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copeab 09-29-2010 01:42 PM

Seaplanes & Submarines
 
I've recently been pondering a setting combining two ideas I've had for some time.

The older idea, inspired by the cargo submarine from the old Traveller adventure Research Station Gamma, was a setting that due to poor weather conditions, (large) surface ships were rare and shipping (and the military) primarily relied on submarines.

The second idea, from my love of flying boats and floatplanes (and recently resparked by watching the DVDs of Tales of the Gold Monkey), wa to have seaplanes dominate land-based aviation.

(and yes, this combination does mean aircraft-carrying subs)

I'm aiming for a pulp setting, circa 1930-1945 technology. Tje two things I think I'll have to have, at a minimum, are:

(1) No large continents but many, many small islands (this makes seaplanes sufficiently useful).

(2) Frequent and heavy storms that are a real threat to sink surface vessels. Airplanes can go around or over them, submarines under them.

Any other ideas?

sambudak 09-29-2010 03:19 PM

Re: Seaplanes & Submarines
 
The world would be fun if it was split into warring factions, and toss in some indigenous sapient that doesn't want them around, or something.

I'm not sure how submarine warfare worked in the TL you're envisioning though.

ak_aramis 09-29-2010 04:05 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by copeab (Post 1055655)
(and yes, this combination does mean aircraft-carrying subs)

The IJN had a few. I-400 class.

Quote:

Originally Posted by copeab (Post 1055655)
I'm aiming for a pulp setting, circa 1930-1945 technology.

the third thing is a power source better than the diesel-electric subs had.

A nuclear plant is probably your best bet. They could have been done with WWI era tech, if the theory had been known; no new devices were needed to do it.

Sub-to-sub warfare was typically at surface, mostly using deck guns. (Which many subs of the era did have.) Torpedoes could also be used; many were unguided, and some were wire guided.

malloyd 09-29-2010 05:14 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by ak_aramis (Post 1055778)
The IJN had a few. I-400 class.


the third thing is a power source better than the diesel-electric subs had.

A nuclear plant is probably your best bet. They could have been done with WWI era tech, if the theory had been known; no new devices were needed to do it.

Well, other than all the ones connected with getting the nuclear reaction to run and pulling the heat out of the reactor vessel.... It is true once you get on the far side of the first heat exchanger you don't need anything you didn't for a TL5 steam plant. Note that even naval reactors are fairly large, heavy pieces of technology. Using them will result in quite large submarines by TL6 standards.

But actually the diesel part isn't all that bad as a primary source, surface ships use the same technology after all and it works fine. It's the electric part - for powering the sub underwater - that's severely lacking. A lot of otherwise quite plausible technologies from jet packs to portable televisions stumble over the problem of compact energy storage, so you need to be careful of side effects when introducing magic batteries, but they'll work too.

Another alternative might be fuel cells, which historically were demonstrated before internal combustion, and are concievable enough more efficient that you could store both the fuel and oxygen to burn it with in a similar amount of tankage you'd need for just the fuel of an air burning diesel.

copeab 09-29-2010 06:16 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by sambudak (Post 1055721)
I'm not sure how submarine warfare worked in the TL you're envisioning though.

Submarines did sink other submarines in WWII, although I'm not sure if both were submerged at the time.

copeab 09-29-2010 06:23 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by ak_aramis (Post 1055778)
The IJN had a few. I-400 class.

Well familiar with it ;)

There are also the submarine cruisers, such as the Surcouf and (unbuilt) Type XI U-cruiser.

Quote:

the third thing is a power source better than the diesel-electric subs had.
As malloyd said, the battery life is the real problem. However, with snorkels a sub can run just under the surface and still use the diesel engines. Only when it has to run deeper than periscope depth does it need the batteries.

sambudak 09-29-2010 06:24 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by copeab (Post 1055889)
Submarines did sink other submarines in WWII, although I'm not sure if both were submerged at the time.

Well I'd guessed as much, but there's always some handwavium lying around to be used.

copeab 09-29-2010 06:28 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by malloyd (Post 1055848)
Another alternative might be fuel cells, which historically were demonstrated before internal combustion, and are concievable enough more efficient that you could store both the fuel and oxygen to burn it with in a similar amount of tankage you'd need for just the fuel of an air burning diesel.

There was also Hellmuth Walter' hydrogen peroxide engines.

Frost 09-29-2010 06:39 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by copeab (Post 1055898)
As malloyd said, the battery life is the real problem. However, with snorkels a sub can run just under the surface and still use the diesel engines. Only when it has to run deeper than periscope depth does it need the batteries.

Using strictly realistic technology, the snorkle working in conjunction with diesel/ electric or steam/ electric propulsion is probably going to be a major part of the solution.

Where the goal is to extend the time spent submerged or provide the submarine with a sprint capability the best bet (or least worst) is a combustion engine with an independent air supply in the form of either Hydrogen Peroxide or simple compressed air. Both approaches were tried in the period you are basing your setting off and are a great deal better than nothing despite their sometimes worrying limitations.

ak_aramis 09-29-2010 07:28 PM

Re: Seaplanes & Submarines
 
Quote:

Originally Posted by copeab (Post 1055898)
Well familiar with it ;)

There are also the submarine cruisers, such as the Surcouf and (unbuilt) Type XI U-cruiser.



As malloyd said, the battery life is the real problem. However, with snorkels a sub can run just under the surface and still use the diesel engines. Only when it has to run deeper than periscope depth does it need the batteries.

DE subs had 4 key depths noted:
Surfaced Draft
Periscope depth
Snorkel depth - the snorkel wasn't always on the periscope
Crush depth

But there's one more: weather depth. Surface weather has deeper effects than the wave height.
21. Can you feel the waves on a submarine when it's under the water?

It depends on how big the waves are at the surface and how deep is the submarine. During normal weather conditions, a submerged submarine will not rock with the motion of the waves on the surface. In fact, during even moderate storms the submarine stays perfectly level at its submerged depth while the waves crash above. In extremely violent storms like hurricanes and cyclones, wave motion can reach 400 feet or more below the surface. Though not as violent as on the surface, these large waves can cause a submarine to take 5 to 10 degree rolls.
(http://www.navy.mil/navydata/cno/n87/faq.html item 21)
http://www.seafriends.org.nz/oceano/waves.htm notes that deepwater wave depth scales to 0 at half-wavelength below midline of the surface wave. It also notes that wavelengths of 100m are not uncommon... and few subs will have 50m of even flexible snorkel... let alone the additional height needed to avoid breakers.

In a wholly ocean setting, you'll need to account for weather depth, and realize motion at depth is very roughly wave height times (Wavelength-(2*depth))/wavelength. And weather depth on such a setting are gonna be anywhere from 1m inside some archipelagos to 50m+ in deep wide ocean.

If your goal with subs is avoiding weather, then it's pretty safe to assume a need for 50m depth, plus 5m above surface, as needed for snorkel, so a safety margin of 5m for 60m snorkel, of which 10m is probably rigid.

If, instead, you go with a nuke, you can get electrolysis, don't need batteries (which were, at the time, lead-acid, heavy as heck, low energy density), and can cruise for months, or even years. And, to be honest, it's only a decade past your envisaged era.


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