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author committer natronics 2010-07-14 00:22:06 (GMT) Portland State Aerospace Society 2010-07-14 00:22:06 (GMT) 0ee62220e07463c81f0c094f32c8403c993ad2ea (patch) (side-by-side diff) f9d0aa7d0be8b4c6c7205e120d8eac677a633d6f 27105b209768466b82ca27798a1590815d3390a4 (diff) wiki-0ee62220e07463c81f0c094f32c8403c993ad2ea.zipwiki-0ee62220e07463c81f0c094f32c8403c993ad2ea.tar.gz
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-rw-r--r--lv2c_launchdata-2010-06-27.mdwn18
1 files changed, 18 insertions, 0 deletions
 diff --git a/lv2c_launchdata-2010-06-27.mdwn b/lv2c_launchdata-2010-06-27.mdwnindex 36387b8..6dd1ee4 100644--- a/lv2c_launchdata-2010-06-27.mdwn+++ b/lv2c_launchdata-2010-06-27.mdwn@@ -200,3 +200,21 @@ Here is a close up of just during the burn. Taking our binned/averaged data we can integrate to find the velocity at each point: [[!img velocity.png size="650x650"]]++### Drag++After the motor burns out we should be able to find all the forces on the rocket; drag and gravity. Gravity is easy to predict and knowing the mass and acceleration we can solve for drag force:++[[!teximg code="F_d = ma - mg" ]]++[[!img drag.png size="650x650"]]++Knowing the Drag force, height of the rocket, and velocity of the rocket we can estimate the Cd empirically. We simply solve for Cd.++[[!teximg code="F_d = \frac{1}{2} \rho v^2 C_d A" ]]++[[!teximg code="C_d = \frac{2 F_d}{\rho v^2 A}"]]++[[!img drag_cd.png size="650x650"]]++This technique does not appear to work very well, unless OpenRocket is just very wrong about drag. Which is possible. The technique is very sensitive to having the correct velocity.