Originally Posted by
walbut
DV
In the case of a zero zero ejection, while the seat is moving upwards under the force from the rocket motor, the drogue gun fires and when the drogue chute deploys it rotates the seat around so that the crewman is moving upwards, feet first. When the scissor shackle releases from the seat and the main chute deploys, the occupant and seat are still moving upwards. In this case it is effectively the inertia or kinetic energy of the seat moving upwards that provides the energy to inflate the chute, which is partially if not fully inflated when the occupant reaches his/her apogee at around 200 -300 ft depending on weight.
Walbut
I can confirm this from experience. The most surreal part of my Martin-Baker ride (0 ft / about 65 kts) was looking up (in my frame of reference) to watch RAF Valley receding rapidly in the overhead, then looking down to see my boots pointing at the sky.