I have never attempted relativistic calculations before and wondered if
I have this right.

I am currently reading John Ringo's 'Gust Front' in which a ground based
anti-starship weapon is described as firing bars of depleted uranium,
100mm in diameter and two metres long at a muzzle velocity of 0.3c.

I make this a KE of 1.302 exa-Joules, equivalent to a touch over 311MT
of TNT.  Is this right?  And would such a weapon system really be
feasible within an Earth-standard atmosphere?

Many thanks,

David Shaw