Ignition System – Fail Often and Fail Early

July 27, 2017

by bluShift Aerospace

Ignition System – Fail Often and Fail Early

The last several weeks have been largely consumed with pressure testing of the oxidizer system. This week we started work on assembling the circuitry and piping for the ignition system. We’re using a version ignition system that we had developed and tested previously in 2015, but with a different oxidizer.

Incremental Failure Fun

As we go through the assembly process we are testing each element, to make sure it functions as expected – as opposed to slapping everything together and “see how it goes”. We have learned the hard way that if you don’t test your assembly and test a system in its components we wind up with a multitude of bugs to solve.

Not only is it difficult to identify all the right sources of the problems in this situation, you’re kicking yourself for not addressing the issues early on – saving yourself time in the end. Put in better terms we must “fail often and fail early”.

Rockets Can Get a Case of Engine Knocking Too

Our key goals for this system are threefold. One to obviously ignite our bio-derived fuel. Two, to do so consistently and easily. And three, to avoid “hard starts”.  The last two may be the most challenging based upon past test experiences.

In a hard start the engine ignites more energetically than expected, raising combustion chamber pressures potentially well beyond their expected normal operating point. As a result, we would potentially see damage to our injection and ignition bulkhead, as well as our nozzle – all of which we have invested so much time in manufacturing.  We really want to get it right.

First we’ll testing the ignition system with essentially no combustion chamber. Then add a “dry” combustion chamber (no fuel), followed by  testing with fuel but no nozzle. And then lastly with the nozzle attached.

Here’s to failing soon and creating solutions just as quickly.

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