JATO: Jet Assisted Take Off. It's indeed a solid fuel booster rocket. There's a myth that someone strapped one to a car, then crashed into a cliff...
As for the US vs German points of view, what I see in general is the stereotypical "bigger is better" for the US, and "less is more" for "Germany" (which is actually more European, not just German). Personally, I prefer the latter, but the way we get there, is by first pushing the extreme of "how big can we make it?".
For example, we've discovered that a massively large pump actually decreases performance, as it adds a significant amount of heat into a loop.
Similarly, I'm sure Zalman is discovering a number of interesting things from developing the huge "flower" HSF.