please set detacher power to 0 before use cause i forgor

This is a simple booster that can be used in custom missiles. It has easily configurable thrust and burn time, and also leaves a smoke trail. The diameter is smaller than that of the stock missiles so you can fit this anywhere.

How does it work?

This uses the same rocket part and detacher setup as my detonator, but the selfDestructTimer attribute here is set to almost infinite. This allows the booster to leave a smoke trail without using missile parts. The engine uses the following input FT expression to allow for custom burn time and power:

clamp((launch * power_kN), 0, power_kN) * clamp01(sign(smooth(-launch, 1/burn_time)))

The fuel supply and air intake are included

How to use

Detach the front fuselage part and save as a subassembly. You will need to declare 3 variables to use this:

power_kN - Booster power in kilonewtons
burn_time  - Burn time in seconds
launch - Launch expression, for example an AG1-8

Here i used 15kN of thrust and a burn time of 5 seconds, close to what you would see on a missile like a late AIM-9 variant. Launch is bound to AG1