Space Warfare, Early
Interplanetary Age Warfare The first spaceships were slow, clumsy, inefficient, and incredibly frail, and remained so well into the Federation period. Nevertheless, human nature is such that, even as early as Interplanetary period, vessels were being adapted for combat in a vacuum.
Interplanetary age warships fell into two broad categories, Attack ships and Hunter-Killers. Attack ships were often essentially modified SIOS or heavy shuttles equipped with advanced sensors, and using smart rockets and drones (with either a conventional or a nuclear, much more rarely an amat, warhead) to bombard a target, and had beam, kinetic, and defensive missile weapons for point-defence. Hunter-Killers were equipped with rockets and heavy beam weapons. Their task was to seek out and destroy Attack Ships. A great deal of expense and research was invested in making these vessels invisible to passive scanning, and to give them the tiniest possible signature for active scanning. The so-called "stealth" materials, which absorbed all types of electromagnetic radiation, were invaluable here. Tactics often involved a game of hide and seek, not unlike the submarines of industrial and information age Earth. However, once the ship's drive units (usually nuclear fusion, in some cases ionic) were engaged the vessel was immediately visible. Again, if it used its active sensors it was visible. If it passed over a starfield being observed by defenders' telescopes it was visible. And once detected, both types of vessel were large, unarmoured, fat easy targets that could be taken out with a single kinetic or beam hit.
Federation Era Spaceforce The next five hundred years were a period of isolation of human habitation, with occasional forays by raiders and pirates in crude and often jerry-rigged nanobuilt ships, until the rise of the Federation of Sophonts ushered in a new era of peace of prosperity. While the Federation did not have any enemies comparable to the Interplanetary Age superpowers, the continued existence of stubborn, survivalist, and hostile haloists, backgrounders, shadow federationists, and exdependents, all of whom were resentful of Federation incursions and mining operations on their territories, and any of which would launch sudden guerrilla attacks on megacorporate and government outposts, required a defensive force of some sort. Instead of the large fragile expensive behemoths of the interplanetary period, the Federation used small, fast, short-range highly manoeuvrable vessels that were based in trouble spots and constantly on call. These included various designs referred to as fighters, patrol ships, area control vessels, and gunships. These terms were often arbitrary (what one polity or corporation called a fighter another would call a patrol ship) although as a generalisation, a fighter was very small (one or two man, when aioid it was called a "drone") and fairly lightly armed (light beam and a few rockets, almost never nuke), highly maneuverable, and of very limited range (often only chemical propulsion), a patrol ship was somewhat larger and able to carry somewhat more weapons but less maneuverable, and usually likewise very short range, an area control vessel was about the same size or larger again, and of longer range (usually ionic or nuclear propulsion), usually about as heavily armed as a patrol ship, while a gunship was either close or long range (depending on the drive unit), highly or not very manoeuvrable, but always very heavily armed. There was never any need for a long-range heavily armed vessel such as the old Interplanetary Age Hunter-Killer, as most insurgent ships were likewise small and relatively lightly armed; none of the haloists had the resources to make anything bigger, and those Backgrounders that did studiously kept to themselves and stayed in the outer Oort regions where even the megacorps did not bother to penetrate.
The Late Federation period - Effective Shielding and the System Control Ships With the ossification of outlying megacorps, institutes, hinterworld clades, and Federation colonies into hereditary Houses, the military option became a lot more important. Unless it had an insystem garrison, the centralised and bureaucratic Federation had no real power over interstellar distances. Rival empires, raiders, pirates, even rogue neumanns, were a threat to the isolated colonies and polities. Moreover, as well as defending, these developing dynasties often wished to expand their sphere of influence. And while many systems remained peaceful, many other suffered from prolonged interplanetary rivalry and even warfare, reminiscent of the old Sol System superpowers, but with a smaller population and more advanced ships. Most vessels were about the size of a Federation area control vessel (about 1-2,000 tonnes), and equipped with fusion pulse, fusion-ionic, or hybrid amat-fusion (pure amat was generally too rare and expensive out in the provinces) main drive that, when well optimised, gave a fairly respectable performance, chemical thrusters were quick close-in manoeuvering, sophisticated and usually state of the art sensors, target-acquisition, and fire-control systems, and the standard Federation era complement of beam and missiles (Newton's Third Law ensured that kinetic weapons remained impractical on such small vessels). Nanodefensive armour (reactive laminate, intelligent skin, absorptive/reflective dermalloy, etc) were widely used but generally not very efficient; especially in the case of the less technologically advanced clades and Houses, but stealth materials were widely used. Most of these vessels tended to be light and relied on speed, maneuverability, stealth, and of-course the ship's superbright (aioid or biont, depending on the clade) control systems to outfight and out-maneuver the opposition. However, there was also an astonishing diversity, as indicated by the contrast between the Arcadian Phagocyte hunter-killer class, the Minsky-of-Leher Cyclone heavy fighter, or the Freeman Warbird strike-interceptor.
While ships of the early Federation period had speed, maneuverability, intelligence, and devastating weapons, the development of decent shielding lagged behind. At the same time that the corporations were seeking ways to design protective shielding for interstellar vessels to protect them against interstellar gas, hard radiation, and cosmic dust, arms manufacturers and the military made parallel attempts to protect ships. The two approaches actually cross-fertilised each other, because cladding that can protect a relativistic ship against hard radiation may also work against optical, x-ray and gamma-ray laser weapons. The needs of each still remained very different, as a protective shielding that works for one kind of radiation often did not help against another one. However, super-reflective materials found use with both. These could defend against optical lasers, but were useless against particle beams and mass drivers.
It is generally agreed that the ideal military shielding should:
1. Reflect lasers
2. Reflect/absorb particle beams
3. Withstand physical/kinetic impacts
4. Be stealthy
5. Be light
6. Be robust and reliable
In practice even today no more than three or four of these is possible, even with ultra-tech.
In any case, by the middle to later Federation period a sleek new breed of warship had emerged, very different to the fragile behemoths of the late Interplanetary period. This led to the development of the giant System Control Ships, such as the amat-powered Constellation class, and the even larger conversion-drive powered Cerberus class, which made use of several new advances in transapientech for both shielding, AI control, and propulsion)
By the 6th to 7th century some of the Houses and regional Empires had likewise developed a sufficient industrial base to construct capital ships. The Penglaist Chung class Space Domination Vessel, the Doran Empire Excalibur class dreadnought, the Eridanus League Yi Sun Sin System Control Ship, and the Silicon Generation xd-1285 class fractal destroyer, were typical. These behemoths, equivalent in size to the biggest of old Interplanetary Age SIOS, were mostly used for showing the flag; gunboat diplomacy against recalcitrant colonies. Devastating against lightly industrialised or medium-tech systems, or rebels lacking deep-space capacity, they were at the same time very vulnerable to attack by swarms of superbright fighters and hunter-killer stealth missiles.
The Conver Ambi Layered Wave Formation It was actually the Conver Ambi that revolutionised interstellar warfare in the 2000s on, with their classic "layered wave" advance. This involved an advance swarm of massed nanodrone advancing sensors and assemblers, followed by and interfaced with low signature and highly maneuverable long-range fighters, then a second nanite swarm, then the escort vessels and heavy fighters, and finally the big capital ships and support and engineer vessels. In this manner they presented to an enemy an advancing front, stretched over several light hours, in which the most important and powerful vessels were defended by a shield of relatively expendable fighters, who in turn were protected by a shield of more expendable nanites. And conversely, starting with the flagship - the Fleet Command Ship - in the center (usually a dreadnought or space domination vessel), each layer could use the next layer out as not only sensor arrays but also mobile artillery.
The Layered Wave tactic was not original to the Conver Ambi. In fact in all its details it can be found in the works of the great strategist Admiral Jon C. Smyth-Ho of five centuries earlier. In Smyth-Ho's time however mercantilism took precedence over militarism, and neither the money nor the infrastructure was available for the building of ships on the scale required for the "layered wave". The Conver Ambi changed this, and soon the Federation was following suite, although never to the extent of the Conver Ambi.
The chief vulnerability of the "layered wave" was of course the fact that once the flagship was taken out the battle was over (the command ship not only was the center of operations for the admiral, but also for the administering priesthood and local aioid supervision). As easy as this seemed in theory though, in practice it was very difficult even for a stealth hunter-killer drone to penetrate the successive waves of nanites, fighters, escort vessels, and secondary capital ships, and the Conver Ambi proved to be one of the very few empires capable of maintaining a prolonged military advance over interstellar distances (other classic examples being some of the relativistic version war fleets, the Biovirate, and the Amalgamation, although the latter had the advantage of local computational self-modelling in each unit, giving a sort of pseudo-ftl/pseudo-telepathic effect).
But even with all its strengths, the Conver Ambi advance was not able to overrun the bigger and more heavily industrialised and hyperturinged systems. As awesome as a Conver Ambi battle group might be, it was still insignificant next to the resources of a single unified industrialised solar system.
Reactionless Drive The introduction of reactionless drives was a revolution that can not be strongly enough stressed. The downfall of the Conver Ambi, the Dorans, and even the Federation battle fleet was due simply to their being rendered militarily irrelevant by the SI:4 and their reactionless drive fleets. Pre-reactionless drive ships were easily visible, and, as they could not turn well (an especial problem for capital vessels), their trajectories could be predicted and they were easily targeted. Reactionless drives meant that ships could accelerate so quickly that having a non-stealth shield was not equal to suicide. Instead warships flew in erratic "butterfly paths", evading missiles and beams.
But reactionless drive, based as it was on metric engineering technology, was incredibly expensive, resource hungry, and required hyperturing intense processing and supervision for fabrication and maintenance. Some military civilizations - the cyber-dwarf Doran Empire for instance- simply disappeared altogether. Others, like the Conver Ambi, were able to continue their hold through clever memetic, cultural, and economic means. They were however never able to regain their pre-eminence, and the surprising thing about them is that they lasted so long. Meanwhile, hider groups like the Backgrounders simply withdrew to the depths of interstellar space altogether, no longer a part of galactic culture.