Propellant Fundamentals

1
Propellant Fundamentals

• Dr. Carol Campbell
• Senior Scientist, Team Leader
• ATK Launch Systems
• Email carol.campbell_at_atk.com

2
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
  programs
• 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

3
Overview

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

4
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

5
Solid Rocket Motor Overview
6
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
shape
7
Solid Motor Applications
Space Shuttle
Minuteman III
Trident II (D5)
Castor 120
Hydra 70
8
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

9
Solid Rocket Components
10
How Thrust Is Created

• Propellant burning in chamber raises chamber
  pressure
• Pressure difference causes gases to accelerate
  from chamber and through nozzle at high speed

11
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
12
Propellant RequirementsFundamentalsIsp,
DensityBallistic and Mechanical Properties
13
What Makes a Rocket Operate?

• Four things to know
• Newtons first law
• Newtons second law
• Newtons third law
• Boyles Law

14
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
  reaction

?
15
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

Drag
Weight
16
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)

Drag
Velocity
Weight
17
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

Drag
Velocity
Weight
Mass Flow
18
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
19
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

20
Idealized Thrust Equation
Pa - ambient pressure
At - throat area
Pe - exit pressure
Ae - nozzle exit area
Momentum change
Thrust
Pressure thrust
Optimum nozzle expansion ratio (? Ae/At) when
Pe Pa
21
Specific Impulse What and Why

• Impulse (I) is thrust x time
• Longer duration thrust increases rocket speed,
  but
• 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
mi/mf
22
Thrust Increases with Altitude

• As the missile ascends, the ambient pressure
  decreases so the pressure thrust contribution
  increases

• This effect is important in nozzle design

23
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

Density impulse ? Isp (N-sec/m3 or lbf-sec/in.3)
24
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
  code
• Input molecular formula, heat of formation,
  density for each ingredient in ingredient
  database
• 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

25
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
time
26
There Are Multiple Ways to Drop UsedPropulsion
Hardware Mass
27
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
  separation)

28
Where Do Ballistic and Mechanical Properties Fit?

• Ballistic properties (burn rate and dependence of
  the burn rate on pressure and temperature) affect
  performance
• 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
  insulation
• Interdependence for optimum performance

29
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
lsp
High ? Lightweight materials Low factors of
safety Highly stressed Highly integrated
structure
For smallest volume system, engineers seek high
density lsp
30
Formulation FundamentalsIngredientsTailoring
Formulations
31
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
Fuel
Ignition Source
Oxygen
The Combustion Triangle
32
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
  processing)
• Composite modified (energetic solids added to
  NC/NG)
• 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
  properties
• Homogeneous propellants are often minimum-smoke
  detonable
• 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
  prepolymers

33
Application Will Determine Ingredients

• Plume signature
• Minimum smoke (no metal fuel, no HCL, limited
  condensables)
• 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

34
Propellant Class By Signature
35
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

36
Smoky Propellants
37
Minimum and Reduced-Smoke Propellants
38
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
39
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)
40
Composite PropellantsEnergetic Prepolymers

• Polymer contains energetic functional groups
• Nitro (-NO2) , nitrato (-ONO2) , azido (-N3) ,
  nitramino (-NNO2), difluoroamino (-NF2)
• Energetic prepolymers are normally
  hydroxyl-terminated
• Polyglycidyl nitrate (PGN or polyGlyn)
• Glycidyl azide polymer (GAP)
• Polyoxetanes
• Azidomethylmethyloxetane (AMMO)
• Bis(azidomethyl)oxetane (BAMO)
• Nitratomethylmethyloxetane (NMMO)

41
Composite PropellantsBinder System Ingredients

• Prepolymer (see prior charts)
• Curative
• Provides chain extension and/or cross-linking of
  prepolymer
• 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
  temperature
• 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
  oligomer)
• Trimethyolpropane, TP4040 (hydroxyl
  functionality)

42
Composite PropellantsBinder Ingredients
(Continued)

• Bonding agent
• Promotes adhesion between binder and solid
  particles
• 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
• BTTN, TMETN, DGTN, NG, GAPP, BuNENA, BDNPA/F
• Stabilizers
• Antioxidants, thermal stabilizers, free radical
  scavengers, metal sequestering agents, other
• Processing aids
• Cure retarder (e.g., pyrocatechol), isocyanate
  blockers
• ODI, lecithin, moisture (with extreme care),
  silicone oil

43
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

44
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

45
Composite PropellantBallistic Additives and
Control

• 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,
  FeF3
• Other metal oxides, mixed-metal chromites,
  ferrocyanides
• Copper phthalocyanine, copper dimethyldithiocarbam
  ate, TPB
• Catocene, Butacene (ferrocene-substituted HTPB
  prepolymer)
• Nonmetal compounds
• Coolants C (opacifier), Microthene (micronized
  polyethylene)
• Combustion stability
• ZrC, flake graphite, Al2O3 (damping additives)

46
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,
  atmosphere
• Plasticizer migration, oxidizer dissolution, or
  recrystallization, stabilizer depletion
• Effect on performance, ignition, mechanical,
  bondline, ballistic, and hazard properties

47
Propellant CharacterizationBallistic and
Combustion PropertiesMechanical
PropertiesBondline Properties
48
Propellant Characteristics

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

49
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
exponent
50
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,
  dp/dt

51
Plateau Propellant Burn Rate Curve

• Some propellants exhibit low-slope regions called
  plateaus

52
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)
  /F
• Values less than 0.20/F are usually desired

130 F
80 F
30 F
Burning Rate, ips
Pressure
53
Thrust Profiles

• Tactical rocket motors can utilize nearly
  constant thrust, e.g., Sidewinder (minimizes case
  weight)
• Space launch boosters like to have regressive
  thrust during operation (decrease by 50 to avoid
  over-acceleration for sensitive payloads) e.g.,
  Shuttle
• 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
54
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
55
Recession of a Linear Surface
V0200264 449
56
Recession of an Angled, Linear Surface
V0200265 449
57
Recession of a Curved Surface
V0200266 449
58
Recession of a Linear and Curved Surface
V0200267 448
59
Simple Grain Designs
-
60
Classification of Grains According
toPressure-Time Characteristics (Sutton Ross)
61
Grain Dimensions/Designs
62
Thrust vs Time
63
Combustion Chambers
64
Solid-Propellant Grain Designs
65
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
66
Effect of Propellant Temperature on Burning Time
and Chamber Pressure (Sutton Ross)
Change in internal energy changes theburning
rate and energy (impulse) output
67
Characteristics of Several Grain
Configurations(Rocket Propulsion Elements, 4th
Ed, by Sutton and Ross)
68
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

69
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)
70
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

71
Interfaces in Motor
COMPLEX BONDING SYSTEM

• INTERFACES
• From one ideal
• Three or more

72
Chemical and Physical Processes in Bonding
HTPB/IPDI Propellants
73
Time Cure/Aging
MIGRANTS B BONDING AGENT C CURATIVE
H2O PLASTICIZER BURN RATE CATALYST
74
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

75
Performance EvaluationDelivered vs Predicted
Data for Motors
76
Review of Basic EquationsPressure
77
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
burn?
Operating pressure
Gravity
Grain burning surface area
Characteristic velocity a propellants ability
to produce pressure
Density how heavy is the propellant?
78
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)

79
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

80
Total Impulse Area Under the Thrust-Time Curve
81
Predicted Pressure at 70F
82
Thrust-Time Curve Terminology
83
CP-SPC Motor Pressure-Time
84
CP-SPC Motor Thrust-Time
85
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

86
Motor Test Results

• Predicted FICP
  Measured CP-SPC Measured
• Burn Rate _at_ 1000psi, 85oF(ips) 0.40 0.4246
  0.4206
• Burn Rate Exponent - n 0.36 0.3798
  
• Propellant Density (lbm/in3) 0.065 0.0633
  0.0642
• 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

87
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
88
Hazards DeterminationSafety PropertiesShock
SensitivityClassification by DoT/DoDInsensitive
Munition Requirements
89
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)

90
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

91
ABL Friction

• Contact Surfaces - 1/8 THK x 2 DIA Wheel on Steel
  Plate
• MGR Tool Steel, Rockwell C50-55, 50-70
  Microinches/inch
• 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

92
Unconfined ESD

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

93
Data Reduction Helps Make Distinctions
94
Thiokol SBAT

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

95
Thiokol SBAT

• Simulated Bulk Autoignition Test
• Insulated Sample Gives Good Indication of Bulk
  Response.

96
Thiokol SBAT

• Simulated Bulk Autoignition Test
• Thermal Response vs. Temperature

97
Russian DDT

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

98
Russian DDT

• Test Article Expands to Show Detonation Run
  Distance

99
Russian DST

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

100
3-Inch DDT

• Standard, Full-Scale Deflagration-to-Detonation
  Test
• Witness is Based on Pipe Fragmentation

101
NOL Card Gap

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

102
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
  1.3
• Defining document TB 700-2 now requires
  different testing

103
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
  contents
• HD 1.2 Major hazard is that from dangerous
  projections
• 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

104
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
  systems
• Need to provide best possible capabilities for
  future military/commercial uses

105
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
  tests
• 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

106
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

107
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
  pipe
• 5.5-in long, 1.9-in OD
• Used for 30 years

108
Shock Test Results 5-inch

• Moderate nitramine, nitrate ester, NOL LSGT 70
  cards
• 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
109
Reaction Velocity vs DistanceHTPB 5-inch Shock
Tests
1.0
12.2
19.2
5.2
Distance, inches

• Velocity data (crush pins) match results of
  plate damage
• HTPB-2 tested at 128 kbar appears to be very
  near the threshold

110
Safe Handling of Rocket Motors
Susceptibility to Shock to detonation Impact
Deflagration to detonation Delayed
detonation Thermal Friction Electrostatic
discharge
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
111
Insensitive Munitions

• Different than hazard classification
  (shipping/storing)
• Includes in-service hazards

112
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
feet
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
detonates
113
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

Video
114
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)

115
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
Video

• Metal banding loosely connected to secure motor
  on plywood stand
• 0.5-Inch thick mild steel witness plate placed
  below motor

116
Fragment Impact Results

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

117
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

Video
118
Bullet Impact Results

• Three small burning objects observed immediately
  after impact
• Flew toward back of test area and consumed very
  rapidly
• 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
119
Summary

• 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

120
Bibliography

• Principles of Solid Propellant Development,
  Adolf E. Oberth, CPIA Publication 469, September,
  1987
• 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

121
Basic Terminology

• Surface area (As), in2 area of exposed grain
  surface
• Throat area (At), in2 area of nozzle throat
  opening
• 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
  propellant
• 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
• 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