Frankly, physical projectiles themselves are confirmed to be 'not a thing' by either one of Nyz' comments or a Dev-blog (can't recall).
There will be no (or very limited) ship-to-ship collision damage, to prevent 'ramming' PvP that is flagrant in Space Engineers, capable of putting a hole clean through medium-sized vessels with a single physical projectile (small purpose-built debris, accelerated to maximum game-engine speed).
The devs spoke out against large, destructive weapons, capable of one-shotting a vessel of comparable strength, so even if they do implement bomb elements, you can expect these to be largely un-viable against ship-to-ship combat, as you would need more armor on the projectile, to protect it from lock-on weapons, than you would gain from detonating it near the target.
However, a recreation of WW2 bombings on ground constructs? Now that would be cool