To get an inert object through the atmostphere and do real damage it has to be very large. That's a very inefficient way to use mass that you've boosted to orbit, even if it's relatively cheap to get there. So any weaponary they put up there will likely look fairly conventional. The speed of deployment and difficult of intercept would be the game-changer.

But why not a kinetic weapon though? 1000kg tungsten rod coming at 5 km/s and 3000K will sink any ship.

A bit tricky to aim though - basically the moment you initiate the burn for re-entry, you give 15 minute warning.

Well you answered it yourself, anyone competent can dodge that. It's useful for attacking existing installations, but well, you can do that with any weapon.

Plus it's easier to intercept orbital bombardment since you know where it is ahead of time and have plenty of time to intercept.

it takes few minutes for it to reach target so no it's not easy to intercept also what exactly are you planing to use to intercept a solid tungsten rod with exactly?

But it’s true for any orbital-based weapon that needs to de-orbit for striking. Once it starts retro burn you know it’s going for strike and know where it’s going to strike.

Aim it at something that can’t move

My understanding is that rods from god are not easily detectable during reentry the way an ICBM's warhead is.

I don't see why that would be.

You could also just put a ballistic missile on a satellite, then you'd have a guidance system.

Or a GPS guided bomb. Just fire it from a small rocket and let gravity do its thing.

It needs to re-enter, i.e. have the thermal shield, etc. This is what this Starship thing is all about - re-entry is really hard. Regular guide bomb is just going to burn or re-entry into atmosphere.

Any warhead needs guidance system. The question is if passive kinetic payload is enough or it should be something with explosives.

I've wondered about that. In a series of sci-fi books (the lost fleet series, starting with Dauntless), our intrepid heroes bombard military bases with BFRs. Big fucking rocks. Which are tungsten slugs coated with ceramic I think.

These are fired from light hours away at approximately 0.2 to 0.3 c. I had assumed that something going so fast would just disintegrate if it hit an atmosphere head on? The projectiles are described as "increasing velocity" as they approach, and they strike with gigaton effects. I remember reading an xkcd that showed something traveling so fast in atmosphere would cause huge explosions from air turned into plasma.

Depends on the mass of the object, of course, but at at this speed (i.e. energy) it will become a stream of particles going through atmosphere and vaporizing anything in it’s way.

a 20 foot long Tungston rod hitting at 10km/s would release 416 gigajoules of energy. Pretty much a small nuclear bomb or about 100 tons of TNT.

It's impossible to intersept something going 10km/s.