Chain of Command for an Actual Space Force

Before we try set-up a Chain of Command we need to know what to command. Navy ranks isn't such a bad way to go as those countries having navies also have somewhat alike rank systems though wording may differ the idea is alike because of eh, ships - so kind a universal.

- humans, possibly not due to lates advances in long time stay in space even though we may find a way circumvent the effects of less blood to the brain which have some not insignificant effects on the behavior of mankind
- machines, possible and probably the possible if we don't find Un-obtainium and become able to circumvent the laws of physics
- independent machine units with lots of selfcontrol or even cyborgs (gasp!) but its easier to just care for a brain than the full human body, this latter could then in some way be moved to the first category though we don't have experience (that I know of but I may be wrong) of how a cyborg would handle itself on long strechtes of time and space; degeneration of cells though the feeding system should take care of that or sentience left with the brain making it impossible to control though such should be weaned out before or along long range journey's.

Is it at all possible given Earths resources? What size of Force are talking about - Star Wars? Forget it. More an more nations are putting satellite into space but payloads..

The Submarine image is my image of spaceships too which means that a central command in case of non-autonomous units (and being sentient beings - HUMANS dammit - we aint just gonne type SEARCH - REPORT - DESTROY).
Here already we need to deversify the elements of a force. Reconnaisance units to search for possible areas of use or presence or devoid of enemy forces - which can well be independent units constantly reporting their observations and of course build to concealt themselves to avoid detection.
Battle units that for starters would have swarms of independent reconnaisance units around it. Of course stuffed with appropriate missiles which of course make for limited hits delivered but a hit in space will be close to deadly - I don't see a hero like in Das-Boot banging wooden poles to the pressure hull to keep space out! Would be automated damage control anyways with a human overseer. Energy weapons for short range defences unless those would be very powerfull though that would be detriment to ship power etc. If semi-autonomous cyborg it may not require a human crew at all lessening a lot of daily drain on resources leaving more room and energy for weapons (but we want Tom Cruise to star the film..)
Transport unit - we need something to move the Space Marines - will have their own reconnaisance unit and a battle unit for defence or not and only move in when losses would be at acceptable levels (with more than 8+ billion humans of the Terran Confederation) that could be rather a hight percentage BUT it needs to get there and ANY setback being resupplied from Earth - I still expect us to be looking for the first habitable planet where we aren't forced to live underground to become green scaly skinned gargoyles. Yeah - the local fair Beauty! HA!
Supply unit - in case you haven't noticed humans tend to eat and drink known produce and then defecate - don't think un-obtainium will do much about such fact of Nature. A lot of them depending on size of total units and distance to target and propulsion. With un-obtainium drives its no problem we all know splitsecond from Earth to Anywhere.

Politics - is he raving mad, well of course he is - just think of such diverse politics of Nazis - Democracis - Communism - various Fascism - Religious anythings. Any such will dictate need for control. With the possible exception based on human history this far I don't see any of all sending off a force on an independent mission or at least with REAL Minders at hand not just a JAG.

Supplies/Logistics - is it at all possible with available resources - we assume so! (lunatics!)

Public opinion - we have had enough of war already - the Sovereign State of ?? Demands - this is a defensive operation. Of course its option three except when politics isn't Democracy.

So Reconnaisance - Battle - Transport - Logistics Arms of Service; seems known.
The Reconnainsance arm being the less human intensive unit though I'd expect a field control unit out there if only to relieve Central Command of "In Space No News.." day in day out. This would be very busy once contact is made or something of interest is observed say a small Moon of target planet not observed previously or old satellites seemingly out of work. Decisions have to made of what to do. Reporting upwards to Central Command and Task Force Commander. Perhaps depending upon situation initiate diplomacy - are we going to have silly Foreign Office and Juror and more neededless mouths to feed aboard? Depending upon situation - yes.
Will need Commander who can tell the civvies to shut up untill its their turn to act - we'll get you there now keep quiet please!

Battle arm being the missileartillery (mobile) though they may have drones or Fighters of course but that transport will be a drain on its weapons and abilities. A dedicated Carrier would be a solution so the Tom Cruise' of the future will have their own. Perhaps.
The unit(s) to confront the enemy. Will need a Commander who may be the overall Force Commander.

Transport arm the big one as it is transport human Marines. Here the various grades be as we know them. Holds units of all arms and makes itself a mini-force. Will need a commander of each and a Force Commander (not the Marine one).

Logistics arm to keep contact with home - peoples out there will want to be in touch with their loved one's etc. They have to eat and drink. They need replacements for the popcorn machines and bortsch-cooker. Anything that may break must be repaired or if not possible replaced. More stores than manpower - perhaps - but peoples of a lot of trades who know their trade to get shit up and running quickly.

How to name ranks - well depending upon the political landsscape and the history and tradition it may be anything. The popular misconception is that it needs be American! (incoming - incoming!) It will of course be some kind - now pretending the democratic style again (damn old fool) so a UN or what democratic World Government is ruling/Empire or Ecclesiastes is top dog (yes, Japan have an Emperor and is a Democracy and some religious based state may have a democratic government of sorts though it may be hard to imagine.) So something broad to embrace all.
If sticking with the Naval system the top is easy and probably the common as a lot of Navies use a broad field of like ranks: Admiral which comes in several classes, Commodore, Commander, Captain, Lieutenant, NCO's chief Boatswain, Chief Gunner, ect.