Table of Contents

Orbital Mechanics

Student Activity

Changing Orbital Inclination

Delta "v" problems are most easily solved by using simple scale drawings called vector diagrams.

1. Select an appropriate and convenient scale to represent the speed, such as 2cm = 1km/s

2. Lay out an "arrow" to represent the initial (old) velocity. The "arrow" points in the direction of the velocity.

3. Using a protractor and a ruler lay out a second arrow to indicate the final (new) velocity's direction and speed . Draw the new vector tail-to-tail with the initial velocity vector.

4. Draw in the delta "v" velocity (red in the diagram to the left). Using your speed scale and a protractor, measure this vector to compute the direction and speed change needed to achieve the new velocity.

1. Determine the delta "v" (change in velocity) required to accomplish the following orbital changes.

   • Change the orbital inclination from 51⁰ to zero 0⁰ in low Earth orbit where the orbital speed is 7.8km/s.

   • Change the orbital inclination from 51⁰ to zero 0⁰ in low geosyschronous orbit where the orbital speed is 3.2km/s.

2. Based on your calculations, is it better to change a satellite's orbital plane at it's apogee (highest point), or perigee (lowest point)?

3. Suppose an asteroid were discovered on a collision course with the Earth. If rockets could be used to nudge the asteroid into a new orbit by changing its orbital plane, when in its orbit would be the best time to try to affect this manoeuvre?

4. Comets usually have high orbital inclinations with respect to the Earth's orbital plane. Astronomers would like to send a space probe to visit a comet. To do this they send the space probe as far as possible away from the Sun before applying the change in its orbital plane to match the orbital plane of the comet. Why?

5. It is very difficult to send a space probe over the polar regions of the Sun, even at the Earth's distance. Why?