Getting to space has never been simple. A standing army of thousands is needed to launch the space shuttle, land it safely, and refurbish it so it is once again ready for flight.
And even the most basic space rockets require multiple stages, whose weight is mostly taken up by oxidisers needed to burn fuel. Rockets launch vertically to minimise the time they spend where Earth's gravity is strongest and shed stages to reduce their weight as they climb.
For decades, engineers have dreamed of a better way: a single-stage-to-orbit vehicle that would be lighter, cheaper, and easy to reuse. A fleet of these vehicles, supporters say, could be almost as easy to maintain as conventional jet planes, reducing the preparation time before each launch from months to days or even hours.
Since most of a rocket's weight is taken up by oxidiser, one logical approach is to save weight by developing an engine that can use oxygen from the atmosphere to burn fuel at least part of the way.