Editing Orbit insertion

'''Orbit insertion''' is the task for entering a desired stable [[orbit]] after [[launch]] or arrival in the [[sphere of influence]] of another [[celestial body]].

==Orbit insertion after launch==
After launch, the important task is to avoid all obstacles on the way to the desired orbit:
* [[Atmosphere]]
* Terrain

===Direct ascent===
[[Image:DirectInsertion.png|thumb|right|100px|Direct Ascent]]
The simplest way to to fly at a point on the new orbit and accelerate to the [[orbit velocity]] at this point in one powered phase. This is a preferred strategy for rocket stages with engines, which can't be restarted, but causes very high [[gravity losses]]. 

===Two-Burn strategy===
[[Image:2burnOrbitIns.png|thumb|right|100px|Two-burn orbit insertion]]
For reducing gravity losses, one way is to aim for inserting into a nearly stable orbit just above the obstacles (for example 130 km for earth or  15 km on the moon), which has its apogee at a point of the target orbit. A second burn matches the velocity vector to the orbit velocity of the target orbit.

===Example: Shuttle Ascent===
[[Image:ShuttleAscentOMS1.png|thumb|right|100px|Classic Space Shuttle Ascent]]

The ascent trajectory of the Space Shuttle is full of examples how safety constraints influence the maneuvers. The initial ascent trajectory is shaped to send both ET and Shuttle on a trajectory after [[MECO]], that allows the ET to crash over a small region in the Indian Ocean, while giving the Shuttle still the opportunity to return to KSC in a [[Abort Once Around]] maneuver, should the first burn of the OMS engines (OMS-1) fail. The OMS-1 raises the apogee from the initial low apogee to the target orbit. At the new apogee, about 45 minutes later, the OMS-2 inserts the Shuttle Orbiter into its desired trajectory. Should the OMS-2 fail, the shuttle could still be maneuvered to a safe reentry before it's orbit would have decayed to a uncontrolled reentry over the course of the next few days.