One of the main armaments of UNSC ships is nuclear weaponry but how do they work? A Nuclear weapon in atmosphere does great damage due to the shock wave and expansive heat. However in space there would be no medium for the shock wave and heat this greatly diminishes the effect of a nuclear weapon. How do the UNSC get around this?
by launching the warheads at enemy ships so that they penetrate and so produce a shock wave within the ship. the enemy vessel will also conduct alot of heat from the explosion
> by launching the warheads at enemy ships so that they penetrate and so produce a shock wave within the ship. the enemy vessel will also conduct alot of heat from the explosion
However it has been described that the UNSC has used nukes to crack a Covenant ships shields , how would they do that?
> > by launching the warheads at enemy ships so that they penetrate and so produce a shock wave within the ship. the enemy vessel will also conduct alot of heat from the explosion
>
> However it has been described that the UNSC has used nukes to crack a Covenant ships shields , how would they do that?
as the shields form a sort of fake solid surface of energy I would guess the same physics would apply. if not then it may just be that the stress of keeping the radiation and heat from the reaction would cause the shields to collapse.
Well a certain amount of energy from a nuclear explosion can be carried through space in the form of radiation. So that can severly damage the covenant ship as well as the emp that can take down the shields.
> Well a certain amount of energy from a nuclear explosion can be carried through space in the form of radiation. So that can severly damage the covenant ship as well as the emp that can take down the shields.
completely forgot about the EMP.
emp not E.M.P. 
> emp not E.M.P.
silly me
They use multiple Nukes at once.
Nuke#1 is prematurely Detonated to make the EMP take down the shields.
Nuke#2-4 is used to melt the hull
Nuke#5 is used to blow up inside the ship.
Something similar to that, Obviously the numbering is off; but you should get what Im getting at.
All the energy is released as gamma rays and relativistic neutrons. If the bomb is detonating right on the surface of the shield, then that is a full half of the energy being absorbed by the shields surface. (The other half radiating away into space). If it hits the hull, then the radiation simply disintegrates the hull material, and causes rapid thermal expansion of plasmas from the vaporized materials which causes further damage. It would also cause the ship’s structure to buckle from the thermal expansion of large portions of its hull that was not vaporized.
Looks like you guys already touched on it, but there is a whole host of electromagnetic radiation (in addition to sound, for example) that is released in a nuclear detonation. 