Wisdom of the manuever aside, can it be done? Has it been done?
Not intentionally. If it’s been done it was done in the process of sinking and nobody lived to tell about it.
It would appear not, for reasons derived from another simultaneous thread.
robby, a former submariner, explains how ballast works in a submarine in this post.
The main ballast tanks have valves at the top and permanently open grates at the bottom, to let water in when air is released. If the submarine barrel-rolled, any air in the MBTs would discharge out of the permanently open bottom grates, radically altering bouyancy.
Of course, it might be possible (I don’t know) to drive a submarine when its ballast tanks are full of water, using engines and planes, but I would imagine it is too big a risk to ever try.
I am not a submariner, but I think submarine guidance systems are designed only to yaw and pitch but not to roll.
It would have too have some roll control if only to maintain level. Edit: I suppose the buoyancy might act as a self righting mechanism.
To avoid air coming out the bottom you’d have to “fly” it through the manoeuvre maintaining positive G, I have no idea if a submarine is capable of this.
For an airplane, isn’t a “barrel roll” akin to flying in a kind of corkscrew path, maintaining downward g force for the pilot the whole time? I imagine the resistance of the water would prevent a submarine from performing such a caper.
The idea of a barrel roll is to maintain positive G.
There is no way in the world that a submarine could move fast enough to do that.
Presumably, you could design one to traverse a corkscrew path but it wouldn’t be a barrel roll in the sense that aircraft do them.
Aerobatic pilot Neil Williams used to tell stories of how he would barrel roll large military aircraft and no one ‘in the back’ would be aware that he’d undertaken the maneuver.
I have read the submarine Albacore did such maneuvers because it was a test vehicle and had many different control surface configurations.
You don’t need to be moving fast necessarily, but a barrel roll has both pitching and rolling. In order to maintain positive g you need to be able to either pitch or roll quickly. The slower your roll rate the more you need to pitch to maintain positive g and the faster you’d need to be able to go. On the other hand if you can roll quickly you only need a small amount of pitch to maintain the g.
I don’t doubt that a real submarine can’t do it but I don’t see why it wouldn’t be possible in theory.
But rolling is moving.
As is pitching.
And you need speed for the control surfaces to have sufficient control authority to do something like that.
Of course, I think we’ve been considering a sub that could carry a person.
It’s almost certainly possible to design a very tiny sub that could roll whilst maintaining +ve G.
You could use thrusters instead of control surfaces to achieve the required roll rate.
LOL, yes, I thought of that. The image was hilarious.
Also, you’d have to radically change the shape of the sub to allow it to pitch that fast in water. It would probably need to be virtually spherical to avoid cavitation effects.
Basically, you would be moving so far from the concept of a ‘submarine’ as it is understood today as to be completely irrelevant to the question.
If you roll fast enough you don’t really need to pitch at all, or not much anyway.
Edit: You’re right, you end up having some kind of submerged vertical centrifuge or something.
What if it was submerged in a giant version of one of those “endless pools”, kind of like, you know, a big … conveyor belt …
Or treadmill, I should say. Submarine on a treadmill!
Aside from the problems presented by ballast tanks, I doubt that the power plant would survive a barrel roll intact.
Consider the following:
[ul]
[li]A pressurized water reactor has a small steam-filled vessel that provides plant pressure to the water. If inverted, this steam bubble would go into the coolant loop.[]Steam generators (the nuclear power equivalent of boilers) have water in the bottom that boils and forms steam that leaves the top. Now we would get water directly in the steam piping.[]The main condenser, found under the turbines that form the main engine set, contains condensate, on its way back through to become feedwater. If inverted, this condensate would now be sloshing about in the turbine blades.[/li][/ul]
Since I did not serve on submarines, I don’t know about sub batteries and the like. Inversion probably isn’t nice for batteries.
BTW: I asked this very same question 25 years ago in navy nuke school to our instructor, a Lt-Cdr who had served on submarines. He didn’t seem to appreciate the humor and gave me a withering look.
ETA: On the other hand, if the batteries can handle it, why not completely shut off the power plant and prepare it for inversion (all valves shut, water drained, etc) and give it a go on battery power? Only problem would be that pesky reactor plant, that would need to be depressurized (not done without good reason and plenty of time).
I don’t know too much about small submersibles, but full-sized submarines cannot do a barrel roll.
Actually, as I stated in that thread, when submerged, the main ballast tanks are completely filled with water. There shouldn’t be any air in the ballast tanks. That being said, however, an inverted submarine is in a precarious position. It would not be able to initiate an emergency blow, because any air released into the tanks would just go out of the grates at the “bottom” (now top) of the main ballast tanks.
Little Nemo is correct. Submarines have a rudder, a set of stern planes, and a set of bow or fairwater planes. (Bow planes are on the hull near the bow, and fairwater planes are on the sail, formerly referred to as the “conning tower.”) Each set of planes act in unison; they are not “split,” like the control surfaces on an aircraft’s wings. The upshot is that large submarines have only pitch and yaw control.
As you surmised in your edit, Richard Pearse, the fixed ballast along the keel provides a self-righting moment.
The USS Albacore was a non-nuclear conventionally-powered research submarine with the first “teardrop-shaped hull” designed for prolonged submerged operation. (Earlier submarines had a hull-cross section closer in shape to that of a surface vessel, because they were primarily operated on the surface and only submerged for relatively brief periods of time.) One of the experimental stern plane/rudder configurations the Albacore had was an X-configuration, in which the planes operated independently. While this might have given the Albacore increased maneuverability, I’d be surprised if the Albacore was capable of a barrel roll.
There are a few issues with submarines doing a barrel-roll:[ol]
[li]It’s not necessary. Inverted operation contributes nothing to a submarine’s maneuverability.[/li][li]It would be too easy to lose control and exceed maximum allowed depth.[/li][li]In nuclear-powered submarines, the nuclear power plant is not designed for inverted operation.[/li][/ol]
With respect to point #2, people generally have this erroneous notion that submarines maneuver in the ocean like planes maneuver in the atmosphere. The unclassified maximum depth for U.S. submarines (from the Navy’s official FAQs here) is “deeper than 800 feet.” The FAQ also notes that “[t]he actual depth is classified, but it is less than the deep-diving U.S. Navy-supported civilian research submarines that explore the bottom of the oceans.”
With a vessel that is about 360 feet long (for a typical fast-attack submarine) or 560 feet long (for a ballistic-missile submarine), this doesn’t give a particularly large envelope of operation.
It makes sense that a submarine couldn’t do a barrel roll on purpose. But what about by accident? If a submarine surfaced during very rough weather, broadside to the waves, could they impart enough energy to essentially capsize the sub? And could this momentum carry the submarine through a full roll?
There must be some extraordinary set of circumstances that could cause this to happen, but the sub wouldn’t come out of it well.
Minimally, the power plant would be trashed (e.g. turbines probably would explode, or at least lose lots of blades). With luck the reactor could be saved.
Oh yes… I can’t imagine any electrical/electronic equipment would take too kindly to bilge water flying all over the place (do submarines have water in the bilges?).