Seaplanes & Submarines

[Hans Rancke-Madsen]

If you're going for a Traveller setting, TL5 means anything that could have been made with TL5 materials if we'd known how back in the historical period.

If you're going for an alternate (or isolated) world that has only reached TL5 and entirely by its own efforts, you still have a little leeway to imagine inventions and discoveries that could have been made but wasn't.


Hans

[malloyd]

Originally Posted by copeab

Most ocean going subs of this era (as compared to coastal subs) had a safe diving depth of around 100m or yards, which should be sufficient. Even coastal subs could usually make 75m.

Also, there's not really much need to dive below the weather. The real risks of weather are getting blown into something - not a problem when you are far from shore - or getting swamped by rolling or waves overtopping the deck - not a problem for a sealed up submarine. Getting below the wavelength might be a good idea - ships do occasionally break in half when the bow and stern are supported on wavecrests and there's no water under the middle, though it's rare - but if you can do that, you might get seasick in a hurricane, but rocking with the waves isn't actually dangerous.

[Kale]

Originally Posted by copeab

While a sub could probably launch an autogyro, recovering it would be a problem.

Give the Autogyro pontoons. It lands in the water next to the sub, and a crane brings it back aboard. This is how the Japanese subs recovered their seaplanes I believe. A lot of very early aircraft-carrying ships did this; I think some cruisers or battleships carried a seaplane early on to spot for their guns.

[Anaraxes]

both classes were faster underwater than surfaced

Yes. I'm not enough of a hydrodynamicist to know, but I'm curious as to whether fully submerged travel ought to be faster or slower, all else being equal. Under water, you've got more area wetted by a more viscous fluid, water instead of air. On the other hand, on the surface there are waves and pitching to deal with, which probably cost you forward progress.

some cruisers or battleships carried a seaplane early on

Or even "later on", if we're talking WW2 era. For instance, the USS Missouri carried seaplanes. They even trained in maneuvers to help recovery.

(The Missouri had its keel laid down in 1941; commissioned in June 1944; reached Pearl Harbor at the end of 1944, leaving for the actual fighting at the beginning of 1945. So it doesn't get a lot later than that.)

[Kale]

Nice. Thanks for the link to the seaplane recovery photo. Pretty nifty!
Here's the crane in action:
http://www.bb63vets.com/Photo.asp?id=80&b=79&n=81
Catapult:
http://www.bb63vets.com/Photo.asp?id=85&b=84

[malloyd]

Originally Posted by Anaraxes

Yes. I'm not enough of a hydrodynamicist to know, but I'm curious as to whether fully submerged travel ought to be faster or slower, all else being equal. Under water, you've got more area wetted by a more viscous fluid, water instead of air. On the other hand, on the surface there are waves and pitching to deal with, which probably cost you forward progress.

Normally the biggest factor on the surface is the energy you lose generating the wake (or if you prefer to look at it that way, in climbing your own bow wave). For conventional ship designs wave drag is usually quite a few times skin drag at high speeds, and a substantial fraction of your surface area is wetted anyway, so for the same power you would go faster submerged. But there will be exceptions - boats where there is substantial hydrodynamic lift involved (hydrofoils, anything capable of planing), boats that never try to go very fast in the first place (wave drag stays small), boats that are very light compared to their cross sections (producing a big change in wetted area if submerged) designs where there are large additional drag terms (say for water flow through the propulsion system, induced drag from that hydrodynamic lift, or towing something else through the water)....

[copeab]

It's worth noting that almost all subs through this era were really designed as surface vessels which had the ability to submerge for stealth and concealment and (hopefully) surface again afterwards.

[RogerBW]

Originally Posted by copeab

It's worth noting that almost all subs through this era were really designed as surface vessels which had the ability to submerge for stealth and concealment and (hopefully) surface again afterwards.

Absolutely. It is impossible to overestimate the influence of Albacore on later designs: it's only now that submarine-builders are even thinking of diverging from that basic hull shape.

So that's the first world-building decision, I think: do you want submarines that spend most of their time submerged, in which case you really need some sort of long-duration air-independent power plant (which at this tech level is going to be an early atomic pile), or do you want something closer to the WWII-era base in which submarines are basically attack boats designed round a gimmick? Assuming the latter, how best to get rid of land-based aircraft?

A world with a lot of small islands and no large land masses works for several reasons: severe weather systems make surface shipping untenable but allow aircraft (but not airships!) to land and be tied down in moderate shelter; minimal flat real-estate means that people don't want to give it up for runways and hangarage when they can use the sea instead. I do think you'd see more development of retractable floats for long-range and fighter aircraft than happened historically, and you might get the occasional ZLT experiment for land-based interceptors (rocket rails, etc.).

[Jonas]

Originally Posted by RogerBW

Absolutely. It is impossible to overestimate the influence of Albacore on later designs: it's only now that submarine-builders are even thinking of diverging from that basic hull shape.

The irony being people knew that such a basic hull shape was more efficient underwater since the Holland class, but was abandoned as it was much less stable when surfaced. Given the time the conventional subs of the era spent surfaced vs submerged and you can see why they changed it out.

[vicky_molokh]

This setting just must have the grandparent of this.