Satellites are launched from the Earth's surface by means of multi-stage rockets.After ignition of the first stage rocket Engines,these Launch vehicles first ascent vertically, A few seconds after lift-off ,the rocket is tilted and it flies a curved trajectory until the satellite reaches the predetermined position called ascend trajectory.
since its a vast topic, we discuss only the types of ascent trajectories here.
Two basic types of ascent trajectories can be distinguished for satellite launch vehicles,
1.Direct Ascent ,
2.Hohmann Transfer Ascent.
1.Direct Ascent ,
In Direct Ascent the trajectory selected such that destination point lies in the required orbit, the satellite which in most cases is attached to the final rocket stage, approaches this destination altitude , the final stage stage motor is ignited and the satellite is accelerated to the required orbital velocity.In some cases the rocket motor required for this acceleration is not the motor of last stage, but is an integral part of satellite itself.
2.Hohmann Transfer Ascent.
In Hohmann transfer orbit , the satellite and the last stage of rocket first attains a low altitude circular parking orbit,just outside the densest part of atmosphere, usually this orbit is about 200 km or more, In most launches this altitude is taken to be 185km , shortly after parking orbit injection ,the vehicle is injected into an elliptic transfer trajectory , at perijee , this transfer ellipse is tangential to the parking orbit and at apogee tangential to the required satellite orbit. This transfer orbit is proposed by W.Hohmann , therefore is called "Hohmann transfer trajectory"
since its a vast topic, we discuss only the types of ascent trajectories here.
Two basic types of ascent trajectories can be distinguished for satellite launch vehicles,
1.Direct Ascent ,
2.Hohmann Transfer Ascent.
1.Direct Ascent ,
In Direct Ascent the trajectory selected such that destination point lies in the required orbit, the satellite which in most cases is attached to the final rocket stage, approaches this destination altitude , the final stage stage motor is ignited and the satellite is accelerated to the required orbital velocity.In some cases the rocket motor required for this acceleration is not the motor of last stage, but is an integral part of satellite itself.
In Hohmann transfer orbit , the satellite and the last stage of rocket first attains a low altitude circular parking orbit,just outside the densest part of atmosphere, usually this orbit is about 200 km or more, In most launches this altitude is taken to be 185km , shortly after parking orbit injection ,the vehicle is injected into an elliptic transfer trajectory , at perijee , this transfer ellipse is tangential to the parking orbit and at apogee tangential to the required satellite orbit. This transfer orbit is proposed by W.Hohmann , therefore is called "Hohmann transfer trajectory"
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