Thank you for actually raising these topics and hopefully getting a discussion going!
For me it didn't really occur to bring it up, probably because I am concerned with engineering safety topics (different but nevertheless) ever day at work as well. The German word is "betriebsblind" - blinded by routine.
Since I am going down the prefilled path I might as well share some of my thoughts:
- don't make yourself what you can buy and you know will work. In my case paintball equipment rated for use with CO2 (similar pressure levels and also liquid/gas). The tanks are tested, the valves have burst disks installed and I clean them thoroughly from any combustibles and replace all sealing with nitrous safe material
- think through proven designs and then copy: again, paintball CO2 stuff, the way the valve is opened and so on. There are a lot of parts you can just buy, inspect, try and then copy or simply use. Other example: ullage, check how much mass of nitrous gas suppliers will put in their bottles and go with that ratio. Usually 0,75kg/l, I aim for a little less and use a scale when filling tanks.
- be afraid, double check everything, wear PSA..
And lots more!
Prefilled motors intrigue me because of the simplicity and repeatability. The GSE you need is smaller and not sitting next to the pad (sun..), no solenoids, no electronics. And you can get the same amount of nitrous every time which takes out one variable and let's you know how efficient your motor is