Starships Underwater
- Thread starter Mithras
- Start date
ShawnDriscoll
Cosmic Mongoose
I'm guessing you found this one already. http://forum.mongoosepublishing.com/viewtopic.php?f=89&t=48778
It has actually been discussed in several threads, but right now I amMithras said:
also unable to find one of them.
Looking at my own notes on what is called "aquafitting" in my water
world settings, a plausible starship designed for underwater opera-
tions needs ballast tanks, airlocks/wetlocks capable to handle water
instead of air, underwater sensors (basically sonar, as not much el-
se works well underwater), underwater communicators (also sonar),
an underwater auxiliary drive (preferably a hydrojet drive) and a
pressure hull able to withstand the pressure in the starship's inten-
ded operation depth.
Much of this can be handwaved away, resulting in the concept that
average Traveller starships are able to operate down to a depth of
about 200 meters, but in my experience the devil is here in the de-
tails once more, and during underwater adventures with unmodified
starships the players often encounter plausibility problems. Besides,
a ship purpose built for underwater operations just adds more "co-
lour" to a setting.
alex_greene
Guest
If the ship's capable of handling plunging into a gas giant's upper atmosphere to refuel, a little water's not going to be a great problem for it.
A gas giant's upper atmosphere is much less dense and so alsoalex_greene said:
much less heavy than water, and therefore produces much less
pressure at the same depth, and so a starship's crush depth in
a gas giants's upper atmosphere is significantly different from
the crush depth it would have underwater.
The space shuttle can work in space and fly through atmosphere, but that doesn't necesarily mean it'd work well underwater 
.
Plus, they're opposite design goals - underwater, you're trying to keep the hull pressurised against massive pressures outside and don't want what's outside coming in (plus, there's buoyancy to worry about). In space, you're trying to keep the hull pressurised against zero pressure outside and are trying to keep the inside from leaking out. Granted, there is a lot of similarity in the solution (i.e. airtight seals, thick hull etc) but they still require different approaches.
.Plus, they're opposite design goals - underwater, you're trying to keep the hull pressurised against massive pressures outside and don't want what's outside coming in (plus, there's buoyancy to worry about). In space, you're trying to keep the hull pressurised against zero pressure outside and are trying to keep the inside from leaking out. Granted, there is a lot of similarity in the solution (i.e. airtight seals, thick hull etc) but they still require different approaches.
ShawnDriscoll
Cosmic Mongoose
I want to see a helicopter also be a submarine like in AI. Or a flying sub like in Voyage to the Bottom of the Sea TV show.
This would require an extremely strong but light weight materialShawnDriscoll said:
for the pressure hull and/or an extremely powerful engine, other-
wise it would not be a major problem. If I had to come up with
the technobabble for this one, I would use something like modi-
fied chitin for the hull and eliminate the ballast tanks by using
deep flight technology for underwater movement (the sub "flies"
up and down without changing its flotation, like a shark, which
has no swim bladder).
There may be less constant pressure but keep in mind a gas giant's atmo isn't nearly as sedate as being underwater at depth. For example, on Jupiter, the wind velocity ranges from a minimum of 150mph to over 400mph. A ship's structure will need to deal with this stress as well so the comparison isn't quite so simple.rust said:
ShawnDriscoll
Cosmic Mongoose
An gravity always wins near Jupiter.
These winds produce much less structural stress than a reentrySSWarlock said:
from orbit at a speed of considerably more than 400 mph, and
this is a routine operation for streamlined Traveller starships.
Besides, a wind hits the ship only from one side, and the ship
can and usually does reduce the impact by being moved in the
wind's direction (= being blown off course), while the pressure
underwater hits the ship equally from all sides, from above and
from below, and cannot be reduced or evaded.
Yep, although it depends somewhat on the concept of thelocarno24 said:
gravitics available in the game, not all of the different des-
criptions I have seen for Traveller gravitics would comple-
tely solve the problem. An example would be diving with
a starship, where it is not clear whether gravitics can only
reduce or also increase a ship's apparent weight. Since gra-
vitics are pure fiction, the details of their effects depend on
the author of the Traveller supplement in question, and it
seems the authors had a consistency failure. :shock:
alex_greene
Guest
Not everybody has access to every Traveller book already written. And not everybody who writes Traveller material knows about this forum or CotI. So there's a lot of reinventing the wheel going on, because there's no official stance on what gravitics can and can't do, as such.rust said:
It's a technomagical handwavium to allow non-aerodynamic objects to fly and hover with no visible means of support; it's conveniently been brought forward to TL8, along with Jump drive at TL9, even though technically grav and FTL could easily belong up there with the TL 18 "sufficiently advanced technology."
My thought would be to add a High Guard hull "Amphibious" modification to a vessel to allow it to operate underwater to a few hundred metres in freshwater or saltwater, and a more expensive modification to allow the ship to operate freely to deep ocean - operating depths measured in kilometres. Just rule that the modifications require extra cost - I dunno, something like MCr 0.1 per ton of hull / MCr 0.25 per ton of hull for the deep sea modification - without requiring added mass.
alex_greene said:
I'm pretty sure I didn't. :|
Oh, this wasn't intended to open a can of worms. Merely that if grav technology can allow unaerodynamic kilotonne or megatonne bank vaults to fly, making them float is kind of child's play.
I doubt there are many issues with ballast, either. Once you start dealing with TL12+ exotic armour alloys, I doubt achieving negative bouyancy is ever going to be a problem....
Sounds about right. 'Amphibious' should be essentially free - a ship must logically be environment-sealed and able to resist an atmosphere of pressure differential for extended periods of time (admittedly normally in the other direction!) or it'd be a pretty poor spaceship. It's probably the drives, sensors and the fitment of 'wet' airlocks that are probably the most important elements.
'Deepwater' mods are going to be more relevant but even so probably aren't too big a deal; it essentially comes down to strength of crush depth, so your main defence is the structural strength of starship armour. I'd be tempted to produce an equivalent table of depth-to-pressure-to-damage like in Secrets of the Ancients.
