The thing about balloons is they're relatively cheap, and the stuff you put in them isn't expensive either. If you want to flirt with danger, hydrogen filled is

The thing about balloons is they're relatively cheap, and the stuff you put in them isn't expensive either. If you want to flirt with danger, hydrogen filled is one way to do it. The drone part is mostly to do with automation, as a terrestrial platform allows a lot of hands-on work to prep the rocket for launch. A high-altitude platform would have to be automated. Plus the way rocket physics work is the less fuel you need to punch through the atmosphere at speed, the less fuel you need overall, which reduces the weight of the rocket exponentially, as the fuel itself requires more fuel to get lifted. Anything they can do to get to a higher altitude without paying a heavy price is worth considering. Turning a theory into a viable launch strategy is not easy, I understand, but they've shown a remarkable ability to innovate.