How deep can you go?

[Jak Nazryth]

This has been brought up before in other forums but it was so long ago (for me) I can't remember what the consensus was.
How deep can a normal starship submerge itself under water (normal earth atmosphere) approximately 32 feet per atmosphere (sorry, I'm not sure how that translates to meters, but it's somewhere between 9 and 10 meters?
For some reason I keep thinking around 3 atmospheres was the deepest for "normal" starship hulls to safely submerge under water.
Any rules from mongoose?

 

[DFW]

This has been brought up before in other forums but it was so long ago (for me) I can't remember what the consensus was.
How deep can a normal starship submerge itself under water (normal earth atmosphere) approximately 32 feet per atmosphere (sorry, I'm not sure how that translates to meters, but it's somewhere between 9 and 10 meters?
For some reason I keep thinking around 3 atmospheres was the deepest for "normal" starship hulls to safely submerge under water.
Any rules from mongoose?

Given the strength of an unarmoured hull, it would be much deeper than most present day subs.

 

[Solomani666]

My quick and dirty rule would be:

(Hull Armor + 1) * Surface Gravity * 1000 m = Crush Depth


Note:
IMTU the outer airlock doors are armored to the same level as the hull.

Let me know if this seems about right to you.


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[GypsyComet]

Two issues here.

The first is one of overcoming a ship's tendency to float. Since MGT doesn't address the mass of ships or the differing density of water at increasing depths or in different gravities, this has to be handled with some amount of handwaving. Possibly informed handwaving, if you know older editions, but handwaving none the less.

The mathematically exuberant TNE ship building rules of 20 years ago worked out to the point where minimally space-capable hulls (ie. "no armor") would float regardless of what machinery you put in them, while any level of armor considered worthy of military service was enough to take a hull past neutral buoyancy into "sinks like a rock" densities.

Acting counter to buoyancy if you are too heavy is easy: if you have working reactionless drives, any depth is attainable, including not under water at all. A ship that uses reaction drives needs to be adapted to under water operations, possibly with a whole new drive suite. Not a terribly big deal to a ship that routinely generates MW of power, but something to keep in mind.

Getting a floaty ship to sink also requires working drives, controlled inundation of the cargo deck (to hit neutral buoyancy), or both. If you need to sink but wouldn't normally, and can't use the cargo deck as a big dive tank, I would rule that 10 meters depth per G of maneuver drive is probably acceptable, with the understanding that loss of drives means you take a quick ride to the surface...

As for the other issue, crush depth of the hull, I would point at modern submarines. Properly constructed, any starship hull can perform the needed tasks of a pressure vessel. Traveller's history suggests strongly that any ship that flies will have no trouble with surface water, and that armored hulls can hide deep.

Most civilian hulls will, per two paragraphs above, never reach crush depth without taking water on board. It is safe to assume that a streamlined ship with "no armor" can probably drop to 30 meters, while unstreamlined hulls, not built to handle gas giant dives or even normal landings, are probably going to have issues by 10 meters. Treat each level of armor as a doubling of that number. Armor-1 gets you to 60m or 20m, while Armor-2 gets you to 120m or 40m. Not much armor is needed to let an SDB set on the bottom, sensor buoys/drones on the surface, waiting for law breakers...

 

[Solomani666]

Two issues here.

The first is one of overcoming a ship's tendency to float. Since MGT doesn't address the mass of ships or the differing density of water at increasing depths or in different gravities, this has to be handled with some amount of handwaving. Possibly informed handwaving, if you know older editions, but handwaving none the less.

The mathematically exuberant TNE ship building rules of 20 years ago worked out to the point where minimally space-capable hulls (ie. "no armor") would float regardless of what machinery you put in them, while any level of armor considered worthy of military service was enough to take a hull past neutral buoyancy into "sinks like a rock" densities.

Acting counter to buoyancy if you are too heavy is easy: if you have working reactionless drives, any depth is attainable, including not under water at all. A ship that uses reaction drives needs to be adapted to under water operations, possibly with a whole new drive suite. Not a terribly big deal to a ship that routinely generates MW of power, but something to keep in mind.

Getting a floaty ship to sink also requires working drives, controlled inundation of the cargo deck (to hit neutral buoyancy), or both. If you need to sink but wouldn't normally, and can't use the cargo deck as a big dive tank, I would rule that 10 meters depth per G of maneuver drive is probably acceptable, with the understanding that loss of drives means you take a quick ride to the surface...

As for the other issue, crush depth of the hull, I would point at modern submarines. Properly constructed, any starship hull can perform the needed tasks of a pressure vessel. Traveller's history suggests strongly that any ship that flies will have no trouble with surface water, and that armored hulls can hide deep.

Most civilian hulls will, per two paragraphs above, never reach crush depth without taking water on board. It is safe to assume that a streamlined ship with "no armor" can probably drop to 30 meters, while unstreamlined hulls, not built to handle gas giant dives or even normal landings, are probably going to have issues by 10 meters. Treat each level of armor as a doubling of that number. Armor-1 gets you to 60m or 20m, while Armor-2 gets you to 120m or 40m. Not much armor is needed to let an SDB set on the bottom, sensor buoys/drones on the surface, waiting for law breakers...

Density of water at different depths?
Liquid water does not compress under normal conditions. Its density remains constant.

(This should have been my first clue not to respond to this post.)

Of course the drives will be needed to dive with any lightly armored ship unless it is stocked with a lot of really heavy cargo.

By your calculations you think that a ship that can dive into a Jovian atmosphere and withstand hard vacuum for decades with its cargo bay intact can only withstand being submerged in 40m of water? 40m is the limit for recreational diving with scuba gear! You have to be kidding me!



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[DFW]

T If you need to sink but wouldn't normally, and can't use the cargo deck as a big dive tank, I would rule that 10 meters depth per G of maneuver drive is probably acceptable, with the understanding that loss of drives means you take a quick ride to the surface...

I think that you forgot that you can fill the fuel tanks (a large % of the hull volume) with water.

 

[far-trader]

...Density of water at different depths?
Liquid water does not compress under normal conditions. Its density remains constant.

Define "normal conditions" please. Otherwise... wrong. The density of liquid water does vary in density under normal conditions. Presuming you would include Earth's oceans and seas as "normal". Temperature, salinity, and depth all contribute to varying density to degrees.

(This should have been my first clue not to respond to this post.)

Nice.

This is so ridiculous I am sorry that I even wasted the time to respond.

Not as sorry as some are that you bothered with that kind of attitude.

 

[Solomani666]

...Density of water at different depths?
Liquid water does not compress under normal conditions. Its density remains constant.

Define "normal conditions" please. Otherwise... wrong. The density of liquid water does vary in density under normal conditions. Presuming you would include Earth's oceans and seas as "normal". Temperature, salinity, and depth all contribute to varying density to degrees.

(This should have been my first clue not to respond to this post.)

Nice.

Water in liquid form does not compress or expand due to pressure like other substances until it changes state, ice, steam, plasma, etc. Liquid water density is based on temperature and the differences in density of liquid water at various temperatures is so very minuscule (with extreme emphasis) as to not be measured except in a labrotory. It is most dense at a low temperature just above freezing, but after it does freeze (becomes a solid) it actually expands 9% and becomes less dense. Without a change in temperature, water does not compress (change density) under pressure.

What I meant by liquid water does not change density under "normal conditions" was thus:
Since we are generally talking about Traveller here you could take some liquid water and drop in a singularity.
Under those circumstances I'm pretty certain the liquid water would compress assuming it stayed a liquid.
Under conditions that would not kill every nearby observer instantly, liquid water does not compress except a tiny, tiny bit during some temperature changes.


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[Captain Jonah]

Rather than add to the insults being trolled how about a few facts.

Better than 95% of earth’s oceans are less than 6,000m deep. The others are areas like the deep trenches.

The US has at least 3 deep diving units capable of 6,000m, the Russians have or had 2, the Japanese 1, not sure about others.

These are purpose built to withstand high pressure the hulls are generally of titanium with the crew compartments built as spheres to handle pressure better and other areas open to water to reduce pressure problems. The Russians use an alloy that has slightly better tensile strength.

Modern subs which are not designed specifically for deep diving can do 500m or so routinely and 700+m if pushed but that is getting close to the dangerous point.

For a traveller ship without any form of armour if it can skim fuel from a gas giant it should be able to handle the same depths as a conventional sub, IE 500m. Armoured ones with hulls of Crystaliron are not spec’d for great pressures but should be able to match the 3,000m depths of the vast bulk of deep submersibles. Superdense armour with a far harder and stronger shell and structure than mere titanium should be able to reach the depths we can currently get to with titanium spheres.
While the hulls of starships may not be built with 6,000m depths in mind a few hundred atmospheres of pressure is not going to crack or crush an armoured hull designed to take nuke hits.

Bonded super dense, well how deep is it possible to find in an ocean. An SDN with bonded super dense armour and supporting structural framework could sit on the bottom at 10,000m without problems.

In terms of moving around. Gravatic drives will allow easy movement, the only consideration being underwater which will affect accel and speed.

In terms of floating or not, If you have a working gravatic drive you can do what you want. If you want to float on the surface regardless of how heavy you are just generate enough lift to make it possible, diving works the same way. The only problem comes with just what your ships density is, a large ship that is all empty cargo bays will probably take a lot of thrust to make it dive. However since Traveller doesn’t deal with mass, just volume its probably best to wave hands and say that any ship with 1G plus can dive regardless of other considerations.

 

[Liam Devlin]

Modern subs which are not designed specifically for deep diving can do 500m or so routinely and 700+m if pushed but that is getting close to the dangerous point.

For a traveller ship without any form of armour if it can skim fuel from a gas giant it should be able to handle the same depths as a conventional sub, IE 500m. Armoured ones with hulls of Crystaliron are not spec’d for great pressures but should be able to match the 3,000m depths of the vast bulk of deep submersibles. Superdense armour with a far harder and stronger shell and structure than mere titanium should be able to reach the depths we can currently get to with titanium spheres.

While the hulls of starships may not be built with 6,000m depths in mind a few hundred atmospheres of pressure is not going to crack or crush an armoured hull designed to take nuke hits.

Bonded super dense, well how deep is it possible to find in an ocean. An SDN with bonded super dense armour and supporting structural framework could sit on the bottom at 10,000m without problems.

In terms of moving around. Gravatic drives will allow easy movement, the only consideration being underwater which will affect accel and speed.

In terms of floating or not, If you have a working gravatic drive you can do what you want. If you want to float on the surface regardless of how heavy you are just generate enough lift to make it possible, diving works the same way. The only problem comes with just what your ships density is, a large ship that is all empty cargo bays will probably take a lot of thrust to make it dive. However since Traveller doesn’t deal with mass, just volume its probably best to wave hands and say that any ship with 1G plus can dive regardless of other considerations.

I must presume Mssr Jak Nazryth, your original line of inquiry revolves around wilderness refuelling at planetary bodies of water. By asking for submergence depths, I must presume the players wish to do so without... how to put it delicately... "alert the authorities" that they're doing so.

At TL12, vehicles are triphibian, so most SDB's built at this level can withstand crushing depths of gas giants & oceans. These vessels are armored to withstand the depths and crushing pressures of both environments with ease.

IMTU-and as homebrewed rule of thumb, I use the 500m line as a universal maximum depth for unarmored Streamlined hulls; I add 1500m per point of armor, for simplicity's sake for hulls.

YMMV

PS: Salinity is an issue on water density--any submariner can tell you there's a difference between the Mediterraenean Sea and the Atlantic Ocean...

Traveller be safe & Go armed!

 

[rust]

Its density remains constant.

Mostly true for distilled water, not true for sea water, since the mineral
load influences the density - those minerals have mass, too (without be-
ing Catholic, of course). The differences are not big, usually from about
1,020 kg per cubic meter to about 1,050 kg per cubic meter.

 

[Stainless]

Looks like a rich area for a 3PP to produce an adventure/adventure seeds + background and rules all based on an underwater environment....

 

[GJD]

Gentlemen, those of you arguing over density issues are probably well aware that it's the mass of the water column pressing onto the surface of an object that exerts the pressure. Yes, the density, which varies by salinty and temprature is, of course, a factor, but not as much as the depth. Equivalent depths with differing densitys will have roughly the same pressure.

Lets not get tied up in the essentially irrelivent minutiae when we can apply those considerable intelects to answering the question in a relevant, elegant and entertaining way, eh?

My personal opinion is that for civilian, unarmored ships, the answer to how deep can they go is best expressed in the spirit of Dr, Farnsworth from Futurama: "Well, since the ship is designed to operate in somewhere between 0 and 1 atmospheres, no."

I would imagine that making a ship vaccum sealed and waterproof are two different things, and that the corrosive effect of salt water would play havoc with sensitive ship systems.

I would certainly see aquatic protection as being a hull cost multiplyer to be applied to ships that would be expecting to make frontier refuling - Type S's floating in the sea, for instance, and submersible hull even more so - Dragon's hiding in the worlds oceans , for instance.

But, of course, YTUMV.

G.

 

[DFW]

I would imagine that making a ship vaccum sealed and waterproof are two different things, and that the corrosive effect of salt water would play havoc with sensitive ship systems.

Not at all. Those ships are designed to scoop GG's at hyper-sonic speeds. There is no sensitive ship systems exposed. If a ship can only survive 0-1 atmos, you are dead the next time you skim in a GG..

 

[GypsyComet]

Of course the drives will be needed to dive with any lightly armored ship unless it is stocked with a lot of really heavy cargo.

"Of course" doesn't necessarily occur to people, so it needed stating.

By your calculations you think that a ship that can dive into a Jovian atmosphere and withstand hard vacuum for decades with its cargo bay intact can only withstand being submerged in 40m of water? 40m is the limit for recreational diving with scuba gear! You have to be kidding me!

You can have your realism, or you can have what makes for a fun game.

My assumption is that a streamlined ship with "no armor" may be built to handle the directional stresses of gas giant refueling, which will look a lot like aerodynamic stresses on an airplane, but may not have the bones to handle 360-degree multi-atmosphere invasive compression that 500m+ of submersion inflicts. By the time you even start to add armor, however, you *are* building to handle nuke pressure waves from any direction, so the crush depth of the hull is going to increase quickly. I was being conservative on the basis of adventure potential and past material. SDBs are known to lurk under oceans and deep in gas giants, both of which are suggested to be unwise for the typical civilian ship. So "no armor" is a limitation. Note also that at higher TL, you aren't buying ONE level of armor at a time, you are buying several, so crush depths will increase quite quickly.

The more strict limitations for non-streamlined hulls is based on their "vacc-only" design shortcuts. You aren't paying as much for that hull because there are things it won't do...

 

[atpollard]

Another issue to be considered is the internal atmospheric pressure of the craft. If the hull compresses and causes the internal air pressure to rise significantly above 1 atmosphere, oxygen and nitrogen toxicity will become an issue (just like it is for deep sea divers).

So the hull needs to do more than resist crushing, it needs to resist compressing the internal atmosphere (just like real submarines).

 

[DFW]

Another issue to be considered is the internal atmospheric pressure of the craft. If the hull compresses and causes the internal air pressure to rise significantly above 1 atmosphere, oxygen and nitrogen toxicity will become an issue (just like it is for deep sea divers).

So the hull needs to do more than resist crushing, it needs to resist compressing the internal atmosphere (just like real submarines).

Not an issue. Even if a ship compressed to any measurable degree, which it wouldn't, you simply remove sufficient volume of air to reserve tanks to equalize.

 

[Jak Nazryth]

THE REASON I asked if this was covered in the rules is because I got to make a character and actually got to play a character in another GM's game over the weekend. We were contracted to sit and wait for a "deep cover" operative for two weeks in the wilderness portion of a moderate population world. The deep cover agent had not checked in at his specified time and we were sent to aid him IF required. The pilot decided to hide our scout ship at the bottom of a large lake. We plan on staying submerged until we pick up a distress signal on a predetermined setting. If after two weeks we hear nothing, we return and report. If we receive the distress signal, we go in and recover him.
That spurred the question, how deep can you safely submerge a starship? nobody knew the answer.

There is a lot of real-world examples (and unfortunately insults) posted, but my specific question revolved around any existing rules covering the depth a submerged ship can go. I know of at least one classic traveller module with submerged ocean labs.. something like that, so I was hoping there was something in the game mechanics that covered it.
I used the word "atmospheres" to allow for gravity, pressure, density, etc... differences on any kind of imaginable "type" of liquid water. About 10 years ago on COTI I remember everyone arguing that since ships are designed to keep atmosphere IN instead of pressure OUT (since 99.9% starships are designed for the void of space), and since gas giant skimming only involved entering the upper atmospheres... that unless otherwise noted "normal" hulls could only dive down about 3 atmospheres of pressure. I never got involved in that discussion all those years ago but based on a couple of posts I tend to agree that the advanced "SCI-FI" hulls, and several of the 'real world' examples, a standard hull can go deeper than 3 atmospheres.

Since there appears to be nothing in the rules, here are two "simple stupid" ideas I would like comments on.
Unless specifically designed as a submersible, a standard starship can submerge based on the following.

proposed rule 1 TL + Armor rating in atmospheres of depth
proposed rule 2 half TL + Armor rating in atmospheres of depth

So or TL 12 scout with 4 points of armor can either dive down to 16 atmospheres or 10 atmospheres in depth.

Any comments?

 

[DFW]

proposed rule 1 TL + Armor rating in atmospheres of depth proposed rule 2 half TL + Armor rating in atmospheres of dept
So or TL 12 scout with 4 points of armor can either dive down to 16 atmospheres or 10 atmospheres in depth.

Any comments?

That doesn't jibe with known strength of Trav hulls. If you convert (for Earth)
atmospheres to PSI and look at explosive power needed to penetrate hull (irrelevant that water is causing the PSI) you'll find that a ship could easily sit at the bottom of an ocean trench.

 

[Solomani666]

My quick and dirty rule would be:

(Hull Armor + 1) * Surface Gravity * 1000 m = Crush Depth


Note:
IMTU the outer airlock doors are armored to the same level as the hull.

Let me know if this seems about right to you.


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After reading some of the replies, perhaps this may be more realistic:

(Hull Armor + 1) * Surface Gravity * 500 m = Crush Depth



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