[jboot]

It's an Atlas V 531, one of 10 normal configurations (20 if there were ever a double Centaur flight):

It breaks down to:
5 = 5 meter diameter payload fairing.
3 = 3 SRBs
1 = Single-engine Centaur upper stage

[MarineBrat]

Interesting that there’s 3 SRB’s and yet they’re not symmetrically arranged. That’s a new one on me.

[GeorgeWashingtonsGhost]

Still a bummer we have to purchase the main engines from Russia.. (RD-180) Bad azz engines for sure.