Space travel is one of the largest technological efforts and requires careful planning and a systematic approach in every technical and human aspect. In this chapter, a space mission example will be divided into four consecutive phases, starting with payload and launcher definition and ending with the launch of the rocket. The discussion of the first phase provides general considerations of manned and unmanned commercial missions, orbits, and trade-offs for small satellites. The subsequent phase covers transportation issues of the payload to the launch site. The discussion of the payload integration process and launch proceeding complete the technical contribution of the chapter. A rough market overview is presented in the conclusion.
TopBackground
From a classical viewpoint, a rocket consists of three main parts: the payload; the rocket engine; and the structure, which includes propellant, tanks, and avionics.
The payload is the raison d'être of any launch, representing the rocket's most valuable component. For institutional activities, it might be an Earth observation satellite for weather forecast or a navigation satellite for providing positioning signals (which our smartphones all utilize). For commercial activities, it might be a telecommunication satellite or even a human being in the case of tourism flights. Similar payloads can also be carried for military applications focusing on Earth surveillance, secure communication, and high-precision positioning.
If we look at ground transportation, it can be observed that every vehicle needs contact with the ground’s surface, represented for example by static friction between tires and asphalt, to push itself along. The absence of contact with firm-ground compels reliance on the reaction principle to move matter through air and outer space. In this connection, the vehicle ejects a previously stored substance in the opposite direction to that of the intended movement. Every rocket engine is thus designed to expel gasses at high velocities to generate a force, known as thrust, counter to the flight direction. The process involves converting propellants’ chemically bounded energy via combustion into thermal and ultimately the kinetic energy of hot exhaust gasses. To ensure efficient rocket-engine operation, combustion occurs at very high pressures and temperatures, burning up to several tons of propellant per second. For example, one of the biggest rocket engines ever build, the Rocketdyne F-1 – engine burns approx. 2605 kg of liquid oxygen and kerosene per second (Oefelein & Yang, 1993). Liquid-fuel rocket engines usually employ turbo pumps to feed propellants from tanks into a combustion chamber, where they burn and generate hot gases. A nozzle accelerates the hot gasses into the external environment at supersonic speed. Due to physical correlations according to the Tsiolkovsky equation, it is useful to strive for very light, reliable, and powerful engines to increase the lift capabilities of the entire rocket.
The rocket engine, propellant tanks, and the payload are integrated into the rocket structure. Regarding requirements imposed on mass, the rocket engineer’s challenge is to design very light structures, providing the necessary stiffness and maximal robustness for the construction. The vehicle’s mass decreases during flight due to the propellant consumption and ejection of hot gasses out through the nozzle. On the other hand, the mass of the tank containing the propellants remains constant. The tank’s mass is thus rendered superfluous after the rocket's engine has consumed all of the propellants to accelerate during flight. At a certain point, it becomes expedient to jettison the depleted tanks to decrease the system's mass. This procedure is better known as staging and is necessary for all space launchers to achieve Earth orbit.