pole. So I'd argue the nautical mile was more logical than the statute mile, in this respect. This is also why you can rough 1knot:2km; you're dividing those 10,000,000 old-world-meters by 5400 (90°*60').
- dylan604 7y ago
  If you use a 7200rpm hard drive does the math work out differently? I always forget the definition of the nautical distance. Thanks for the reminder. There's also the knot in a rope every certain distance that would get counted against a stop watch to see how fast the ship was moving.
AtlasBarfed 7y ago
Well, they don't need to be rechargable...
bregma 7y ago
> Turns out 1 knot/hr is nearly 2km/h so that checks out. I think you meant to write 1 knot hour is nearly 2 km -- a weird way to compare distances, but hey, the math works.

by tra3 7y ago

extrapickles 7y ago

Probably some form of lithium primary cell as they have high energy densities and good shelf life.

variaga 7y ago
The article says Zinc-Oxide

jdjrirkfkfk 7y ago

From linked reference: Silver oxide-aluminium (AgO-Al) Silver oxide-zinc (AgO-Zn) Lithium-Ion (Li-Ion) Lithium-polymer Lithium-iron phosphate (LiFePO4) 1,040 Wh/kg 490 Wh/kg 600 Wh/kg 600 Wh/kg 520 Wh/kg The F21 is powered by a new generation of silver oxide-aluminium (AgO-Al) sea-water primary battery using dissolved sodium dioxide powder as electrolyte and incorporating a new electronic closed loop electrolyte circulation system. In comparison with silverzinc and other technologies, AgO-Al energy density is unrivalled. It ensures both maximum speed beyond 50 knots and endurance around 1 hour without compromising safety. TIL: A silver-oxide battery (IEC code: S) is a primary cell with a very high energy-to-weight ratio. They are available in small sizes as button cells, where the amount of silver used is minimal and not a significant contributor to the product cost.

user5994461 7y ago
And here we are on Hacker News with other threads on how battery density is peaking with Lithium and there is nothing better in sight. Turns out there are silver based battery that can do almost double. So what's the catch as to why it's not being adopted by phones?
- smacktoward 7y ago
  Silver is expensive, and the Defense Department is substantially less price-conscious than the average smartphone buyer.
- chipsa 7y ago
  They're primary batteries. Which is to say: not rechargable.
- janekm 7y ago
  Non rechargeable phones aren't very popular, and these batteries need air so can't be easily water-proofed. Also they swell during discharge.

ken 7y ago

Knot means nautical mile per hour. It’s not a short way to say “nautical mile”.

soneil 7y ago

So fun trivia. A nautical mile is one minute of latitude (1/60th of a degree). The meter was originally 1/10,000,000th of the equator to the north pole. So I'd argue the nautical mile was more logical than the statute mile, in this respect. This is also why you can rough 1knot:2km; you're dividing those 10,000,000 old-world-meters by 5400 (90°*60').

dylan604 7y ago
If you use a 7200rpm hard drive does the math work out differently? I always forget the definition of the nautical distance. Thanks for the reminder. There's also the knot in a rope every certain distance that would get counted against a stop watch to see how fast the ship was moving.

AtlasBarfed 7y ago

Well, they don't need to be rechargable...

bregma 7y ago

> Turns out 1 knot/hr is nearly 2km/h so that checks out. I think you meant to write 1 knot hour is nearly 2 km -- a weird way to compare distances, but hey, the math works.