Semi Submarines

There's a reason that most submarines are owned by governments - they're incredibly expensive. So what's a sub-loving consumer to do? Tune in as Marshall Brain breaks down the science behind semi subs (and why it makes them so much less expensive).

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from house stuff works dot com
where smart happens. Hi. I'm Marshall Brain with today's question,
what is a semi submarine? So we've all seen submarines,
and almost always their military submarines, and there's a reason

(00:23):
for that. Submarines tend to be quite expensive. There's two
reasons why they're expensive. First, any sealed container full of
human beings presents problems. You have to deal with the
oxygen supply. You have to deal with this carbon dioxide removal,
and you have to worry about humidity from the error
that we exhale from our lungs. So it takes a

(00:46):
fairly precise system to keep the oxygen level at about
You have to have chemical scrubbers that remove all the
carbon dioxide, and you you need to do something with the
humidity or you get all this condensation on the inside
walls of your submarine makes a mess. The second reason
why submarines tend to be expensive is that when you
stick that sealed container underwater in the form of a submarine,

(01:10):
the problems multiply. You have to deal with water pressure now,
so the container, including its windows, has to be strong
enough to handle depth and it doesn't take much depth
to create a lot of water pressure, and then you
also have to worry about how you're gonna dive and surface,
So you have to have ballast tanks, and you have
to be able to fill those tanks with water or

(01:31):
blow the water out of them. And you have to
make your container completely leak free, obviously, and that's not
a simple thing, especially if you're gonna put windows in it,
and that's why a lot of military submarines don't have
any windows at all. So what's the solution. What if
you would like to create a submarine, but you'd like
the lower the costs so that normal people can afford them,

(01:53):
One thing you could do is you could eliminate the
sealed part of the container. Second, you could eliminate the
problems with pressure by controlling how deep your submarine can
go and keeping it really shallow. And third, you could
eliminate the need for diving and surfacing, and therefore you
can get rid of all the ballast tanks and blowing
the tanks and everything that has to go with that.

(02:14):
Almost all the problems go away if you start putting
these constraints on your submarine. And that's the idea behind
a semi submarine. A semi submarine lets you, as a passenger,
ride around underwater, but the depth is very limited. It
might be six feet at most, and the submerged part

(02:35):
of the submarine remains open to the air above, so
you don't have to worry about pressurizing the container or
keeping the leaks out like you do with a submarine
that goes down a hundred feet. So here's one way
to think about a semi submarine. Think about creating a
small room. Say the size of a closet. It might be,
you know, four by four ft or four by six

(02:55):
ft or six by six feet in size, and it
might be six x or eight feet tall, just like
a normal closet in your house might be. You make
that closet out of a sealed container, either out of
fiberglass or out of steel, and you put great big
windows in it so that you can see out. Those
windows don't have to be exceedingly thick, because they're never

(03:17):
gonna be much more than six or eight feet underwater,
So you might make them an inch or an inch
and a half thick if their glass maybe about the
same if they're made out of acrylic. Now you put
a couple of comfy chairs in this closet so you
can sit and look out the windows. And now you
just have to get this closet submerged in the water
so that it's underwater but won't sink. And the most

(03:39):
common way to do that is to put some kind
of pontoons on top of the closet that will keep
the top of the closet up out of the water.
That is the basic configuration for some semi submarines. And
then you put a couple of electric motors on them,
or a little um gasoline motor or something so that
you can move it around through the water. And if

(03:59):
you're in a nice clear water, say around a coral reef,
you can paddle around with this with this floating closet underwater,
and you can see all kinds of stuff because the
water is nice and clear. You can look and see
the reef, you can see the fish swimming around the reef,
and so on. Without ever getting wet, and without ever

(04:20):
having to worry about scuba equipment or snorkels or anything
like that. You simply sit in your comfy chair, you
look out the window, and you steer the boat around
with some simple steering mechanism. Typically you find semi submarines
in resort areas. So if you go to Hawaii, for example,
you can find semi submarines that hold thirty or fifty

(04:41):
people and you go down below and you're about six
or seven feet underwater, sitting on a bench or a
chair looking out great big glass windows that are an
inch and a half thick. Or you can go to
resort areas and find little two persons semi submarines that
you can tool around with on your own. Semi submarines

(05:01):
were invented in the nineteen nineties and they've been pretty
popular since their invention. They're popular anywhere where you would
find things like glass bottomed boats. Be sure to check
out our new video podcast, Stuff from the Future. Join
how Stuffork's staff as we explore the most promising and
perplexing possibilities of tomorrow. The hau Steffork's iPhone app has arrived.

(05:24):
Download it today on iTunes.