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Hi Nick,

Great to have you aboard!  It sounds like you are an incredibly handy person for us to have around.

Here's a quick run down on some organisational things you should probably to know to help you get involved quickly and helpfully: basically, we recently decided that the way we had been running our projects so far – basically making technical decisions in an informal way on forums/IRC/etc. based on some limited reading and gut instinct-  was not feasible in the long term.  So we have been working on our Engineering Process in the hopes of coming up with a lightweight system for making decisions in a way that is well documented and well researched.  At the core of this process with regards to making technical decisions (like choosing fuels and oxidisers for rockets!) is the Design Task Tree concept, which you can read about at the Engineering Process Wiki page.

Now, the Design Task Tree for OHKLA has already been sketched out a bit, particular with regards to the hybrid rocket design.  You can see a page so far for propellant choice and one for grain geometry.  Neither page is complete, and both were written by me – someone who is absolutely not an expert and has basically just done a lot of reading, from the web and from text books.  If you could look over those pages and (i) correct any mistakes I may have made and (ii) expand them in any way you think useful, it would be a tremendous help.  There is a page for the ignition system, too, but it's blank right now because I don't know much about this area.  If you wanted to start filling it out, following the general template that's already there (and looking at other pages for guidance), that would be a huge help!

The general idea is that once pages like those are complete, i.e. we have listed all reasonable potential choices of solution to a problem and have the numbers, pros and cons clearly displayed, we make a choice on that particular decision by voting.  We have someone on our team who is hopefully going to start work soon on a web app to allow this voting to take place, but for now it is not there.  There's plenty of work to be done gathering the data to inform our decisions, though!

For what it's worth, at this stage, with what knowledge I have, I am planning to vote (when the time comes) for a paraffin/N2O rocket with a single circular combustion port geometry.  The motivations for this are primarily based around simplicity.  N2O is self-pressurising (removing the need for a pressurant tank and value) and non-cryogenic (removing the risk of valves freezing shut/open, which I have read was a big problem with some of AMROC's LOX hybrids), and paraffin's high regression rate (due to liquid boundary layer combustion) should let us get adequate thrust with the circular port geometry, which is, obviously, the simplest geometry there is.  If you have any thoughts on this, I would love to hear them.

Once again, great to have you aboard, hope you have fun helping out!

Just another quick idea: we are now starting to work on what we are tentatively calling "technical reports".  There is one tech report underway so far, on atmospheric entry.  If you wanted to write a tech report on hybrid rockets, or some particular aspect of them you know a lot about, that would be another excellent way that you could help – it would let the rest of us get more up to speed on the topic so we can get more quality work done.