Originally Posted by
walbut
DV
The 500 foot minimum operation altitude must have associated with it a horizontal and vertical speed. Perhaps the 500 ft is based on zero speed in both directions, in which case it is the acceleration of the man and seat downwards under gravity that generates the energy required to inflate the parachute.
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.
I cant remember all the timing details. However if you want more information, there is an excellent little book called Engineering for Life by John Jewell that I acquired many years ago courtesy of Martin Baker and I 'borrowed' one of our office copies just before I retired. It might have been updated since ours was published in 1979.
Walbut
Indeed. (See my earlier) comprehensive QTPs for both equipment and installations will have been done.