I'm not sure I understand your question. A skydiver is transitioning (abruptly) from unpowered free-fall into unpowered, albeit greatly slowed, descent. The j

I'm not sure I understand your question. A skydiver is transitioning (abruptly) from unpowered free-fall into unpowered, albeit greatly slowed, descent. The jetpack user is transitioning from powered, controlled horizontal flight (with its characteristic 6 degrees of freedom) into unpowered descent. A back-up chute for the skydiver has essentially, but not quite, the same flight characteristics and initial deployment conditions as a main. Parachutes in a stable flight configuration are incredibly safe and reliable, but it's GETTING that 6-axis dynamic flight-body INTO that stable flight configuration that's the real challenge. It's relatively easy to design a system for even extremely large, static, dead-weights (such as cargo or even battle tanks) to be safely launched, arrested, and landed via parachute. It's an entirely different problem when your safe chute deployment must take into account the wide variance in airspeed, pitch, yaw, altitude, and environmental influences which powered free flight allows. Imagine a worse-case scenario where all power was lost just after a major inadvertent yaw maneuver (it appears to be designed to minimize yawing). That's a sticky-wicket to solve repeatedly and reliably.