> Since I'm not a rocket scientist...what makes that amazing exhaust? "Mach diamonds" result when the exit pressure of the exhaust is not matched to the ambient pressure. The nice purple colour is presumably a feature of the methane fuel - they are quite likely burning fuel rich at this state of testing as this usually keeps temperatures down. Russell -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist