Space Flight

Newton's law of gravitation defines the attraction of gravitational force Fg between two bodies in space as follows:

Here G is the universal gravity constant (G = 6.670 x 10~n m3/ kg-sec2), and m2 are the masses of the two attracting bodies (such as the earth and the moon, the earth and a spacecraft, or the sun and a planet) and R is the distance between their centers of mass. The earth's gravitational constant /z is the product of Newton's universal constant G and the mass of the earth mi (5.974 x 1024 kg). It is n = 3.98600 x 1014 m3/sec2.

The rocket offers a means for escaping the earth for lunar and interplanetary travel, for escaping our solar system, and for creating a stationary or moving station in space. The flight velocity required to escape from the earth can be found by equating the kinetic energy of a moving body to the work necessary to overcome gravity, neglecting the rotation of the earth and the attraction of other celestial bodies.

By substituting for g from Eq. 4-12 and by neglecting air friction the following relation for the escape velocity is obtained:

D I 2g0

Here R0 is the effective earth radius (6374.2 km), h is the orbit altitude above sea level, and g is the acceleration of gravity at the earth surface (9.806 m/sec). The spacecraft radius R measured from the earth's center is R = R0 + h. The velocity of escape at the earth's surface is 11,179 m/sec or 36,676 ft/sec and does not vary appreciably within the earth's atmosphere, as shown by Fig. 4-6. Escape velocities for surface launch are given in Table 4—1 for the sun, the



Was this article helpful?

0 0
Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook

Post a comment