What combination of parachute ejection timing is most likely to cause zipper damage in a rocket?

What combination of parachute ejection timing is most likely to cause zipper damage in a rocket?

• A. Parachute ejection occurred too soon after motor burnout
• B. Parachute ejection occurred too late after apogee
• C. Parachute ejection occurred at apogee on a vertical flight
• D. Both "A" and "B"

Answer: (D)

Zipper damage happens when the parachute deploys under high airloads that pull hard on the body tube seam. The safest time to eject is near apogee when the rocket’s velocity is very low, so the parachute can inflate with minimal dynamic pressure. If parachute ejection occurs too soon after motor burnout, the rocket is still moving fast and facing significant aerodynamic drag, which creates a strong force on the airframe at deployment and can tear the seam. If ejection happens too late after apogee, you’re still descending with substantial velocity, so the parachute must suddenly fight that motion again, producing heavy loads on the body tube and risking zipper damage. Therefore, both premature ejection after burnout and delayed ejection after apogee raise the risk, making those timing mistakes the most likely to cause zipper damage. Deploying at apogee on a vertical flight minimizes these loads and is the safer approach.

Zipper damage happens when the parachute deploys under high airloads that pull hard on the body tube seam. The safest time to eject is near apogee when the rocket’s velocity is very low, so the parachute can inflate with minimal dynamic pressure.

If parachute ejection occurs too soon after motor burnout, the rocket is still moving fast and facing significant aerodynamic drag, which creates a strong force on the airframe at deployment and can tear the seam. If ejection happens too late after apogee, you’re still descending with substantial velocity, so the parachute must suddenly fight that motion again, producing heavy loads on the body tube and risking zipper damage. Therefore, both premature ejection after burnout and delayed ejection after apogee raise the risk, making those timing mistakes the most likely to cause zipper damage. Deploying at apogee on a vertical flight minimizes these loads and is the safer approach.