Final supersonic flight of our all-carbon-fiber Mongoose 98 at BALLS 25. Video: https://youtu.be/wiX3_UGTf7c
She flew well after a rebuild from her last flight, a supersonic shred (aka a Rapid Unscheduled Disassembly). The green propellant glows with the purity of a laser. I was curious about propellant chemistry when I first saw it, and wrote for ScienceBlogs: Metal ions combine with electrons in the flame, and the metal atoms are raised to excited states because of the high flame temperature. Upon returning to the ground state, they give off light (from their line spectrum) characteristic of that metal. The ions come from metal chlorides: Barium Chloride (BaCl) for green, Copper Chloride (CuCl) for blue, or Strontium Chloride (SrCl) for red. These metal chlorides generally do not exist at room temperature or are too reactive to add as an additive, so precursors are mixed in, and they react during the burn to create the desired molecules. The Chlorine comes from the Ammonium Perchlorate oxidizer for free, and one need only add metal salts such as nitrates or carbonates to provide the metal (unfortunately, they are hygroscopic and have less energy content than the APCP oxidizer, so as with most additives, they tend to be more show and less go). So, for example, Barium Nitrate is the additive that forms BaCl during the burn to emit a laser-like green in the flame. From http://scienceblogs.com/photosynthesis/2009/05/22/rocket-propellant-types/
Leave a Reply