Do spaceships float on water?

[Custodian]

We already know that some ships can enter atmospheres, some of which can be both damp and dense. It is probable that these ships could deal with "wet" conditions (as stated by another poster) otherwise atmospheric conditions such as monsoons could be very problematic to such crafts.

However we don't really have to worry about whether a ship floats unless it looses power, with grav it should largely be able to adjust it's position.

However there are also dramatic considerations to bear in mind.

Only the most standard starships, and only those likely to be placed underwater (such as Scout ships), will have a known crush depth and some simply can't be guaranteed to watertight. Cue scenes from submarine movies and players checking for ex-priests with guilty consciences.

 

[PFVA63]

Hi,

Looking through some of the stuff I had once put together in a previous post on Traveller ship weights on another board using the GURPS Traveller: Interstellar Wars rules it looked like the ships in that book had the following densities;

• 2.0t /dTon for Passenger Vessels & Yachts
• 2.5t /dTon for Survey & Exploratory Vessels
• 4.0t /dTon for Merchant Ships
• 3.0-6.7t /dTon for non-Fighter Small Craft
• 7.5-13.25t /dTon for Fighters & other Military Small Craft
• 5.9-9.7t /dTon for semi-Military Vessels (like Pickets & Commerce Raiders)
• 6.0-9.0t /dTon for Military Ships
• 3.2t /dTon for a Fast Courier
• 7.4t /dTon for a Regular Courier

The densest vessel in the book is a 400 dTon SDB which comes out at 13.25t /dTon. One thing about the GT:IW Rules is that they don't require fuel for the maneuver drive or power plant; the only fuel onboard is used for jump drives. As such I guess that it shouldn't be surprising that a heavily armed SDB, without any tanks for relatively light fuel, would come out so dense. However, at a density of 13.25t /dTon it would still have about 7% of its hull out of the water.

As I noted previously though I seem to recall from "Invasion: Earth" (I think) that SDB's were supposed to be able to hide under the ocean, so that it may be that in the case of the GT:IW vessels they are able to flood some of their void spaces to reduce buoyancy enough to submerge or something.

Anyway, most of the Military vessels in the GT:IW book end up only submerging about 50-65% of their hulls and most of the freighters about 25-30% of their hulls (if I've done my calcs right).

Hope this helps.

Regards

PF

 

[rust]

Looking through some of the stuff I had once put together in a previous post on Traveller ship weights on another board using the GURPS Traveller: Interstellar Wars rules it looked like the ships in that book had the following densities ...

Thank you for the data.

They fit in very well with what I remember from my shipbuilding attempts
for my water world setting: It was quite easy to design a free trader able
to land on the sea surface and float there, even with a full cargo hold.

The only problems were the need for "floaters" (much like those of a sea-
plane) to keep the ship in the right orientation, the placement of the cargo
doors (to prevent the cargo hold from flooding) and the additional electro-
nics (active and passive sonar sensors).
My favourite design even had a "moonpool hatch" enabling the crew to en-
ter the water without using the air lock or to pick up cargo from a subma-
rine below the ship.

 

[StephenT]

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.

Unfortunately, it doesn't work like that. Try putting your hand against the back of your refrigerator at home. Does it feel cold to the touch? If it does you've got a problem, because it should be hot.

Chilling hydrogen down until it turns liquid requires pumping all the heat energy out of it, and that has to go somewhere. An underwater starship will melt ice, not create it, and in extreme cases it might even create a rising column of bubbles and the occasional grilled fish in the surrounding water. :?

(You could pump liquid hydrogen into the surrounding water, though, which might create ice. Or an explosion. )

For the record, I think that Traveller starships will need to be specially prepared for underwater operation. SDBs are purposely designed for it; scout ships are probably tough enough to cope too. Any other streamlined ship could submerge in an emergency, but it risks breaking the heat radiators, getting corrosion damage to exposed equipment, and all the non-vacuum sealed parts of the ship will be waterlogged. The landing gear will be clogged by seaweed and barnacles will start growing on the fuel intakes...

 

[GypsyComet]

Space Barnacles?

 

[walkir]

[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.

You did notice "underwater performance" on starships p.24, stating that any starship with vectored thrust reactionless thrusters (= standard M-Drives) with at least 2G, very good or better streamlining and total compartmentalization are assumed to have the equivalent of a submersible hull, didn't you?
As the stated examples (SDBs) do not have cargo space, it has to use another method then flooding. As the drives are mentioned it has to be pushing.

Edit: Corrected a bit of grammar.
And those rules do of course assume that the ship is waterproof (which is a lesser version of sealed. If it can hold air, it should be able to hold water).

 

[rust]

You did notice "underwater performance" on starships p.24 ...

Yep, but in my view this rule does not make much sense, because it
contradicts parts of GURPS Vehicles (e.g. the necessity of ballast tanks
for a submersible hull), and for my setting I needed a starship able to
remain submerged even when the maneuver drive was turned off.

 

[lastbesthope]

Just thinking, there is a difference between a spaceship floating, and being able to move/operate on or under the surface of a body of water.

LBH

 

[Sturn]

I'm no engineer, but have another wrench to throw into these arguments.

Has it been discussed in Traveller canon whether a ship's anti-gravity or contra-gravity systems can be "reversed" easily? As in instead of making the ship "lighter", with a turn of a dial they can make the ship "heavier" and thus make a floating ship sink without the need of archaic ballast tanks?

In Traveller, unless I'm way off, typical manuveur drive ships can be made to hover and float in varying gravity strengths. So, is it just straight nullifcation of gravity or is the anti-gravity field adjusted per each world's environment? If so, it should be easy to make a floating ship sink just by using the current technology on board?

Like I said, my closest technical degree might be considered "social engineering", so feel free to blast away. I could be thinking the wrong way due to density being based upon mass vs. volume, NOT weight vs. volume.

 

[ShadowDragon8685]

If gravitic drives operated by manipulating local gravity, they'd be hopeless in an environment with minimal local gravity - IE, out in interplanetary space.

As I understand it, gravitic drives operate by creating it's own gravity and making that gravity act upon the ship. Of course, this begs the question, why haven't the empires in MT simply gone with massive, oversized gravitic engines that they can use as weapons by acting them on the enemy ship - or, of course, as shields, by deflecting incoming whatevers. Enough gravity in a localized focus point, and you can deflect lasers.


In fact, that would be pretty much the basis of a Mongoose Traveller conversion based upon Schlock Mercenary...

That would be hella fun...