The three-dimensional linear tangent guidance law (LTGL) has been
investigated and presented in this paper. The launch site is on the Taiwan
Island. In order to simulate the actual flight in the three-dimensional space,
the disturbance normal force considered is also three-dimensional. A
nominal trajectory is computed at first by using an assumed launch vehicle
(LV) model. With an assumed launch site located at (121.5 deg longitude,
22.5 deg latitude), the LV has the capability to insert a 1,000 kg satellite into
a 646.761 km altitude circular orbit. Then the deviated trajectory under the
disturbance of normal force is computed. And then the three-dimensional
LTGL is designed and implemented to guide the LV back to the nominal
trajectory. Two scenarios have been simulated for disturbance force acting
from different directions. Simulation results show that the absolute errors in
altitude and speed are within 3 km and 2 m/s, respectively. Therefore,
precise orbital insertion can be achieved.