SpaceX is very, very far ahead of the field, although it's not quite obvious at the moment, though it will be soon. You see, there are two ways to build reusab

SpaceX is very, very far ahead of the field, although it's not quite obvious at the moment, though it will be soon. You see, there are two ways to build reusable rockets. One way is to build a purely reusable vehicle from the ground up, but this is extraordinarily expensive because of all the testing involved before it can be used commercial. The other is to build an expendable/reusable hybrid. A rocket that can be used in an expendable configuration but has all of the needed elements to allow for reusability down the road. This is vastly easier because it means you can bootstrap development on the back of commercial launch business, and do testing that is largely subsidized by paying customers. And this is what SpaceX has been doing. However, there's a problem. You have to head into reusability from the get go, you can't just modify any old rocket for reusability, you need to design from a place of suitability for reuse from square one. And while that's not an enormous difficulty it is very much non-trivial, and imposes a substantial overhead on R&D and manufacturing costs. This is because most of the optimizations for building a purely expendable rocket drive the design away from the optimizations you'd want for a reusable rocket. In an expendable design it's common for there to be a mix of propellants and a diversity of engine designs between the first and upper stages, it's also common for the upper stage to be more expensive than the first stage, because that stage is more critical for payload performance and launch precision. Also, it's common to minimize the number of engines on the first stage. Even the Saturn V had only 5 first stage engines. And generally there'd be no reason to add first stage engine restart capability on an expendable vehicle. All of those things results in an expendable vehicle that is completely unsuited to reuse. It leads to a first stage that is very difficult to modify for reuse, and an overall rocket design that does not reward the easiest type of reuse (of the first stage) because most of the cost is in the upper stage anyway. SpaceX went to a great deal of effort to ensure that they built a rocket that could serve the expendable launch market immediately (and pull in hundreds of millions of dollars in revenue) while also being suitable for reuse with comparably moderate modifications. The first stage has 9 engines, so throttling down to a thrust level suitable for precision landings of a mostly empty stage is possible by using only one engine. The first stage use restartable engines (using onboard TEA/TEB igniters). And the first stage is about 3/4 of the hardware cost of the vehicle, since the 2nd stage uses only one engine and is also LOX/Kerosene fueled. That foresight has allowed SpaceX to be in the launch business for several years, proving the capability of the company and gaining much needed experience in building and flying rockets while also poising the company to bring to market a reusable launcher. In comparison, every other established launch provider in the world could only do reusability by designing a new launcher from scratch.