How fast should a rocket descend on a parachute?
For model rockets, the ideal descent rate is between 3-6 m/s (10-20 ft/s). This provides safe recovery while preventing damage to the rocket or surroundings. See also our find Quarter Mile ET with Quarter Mile Time Calculator.
What is the drag coefficient (Cd) for different parachute shapes?
Flat circular parachutes have Cd ≈ 1.3-1.5, hexagonal (parasheet) Cd ≈ 1.2-1.4, hemispherical Cd ≈ 1.2-1.3, and conical parachutes Cd ≈ 0.7-0.9. The calculator automatically applies appropriate coefficients.
Should I include a spill hole in my parachute?
A spill hole of 10-20% of the parachute diameter improves stability and reduces oscillation during descent. It slightly increases descent rate but provides more controlled landing.
How does altitude affect parachute performance?
Higher altitudes have lower air density, requiring larger parachutes for the same descent rate. At 3000m altitude, air density is about 0.9 kg/m³ compared to 1.225 kg/m³ at sea level.
What is reference area in parachute calculations?
Reference area is the projected area of the parachute perpendicular to the direction of descent. It's used in drag calculations and differs from the actual fabric area of the parachute.
Can I use this calculator for different rocket sizes?
Yes, this calculator works for any model rocket weight from small rockets (10g) to large high-power rockets (5kg). Adjust the recovery mass to include the parachute and recovery system weight. You might also find our Estimated 1/4 Mile Time — Eighth Mile to Quarter Mile Converter useful.