There's actually a small Spanish company, Zero 2 Infinity, pursuing that seriously for small satellite launch and I was sort of surprised not to see them mentio

There's actually a small Spanish company, Zero 2 Infinity, pursuing that seriously for small satellite launch and I was sort of surprised not to see them mentioned in the article. As other replies mention, you don't save much in terms of overall energy by launching form higher up. However, there are three big pluses to launching from high up in the atmosphere. First, rocket engines are more efficient when they run in a vacuum than when they run at sea level. With SpaceX's Merlin rockets one running at sea level has an ISP of 282 but a vacuum optimized Merlin running in space has an ISP of 348 giving it almost a quarter more impulse for the same fuel expenditure. Second, you don't waste fuel fighting drag as you work your way up through the atmosphere. That can easily be 100s of m/s of delta-v wasted. Finally, launching higher up means saving weight on the rocket structures. You can make your rocket more nearly spherical and save weight on tank area. You can use a lighter tank structure since air resistance forces aren't an issue. And you can light your stages in parallel rather than series because they don't have to be stacked on top of each other or be optimized for different pressures. https://www.zero2infinity.space/ https://www.zero2infinity.space/