EFHA-OCSO-6 'Armageddon' planetbuster missile

The EFHA-OCSO-6 (European Federation High Admiralty - Omega-Class Strategic Ordnance) planetbuster missile is the single most powerful weapon ever developed by any nation of human space, and is one of the most tightly held secret of the European Federation. The missile is 560 meters long, and follows the standard space rule of 10x1x1 of dimensions, with 56 meters of width. That totals at a tonnage of 1 756 160 cubic meters, which is more than most frigates and even some older light cruisers. With this tonnage (which about 2/3rd is taken by various systems, the hull, stealth coating, ect), the EFSN's bureau of logistics was able to cram in no less than 18 gigatons of fusion fuel into the missile, using pressurized monomollecular tanks and active gravity generators. This fusion fuel, when the warhead is detonated, would yield approximately 11x1027 joules, or an explosion of 2.710 exatons of TNT, or over 100 times the upper levels of estimated energy of the asteroid impact suspected to have wiped out the dinosaurs. While not remotely enough to bust a planet, or even pierce the crust, it is enough energy to exterminate virtually all complex life on a world's surface, and completely destroy it's biosphere, or at least cripple it to a point where the survival of humans without massive technological assistance is impossible.

Needless to say, data about this missile and it's use was heavily restricted, with most of the engineers and scientists that worked on the weapon not even being aware it was being built, let alone why or where. In fact, most of the members of the design team thought it was more of a thought experiment relating to mass fusion experiments.

The missile itself was designed during the Ragnarok program, a mostly theoretical program about how planet killing (in the sense that the planet would no longer be able to sustain human life without massive technological assistance) super weapons could be designed. Most of the program was pure science fiction speculation, and some of the options were almost jokes in and of themselves, but the intent was to bury the actual super weapon design under the rest, which was successful. Of the handful of viable designs the program yielded, only 3 were retained for operational use.

Unbeknownst to everyone but the highest ranking officers in the EFSN, the weapons weren't actually a reaction to the UIS' rearmament as advertised to those privy to the information that the weapon would be built, rather they were the continuation of a program began in the aftermath of the Martian Revolution, fearing that the UIS counterattack would be so bloody that the inhabitants of the red planet would have no choice but to destroy Earth to survive. Thus a program was created to study potential super weapons and counter them. That program (called Nuit Éternelle, French for eternal night) eventually evolved into the Earth Orbital Defense Grid Initiative, and the Valhalla program. The Valhalla program yielded a total of 3 super weapons design, 1 purely kinetic, in essence a relativistic kill missile on the scale of a battleship, 1 an extremely hazardous and virulent bioweapon taken from the Terran Hegemony's arsenal, and the last a nanotech 'grey goo' style weapon. Needless to say, the Valhalla program was EXTREMELY secretive, as all three weapons violated several laws and the latter two outright violated the European Federation's constitutional ban on biological and nanotechnological weapons.

The Ragnarok program was built to replace the ageing Valhalla weapons mainly because it was clear that Earth might become the target, and Mars had developed and put into place it's own Orbital Defense Grid. Thus new weapons were needed, ones that could penetrate an extremely sophisticated defensive perimeter like an Orbital Defense Grid, and still be able to do enough damage to wipe out the biosphere, and virtually all human life on the surface. Since relativistic projectiles simply wouldn't work against an ODG, and the EFSN did not possess inertial compensators good enough to prevent any nanotech or bio weapon from being destroyed by the sheer g forces required for a missile to get through the grid, completely new designs were required.

Additionally, the Valhalla weapons were made to be fired from Earth itself, and thus a new weapon platform, capable of carrying the weapons themselves and delivering them to other solar systems if necessary was thought up, the Final Contingency-class cruisers. It also added second strike capabilities, as a threat assessment concluded that if the European Federation could make stealth weapons platform good enough to conceal a first strike planetkiller capability, the UIS most definitely could as well.