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SDBs can go underwater?


Something I dimly recall but can't verify at the moment is the capability of SDBs to go underwater. I know they can hide in a gas giant's clouds, which can give a nasty surprise to any starship captain foolhardy enough to do a gas-and-go. But SDBs can also be submarines?
Any starship can be submersible, since (by definition) they are pressure sealed.

SDB's generally have *lots* of armour, so they can take a lot of pressure (the deep atmosphere pressure in a GG makes the Marianna (SP?) trench look low-pressure)

A problem that I would see with submerging starships is that most of them tend to be lighter than water (something that is offset by the stacks of armour, mentioned above) but the easy solution is to flood fuel tankage (or cargo areas) with water which should offset bouyancy nicely.

If you're looking for a Canon reference, I believe that the SDB in suplemment 7 (traders and gunboats) has the text description you're looking for.

(of course the ship needs to be streamlined...)

Scott Martin
I don't think it was ever explicity stated, but rather implicitly established that ships (those streamlined as per Scott's and Anthony's observation) are either buoyant or, possibly, subermersable.

IMTU most starships operated by small crews are. And by that I mean stuff that's under 2000 tons displacement, and even then there's some figureing involved.

Unless a ship was specifically designed for submerged operations I would think it difficult to control, even if it was sealed against outside elements.

Which segues into a point I want to bring up. Just because the interior is air tight, that is the crew living area, does not mean that the exterior is "water tight". That is to say air may not get out, and will probably circulate normally inside the ship as long as the power plant and other machinery are operationsl, but this does not mean that all the working components are sealed tight against "the elements", in this case water.

Which means that a ship that could submerge may very well damage circuits, wiring and machinery from water leaving through gaps between armor plates (if any), or other joints and fittings designed for use in outer space, but not for use beneath ocean waves.

Myself, just thinking off the top of my head, I would think making a spacecraft "submersable" would be extra. How much, I'm not sure, but I would imagine it would be less than streamlining the thing.
Well, there is a huge difference from being sealed against vacuum and being sealed against high pressure.

I don't think all starships (even streamlined) would fair well under high pressure. I think most would sink and crush. Once you get past any bouyancy issues. And as mentioned you'd probably have all kinds of other problems.

Depending on the design rule set you can figure out the bouyancy or lack of and the crush depth (I recall doing it for a few designs, in FF&S1 iirc).

However to the point, the SDB from CT is specifically noted for this ability leading me to believe it is somewhat unique in this regard. It's mentioned in the writeup in Supp 7:

"In extreme situations, they can scatter and hide, in asteroid belts, on airless worlds, and in the depths of oceans..." and other lines such as SDBs "are built to take the pressures of ocean depths and to operate wtihout problems in such environments."

As for the implication of the "deep within the... gas giant" stationing, well, how deep is deep enough? And again the SDB seems unique in this ability.
Hi !

According to MTs design sequences most space vessels have a greater density than water (e.g. a SDB is give with 5400 m³ and 11000 tons), so they are likely to sink without drive support.

While MTs Refs Companion explicitly states, that undersea is a typical hiding place, I would agree with Blue Ghost, that there are some but perhaps minor implications with that.
At least with thruster drives I see no real problem in maneuvering under water at reasonable velocities.

Leads me to a question:
With thruster or g-drive capabilities IMHO something like a hot reentry or another forced high velocity atmo crossing would not necessary.
So most starships (streamlined or not) should be able to get to a planets surface, just in a more or less fast way.
How do you explain this thing in YTU ?


I'm with BlueGhost on this one - it's a bit of a bugbear of mine. Saying that a spaceship can go underwater because it's airtight is akin to saying a car can fly because it has gullwing doors.

I brought this up on the TML a few years back and it sparked a fairly heated debate (well it is the TML) - I think in the end, the general concensus was that if ships are sealed against the impurities and dust in the highly dense atmosphere of a Gas Giant then they should be pretty well protected against water.
Also Traveller doesn't use Star-Wars style afterburners for propulsion (even though just about every Traveller ship illustration shows them) - they use 'thrust plates' which will apparently propel the ship as easily underwater as it will through atmosphere or vaccuum.

It all smacked of desperate retrofitting but if it works for you then what the hey.

This lead off into a seperate discussion. My problem really was not so much the fine details of submersible ships (I'm all for them) but the idea that canon Traveller ship designs - which were quite clearly not designed to go anywhere near liquids - were often depicted sat on or semi submerged in a body of water. So we started looking at ships that were specifically designed to do that.

I think all I actually came up with was a slightly modified streamlined hull that has an underside like a SeaKing helicopter (ie: the bottom of a boat). Also optional pontoons that could double as cargo or fuel pods. I know Tanuki (or was it Kitsune - or are they the same fella? - or was it you, Far-Trader?) had a go at drawing some up. I've still got them somewhere.

I'd link to the thread but it was so long ago it'd take me all day to find it in the archives...

If you look at canon ship pictures, they typically aren't even streamlined, even if they're supposed to be.
Originally posted by Anthony:
If you look at canon ship pictures, they typically aren't even streamlined, even if they're supposed to be.
Actually most are streamlined, streamlined doesn't necessarily imply airframe or lifting body.
One solution to the problem is that there could be SDB that have been engineered to work underwater. A more expensive option than just having submarines with Mason platforms to be sure. But, imagine a pirate High Guard refuelling off Jupiter ways and a SDB taking a pot shot from Europa and then giving chase.
Ships have always been able to scoop water from oceans etc, as well as survive indefinitely in insidious atmospheres, so I wouldn't worry about it.

Kafka has the truth of this; SDBs are engineered to operate underwater and in gas giants. Besides the specific combat rules in Invasion:Earth, there are also oodles of color text across all the versions supporting the idea.

And yes, for all the pedants out there, no ship building rules set in Traveller's long history ever presented specific costs for a "submariner/gas giant" hull and/or maneuvering packages. We'll just have to take it on faith.

Using I:E as a guide, SDBs are definitely able to submerge and hide in oceans. However, their ability to move great distances and fight underwater are still open to question. The Solomani player can place SDBs in ocean hexes, however he cannot move them while they are submerged. Also, in the case of ground attacks SDBs are greatly limited in range from their ocean placement hex.

So, liquid water seems to provide SDBs and other Traveller ships some protection from detection; there is color text in MT IIRC that mentions how deeps a vessel must submerge versus its longest dimension. As noted above, ubdersea combat operations are open to interpretation. (GT's Darkmoon briefly mentions SDB underwater combat.)

We also need to remember the text from several CT adventures. For example, there's a JTAS adventure written by John Ford (IIRC) featuring a pyramid-shaped STL space craft, Imperial researchers, and Zho troopers. In it, the Zho cutter and Imperial small craft operate easily underwater. In SotA, the players can search a gas giant for the Ancient's signal after making relatively minor modifications to their ship.

So it seems that these operations can and do take place. If you need blueprints and unit costs you're out of luck however.

Have fun,
Yea, just because something is water tight and buoyant, or at least had controllable buoyancy (either through ballast or contra grav) is a completely seperated issue from whether the ship is efficient as a sea going vessel. One doesn't imply the other. Oil platforms, for example, are sea gong vessels, and spectacularly bad at it. But they're there nonetheless.

When folks mention fuel skimming, I think folks think of things like fire fighter water bombers. But that's not what come to my mind at all.

Rather, the ship lands in the sea and parks, and then opens up the appropriate valves and starts taking in water. It's not a fly low and scoop operation. It's more like dipping.

As to the earlier question about unstreamlined craft landing in atmospheres, it's a valid point.

If a ship has, essentially, zero velocity, then its streamlining shouldn't matter. Use contra grav to slowly and gently lower the ship in to the atmosphere.

So, technically, I think it could be done. But I don't think it's practical.

The problem is simply winds, and a ship, even one with a ground velocity of 0, would have to contend with winds. For example, in the earth upper atmosphere the winds are over 200 MPH.

So, since a ship simply isn't buoyant enough to be blown along the winds like a leaf, and thus maintain 0 relative velocity to the winds, there's going to need to be some kind of streamlining I would imagine.

Now, to be fair, you'd like to think that a ship that can withstand 6gs of acceleration, regardless of configuration, should be able to withstand at least some amount of wind force.

But using the classic "big dish" antenna, I think that this is something that could withstand 6Gs of acceleration, but the wind may well produce more force than that.

So, anyway, I think it's fair to say that "no", an unstreamlined ship can not land in an atmosphere, at least without some damage to the ship. I can certainly see it being an interesting role playing event, and I would think that a ship should be able to land reasonably intact, particularly any of the major ship configurations other than Dispersed Structure, and the ship may even be able to take off again later. But it will be a slow trip, both coming in and getting off, and filled with peril.
My quick'n'dirty houserule for submersing a starship was to require an armor factor of one or better and a streamlined hull.

For a more detailed ruling perhaps the armor factor could translate into a certain number of atmospheres a ship's hull can withstand?
Black Globe; that's a nifty piece of GMing.

Everyone else; remember that a gas giant's atmosphere, though amonia (or predominantly amonia), is still an atmosphere. It's not a liquid. Even though it may have some loosely related liquid properties, it's not pressing on the ship's hull the same way a liquid like water might do.

Travelling through a jovian atmosphere, though comprised of amonia, is much different than if that ship were travelling through an ocean of Pine Sol

To add to Black Globe Generator's ruling, it may be just a simple matter of a GM adjudicating the matter; i.e. "Well, this ship has a certain history and build *yadda yadda yadda*... therefore you [the players] determine that your ship is capable of undersea travel."

Having said all that, it might be something to address in the T5 rule set.

One more thing; from what I recall of the Invasion Earth counters and rules were not patrol ships capable of total submersion? I mean in addition to SDBs I think PCs also said to have maritime operations in mind.

whartung; I think CTs rules stated that ships "skimmed" oceans to refuel; i.e. they slowed to an appropiate velocity, then touched down to the ocean, but kept on going allowing the ship's momentum and subsequent pressure from the velocity to fill the tanks.
Dear Folks -

Most people have already addressed this: canonical Trav ships are waterproof. Apart from this, you may like to rule on how waterproof they are. BG's rule that a hull with "no armor" (Striker AF 40) can withstand 1 ATM; hull with armor factor 1 can withstand 2 ATM, etc etc, is not a bad start. Remember however, that standard TL 13 basic battledress (presumably with more moving parts and thus less able to be sealed) can withstand 600 ATM...!!!

And as for underwater rules:
Originally posted by Bill Cameron:
And yes, for all the pedants out there, no ship building rules set in Traveller's long history ever presented specific costs for a "submariner/gas giant" hull and/or maneuvering packages. We'll just have to take it on faith.

So, liquid water seems to provide SDBs and other Traveller ships some protection from detection...
...there actually ARE some CT underwater rules (albiet a varient) in JTAS #22: "Seastrike", by Marcus Rowland. The article includes rules for "water as armor" and for modifying weapons so that they work underwater.

From memory (my notes are at home) there was also a Challenge article about underwater combat using MT rules. The article opened with a description of SDB's/submersibles defending a world against an invasion by Lucan's forces.

So there is some stuff out there.
Originally posted by Hyphen:
Dear Folks -

-clip-...there actually ARE some CT underwater rules (albiet a varient) in JTAS #22: "Seastrike", by Marcus Rowland. The article includes rules for "water as armor" and for modifying weapons so that they work underwater.
The weapons affects seem problematic - unless of course you're using meson guns.
First edition High Guard called all wilderness refueling "dipping".

Second edition started using "skimming" for gas giant refueling, and "dipping" for ocean refueling.

Dipping in both cases is stated as a ship landing in the water and opening the fuel cocks.
being able to submerge is one thing. dealing with long-term immersion in salt water is another. any ship not designed to deal with electrolytic and bimetallic corrosion will soon deteriorate in such an environment - in some cases, very soon.

and, any ship not designed to forcibly repel marine life will soon find itself covered with any number of marine plants and animals looking for a home. hard to fight when there's barnacles growing on the optics and abalone clogging up the missile racks and electric eels trading love buzzes with the EM sensors.