[Rockets] OROC Model Launch. Saturday, November 14th, 12-3pm. Memorial Park

Michael Ward michaelward at sprintmail.com
Sun Nov 22 15:05:45 PST 2009


Hi all,

Just in case you are interested in some specifics for the Nov. 14th
launches of the Red Devil (Estes Big Bertha modified to a 2 stage with
payload bay), I've attached links to:

* pictures of the rocket:
http://www.math2learn.org/index.php?option=com_phocagallery&view=category&id=3:rocketry&Itemid=61

* PerfectFlite Alt15K/WD altimeter readings
http://www.math2learn.org/files/RedDevil/20091114-1-D120C63.txt
http://www.math2learn.org/files/RedDevil/20091114-2-D120C65.txt

* a spreadsheet of trajectory calculations in Gnumeric & Excel format:
http://www.math2learn.org/files/RedDevil/RocketSimulate.gnumeric
http://www.math2learn.org/files/RedDevil/RocketSimulate.xls

The theoretical calculations (636 ft) are in the ballpark of the
altimeter data.  I have no idea how accurate the drag coefficient is.
In order to estimate the apogee, I plugged in the complete rocket
(RedDevil) with a D12, found the conditions at the point where the D12
engine stopped (~35 m/s, 36 m), and then switched over to calculations
for the 2nd stage (RedPheonix) with a C6 engine using conditions at the
cut-off of the D12 (~35 m/s, 36 m) as initial conditions.

The 1st stage has more cross sectional area than in the spreadsheet due
to the rubber band mechanisms on the fins.  It also had some extra
initial resistance due to rubbing on the launch rod (I think I fixed
that for the next launch).

Let me know if the spreadsheets don't work for you and you really want
to get them going. Here are some details:

stage 1: ht=8 3/4 in, wt=114g+41g x-sec-area=3.5 in^2 recovery=tumble
stage 2: ht=31 in, wt=143g+25g x-sec-area=3.5 in^2 recovery=chute
combined: ht=36 1/8 in, wt=257g+66g x-sec-area=3.5 in^2

The calculations (especially for air resistance) are based on:
http://www.apogeerockets.com/education/downloads/numeric_methods.pdf
http://www.esteseducator.com/Pdf_files/Part_1.pdf (parts 2,3,...)
http://www.engineeringtoolbox.com/air-altitude-density-volume-d_195.html

The engine thrust data is from (click on the engine description):
http://www.redarrowhobbies.com/estes_model_rocket_engines.htm

I'm planning to soon write an introduction to the calculations:
http://www.math2learn.org/index.php?option=com_content&view=article&id=48:rocket-trajectory-calculations&catid=35:applied-elemetary-math&Itemid=58

Enjoy,
- Mike



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