Model Rocket Altitude Predictor

Multi-Stage Version

Experimental

A user's motor version is also available.

ALL NEW MOTOR THRUST PROFILES

as of 26 April, 2004
Updated again with new Ellis Mountain motors and Revisied Loki Data on 13 December, 2004

Read about it at http://webalt.markworld.com/webalt.html
The old profiles are still available by using http://webalt.markworld.com/multistage1.html

This page drives a rocket simulation program which will project the peak altitude and other flight profile information about a multi-stage model rocket. A single stage version is available at http://webalt.markworld.com/webalt.html.
First read the disclaimer.
Then fill in the requested information about your rocket.
  • For each stage, you can select up to 3 motor sizes and specify a quantity of each size. Leave the quantity blank for unused motor sizes or stages.
  • Masses specify the launch mass of each stage and everything that will be lost when it is ejected. The sum of the individual stage masses entered should equal the launch mass of the entire vehicle including motors and propellants.
  • 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
First Motor Size
Quantity of First Size
Second Motor Size
Quantity of Second Size
Third Motor Size
Quantity of Third Size
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


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.

The program interpolates (linearly) between time/thrust data points in a motor-specific thrust profile. If you would like to see a motor added, Email the thrust profile as a set of time (in seconds) and thrust (in Newtons) data points in this format or try the user-entered thrust profile version of this program.

People often ask me the "formula" used by this calculator. Well, the best answer is F=MA. This calculator uses numerical integration which is how lazy programmers with fast computers do calculus. If you want to see how a real man does it, check Randy Culp's Analytical Solution! He's also done the math for the multi-stage case. Check Randy's Space Exploration Home Page for his latest.

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.

Email with comments, corrections, and bug reports.
Visit the Mark Sullivan home page for more technical hobby resources
or the Teeniemünde Rocketry Club