Replacement Vulcan test launch with inert payload, experiments, and demonstrations for certification with the USSF after delays caused by payload testing of the Sierra Space Dreamchaser CRS SNC-1 mission, the original planned payload.
Actually rewatching it, it looks like might have been a nozzle failure on one of the GEMs. There's a big flare before clouds obscure the rocket - much bigger than the ice. After this, one side looks to have a bigger exhaust plume than the other, and burns out slightly sooner.
The ULA launch team is authorized to begin cryogenic propellant loading operations as today's #VulcanRocket countdown proceeds on schedule. Weather is 80% favorable to launch the #Cert2 mission at 6:00amEDT (1000 UTC).