ships & submarines
- Thread starter Dagrill
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AnotherDilbert
SOC-14 1K
Mongoose Vehicle Handbook can be used to design wet ships.
Timerover51
SOC-14 5K
The following appears as an author's note in the Cepheus Engine Vehicle Design Guides.
Hi,
I have the Mongoose Vehicle book, but I'm somewhat confused as the only example provided is a TL9 frigate with torpedoes. Can torpedoes be used against submarines?
I can't find anything about depth charges, which is what they used in the GPW.
The other problem I have is what weight of the ship (or sub) in shipping tons, is equivalent to the displacement tons? Also most ships have at least 2 figures for displacement tons and often wildly different?
I want to create a warship equivalent to the Secretary class US Coastguard Cutter for Low Tech water worlds and also some subs, with some sort of anti spaceship capability if possible.
Kind Regards
David
AnotherDilbert
SOC-14 1K
As far as I know they can now, but could not in WW1-WW2.
There was some discussion about wet ship combat, including depth charges, in Challenge magazine #53, #54, and #60 for MT. Other than that I can't remember depth charges detailed in Traveller.
As far as I understand depth charges are just free falling bombs. Since water is much better at transmitting shock than air, they do more damage at longer distance than aerial bombs. So take a bomb, increase damage and blast radius.
Displacement tons are a bit complicated in Traveller. Generally they mean the volume of 1 ton of liquid hydrogen, about 14 m³.
Wet ships generally measure weight by how much water it displaces, at about 1 m³/ton.
MgT2 Vehicle Handbook measures vehicles in Spaces, where 1 Space = 250 kg = ¹⁄₄ tonne (mass).
Shipping tons is how many spacecraft displacement tons (~14 m³) of cargo capacity it would consume to transport, i.e. how large a shipping container with the vehicle inside would be. It's not a weight, but a volume.
So the frigate on p92 is 3500 Spaces so weighs 875 tonnes (mass), but would take 1750 spacecraft displacement tons (volume, about 24500 m³) of cargo capacity to transport.
Carried aboard another vehicle it would consume 3500 Spaces.
A 3750 tonne ship would be about 15000 Spaces. TL 7-8 torpedoes would presumably be able to attack submarines.
Spacecraft weapons can be used according to p44. Perhaps such a large vehicle can dispense with the power requirement for small spacecraft weapons.
There was some discussion about wet ship combat on the Mongoose forum recently.
Thanks this is all useful stuff, I am trying to create a Navy for Thalassa in the Trojan Reach, so TL8 and rich with a massive infrastructure of 9, can easily construct whatever they like up to TL8,
Thanks for your help
David
Timerover51
SOC-14 5K
Torpedoes can be used against submarines. The US Mark 24 Torpedo, introduced in 1944, was a low-speed acoustic torpedo adequate to deal with the German VIIC and IX submarines. Current anti-submarine torpedoes use acoustic homing and are fairly small, 12.75 inch diameter, to allow for easy aircraft and helicopter carriage. The warheads are typically under 100 pounds of Torpex or an Octol-based explosive with more than twice the energy of TNT. The British have conducted a live test of a shaped-charge warhead and were amazed at the damage down to the submarine target. Look up the current US Mark 46 torpedo for more details. If you need more assistance, ask here, as there are also much larger submarine-launched anti-submarine torpedoes.
A WW2 325 pound depth charge, loaded with 225 pounds of TNT, had a lethal radius of damage against a German Type VIIC U-boat of 17 feet, with severe damage to the internal workings of the sub at twice that range. A 350 pound depth charge, loaded with 250 pounds of Torpex had a lethal radius of 22 feet against the same type of submarine. The Type VIIC had a hull crush depth of around 900 feet or so. Modern submarines are intended for deeper diving and have thicker hulls of higher strength steel or sometimes Titanium. For lethal radius, take the cube root of the weight increase in terms of TNT-equivalent for lethal radius. That is all that I can say about this.
Traveller Displacement tons are based on either 13.5 or 14 cubic meters, which means that they are 13.5 or 14 times the displacement tonnage of nautical vessels. Now, that only covers the submerged portion of the hull, and does not include the above water portion of the hull and superstructure. If you need to know the size of the ship in terms of Traveller Displacement Tons, take the length times the beam times the draft of the ship to get the underwater portion of the hull. Then add to that the length times the beam times the height of the superstructure of the vessel to get the total in Traveller Displacement tons. A
As for the actual mass of the nautical vessel, what you might be looking at is either the difference between light load and deep load displacement, or the difference between Standard Tonnage, set by the Washington Naval Treaty of 1922 and actual ship tonnage. It will depend on when the ship you are looking at was built, with those prior to and during World War 2 often quoted in terms of both Standard and actual displacement.
Are you looking at the current US Coast Guard Cutter class or the pre-World War 2 class?
Condottiere
SOC-14 5K
1. Against orbital targets, you probably want to borrow the missile, (space) torpedo and/or meson weapon systems from High Guard. It's about four spaces per tonne.
2. Surface warships are pretty much sitting ducks.
3. The better the structural strength of the submarine, the deeper it can dive, and at some point, water pressure will either crush it or the pursuing torpedo.
2. Surface warships are pretty much sitting ducks.
3. The better the structural strength of the submarine, the deeper it can dive, and at some point, water pressure will either crush it or the pursuing torpedo.
Thanks for the advice.
I'm looking at the pre-war Secretary Cutters, that were (apparently) the most successful ships in the battle of the Atlantic. They look like an ideal design for a low tech waterworld to me.
Kind Regards
David
Timerover51
SOC-14 5K
The British thought highly of the ones that they got under Lend-Lease from us. They were designed to be highly seaworthy, which in the North Atlantic means a lot.
Also, when it comes to anti-submarine weapons, do not overlook the Hedgehog, the Squid, the double Squid, and the British Limbo depthcharge mortar.
My father had a PhD thesis for which he bought a book on underwater explosions written by a naval weapons tech. The book was immediate post-WWII, and had his experiments with directed energy warheads in it- which looked VERY much like how I understand Mark48s work. Several times the effect of a conventional explosion. The tech was asking for funding on this IN the book, one presumes he got it.
