Why Do Submarines Float So Low?

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One of the most important differences between submarines and other vessels is that when submarines slip beneath the waves, they more often than not come back up.

Besides stability while surface running, the other reason a sub sits low in the water is optimization of design. The more mass that can be dedicated to the hull thickness, the deeper the sub can safely dive. So the hull is made as heavy (thick) as possible, leaving just enough buoyancy for satisfactory surface running.

FYI for those that need to know... the submarine pictured throughout the video is NOT an Ohio Class, which is a Ballistic Missile or Cruise Missile Submarine, it is a Virginia Class, which is known as a 'Fast Attack' Submarine. The difference is that Missile Subs, also known as 'Boomers', are designed either to make entire cities vanish under a mushroom cloud (forming part of the US Militarys Nuclear Triad), or fling a whole bunch of Tomahawks to zerg-rush enemy defense systems, or just blow up a particular thing you really don't like. A 'Fast Attack' Submarine (the name comes from their speed FYI), is meant to patrol the oceans as a silent hunter. Be it enemy shipping, or enemy submarines (especially other Boomers), their role is to just hunt. Now, yes, modern Fast Attacks do have the ability to launch Tomahawks or Harpoon Missiles, however, they rarely carry such weapons as they take up valuable torpedo space, and when they're used, tend to mark the subs' location like a giant neon sign, making them easy pickings for either another submarine, or worse, Anti-submarine helicopters, aircraft, and warships.

animations have been really on point and the content is always fascinating. here is my internet points, good sir

Nice video! Just a quick point at 5:40, integrated electric propulsion is only a recent (re)development in nuclear submarines, the majority of SSNs use steam turbines mechanically linked to the shaft. IEP is quieter though, so it is increasingly featuring on new SSNs.

I loved the diesel engine sound the recharging sub made

Submarines are fascinating vessels, I love them

submariner is considered to be the toughest branch of any country's navy. its very hard and leaves a huge toll on a person to be locked in a tin can, underwater for months, so submarines always have the best foods available with treats and deserts. to keep their spirits up!

"So, why do ships need to when they ". Stability. Always, stability. Seems like stability is somewhat important for seagoing vessels.

Darn.. I was planning to use that length measurement at 7:57 to build my own, but that disclaimer that the information is not to be used as such, is really putting a damper on making one in my back shed

SmarterEveryDay has made an extensive series of videos covering life inside a sub, including how they move underwater and how they see, its really interesting

Actually, once submerged, you don't use compressed air to pump water from the variable ballast tanks to achieve and maintain neutral buoyancy. You use pumps, specifically - the trim pump. And typically, you don't even use compressed air to surface either. Instead, you drive to the surface and broach the ship. Once broached, you maintain enough speed to keep the boat broached and you then start a low-pressure blower to blow low-pressure air into the top of the main ballast tanks (MBTs), thus pushing water out of the MBTs through the always open flood ports at the bottom of the MBTs. Compressed air is more or less a precious commodity on a submarine. You've only got so much tank space to hold it and can only compress so much before you need to go to periscope depth to take a positive pressure in the boat so you can then start running the hi-packs (air compressors) to recharge the air packs since to compress air, you have to get air from somewhere and there's only so much air inside the pressure hull. So as you run compressors to compress air, you're depleting the available air inside the pressure hull. By taking a positive pressure in the boat, you basically have some excess air so that as you run the hi-packs and use up air, you're consuming that "extra air" so that when you're done - you're basically back to normal pressure in the boat, or 14.7 PSI.

5:42 There's one thing you didn't mention, and that is that atomic submarines make noise from the incoming water to cool the reactor. This noise is far louder than the propeller

They also have chemical oxygen generators (called "candles") onboard that can be used when oxygen goes too low. These work by thermal decomposition of chlorates: 2 NaClO3 -> 2 NaCl + 3 O2 There si a great hands-on presentation of the device on SmarterEveryDay channel (one where he visits an actual nuclear submarine). The candle burns slowly, generating oxygen for many people. It should be noted however that chlorates and perchlorates are hazardous being a powerful oxidisers - there was an explosion on HMS Tireless (S88) back in 2007 taking life of two sailors because one such candle has been contaminated by hydraulic oil.

The animations are high quality and serve to illustrate the points. I must nitpick: for the electrolysis, the anode should have twice as many bubbles as the cathode.

There's a decommissioned(non-nuclear) submarine, the USS Blueback, on display in Portland, Oregon. I took a tour of it once and it was amazing, especially learning about the gruelling schedule the crew has to work.

Nuclear submarines do not use compressed air to displace water in the ballast tanks to create neutral buoyancy. The ballast tanks are completely flooded with water. Buoyancy is maintained using trim tanks and electric pumps to pump water in and out. There are also aux tanks and drain tanks that can be manipulated to maintain neutral buoyancy and an even trim angle. There are two ways to get the water out of the ballast tanks if you want to surface. The first (and most fun to ride in) is using high pressure compressed air to “emergency blow” air into the ballast tanks making the sub shoot to the surface. The normal way to surface is to proceed to periscope depth, raise an induction mast out of the water and use a low pressure blower to blow air into the ballast tanks. As the air pushes water out through holes in the bottom of the ballast tanks, the sub becomes positively buoyant and comes the rest of the way to the surface. At least that is how we did it when I was an EM1(SS) PLANKOWNER on the USS Bremerton (SSN-698) where I earned my dolphins and became “Submarine Qualified”.

As a cook, I sometimes like to imagine being a cook on a sub. It just seems more interesting than being a cook in a hotel - but if I imagine it too vividly, I realize I would be terrified to be sealed in a can hundreds of meters below the surface.

I have to say, your ad read was VERY good. Just a very neutral, comforting delivery. Honestly, advertisers would do well to hire someone with the kind of ad read you just did. Sounds SUPER good and professional. I mean, I loved the topic and coverage of subs, don't get me wrong. But that ad read stood out to me as outstanding.