It's not a matter of the balloon being airtight. At some point , there simply is not going to be any air for the balloon to be less dense than. It's not going to to explode either. Weather balloons go up there regularly, and they don't explode.

Any balloon capable of hoisting a rocket capable of leaving the atmosphere would simply be too large to use. Rockets weigh tens of thousands, if not hundreds of thousands, of kilograms/pounds.

You would somewhere around 303 cubic kilometers of helium to lift a Falcon 9 rocket, for example.

A balloon just would not work.

Hi TeranAmbassador33

You are 100% Right ******** The Balloon Exploded Because it was not an Material Balloon Damn I am an idiot Why did I not think of that earlier There are alarm going off in my head saying ("You are the Biggest idiot on the Planet Research before you comment you moron") It seems I owe you an Apology Sorry. Here is the Footage I was telling you About On James Mays Man Lab The Balloon although filled with Hydrogen exploded because it was an ordinary Balloon. Here is the link

James Mays Man Lab Hot Hydrogen Balloon

Sorry for doubting and arguing about it with you I should have checked Before.

Karl

There's a white paper somewhere on the web titled "The Balloon Assisted Launch System - A Heavy Lift Balloon" by Debora Grant and James Rand. I haven't been able to see more than the first page, but it looks interesting. Also take a look here and here. The biggest difference I see is that these guys are talking mostly about microsatellites and other tiny payloads, which you could launch with much smaller rockets from a balloon. 

Thanks regulus

That looks really cool I hope they manage to do it one day. I am surprised thought that a normal hydrogen filled balloon got so high and the same goes for the helium balloon(it didn't get as high).

As costly as they are, they are still necessary and still the most viable option for launching space ships and robots to view life in outer space. It will take a while before a cheaper option is created because gravity is a real pain.