Non-altimeter based backup recovery system for multiple stage composite motor rockets

This is a system to stop the upper stage of your rocket from coming in balistic if the upper stage does not light. It is very cheap to make, and not too complicated. The only issues are that your rocket has to separate because of the upper stage motor lighting, so you'll have to protect the booster from the flame (I just stuffed wadding in the top of the booster). Also, the booster delay has to be as chosen as if the rocket were one stage (this is so ejection occurs at apogee if the sustainer does not light). This means, however, that you are going to have to make sure that the booster does not hit the ground before the ejection charge goes off if the upper stage does light.

Here's how the system works: There is a backup parachute located in the booster coupler (or anywhere on the booster really, even in a little pod on the outside of the booster if you don't have room inside and it doesn't affect the look of your rocket too badly). The backup parachute is attached to elastic shock cord, with is then attached to any flammable string (I used twine), which is looped through one U-bolt on the sustainer's aft centering ring, goes over the sustainer motor's nozzle, and is tied to another U-bolt on the other side of the centering ring. If the sustainer engine lights, the string will burn, and the booster will be blasted off normally. If the sustainer does not light, the booster will be separated from the sustainer by the booster�s ejection charge. The burn string will remain intact, and the parachute will be pulled from the booster bulkhead.