page_title: Hybrid-propellant rocket
section_title: Additive manufacturing
hierarchical_section_title: Hybrid-propellant rocket / Fuel / Grain manufacturing methods / Additive manufacturing
caption_attribution_description: English: This is a 3D-printed fuel grain used in development testing at Purdue University for a hybrid rocket motor that would fit inside of a suitcase. The suitcase would be a portable education demonstrator, used for demonstrating rocket combustion. The motor used nitrous oxide as the oxidizer and pyrodex pellets for the igniter. The fuel grain pictured here also functions as the combustion chamber. Typical rocket motors (not used for demonstrations) have a case around the fuel grain in order to contain the pressure from the combustion events, however in this case, the fuel grain acts as the pressure vessel. The combustion events can be seen throughout the entire motor, including the nozzle.
context_page_description: A hybrid-propellant rocket is a rocket with a rocket motor that uses rocket propellants in two different phases: one solid and the other either gas or liquid. The hybrid rocket concept can be traced back to at least the 1930s.
  Hybrid rockets avoid some of the disadvantages of solid rockets like the dangers of propellant handling, while also avoiding some disadvantages of liquid rockets like their mechanical complexity. Because it is difficult for the fuel and oxidizer to be mixed intimately, hybrid rockets tend to fail more benignly than liquids or solids. Like liquid rocket engines, hybrid rocket motors can be shut down easily and the thrust is throttleable. The theoretical specific impulse performance of hybrids is generally higher than solid motors and lower than liquid engines. as high as 400s has been measured in a hybrid rocket using metalized fuels. Hybrid systems are more complex than solid ones, but they avoid significant hazards of manufacturing, shipping and handling solid rocket motors by storing the oxidizer and the fuel separately.
context_section_description: Additive manufacturing is currently being used to create grain structures that were otherwise not possible to manufacture. Helical ports have been shown to increase fuel regression rates while also increasing volumetric efficiency. An example of material used for a hybrid rocket fuel is acrylonitrile butadiene styrene (ABS). The printed material is also typically enhanced with additives to improve rocket performance. Recent work at the University of Tennessee Knoxville has shown that, due to the increased surface area, the use of powdered fuels (i.e. graphite, coal, aluminum) encased in a 3D printed, ABS matrix can significantly increase the fuel burn rate and thrust level as compared to traditional polymer grains.
caption: A transparent portable education demonstrator 3D-printed hybrid rocket fuel grain with dual helical fuel ports, a post combustion chamber, and a de Laval nozzle, shown prior to hot fire test.
exif: {"Image ImageDescription": "SONY DSC", "Image Make": "SONY", "Image Model": "DSLR-A200", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "GIMP 2.6.11", "Image DateTime": "2016:12:26 21:29:30", "Image ExifOffset": "208", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "922", "Thumbnail JPEGInterchangeFormatLength": "3757", "EXIF ExposureTime": "1/80", "EXIF FNumber": "63/10", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "100", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2014:04:28 17:44:05", "EXIF DateTimeDigitized": "2014:04:28 17:44:05", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "8", "EXIF ShutterSpeedValue": "790241/125000", "EXIF ApertureValue": "331919/62500", "EXIF BrightnessValue": "27/4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "497/100", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "50", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3712", "EXIF ExifImageLength": "2486", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "798", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF FocalLengthIn35mmFilm": "75", "EXIF SceneCaptureType": "Standard", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal"}