#### tpw2000

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- Thread starter tpw2000
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Also, you can get a good, basic sim for the purposes of altitude and delay timing on http://thrustcurve.org.

D = Cd A (.5 * rho * V^2)

where Cd= drag coefficient

A = cross sectional area

rho= density of the fluid

V = velocity

If you know the drag, you can solve for the Cd. Typically, drag coefficients can be looked up in a reference book. The drag coefficient may be a function of the velocity or Reynolds number, but is probably pretty much a constant for incompressible flow. For compressible flow the drag coefficient may be expressed as a function of Mach number. I remember that there was a very good reference book by Hoerner on drag coefficients for many different objects (including unusual things like the Statue of Liberty), but the book is hard to find.

I have an old report from Estes TR-10 "Model Rocket Altitude Prediction Charts including Aerodynamic Drag" by Douglas J. Malewicki that derives analytical formulas from differential equations for finding apogee for the coast phase after motor burn-out. You would still need an estimate of the rocket velocity at burn-out (which can be done). The calculations can be done by hand, but you need to be good at math. This paper might be available from the NAR website.

Also, more information can be found here:

http://www.rocketmime.com/rockets/rckt_eqn.html

Also, more information can be found here:

http://www.rocketmime.com/rockets/rckt_eqn.html

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Is there documentation for the formulas that open rocket uses?

Looks like it might be in here: http://openrocket.sourceforge.net/documentation.html

Or use Openrocket or Thrustcurve like I do!

https://www.apogeerockets.com/education/downloads/Newsletter438.pdf

Yes: Estes TR-10 or Centuri-TIR-100 Altitide Prediction Charts. Both were first issued in the early 1970's but are still available from several sources. I still have my original copies for back in the day which I use often.I have an old report from Estes TR-10 "Model Rocket Altitude Prediction Charts including Aerodynamic Drag" by Douglas J. Malewicki that derives analytical formulas from differential equations for finding apogee for the coast phase after motor burn-out. You would still need an estimate of the rocket velocity at burn-out (which can be done). The calculations can be done by hand, but you need to be good at math. This paper might be available from the NAR website.

Also, more information can be found here:

http://www.rocketmime.com/rockets/rckt_eqn.html

Below are a couple pages from Both Centuri TIR-100 & Estes TR-10, Hope they help a little

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To Aerostar:

That's EXACTLY what I was looking for! And surprisingly little hardcore algebra, just a lot of plug-in data.

As far as everyone else:

Super helpful, all of you guys. Much more so than in other hobbies (which I won't name)!

That's EXACTLY what I was looking for! And surprisingly little hardcore algebra, just a lot of plug-in data.

As far as everyone else:

Super helpful, all of you guys. Much more so than in other hobbies (which I won't name)!

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jcrocket.com/flight-physics.shtml

The simple simulator used in ThrustCurve.org is public as well:

github.com/JohnCoker/thrustcurve3/tree/master/simulate/flightsim