Page 63 - Intro to Space Sciences Spacecraft Applications

50 Introduction to Space Sciences and Spacecraft Applications
- - (2-20)
AvlHobinann - 'Ptransfer orbit vcirclow orbit
At the transfer orbit apogee, the Av required to enter the circular higher
orbit would be:
(2-21)

Simple Plane Changes. A simple plane change only changes the inclina-
tion of the orbit and does not affect the other orbital characteristics. Plane
changes must also be done at the intersection of the initial orbit and the
desired orbit, as depicted in Figure 2-12. The Av required for a simple
plane change can be found from:

Ai
Avsirnple plane change = 2v sin - (2 - 22)
2

where v represents the orbital velocity and Ai is the change in inclination.
An important point that should be realized from equation 2-22 is that
plane changes performed at low orbital velocities minimize the required
Av. This suggests that plane changes should be performed at high altitudes
or at points of lowest velocity. It should also be realized that plane
changes in general are expensive in terms of Av. Equation 2-22 shows that
a plane change of 60" requires a Av equal to the orbital velocity itself!

initial
orbit

*"applied at
intersection
of orbits f%l = IT*!

Figure 2-i2. Plane change. Plane change maneuvers are performed over
the equator where the two orbital planes intersect.