summaryrefslogtreecommitdiff
path: root/lv2c_launchdata-2010-06-27.mdwn
authornatronics <natronics@web>2010-07-14 00:22:06 (GMT)
committer Portland State Aerospace Society <psas@psas.pdx.edu>2010-07-14 00:22:06 (GMT)
commit0ee62220e07463c81f0c094f32c8403c993ad2ea (patch) (side-by-side diff)
treef9d0aa7d0be8b4c6c7205e120d8eac677a633d6f /lv2c_launchdata-2010-06-27.mdwn
parent27105b209768466b82ca27798a1590815d3390a4 (diff)
downloadwiki-0ee62220e07463c81f0c094f32c8403c993ad2ea.zip
wiki-0ee62220e07463c81f0c094f32c8403c993ad2ea.tar.gz
More data analysis
Diffstat (limited to 'lv2c_launchdata-2010-06-27.mdwn') (more/less context) (ignore whitespace changes)
-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.mdwn
index 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.