So we all know the traditional way to get into space is via a huge gas guzzling rocket that belches out flames, exhaust, and other potential pollutants. 

So here is my proposal: we use balloons to get our rockets to the edge of space and only then do we fire up the engine. My guess is that this will limit pollution and noise to the surrounding areas and will save on fuel. 

So my question is: why are we not doing this? Is there some kind of limitations that I'm not thinking of? I realize lighter than air craft don't work when there is no air, but that shouldn't keep us from using this to get to the edge of the atmosphere right?