1. 1 SOLID PROPELLANT ROCKETS Solid fuel rockets rely on controlled explosion of a mixture of substances Nearly a homogeneous material that is burned Similar to gunpowder ~ (75% potassium nitrate, 10% carbon, and 15% sulfur) Example: STS Solid Rocket Boosters: –Contain ammonium perchlorate as an oxidizer and aluminum as a fuel –Rest of mixture devoted to bonding two reactants –Once a solid rocket is ignited, can not be turned off

2. 2 OVERVIEW: SOLID ROCKET COMPONENTS

3. 3 ADDITIONAL EXAMPLES

4. 4 GRAIN DESIGNS

5. 5 GRAIN CROSS-SECTIONAL GEOMETRIES

6. 6 SOLID PROPELLANT ROCKETS

7. 7 SOLID ROCKETS AND NOZZLE FLOW Special issue with solid propellants that use powdered metals as a fuel additive Adding aluminum to formation of solid propellant increases gas temperature, but incurs performance penalties related to solid particles that are generated –Aluminum burns with oxygen to form Al 2 O 3 particles Particles are initially liquid and solidify during expansion process Also tend to agglomerate to become large particles Large particles do not accelerate as quickly as the gas surrounding them These particles may constitute as much as 10-25% of total mass Need to consider this in nozzle design, which must account for two-phase flow Simplified models exist for analysis of performance: –Results indicate that large particle sizes are a detriment –However, for small particles, there is an optimum amount of Al to add

8. 8 ROCKET FUEL SELECTION GUIDE Desirable Physical Properties –Low freezing point –High specific gravity (dense propellant) –Stability (with time) –Heat transfer properties –Pumping properties (low vapor pressure, low viscosity) –Small variation in physical characteristics with temperature –Ignition, combustion, and flame properties Performance of Propellants Economic Factors Physical Hazards (Explosion, Fire, Spills) Health Hazzards Corrosion