Small Craft - Research Submarine

[rust]

For my Pandora setting I will need a deep sea research submarine. Since
I do not like the Mongoose Traveller vehicle design system, I tried to use
the rules for small craft design.

This is of course not a "real" design, it was intended to give me an appro-
ximate idea what the size and cost of such a craft could be like in Mongoo-
se Traveller terms.

The result is this here (and sorry for the unusual format):

Small Craft - Research Sub

Hull streamlined, self-sealing: 30.00 dtons / 1.73 MCr.
Armour (Titanium, 10 %): 3.00 dtons / 0.13 MCr.
Reinforced Hull (10 %): 3.00 dtons / 0.30 MCr.
Reinforced Structure (10 %): 3.00 dtons / 0.60 MCr.
Aerofins (Control Surfaces): 1.50 dtons / 0.15 MCr.

Control Cabin (3 persons): 4.50 dtons / 0.15 MCr.
Computer Model 1: ------ / 0.16 MCr.
Sensors: 2.00 dtons / 1.00 MCr.

Fusion Power Plant: 1.50 dtons / 3.50 MCr.
Reactor Fuel: 1.00 dtons / ----------
Gravitic Drive: 1.00 dtons / 2.00 MCr.

Cabin (Fresher etc.): 1.50 dtons / 0.05 MCr.
Grappling Arm: 2.00 dtons / 1.00 MCr.
Airlock: 1.00 dtons / 0.20 MCr.
Hangar (Ballast Tanks): 5.00 dtons / 1.00 MCr.

Total: 30 dtons, 11.97 MCr.

With the titanium armour, a reinforced hull and a reinforced structure the
submarine should easily be able to operate in a depth of up to 3,000 me-
ters - and this is the maximum depth of Pandora's ocean.

As you see, I have used the aerofin rules for the control surfaces, the ca-
bin rules to give the crew a fresher, the grappling arm rules for a manipu-
lator used to collect samples, and the hangar rules for the ballast tanks.

The sub has no dedicated cargo hold for the samples, because these can
be kept and transported outside of the actual submarine, they do not need
a pressurized environment.

 

[Mithras]

Now that is thinking 'outside of the box'!!

Well done.

 

[rinku]

Classy work, rust.

Are you using contra-grav in this campaign? If so, that could be an alternative to buoyancy tanks. Saves volume and simplifies hull integrity issues.

You might want to consider modest armament (missiles) or probes, too. Even if not expecting fighting, some ability to blow things up may be of use in excavation or exploration.

 

[Lord High Munchkin]

That's a very good point... a sub equipped with grav wouldn't really need ballast tanks.

 

[rust]

Classy work, rust.

Thank you.

Are you using contra-grav in this campaign? If so, that could be an alternative to buoyancy tanks. Saves volume and simplifies hull integrity issues.

In this setting contragrav is extremely expensive, very power hungry and
bulky, so it is almost only used for starships.

You might want to consider modest armament (missiles) or probes, too. Even if not expecting fighting, some ability to blow things up may be of use in excavation or exploration.

Yep, I was thinking of microtorpedoes, probes, instrument packages and
thelike in pods mounted on the outside of the hull, because they do not
need a pressurized environment and would be easier to exchange. How-
ever, I have not yet designed anything of that kind.

 

[hdan]

Are you using contra-grav in this campaign? If so, that could be an alternative to buoyancy tanks. Saves volume and simplifies hull integrity issues.

I'm curious: How? Except in its power to be used as Handwavium, Contra-Grav would do nothing to displace water from your hull or make you more massive.

As I imagine it, CG allows you to ignore the pull of the local planet's gravity in varying amounts, so that you can "float" up (really just moving away from the planet due to reduction in centripetal force) by effectively widening your orbit and using your maneuver thrusters to gain velocity so it doesn't take you hours to reach orbit.

I suppose if you consider CG to be more like the "Mass Effect" system of controlling your inertial mass (or its interaction with the universe outside the "bubble") in either a positive or negative way, you could make your submarine appear massive enough to effectively increase "gravity"....

 

[hdan]

Huh, my last messages comes across as snarky. Not my intent, just trying to understand how CG can be used in place of ballast tanks.

 

[DFW]

I'm curious: How? Except in its power to be used as Handwavium, Contra-Grav would do nothing to displace water from your hull or make you more massive.

Hmm. Well if your craft is denser than water, contra grav would make you go from sinking to neutral buoyancy (no longer sinking). At which point any slight forward speed would enable you to surface using the diving planes.

BTW rust, IIRC most non-military subs have emergency ballast (usually a conformal "sled" made of lead attacked to the belly) that can be jettisoned in case of power failure or inability to blow water from the ballast tanks.

 

[hdan]

Hmm. Well if your craft is denser than water, contra grav would make you go from sinking to neutral buoyancy (no longer sinking).

LOL, I must be more tired than I thought; that's pretty obvious.

 

[rust]

BTW rust, IIRC most non-military subs have emergency ballast (usually a conformal "sled" made of lead attacked to the belly) that can be jettisoned in case of power failure or inability to blow water from the ballast tanks.

Thank you, a good reminder, I will add it to my list.

 

[Rikki Tikki Traveller]

I would suggest dumping the Ballast Tanks (or just making it smaller, as in a back-up system to the gravitics) and add Probe Drones (just a ton would be plenty to simulate your probe torpedoes.

I like this approach!

 

[rust]

I would suggest dumping the Ballast Tanks (or just making it smaller, as in a back-up system to the gravitics) and add Probe Drones (just a ton would be plenty to simulate your probe torpedoes.

Thank you, a good idea.

 

[Silvereye]

For my Pandora setting I will need a deep sea research submarine. Since
I do not like the Mongoose Traveller vehicle design system, I tried to use
the rules for small craft design.

Interesting idea, and it seems to work quite nicely. A couple of observations and some feedback.

The external equipment and sample storage stations and grapple arms etc. I'd actually just make it a 'modular' external cargo space so it can be easily modified depending on the mission needs. Examples might be manipulators, sensor booms, cameras, ROV hanger, sampling equipment, etc...

Also, the reactor fuel. If your tech allows it, I'd just replace most of it with fuel processing. Your vessel operates in water. You can then generate hydrogen fuel from the surroundings, and probably oxygen as a by product meaning the endurance of the vessel then becomes limited by the crew requirements.

I'd also add batteries (or fuel cell) as a back-up power supply in case of emergency.

Finally, does the submarine have to remain static "on station"? I'm guessing so as trying to collect samples or do precision work at speed is kind of hard. If not though, you can use an aerofoil to provide downforce to submerge (lift in the opposite direction) and remain submerged as long as the vessel is moving forwards and do away with the ballast tanks.

 

[rust]

Thank you very much for your feedback.

Finally, does the submarine have to remain static "on station"? I'm guessing so as trying to collect samples or do precision work at speed is kind of hard. If not though, you can use an aerofoil to provide downforce to submerge (lift in the opposite direction) and remain submerged as long as the vessel is moving forwards and do away with the ballast tanks.

If I do not misunderstand this, this would be the Deepflight concept that
is used by some of the small submersibles ?

http://deepflight.com/subs/index.htm

I was thinking of introducing a vehicle of this kind as the common, affor-
dable "underwater car" of the colonists a few years after the colony is
established, but the concept could indeed also be used for a research ve-
hicle.

 

[DFW]

Hmm. Well if your craft is denser than water, contra grav would make you go from sinking to neutral buoyancy (no longer sinking).

LOL, I must be more tired than I thought; that's pretty obvious.

Well, you can't rise solely on contra-grav. So, it isn't a total replacement for ballast.

 

[Silvereye]

If I do not misunderstand this, this would be the Deepflight concept that is used by some of the small submersibles ?

Yeah, the creations of that talented Mr Hawkes. Using a downward lift instead of ballast.

As an aside, a couple of links for you to have look at. They are kind of submarine engineering related.

Just to prove there is a very fine line between madness and genius. The Reid RFS-1. And a Stingray Drive not as efficient as a propeller, but kind of a fun concept.

 

[rust]

As an aside, a couple of links for you to have look at. They are kind of submarine engineering related.

Thank you very much for the links.

The GURPS Vehicles design system has something quite similar to the
Stingray Drive under the name of "flexibody" propulsion, and I toyed
with it during my first attempts at creating aquatic robots. However, at
least within the framework of the GURPS system this kind of drive tur-
ned out to be extremely expensive, with few advantages (if any) com-
pared to a hydrojet drive, so I finally deleted the idea from my list.

 

[rinku]

Well, you can't rise solely on contra-grav. So, it isn't a total replacement for ballast.

Well... ACTUALLY you may be able to, depending on the density of the sub. Referring to wiki, Bouyancy is defined as the upward force that opposes gravity, which is equal to the weight of the displaced volume of fluid.

So if the effect of gravity on the sub is reduced while the weight of water displaced is not, you will get upward force. A normal sub without water in its tanks will float (otherwise it's not much bloody good), so it's just a matter of design to produce one without tanks that varies its antigrav to rise and dive. Full antigrav would be counterproductive - you'd pop to the surface like a cork and might even float above the water (depending on air density).

Caveat - some of this depends on how you define antigravity. I prefer the type they used in Traveller New Era which had it just reduce the gravitational vector, with diminishing returns above about 95%. That mentioned the floating effect, too, but expected some kind of thruster to fly with. However, because water is so much denser than air it provides a LOT more buoyancy. None of this will help much with *lateral* thrust, so you'll still need a propeller or something.

http://en.wikipedia.org/wiki/Buoyancy

 

[DFW]

Well, you can't rise solely on contra-grav. So, it isn't a total replacement for ballast.

Well... ACTUALLY you may be able to, depending on the density of the sub. Referring to wiki, Bouyancy is defined as the upward force that opposes gravity,

Right. So, if you build a tank of water in space and you put sub in there that is less dense than the water, does it move?

 

[rinku]

Well, you can't rise solely on contra-grav. So, it isn't a total replacement for ballast.

Well... ACTUALLY you may be able to, depending on the density of the sub. Referring to wiki, Bouyancy is defined as the upward force that opposes gravity,

Right. So, if you build a tank of water in space and you put sub in there that is less dense than the water, does it move?

Without antigrav I don't think so, though there's probably *some* force from somewhere that's going to affect it (that's why zero gravity is not generally used these days in preference to micro-gravity).

Another test of this would be:

If you dropped a sealed tank full of water with a floating ball inside it, does the ball remain floating, rise or does it sink? What happens to a brick in this situation?

(and, no, I don't know the answers )

Edit: One little titbit from the wiki article I hadn't really realised before:
"Buoyancy reduces the apparent weight of objects that have sunk completely to the sea floor. It is generally easier to lift an object up through the water than it is to pull it out of the water."

Damn me, but *that's* what all that use of flotation tanks is about at NASA. It's not to give the illusion of reduced weight... it's to give *actual* reduced weight.