[url=http://www.rocketpunk-manifesto.com/2009/08/space-warfare-vii-kinetics-p... Space Death Buses is an interesting concept[/url]

The only Setting I can remember having these is David Weber's Honorverse, and more like a concept than a usable thing, and it works the following way: - Premise: FTL travel is possible by Hyperspace "cheat", but gravity is related: you cannot jump unless you are a very long way from the local star (in EP, at least on Uranus or even Eris' distance from the Sun). There is also the possibility of using wormholes, but less than two dozen of such can be used (the rest are not stable or connected to nothing at all). - Premise: spaceships use a "gravity wedge" that, aside from generating a gravitational distortion that can be picked FTL (in-system), is completely unpenetrable. The Gravity Wedge is composed of two defined and limited planes (that would cross themselves on the aft of the ship if prolongued) at thousands of gravities. - Defensive Premise: Top and Bottom of ships are protected by the Wedge and are, thus, invulnerable. Sides are protected with force fields (with openings to fire onboard weapons) and armor, but the front and back of the ships have only armor, because the back has to be clear for the Wedge to provide accceleration and the front has to be clear not only because of that, but also for the sensor systems. - Energy source: hidrogen-based (from one point onwards, nuclear for some small "fighters" and missiles). - Premise: FTL Comms are not possible (until a point, and only for one faction... until another point, then it is avaible for two factions. In all cases, this can only works inside of the solar system). - Premise: all ships and missiles have a top speed they cannot surpass, even with constant acceleration, without suffering damage to the frontal systems - Effect: Missiles use this same system for propulsion (but at one time, they get a second and then a third reaction drive). A drive cannot be turned off and then reignited, and some energy in the propulsion system is needed for a missile to not go "ballistic" (straight line. Missiles are programmed to self-destruct to not ruin somebody's day millions of years after launch). Also, the propulsion system has to be on at launch. - Limitation: missiles are very limited by space: they are essentially controlled/aided by the launching ship, meaning distance has an effect on accuracy (once the in-system FTL comms and multiple drices missiles are researched, this becomes irrelevant). - Relativistic kills: a ship accels to its max (about 500 gravities in the first books, about 600 or so in the later ones) in a collision course with its target, and then launches its missiles configured to get most speed. 0.96c is possible, but the missile will go in ballistic, and the propulsion system can be tracked while engaged. Since the missile has to go ballistic and you had FTL warning of its launch (and even at lightspeed, lag is there: it takes hours at a constant acceleration of 500 gravities to cross a solar system). Conclussion: in this Setting, relativistic Weapons are only useful against targets that cannot dodge, like space stations or planets. Habitable planets are protected from orbital bombardment by an edict enforced by the biggest navy in the setting, by the way.

Prophet710 wrote:

Next question. Could you miniaturize this, something the size of say, a Javelin (the ballistic missile launcher suite, not the spear you throw). Obviously not a one shot kill, but more like a recoil-less 20 cal. ??

Yes, it is called a particle rifle. Of course, the missiles are now individual protons. The problem with RKVs is how to spend the energy needed to accelerate the projectile without vaporising it. And if you can get that much energy, you also need to consider whether it is best to just beam it straight at the target instead. RKVs do not make sense in all settings. (The classic RKV novel is Pellegrino's "The Killing Star")

Existing superconducting batteries could do one shot (assuming 50 kilos of batteries, and future batteries 50x better than today's best; 1.01 Mj/KG), but your problems are weapons efficiency and projectile size. A 1 gram projectile travelling at .96c would develop an energy equal to 2.288E+15 Joules. This is beyond the energy possibly generated by a humanoid sized system, but perhaps in EP Tanks and other vehicles could generate this much power. For comparison, a .50BMG rifle round weighs over 50 grams and delivers about 18,000 joules. Your issue now is how much energy actually bleeds into the target- I can see it simply punching a hole through the target without significant damage- but even a 1% energy dump would result in a localized explosion.

Xagroth wrote:

Imagine the kind of damage to the surroindings a 0.96c projectile can cause just by passing by.

The webcomic xkcd did cover what would happen if a baseball was thrown at 0.9c (ignoring how that was achieved). The effects are not pretty. You would probably be creating a creating a nuclear explosion in the barrel of the gun. http://what-if.xkcd.com/1/

Xagroth wrote:

Yes, because that kind of weapons are considered "anti-material" ones, and cannot be used against personnell. Funny thing, a uniform is a "material", or a vehicle too. The Geneva Convention also forbids to shoot against medical vehicles if they sport the Red Cross (or equivalent) symbol and are unarmed and used for medical purposes. I think in WW2 some of the "hospital ships" sunk by the Germans were in fact being used to move troops and supplies, and today we have the Merkava version that exchanges the explorer's space for medevac stuff and its, therefore, unprotected by the Convention (because it is a tank!). I think the only "relativistic" weapon we can implement in EP without breaking the setting's atmosphere of "hard" sci-fy would be laser weapons and the kind.

I've done the calculations before, but clearly I need to expand on them. It is possible (theoretically) to build railguns that are 50% efficient, but no rail material would ever survive blasting something at .9C. A coilgun is never in contact with the projectile, and therefore could hypothetically launch this relativistic projectile. A 1 gram .96c projectile would have an energy of ~2.28E15 Joules, I compared it to a .50 BMG round, but perhaps a more suitable comparison is tons of TNT; One ton of TNT (metric) has energy equal to 4.18E6 Joules. Thus, our hypothetical projectile has more energy than 545 Kilotons of TNT! Thats 545,000 Tons of TNT! For reference, the Hiroshima nuclear device yield was ~20,000 tons of TNT! This is over 27 Hiroshimas and change! Another comparison would be the American Minuteman III warheads- each MIRV's warhead is a mere 330 kilotons! Assuming a coilgun efficiency of around 30%, you only need your capacitors/other energy jars to hold about 7E15 Joules of energy. Thats less than 2 Megatons of TNT! Or the energy supplied by joining 50 grams of Antimatter to normal matter. Of course, Antimatter-Matter reactors can hardly be expected to even approach 50%, forget 100% efficiency... but it shows you, in EP, it is quite possible to use relativistic weapons. If you are willing to accept even smaller projectile weights, even the EP equivalents of Tanks could theoretically fire relativistic ammunition.

NewAgeOfPower wrote:

Of course, Antimatter-Matter reactors can hardly be expected to even approach 50%, forget 100% efficiency... but it shows you, in EP, it is quite possible to use relativistic weapons. If you are willing to accept even smaller projectile weights, even the EP equivalents of Tanks could theoretically fire relativistic ammunition.

Though doing so in an atmosphere would cause a nuclear fireball with the tank at ground zero, which isn't survivable.