Black Shire

In all three configurations both motors are ignited at the same time (like a cluster). A hold back system is required. The E7-RCT orbiter motor burns slightly longer than the E15-4 booster motor. That makes it a 1 1/2 parallel stage rocket. Separation occurs when the rear ejection parachute deploys from the booster stage. The orbiter motor remains with the orbiter.

The two motors used have different impulses and average thrusts. As a consequence, they have different offsets from the vertical C.G. and also different thrust line angles. Getting that part right is a real B... err, challenge.

Regards,

DJ Miller