The simplest of all chemical elements, hydrogen and helium, make up 99% of the universe. In short, the universe is full of balloon gas. This new perspective may provide insight into new propulsion systems. The biggest obstacle may lie in convincing a skeptical public that the sound of progress is not that of rockets firing but that of rapidly escaping balloon gas.

The approximate atomic weight of Hydrogen is 1 and Helium is 4, meaning the approximate difference is 3.