Astronautics

Astronautics (alternatively also cosmonautics) is the theory and practice of navigation beyond Earth's atmosphere.

The term astronautics was coined by 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 once.

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 huge variations in temperature in very brief periods. Extreme constraints on mass cause astronautical engineers to face the constant need to save mass in the design in order to maximize the actual payload that reaches orbit.

The early history of astronautics is theoretical: the fundamental mathematics of space travel was established by Isaac Newton in his 1687 treatise Philosophiae Naturalis Principia Mathematica. Other mathematicians, such as Swiss Leonhard Euler and Italian Joseph Louis Lagrange also made essential contributions in the 18th and 19th centuries. In spite of this, astronautics did not become a practical discipline until the mid-20th century. On the other hand, the question of spaceflight puzzled the literary imaginations of such figures as Jules Verne and H. G. Wells. At the beginning of the 20th century, Russian cosmist Konstantin Tsiolkovsky derived the famous rocket equation, the governing equation for a rocket-based propulsion, based on the work of Pedro Paulet, enabling computation of the final velocity of a rocket from the mass of spacecraft ( $m_{1}$ $m_{1}$ ), combined mass of propellant and spacecraft ( $m_{0}$ $m_{0}$ ) and exhaust velocity of the propellant ( $v_{e}$ $v_{e}$ ).

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