Operational depth.

[Blue Ghost]

Sorry, I've asked this before, but I can't find the thread.

What is the operational depth for a starship under standard conditions?

I guess what I'm really asking is how much pressure a hull can take, which would dictate at what depth said vessel can operate on various worlds.

Loosely related, what kinds of oceans can it operate in? Liquid methane? Other aqueous solutions? Would a Type-S be able to operate under the surface of a variety of oceans? Could a type S succesfully operate in an ocean of ammonia? Mercury?

Other starship environments; would a type-S do well in a stellar nursery? What kind of temperatures can a type-S withstand before the crew started to feel toasty?

Lots of questions, I know, but I've never seen any of these really addressed in either CT nor MT publications.

 

[BlackBat242]

We've gone over and over this in multiple threads in the years I've been here, and the basic jist is that there are no rules about that, and everybody has a different idea on how deep a "normal" starship can go, whether "normal" design includes sealing to keep out higher outside pressures or just to keep air in in a vacuum, the role of armor in determining operating depth, and so on.


Make up your own rules... it'll be quicker and save you time and aggravation.

 

[steventirey1985]

THis the thread you can't find?

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[BytePro]

In the context of an adventure - whatever it needs to be (or not be)...

In the context of an 'official setting' - where not addressed, start from some basic assumptions. I.e. fuel 'skimming' implies some degree of operation in extreme environs other than vacuum... high speeds in atmos suggest some appreciable heat tolerance.

So, in the absence of rules, I'd probably go with around 30 m under earth like salt oceans or around ~4 atmo (IIRC). Denser liquids would reduce the depth, etc. Ship hulls sections could easily exceed this pressure - but not the entire ship (i.e. would be weak spots when the entire vessel is under pressure).

Slamming into the 'ground' is probably not considered good for a ship - likewise, liquids are 'incompressible' - so high speed impacts would be detrimental.

Special vessels - customized for 'deep sea' or solar studies - might be in order. I could see a ship designed to survive a stellar corona long enough to penetrate to the chromosphere or below (where temps are lower) for extended durations...

YMMV...

 

[Carlobrand]

On the one hand...

Starships are said to have a hull strength equivalent to 33 cm (a bit over a foot) of steel. That's a pretty hefty hull. WW-II era U.S. subs were a bit under an inch thick and could go down 400-450 feet safely, half again as much with some risk. Our earlier nuclear subs had 1 1/2 inch hulls and could safely manage 700 feet and had a crush depth in excess of a thousand feet(alloy and shape were better). Soviet submarine Kursk's pressure hull was two inches of - some titanium alloy, I think. On hull thickness alone, Traveller ships should be able to handle a decent depth.

On the other...

It isn't just hull thickness that you have to deal with. Modern subs achieve great depths in part by having very carefully designed hulls that distribute the forces as evenly as possible. Few starships show any consideration for that kind of precise shaping, and unless they were specifically designed for depth, they might show some unexpected weak spots that would - literally - sink them. The air lock door seal is one possible point, as are such things as the seam between a turret and the hull, wiring conduits for external sensors and antennae, etc. It would be rather unfortunate to be diving in your free trader and have an unexpected leak short out your drive or control panel while you were a thousand feet down.

So, I'd say if they weren't specifically designed for it, no more than 500-700 feet or so, being generous - which puts your ship under roughly 15-20 atmospheres. Beyond that, I'd look for leaks to start popping up in awkward and unexpected places, since the designers weren't actually designing to keep massive amounts of water out of a spaceship - and leaks under 20 atmospheres of pressure can be wickedly dangerous. Assuming they don't cause damage to the wrong equipment and sink the ship that way, the ship would be forced to surface and repair the damage, 'cause the ship's internal bulkheads - penetrated as they are by ducts and wiring, and intended to deal with at worst a 1-atmosphere pressure differential - are even less capable of holding out water under extreme pressure and could not be counted on to contain the leak to the affected compartment.

If they're an SDB or otherwise designed for high pressure, then they might manage quite a depth - modern subs can manage 2000 to 3000 feet, and their hulls are nowhere near as strong as an armored SDB.

 

[Icosahedron]

THis the thread you can't find?

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The thread linked to in that thread is the one of more interest. We never did get a definitive spreadsheet of hull design and pressure from Nick Bradbeer, did we? I wonder what happened to him?

 

[samuelvss]

I would say that military ships (including IISS) would be much stronger; as strengthening the "weak spots" of an otherwise incredibly strong hull would cost more, but be a relatively small increase in cost (compared to the cost of this massive hull).

 

[jshiggin]

So, I'd say if they weren't specifically designed for it, no more than 500-700 feet or so, being generous - which puts your ship under roughly 15-20 atmospheres. Beyond that, I'd look for leaks to start popping up in awkward and unexpected places, since the designers weren't actually designing to keep massive amounts of water out of a spaceship - and leaks under 20 atmospheres of pressure can be wickedly dangerous. Assuming they don't cause damage to the wrong equipment and sink the ship that way, the ship would be forced to surface and repair the damage, 'cause the ship's internal bulkheads - penetrated as they are by ducts and wiring, and intended to deal with at worst a 1-atmosphere pressure differential - are even less capable of holding out water under extreme pressure and could not be counted on to contain the leak to the affected compartment.

Note that a refueling run into a gas giant might very well put you into a moderately high external pressure situation, what with the ballistic run at near orbital speeds through a (largely) hydrogen atmosphere.

 

[Blue Ghost]

THis the thread you can't find?

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That's the one, Steve. Yeah, it was never resolved. I remember reading about hiding type-Ts and SDBs in oceans, and the occasional off handed comments about submersible stuff, but nothing concrete.

Hell, it's just fiction. I'll make something up.

 

[Carlobrand]

THis the thread you can't find?

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Wow! A thousand atmospheres! I never expected that. You could almost do the Marianas with that.

 

[DangerousThing]

If a ship can land on a planet with a heavy and insidious atmosphere of 10 times Earth atm, then the ship should be able to survive a *little* water.

Unfortunately water gets into high pressure quickly, and as pointed out above, subs are very carefully designed. And submariners are a special breed of people. Probably some WW 2 submarine books might help players understand what it's like to be on a small Traveller star ship.

 

[Ackehece]

think we ruled out going deep enough into a gas giant to scoop metastable metallic hydrogen. So no 500,000 atmospheres of pressure or greater.


figured I would define an upper limit

 

[Dragoner]

An armored warship would be most likely more capable that a light commercial ship, ie a Guardian versus a Free Trader.

 

[Blue Ghost]

Thanks for the responses. I'm going to try and come up with some kind of general rule for something I'm writing.