Hybrid Modular Booster Concept | Booster | Forum

What is the motivation for having the fuel burn from bottom to top?  I have never seen or read anything about this configuration.  That's not to say it is a bad idea, but it seems (slightly) less simple than the more common configuration, and all our steps away from simplicity should be justified by an expected performance gain or price drop.

With regards to the use of a low melting point metal, I would worry about the pipe melting higher than the current line of combusion, which could irregularities or even interruptions in the oxidiser flow.  If the pipe melted right through we may even see combusion happening along the length of the melted section.

I am a little nervous about endorsing such an odd design without more knowledge of rocketry.

Also, I am not sure that the use of a pipe would allow the effect that makes paraffin fuels so effective, where fast moving oxidiser whips up a fine spray of liquid fuel which burns faster than the solid fuel.  We are not sold on paraffin yet, of course, but I don't think we should commit to a design that rules it out yet either.

I don't mean to be too negative, I am a huge fan of your ongoing SketchUp work, I think it will do a lot to inspire interest in the project, but I don't think we should produce conceptual sketches in this level of detail too far ahead of proper technical planning and actual experience.  Certainly I think it is too soon to be deciding on any kind of scale, like the 1 meter distance from the bottom of the pipe to the bottom of the combustion chamber – we don't really have any idea what sorts of values would be optimal for that yet.

If you do want to produce an internal-view sketch of the modular booster now (and for the record I think it would be a good idea to do so), my advice would be to keep it fairly generic and low detail for now – basically just show an oxidiser tank and a fuel grain connected by some quite generic looking thing so people understand the overall concept.