Fore/Top shoulder length on booster?

[JonathanOtt]

How much fore/top shoulder on the booster should extend into the sustainer? Sustainer is a BT50, booster is a BT55 with a 30mm transition.

I know it has to be a 'loose' but not 'sloppy' slip fit, and I'm thinking too much will have too much friction and might not allow separation; too short and it might not stay attached (pre launch).

Thoughts?

 

[waltr]

I've been asking myself that same question for a 2-stage build I'm doing.

Research (reading forums here) indicates about 1 caliber of ISC into sustainer is recommended.

This has worked for me on LPR, BP motors, with gap staging. Should also work on larger rockets.

 

[Banzai88]

I have a MadCow/CW Double Shot kit and a Wildman 2" ShapeShifter jr. 2 stage. Both seem to be set up for 1 caliber of interstage coupler engagement.