At EADS Launch Vehicles, Toulouse, France (www.lanceurs.aeromatra.com), engineers have refined the separation process and optimized the amount of pyrotechnics used. An electric signal ignites the entire length of a metal-encased explosive running the circumference of the rocket. A back plate focuses the resulting blast outward, where the force is just enough to break the connecting plate along a precisely scored line. The blast does not shatter the metal plate into thousands of small pieces that could interfere with the upper stage. The lower stage falls away, leaving the second and upper stages undamaged.
Explosives help jettison rocket's lower stages.
Explosives have long been used to help multistage rockets quickly and cleanly shed their lower, depleted stages.