Paul5388
Registered: 11/22/08
Posts: 20
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Reply with quote | #1 |
I was reading another site the other day, from an old FT, and ran across some 1953 USN films on Fire Control Computers. They're in a two part series that explains the basic means for performing the analog computations necessary for fire control.
Once the gun(s) and the director are on the "same sheet of paper", through shooting a star, the parallax (remember, the directors are on the 05 and 06 levels and the guns are on the main deck and 02 level, so there's an angle between them when the same point is visually seen) can be computed and the point of aim will coincide at a particular range with the visually acquired target. The computer will also compensate for trajectory at that range along with the movement of the target, the necessary lead and the movement of the ship itself.
This 1953 information pertains to the gun fire control system the Little Rock had as CL-92 and also as CLG-4.
Here's a presentation that will give you something to think about (they will auto start from the links).
FIRE CONTROL COMPUTERS PART 1 video 19 minutes
FIRE CONTROL COMPUTERS PART 2, video 23 minutes
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Paul Jett FTG3, 1962-1965
http://www.handloads.com |
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Paul5388
Registered: 11/22/08
Posts: 20
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Reply with quote | #2 |
Maybe I should have explained "shooting a star" a little more.
When an object is light years away, the angle between two sights on the same vessel is so small, in comparison to the target distance, the angle is negligible. Some say the two sights are parallel, but everyone knows parallel lines never converge, by definition.
So, shooting stars optically becomes the same as if they were both looking through the same optical sights.
The distance between the director and the gun can be physically measured, which becomes a constant in the computations. That distance is always the base of the triangle that exists for any target and was part of the reason we learned some of those "A" school ditties, i.e. sine = O/H, cosine = A/H and tangent = O/A (where A = the adjacent side, H = the hypotenuse and O = the opposite side. (Those ditties are the reason I still remember the color code for resistors too. They just aren't repeatable on a public forum.  )
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Paul Jett FTG3, 1962-1965
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Artillery
Moderator
Registered: 01/25/07
Posts: 126
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Reply with quote | #3 |
Paul,
I remember several of the ditties. There were at least three of them. They help described the basic Trig functions you referred to.... which is important to us "missile types" as well.
In addition to the 5" and 6" gun systems, the ship's missile fire control system needs to rapidly and continuously "resolve" several angles both prior to, and after launch. Likewise, the missile's homing phase guidance system performs continuous calculations using these formulae as the missile closes in on the target.
Here's my helpers...
1. “Some Children Think Oscar Had A Heap Of Apples."
This was my favorite. (Although I do remember an alternate racier version.)
Specifically:
Some = Oscar / Had equates to Sine = Opposite / Hypoteneuse
Children = A / Heap equates to Cosine = Adjacent / Hypoteneuse, and
Think = Of / Apples equates to Tangent = Opposite / Adjacent
Below are the others I remember.... which are actually a little more user friendly when it comes to writing out the three primary functions: S = O/H, C = A/H and T = O/A.
2. "Some Officers Have Curly Auburn Hair Till Old Age."
3. "Some Old Hippie Caught Another Hippie Tripping On Acid."
Studying Basic Trigonometry during high school certainly helped me understand the details of my Navy rating better.... these little ditties helped as well!
Anyway, "Thanks" for your ongoing input.
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Art Tilley MT2
1962-1963 |
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Paul5388
Registered: 11/22/08
Posts: 20
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Reply with quote | #4 |
Art,
As a high school drop out, I was at a little bit of disadvantage, since I hadn't gotten as far as taking trig at that time.
Of course, the whole experience showed me how woefully inadequate my education really was and that helped spur me on to greater educational pursuits. Some things are reversible or they are subject to being superseded, like education. While I was on board the Little Rock, I managed to take and pass two GEDs, which helped open the doors to college when I returned to civilian life.
The source for the two videos is Gene Slover's site, http://www.eugeneleeslover.com/GS-USN-PAGE.html, which also has some torpedo videos and quite a bit of other information.
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Paul Jett FTG3, 1962-1965
http://www.handloads.com |
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