In various research projects for combustion and mixing clear windows are often used, usually in conjunction with some sort of schlieren or Raman spectroscopy set up. Below is a link to a quick summery paper on one of the projects less than a decade ago. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050169188.pdf Lloyd On Fri, Sep 19, 2014 at 1:19 PM, Lars Osborne <lars.osborne@xxxxxxxxx> wrote: > High speed video of a clear rocket engine made by rocketdyne in the 60's. > > http://youtu.be/QBV0DED7RYA?t=6m4s > > Has anyone made a clear liquid engine since? > > Thanks, > Lars Osborne