December 21, 2018

Spot 1

I've had the privilege of getting to see the inside of the forward Mk 38 Main Battery Director on both Iowa and Massachusetts. This position, known as Spot 1, is the primary position for main battery fire control, and provides an incredible view of the area around the ship. I thought I'd share some of my pictures from the visits.


The outside of Iowa's Spot 1

The basic purpose of the director is to provide range, bearing and level information to the fire-control system. This information allows the ship to know the position of the target and to compensate for the ship's own roll and pitch, so that it can place shells on the target accurately.


Me on the air defense level of Iowa, just below Spot 1

The view forward from Iowa's air defense level, about 100' above the water. Note Catalina Island in the background. This is almost exactly as far as the main guns could shoot.

Inside each director were seven people: a spotter, who controlled the director and passed spotting corrections to the impact location of salvos, a trainer, a pointer, a cross-leveler, a rangefinder operator, and two talkers, who are primarily there to pass information back and forth to the plotting room. The director is very cramped, even when you're up there by yourself, and it's frankly hard to imagine being stuck up there with six others.


The rangefinder inside Spot 1 on Iowa

The scopes for the cross-leveler and trainer on Iowa.

The rangefinder is a Mk 48 stereoscopic model, with 25x magnification and a 26.5' base. The other option for range information is the Mk 13 radar on top of the director. This gave full blind-fire capability to the ship's fire-control system.


Me in the trainer seat on Massachusetts. Photo courtesy of James Koppel.

Bill Hood, who was gracious enough to take us up to Spot 1 on Massachusetts, in the pointer seat.

The cross-leveler, using a 4x power Mk 56 scope, compensates for the ship's angular motion perpendicular to the direction the director is pointing, while the trainer points the entire director, which also provides the information on target direction, using his 12x power Mk 69 scope. He is aided in this by the rangekeeper, which is buried deep in the ship. It also drives the director, keeping it pointed at where it thinks the target is. If the crosshairs move off the target, the solution is bad, and needs to be corrected.


The bow of Massachusetts, seen from above.

The view from the air defense level of Massachusetts

The pointer (whose scope is out of the above shot to the left) also uses a Mk69 scope to compensate for angular motion along the line of sight. The pointer and trainer scopes can form a primitive rangefinder. Behind the rangefinder is a Mk 29 periscope, also 12x. This is used for spotting, and to look for new targets.


Indicator dials inside Spot 1 on Massachusetts

The Mk 38 director is a key component of the fire-control system of the last generation of American battleships, a system that gave them a decisive edge in their encounters with enemy battleships. Getting to visit was a privilege. The view from 150 feet above the waterline is amazing, and it's cool to see where the ship's eyes were located.

Comments

  1. December 21, 2018Chuck said...

    I'm surprised there aren't more bumpers, it seems like it would be hazardous holding your eye up to those eyepieces in the heat of battle. On that same note, does the rangefinder operator just sort of stand there with his back to the hatch? Or does he have a seat that is folded up somewhere?

    Amazing to see those views, I never think of battleships as being tall.

  2. December 21, 2018bean said...

    I've checked some of my references, and it does look like there's a fold-away seat. Re the bumpers, it's a battleship, not a tank or even a destroyer. The ship doesn't usually move all that fast.

    Amazing to see those views, I never think of battleships as being tall.

    I know what you mean. They don't look tall, primarily because of how big they are. They feel very tall when you have to climb all the ladders, but then you get to the top, and it's all worth it.

  3. December 27, 2018quanticle said...

    How heavily armored was the gun director? On the one hand, it seems like a fairly critical piece of equipment, so you'd think they'd armor the heck out of it to keep it safe from enemy fire. On the other hand, it's not that big, and more armor makes it heavier and more difficult to rotate.

  4. December 28, 2018bean said...

    I don't have the right reference to hand to give a precise answer, but it's splinter armor, probably 1-2". The big problem is topweight. You want the directors high up, which means they need to be light. The British main gun director (the Director Control Tower, DCT) was quite heavy, which meant it couldn't be mounted that high up, limiting range. And steel weighs 40 lb per in of thickness per square foot.

  5. January 01, 2019bean said...

    It turns out the answer was exactly in the middle of my predicted range. The armor on the director was 1.5" STS.

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