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Calcimator

Dual Deploy Calculator

Size drogue and main parachutes for dual-deployment recovery. Calculates chute diameters, descent times, opening shock, and black powder ejection charges.

Inputs

Results

Drogue diameter (in)

10.3

Main chute diameter (in)

45.6

Drogue diameter (cm)26.1
Main chute diameter (cm)115.9
Total descent time (s)64
Main opening shock (G)29.6
Drogue BP charge (g)1.05
Main BP charge (g)1.57
Landing energy (J)20.3
How to Use This Calculator
  1. Enter Rocket mass (kg), Expected apogee (m AGL), and Main deploy altitude (m AGL).
  2. Set Drogue descent rate (m/s), Main descent rate (m/s), and Compartment diameter (mm).
  3. Adjust Compartment length (mm) as needed.
  4. Review Drogue diameter (in) and Main chute diameter (in).
  5. Use Drogue diameter (cm) and Main chute diameter (cm) to inform your decision.

How the result changes with Drogue descent rate (m/s)

Drogue descent rate (m/s)Drogue diameter (in)Main chute diameter (in)
8.524.145.6
1712.145.6
287.345.6
375.545.6

What each input means

Rocket mass (kg)
Total rocket mass at recovery (after burnout).
Expected apogee (m AGL)
Peak altitude above ground level.
Main deploy altitude (m AGL)
Altitude at which the main parachute deploys. Typical: 150-300m.
Drogue descent rate (m/s)
Target descent rate under drogue. Typical: 15-25 m/s.
Main descent rate (m/s)
Target final descent rate under main. Typical: 3-5 m/s.
Compartment diameter (mm)
Inner diameter of the ejection compartment (body tube ID).
Compartment length (mm)
Length of the sealed ejection compartment.

What each result means

Drogue diameter (in)
Required drogue parachute diameter.
Main chute diameter (in)
Required main parachute diameter.
Drogue diameter (cm)
Drogue diameter in centimeters.
Main chute diameter (cm)
Main chute diameter in centimeters.
Total descent time (s)
Time from apogee to landing.
Main opening shock (G)
Deceleration when main chute opens, in multiples of gravity.
Drogue BP charge (g)
Recommended black powder mass for drogue ejection.
Main BP charge (g)
Recommended black powder mass for main ejection.
Landing energy (J)
Kinetic energy at touchdown. Keep below 75 J.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Rocket mass (kg) = 2, Expected apogee (m AGL) = 600, Main deploy altitude (m AGL) = 200, Drogue descent rate (m/s) = 20 = 7 input(s) provided
  2. Calculate Drogue diameter
    Drogue diameter = drogueDiameterM * 39.3701
    10.3 = 10.3
  3. Calculate Main chute diameter
    Main chute diameter = mainDiameterM * 39.3701
    45.6 = 45.6
  4. Calculate Drogue diameter
    Drogue diameter = drogueDiameterM * 100
    26.1 = 26.1
  5. Calculate Main chute diameter
    Main chute diameter = mainDiameterM * 100
    115.9 = 115.9

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