Brock and Gary are engineers onboard the Nexus Starship. They are seen in an Out Of Bounds area during the tutorial and can be spoken to upon later return. They are seen in both modes trying to fix a turbine engine. They have a lot of Missions. Most are daily but others are not.
Build the Rocket - Smash some Maelstrom Generators and collect parts (daily)
Purchase Those Rockets - Find a Model Vendor and buy two Rocket Modules (cockpit and nosecone)
Their names are references to characters from Shangri-La in Black Ops.