Do spaceships float on water?

[5h4ne]

Do spaceships float on water?

I'm just fleshing out the details of a scenario based on a Hydro 9 world (mostly water) - the PCs will need to travel across the surface. They'll be landed at the starport for repairs.

However, I wonder if it is possible for a standard Traveller players' ship. such as a scout or free trader, to physically float on the ocean without requiring much in the way of power/ pilot.

I can always get the players to travel in naval ships/ boats etc. The TL of the world is A (10).

Cheers

 

[rust]

Do spaceships float on water?

Yes, unfortunately they do.

My last setting was a water world, and I spent quite some time trying to
design a starship able to dive with GURPS Traveller Starships and GURPS
Vehicles, but in the end I had to turn the idea around and design a space-
going submarine, simply because all starships I designed had flotation ra-
tings that were too high to enable them to dive without flooding the cargo
holds.

 

[GypsyComet]

The easy solution is that "unarmored" ships float, and armored ones do not, as the armor tips a ship over the density that allows it to float on water. You could even set a particular level of armor as establishing neutral bouyancy.

Slightly more complex but still within Mongoose Traveller's reach would be to cross-index armor with the percentage of the ship that is high density, leading to high-performance but unarmored ships sinking, while low-performance ships that are all cargo might still sink due to being armored. As high performance also tends to mean "a lot of fuel", I'm not sure this is a useful scale, but it might be worth a look.

If you simply must know the hard numbers, either dig up a copy of MT's "Referee's Handbook" or TNE's "Fire, Fusion & Steel", or make it up. The typical assumption is that engineering spaces and armor are considerably denser than water, while fuel and cargo spaces are considerably less dense than water, and living spaces are a bit less dense on average.

 

[kristof65]

Short answer: Depends.

It depends on the ships weight versus it's shape, the density of the ocean and the amount of water the ship displaces.

There are entire engineering fields built around this.

Some designs are more likely to float than others, because of their shape.

 

[GypsyComet]

Shape and mass distribution are a much more complicated issue, certainly. Knowing that a ship will float is relatively easy by comparison. The trick is figuring out what parts end up above water.

This is why the magic of anti-grav is so common as an assumed technology. With anti-grav the ship floats at the level required by plot.

 

[PFVA63]

Hi,

As others have noted there are a lot of things to consider, but based on past similar discussions, as well as some limited stuff from previous cano sources, I think alot of people tend to assume that most vessels (especially those with big cargo and/orfuel tanks) will typically float, while heavily armed and armored vessels may or may not (especially System Defense Boat type vessels which have relatively small fuel tanks - due to their lackof jump drives).

In the old boardgame "Invasion Earth" which is set in the Traveller Universe, specifically, I think thatthere is a reference to some SDBs hiding underwater.

Additionally, some other Traveller rulesets, such as GURPS Traveller: Interstellar Wars have specific rules for calculating a ships mass in addition to volume, and based on thoe rules most ships float, with system defense type vessels being close to being nuetrally buoyant.

Hope this heps.

Regards

PF

 

[zanwot]

You seem to want starships that float, so your initial question is answered as by default they seem to float.

However I see to ways to make a starship sink on purpose:
* As Rust mentionned, flood the cargo hold: Open the cargo hold on a trader ship and use it as a ballast, though you could then be stuck sinking. I am pretty sure with an advanced air lock and life support you could even manage to pump in and out the needed air to get neutral bouyancy, just like a submarine, but that may require creative engeneering.
* Depending in how you interpret Traveller thrusters, and more specifically how ships manage vertical take off, you could simply *push* yourself down into the water with the same vertical thrust. So long as you manage to submerge the craft entirely you then can go essentially as deep as you want (the force pushing you up stays essentially constant with depth) and get neutral bouyancy, so long as you keep on *pushing down* and the hull resists the pressure (another issue alltogether). Of course how much thrust is needed to submerge a ship needs to be calculated, and will depend on how dense it is of course. My guess is with a 1 G thrust civilian ship you will not go far with this, but with any military ship (dense and high thrust) you should be able to do whatever you want.

 

[GypsyComet]

I think thatthere is a reference to some SDBs hiding underwater.

Early issue of JTAS mentions SDB hiding underwater, in gas giants, and various other places.

This leads back to the arguments on sensor rules, of course, but the general idea is that hiding in spots that require specific and time consuming sensor sweeps is worth doing since invading ships may not have the time or attention to find you until you have sent a flight of missiles up their tailpipes.

Under some rule sets a ship keeping artificial gravity on is basically broadcasting its location to anyone with densitometers. This is a bit too Star Trek for me, but it does lead to ships like SDBs needing to keep station underwater without having AG going, which means they have to be dense enough to stay down.

Add this to art in MT (the cover of the Ref's Companion, among others) that shows Scout ships floating, and it becomes apparent that ships as a whole straddle the bouyant threshold of density.

 

[kristof65]

This is why the magic of anti-grav is so common as an assumed technology. With anti-grav the ship floats at the level required by plot.

From a GMs standpoint, unless there is a good reason not to - IE, total systems failure, I would just assume the anti-grav allows the pilot to set it to "float" as he/she wants it to as well.

Otherwise, even if most ships float, you end up with another issue - at what orientation do they float?

FREX, a Type S scout ship might float with the nose/bow pointing down, based on it's weight distribution (or not - I do know that an empty container with the same shape would float nose down - not sure what the weight distribution inside the Type S would do to change things)

 

[phild]

so long as you keep on *pushing down* and the hull resists the pressure (another issue alltogether).

At what depth is this going to be a problem? I'd assume that ship hulls can take a reasonable amount of pressure from the strains of 6G acceleration (there's no greater hull cost for fast ships), from gas giant skimming and from whatever other structural challenges deep spaces lends. But I wouldn't know how quickly pressure increases under-water. So an interesting (using the term entirely subjectively) challenge for someone:

1. What are the implications for depth, pressure and starship hulls in a standard H20 ocean?

2. How would this vary on a liquid methane, mercury, liquid hydrogen or other exotic fluid ocean?

 

[rust]

I'd assume that ship hulls can take a reasonable amount of pressure from the strains of 6G acceleration (there's no greater hull cost for fast ships), from gas giant skimming and from whatever other structural challenges deep spaces lends.

This is a bit complicated, because starship hulls are built for "high pres-
sure inside, low pressure outside", while under water the situation is re-
versed, with "low pressure inside, high pressure outside".

As a rule of thumb, the pressure under water increases by approximate-
ly 1 atmosphere per 10 meters of depth, so at a depth of 100 meters
the pressure would be 10 atmospheres - ten times the pressure at the
surface level.

GURPS has rather detailed rules for calculating the "crush depth" of ve-
hicles, the depth at which the water pressure would be high enough to
destroy the vehicle.

On other worlds and in oceans made of other fluids several factors would
influence the pressure, for example the local gravity and the density of
the fluid.

 

[Stainless]

C'mon guys. The game is 100% fiction. It's made up. If you want your starship to float, then let it float. Use whatever handwavium your enquiring players require. The game is stuffed full of delicious hanwavium after all. Get on with the game (aka plot) and have fun! Honestly, some people think too much :roll:

 

[EDG]

Honestly, some people think too much :roll:

Or maybe some people think too little.

If people want to worry about this sort of thing, what skin is it off your nose? It's not getting in the way of your game is it?

 

[GypsyComet]

We're now wandering off into a completely different OTA*.

Starship hulls in Traveller are, by nature, built to resist inward pressure as well as outward. The act of landing, skimming a gas giant, or taking a near-miss from a missile in a fight are all inward pressure situations, and a hull that can't handle them at shock attack levels won't stay spaceworthy for long. Heck, landing on a Size A world stands a chance of producing a 1 ATM inward pressure, and getting there caused more than that on the hull.

And again, we have official Traveller art that shows ships floating in water.

So. The question is not whether a ship can handle inward pressures, but more "how much?"

This answer can be informed by prior editions, but it is probably best to frame it in a way that is self-contained within MGT. Is it the same for all? Is is armor based? Streamlining based? A combination?


* - Old Traveller Argument

 

[5h4ne]

Well, as the original question asker, I'm happy with all the info given!

I'm not very technically minded but as I was going through the framework of the scenario I'm gonna run at a con, I thought it would affect the flow of it and the finale if the players had access to their ship or not. So it's all story based.

I run other games, but with Traveller I kind of like to get the tech sounding a little bit realistic and I know some of my players aren't tech ignorant artists like me

In the end, I've plumped for the ship being able to float and the players being able to get off and explore the islands and arcipelagos easily enough.

The world in question is Violante btw. This is the first Traveller scenario I've written - I've only run two before that were published adventures.

Cheers.

 

[rust]

C'mon guys. The game is 100% fiction. It's made up.

If it were 100 % fiction, you could have stars orbiting planets, space figh-
ter weapons destroying entire battlefleets with a single shot, beginning
characters with an average skill level of 75, and so on. :lol:

The question is not whether a ship can handle inward pressures, but more "how much?"

This answer can be informed by prior editions, but it is probably best to frame it in a way that is self-contained within MGT. Is it the same for all? Is is armor based? Streamlining based? A combination?

The GURPS formula I mentioned uses:
- the structural frame type (extra-light to extra-heavy) of the vehicle,
- the armour strength of the vehicle (which also includes the material
used),
- whether the vehicle has a submersible hull (one specifically designed
to withstand high inward pressure).

 

[GypsyComet]

The GURPS formula I mentioned uses:
- the structural frame type (extra-light to extra-heavy) of the vehicle,
- the armour strength of the vehicle (which also includes the material
used),
- whether the vehicle has a submersible hull (one specifically designed
to withstand high inward pressure).

Step three is outside the MGT experience for now, but may come up once we have vehicle construction rules.

Steps one and two have answers within the Core MGT book and High Guard.

Easiest is to take the actual armor value (which already has effects of TL/material incorporated) and factor it against the presence or absence of additional Structure (from HG). The "submersible hull" question should be assumed to be in play and defaulted to yes or no, so the later addition of such an option can be factored backwards should someone want to.

If there is ugly math, make it all into a table instead.

 

[rust]

If there is ugly math, make it all into a table instead.

I think the math would be quite simple, and if we were still using our
Pharos IV water world setting, I would try to write, test and post a
formula, but since our current Enki II setting is a desert world ...

 

[Jeff Hopper]

Anyone ever given thought to starships creating their own icebergs?

This just came to me, so ignore it if you like. We've got a starship, with fuel tanks loaded with liquid hydrogen, sitting in an ocean. Now, even with superscience insulation on those tanks, the hull would probably still get cold. So wouldn't there be a possibility of ice forming around the fuel tank areas of a ship?

(Yeah, there are a lot of other things involved. Salinity of the seawater. Temperature of the seawater. )

Now, even if you want to declare that this isn't an issue as a referee (its your game, after all), there still might be situations where this ice-forming problem could occur.

Just an odd thought to mull over.

 

[Dave Chase]

First, make sure that keep seperate between whether a space craft/ship can float and whether it is water proof.

They are not the same.

Secondly, T5 (Marc Miller) is/has addressed this somewhat. You have to pay for/design the craft/ship to be work in liquid enviroments

It uses the terms

Flotation Hull. Sealed to protect against prolonged water or fluid exposure.

Submergence Hull.
Hull is sealed to protect against prolonged water or fluid exposure. Includes ability to submerge and resurface.

And you need either one (or both) to do landings and takeoffs from liquid.

Currently no formulas are presented, its more of a design feature to include at the building of the ship. (Ie, no reto fitting at this time allowed.)

Dave Chase