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Calcimator

High-Power Certification Calculator

Plan your NAR/TRA Level 1, 2, or 3 certification flight. Predicts altitude, velocity, and Mach number from motor and rocket specifications.

Inputs

Results

Predicted apogee (ft)

742

Predicted apogee (m)226
Burnout velocity (m/s)57.3
Max Mach number0.17
Thrust-to-weight ratio3.71
Burn time (s)2.08
Altitude at burnout (m)60
Coast altitude gain (m)166
Cert LevelLevel 1
Motor LetterH
How to Use This Calculator
  1. Enter Rocket dry mass (kg), Motor total impulse (N-s), and Motor average thrust (N).
  2. Set Motor loaded mass (kg), Body diameter (mm), and Drag coefficient (Cd).
  3. Review the Predicted apogee (ft) result.
  4. Use Predicted apogee (m) and Burnout velocity (m/s) to inform your decision.

How the result changes with Rocket dry mass (kg)

Rocket dry mass (kg)Predicted apogee (ft)
5.09211
180
330
450

What each input means

Rocket dry mass (kg)
Rocket mass without motor (airframe, recovery, electronics).
Motor total impulse (N-s)
Total impulse from the motor data sheet. H=160-320, I=320-640, J=640-1280, K=1280-2560.
Motor average thrust (N)
Average thrust from the motor data sheet.
Motor loaded mass (kg)
Total motor mass including propellant and casing.
Body diameter (mm)
Rocket body tube outside diameter.
Drag coefficient (Cd)
Estimated total drag coefficient. Typical: 0.4-0.7. Use the Drag Coefficient calculator for a better estimate.

What each result means

Predicted apogee (ft)
Estimated peak altitude above ground level.
Predicted apogee (m)
Peak altitude in meters.
Burnout velocity (m/s)
Rocket speed at motor burnout.
Max Mach number
Peak velocity as fraction of speed of sound. Stay below Mach 0.8 to avoid transonic effects.
Thrust-to-weight ratio
Motor average thrust divided by liftoff weight. Minimum 5:1.
Burn time (s)
Motor burn duration (total impulse / average thrust).
Altitude at burnout (m)
Height gained during powered ascent.
Coast altitude gain (m)
Additional altitude gained after motor burnout during unpowered coast.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Rocket dry mass (kg) = 3, Motor total impulse (N-s) = 250, Motor average thrust (N) = 120, Motor loaded mass (kg) = 0.3 = 6 input(s) provided
  2. Calculate Predicted apogee
    Predicted apogee = totalAltitudeM * 3.28084
    742 = 742
  3. Calculate Predicted apogee
    Predicted apogee = burnoutAltitudeM + coastAltitudeM
    226 = 226
  4. Calculate Burnout velocity
    Burnout velocity
    57.3 = 57.3

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