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Title: Propellant Fundamentals

Propellant Fundamentals
  • Dr. Carol Campbell
  • Senior Scientist, Team Leader
  • ATK Launch Systems
  • Email

Biographical Information
  • Education
  • B.S. Chemistry, Northern Arizona University
  • Ph.D. Inorganic Chemistry, Utah State University
  • Work Experience
  • ATK 18 years including 13 years in RD and 5
    years in program management
  • Talley Industries of Arizona 2 years in RD
  • Significant Achievements
  • Principle Investigator for ONR aluminized
    plateau-burning propellants with both HTPB and
    energetic binder systems, Navy DTO high-energy
    Class 1.1 propellants, IHPRPT Phase II
    propellants optimization and scaleup, Lockheed
    low cost third stage propellant, AF PAP hazards
    characterization program and numerous RD
  • Program manager for Navy decoy flare program,
    Navy reactive materials programs, nominated to
    2003 Technology Hall of Fame as part of team for
    development of Thiokol demining flare
  • Seven patents and over 20 technical publications
  • How You Became Interested in Solids
  • Closet pyromaniac

  • Objectives
  • Provide an introduction to solid propellant
    formulation concepts
  • Scope
  • Propellants selection factors
  • Propellant ingredients
  • Propellant characterization

Propellant Fundamentals Outline
  • Solid rocket motor overview
  • Determination of propellant requirements
  • Fundamentals
  • Isp, density
  • Ballistics, mechanicals
  • Formulation fundamentals
  • Ingredients
  • Tailoring formulations
  • Propellant characterization
  • Ballistic and combustion properties
  • Mechanical properties
  • Bondline properties
  • Performance evaluation
  • Delivered vs predicted data for motors
  • Hazards determination
  • Fundamental safety properties
  • Shock sensitivity
  • Classification by DoT/DoD
  • Insensitive Munition requirements

Solid Rocket Motor Overview
Solid Propellant Rocket Motors
Peacekeeper Stage I
Solid rocket motors come in all shapes and sizes
depending upon their intended use. Most are
cylindrical in shape with a length- to-diameter
ratio (L/D) ranging from 21 to 121. Special
motors may be spherical or nearly spherical in
Solid Motor Applications
Space Shuttle
Minuteman III
Trident II (D5)
Castor 120
Hydra 70
Solid Rocket Motor Components
  • Major components
  • Case
  • Pressure vessel (500-4000 psi)
  • Propellant
  • Energy provider
  • Nozzle
  • Energy converter
  • Control Systems
  • Thrust vector control
  • Attitude control is generally a separate system

Solid Rocket Components
How Thrust Is Created
  • Propellant burning in chamber raises chamber
  • Pressure difference causes gases to accelerate
    from chamber and through nozzle at high speed

Solid Rocket Propellant Grains
  • Why the funny shaped holes in the middle of a
    solid propellant grain?

Thrust is controlled by mass flow. Mass flow in
a solid rocket motor is controlled by the exposed
burning surface. The exposed burning surface is
controlled by the internal configuration of the
hole in the propellant grain, which is created
by a mandrel (core)
Throttling by design
Propellant RequirementsFundamentalsIsp,
DensityBallistic and Mechanical Properties
What Makes a Rocket Operate?
  • Four things to know
  • Newtons first law
  • Newtons second law
  • Newtons third law
  • Boyles Law

Newtons Laws
  • A body in motion will travel in a straight line
    unless acted upon by an external force
  • The acceleration of the body will be proportional
    to the net external force
  • a F/m
  • For every action there is an equal and opposite

Newtons First Law
  • In the absence of contrary forces, the speed and
    direction of an objects movement will remain
    constant (inertia)
  • A rockets thrust must be great enough to lift
    its total mass from the launch site or it will
    not fly
  • Gravity and air resistance (drag) must be taken
    into account in determining both the required
    thrust and computing its trajectory tothe
    ultimate target

Newtons Second Law
  • Acceleration is the ratio of the applied force to
    the inertial (rest) mass of the object (F ma)
  • The greater the amount of thrust developed
    relative to the mass of the total vehicle, the
    faster the rocket will move through the air
  • If enough thrust is developed, the speed can be
    built up until the vehicle can escape the pull of
    earths gravity and move into outer space (about
    7 miles per second)

Newtons Third Law
  • For every force exerted by one mass on another,
    there is an equal and opposite reaction exerted
    by the second mass on the first
  • Expulsion of combustion products (gases) through
    the nozzle produces a reactive force on the
    rocket in the opposite direction which causes it
    to be propelled

Mass Flow
Boyles Law
  • Reducing the volume of a container within which a
    gas is held causes its pressure to increase in
    direct proportion
  • P1V1P2V2
  • As the temperature is raised on a fixed mass and
    volume of gas the pressure increases
  • PV nRT (Ideal Gas Law)
  • Propellant combustion increases n and T

Starting Pressure and Volume
Final PressureHigher Final Volume Lower
Robert Boyle
Basic Principles of Solid Rockets
  • Case
  • Pressure Vessel
  • Thrust Vector Control
  • Guidance

Flow of Exhaust Gas
High Pressure
Low Pressure
  • Nozzle
  • Gas Expansion
  • Igniter
  • Ignition
  • Grain
  • Thrust
  • Mass Flow
  • Sustained Pressure
  • Throat
  • Pressure Control

Idealized Thrust Equation
Pa - ambient pressure
At - throat area
Pe - exit pressure
Ae - nozzle exit area
Momentum change
Pressure thrust
Optimum nozzle expansion ratio (? Ae/At) when
Pe Pa
Specific Impulse What and Why
  • Impulse (I) is thrust x time
  • Longer duration thrust increases rocket speed,
  • Carrying more propellant weight limits the gain
  • Specific Impulse (Isp) is Impulse produced per
    weight of propellant burned
  • Isp F/m F?t / ?m
  • Higher Isp uses less propellant to create
    impulse, so a smaller, lighter missile
    accelerates faster, and
  • Faster acceleration creates more speed
  • Solids 240-255 sea level, 290-305 vac
  • Liquids 280-400 sea level, 310-450 vac
  • Doubling missile speed quadruples its range

Also ?V Ve In Ve
Isp X g
Thrust Increases with Altitude
  • As the missile ascends, the ambient pressure
    decreases so the pressure thrust contribution
  • This effect is important in nozzle design

Density Impulse
  • An indicator of package size
  • Dense propellants pack a lot of propellant into a
    smaller airframe
  • Density impulse
  • Specific impulse multiplied by propellant bulk

Density impulse ? Isp (N-sec/m3 or lbf-sec/in.3)
How Do We Calculate Isp and Density?
Equivalent Formula AL 0.59300 C
1.08745 O 2.37779 H 4.03415 CL
0.57954 N 0.59085 FE 0.00013
React. mix. dens 1.72260 g/cc 0.062233
lbm/in3 O to F weight ratio 0.0000
Equivalence Ratio 1.9040 OCAL ratio
1.2028 Output from RKT run Pressure
1000.0 psi Flame Temp 3243.9 K Molecular
wt 26.605 Specific Heat ratio 1.15936
Enthalpy -440.83 cal/g Mass Gas Fraction
0.7114 Moles(gas)/100g(Gen.) 3.759 Beta
(carbon oxidation) 0.0734 Cstar 5172.0
ft/sec Exit Parameters Pressure
14.70 psi Temperature 1900.20 K
Area Ratio 9.799 Vacuum Impulse
285.11 lbf-s/lbm Spec Imp. (ISP) 261.96
lbf-s/lbm Output from TP run Enthalpy
-2505.73 cal/g (at 298.1 K) Heat of
Combustion 2064.90 cal/g ( 3716.82
btu/lbm )
  • Most common tool is the NASA-Lewis thermochemical
  • Input molecular formula, heat of formation,
    density for each ingredient in ingredient
  • Input propellant ingredients, weight percent, and
    operating conditions
  • Pressure, expansion ratio
  • Code has library of chemical reactions and
    associated constants
  • Provides output including exhaust species and
    those shown here

Range Depends Mostly on Burnout Velocity2(?V)2
For a Flat Earth case (Range ltlt Rearth)
For Vo 0, tb 0, and no drag
? 45 deg yields maximum range
Vo initial velocity and tb rocket burning
There Are Multiple Ways to Drop UsedPropulsion
Hardware Mass
High-Velocity Vehicles Use Series Staging
  • Staging allows large (?V/Isp) for
  • Long range
  • Low Isp technology use
  • Payload fraction is product of successive
    burning-payload fractions
  • Cost and complexity increase
  • Multiple stages to develop and build
  • Interstage systems required (structures and

Where Do Ballistic and Mechanical Properties Fit?
  • Ballistic properties (burn rate and dependence of
    the burn rate on pressure and temperature) affect
  • The grain design must produce correct thrust
    profile (mass flow rate) over operating pressures
  • Cases (pressure vessels) are designed with
    factors of safety to account for variability
  • Mechanical properties (strength and stretchiness)
    required are affected by grain design
  • Motor diameter, bore diameter, grain features,
    stress relief flaps
  • Operating pressure and temperature range
  • Transportation and assembly loads
  • How well the propellant sticks to the
  • Interdependence for optimum performance

Requirements Summary
Low molecular weight exhaust High combustion
temperature High Pc/Pe High mass
ratio Components High bulk density
For lightest weight system, engineers seek high
High ? Lightweight materials Low factors of
safety Highly stressed Highly integrated
For smallest volume system, engineers seek high
density lsp
Formulation FundamentalsIngredientsTailoring
Solid Rocket Propellants
  • What is a solid rocket propellant?
  • Propellants are energetic compositions designed
    to burn in a controlled manner to generate gas
    or propulsive force
  • Propellant is a hard, rubbery mass (think pencil
    eraser!) containing fuel, oxidizer, and other
    minor additives necessary to control the
    propellants ballistic and physical properties
  • The fuel, oxidizer, and additives are generally
    solid materials held together by the binder, an
    elastomeric or thermoplastic material

Propellants do not require air or other external
sources of oxidizer to combust Propellants are
capable of violent deflagration or detonation
under certain conditions
Ignition Source
The Combustion Triangle
Types of Solid Propellants
  • Black powder (13th century)
  • Homogeneous propellants
  • Single-base, nitrocellulose, smokeless powder
    (19th century)
  • Double-base, nitrocellulose/nitroglycerin
  • Extruded or cast (solvent or solventless
  • Composite modified (energetic solids added to
  • e.g., potassium perchlorate
  • Triple-base, NC/NG/nitroguanidine
  • Elastomer-modified (EMCDB) or cross-linked
    double-base (XLDB)
  • Curable prepolymer added to enhance one or more
  • Homogeneous propellants are often minimum-smoke
  • Composite propellants
  • Heterogeneous propellant consisting of a
    continuous polymeric binder phase filled with a
    homogeneous dispersion of solid particles
  • Two major binder system classes high molecular
    weight and low molecular weight curable

Application Will Determine Ingredients
  • Plume signature
  • Minimum smoke (no metal fuel, no HCL, limited
  • Reduced smoke (no metal fuel or limited metal
    fuel, HCL)
  • Smokey (metallized, HCL)
  • Radar attenuation, IR
  • Other exhaust product characteristics
  • Temperature
  • Oxidation index
  • Erosiveness
  • Corrosiveness
  • Toxicity
  • Contamination effects

Propellant Class By Signature
Classes of Solid Propellant (Signature)
  • Metalized ( Isp 262-272 lbf-sec/lbm)
  • Class 1.3 or Class 1.1 (detonable)
  • Class 1.3 Inert binder, AP, Al
  • Class 1.1 Inert binder, energetic plasticizer,
    AP, Al
  • Strategic/Space booster applications
  • Highest performance
  • Reduced-Smoke (Isp 246-252 sec)
  • Minimal particulates (no Al)
  • Typically AP oxidizer
  • Minimum-Smoke (Isp 220-248 sec)
  • No AP or Al, minimal particulates
  • Nitrate esters, nitramines usually Class 1.1

Smoky Propellants
Minimum and Reduced-Smoke Propellants
Composite PropellantsCross-Linkable Prepolymers
  • Polysulfide
  • Polybutadiene-based
  • Polybutadiene acrylonitrile (PBAN),
    carboxyl-terminated polybutadiene (CTPB),
    hydroxyl-terminated polybutadiene (HTPB)
  • Polyether (hydroxyl-terminated), a.k.a. HTPE
  • Polyethylene glycol (PEG), HO-CH2CH2Ox-OH
  • Polyester and polyether-polyester copolymers
  • Energetic prepolymers

Most prepolymers have dual use
In curable composite propellants, the prepolymer
molecules are cross-linked via the formation of
covalent chemical bonds
Example Cure ReactionHTPB and IPDI
Hydroxyl (-OH) groups on HTPB prepolymer react
with isocyanate (-NCO) groups on IPDI to form
urethane linkages, providing chain extension.
Cross-linking is provided via side-chain OH
groups on the HTPB (not shown)
Composite PropellantsEnergetic Prepolymers
  • Polymer contains energetic functional groups
  • Nitro (-NO2) , nitrato (-ONO2) , azido (-N3) ,
    nitramino (-NNO2), difluoroamino (-NF2)
  • Energetic prepolymers are normally
  • Polyglycidyl nitrate (PGN or polyGlyn)
  • Glycidyl azide polymer (GAP)
  • Polyoxetanes
  • Azidomethylmethyloxetane (AMMO)
  • Bis(azidomethyl)oxetane (BAMO)
  • Nitratomethylmethyloxetane (NMMO)

Composite PropellantsBinder System Ingredients
  • Prepolymer (see prior charts)
  • Curative
  • Provides chain extension and/or cross-linking of
  • Di-, tri- or polyfunctional epoxide or isocyanate
  • ERL-0510 (epoxide), MAPO (aziridine)
  • IPDI, DDI, HDI, MDI, TDI (difunctional NCO)
  • N-100, N3300, PAPI, Solithane 113 (NCOgt3)
  • Cure catalyst
  • Increases the rate of curing or lowers cure
  • TPB, FeAA, Cr-octoate, Fe-octoate, TPTC, DBTDL
  • Cure catalyst activator (e.g., maleic anhydride
    or DNSA for TPB)
  • Cure catalyst retarder (e.g., MgO for TPB, HAA
    for FeAA)
  • Cross-linking agent (polyfunctional molecule or
  • Trimethyolpropane, TP4040 (hydroxyl

Composite PropellantsBinder Ingredients
  • Bonding agent
  • Promotes adhesion between binder and solid
  • Generally required with HTPB propellants
  • HX-752, Tepanol
  • Plasticizer
  • Increase propellant strain, sometimes used as a
    processing aid
  • Inert plasticizers DOA, DOS, DOP, IDP
  • Energetic plasticizers also used to tailor
    energy/hazard sensitivity
  • Stabilizers
  • Antioxidants, thermal stabilizers, free radical
    scavengers, metal sequestering agents, other
  • Processing aids
  • Cure retarder (e.g., pyrocatechol), isocyanate
  • ODI, lecithin, moisture (with extreme care),
    silicone oil

Composite PropellantEnergetic Solid Ingredients
  • Oxidizer
  • Ammonium perchlorate, NH4ClO4 (AP)
  • Ammonium nitrate, NH4NO3 (AN)
  • NaNO3, KNO3, KClO4, LiClO4
  • Ammonium dinitramide, NH4NNO22 (ADN)
  • Hydroxylammonium perchlorate, NH3OHClO4 (HAP)
  • NH2NH3CNO23 (HNF), NO2ClO4 (NP)
  • Nitramines
  • RDX, HMX, and CL-20
  • RDX/HMX are monopropellants
  • CL-20 is a net oxidizer

Composite PropellantMetallic Fuels
  • Metals
  • Aluminum (Al), Magnesium (Mg), Al alloys (Al/Li,
    Al/B, Al/Mg)
  • Boron (B), Beryllium (Be)
  • Metal hydrides
  • ?-alane (AlH3), BeH2, boron hydrides, carboranes
  • High density fuels/metal oxides
  • Zirconium, Hafnium, Tungsten
  • Bismuth oxide (Bi2O3)
  • not a fuel

Composite PropellantBallistic Additives and
  • AP particle size, Al (metal fuel) particle size
  • Curative (DDI yields lower burn rate than IPDI)
  • Specific choice of oxidizer or fuel
  • Ballistic modifiers
  • Metal compounds
  • Iron oxides/SFIO, TiO2, Al2O3, copper chromite,
  • Other metal oxides, mixed-metal chromites,
  • Copper phthalocyanine, copper dimethyldithiocarbam
    ate, TPB
  • Catocene, Butacene (ferrocene-substituted HTPB
  • Nonmetal compounds
  • Coolants C (opacifier), Microthene (micronized
  • Combustion stability
  • ZrC, flake graphite, Al2O3 (damping additives)

Additional Ingredients Concerns
  • Processing
  • Ingredient, density, reactivity, particle
    size/packing fraction, solids loading effects
  • Mix procedure, mix temperature(s), order of
    addition, number of additions, blade rpm, blade
    times, vacuum mixing, hold/purge times
  • End-of-mix viscosity, potlife, rheological
    behavior, castability
  • Cast technique, cure temperature, pressure and
    time, cure kinetics
  • Aging behavior
  • Oxidative cross-linking (hardening), hydrolytic
    (typically softening), decomposition, reaction
    with contaminants
  • Effects of temperature, humidity, vacuum,
  • Plasticizer migration, oxidizer dissolution, or
    recrystallization, stabilizer depletion
  • Effect on performance, ignition, mechanical,
    bondline, ballistic, and hazard properties

Propellant CharacterizationBallistic and
Combustion PropertiesMechanical
PropertiesBondline Properties
Propellant Characteristics
  • Ballistic and combustion properties
  • Burn rate, pressure exponent, temperature
    sensitivity (?k)
  • Exponent break, plateau/bi-plateau,
  • Mechanical properties
  • Stress, strain, modulus, stress relaxation
  • Dependence on temperature, pressure and strain
  • Bondline properties (propellant/liner/insulation)
  • Tensile adhesion, peel strength, constant load,
    penetrometer, shear

Propellant Testing
Strand Burner
  • Rationale
  • Motor development depends on knowing propellant
    burning rate
  • Burning rate (in/sec) depends on
  • Composition
  • Pressure
  • Temperature

Motor Static Test
Results St. Roberts Law r a(p)n r burning
rate, a rate coefficient p pressure, n rate
18 Aluminum 89 Total Solids Burning Rate
  • Burning rates curves are typically log-log plots
  • Usually low pressure exponents are desirable
  • Motor is less susceptible to minor perturbations
  • High pressure exponents can sometimes be an
    advantage in propellant extinguishment behavior,

Plateau Propellant Burn Rate Curve
  • Some propellants exhibit low-slope regions called

Temperature Sensitivity (Oberth)
  • The effect of temperature on motor chamber
    pressure is called pk
  • For a given motor geometry at a constant nozzle
    throat area (Kn Ab/At),
  • pk 100 ln (P2/P1)/(T2-T1)
  • Values less than 0.20/F are usually desired

130 F
80 F
30 F
Burning Rate, ips
Thrust Profiles
  • Tactical rocket motors can utilize nearly
    constant thrust, e.g., Sidewinder (minimizes case
  • Space launch boosters like to have regressive
    thrust during operation (decrease by 50 to avoid
    over-acceleration for sensitive payloads) e.g.,
  • Model rockets are exciting with enormous initial
    thrust followed by continued smoke evolution with
    decreased thrust
  • Shoulder-fired anti-tank weapons must have a huge
    acceleration to burn out before missile clears
    the launch tube (up to 1300 gs). Interceptor
    steering motors also need very large thrusts for
    short durations

Propellant grain geometry predominantly controls
the shape of the resulting thrust profile
Solid Propellant Rocket Motor Operation
Propellant burns out from all surfaces
More surface area means more burning propellant
and more thrust
The resulting thrust profile is driven by how the
burning surface area changes over time
Recession of a Linear Surface
V0200264 449
Recession of an Angled, Linear Surface
V0200265 449
Recession of a Curved Surface
V0200266 449
Recession of a Linear and Curved Surface
V0200267 448
Simple Grain Designs
Classification of Grains According
toPressure-Time Characteristics (Sutton Ross)
Grain Dimensions/Designs
Thrust vs Time
Combustion Chambers
Solid-Propellant Grain Designs
5-in. CP Pressure vs Time
Spike Effect At the case wall high concentratio
n of fine ammonium perchlorate (AP) particles
Hump Effect
Hump effect caused by core plunging cast process
Effect of Propellant Temperature on Burning Time
and Chamber Pressure (Sutton Ross)
Change in internal energy changes theburning
rate and energy (impulse) output
Characteristics of Several Grain
Configurations(Rocket Propulsion Elements, 4th
Ed, by Sutton and Ross)
Mechanical Property Control
  • Physical property tailorability is bound by the
    binder type, solids loading and packing fraction
    of the solid ingredients
  • These factors largely are determined early on
    based on mission requirements once established
    physical properties may be tailored by one or
    more of the following
  • Cure agent-to-polymer ratio
  • Cure agent ratio (e.g., difunctional-to-trifunctio
    nal curative ratio)
  • Bonding agent level
  • Plasticizer-to-polymer ratio (if any)
  • Level of noncurative cross-linking agent (if any)
  • Stress enhancing additives
  • Control of environmental variables is important
    to maintain physical properties

Physical Property Testing
  • Rationale
  • Tensile property requirements
  • Cure stress
  • Temperature cycling
  • Motor ignition
  • Flight acceleration
  • Motor storage

Typical values at room temperature Max. stress
80-120 psi Max. strain 35-60 Initial modulus
400-800 psi (Requirements vary with mission)
Typical Stress-Strain Curve
  • Tested across required temperature ranges
  • Tangent modulus
  • Stress at max strain
  • Strain at max stress
  • Strain at failure
  • Shore A (propellant hardness)
  • Many other supporting tests including pressurized
    tests, stress relaxation, etc

Interfaces in Motor
  • From one ideal
  • Three or more

Chemical and Physical Processes in Bonding
HTPB/IPDI Propellants
Time Cure/Aging
Propellant / Wash Coat / Insulation (PLI)
Bondline Tests
  • Analog Flapped Termination (AFT) Specimen
  • Quantitative tensile data for use in generating
    PLI master capability curves
  • Used in determining PLI tensile structural safety
    factors/margins of safety
  • Flapped Lap Shear (FLS) Specimen
  • Quantitative shear data for use in generating PLI
    master capability curves
  • Used in determining PLI shear structural safety
    factors/margins of safety
  • Ninety Degree Peel Specimen
  • Qualitative data for use in establishing bondline
    system baseline
  • Testing is typically more sensitive to cured
    bondline material property changes (I.e
    conservative warning flag to take a look)
    caused by
  • Individual raw material variation
  • Processing environment windows

Performance EvaluationDelivered vs Predicted
Data for Motors
Review of Basic EquationsPressure
Review of Basic Equations Mass Balance
  • Throat area
  • how big is the
  • hole in which the hot
  • gas is coming out?

Burning rate how fast does the propellant
Operating pressure
Grain burning surface area
Characteristic velocity a propellants ability
to produce pressure
Density how heavy is the propellant?
Thrust Equations
  • F v2 (P2 - P3) A2
  • F Pc At Cf (chamber pressure) (throat area)
    (nozzle size)
  • F Isp (weight flow rate) (specific
    impulse miles/gallon of the propellant or total
    push per pound of propellant)

Impulse Equations
  • IT total impulse
  • Area under the thrust-time curve
  • Total push or summed push delivered from
    burning the propellant and expanding the gas
    through a nozzle

Total Impulse Area Under the Thrust-Time Curve
Predicted Pressure at 70F
Thrust-Time Curve Terminology
CP-SPC Motor Pressure-Time
CP-SPC Motor Thrust-Time
CP-SPC Motors Ballistic Performance (Utah
Ambient, 85oF)
Measured From CP-SCP Test Data
Motor3 Motor2 Max
Pressure 1,731 1,756 Avg Pressure 1,263 1,297 M
ax Thrust 1,709 1,746 Avg Thrust 1,242 1,279 A
ction Time 6.95 6.86 Total Impulse 8,628 8,776
Isp 245.2 244.5 Expended Wt 35.2 35.9 Initial
Throat Dia. 0.863 0.862 Final Throat
Dia. 0.941 0.927 Initial Exit Dia. 2.251 2.259 I
nitial Exp Ratio 6.808 6.865 Eros Rate
(mil/s) 4.33 3.54 Ambient Pressure 12.647 12.647
_at_1000 psi

Motor Test Results
  • Predicted FICP
    Measured CP-SPC Measured
  • Burn Rate _at_ 1000psi, 85oF(ips) 0.40 0.4246
  • Burn Rate Exponent - n 0.36 0.3798
  • Propellant Density (lbm/in3) 0.065 0.0633
  • C _at_1,000psi (ft/sec) 5,210 5,093 5,064
  • Vacuum Isp Efficiency () 94.7 93.4 91.6
  • Assumed the same value as calculated from the
    FICP tests
  • ?k (20-120F) 0.18/F was measured in
    70-g motors

Subscale Motor Test ResultsAverage Burn Rate vs
Average Acceleration
Al2O3 particles driven back into the propellant
grain provide the heat/heat transfer to increase
the burning rate
Hazards DeterminationSafety PropertiesShock
SensitivityClassification by DoT/DoDInsensitive
Munition Requirements
Safety Properties
  • Safety/Hazards
  • Ingredients and formulations
  • Stability, chemical incompatibilities
  • Ignition sensitivity to heat, impact, friction,
    spark (uncured and cured)
  • Sensitivity to detonation (confinement, stimulus,
    critical diameter)

ABL Impact
  • 2 kg Weight
  • 1/2-inch DIA Impact Surface
  • MGR Tool Steel
  • Rockwell C50-55
  • 50-70 Microinches/inch
  • Up to 80 cm Drop
  • 3.5cm TIL is moderate
  • 1.8cm TIL is sensitive
  • TIL is 20 Nogo Level

ABL Friction
  • Contact Surfaces - 1/8 THK x 2 DIA Wheel on Steel
  • MGR Tool Steel, Rockwell C50-55, 50-70
  • Up to 800 lbs Load at 8 Feet per Second
  • TILs - 100 lbs at 8 fps is moderate 50 lbs at
    3 fps is sensitive

Unconfined ESD
  • Electrostatic discharge
  • Up to 40 KV
  • J½CV2
  • Up to 8 Joules
  • Any Reaction at 8J is moderate
  • Bulk ignition is Red Line

Data Reduction Helps Make Distinctions
Thiokol SBAT
  • Simulated Bulk Autoignition Test
  • 5 Test Cells and 1 Reference
  • More Sensitive Than DSC Similar to ARC, but
  • Ramp 24 F/hr. Run Reaction to Completion -
    Shows Reaction Severity
  • Exotherm Below 300F is moderate Below 225F
    is sensitive

Thiokol SBAT
  • Simulated Bulk Autoignition Test
  • Insulated Sample Gives Good Indication of Bulk

Thiokol SBAT
  • Simulated Bulk Autoignition Test
  • Thermal Response vs. Temperature

Russian DDT
  • Finds Deflagration to Detonation Susceptibility
    Using 10g Sample
  • Heavy Confinement Means Results Comparable to
    Larger-Scale Tests

Russian DDT
  • Test Article Expands to Show Detonation Run

Russian DST
  • Finds Shock to Detonation Susceptibility Using
    10g Sample
  • Heavy Confinement Means Results Comparable to
    Larger-Scale Tests

3-Inch DDT
  • Standard, Full-Scale Deflagration-to-Detonation
  • Witness is Based on Pipe Fragmentation

NOL Card Gap
  • Standard Shock Sensitivity Test
  • Number of Plastic Cards is Varied Shock is
  • Witness is Clean Hole Punched in Steel Plate

Propellant Hazard Classification
  • All current solid rocket propellants are divided
    into two hazard classifications (1.1 or 1.3)
  • Two tests historically used to screen for 1.1 and
  • Defining document TB 700-2 now requires
    different testing

Hazard Classification of Rocket Motors
  • Hazard Division assignments for storage and
    transportation of rocket motors are based on the
    response to TB 700-21 UN Test Series 6
  • Internal ignition or initiation
  • Propagation of burning or explosion
  • Response in a fast cook-off fire test
  • Response to testing
  • HD 1.1 Result is an explosion of the total
  • HD 1.2 Major hazard is that from dangerous
  • HD 1.3 Radiant heat and/or violent burning but
    with no dangerous blast or projection hazard
  • HD 1.4 Small hazard in the event of ignition or
    manufactured with the view to production and
    explosive or pyrotechnic effect
  • Historically, most rocket motors have fallen in
    HD 1.1 or 1.3, either by test or by analogy
  • 1. Department of Defense Ammunition and
    Explosives Hazard Classification Procedures
    Joint Technical Bulletin TB 700-2/NAVSEAINST
    8020.8B/TO 11A-1-47DLAR 8220.1

Why Do We Care How Future Motors Are Classified?
  • Need to establish the detonation hazard
  • If HD 1.1, infrastructure would need to change
    for many large motor systems
  • Much more real estate (QD restrictions) and
    greater support handling cost
  • Uses restricted for HD 1.1
  • Space launch community has been unwilling to even
    consider HD 1.1 rockets
  • Test ranges want no part of a 1.1 system
  • Satellite launch facilities not designed for 1.1
  • Need to provide best possible capabilities for
    future military/commercial uses

TB 700-2 Has Seen Several Revisions
  • DoD Hazard Classification Protocol was reissued
    in 1998
  • Nominal test protocol impractical and extremely
    expensive (up to 12 full-scale assets required)
    for large solid rocket motors a full-scale
    bonfire test was and still is required (no
    acceptable subscale analog test specimen for
    bonfire testing)
  • Alternate test protocol (8-in SLSGT) imposed
    severe shock sensitivity requirements
  • After input from the propulsion community, the
    DDESB modified test procedures for large rocket
    motors in January 2002
  • Changes were made to the alternate test protocol
  • Shock tests less severe than the 8-in SLSGT could
    be performed in lieu of single package test and
    stack test, but NO DATABASE existed for the new
  • A full-scale bonfire test is still required
  • Another revision, November 2005, is currently
    in work which may require even more stringent
    shock test requirements
  • Community (government, industry, JANNAF, DDESB,
    and JHC) discussions and interaction needed to
    realize credible testing requirements

Alternate Test Protocol January 2002 Rev
  • Shock sensitivity test options provided to be
    performed in lieu of single package test and
    stack test
  • Option 1 8-in SLSGT, same as before
  • Best suited for large boosters using propellants
    without energetic binders/additives, large
    critical diameter (Dc gt 14-in)
  • Option 2 Gap Test at 70 kbar, 150 Dc, motor
    confinement, no less than 5-in diameter
    regardless of Dc
  • First must determine Dc
  • Best suited for large boosters using propellants
    with energetic binders/additives
  • Option 3 Gap Test at 70 kbar, motor diameter,
    motor confinement
  • Best suited for smaller, tactical rocket motors

Case Selection
  • Alternate Protocol Option 2 calls out testing
    to be conducted at equivalent motor confinement
  • Composite case selected
  • Capable of 2000 psi (closed ends)
  • 5-inch diameter by 20-inch long cylinder
  • Photo at right compares this to standard NOL LSGT
  • 5.5-in long, 1.9-in OD
  • Used for 30 years

Shock Test Results 5-inch
  • Moderate nitramine, nitrate ester, NOL LSGT 70
  • 5 x 20 cylinder
  • Input pressures tested 105, 70, and 34 kbar

34 kbar no go
70 kbar no go
  • Results
  • No Go in 34 and 70 kbar tests remaining
    propellant did not burn
  • Go at 105 kbar
  • 5-inch test required per TB700-2 Alt Protocol
    pass as HD1.3 for shock

105 kbar go
Reaction Velocity vs DistanceHTPB 5-inch Shock
Distance, inches
  • Velocity data (crush pins) match results of
    plate damage
  • HTPB-2 tested at 128 kbar appears to be very
    near the threshold

Safe Handling of Rocket Motors
Susceptibility to Shock to detonation Impact
Deflagration to detonation Delayed
detonation Thermal Friction Electrostatic
Hazard Scenario Sympathetic detonation
or direct hit Transport crash, stage
drop Propellant damage/combustion Hard surface
impact/recompression Fire Stage drop and
slide Pulling tarp off motor
Insensitive Munitions
  • Different than hazard classification
  • Includes in-service hazards

IM Reaction Types By MIL-STD-2105C
SEVERE - - - - - - - - - - - - - - - - - - - -
(Reaction Response) - - - - - - - - - - - - - - -
- - - - - MILD
Type III Explosion Reaction Pressure bursts of
confined energetic material due to rapid burning
air shock and high velocity fragments can damage
nearby structures
  • MS propellants react violently to shock and
    impact stimuli

Type I - Detonation Reaction Supersonic shock
wave through energetic material with capability
for large ground craters fragment and blast
overpressure damage to structures
Type V Burning Reaction Ignites and burns
non-propulsively no fatal fragments beyond 50
Type IV Deflagration Reaction Low pressure
rupture of confining structure or expulsion of
closures no significant fragmentation, energetic
material may be thrown about with heat and smoke
damage to surrounding propulsion of munition
might occur
  • MS propellants typically react less violently to
    thermal stimuli
  • RS propellants react violently to thermal stimuli

Type II Partial Detonation Damage depends on
the portion of the energetic material that
Shaped Charge Jet Setup
SCJ Test Arrangement
PCB Over-pressure gauges
30 ft
15 ft
7.5 ft
191 mm stand-off
65 mm Viper SCJ (191 mm stand-off)
200 ft
  • Metal banding loosely connected to secure motor
    on plywood stand
  • 0.75-Inch thick mild steel witness plate placed
    below motor

Shaped Charge Jet Results
  • Large section of motor (75 mass) fell off stand
    and moved 8 ft away
  • No metal fragments released
  • Sample burned until completely consumed
  • Witness plate showed no damage
  • Smaller fragment (25 mass) flew 18 ft away
  • Sample burned until completely consumed
  • No over-pressure detected from motor (8 psi
    recorded from SCJ)

Fragment Impact Set-up
Army-FI Test Arrangement
PCB Over-pressure gauges
30 ft
15 ft
7.5 ft
50 ft stand-off
20 mm cannon
200 ft
  • Metal banding loosely connected to secure motor
    on plywood stand
  • 0.5-Inch thick mild steel witness plate placed
    below motor

Fragment Impact Results
  • Motor burned on stand all propellant remained in
  • Composite section fragments (no insulation or
    propellant) thrown approximately 15 39 ft
  • No metal fragments released
  • No over-pressure detected on any gauges

Bullet Impact Set-up
BI Test Arrangement
PCB Over-pressure gauges
30 ft
15 ft
7.5 ft
40 ft stand-off
12.7 mm gun
200 ft
  • Metal banding loosely connected to secure motor
    on plywood stand
  • 0.5-Inch thick mild steel witness plate placed
    below motor

Bullet Impact Results
  • Three small burning objects observed immediately
    after impact
  • Flew toward back of test area and consumed very
  • Mass and velocity unknown
  • Motor burned on stand
  • Many small pieces of composite section (no
    insulation or propellant) thrown about area
  • No metal fragments released
  • No over-pressure detected on any gauges

Bullet entrance hole
Bullet exit hole
  • Solid propellants can be formulated to cover a
    wide variety of applications
  • Performance ranges and hazards properties
    (ingredients selected) driven by system needs
  • Research continues on new ingredients-more energy
    with less hazards sensitivity is the holy grail
  • Offer tailorability of burn rates and mechanical
    properties to meet motor requirements
  • Hazards characterization for shipping and
    storage, and required IM compliance represent
    further challenges to meeting performance goals

  • Principles of Solid Propellant Development,
    Adolf E. Oberth, CPIA Publication 469, September,
  • Explosives, 3rd Revised and Extended Edition,
    Rudolf Meyer, 1987
  • Fundamentals of Solid Propellant Combustion, Ken
    Kuo and Martin Summerfield, AIAA, 1984
  • Rocket Propulsion Elements Fifth Edition,
    George P. Sutton, John Wiley Sons, 1986
  • Department of Defense Ammunition and Explosives
    Hazard Classification Procedures, TB 700-2,
    NAVSEAINST 8020.8B, TO 11A-1-47 DLAR 8220.1,
    January 2002 Revision
  • Hazard Assessment Tests for Non-Nuclear
    Munitions, MIL STD 2105C, 14 July 2003
  • Computer Program for Calculation of Complex
    Chemical Equilibrium Compositions, Rocket
    Performance, Incident and Reflected Shocks, and
    Chapman-Jouguet Detonations, S. Gordon and B.
    McBride, NASA SP-273, March 1976

Basic Terminology
  • Surface area (As), in2 area of exposed grain
  • Throat area (At), in2 area of nozzle throat
  • Burning rate (aT ), in/sec burning rate
    referenced to 1 psia
  • Center perforated seventy pound charge (CP SPC)
    test motor containing approximately 40 lbs of
  • Characteristic velocity (C ), ft/sec ability
    of the propellant to produce gas flow
  • Propellant density (?) density given in lb/in3
    or g/cc
  • Deflagration to detonation test (DDT) measures
    ability to transition from rapid burning to
  • Detonation susceptablity test (DST) measures
    sensitivity to shock
  • Thrust (F), lbf the push generated from
    internal gas pressure and accelerating hot gases
    through a nozzle
  • Impulse (IT), lbf-sec the total or summed
    push over a given operating time
  • Specific impulse (Isp), lbf-sec/lbm how much
    push is delivered by one pound of propellant (
    equates to a miles/gallon term)
  • Burning rate exponent (n) slope of the log-log
    plot of burning rate versus pressure
  • Pressure (Pc), psia the internal force created
    by burning propellant gases
  • Burning rate (rb), in/sec or mm/sec regression
    rate of propellant surface at a given pressure
  • Burn time (tb), sec the time at which the motor
    has burned through its (minimum) web thickness
    (also known as web burn time)
  • Action time (ta), sec user specified useful
    operation time
  • Total time (tt), sec time at which no more
    pressure or thrust is generated
  • Incremental velocity (DV), ft/sec the amount
    of velocity or kick imparted by the rocket
    motor to the system