Imperial Navy Ranks

Officer Ranks

Lord-High Admiral of the Imperial Navy - This guy is a High Lord and is the single dude responsible for the ENTIRE Imperial Navy, though likely he doesn't do much other than delegate to his subordinates and attend tedious High Lord meetings on terra.

Lord-High Admiral - There are five of these guys, one for each Segmentum. While they're probably never anywhere near the front lines they probably have more to do, since its their job to oversee the deployment of battlefleets between sectors and ensure materials move properly from sector to sector.

Lord Admiral - The guy in charge of a battlefleet who gets direct command of vessels and formations. You see these guys in the fluff quite regularly when "key" worlds (like Armageddon) need defended or attacked.

Solar Admiral - Often a terminal rank... no really. Occasionally regular Admirals who do good jobs can put themselves forward for promotion to this position, which needs to be approved by the Lord-High Admiral, then the officer needs to travel to Terra be reviewed by the Lord-High Admiral of the Imperial Navy. Obviously this can take a very, VERY long time to approve. So they might often be dead before the promotion gets approved. If they get approved they are likely to get promoted straight up to sector commander (see Lord Admiral) as a position will have probably opened up while he was waiting. More rarely, Solar Admirals can get sent on "detached duties" which is basically a license to do as they please with their independent fleets

High Admiral - Commands several group of naval fleets (e.g. Battlegroups), often the most senior Navy officer in a Crusade but the things these fucks usually do is just having snacks with their Imperial Guard counterparts and leaving the combat duties to their subordinate Admirals.

Admiral - Gets put in charge of a battle-group and told to oversee some sub-sectors. He's usually the highest of the "front line" ranks and much of his time will be on active duty patrolling his assigned region or being sent to combat zones by his battlefleet's high command.

Vice Admiral - Battle-groups traditionally get split into three parts, with the highest Admiral taking up the portion containing the larger ships, while the "Vice" Admiral takes the "Vanguard" portion of faster moving ships.

Rear Admiral - The third portion of a Battle-group would be the "Rearguard" and usually gets assigned to the youngest/least experienced Admiral in the fleet. His job is usually the quietest one as he gets the mop-up and repair duties, this is also where inexperienced or freshly gained captains and warships gain combat experience before being reassigned under the command of a more important formation and higher ranking admiral.

Commodore - an experienced Captain in command of a squadron of capital ships. It's traditionally only a temporary rank, as capital ships don't always get assigned to each other the same way that escorts commonly do. But the realities of war often mean that ships stay together for extended periods, often well beyond the lifespans of generations of captains.

Lord Captain - not actually a rank, but an honorific applied to Captains of detached vessels operating independently. The "Lord-" part implies that they operate with the full authority of the the Imperial Navy when they act so they can deal with outside organisations (like the Mechanicus, Planetary Governors, Space Marines or Imperial Guard) on relatively even footing.

Captain - The commander of a single capital ship. He has total authority over those within the ship under his control.

Commander - Usually the ranking officer of an escort vessel or escort squadron. Is also the ranking officer on board orbital space stations. It also gets used as the terminal rank amongst Pilots, since small attack craft all fall under the remit of the Navy; so a Wing Commander would get command over all pilots based on a single carrier.

Lord Lieutenant - The second-in-command to captains of capital ships, bizarrely Commanders don't hold that role and hold their own positions. Thankfully because a chain of command exists in any military, despite a Wing Commander holding higher "actual" rank over a Lieutenant on a carrier vessel he would not hold any higher authority on that ship outside of commander pilots.

Lieutenant - A "working" rank. Either holds command over small system vessels or acts as second in command to Commanders of escorts, or as department heads on Capital ships. They are also Squadron leaders amongst pilots.

Sub-Lieutenant / Ensign - Team leaders or attack craft pilots.

Midshipman - Apprentice officers who haven't passed any exams or earned any responsibility, they would exist below the Warrant Officers in terms of authority, despite holding a commission. Midshipmen are commissioned from Imperial Nobility as part of the Imperial Tithe (which can mean virtually anyone gets the job if they send their useless heirs just to keep the best ones at home) but they are also assigned from the Schola Progenium. In addition, Midshipmen also may be taken on as a personal favour from the Captain of a vessel if he knows the family. This echoes the ancient real-world practice of young noblemen showing up while the vessel was in dock with a letter from their family and being granted a commission on the Captain's say-so.

NCO Ranks

Ship Master - the most senior Warrant officer on board a starship, also quite possibly the busiest man on the starship. It's his job to maintain the logs, update stellar navigation charts, oversee ships stores and order supplies, and command a hanger deck if there is one. Basically he's the guy who knows the ship better than anyone. In real-world historical usage, this guy would have an authority equivalent to a Lieutenant on board a starship, and would "mess" (ie: occupy the same space) as the other officers do.

Bosun - (Shorthand for Boatswain) The NCO directly responsible for all of the common crew members, including maintaining discipline. Despite his position, his actual rank may vary depending upon the size of vessel or operational requirements, in practice it never really matters since he's unlikely to ever meet another Boatswain. (real-world Boatswains could be proper Warrant Officers or not and held responsibility over all areas of the ship other than Engineering, which was left to the Chief Engineer, as if they disciplined/executed/imprisoned a skilled crewman from that department the ship could be crippled).

Note that most Capital Ships, but not all Escort ships, may have an actual Naval Commissar on board in this role, tasked with maintaining discipline up to and including the Officer compliment

(basically the commissar for the non-officers, and for the officers of most escort vessels).

Chief Warrant Officer - Also called "Chief Petty Officer" on some vessels. Will often be given command of important ship sections (like Chief Engineers, helmsmen, or auspex control, as these are critical to the ongoing operation of a starship)

Warrant Officer - You'll find lots of guys of equivalent rank on a ship, in command of various operational sections keeping the ship running at all times:

Masters of Ordnance- make certain that Torpedoes and Attack craft (if any) are fuelled and maintained. He is also the man who pulls the trigger on the Nova Cannon if the ship has one.

Master Gunner - have responsibility over all of the weapons batteries and make ensure they are loaded and fired when required.

Master-at-Arms - responsible for all "small" arms (since some warships, mostly battleships, can have whole divisions of Arms-men equipped much better than most Imperial guard divisions on board. The small arms aren't always 'small') on board a starship, overseeing all Sergeants-at-Arms, as well as maintaining order over any barracked Guard regiments currently in transit. Holds same authority as an Imperial Guard Colonel.

Master of the Vox - making sense out of the bazillions of messages that run through the bridge at any given moment both internally and externally (crews can get pretty massive, and a lot of traffic can come through at once). On larger ships he isn't alone, several Vox masters directing large teams of Vox operators on the bridge.

Steward - The guy who keeps everyone else well fed. A monumental task on larger ships (sometimes made easier by reducing the majority of the crew to slaves).

Gun Captain - Funnily enough, the man in charge of a single gun crew. Makes sure that the weapon is taken care of, is reloaded quickly enough, and is accurate when asked to fire. All of that comes back to this guy. While there are many (I mean literally thousands) that all share this rank on most ships, the dudes who man the lances and Macro cannons are normally treated as the superiors to the guys in charge of the smaller secondary weapons.

Sergeant-at-Arms - Man in charge of the weapons lockers and leader of boarding parties, as well as maintaining shipboard security. Usually they are transferred from Imperial Guard regiments so that they don't have any prior association with the crew (one of the best things that can ever happen to an Imperial guardsman, almost always a sergeant who was lucky enough to survive their first deployment). Normally a lot of these guys around, since they lead 'squads' and 'platoons' on board the ship.

Non-Officer crew:

Ratings - Press-ganged criminals or Voidsmen undergoing punishment through harsh service. They make up the majority of those sent to board enemy vessels and keep discipline on the ship. Different captains have different ways of keeping their Ratings in check, from implanting explosives into their heads to simply keeping them constantly drugged up to remain utterly obedient. Very few Ratings survive first deployment, but there is a limitless supply of low-lives the Navy can pick from to replace them.

Arms-men - Crewmen trusted to carry weapons. They are not true soldiers, as offensive boarding actions tend to be rare, but they are well equipped when compared to most Guard units. These guys also still have their own regular responsibilities on board ship as well, mainly in maintaining security and discipline. Since they are trusted more, they have slightly more freedom to move around the vessel as well, though most Imperial employees really don't want the job, since it means they get scrutinised more for any mistakes made, and they could end up being forced into beating up their buddies.

Voidsmen - the lowest rank of crewman on board a Naval Starship above the Servitors unless the Captain is cool with slavery (sometimes they literally are just slaves, but some of the more humane and less dickish have a legitimate crew of literally hundreds of thousands: most will never-ever see the captain or many of the officers in their entire lives regardless).

If they have a skill or a trade they may be referred to as Able Voidsmen which is an official rank that might require examinations. Additionally, if they show leadership qualities they might be promoted to Leading Voidsman and put in charge of work gangs and be considered for promotion to Warrant Officer if a position opens up on the ship.

I know I said I was done with this, but I forgot to include crew details. This is complete now.