Boris, the flight of the Soyuz was beautiful, but I never did get to look at it up close on the field. Nice! I didn't realize it was an outboard BP cluster with an APCP core motor. I'd love to talk to you at a launch some time about clustering (especially APCP motors, or a combo of BP and APCP - sounds tricky). I've only clustered up to 4 BP motors at a time, but I like it.
Thanks.
The Soyuz is one of my favorite rockets.
Between building it initially and rebuilding it after the first flight, I put somewhere around 200 hours into it.
Unless a rocket will take me into space, I don't think I will spend that much time on a project again.
The key to successfully clustering hobby rockets is to make every step from the press of the launch button to motors thrusting hard happen as quickly and reliably as possible:
1) Lots of electrical power - high current cluster box with LiPo battery and automotive relays - mine can deliver 100A+ at 12v+ to the igniters. This set up has fired up to 30 motors repeatedly.
A typical club relay will usually do well with 4 motors and may handle 8.
With any cluster, always make sure there is a relay and power source at the pad. Long runs of lamp cord between the power source and the igniters must be avoided due to severe voltage line loss.
2) Reliable igniters with long leads and No clip whips - Rocketflite CF wires and pyrogen kits are what I use for almost all clusters
3) Only use motors that will come up to pressure very quickly - preferably under 0.3 seconds - all BP motors and most CTI motors will do this. Can use other motors if careful steps are taken to assure quick firing.
If these conditions are met then BP and AP motors can be mixed at will.
Please see website in my signature for more details.
I also prefer to have redundancy for recovery deployments for HP projects.
The Soyuz flies with motor deployment backup to the primary altimeter deployment.