I think you are right about "launching" Chris - it is just how you choose to express it that is going to be tricky. Basically they are talking about the relay race and the baton change and how when they hand over the baton then they are doing it at speed to launch the other one forward in the next leg of the relay. It sounds a bit funny that both of them are "launching" each other and I presume that they just mean one of them (the other one is supposed to slow down and not get launched!) but I suppose each gets launched at their respective start of the relay leg if you see what I mean. I think you are going to have to hack it around a bit in English- I would go for something like "two individuals who come together at a really short but vital moment to become one and launch one off/give blast off to the runner of the next leg" or ".... to become one as they hand over the baton and the runner of the next leg is launched off" - ugly but I am sure you can make it sound more English.