Interstage length

Titan
Always minimize interstage length for two reasons:
1. minimize weight
2. longer interstage length decreases vehicle integrity - increases chance of buckling.

Vertical stacking - don't want too long - too unstable
standing waves - loads to accomodate more loads:
1. more weight
2. thicker walls on interstage

Interstage length is minimum to accomodate RL-10.

Retractible extension to nozzle - radiation cooled - red when firing.