Astrophysics

Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature and chemical composition) of astronomical objects such as stars, galaxies, and the interstellar medium, as well as their interactions. The study of cosmology is theoretical astrophysics at the largest scales.

Astrodynamics

Main article: Astrodynamics

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Astrodynamics is the branch of celestial mechanics concerned with the motion of rockets, satellites and missiles. It is based upon Newton's laws of motion, and law of universal gravitation. The formula for escape velocity is defined in astrodynamics as: vgeqsqrt{2 G M / r} Astrodynamics is also used to compute the position of a satellite at a given time, a problem first solved by Johannes Kepler, who computed the formula:

Related Topics:
Astrodynamics - Newton's laws of motion - Law of universal gravitation - Escape velocity - Johannes Kepler

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MT = E - e sin E ;

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This formula is commonly referred to as Kepler's equation, and can compute the time required for a satellite to travel from periapsis P to a given point S.

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Modern techniques for computing time-of-flight include the patched conic approximation, where one must choose the one dominant gravitating body in each region of space through which the trajectory will pass, and to model only that body's effects in that region, or the universal variable formulation.

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