I feel my inner nerd awaken. The nerd is the hot light in the darkness. All else is unfullfilled void.
This is a special place.
We must not allow this place be soiled by the Non.
Non must go. Now.
Okay lets take this dead serious. Space warfare. Tough cookie.
Lets pick up a scenario, two neighbouring planets at war. We pick a random setup, lets say world Earth located in the Sol system VS some random world at Alpa Centauri.
Allowed are all forms of technology, but only REAL technology, nothing imaginary.
To flesh out the scenario a bit more we assume Centauri is invading the Sol system with the goal of claiming the planet - intact - well, more or less. Certainly more is ideal but colleteral damage in war is nothing unusual.
Maybe because they picked up their transmissions (really old transmissions) or because that golden plate we sent into space fell on the head of somebody really important.
Who cares? Lets assume the role of the invader.
Obviously the first problem we run into is the trip to Sol itself. The distance is 4.37 light years. Clearly a short range engagement in galactic scale. We naturally want to get there as fast as possible.
Einstein proposed there is nothing faster than light. Well... not exactly... thats greatly simplified.
What he really said is: the faster you go the slower time resolves for you. The slower you go the faster time resolves.
If somebody has any doubts regarding this i recomend reading up on GPS sattelite time syncronization correction formulas. There are also experiments with nuclear clocks and jetplanes. That is a fact ladies and gentelmen.
What he talked about is "slow light images" and the general perception somebody has rocketing into the night sky - because the night sky is an image of the past (light takes time to travel, so its a really old image), and technically you catch up on it the faster you go. Its not that easy, its not only affecting the perception, it seems also affect physics in a more general way (wich explains the clock experiment or correction formulas for sattelite time sync). Personally i belive its somehow linked to gravitation per se, but thats pure speculation.
What do i want to show with this load of physics garbage?
Well, for the most part that there is no galactic tempo limit. There have been experiments transporting information at above light speed with the use of quantuum effects - maybe a little garbled, but it worked.
Whilst a great deal of people are searching for a key to the stars (hyperdrive, FTL, wormeholes, spacefolding), it becomes slowly clear that nobody locked the door in the first place.
So, considering time runs faster the faster you move we want to move as fast as possible.
So, what is the most powerful propulsion?
That would be... a fusion blast.
Imagine a big (really big) fusion bomb loaden mothership. Ironically the drive is also its most powerful weapon. Not a big surprise. The world ain't ready for such a vehicle. Imagine how the Russions would freak out if the Americans build such a thing. Or vice versa, also applies. Or a madman at its controls. Not good.
Moral aspects aside, the next problem we run into is acceleration.
Basically there is not much stopping us (there is and it becomes really dangerous at certain speeds, but from a viewpoint of pure acceleration there is not much holding us back, only the need for thick armor and a redundant design for particles ramming the ship at approximately lightspeed). The idea is to blast us to speed with a few nukes, savely shielded from radiation in our ship.
Of course the human body can only withstand a certain degree of acceleration. Remember - no dampening forcefields.
So we have to accelerate in tolerable parameters. This means slow acceleration, slow breaking. Remember at a point there will be no gravitational pull from stellar bodies, so the only thing really interesting are the forces during breaking and acceleration.
That are the basics. Of course the trip will still take some millenia (assumed, we'd only know for sure through experiments and people are a little itchy about orbital nukes for some reason).
No cryogenics. We have no working cryogenics. So the ship has to be a home for some generations to come. It has to be able to sustain multiple generations, it needs kinda self-regenerating systems and because those systems can fail or are not entirely perfect loads of supplies. Remember as i mentioned it has to be big? Make it epic.
And since we expect an advanced civilization we want to take over we finally come to the Space warfare part.
The smartest thing to do would be to sneak into the system collecting some data about our opponent first. Its kinda hard to be stealthy if you use fusion bombs for decelleration *g*
On the other hand we have two advantages on our side:
1) with all the stellar anomalities to watch it could be interpreted as some natura occurence, mabe a comet or be overlooked alltogether
2) "aliens are attacking us" is not really considered a sane response and everyone will look for another explaination to appear sane, even if there is not really one
For that reason it would not be totally futile to appear as a big piece of rock and at least attempt to make "natural" movement only until it is too late. Probably being as less visible by taking advantage of a nearby planet or the moon between us and them.
The idea to launch a quick all out barrage of fusion missiles at all major population centres (mexico city for an example), capitals and so on is intriguing, but would almost certainly trigger a retaliatory strike of some sort.
Another possiblity would be to launch a shuttle to take samples and develop some sort of biological weapon, minimizing enviromental damage in a quick hush-hush night op. A stealth design for the shuttel would not hurt at this point. Of course in the case of detection we risk also a retaliatory strike.
In this case we have to face the possibility to be confronted with a hostile response, so we need to be prepared for that.
The most obvious weapon being ultilized are thermonuclear weapons, so point defence is mandatory.
I am not a big fan of energy weapons because energy can be deflectet and for the fact that those weapons are indeed a bit unwieldy and take up too much space. Magnetic (for an example) accelerated high speed explosive rounds littering the area with debris seem so much easier and better.
Energy weaponery could be used for actually sieging the planet, maybe with a set of mirrors to focus Sol's own light concentrated to the surface. Its true energy weapons take an enormous ammount of power, but seeing a huge power source is present already it would be a shame to let it go to waste.
However, the best strategy would be to avoid confrontation with our mothership as much as possible. We could launch guided missiles from behind the moon, but honestly - some sort of missile loaded attack craft would be so much better and also allow to break through defences (no computer replaces an aware pilot when it comes to adapting to the unexpected) and strike targets at the surface with more precision. The could also act as interceptors for threats lauched vs the mothership, like missiles and opposing attack crafts. A missile can't strafe crucial targets. An attack fighter can. And it allows attacking from a safe distance.
For pretty much the same reason some kind of large scale orbit to surface transport vehicle would be interesting - for boarding opponent craft, orbital installations and of course to land ground troops.
Surely - a nuke will eliminate any of those vehicles, but i rather trade fighters and/or transports for nukes than seeing the mothership go *boom*. Those will at least stand a chance to avoid a missile or spread in the case of large scale area attacks.
And if thats not working we threaten to blast the moon out of orbit ^^
"Can we really do that, Commander?"
"No, but they don't know this."