Prototype #2 has successfully flown. This prototype has boosters that drop off during the boost. Below is a picture of the aft end of prototype #2.
The timer sits in the tube to the left of the MMT. Above this is the pull-pin contacts. The blue piece to the left of the timer tube is the secondary ignitor hook up. At three places around the inside of the body tube are the booster deployers. The top one is holding a booster. The right one is in the hold position without a booster. The left one is in the activated position. The booster attachments are not shown (they were ripped off after this unsuccessful flight. At launch the pull pin actives the timer. The timer then activates the secondary ignitor. This ignitor burns through a loop of stretchable cord (this replaces the thick elastic in this photo). When the cord burns through, the three small elastics open the booster deployers. This allows the boosters to drop free and tumble recover. Simple, huh?