Optimizing the Structural and Deflagration Properties of Aluminum-Rich Paraffin-Based Hybrid Rocket Motors

Abstract

Hybrid rocket motors offer an alternative to conventional solid motors and liquid engines. One of the most severe limiting factors of hybrid rocketry is the low regression rate as the fuel does not burn nearly as quickly as in a solid rocket. However, the discovery of liquefying fuels such as paraffin has greatly improved the regression rate of hybrid rocket fuels. Such fuels operate by liquefying to a greater extent than conventional fuels, whereby the low viscosity allows droplets of the fuel to become entrained in the oxidizer flow which increases the speed of the combustion process. Paraffin has a low compression strength and fractures easily. Recent studies show that the incorporation of polyethylene and aluminum powder can maintain and even increase the high regression rate of paraffin rocket motors, and increase the structural strength to allow these motors to survive the flight loads they experience during launch. This project seeks to further advance the benefits of the addition of aluminum powder as previous research suggests that the addition of aluminum powder at a concentration greater than 25 by mass could greatly increase the regression rate. As the concentration of aluminum powder increases more energy is released from the combustion of the fuel which increases the temperature of the combustion resulting in a faster regression rate, but the fuel also becomes more viscous which prevents the entrainment of fuel droplets which serves to limit the regression rate. Due to the COVID-19 pandemic, test fires were unable to be completed to measure the regression rate of the fuel samples with a higher concentration of aluminum powder. However, data from compressive yield testing of each of the fuels suggests that the optimal fuel composition contains 35 aluminum powder by mass.

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Document Details

Document Type
Technical Report
Publication Date
Jul 06, 2020
Accession Number
AD1136701

Entities

People

  • Kaden C. Dohm

Organizations

  • United States Naval Academy

Tags

Communities of Interest

  • Weapons Technologies

DTIC Thesaurus Topics

  • Additives (Chemicals)
  • Aeronautics
  • Alkanes
  • Aluminum
  • Astronautics
  • Burning Rate
  • Combustion
  • Combustion Chambers
  • Composite Materials
  • Electron Microscopes
  • Failure Mode And Effect Analysis
  • Fuels
  • Heat Capacity
  • Heat Energy
  • Hybrid Rocket Engines
  • Hydroxyl Terminated Polybutadiene
  • Instructors
  • Materials
  • Materials Laboratories
  • Materials Testing
  • Mechanical Properties
  • Rocket Engines
  • Rocket Fuels
  • Rocket Propulsion
  • Rockets
  • Scanning Electron Microscopes
  • Specific Heat
  • United States
  • United States Naval Academy
  • Yield Strength

Readers

  • Mathematics or Statistics
  • Rocket Propulsion.