submariners could you answers this please....?

Question

i love the movie down periscope, while i was watching it yesterday it occured to me i dont know what the term "down bubble" means. is it a real term and what does it mean??

( my grandpa actually served on the submarine they use in that movie!!)

Answer 1

...to put it as simply as possible, think of a bubble inside a water-filled tube in a carpenter's level, which identifies the flat plane levelness of a surface; the indicator that reads the 'down bubble' and 'up bubble' on a submarine does pretty much the same thing, except that it's installed verically on a panel, in front of the planesmen (the drivers). The indicator is marked off in angle increments, or degrees, with 'zero' being the most flat plane levelness a submarine can attain. The bubble in the indicator shifts and adjusts itself to the resulting desired operation (rise, or 'up', and dive, or 'down') of the submarine, which is altered by the position of the forward and aft planes (the submarine's 'wings' and 'tail'), as well at the transfer of water to and from the various ballast tanks. Transfering water to the forward tanks (by alternately blowing air into & water out of the aft tanks, and pumping/flooding water into the forward tanks), and emptying the aft tanks, coupled with the proper adjustment of the forward and aft planes, will cause the bubble in the indicator to go below the 'zero' line, causing a 'down bubble', and a down-angle for the submarine; in turn, transferring water to the aft ballast tanks (by alternately blowing air into & water out of the forward tanks, and pumping/flooding water into the aft tanks), and emptying the forward tanks, coupled with the proper adjustment of the forward and aft planes, will cause the bubble in the indicator to go above the 'zero' line, causing an 'up bubble', and an up-angle for the submarine. The more water is transferred either forward or aft, combined with the proper plane adjustments, the greater degree of either 'up bubble' or 'down bubble'...

...when the diving officer calls for a specific degree 'up bubble' or 'down bubble', the planesmen will move the forward and aft planes accordingly, while the chief-of-the-watch, who is in charge of shifting water to and from the various ballast tanks, will conduct flooding/pumping/blowing operations, as necessary, to match the ordered degree of bubble, working in tandem with the planesmen...

...hope you caught all that; if I was able to draw on Yahoo! Answers, I could afford you an easy-to-understand diagram. Anyways, there you go...and this is from a 20-Year Navy Submarine veteren mechanic (...I parted ways with the Navy, about five-and-a-half years ago...and I actually still remember all this stuff!!!)

Answer 2

An explanation of what down bubble refers to...

http://www.maritime.org/ds.htm
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