Orbital Sieges and Assaults

[Uberlord Gendo]

The question about Magnus got me thinking, what do we know about how orbital defenses, sieges, and assaults work in 30k?

Most of the examples I'm aware of are pretty lopsided, but I think there was a short story in one of the anthologies about doing scenarios through psyker mind hacking with the Sol system defenses against Horus' armada where the star forts were literally fortresses.

How do ground batteries work? If Vraks is any indication, the combination of Vraks' defenses and an orbital made the Siege necessary in the first place.

So assuming all things being equal what sort of stuff are we dealing with? (Like broadly equivalent forces.)

[Marshal Rohr]

Ground defenses are a combination of missiles like our ICBMs and high powered lasers that have a limited effective range. Missiles are obviously finite and can be intercepted, lasers lose power after a certain range. Void defenses just move those lasers and missiles closer. Edited May 6, 2021 by Marshal Rohr

[Arendious]

Macro-cannons are mentioned as ground-to-space weapons, as well as titan-scale plasma weapons.

 

Said macro-cannon are *probably* railguns, though something like Bull's Baghdad Gun would be quite appropo.

[Marshal Rohr]

Titan Scale weapons are still very small by ship standards. I can’t remember where I saw the comparison but someone mentioned Titan scale weapons like the Sunfury or Bellicosa would be extremely close range ship weaponry and would be on those Gun decks on the models that don’t really do anything in BFG.

[Billy the Squid]

The question about Magnus got me thinking, what do we know about how orbital defenses, sieges, and assaults work in 30k?

Most of the examples I'm aware of are pretty lopsided, but I think there was a short story in one of the anthologies about doing scenarios through psyker mind hacking with the Sol system defenses against Horus' armada where the star forts were literally fortresses.

How do ground batteries work? If Vraks is any indication, the combination of Vraks' defenses and an orbital made the Siege necessary in the first place.

So assuming all things being equal what sort of stuff are we dealing with? (Like broadly equivalent forces.)

 

GW has been pretty vague regarding ground batteries, ranging from defence laser silos, surface to ship missiles, macro cannon emplacements all have been mentioned in the lore. The purpose is to target ships in low orbit, where ships move to deploy ground forces/ provide supporting fire with some degree of reasonable accuracy (a god engine may look big, but trying to hit even a titan 1000km away while in low orbit is a tall order)

 

So the purpose of ground emplacements is to stop ships achieving low orbit and deploying ground forces/ dropping orbital bombardments on defensive positions/ formations or at least making it as difficult and costly as possible for the enemy. Like historical costal emplacements, if the enemy fleet has achieved orbital supremacy then the tide has already turned against the defenders and the goal is to stymie the inevitable orbital invasion. ie: you already lost the fleet battle and are on the back foot. 

 

To give an indication of the sheer scale of the weapons, think of the energy required to accelerate a 10+ ton shell with enough velocity to hit a target in low orbit, overcome the planet's gravity & air resistance and impart enough kinetic force to cause damage. Or for laser/ plasma weapons over come the refractive effects of the planet's atmosphere on particle and have enough energy to damage a target. We're looking at plasma reactors large enough to power a Retribution class battleship.

 

Hence why Legio Astartes orbital drop assaults are so effective, surface to ship weapons are designed to hit macro landers carrying Titan Demi Legios and ships several km long, not a drop pod hurtling to earth hundreds of miles and hour (which is where flak comes in, the ones which aren't knocked out by the orbital bombardment, which the surface emplacements are trying to prevent.)