Model Rocket Altitude Predictor

User Motor Version

Experimental

This page drives a rocket simulation program which will project the peak altitude and other flight profile information about a model rocket given some vehicle parameters and a simplified thrust profile. A version with common commercial motors built-in is available at http://webalt.markworld.com/multistage.html.
First read the disclaimer. Then fill in the requested information about your rocket.

For each stage, you may enter two thrust level and burn duration pairs. If your motor is constant thrust (i.e. a liquid), leave the sustain phase blank and enter your thrust and duration as the boost phase parameters. Leave both phases blank for unused stages.
The propellant mass includes propellant for both phases. Propellant mass will be consumed proportionally to impulse delivered over time.
Masses specify the launch mass of each stage including propellant and everything that will be lost when that stage is ejected. The sum of the individual stage masses entered should equal the launch mass of the entire vehicle including all propellant.
Staging delays are specified in seconds from stage start. A stage ejects and the next stage ignites after this delay.
Cd for each stage is the entire vehicle including that stage.

When all appropriate data is filled in, click the LAUNCH button to start the simulation and receive the results.

Rocket Name
Body Diameter	millimeters
	First Stage	Second Stage	Third Stage
Boost phase thrust			Newtons
Boost phase duration			seconds
Sustain phase thrust			Newtons
Sustain phase duration			seconds
Propellant mass	grams	grams	grams
Staging Delay	seconds	seconds
Mass	grams	grams	grams
Cd
Parachute Delay	seconds from launch (optional)
Chute Diameter	millimeters (required only if ejection delay specified)
Launch Angle	degrees from vertical
Launch Altitude	meters MSL

Not sure what to use? Me neither!

This simulation uses a number of approximations to simplify the amount of data you have to input. For instance, there is no attempt to simulate the effects of winds and the drag of your rocket is calculated with a simplified transonic drag model. A better multi-stage simulation would also use the length of each stage to evaluate friction drag along the body tube.

The default Cd of .75 should be pretty close for a typical, rocket-shaped, model vehicle with three or four average sized, airfoil fins a good smooth finish and a typical launch lug. For other vehicle geometries, you may need to supply a different Cd. See John S. DeMar's excellent Model Rocket Drag Analysis for more information.

Disclaimer:
Because of the approximations used, the large number of uncontrolled real-world variables influencing rocket trajectory, and the very high probability that there are bugs in this experimental program, I cannot accept any liability for the failure of your actual rocket flight to conform to this projection.

Claimer:
I hope you enjoy the program and let me know how its projections match any actual flight measurements you may make.

with comments, corrections, and bug reports.
Visit the Mark Sullivan home page for more technical hobby resources.