Difference between revisions of "Orbit insertion"
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===Direct ascent=== | ===Direct ascent=== | ||
[[Image:DirectInsertion.png|thumb|right|100px|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 | + | 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 that can't be restarted, but causes very high [[gravity losses]]. |
===Two-Burn strategy=== | ===Two-Burn strategy=== | ||
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[[Image:ShuttleAscentOMS1.png|thumb|right|100px|Classic Space 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 | + | 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 its orbit would have decayed to a uncontrolled reentry over the course of the next few days. |
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Latest revision as of 11:10, 15 October 2022
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[edit]
After launch, the important task is to avoid all obstacles on the way to the desired orbit:
- Atmosphere
- Terrain
Direct ascent[edit]
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 that can't be restarted, but causes very high gravity losses.
Two-Burn strategy[edit]
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[edit]
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 its orbit would have decayed to a uncontrolled reentry over the course of the next few days.