Submarines: How am into?

[Sharkman Briton]

I wanna make a submarine so bad but I can't seem to make it work, I've tried those small radial ore tanks full up as ballast but that don't work, the thing doesn't even pitch down! So how am into submarine? Thanks.

[SchweinAero]

What else do you have on your ship? A screenshot would help.

Most parts in current KSP are positively buoyant, so it usually takes more ballast than you'd think.

[Sharkman Briton]

it's not a ship I have, it's in general.

[capi3101]

In general, you want your craft to be as neutrally buoyant as possible before you stick it in the water. Kerbin's ocean's now have the same density as regular water - 1 metric tonne per cubic meter. You want your craft's density to be about the same. So what you can do (and this is a very crude method of doing it; an exact method would involve differential equations) is pop open the engineer's tab and find your length, width, height and mass. Multiply the length, width and height by one another; this is your crude volume. Divide your mass by your crude volume, and you've got your crude density. With a crude density value of less than one, your craft will be positively buoyant and have a tendency to float. With a value greater than one, it'll be negatively buoyant and have a tendency to sink. In either case, you'll need propulsion units to counter the buoyant tendencies of your craft; positively buoyant craft can also be made neutrally stable by adding ballast - say a set of monoprop cylinders set on decouplers. And then you'll need some kind of main propulsion system, obviously.

I'm pretty sure that a craft with a crude density equal to one would also have a tendency to sink. Why? The method of determining volume (length times width times height) is for a rectangular prism (a box). Unless that's how you're designing your craft, your actual volume will be somewhat less than this "bounding box" volume. Volume and density are inversely proportional to one another, so as you decrease volume, density increases. Fair warning that you're really probably looking for a value somewhere in the 0.9-1.0 range, with the exact break even value dependent on your craft's design.

That oughta be enough to get you started. I will say this - air acts like a fluid (the five words that give meteorologists nightmares), so almost anything you can apply to an aircraft you can apply to a submarine. You're just dealing with a medium with a roughly thousandfold increase in density.

Edited November 12, 2015 by capi3101

[Sharkman Briton]

Thankies

[capi3101]

No problem.

I wonder how popular making submarines is going to be in general, now that water behaves as it should. If they turn out to be really popular, I could see someone conceivably making a FAR-like mod that would voxelize your craft and give you a better approximation of its volume, show you its buoyancy tendencies, maybe come with a few ballast tank parts so you could be all Das Boot and everything...

Might be worth Squad's time to put a few easter eggs under the ocean is what I'm saying here, I guess.

[mcirish3]

So has anyone take the time as of yet to figure out what parts are negatively buoyant and what one are positive? I am guessing we may find some surprises there.

[Red Iron Crown]

So has anyone take the time as of yet to figure out what parts are negatively buoyant and what one are positive? I am guessing we may find some surprises there.

Check out this thread: http://forum.kerbalspaceprogram.com/threads/138931