Editing UGM-27 Polaris (section)

=== Guidance ===
At the time that the Polaris project went live, submarine navigation systems accuracy was adequate for existing weapons systems. Initially, developers of Polaris were set to utilize the existing 'Stable Platform' configuration of the inertial guidance system. Created at the MIT Instrumentation Laboratory, this Ships Inertial Navigation System (SINS) was supplied to the Navy in 1954.<ref name="MacKenzie & Spinardi 1988">{{cite journal |last1=MacKenzie |first1=Donald |last2=Spinardi |first2=Graham |title=The Shaping of Nuclear Weapon System Technology: US Fleet Ballistic Missile Guidance and Navigation: I: From Polaris to Poseidon |journal=Social Studies of Science |date=August 1988 |volume=18 |issue=3 |pages=419–463 |doi=10.1177/030631288018003002 |s2cid=108709165 }}</ref> The developers of Polaris encountered many issues from the outset of the project, including the outdated technology of the gyroscopes they would be implementing.

This 'Stable Platform' configuration did not account for the change in gravitational fields that the submarine would experience while it was in motion, nor did it account for the ever-altering position of the Earth. This problem raised many concerns, as this would make it nearly impossible for navigational readouts to remain accurate and reliable.  A submarine equipped with ballistic missiles was of little to no use if operators had no way to direct them.  The Polaris developers then turned to a guidance system that had been abandoned by the U.S. Air Force, the XN6 Autonavigator. Developed by the [[Autonetics]] Division of North American Aviation for the U.S. Air Force [[SM-64 Navaho|Navaho]], the XN6 was a system designed for air-breathing [[cruise missiles]], but by 1958 had proved useful for installment on submarines.<ref name="MacKenzie & Spinardi 1988"/>

A predecessor to the [[Global Positioning System|GPS]] satellite navigation system, the [[Transit (satellite)|Transit system]] (later called NAVSAT), was developed because the submarines needed to know their position at launch in order for the missiles to hit their targets. Two American physicists at [[Johns Hopkins University|Johns Hopkins]]'s [[Applied Physics Laboratory]] (APL), William Guier and George Weiffenbach, began this work in 1958. A computer small enough to fit through a submarine hatch was developed in 1958, the [[AN/UYK-1]]. It was used to interpret the Transit satellite data and send guidance information to the Polaris, which had its own guidance computer made with ultra miniaturized electronics, very advanced for its time, because there wasn't much room in a Polaris—there were 16 on each submarine. The Ship's [[Inertial Navigation System]] (SINS) was developed earlier to provide a continuous [[dead reckoning]] update of the submarine's position between position fixes via other methods, such as [[LORAN]]. This was especially important in the first few years of Polaris, because Transit was not operational until 1964.<ref>{{cite web| url = http://techdigest.jhuapl.edu/td/td1901/danchik.pdf| title = Danchik, Robert J., "An Overview of Transit Development", pp. 18–26| access-date = 2014-10-22| archive-date = 2017-08-21| archive-url = https://web.archive.org/web/20170821140444/http://techdigest.jhuapl.edu/td/td1901/danchik.pdf| url-status = dead}}</ref> By 1965 microchips similar to the [[Texas Instruments]] units made for the [[Minuteman II]] were being purchased by the Navy for the Polaris. The Minuteman guidance systems each required 2000 of these, so the Polaris guidance system may have used a similar number. To keep the price under control, the design was standardized and shared with [[Westinghouse Electric Company]] and [[RCA]].  In 1962, the price for each Minuteman chip was $50. The price dropped to $2 in 1968.<ref>{{cite book
| title=The Innovators: How a Group of Inventors, Hackers, Geniuses, and Geeks Created the Digital Revolution
| publisher=Simon & Schuster
| year=2014
| pages=181–182| title-link=The Innovators: How a Group of Inventors, Hackers, Geniuses, and Geeks Created the Digital Revolution
}}</ref>