Comment by podperson | Hacker News Reader

Comment by podperson | Hacker News Reader

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I'm amazed the basic underlying idea (which I believe the designer has been working on for some time) has taken so long to get real traction. In essence, the submarine is an underwater "airplane" that uses the principle of "lift" to go down (so if its engine fails it "falls" to the surface). This means no ballast tanks and a very simple, robust design (mechanical stuff outside the bubble; life support and people inside).

Oddly enough the only reason I know anything about this subject is that back in 1997 I was working as a game designer working on a "Tomb Raider"-like game but with the emphasis on the underwater gameplay (I thought Tomb Raider's underwater stuff was a huge missed opportunity, since I found the few underwater bits the most scary and tense).

Researching the back story I looked into what was happening in submarine design (a field that doesn't get a huge amount of coverage, even among geeks) and found out about these underwater "planes" and some stuff the US Navy was experimenting with (i.e. a modified Los Angeles class submarine that could launch armed drone subs, which is a brilliant idea since the most dangerous thing an attack sub can do in combat is launch a torpedo).

Again -- funny how slow progress seems to be in subs compared to everything else.

Actually, that idea is employed by every single US Navy (and I assume their foreign counterpart) submarine. The bow & stern planes combined with forward motion do almost all of the up and down depth control after you are under water. The ballast tanks are only really for changing whether you are a surface ship or a submerged ship.

The main disadvantage of not having ballast tanks is that on the surface, you won't float that high (I assume you will be slightly positively buoyant, because requiring power to get back to the surface is crazy, and perfectly neutral buoyancy is nearly impossible to achieve). This doesn't matter for a little thing with a tender, but for anything on its own, I'd rather float a little higher. Also, you have to keep moving to keep lift up. That just doesn't make sense for a boat that you spend a lot of time stalking around with as much stealth as possible.

As for "the most dangerous thing an attack sub can do in combat is launch a torpedo", that's just not true. The majority of the missiles launched against Libya this month came from US subs (SSGN). And there are a lot of capabilities that are secret or borderline secret. Check out "Dark Waters" and "Blind Man's Bluff". Also http://www.globalsecurity.org/military/systems/ship/dds.htm

``Lead On!'', by Rear Admiral Dave Oliver, Jr, 1992, claims otherwise on pages 50-51: ``On the day of interest, while operating at a deep depth, the digital-readout depth gauge on this ship stuck at a few feet shallower than the desired depth. As the submarine was not quite as light as the crew thought, the ship slowly drove itself deeper and deeper. No one recognized that the two other depth gauges were slowly creeping downward, correctly indicating that the ship was going deeper.''

There's a description before this of how 44 psi is 100 feet, and some of the depth gauges showed psi and others feet, and how the standard procedure had been to have the ballast tanks trimmed light, forcing a down angle to maintain depth.

The book continues ``We made several changes in submarines as a result of this incident. For one thing, we don't trim light and run with a down bubble anymore. If the ship takes a down bubble now, except during transitory conditions when the submarine is changing depth, then something is wrong.''

You're wrong on both counts.

The sub design in question has no ballast tanks. It literally "flies" downward and "sinks" to the surface. No navy subs (at least non-classified subs) do this. Not having ballast tanks is a huge design advantage.

Firing missiles from a Sub against a low tech country with no navy to speak of is hardly a combat situation. In naval combat the only thing subs are really afraid of is other subs and aircraft, and the best way to give up your position is to fire a torpedo.

Not having a ballast tank is decidedly NOT a huge design advantage for a military sub, because to stay under the surface you have to keep moving at a certain rate of speed. That is not a desirable trait when your primary goal is to be stealthy.

It IS a great design advantage for non-military subs when your primary goal is to be safe.

The concept is not exactly earth shatteringly new, I've seen concepts of it from navy contractors for decades, the Navy just has no use for one.

For surviving, yes, the only thing can kill a sub is a ship or airplane. How for succesfully completing a mission usually the goal is to remain undetected. That is certainly harder to do.

IMHO the cause for slow progress is due to most submarine research are restricted and classified as top secret.

At the other hand, I wonder why submarine exploration of oceans on earth is not regarded as highly as space exploration. Also while there are so many private start-ups focus on commercial space business, what about deep ocean? I know James Cameron's participation. But anybody else?

Technology: Submarines have to withstand hundreds of atmospheres of pressure.

Spacecraft? 1.

Professor Hubert Farnsworth: Good Lord! That's over 5000 atmospheres of pressure!

Fry: How many atmospheres can the ship withstand?

Professor Hubert Farnsworth: Well, it was built for space travel, so anywhere between zero and one.

Surely exiting a gravity well causes the spacecraft to experience an enormous amount of pressure opposite to the direction of its travel.

Many different forces for sure, but I doubt that acceleration through the atmosphere causes a uniform pressure over the entire craft.

In fact, would you get the opposote effect along the sides of the craft, where air is moving fast but parallel to the surface?

The weird thing about the design shown is that it really doesn't look particularly strong. Is that a glass bubble cockpit?

A traditional submarine is a huge steel cylinder. I thought there was a good reason for that.

From and article I read yesterday (I believe it was in wired) the "bubble" is solid quartz.

You mean zero :)

Negative one perhaps?

It doesn't have to withstand a pressure, but it does have to contain a pressure. Kind of opposite-ish.

Only if you build it in space.

Woods Hole has made autonomous ocean gliders that power themselves using the temperature differential of surface and deep water.

http://www.whoi.edu/page.do?pid=7545&tid=282&cid=370...

Speaking as someone who knows nothing beyond what you'd find in a Tom Clancy novel: The inability to quietly hold still is kind of a deal-breaker for almost all military & many research uses, isn't it?

Not necessarily. Holding still is useful, but a modern submarine isn't dramatically louder when in motion than it is at rest.

Sound from turbulent flow over the surface of the hull is minor and doesn't travel very far (IIRC it's more of a problem for listening than being heard). More significant is the noise generated the formation and popping of bubbles on the surface of the propeller (cavitation) as it moves through the water. But this is a function of depth in addition to speed: to prevent cavitation you can just go deeper. Or more precisely: the deeper you go, the faster you can turn your propeller without cavitating.

Exactly, thats why military can not and does't use airplanes ;).

If you don't care about being detected, why not just use a boat?

Perhaps because these can go faster, or deep enough that they can't be detected nearly as easily?

Well, it seems kind of difficult, in fact I am surprised it works. As you go deeper and deeper the water gets denser and denser which means the buoyant force becomes greater, which means that you have to exert a greater force to keep going down. If you rely purely on wings to exert that force, you will have to move with a pretty high velocity in order to exert sufficient force. It seems much simpler to just take on ballast and rely on good old gravity to pull you down.

If this thing works at all, my guess is it will have to go pretty fast, which would make it kind of dangerous and kind of hard to do exploration with.

Water does not get significantly more dense under pressure. According to Wikipedia, at an ocean depth of 4km, its volume is reduced by only 1.8%. That's not going to have to have much effect on the speed required to get lift.

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