Moisture Resistant Black Powder Substitute and Its ...

Moisture Resistant Black Powder Substitute and

Its Application as Center-Perforated Pellets in

Mortar Ignition Cartridges

Mr. Gary Chen, TACOM ARDEC and

Dr. Reed J. Blau, ATK Thiokol Propulsion, Company LLC

26 March 2003

38th Annual Gun, Ammunition and Missiles Symposium and Exhibition

Leadership Teaming Communication

Employee Support Strategic Thinking Organizational Climate

THIOKOL PROPULSION

THIOKOL PROPULSION

Background

TACOM ARDEC

q Black powder is still an important energetic used in many military applications

l The BP formulation is thousands of years old.

l It is an important component in ignition, propulsion, and explusion trains of modern weapons systems.

? Over 100 military components distributed by JMC require BP.

? Estimated annual consumption 100,000 lbs (75mm Saluting Charge, 155mm MACS Prop Charge, Grd Illum Signals, etc.)

q Certain limiting characteristics make it highly desirable to replace BP in some or all of these components, e.g.,

l Moisture absorption

l Safety during its production

l Reproducibility ? lot to lot and charcoal variations

THIOKOL PROPULSION

Background

TACOM ARDEC

q Properties of a suitable BP replacement include:

l Greater Resistance to Moisture Absorption

? Maintain ballistic performance ? Minimize corrosion of nearby metallic components ? Minimize loading and storage costs

? Less stringent temperature and humidity controls ? Decreased frequency of component inspections

l Charcoal-Free

? Performance problems in BP have coincided with changes in production of the charcoal used therein. Variability may arise due to:

? Wood type and growth history

? Process creep in production parameters ? Moisture absorption even at low relative humidity

l Sulfur-Free

? BP combustion produces sulfur dioxide ? toxic by inhalation, acid rain precursor

l Processing Requiring Fewer Attended Operations

? Minimizes risk of operator fatalities during production

l Drop-In Replacement

? Minimizes component redesign and qualification costs

THIOKOL PROPULSION

Moisture Resistant

Black Powder Substitute (MRBPS)

TACOM ARDEC

q Formulation does not contain charcoal or sulfur

q Principal Constituents of Formulation Family

l Potassium Nitrate (KNO3) is the Principal Oxidizer

? The same as in black powder

l Auxiliary Oxidizer is Potassium Perchlorate

? Adds brisance to the MRBPS formulation ? Allows an added degree of freedom for performance tailoring

l Phenolphthalein replaces Charcoal as the Fuel

? Structurally related to charcoal ? Notable for promoting short rise times as a fine powder

Structure of Phenolphthalein

? Absorbs significantly less moisture than charcoal under comparable conditions

l Ethyl Cellulose is added as a Process Aid/Binding Agent

? As binder to hold fuel and oxidizers together ? Additive allows remote continuous processing of MRBPS via twin-screw extrusion

? Will provide lubrication lowering torque required for extrusion ? Eliminates phase separation between MRBPS solids and the processing solvent, ethanol

? Absorbs minimal moisture

l Heat of Explosion (798 kcal/g) is comparable to that of black powder (810 kcal/g)

l Pressure exponents are somewhat higher for MRBPS (0.33) than BP (0.20)

THIOKOL PROPULSION

Moisture Absorbtion %

1.4

1.2

1

0.8

0.6

0.4

0.2

0

0

1

2

Moisture Absorption Measurements

TACOM ARDEC

75% RH/Ambient Temperature & 120 F:

BP Pellet-1 RM/75%RH MRBPS Pellet-1 RM/75%RH BP Granule-1 RM/75%RH MRBPS Granule-1 RM/75%RH

? Ambient temperature- BP and MRBPS reached equilibrium at 1.2% and 0.2% respectively after 3 days. ? 120 F- BP and MRBPS reached equilibrium at 1.4% and 0.2% respectively after 1 day. ? No significant difference in moisture absorption between pellets and granules.

90%RH/30C (Mil-STD-286 C, Part 503.1.3):

? BP and MRBPS pellets absorbed 5.3% and 1.5%

moisture respectively after 18 days. Similar moisture absorption pattern occurred for granules.

3

4 Day 5

6

7

8

9

10

Moisture Absorption %

1.8

6

BP Pellet-1 30C/90RH

1.6

5

BP Granule-1 30C/90RH

1.4

Moisture Absorption %

1.2

BP Pellet-1 120F/75%RH

4

MRBPS Pellet-1 30C/90RH

1

MRBPS Pellet-1 120F/75%RH

MRBPS Granule-1 30C/90RH

3

0.8

BP Granule-1 120F/75%RH

0.6

2

MRBPS Granule-1 120F/75%RH

0.4

1 0.2

0

0

0

1

2

3

4

5

6

7

8

9

10

0

Day

5

10

15

20

Day

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