Tell me why it wouldn't be possible to go to space like this:

Jet fuel is expensive, so what if you use some sort of weather balloon? Of course the weather balloon pops at a certain altitute because the pressure inside is greater than the pressure outside. So what if you do some sort of vent that lets the floating gas escape slowly to prevent the balloon from popping? Wouldnt you go higher and higher? And then you would only need some fuel for the last few miles instead of from off the ground

thanks