Small Craft - Research Submarine

[justacaveman]

Water and air are both fluids. If grav vehicles work in air, they work even more effectively in water (As long as they're waterproof, and can withstand the pressure.).

Submersibles and lighter-than-air vehicles work on the same basic premise, displace a sufficient volume of the medium you're in and you rise, increase the weight-to-volume ratio and you sink.

Depending on how gravitics is viewed by the game system it usually either provides a reactionless thrust or insulates the craft from gravity. Either way provides lift. Reactionless thrust usually provides it's own forward motion, while the insulating version needs additional drives. If you insulate yourself from gravity you also have the problem of dealing with planetary rotation etc., which is why I use the thrust model IMTU.

 

[simonh]

FWIW some of the submersible designs in Fire Fusion & Steel used contragrav, but they used it fairly unimaginatively and the designs were mostly broken anyway. e.g. subs that were so buoyant even full downward thrust wouldn't submerge them, fuel tanks half the size of the craft giving hundreds of days endurance when fuel purifiers would have made a much more compact and cheaper design with unlimited endurance, etc.

The ideal contragrav design is a vehicle that unpowered is buoyant, and uses contragrav for ubmersion and propulsion. That way on a power or drive fault it fails safe and comes to the surface. The downside of this design is that if the vehicle is lightly loaded you have to use more thrust for submersion and thus have less left over for lateral propulsion so you may want to have some ballast as well in an optimised design.

Simon Hibbs

 

[rust]

The ideal contragrav design is a vehicle that unpowered is buoyant, and uses contragrav for ubmersion and propulsion.

True, but I am not convinced that Traveller's concept of contragrav would
allow for the use of gravitics to increase the mass of an object, because
this goes far beyond shielding the object from gravitic fields or countering
such fields.

 

[Jame Rowe]

Wouldn't you still want ballast, just in case the contragrav goes out?

 

[rust]

Wouldn't you still want ballast, just in case the contragrav goes out?

Most probably, because even a submarine with a positive buoyancy that
would automatically raise to the surface in the case of a contragrav fai-
lure can have good reasons to prefer to stay submerged - just think of
a major storm and high waves at the surface.

 

[Captain Jonah]

Ok here is where it gets strange

Gravatic drives either provide thrust or can negate 90-95% of the effect of gravity on a ships weight allow it to take of and land on worlds.
So as a drive for the sub its fine. For subs much heavier than water it makes them float. How then does this help them submerge. Weird stuff coming up.

Under artificial gravity objects are under the apparent effect of levels of gravity simulating that found on worlds. Is this purely a quantum attraction at the sub molecular level or is an object inside a 5G field actually 5 times as heavy.

In theory the force used to attract an object should be equal to the apparent weight of the object and grav plate and object should have the same weight outside the field regardless of how much the object in the field seems to weigh.

What happens if the field you are making heavier is the gravity field of the planet. Since the planet is not going to come to you then you most surely will go to it.

Mounting grav plates upside down on the base of the hull set to produce a broad field rather than the more controlled ship type and use them to grab the planets own gravity field which being a product of the planets mass has an awful lot of weight behind it.

Ramp up the field and down you go, pulled towards the mass of the gravity field. Lower the power or in an emergency when your power plant fails and you rocket upwards because your ship is far less heavy that the water.

Artificial grav plates can produce (depending on version) 3-5 or as many as 10 Gs. Even if, as seems reasonable you are generating an attraction rather than actual weight the attracted object is pulled towards the grav plate far more than the grav plate is pulled towards the object.

Planet attracted to sub, sub attracted to planet. One of those two isn’t going to move much, the other will move a lot.

Rust, emergency batteries

 

[rust]

Rust, emergency batteries

Ah, I do not trust that newfangled gravitics stuff and keep the old ballast
tanks - mainly because to replace them with gravitics would doubtless in-
spire the players to come up with both prolongued discussions and evil
uses for that kind of gravitics that I failed to foresee ... :wink:

 

[Captain Jonah]

Rust, emergency batteries

Ah, I do not trust that newfangled gravitics stuff and keep the old ballast
tanks - mainly because to replace them with gravitics would doubtless in-
spire the players to come up with both prolongued discussions and evil
uses for that kind of gravitics that I failed to foresee ... :wink:

Also on a colony with limited support a good old fasioned ballast tank and pump is a lot easier to maintain than a high tech grav submergance unit.

 

[rust]

Also on a colony with limited support a good old fasioned ballast tank and pump is a lot easier to maintain than a high tech grav submergance unit.

Indeed.

"No problem, Captain. I only have to replace that little G-739/C module.
We only have to tell the crew of the freighter that comes for the ore from
the seafloor mines in four months to order one on Cassandra, and the
next ore freighter will bring it. Trust me, your sub will be back in business
in less than a year." :twisted:

 

[Captain Jonah]

Also on a colony with limited support a good old fasioned ballast tank and pump is a lot easier to maintain than a high tech grav submergance unit.

Indeed.

"No problem, Captain. I only have to replace that little G-739/C module.
We only have to tell the crew of the freighter that comes for the ore from
the seafloor mines in four months to order one on Cassandra, and the
next ore freighter will bring it. Trust me, your sub will be back in business
in less than a year." :twisted:

Or the captain of that ore ship is a true merchant and is willing to sell you one from his spares locker, at 10 times its normal price.

Well he is selling you a vital part and taking the risk he may need it later, his personal nullG bed could breakdown again

 

[AndrewW]

New adventure possibility. We need a crack commando team (one that can break out of a maximum security military prison) to cobble something together to get the sub back in operation.

Or get aboard the next ship that comes in and 'borrow' one of their's.