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MAE 4316: Propulsion

MAE 4316: Propulsion. An Introduction to Rocket Propulsion Systems. Lesson Topics. Some math Thrust, Impulse, Isp Types of launch vehicle propulsion systems Design considerations Launch Trajectories The Big Picture. Launch Trajectory. Rocket Propulsion. MATH Take notes….

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MAE 4316: Propulsion

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  1. MAE 4316: Propulsion An Introduction to Rocket Propulsion Systems

  2. Lesson Topics • Some math • Thrust, Impulse, Isp • Types of launch vehicle propulsion systems • Design considerations • Launch Trajectories • The Big Picture

  3. Launch Trajectory

  4. Rocket Propulsion • MATH • Take notes…

  5. Liquid Rocket Engines • A liquid rocket engine is a system that uses completely liquid propellants to produce thrust • Advantages • High Isp • Throttle-able • Stop and restart • Reusable • High density Isp (compared to gas storage) • Disadvantages • Low Thrust (compared to solids) • Complex • Cryogenic storage of propellants • Safety

  6. Liquid Rocket Engines • Liquid rocket engines are used for • Launch vehicles • Bipropellant systems • Fuel • Oxidizer • Generates enough thrust • Relatively high storage density • High Isp allows reasonable propellant mass for ΔV required

  7. Liquid Rocket Components

  8. Solid Rocket Motors • A solid rocket motor is a system that uses solid propellants to produce thrust • Advantages • High thrust • Simple • Storability • High density Isp • Disadvantages • Low Isp (compared to liquids) • Complex throttling • Difficult to stop and restart • Safety

  9. Solid Rocket Motors • Solid rocket motors are used for • Launch vehicles • High thrust (high F/W ratio) • High storage density • Ballistic Missiles • Propellant storability • Excellent aging • Quick response • storability • high F/W ratio)

  10. Solid Rocket Motor Components

  11. Hybrid Propulsion Systems • A hybrid propulsion system is one in which one propellant is stored in liquid (or gaseous) state while the other is stored in solid phase. • Solid Propellant / Liquid (or gas) Oxidizer • Most Common • Solid Oxidizer / Liquid Propellant • Less Common

  12. Hybrid Advantages • SAFETY: Literally no possibility of explosion • Controllable • Throttle • Stop / Re-start • Safe exhaust products • Higher Isp than solids • Higher density Isp than liquids • Lower complexity than liquids • Lower inert mass fraction than liquids

  13. Hybrid Disadvantages • More complex than solids • Lower Isp than liquids • Lower density Isp than solids • Lower combustion efficiency than either liquids or solids • O/F variability • Poor propellant utilization • Higher inert mass fraction than solids

  14. Hybrid Schematic

  15. Nuclear Propulsion • Nuclear Thermal Propulsion (NTP) • System that utilizes a nuclear fission reactor • Energy released from controlled fission of material is transferred to a propellant gas • Fission • Absorption of neutrons in a fuel material • Excitation of nucleus causes fuel atoms to split • Two new nulcei on average (Fission Fragments) • High KE from release of nuclear binding energy • Usually radioactive • 1 to 3 free neutrons • Necessary to keep reaction going • Critical if each fission events leads to another • Can be absorbed by reactor material or leak from reactor

  16. Nuclear Propulsion • ADVANTAGES • High Isp (2-10x that of chemical systems) • Low Specific Mass (kg/kW) • High Power Allows High Thrust • High F/W • Use of Any Propellant • Safety • Reduced Radiation for Some Missions

  17. A Nuclear/Chemical Comparison • One gram of U-235 can release enough energy during fission to raise the temperature of 66 million gallons of water from 25oC to 100oC. • By contrast, to accomplish the same sort of feat by burning pure octane, it would require 1.65 million gallons of the fuel

  18. Nuclear Propulsion • DISADVANTAGES: • Political Issues • Social Issues • Low Technology Readiness Level (Maturity) • Radiation issues (Shielding) • High Inert Mass

  19. Nuclear Propulsion Schematic • Propellant Tank: Similar to tanks discussed for liquid propulsion systems. Tank can also be used as a radiation shield. • Turbopump: Provides high pressure propellants to the heat exchange region of the propulsion system. Warm gas from regeneratively cooled nozzle drives the turbines. • Radiation Shield: Protects the payload from radiation from the reactor by absorbing or reflecting neutrons and gamma rays.

  20. Design Considerations • Why does the Space Shuttle look the way it does?

  21. Launch Trajectory

  22. Launch Trajectory

  23. The Big Picture • Ballistic missiles and launch vehicles need large amounts of ΔV • As inefficient as rockets are (low Isp), they are currently the only means by which high velocities (hypersonic) can be easily obtained

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