Watching the Antares launch for Orb-1 mission of Cygnus, I was thinking about the booster.
First stage is built in Ukraine by the company that makes the Zenit. They use the NK-33 engine, (Called an AJ-26 in the US) built in the 1960's (!! Yes, engines could be older than most of the people working on the project) for the Soviet N-1 Moon launch vehicle.
Second stage is stranger, to me, if you can believe it! They use ATK Castor solid rockets.
Thus the question, if the first stage has a 'burp' for some reason and say first stage thrust is low, or high, or 'wrong', and you fire your second stage solid, how do you correct?
When the SpaceX Falcon 9 'burped' an engine on a flight, they throttled up the other 8 engines and basically burned a little bit longer.
The second stage had some level of throttle control and timing control to adjust for that to keep the mission on track. (The secondary payload for Orbcomm that was lost, was not deployed, because of NASA rules on orbits that approach the ISS, where they are super picky and strict).
What would Orbital do, with a solid second stage in that case? You get two options. On, and burned out. Do you have to use an upper (third or payload based) stage to correct any variations?