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deorb [2008/11/05 21:21]
christra
deorb [2008/11/06 15:06] (current)
christra
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 At some point down on the flightpath Shuttle starts to produce lift, the velocity is so high that just the angle of the shuttle is enough to produce a noticeable amount of lift. To prevent ditching and to manage the energy state the Shuttle is banked to one side quite steeply, but without reducing the AOA, it's a combined movement around all axes. Banking the Shuttle prevents the lift line from pointing up (and decreasing the sink rate) instead the lift is pointed sideways. The bank leads to a very slow course deviation. This allows the flight path to be lengthened in order to manage energy (the longer flight time allows more speed can be depleted by the high drag). Unfortunately,​ This causes the Shuttle to move off course and that needs to be corrected at some point, and this leads to a "roll reversal"​ - the Shuttle banks to the other side. Depending on the energy that is left there will be a few more rolls. Due to the shape of the generated flight path, these repeated turns/rolls are also known as "S turns"​. Throughout the Entry the onboard computers keep track and constantly update the flight path and the required maneuvers are executed by the Digital Auto Pilot (DAP). The Commander or the Pilot usually leave the task to the computers but can take control if needed. The screenshot below shows the shuttle during a right "​roll"​ and the arrows show the vectors of lift and velocity (movement). The angle α between the x-axis and the movement is the [[wp>​Angle_of_attack|Angle of Attack]]. In reality it is not exactly the x-axis but for our understanding it is good enough. It should be clear now that the direction where the nose points to and the direction of movement are different things. At some point down on the flightpath Shuttle starts to produce lift, the velocity is so high that just the angle of the shuttle is enough to produce a noticeable amount of lift. To prevent ditching and to manage the energy state the Shuttle is banked to one side quite steeply, but without reducing the AOA, it's a combined movement around all axes. Banking the Shuttle prevents the lift line from pointing up (and decreasing the sink rate) instead the lift is pointed sideways. The bank leads to a very slow course deviation. This allows the flight path to be lengthened in order to manage energy (the longer flight time allows more speed can be depleted by the high drag). Unfortunately,​ This causes the Shuttle to move off course and that needs to be corrected at some point, and this leads to a "roll reversal"​ - the Shuttle banks to the other side. Depending on the energy that is left there will be a few more rolls. Due to the shape of the generated flight path, these repeated turns/rolls are also known as "S turns"​. Throughout the Entry the onboard computers keep track and constantly update the flight path and the required maneuvers are executed by the Digital Auto Pilot (DAP). The Commander or the Pilot usually leave the task to the computers but can take control if needed. The screenshot below shows the shuttle during a right "​roll"​ and the arrows show the vectors of lift and velocity (movement). The angle α between the x-axis and the movement is the [[wp>​Angle_of_attack|Angle of Attack]]. In reality it is not exactly the x-axis but for our understanding it is good enough. It should be clear now that the direction where the nose points to and the direction of movement are different things.
  
-|{{:​rr ​right.jpg?​600|SSM2007 - Shuttle in right roll}}|+|{{:​rr.jpg?​600|SSM2007 - Shuttle in right roll}}|
 ^  SSM2007 screenshot of a Shuttle during a right roll.  ^ ^  SSM2007 screenshot of a Shuttle during a right roll.  ^
  
deorb.txt · Last modified: 2008/11/06 15:06 by christra