Summer in the Bahamas with Lorac

The summer of 1964 saw Michelson steaming around the Bahamas. Established a few years earlier, the navy's Bahamas test range was a good place for running sea trials on all the newly installed electronic stuff. While this navy operation, called AUTEC, was supposed to be for testing and qualifying submarines it had all the necessary radio navigational aids already in place.
The Bahamas test range was located in the very deep area just east of Andros island.

Two large transit cases arrived accompanied by a couple of wood crates. Volunteers lugged all this up to Survey Control where we unpacked two Lorac receivers, two strip chart recorders and a custom made aluminum mounting rack. The ship's carpenter helped install the Lorac stuff, bolting it down to a large chart table we used to study printouts, depth recorder traces and, yes, charts. The first in a succession of Oklahoma based Native American Lorac "tech reps" (field engineers) also appeared on board. These guys were real pros, very helpful and good to work with.

So, you say, what is or was Lorac? It is forgotten today, a radio navigation aid owned as a patented, proprietary system by Seismograph Service Corporation (Seiscor), then an oil survey support company from Tulsa. Intended for survey use, Seiscor claimed that Lorac was supposed to mean "long range accuracy". I immediately compared this with Loran, "long range navigation" and immediately became pre-clintonian, parsing the name. Lorac was a short range service, perhaps medium range, but clearly not long range.

Two Lorac receivers were installed, plugged in, furnished with signal using the two spare Loran C whip antennas. Voila! They worked. Two little problems surfaced pretty quickly.

(#1) Lorac needed to know where it was when you turned it on in order to tell you where you were located. It could track the ship's movement but there was no way to determine the correct "lane count". That's what the strip chart recorders were for. If you lost your lane count you could look at the record. It helped if the ship was steaming in a straight line. Otherwise, lost lanes meant somebody had to fly out the lane count to the ship. Yes, this happened! Alternately, the ship could go to a location where the Lorac position was known. A Lorac mail buoy, maybe?

In Survey Control we had a silly song "my Lorac won't come back" sung to the tune of  the Australian boomerang song. This was reserved for when we thought we had lost a lane somewhere but coudn't find it. A call down to the Seiscor rep was the answer. Get him out of bed and he'd stumble up to the bridge deck (03 level), check out the chart recorder and find the problem. Survey Control was on the starboard side behind the bridge, four decks above our living quarters.

(#2) The other anomaly had to do with taking readings from the receivers. Readouts from two dials, one called red the other green had to be taken visually, usually once a minute. These measurements of phase difference between station pairs had to be keyboarded into the Bendix G-15D computer, which when loaded with a Bahamas Lorac program on punched paper tape, did the math, calculating the ship's position. Our Loran C receivers did all this automatically, being hot wired to the dreadfully slow NAVDAC computer.

Operationally, this meant that one guy would read the Lorac phase meters once a minute upon the call "mark" given by the oceanographer on duty and somebody else would plug the readings into the computer terminal. It would take an extra oceanographer and/or an additional navy guy to accomplish all this, including plotting the computed chart positions and giving steering instructions to the mate in the pilothouse.

Lorac's accuracy was very good. Also available in the Bahamas were navaids Decca Navigator, which we didn't use but did have lane identification, and good old, familiar Loran C.