Spacecraft, a vehicle designed to fly in or out of space, such as launch vehicles (space rockets), artificial Earth satellites (EAS) and other celestial bodies. The name CLA is generic and includes various types of such vehicles, including those using the nonreactive principle of motion (e.g., solar sail, etc.). Launch vehicles (space rockets) are a means of achieving the necessary speed for the space flight of CLA, which can be divided into 2 main groups: a) Earth-orbiting CLA, moving on geocentric orbits, not going beyond the Earth’s sphere of action (ISA); b) interplanetary CLA, which in flight go beyond the Earth’s sphere of action and enter the sphere of action of the Sun, planets or their natural satellites. At the same time there is a distinction between unmanned CLA (unmanned ISZ, artificial satellites of the Moon – ISL, Mars – ISM, the Sun – ISS, etc., automatic interplanetary stations – AMS) and manned (spacecraft-satellites, manned orbital stations, interplanetary spacecraft). Most of these types of spacecraft have already been created; the development of interplanetary spacecraft for flight and landing on other planets, reusable transport spacecraft, etc. is underway.

The flight of the spacecraft is divided into the following sections: withdrawal – the spacecraft is given the necessary space velocity in a given direction; orbital, during which the motion of the spacecraft occurs mainly by inertia, according to the laws of celestial mechanics; landing section. In some cases the spacecraft are equipped with rocket engines, which allow to change (correct) the trajectory of the spacecraft on the orbital section or to brake the spacecraft during the landing. For modern spacecraft, which use chemical rocket engines, the length of the flight segments with working engines (withdrawal, correction, braking) is much less than the orbital flight segments.

A rocket is the only available means of flight into space. A rocket’s maximum speed depends on the jet velocity determined by the type of propellant and the perfection of the engine, and the ratio of the propellant mass to the overall (initial) mass of the rocket, i.e. the perfection of the rocket’s design, as well as the mass of the payload. The jet velocity from the engine with modern chemical propellants is 3000-4500 m/s; herewith a one-stage rocket of a rational design is practically not capable of developing the velocity necessary for the space flight (about 8 km/s). Therefore rockets are divided into parts which are separated in flight as fuel is consumed (fuel tanks, engines). The main rockets used in astronautics (launch vehicles) have from 2 to 4 stages. The constructive schemes of these rockets are very diverse; their distinctive feature is a low relative weight of the structure (together with the propulsion system, it usually does not exceed 10-12% of the fuel mass). Creating such a structure with high stiffness and strength is a difficult technical task. The rocket operates under very high static and dynamic loads, so the maximum use of material strength and structural perfection of individual assemblies is required together with a considerable overall dimensions of the structure. A rocket equipment includes a number of systems and units for in-flight control, stage separation, fuel tank supercharging, regulation of fuel supply to engines, etc. The propulsion systems of a space rocket usually consist of several engines whose operation is synchronized.

The rocket flight along the pre-set trajectory, its stabilization relative to the center of mass, control of engines (thrust control, activation and deactivation) and issuance of commands for stage separation are provided by the control system. It represents a complicated complex of devices and units (gyroscopic, electronic, electromechanical, etc.) and in some cases includes an onboard electronic computer. Space rockets are one of the greatest achievements of modern science and technology; creation of rocket-space complexes requires a high level of development of many branches of science and technology – metallurgy, chemistry, radioelectronics, computer engineering and many others.