Look here.
http://en.wikipedia.org/wiki/BrahMosIts technology TODAY.
And it can go up to Mach3.
Speed of sound is 340.29 m / s
Meaning, this can go 1000+ M/s
And this isnt even the most advanced tech today.
The range of these missiles doesnt have to be more than a few kilometers at MAX. A ballistic bomb with no rocket propulsion also would work. Its only a few kilometers!
In space, there is NO Friction with air, and no Gravity to pull down the missile.
Its reasonable to assume that Anti-Ship weapons hundreds of years in the future can go 1000+ m/s.
Flak/Turrets find it hard to shoot down a bomb at 150 M/s, which isnt even much. Get a Helios, mod it to go 150 m/s and get a Fenris to shoot it at any enemy ship. Especially an Orion. 95% of the time, the bomb will reach its target. Unless there are some 30 ships running intercept. And even then, its highly unlikely. No ships except a few Shivan ones can go at 150 m/s.
Edit: A cyclops bomb is fission bomb. Meaning, its as stable as any weapon in modern arsenals. Nuclear bombs dont explode when shot. They need to be DETONATED. Meaning, risk of blowing up is minimal.