The ranks of the Imperial Navy can, to a newcomer, seem confusing and arbitrary. To a certain extent, this is correct. The modern navy is an amalgamation from several different sources. Originally it was an ad-hoc organisation created from the navy, air force and traditional military forces of Old Equestria and carried over several naming conventions from them. As the study of the Arcane Sciences and Medicine grew, their tactical importance was not overlooked and they were added to the newly created Navy as separate divisions within the command structure. Over the last five hundred yeards increased hostilities and minor conflicts with the Confederacy helped wean out most of the unnecessary ranks, until eventually leaving behind the four divisions and the ranking system we use today. The four divisions are; Science and technology, Medical, Security and Command:
Command—represented by a blue sash except in the case of the admiralty, this division synthesises information from the other divisions and issues them orders in order to maximise fleet efficiency.
From top to bottom the command ranks are;
Fleet Admiral- the highest possible rank, these individuals are in control of entire fleets consisting of hundreds, if not thousands of ships. There are traditionally four Fleet Admirals at a time, with Queen Celestia acting as an honoury Fleet Admiral. This fifth fleet, referred to as the "Royal Fleet" acts primary as a self defence force due to the Princess' distaste to war and combat. Every pony that joins the navy will be assigned to one of these 5 fleets and will only be transferred under exceptional circumstances, although ponies may request which fleet they join when they enlist. The uniform of a fleet admiral is a white jacket with a golden sash bearing five golden stars.
Admiral- a lesser rank to the Fleet Admiral, each admiral commands between 10-100 ships and reports solely to the Fleet Admirals. Most admirals can be found either stationed in any of the capitals or attending a Fleet Admiral on their grand battle cruiser. An admiral’s uniform consists of a white jacket with a silver sash bearing a single gold star.
Captain- those who hold this rank command a single ship and all its crew, and as such make all executive decisions on a ship—not even a fleet admiral can counteract an order given by a captain to his crew without invoking ancient protocols, and is considered one of the most grievous insults a captain can receive. The captain’s uniform consists of the traditional imperial navy black jacket and a blue sash with five silver stars.
Commander- known as "captains in training", the role of the commander is to assist the captian in his duties, ensure his orders are carried out and help him maintain a presence on the bridge of a ship. A commander's orders are often held in the same regard as a captain's, although the admiralty may overrule them without penalty. It is also the highest rank that can be bought, or commissioned, rather than earned, due to an ancient law put in place to prevent the nobility from having to climb the lower ranks. This has the unfortunate consequence that most commanders are seen as incompetent snobs by the lower ranks. The uniform of a commander is the black jacket with a blue sash with one silver star.
Lieutenant- the jack-of-all-trades of the command division, they are often fill out the specialist roles on the bridge such as communications, helm and tactical. Another commissioned rank, most holders of this rank are senior officers from other divisions who have been promoted 'sideways' into the command division. Such officers can often expect a quick promotion to captaincy, should they meet their superior’s expectations. A lieutenant's uniform consists of the black navy jacket and blue sash with a silver stud.
Command Cadet- the non-com's of the command division and the lowest rank. Typically seen as dogsbodies, they are usually allocated grunt work considered below the upper ranks. Their uniform is the black jacket with blue sash, but no pips.
Security—the security division combines law enforcement with traditional military ground forces, in an elite organisation known as the mareines. The mareines are trained in various forms of combat, both ranged and CQC (Close Quarters Combat) and are a highly efficient military force. Officers of the security division often double up as tactical officers, controlling the ships weaponry and dictating tactics to the captain, although this usually only occurs on understaffed or deep space ships, where redundancy is usually not an option. Due to the vast majority of combat being space oriented, there are significantly fewer security ranks than in the command division.
The ranks of the security division are;
General- equivalent to an admiral, the generals command the mareine forces spread across the fleet. Only the bigger ships with a large contingent of mareines have a general on board. A group of mareines lead by a general is called a company, regardless of its size. A general's uniform consists of a white jacket with a red sash bearing 5 golden stars.
Chief- equivalent to a lieutenant, the chief commands all the mareines aboard the specific ship they are stationed on, unless their authority is overridden by a general. Chiefs often receive training to replace or even become a ships tactical officer. Such officers are occasionally promoted 'sideways' directly into the rank of lieutenant. The chief's uniform the same as a lieutenants, only with a red sash.
Sergeant- an informal rank around which a squad of cadets are trained to work around. The sergeant typically relays orders and information to and from the chief to his squad. As an informal rank they are officially unrecognised by the command structure, being little more than glorified cadets. However, most chiefs pay attention to what the sergeants have to say, being closer to the troops than the upper ranks. Sergeant's use the same uniform as a chief, but without the officers pips.
Security Cadet- the basic hoofsoldiers and non-com's of the mareines, trained to work in groups of 5-20 around a sergeant. They use the same uniform as the sergeant.
Medical—represented by a green sash, the medical division consists of Doctors, nurses and orderlies. Each ship, by royal decree, must have at least one doctor and one nurse on board to serve the wellbeing of the crew. Doctors also care for the crews mental health as well as their physical health, acting as therapists and councillors when the need arises.
The medical division ranks are;
Medical Officer- Equivalent to a lieutenant, medical officers are typically the most senior doctors on board a ship. They utilise the same uniform as a lieutenant, but with the medical division's green sash instead.
Junior Officer- a jack of all trades rank, this is for surgeons, nurses, therapists and non-senior doctors. Their uniform lacks the pip the medical officer wears.
Medical Cadet- the non-com of the medical division, cadets serve as unlicensed medical practitioners, assisting doctors and nurses in their duties.
Science and technology division—the most recent and most flexible of divisions, the science and technology division fills out various specialist roles. These roles are as varied as the disciplines of science, but can be typically be split into two categories; practical and theoretical. Practical scientists are technicians, engineers, mining geologists and the like, whilst theoretical scientists are typically astrophysicists or arcanophysicists.
The ranks in the science division are:
Science Officer- Equivalent to a lieutenant. These officers manage the various projects a ships science team would work on, and integrate them into practice. On the bridge they provide the captain with detailed technical information and manipulate the scanning systems. During combat they work with the tactical division to detect weak points in the shields of other ships. Whilst holders of this rank often specialise in a particular field of science, they have to be familiar with other branches of science as well.
Engineering officer- similar to a science officer, the engineering officer affords the same status, but whereas the science officer deals with various aspects of science, the engineering officer focuses exclusively on maintaining the ships engines and other systems.
Junior Officer- similar to the medical division, this is also a jack of all trades rank, with each holder typically specialising in a different aspect of science. It is the Science Officers duty to ensure co-operation between different Specialists and to ensure that their talents are used efficiently.
Science Cadet- the non-com of the science division, the cadets carry out the grunt work, preparing experiments and assisting the Officers with their duties.
-from A treatise on Imperial Navy customs, by Professor Clever Cogs