solid propellant combustion and its stability
TRANSCRIPT
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Solid Propellant Combustion
and Its Stability
Solid Design Team:
Nick, Scott, Mayra, Afiq, Zach, Derek
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Breaking News: NASA building a restaurant on the
moon
Great food...but no atmosphere
http://www.aerotech-rocketry.com/products.aspx
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Design Process
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● Payload
● Drogue Chute
● Payload/Avionics
● Main Chute
● Motor and Casing
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Quick Recap
Motor and Propellant Selection
Motor Case
Nozzle
Igniter
Aerotech L2200G-P Mojave Green (HTPB/AP/AL)
2024 Aluminum Alloy
Built into Motor
Bridgewire explosive
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● Propellant Combustion
o Burn rate
o Flame Pattern
o Ignition Characteristics
● Propellant Stability
o Acoustic Resonance
o Ignition Wire Configurations
o Combustion Stability
Today’s Overview
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Experimental Observations
● Three dimensional microstructures
● Three dimensional flame structures
● Intermediate products in the liquid and
gaseous phase
● Spatially and temporally variant processes
● Aluminum agglomeration
● Non linear response behavior
● Formation of carbon particles
Physical and Chemical Processes
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Double-Base Flame Pattern
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Composite Flame Pattern
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Bridgewire Igniters
Competition Rules (page 4)
https://www.youtube.com/watch?v=VT6v6UkJE5Q
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Igniters - How They Work
http://www.jacobsrocketry.com/aer/ignition_and_igniters.htm
● 2 Conductor Lead Wire
● Igniter (Bridge) Wire
● Pyrogen
● Launch System with Alligator Clips9
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Ignitability Factors
1. Propellant Formulation
1. Initial Temperature
1. Surrounding Pressure
1. Mode of Heat Transfer
1. Grain Surface Roughness
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Ignitability Factors Cont.
6. Propellant Age
7. Composition & Hot Solid Particle
Content
8. Igniter Propellant
9. Velocity of Hot Igniter Gases
10. Cavity Volume & Configuration
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Ignition Phases
● Phase I: Ignition Time
Lag
● Phase II: Flame-
Spreading Interval
● Phase III: Chamber-
Filling Interval
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Igniter Selection
● Fat Boy Starters○ Manufactured by QuickBurst
○ Used for J-size motors and larger
○ Requires 12 volts
○ Moisture and shock resistant
○ $13.44 for 3 pack
http://www.apogeerockets.com/Rocket_
Motors/Motor_Starters/Fat_Boy_Starter
s
● First Fire Starter○ Manufactured by AeroTech
○ Used for H-size motors and larger
○ Requires 12 volts
○ $12.83 for 3 packhttp://www.apogeerockets.com/Rocket_Motor
s/AeroTech_Accessories/First_Fire_Igniter13
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Launch Controller
● Go Box Launch Controller○ Manufactured by Pratt Hobbies
○ Connected to 12 volt system
■ Car battery
■ 8 pack of AA batteries
■ Jump start battery
○ Will set off all types of igniters
○ $39.99
http://www.apogeerockets.com/Launch_Access
ories/Launch_Controllers/Go_Box_Launch_Co
ntroller
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Combustion Instabilities
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● Vortex shedding
○ Applies to large rockets
● Acoustic/pressure resonance
○ Random
○ Changes with cavity geometry
○ Impossible to characterize analytically
○ Repeatable with identical motors
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Acoustic
● Due to unstable combustion
● Pressure oscillates at least 5%, usually
greater 30%
● heat transfer increase, create
temporary thrust
● Decrease burning duration
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In our case,
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Combustion Stability Assessment
● Accepted combustion stability rating
procedure does not exist
● Most common: T-burnero Process
o Results
o Limited method
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Addressing Combustion Instability
● Changing grain geometry
o Shifts frequencies away from
undesirable values
● Changing propellant
composition
o Adding aluminum, changing the
binder
● Adding mechanical device
o Reduces unsteady gas motion
o Changes natural frequency of
cavities
o Cons: extra inert mass,
additional problems with heat
transfer or erosion 21
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How does it apply to our design?
● Chosen motor: Aerotech L2200G-P Mojave
Green
● Aerotech does not provide combustion stability
information
● Possible to test the stability ourselves
● Addition of mechanical device 22
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Summary
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● Flame pattern predetermined for our design
● Fat boy or First Flame Igniter with Go Box
Launcher
● The combustion stability of propellant will be
observed during testing of the full scale motor.
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Next Steps
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● Work on solid motor design review
● Finalize purchase orders
● Continue RockSim designs and simulations
● Begin electrical and recovery considerations
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Questions?
THANK YOU!