# Using centrifugal force to support pressure vessels

1. Aug 19, 2015

### cyberdiver

If the walls of a submarine were supported by fast-spinning rings, using centrifugal force to prevent collapse or buckling, would this be viable engineering? I am assuming that the rings would be magnetically suspended to eliminate friction. This also seems like a self-stabilizing system with regard to strain.

2. Aug 19, 2015

### K41

First, let me quite frank, my basic mechanics is shocking.

You asked would it be viable, well firstly, a centrifugal "force", as far as I am aware, it doesn't actually exist physically, its just a mathematical necessity depending on the frame of reference (it appears in rotating reference frames I think).

Even if you had some magnetic field which created a force (I think you calculate this with the Lorentz equation), you'd also still need to account for the fact that the fast spinning rings would also significantly alter the fluid around the submarine which further complicates things.

It's an interesting proposition and hopefully someone far more knowledgeable can respond.

3. Aug 19, 2015

### cyberdiver

I'm not sure how else to refer to centrifugal 'force'. Well, I suppose that's why I'm up here in the first place, right?

Interesting statement about magnetohydrodynamic effects. I've never considered that before.

4. Aug 19, 2015

### Staff: Mentor

Spinning rapidly, yet still providing structural support? Sure, it is possible in theory, but in practice it would be incredibly difficult, requiring enormous magnets, for example. You're talking about a mag-lev train running rings around the submarine, except that this train is supported from both sides!

And yes, the difference between "centrifugal" and "centripetal" is not relevant to the question. But yeah, "ficticious" is a poorly chosen name for something that is quite real, but just frame dependent so it doesn't show up in all reference frames.

5. Aug 20, 2015

### SteamKing

Staff Emeritus
Submerged submarines can be traced by searching for the subtle distortions a steel hull creates in earth's local magnetic field.

If you use a bunch of magnets to spin the hull like a mag-lev train, it's the same as turning on a flashlight in a dark room: the hunter can detect the location of the prey very easily then.

6. Aug 20, 2015

### cyberdiver

The hull won't spin. It will be support rings on the inside that spin, and magnets would transfer the centrifugal force to the hull to counteract exterior pressure. I'm basically trying to have a structure based on tension instead of compression. As for stealth, I conceived this idea thinking about gas giant atmospheric probes, not so much military applications.

7. Aug 21, 2015

### sickwayne

A question: are these support rings structurally sound?
If they are strong enough to withstand the loading due to the centripetal acceleration, then they would likely not physically deform enough to impart that loading into the maglev type radial suspension/bearing system so that it may be then transferred into the hull of the vessel. Also if these rings are intended to be structurally capable of withstanding the outwards load, then they would be able to also withstand an even greater inwards load due to their circular shape; and in this case it would certainly be easier and less heavy to build the vessel's hull like the rings and forego the rings entirely.
But, . . . if these rings are not strong enough to withstand the outwards loading that they generate, then they could in fact impart that loading into the hull by physically deforming and becoming closer to their magnetic supports. But there you have what seems to be a thin, gray line between being unstable enough to do the job and being too weak to handle all of the forces that something would undergo on the way to a gas giant.

8. Aug 21, 2015

### sickwayne

*You also have a gargantuan control moment gyroscope here!

9. Aug 22, 2015

### cyberdiver

Would there be a point where rapidly spinning it becomes more mass-effective than simply making the supports thicker and thicker?. As for the structural strength of the ring, I'm not entirely sure what the ring would be made of or what structures would be required on it (coils, etc.), because my knowledge of magnetics is rather lacking here

As for the gyroscope effect, since several of these rings will be required, having them spin in alternating directions should cancel out this effect.

10. Aug 24, 2015

### sickwayne

I am not well versed enough in these exact areas to throw up definitive numbers, but I do have some key points of design that I think would have to be accounted for.
1. If the rings were of a segmented design, they could easily be allowed to separate a set amount and still be strong in compression.
2. If magnetic repulsion through the ring's bearing/suspension is the intended method of transferring supportive strength to the hull, then the hull should be designed to have an allowable movement both inwards and outwards. Magnetic repulsion should prove to be a "springy" way to support the hull and some movement of the hull should be expected.
3. Variable support strength is a must and their are three ways I readily see to achieve this.
A- Method one would be to vary the rotational speed of the rings. A high energy requirement, but the mag-lev system could possibly be simplified.
B- Method two is to have a varying strength electromagnetic bearing/suspension system. The hang up here would be set the rings at a constant rotational speed that will be high enough to offer enough support when the demand is high, but low enough so as not to cause the rings to fail structurally. If the hull does not keep the rings compressed, then the rings need to be able to hold themselves together.
C-Method one and two combined - could possibly be the best of both. Sometimes option C's can be the worst of both worlds, so explore with skepticism.

Hopefully that will give a point of view that helps.