Astronautics is the theory and practice of navigation beyond the Earth’s atmosphere.
The term astronautics was coined in the 1920s by J.-H. Rosny, president of the Goncourt academy, in analogy with aeronautics. Because there is a degree of technical overlap between the two fields, the term aerospace is often used to describe both at the same time. In 1930, Robert Esnault-Pelterie published the first book on the new field of research.
As with aeronautics, the restrictions of mass, temperatures and external forces require that applications in space survive extreme conditions: high-grade vacuum, the radiation bombardment of interplanetary space and the magnetic belts of low Earth orbit.
Space launch vehicles must withstand titanic forces, while satellites can experience large temperature variations in very short periods. The extreme limitations of the mass make astronautic engineers face the constant need to save mass in the design to maximize the real load reaching the orbit.
The early history of astronautics is theoretical: the fundamental mathematics of space travel were established by Isaac Newton in his 1687 treatise Philosophiae Naturalis Principia Mathematica. Other mathematicians, such as the Swiss Leonhard Euler and the Franco-Italian Joseph Louis Lagrange also made essential contributions in the eighteenth and nineteenth centuries.
Despite this, astronautics did not become a practical discipline until the middle of the 20th century. On the other hand, the question of space flight baffled the literary imagination of figures such as Jules Verne and H. G. Wells.
At the beginning of the 20th century, the Russian cosmologist Konstantin Tsiolkovsky derived the famous rocket equation, the governing equation for a rocket-based propulsion, which allows to calculate the final velocity of a rocket from the mass of the spacecraft, the combined mass of propellant and spaceship.
Although many consider astronautics itself as a fairly specialized subject, engineers and scientists working in this area must be well informed in many different fields.
Astrodynamics: the study of orbital motion. Those who specialize in this field examine topics such as trajectories of spacecraft, ballistics and celestial mechanics.
Spacecraft propulsion: how spacecraft change their orbit and how they launch. Most spacecraft have a variety of rocket engines, so most of the research efforts focus on a variety of rocket propulsion, such as chemistry, nuclear or electric.
Spaceship design: a specialized form of systems engineering that focuses on combining all the subsystems needed for a particular launch vehicle or satellite.
Controls: keep a satellite or rocket in the desired orbit and orientation
Spatial environment: although it is more a subdiscipline of physics than of astronautics, the effects of space weather and other environmental problems constitute an increasingly important field of study for spacecraft designers.