Multistage rocket
A rocket that sheds the parts whose fuel is spent as it flies. With that weight gone, the remaining stages accelerate faster.
By the rocket equation, the speed a rocket can gain is set by the ratio of its starting weight to its burnt-out weight. Carrying empty tanks and engines all the way is wasteful; drop them partway and the same fuel yields far more speed. Konstantin Tsiolkovsky worked the idea out in detail in a 1929 book, describing rocket trains: several rockets coupled together and cast off in turn[1].
Reaching orbit round the Earth takes about 8 kilometres per second, which is extremely difficult for a single stage burning today's chemical fuels. Almost every working rocket therefore has two or three stages. Discarded stages are thrown away, so recovering and reusing them has become the key to cheaper launches.
Related terms
- Rocket equationThe equation stating that a rocket's gain in speed depends on its exhaust velocity and on the ratio of its starting mass to its burnt-out mass.
- Reusable rocketA rocket that is recovered after launch, serviced and flown again. Not throwing the vehicle away brings down the cost of launch.
- Liquid-propellant rocketA rocket that burns liquid fuel and oxidiser fed into a combustion chamber. The burn can be throttled, stopped and restarted.
On the timeline
Sources
- K. E. Tsiolkovsky, “Космические ракетные поезда (Cosmic Rocket Trains),” Kaluga (book) (1929).