Rocket, Multistage

a rocket that, as its propellant is expended in the course of the flight, jettisons each successive structural element (rocket stage) that has been used and is not needed for further flight. The first-stage engine, which is capable of lifting and accelerating the entire rocket to a given speed, operates during the launching. When the principal supply of fuel has been consumed, the first-stage engine together with the structure that contains the empty tanks is jettisoned. The flight continues with the operation of the second-stage engine, which has a lower thrust but is capable of imparting added speed to the lightened rocket. When the fuel of the second stage has been expended, the third-stage engine cuts in and the second stage is jettisoned. This process could, in theory, be continued further, but structural complexity imposes a practical limit on a multistage rocket of two to four stages.

Multistage rockets may be constructed with the stages in a series or a parallel arrangement. In a series, or tandem combination, which is the most common, each individual stage is first exhausted and then jettisoned, whereupon the engine of the next stage is ignited. In a parallel, or cluster, arrangement, the individual stages and their engines and fuel tanks can operate simultaneously. Other arrangements are also possible, such as the first and second stages in parallel and the second and third in series. A single-stage rocket of efficient design is virtually incapable of developing the speed needed to launch a spacecraft into a near-earth orbit (approximately 8 km/sec).

Multistage rockets were first mentioned in the 1500’s by V. Biringuccio and in the 1600’s by K. Semenavicius. In the 1900’s, R. Goddard, H. Oberth, and A. A. Shternfel’d were studying the problems of using multistage rockets. The concept of a multistage rocket was most fully elaborated by K. E. Tsiol-kovskii in his Rocket Trains (1929) and Maximum Rocket Speed (1935). In these works, Tsiolkovskii presented the first scientific design and construction principles for multistage rockets. More thorough mathematical study of the problems of multistage rockets continued into the 1950’s, when the problems in the design and construction of multistage rockets represented urgent, practical tasks in science and technology.