Astronautics, or astronautical engineering, is the branch of aerospace engineering that deals with machines designed to exit or work entirely beyond the Earth's atmosphere. In other words, it is the science and technology of space flight.
The term astronautics was coined by analogy with aeronautics. As there is a certain degree of technology overlapping between the two fields, the term aerospace is often used to describe them both.
As with aeronautics, the restrictions of mass, temperatures, and external forces require that applications in space survive extreme conditions: highgrade vacuum, the radiation bombardment of interplanetary space, 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.^{[1]} 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.
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The early history of astronautics is theoretical: the fundamental mathematics of space travel was established by Isaac Newton in the 17th century in his treatise Principia.^{[2]} Other mathematicians, such as Euler and Lagrange also made essential contributions in the 18th and 19th centuries. In spite of this, Astronautics did not become a practical discipline until the mid20th century. On the other hand, the question of space flight tickled the literary imaginations of such figures as Jules Verne and HG Wells.
At the beginning of the 20th century, Konstantin Tsiolkovsky derived the famous rocket equation, the governing equation for a rocketbased propulsion. This equation makes it possible to compute the final velocity of a rocket from the mass of spacecraft(m_{1}), combined mass of propellant and spacecraft (m_{0}) and exhaust velocity of the propellant (v_{e}).
For more information on the mathematical basis of space travel, see space mathematics.
By the early 1920s, the American Robert Goddard was developing liquidfueled rockets, which would in a few brief decades become a critical component in the designs of such famous rockets as the V2 and Saturn V.
Although many regard Astronautics itself as a rather specialized subject, engineers and scientists working in this area must be knowledgeable about many distinct fields of knowledge.
