Origin of Test Requirements and Passing Criteria for the Qualification of Propellants
Ken Tomasello; Navy Insensitive Munitions Office; Indian Head, MD USA
John Adams; Associate, Booz Allen Hamilton; Arlington, VA USA
Michael Sharp; MSIAC/NATO, Brussels, Belgium
Keywords: Explosives, Explosives Safety, Origin of Test Requirements, Insensitive Munitions, Solid and Liquid
Propellants, Explosive Qualification and Final (Type) Qualification
Abstract: The development of explosives requires a rigorous regimen of tests, both small-scale, and large-scale, before explosives can be judged safe and suitable for service use. The U.S. Department of Defense (DoD) requires that all energetic materials be Qualified and Final (Type) Qualified in accordance with NATO STANAGs 4170 and
4439, with guidance provided in the associated AOPs 7 and 39 for implementing policy. Questions are often raised during program development and reviews as to the origin and applicability of tests, and pass/fail criteria required by the military services. This paper is the result of a review of historical documents, including many documents detailing European explosive history. We define the term Qualification as used originally, and attempt to put in perspective the purpose of test requirements and any associated pass/fail criteria. Our goals are to put the qualification of explosive in a historical context, and to stimulate discussion within the energetic material community as to the validity of these requirements in our current work environment. This paper, the third in a series, will only address Qualification requirements for solid and liquid propellants. It explores each test and examines the genesis of the test requirements and pass/fail criteria.
Acknowledgements: We would like to thank Ray Beauregard, who drafted and staffed the covering Navy instructions for NAVORD OD 44811and participated in its preparation, for his guidance and counseling in the history and early development of explosive qualification requirements. We would also like to thank Roger Swanson and Emmanuel Schultz of MSIAC NATO who provided a list of international contacts, which was used to expand the international content of this paper.
Introduction
One of the truisms of the explosives profession is that explosives sensitivity tests that lead to a decision on whether an explosive material is safe (suitable) for production and use in military applications is generally based on experience gained from accidental and often catastrophic events. In the very early stages of their development and use, people discovered that explosive materials could be initiated accidently by stimuli such as friction, impact, fire and sparks. The unintended reactions often resulted in loss of life and destruction of facilities. We can assume that a short time after accidents happened, the incidents were recorded in some way, and steps were taken to avoid reoccurrences. The British Government responded to a disastrous explosion at Birmingham that killed 53 people by passing the “Explosives Act” in 1875 1 (DoA 1990). A striking modern example is the disastrous explosion that took place on 10 July 1926 at the Lake Denmark Naval Powder Depot (Picatinny Arsenal, USA), which led the U.S.
Congress to establish the “Joint Army-Navy Storage Board” in December 1927. This Board eventually became what is known today as the Department of Defense Explosives Safety Board (DDESB).
There are often questions raised during program development and reviews on the evaluation process, and technical requirements imposed by the Services. The tests, their origin, the applicability, and pass/fail criteria required by the military services are not always understood. This paper is the result of a review of historical documents, and interviews with members of the energetic materials community who were instrumental in developing the requirements. It explores each test and examines the genesis of the test requirements and pass/fail criteria assigned.
To address this, we must first define the term Qualification and later attempt to put in perspective the purpose of test requirements and any associated pass/fail criteria. Qualification results from assessment of the sensitivity of an
1 An abstract of The Explosives Act of 1875 can be found in Appendix D of A Handbook on Modern Explosives (M.
Eissler 1890)
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explosive based on relativity small-scale, standardized laboratory tests to determine whether an explosive material possesses properties that makes it safe and suitable for limited production and may be considered for further tests in military application hardware. (NATO 2008)
This paper will address mandatory small-scale Qualification requirements for solid and liquid propellants. In this review propellant will be referred to as either “Solid Gun Propellant”, “Solid Rocket Propellant”, or “Liquid
Propellant”, depending upon the particular application. In accordance with the NATO definition, a Solid Gun
Propellant is a “substance, or mixture of substances, that is required to burn in a controlled manner within a gun combustion chamber producing hot gases capable of propelling a projectile at high velocity. Combustible cases may also be included as they contribute to the overall energy of the propellant”. (NATO 2008) In accordance with the
NATO definition from the same reference, a Solid Rocket Propellant is a “substance (or a mixture of substances) that is required to burn in a controlled manner within a rocket motor producing hot gases that are vented through a nozzle to propel the munition. Propellants used in cartridge activated or other non-propulsive devices are also included in this category.” And finally, also from the same reference, the NATO definition of Liquid Propellant is a
“substance (or a mixture of substances) that is required to react in a combustion chamber in controllable manner in order to generate propulsive force. These may be monopropellants, bi-propellants or hybrids comprised of liquids and solids.”
Mandatory small-scale Qualification and Insensitive Munitions (IM) Final (Type) Qualification requirements for main charge explosives were addressed in a previous paper (K. M. Tomasello 2010), and primary and booster explosives were also previously discussed (Tomasello, Adams and Sharp 2011). Qualification of pyrotechnics will be addressed in a future paper. A roadmap of explosives test requirements is shown in Figure 1. This figure illustrates what has already been addressed, what is being addressed in this paper, and what is planned for the future.
Figure 1. Roadmap of Explosives Test Requirements
Background
Historically, at least before WW II, the evaluation and approval of a new explosive was a two-step process.
Laboratory studies on thermal and mechanical sensitivity were conducted on new explosives, and then an evaluation under simulated field conditions was made before the acceptance for field use (Noyes 1948).

During and after WW II there was a great deal of interest among the laboratories in Australia, Canada, the UK and the U.S. (The Technical Cooperation Program (TTCP) countries) to standardize tests used to evaluate the sensitivity of explosives to mechanical and thermal stimuli. In the 1950s and 60s there was a very active TTCP Panel 0-2
(Explosives) that met formally at least once a year. Among other things, the panel was interested in trying to standardize some of the laboratory sensitivity tests and to this end, established a panel.
2 In February 1966 the Panel published the “Manual of Sensitiveness Tests”. The preface states: “…this document should be the first step towards achieving standardization of sensitiveness tests.” It is not surprising that the tests selected by the Panel were impact, friction, shock, and fragment/bullet impact since these were some of the basic tests that had been used in one form or another by the explosives community before World War I and thereafter (Marshall 1917).
Although the DDESB had years earlier developed tests and thresholds for explosives acceptance for transportation and storage, it wasn’t until 1972 that formal qualification procedures for explosives were documented and formalized by the U.S. Services. However, even as early as 1892, there was awareness that “explosive substances should be capable of being handled and transported by road or railway with at least relative safety”. (Berthelot 1892)
This carried over to the Bureau of Mines as they realized explosive qualities such as stability were important in making an explosive reasonably safe to handle and transport. (Hall, Snelling and Howell 1912) Testing also started in two branches of the service: “In 1909 the Navy’s surveillance test at 65.5°C was adopted, and in 1910 the joint
Army and Navy Board that had been appointed in 1906 issued its first set of joint specifications for the two branches of the service.” (Van Gelder and Schlatter 1927) The only laboratory-level pass/fail criteria for the explosive material that existed before NAVORD OD 44811 (DoN 1972) were in explosives Hazard Classification (HC) documents. OD 44811 and its covering Instructions established criteria for the Safety and Suitability 3 for Service
(S3) use of Navy explosives. (Beauregard and Gryting 1972) Following the publication of this document, the Joint
Technical Coordinating Group (JTCG) for Munitions Development Working Party for Explosives issued it as ADA-
086259 (JTCG 1972), thus promulgating a Tri-Service agreement on procedures to qualify primary, booster and main charge explosives for service applications. Both of these documents were superseded by MIL-STD-1751 4 , and now by the U.S. section of NATO AOP-7 Edition 2 Rev. 3 (NATO 2008).
What was new with NAVORD OD 44811 and its covering instructions was that now the historical process was formalized, terms were defined, and for the first time, any new application of an explosive whether new or previously used in other applications had to be reviewed and approved at the General/Flag Officer level. One might ask the question: “Why in the early seventies was there the sudden interest in imposing new requirements on munitions and explosives community?” To answer that question one should consider that the preparation of
NAVORD OD 44811 was during the 1970 to 1972 period. In a four-month period, between 9 July 1969 and 7
November 1969, there had been four in-bore detonations of Navy 5-inch gun projectiles, bombs/warheads had detonated in fuel fires on three aircraft carriers, and a cargo ship loaded with bombs had exploded. As a result, there was great deal of concern in the services, especially the Navy, about the sensitivity of explosives and about their safe use in munitions (R. L. Beauregard 2005).
2 This panel eventually disappeared as a result of a TTCP reorganization, however the work continues within TTCP.
3 STANAG 4629, Safety and Suitability for Service Assessment Testing of Non-Nuclear Munitions, provides guidance on the management of S3 assessment testing for conventional munitions and to standardize the S3 assessment testing processes. STANAG 4629 incorporates AAS3P-1, Allied Ammunition Safety and Suitability for
Service Assessment Testing Publication – Guidance, by reference. AAS3P-1 incorporates STANAG 4439 and AOP-
39 by reference. The Main Group (MG) approved STANAG 4629 to be sent out through the documentation division for national ratification; The MG approved AAS3P-1 for release and is also going through the ratification process.
4 The content of OD-44811 was divided into two parts: Interim Qualification, which in NATO became
Qualification, and Qualification, which eventually became Final (Type) Qualification in NATO. AOP-7 covers
Qualification tests; the Final (Type) Qualification tests are covered in MIL-STD-2105D (DoD 2011).

Qualification Tests for Solid Gun Propellants
The U.S. DoD first defined Qualification requirements for explosive materials in NAVORD OD 44811 and ADA-
086259 5 , which was the tri-service version. This was to assure that the materials approved were safe 6 and suitable for production and could be considered for service use in the roles identified. The roles identified were primary, booster and main charge explosives. Propellants and pyrotechnics were not covered in the OD or the AD. These documents contained advisory and mandatory pass/fail criteria for selected tests.
The focus of this section will be the rationale for mandatory qualification tests and pass/fail criteria (Table 1) for solid gun propellants as identified in MIL-STD-1751A 7 (DoD 2001), STANAG 4170 (NATO 2008), and AOP-7
(NATO 2007).
Chapter 2 of Military Explosives (DoA 1990) provides some history related to military applications of energetic material, including some historical aspects of testing of energetic materials, which includes propellants. In 1578,
Bourne of England devised an instrument for testing gunpowder. In 1627, an improved instrument for testing black powder was devised by Curtenbach and described by him in his Halinitro Pyrobolia in 1627. In 1647, testing the strength of gunpowder, by firing a ball from a mortar and measuring the distance the ball travelled, was proposed by
Master-Gunner Nye in his "Art of Gunnery." This mortar test was adopted by France and other countries soon afterward. Robins (1742) improved on a closed bomb for testing the power of an explosion. In 1904, the
Obermueller Stability Test, “which consisted of heating 1-2 grams of nitrocellulose in a small tube under vacuum at
135-140° and measuring the pressure of evolved gas by vacuum manometer”, was introduced.
Berthelot, in the translation from the French, enumerated the most essential conditions that comprise the tests of stability, which are stability on exposure to air, neutrality, exudation, shock, immersion, and heat. Berthelot also discusses the sensitiveness of explosive substances “depends both on condition of heating, and on the mode of propagation of the reactions”. (Berthelot 1892) Guttmann, in his report to Congress, mentioned that in 1534 was the
“first instance of a nitrated organic substance having been used as a propellant”. (Guttmann 1909) Guttmann also described several characteristics of explosives for use in firearms – propelling power, stability, sensitiveness to shock, and deterioration when stored. (Guttmann 1906) Barnett noted that some of the first-class powers used only nitroglycerine propellants (Great Britain and Italy), some used nitrocellulose powders only (France, Russia, U.S.), and some used both (e.g. Germany). Barnett stated: “As the best test of a propellant is its prolonged trial under use, the war should furnish interesting data as to the relative merits of the two classes of powders”. (Barnett 1919)
Marshall noted that propellants differ from explosives in that propellants “explode comparatively slowly” while
“explosives are much more rapid in their action”. (Marshall 1920) Similarly, Van Gelder noted that gun cotton made in 1872 was “not suitable as a propelling charge in cannon or rifle” as it was “too brisant”. (Van Gelder and
Schlatter 1927)
The stability question of propellant caused serious concern to Government experts and powder companies (c. 1907) as large quantities of powder showing signs of decomposition were destroyed so as not to endanger magazines of battleships; large amounts of good powder were destroyed on the strength of shipboard tests made by poorly-trained gunners. (Van Gelder and Schlatter 1927)
5 The British, who were the Custodian Nation for STANAG 4170, modeled the first draft of that STANAG on ADA-
086259. The first draft, presented by the UK in September 1980, had a main body and four Annexes.
6 Guttmann, in his report to Congress, posed the question: “How can one tell whether an explosive is “safe”?”. His response to this question was that it “is a still more difficult one to answer”. (Guttmann 1909)
7 MIL-STD-1751A, which was preceded by MIL-STD-1751 (USAF) (DoD 1982), was canceled by DoD Notice of
Cancellation, MIL-STD-1751A Notice 1, dated 25 May 2005 and the content of MIL-STD-1751A was incorporated into the U.S. section of AOP-7. For easy reference, 10.7.16.6 in the U.S. section of AOP-7 provides a table with the old MIL-STD-1751A test numbers and the new corresponding AOP-7 test numbers.

Test
Impact
Standard
Sensitivity
Table 1 — Pass/Fail Criteria for Solid Gun Propellant Qualification
MIL-STD-1751A
(2001)
NATO AOP-7 U.S. Section
(2007)
Safety
Impact sensitivity shall be compared both to a
Type I or II, Class 5 RDX, and to a qualified propellant intended for a similar application.
Sensitivity no more than that of the reference comparison propellant.
The new gun propellant is compared to a
Type I or II, Class 5 RDX, and to a qualified gun propellant used in a similar application. No advisory criterion is provided.
Friction
Sensitivity
Electrostatic
Sensitivity
Friction sensitivity shall be compared both to a
Type I or II, Class 5 RDX, and to a qualified propellant intended for a similar application.
Sensitivity no more than that of the reference comparison propellant.
The candidate gun propellant is compared to a Type I or II, Class 5 RDX, and to a qualified gun propellant used in a similar application. No advisory criterion is provided.
Electrostatic sensitivity shall be compared both to a Type I or II, Class 5 RDX, and to a qualified propellant intended for a similar application. Sensitivity no more than that of the reference comparison propellant.
The candidate gun propellant is compared to a Type I or II, Class 5 RDX, and to a qualified gun propellant used in a similar application. No advisory criterion is provided.
Ignition
Temperature
Thermal
Stability
NR
≤ 2 ml gas/g propellant/40 hr @ 100°C
Aging Properties NR
Self-heating
Compatibility
Self-heating is assessed either experimentally or by calculation. Critical temperature and selfheating properties determined.
DTA, DSC, or VTS: ≤ 10°C ∆T of exotherm peak T @ < 10°C/min; propellant in 1:1 mixture w/ material being tested
Shock Sensitivity No criterion given
Critical Diameter No criterion given.
No advisory criterion is provided.
≤ 2 ml gas evolved /g HE/48 hr @ 100°C
An aging protocol shall be established.
Reasonable assurance that no unanticipated aging problems exist.
Technical assessment required.
NR
DTA or DSC: ≤ 10°C ∆T of exotherm peak T @ < 10°C/min; explosive in 1:1 mixture w/ material being tested
The shock sensitivity of the candidate gun propellant is compared to a qualified gun propellant used in a similar application.
No advisory criterion is provided.
No advisory criterion is provided. Can help in assessing the shock vulnerability of the granular bed.
Toxicity
Material Safety
Data Sheets
(MSDS)
Mandatory
Statute
Mandatory. Part of the qualification process.
Assessments of ingredients, combustion products & by-products of HE processing.
NR
Advisory
Assessments of ingredients, combustion products & by-products of gun propellant processing
Criteria: None; Info purposes only, assure safe handling & use
Not Required

Safety Tests: The safety tests for solid gun propellants qualification are discussed in the following section. It is noted that in MIL-STD-1751A, solid propellants are discussed, and unlike AOP-7, no distinction is made between solid gun propellants and solid rocket propellants.
Impact Sensitivity: What may have been the first mechanical apparatus, the Impact Machine, used for testing explosive materials was mentioned in 1906 (SIC 1906). Impact testing may have been done prior to this by Maj.
Beverly W. Dunn at the Frankford Arsenal c.1901, as he developed “a fairly satisfactory form of impact-testing machine” for testing explosive sensitiveness “in some form of laboratory apparatus before risking the destruction of a gun by firing them in projectiles”. (Van Gelder and Schlatter 1927) Eissler discussed a falling hammer or weight test for the ignition sensitivity of gun-cotton to determine the amount of gun-cotton that would detonate, based on different drop heights. (M. Eissler 1897) Before this, hand-held mallets were used. An impact machine (hammer drop) was installed at the Bureau of Mines for determining the sensitiveness of explosives to direct impact and minimizing the effects of irregularities in the explosive. (Hall and Howell 1913) Marshall noted that one of the most important physical properties of an explosive is its sensitiveness, which “affects not only its safety in handling and use, but also its suitability for various purposes”. (Marshall 1917b) MIL-STD-1751A gave the following rationale for conducting the impact test: “This test determines the sensitivity to a normal impact of explosives in powder and liquid form.” AOP-7 states that the purpose of the Ball Drop Impact Sensitivity test is to “determine the sensitivity to impact of primary explosives”. The pass/fail criteria in MIL-STD-1751A were that “data shall be compared both to a Type I or II, Class 5 RDX conforming to MIL-DTL-398, measured contemporaneously with the candidate explosive by one of the Group 1010 impact sensitivity test methods, and to a qualified propellant intended for a similar application.”.. Simply stated, impact sensitivity tests are required to determine the relative sensitivity of an explosive material to a material that is known to be acceptable for service use.
Class 5 RDX is very fine and very consistent from batch-to-batch, which allows it to be used for calibration of standardized testing machines. MIL-STD-1751A notes that Class 5 RDX is “the standard of comparison for booster and main charge explosives” and is “the reference standard material”.
The test setup and assembly for the laboratory scale impact test (Method 1011) described in MIL-STD-1751A is identical to the one described in Test Series 3a(i) for the United Nations classification of explosive substances for transportation and is an acceptable alternate test for hazard classification tests (DoD 1998).
Friction Sensitivity: Berthelot notes that when two different explosive substances are compared after decomposition at the same temperature, “their relative sensitiveness to shock and friction depends on the quantity of matter over which, from the first instant, the work of the shock or of the friction is distributed”. (Berthelot 1892) Eissler described a friction test for testing the “insensitiveness of friction” in which the explosive is rubbed between two sandpaper surfaces. (M. Eissler 1897) Marshall discussed several tests for friction sensitiveness, including striking the explosive with a hammer, a glancing blow from a broom-stick, rubbing the explosive in a mortar, and shooting at the explosive with a rifle (c. 1904). Marshall also noted the U.S. Bureau of Mines adopted a steel anvil and steel shoe apparatus for testing the sensitiveness of explosives to friction. (Marshall 1915) Brunswig noted that the mortar friction test could be made more sensitive by warming the mortar or adding sharp sand or similar substance to the explosive. (Brunswig 1912) A test for determining the sensitiveness of explosives to frictional impact (a glancing blow) was adopted by the Bureau of Mines to simulate ramming home explosive in a drill hole. (Hall and Howell
1913)
The rationale for conducting a sliding friction test was given in MIL-STD-1751A: “Friction sensitivity tests are conducted to determine relative safety in processing and to determine the sensitivity of a substance when subjected to a sliding frictional force”. STANAG 4170 and the associated STANAG 4487 (Explosive, Friction Sensitivity
Tests) mentioned no rationale. The purpose of the friction sensitivity test in AOP-7 is very similar in that it states
“this test is used to determine the sensitivity of a substance when subjected to a sliding frictional force”. The pass/fail criteria for the friction sensitivity test are identical for MIL-STD-1751A and AOP-7: Data shall be compared to
.
The Allegheny Ballistics Laboratory (ABL) Sliding Friction Test (Method 1021, MIL-STD-1751A) has been adopted by the UN as a standardized procedure used for the hazard classification of explosive substances. The

BAM 8 Friction Test (Method 1024, MIL-STD-1751A) has also been adopted by the UN as a standardized procedure for the hazard classification of explosive substances. The ABL Sliding Anvil Test is also an acceptable alternate test for hazard classification testing using the pass/fail criteria contained in Chapter 6 of TB 700-2 (DoD 1998).
Electrostatic Sensitivity: A more detailed rationale was given for electrostatic discharge in OD 44811 and MIL-
STD-1751A. In the mandatory requirements section for main charge explosives, OD 44811 stated, “Electrostatic sensitivity tests are made to ensure relative safety from the discharge of charged objects or bodies including humans”. The ABL report referenced in OD 44811 estimated an ungrounded person can deliver a maximum discharge of 0.001 joules (0.0003µF, 3000 V). Long before this however, Guttmann noted the great importance of a static electric charge in the manufacture of gunpowder, “since through neglecting to take proper precautions it is quite possible for dangerous fires and even explosions to occur.” (Guttmann 1895) Brunswig noted the propensity of nitrocellulose to collect static electricity and frequently cause accidents due to electrical static discharge.
(Brunswig 1912) Subsequently, Marshall noted the importance of dressing machinery drive belts in a gunpowder factory to make the belts “conduct and so prevents the accumulation of static charges of electricity”. (Marshall
1915) During this period there was an understanding that “explosives are easily electrified” from lightning or workers’ shoes, which “should be provided with a few copper studs in the sole, so as to “earth” the wearer”. (Barnett
1919) Sanford noted the importance of lightning conductors for explosives buildings as well as using wood, brass, and bronze in the construction of the buildings. (Sanford 1896) MIL-STD-1751A mentioned: “This test determines the energy threshold required to ignite explosives by electrostatic stimuli of varying intensities. Material response data obtained can then be used to characterize the probability of initiation due to electrostatic discharge events.”
STANAG 4490 9 states:
“Most of ESD (electrostatic discharge) tests used at this time are "spark tests" that use small quantities of material and simulate the discharge through such material by charged humans or metallic pieces.”
MIL-STD-1751A required and AOP-7 requires that the test data be compared both to a Type I or II, Class1 or Class
5 RDX conforming to MIL-DTL-398, and to a qualified gun propellant used in a similar application .
Ignition Temperature: Ignition temperature was not required for MIL-STD-1751A. Ignition temperature is a mandatory requirement in AOP-7, but no advisory criterion is provided. The ignition temperature is measured using
Differential Thermal Analysis (DTA), Differential Scanning Calorimetry (DSC), or STANAG 4491 tests.
AOP-7 states that the purpose of the Thermal Stability (DTA) test is to “evaluate the behavior of energetic materials when subjected to a temperature rise”. The DTA test records the difference in temperature between a substance and a thermally inert reference material when both are subjected to the same thermal conditions. The Thermal Stability
(DSC) test measures the heat flow to or from a sample as it undergoes transitions in a thermally controlled environment. (NATO 2007)
Thermal Stability: The Abel heat test was first introduced by Sir Frederick Abel in 1866 as a test for the stability of gun cotton. (Abel 1866) It was introduced as a response to various gun cotton factory accidents. In 1914 it became a requirement that all nitro compound explosives satisfied the conditions of the Abel heat test, and now it is seen as a purity test to be used at the beginning of propellant life and not an extent-of-aging indicator. (Sharp 2012) Walke, in his lectures to the U.S. Artillery School in Fort Monroe, Virginia, reported that the stability or heat test was “applied during the process of manufacture”. Walke further noted that the stability test for explosives was “precisely the same”, with a few modifications, as used for gun-cotton. (Walke 1891) Berthelot describes the heat stability as being composed of two parts, very slow progressive heating to determine partial evaporation of components, and more rapid heating to ascertain at what temperature the explosion takes place, or progressive decomposition at a lower temperature. (Berthelot 1892) Guttmann discussed the importance of stability in explosives, and that various
8 The BAM (Bundesanstalt fur Materialprufung) small friction tester, manufactured by the Julius Peters Company of
Berlin, Germany, is used to measure the response of energetic materials to a friction stimulus generated between two roughened porcelain surfaces. (NATO 2007)
9 STANAG 4490 (Explosives, Electrostatic Discharge Sensitivity Test(s)) is a related document referenced in
STANAG 4170 Edition 2 (NATO 2008).

stability tests had been proposed, but none was a true measure of stability. (Guttmann 1909) Marshall reported that several investigators, during the 1903-1912 timeframe, devised sensitivity tests in which the explosive is heated in a vacuum and the evolution of the gas was measured, generally by means of a manometer. (Marshall 1915) Marshall reported that Lunge and Bebie conducted stability testing on nitrocellulose, but the tests were unsatisfactory because the products had not been stabilized sufficiently. (Marshall 1917a) In tests using an evacuated, airtight glass balloon conducted over many months, Frederick Abel apparently showed “that very pure nitrocellulose withstood to a remarkable degree the decomposing influence of long-continued heating, even at temperatures of almost 100C”.
(Brunswig 1912) Barnett noted that the Abel Heat Test determined the relative rate of acid production and “in spite of its numerous imperfections gives a fair idea of stability”. (Barnett 1919) Although the Abel Heat Test was the most common test for determining explosive stability, other tests were also used. There were the Guttmann, Spica and Moir (very sensitive) trace tests, the very crude Vieille test adopted in France, the Waltham Abbey Silvered
Vessel Test, and the Will quantitative test. (Barnett 1919) Rationale was found for vacuum thermal stability in
MIL-STD-1751A and STANAG 4491 10 . Both references identified this test to measure the stability of an explosive at an elevated temperature under vacuum and to support a determination of how the explosive reacts to elevated temperatures over a period of time. No other rationale or elaboration was noted. MIL-STD-1751A had an advisory criterion to be acceptable as a propellant: the Vacuum Thermal Stability (VTS) 11 or Modified VTS (MVTS) value must not be larger than 2.0 ml gas evolved/gram of propellant/40 hours at 100°C. The NATO AOP-7 document has this threshold as a mandatory requirement, and is identical with the exception of the duration, which is 48 hours.
AOP-7 also allows STANAG 4556 tests.
For stability testing of nitrocellulose propellants, AOP-7 (NATO 2008a) allows each NATO Partnership for Peace
(PfP) nation to use their national test procedures rather than the NATO STANAG test procedures, if the national tests are listed in AOP-7. Some of these, such as the Abel Heat Test are very old (c. 1865) 12 (Schlatter 1921). The
Government Heat Test, or heat test for determining stability of explosives, was defined by order by the Explosives
Act of 1875. (Sanford 1896) This may have been the first detailed and documented test required to test the stability of explosives. Others, such as the Methyl Violet Tests (Meyer, Kohler and Homburg 2002), the Dutch Mass Loss
Test, and the Bergmann Junk Test 13 (Worden 1911) are more recent, but still at least 50 years old. (Vogelsanger
2011)
A need to have a single heat test for all countries was identified as early as 1919. Barnett noted that the heat test has been adopted by most countries as the standard method for measuring stability, and postulated that “it would be a great convenience if an international method of carrying out the (heat) test could be established and adopted by all countries”. (Barnett 1919)
Thermal Stability (Method 1061 and 1063, MIL-STD-1751A) is an acceptable alternate test procedure for hazard classification testing using the pass/fail criteria contained in Chapter 5 of TB 700-2.
Aging: As explosives age they undergo chemical decomposition. Desired mechanical properties degrade, ingredients and decomposition products become sensitive to a point where they are unfit for service use. Nitrate esters require a high level of surveillance compared to other explosives because of stabilizer depletion, which results in self-heating and eventually autoignition. Guttmann provided a definition of stability: “it must neither volatilize, nor alter mechanically or chemically when kept”. (Guttmann 1895) Weaver suggested that for an explosive to be considered for military use it had to “prove itself to be a thoroughly stable mixture when stored for long periods of
10 STANAG 4491 (Explosives, Thermal Sensitiveness and Explosiveness Tests) is a related document referenced in
STANAG 4170 Edition 2.
11 The VTS test was developed by Dr. Russell McGill at the Explosives Research Laboratory (ERL), Bruceton, PA to measure the chemical stability of explosives like PETN and RDX. (Noyes 1948)
12 A detailed description of the Abel Heat Test is described in Appendix B of A Handbook on Modern Explosives .
(M. Eissler 1897)
13 Marshall noted that in 1907 “Prussian military authorities and the German Railway Commission adopted a test devised by Bergmann and Junk”. (Marshall 1915)

time under the conditions to be found in ordinary service and storage magazines”. (Weaver 1906) Marshall noted that an important property of an explosive is its stability, such that it “should retain its properties and composition unchanged when stored even for a long period”. (Marshall 1917a) Marshall further noted that true stability “can only be ascertained by storage trials under various conditions extending over months or years”. (Marshall 1915) Barnett also noted that stability was very important for long term storage of military powders (propellants) before use, and that “the most stable powders are usually those which are least porus [sic], as porosity frequently leads to instability through oxidation”. (Barnett 1919) A sample of British MD cordite (British double-base prior to World War II) has been found to be of apparently unchanged stability after 30 years of temperature-climate storage (c. 1939). (DoA
1990)
Prior to the adoption of stabilizers in propellants, a surveillance test was proposed (c.1907), and later adopted by the
Navy in which a few ounces of propellant were exposed to 150°F temperatures in a sealed glass bottle. In 1908, diphenylamine stabilizer was added to military powders, which resulted in a much longer storage life. Although adopted in the U.S. in 1908, the use of diphenylamine as a stabilizer was mentioned in 1890 for Alfred Nobel’s smokeless powder. (Van Gelder and Schlatter 1927)
MIL-STD-1751A left the aging requirement up to the service qualification authority as deemed appropriate, and provided no detailed procedures.
AOP-7 states: “It is very important to determine whether the safety and performance characteristics of an explosive will change during its life cycle.” AOP-7 requires that data acquired following accelerated aging shall be provided to determine whether the explosive characteristics of the original material have changed due to aging. Any change that could affect safety and reliable performance is of particular concern. An aging protocol shall be established, and aging studies should continue “until there is reasonable assurance that no unanticipated aging problems exist”. A technical assessment of the test results is required to determine the extent impact on safety and performance. If the explosive is qualified for joint military use, the aging protocol must be approved and coordinated among the
Services. (NATO 2008a)
Self-heating: MIL-STD-1751A called for self-heating to be assessed either experimentally or by calculation. The critical temperature could be estimated using the thermal stability test, which is used for determination of critical temperature and self-heating properties associated with a given energetic material or propellant. AOP-7 does not have a self-heating requirement for solid gun propellants.
Rationale for the critical temperature and self-heating properties was provided in MIL-STD-1751A: “When an energetic material is slowly subjected to an elevated temperature for a prolonged period of time, the material may undergo the phenomenon of self-heating. In this process, thermal energy is liberated in the interior of the explosive as a result of slow chemical decomposition. At some point, a state of equilibrium exists at which the energy released by the thermal decomposition process is equal to the energy dissipated by the system. If the thermal energy is released at a faster rate than it is dissipated, the temperature of the explosive will increase until a catastrophic event occurs. This event, generally referred to as slow cookoff, is associated with the material’s critical temperature. The critical temperature is defined as the lowest constant surface temperature above which a given energetic material of a specific size and shape will catastrophically self-heat. Critical temperature is a heat balance between heat generated and heat lost for a given mass and geometry of an explosive or propellant.”
Compatibility: Compatibility was mandatory for MIL-STD-1751A and is mandatory for AOP-7. As for rationale,
MIL-STD-1751A stated “The interaction of the candidate explosive with common materials (e.g. metals, adhesives, acids, bases) with which it may come into contact shall be assessed.” No mandatory pass/fail criteria were identified, but (advisory) guidance was given in MIL-STD-1751A and is provided in AOP-7 that when using DTA or
Differential Scanning Calorimetry (DSC) procedures, a change of no more than 10°C in the exotherm peak temperature, measured at a heating rate of 10°C/minute or less. The AOP-7 rationale offers that data acquired in accordance with STANAG 4147 is to determine the compatibility of the propellant with materials used in its manufacture or in its intended application. (NATO 2008a)

Shock Sensitivity: MIL-STD-1751A called for the shock sensitivity to be assessed using the Naval Ordnance
Laboratory (NOL) Large Scale Gap Test (LSGT) 14 , the NOL Small Scale Gap Test (SSGT), the Expanded Large
Scale Gap Test (ELSGT), the Super Large Scale Gap Test (SLSGT), the Insensitive High Explosive (IHE) Gap Test, or the Wedge Test. There were no pass/fail test criteria provided.
In AOP-7, shock sensitivity is a mandatory requirement for gun propellants. The shock sensitivity of the candidate gun propellant is compared to a qualified gun propellant used in a similar application. No advisory criterion is provided. Normally the NOL LSGT or an appropriate STANAG 4488 shock sensitivity test is used.
The purpose of shock sensitivity testing is to
SSGT,
Intermediate Scale Gap Test, ELSGT, and SLSGT are conducted to provide
a measure of the shock required to initiate and propagate a high order detonation in the explosive being tested”. MIL-STD-1751A states that the LSGT
“has been used extensively for over thirty years to characterize the shock sensitivity of energetic compounds, and to some extent, it is considered the “baseline” from which most other shock sensitivity tests have been developed”. In
1961, the SSGT was redesigned to use an RDX donor and polymethylmethacrylate (PMMA) attenuator, which corrected several test deficiencies. (DoD 2001) The IHE gap test was developed to provide a means for measuring the shock sensitivity of insensitive high explosives. The technical objective was to develop a procedure that subjects the test explosive to stresses of 15-80 kbar with a pulse width of several microseconds. (DoD 2001)The purpose of the wedge test is to determine the shock initiation characteristics of an energetic material. The objective of the wedge test is to determine the run to detonation point at which the detonation wave overtakes the shock wave. (DoD
2001)
The NOL LSGT (MIL-STD-1751A) is an acceptable alternate test for the gap test for solids and liquids (UN hazard classification Test 2(a) (iii)). Additionally, the U.S. Army Armament Research, Development and Engineering
Center (ARDEC) Solid Propellant Shock Initiation Sensitivity Test is an acceptable alternate test for solid gun propellants. And finally, the ELSGT test described in MIL-STD-1751A is an acceptable alternate test procedure for
Extremely Insensitive Detonating Substance (EIDS) hazard classification Test 7(b) of TB 700-2. (DoD 1998)
Critical Diameter: The critical diameter defines the threshold for propagation of steady-state detonation. MIL-STD-
1751A notes that this test measures the failure threshold, which means it is far more easily affected by small variations in the physical properties of the charge. Additionally, there is no well-defined test for critical diameter that is applicable to all explosives at all diameters; other techniques may be used to characterize and define the critical diameter. (DoD 2001)
Critical diameter was in the list of mandatory data and appropriate tests for propellants in MIL-STD-1751A. The critical diameter assessment used either the critical diameter test or the very small critical diameter test. There were no pass/fail test criteria provided.
In AOP-7, the critical diameter performance assessment test is used to find the smallest diameter that can support a steady state detonation. This information can help in assessing the shock vulnerability of the granular bed. AOP-7 provides no advisory criterion.
Statute Requirements: Statute requirements are mandated as a result of government laws or regulations. This information allows for the safe handling of the explosive and/or ingredients during production and use in order to assure personnel safety. Data are provided for informational purposes.
The Explosives Act of 1875 in Great Britain may have been the first attempt to regulate the “manufacturing, keeping, selling, carrying, and importing” explosive substances. In the U.S., public safety came to the fore as early as World War I when the U.S. Congress passed the Explosives Regulation Act that made it unlawful to
“manufacture, distribute, store, or use” explosives in a manner “detrimental to the public safety”. (Manning 1919)
14 NOL developed the LSGT to measure the shock sensitivity of solid rocket propellants and the LSGT was essentially a modification of the test developed by Eyster, Smith, and Walton c.1949. (R. L. Beauregard 2005)

Toxicity Evaluation: The Toxic Substances Control Act of 1976 provides EPA with authority to require reporting, record-keeping and testing requirements, and restrictions relating to chemical substances and/or mixtures. (USC
1976) There seemed to be some precedence for this Act. For example, as noted in the chapter on Explosives and
Propellants, in the United States during World War I, there were at least 17,000 cases of TNT poisoning, resulting in more than 475 deaths. (Deeter and Gaydos 1993) About this same time, Marshall noted that under certain conditions, some of the products formed by explosives are poisonous, such as carbon monoxide and oxides of nitrogen. (Marshall 1917b) MIL-STD-1751A required that an evaluation of the toxicity of an explosive must be performed as part of the general qualification requirements. This included assessments of the ingredients, combustion products, and by-products of the processing of the explosive. Support in the evaluation of toxicity was available from the Operational Toxicology Branch of the Air Force Research Laboratory Deployment and
Sustainment Division, at Wright Patterson AFB.
STANAG 4170 requires that an evaluation of the toxicity must be performed. In the U.S. section of AOP-7 this includes an assessment of the ingredients, combustion products and by-products of the processing of the explosive.
Support of the evaluation is available from the Operational Toxicology Branch, Air Force Research Laboratory
Deployment and Sustainment Division, Wright Patterson AFB, Dayton, Ohio.
Material Safety Data Sheet (MSDS): MSDS requirements did not come into being until the early 1980s, and therefore did not appear in MIL-STD-1751A. In the U.S. section of AOP-7, it is mandatory but for information purposes only that MSDS be available to assure the safe handling and use of material, and shall be prepared in the early stages of the development of the explosive material.
In the U.S., OSHA issued its final regulations in Rules and Regulations of the Federal Register, Volume 48, Number
228, on November 25, 1983. Under this ruling, MSDSs (either an improved form Number 20 or some similar format) were required for all shipments of hazardous chemicals leaving the manufacturers work place and from all importers of such on all shipments by November, 1985. In the U.S., the Occupational Safety and Health
Administration requires that MSDSs be available to employees for potentially harmful substances handled in the workplace under the Hazard Communication regulation. The MSDS is also required to be made available to local fire departments and local and state emergency planning officials under Section 311 of the Emergency Planning and
Community Right-to-Know Act. The American Chemical Society defines Chemical Abstracts Service Registry
Numbers (CAS numbers), which provide a unique number for each chemical, and are also used internationally in
MSDSs.
Qualification Tests for Solid Rocket Propellants
The U.S. DoD first defined Qualification requirements for explosive materials in NAVORD OD 44811 and ADA-
086259, which was the tri-service version. This was to assure that the materials approved were safe and suitable for production and could be considered for service use in the roles identified. The roles identified were primary, booster and main charge explosives. Propellants and pyrotechnics were not covered in the OD or the AD. These documents contained advisory and mandatory pass/fail criteria for selected tests.
The focus of this section will be the rationale for mandatory qualification tests and pass/fail criteria (Table 2) for solid rocket propellants as identified in MIL-STD-1751A (DoD 2001), STANAG 4170 (NATO 2008), and AOP-7
(NATO 2007).

Test
Impact
Sensitivity
Friction
Standard
Sensitivity
Table 2 — Pass/Fail Criteria for Solid Rocket Propellant Qualification
MIL-STD-1751A
(2001)
NATO AOP-7 U.S. Section
(2007)
Safety
Impact sensitivity shall be compared both to a
Type I or II, Class 5 RDX, and to a qualified propellant intended for a similar application.
Sensitivity no more than that of the reference comparison propellant.
Friction sensitivity shall be compared both to a
Type I or II, Class 5 RDX, and to a qualified propellant intended for a similar application.
Sensitivity no more than that of the reference comparison propellant.
The data are compared to normal. The candidate rocket propellant is compared to a Type I or II, Class 5 RDX, and to a qualified rocket propellant used in a similar application. No advisory criterion is provided.
The candidate rocket propellant is compared to a Type I or II, Class 5 RDX, and to a qualified gun propellant used in a similar application. No advisory criterion is provided.
Electrostatic
Sensitivity
Electrostatic sensitivity shall be compared both to a Type I or II, Class 5 RDX, and to a qualified propellant intended for a similar application. Sensitivity no more than that of the reference comparison propellant.
The candidate rocket propellant is compared to a Type I or II, Class 5 RDX, and to a qualified propellant used in a similar application. No advisory criterion is provided.
Ignition
Temperature
NR
Thermal
Stability
≤ 2 ml gas/g propellant/40 hr @ 100°C
Aging Properties NR
No advisory criterion is provided.
≤ 2 ml gas evolved /g HE/48 hr @ 100°C
Self-heating
Compatibility
Self-heating is assessed either experimentally or by calculation. Critical temperature and selfheating properties determined.
DTA, DSC, or VTS: ≤ 10°C ∆T of exotherm peak T @ < 10°C/min; propellant in 1:1 mixture w/ material being tested
Shock Sensitivity No criterion given
Critical Diameter No criterion given.
An aging protocol shall be established.
Reasonable assurance that no unanticipated aging problems exist.
Technical assessment required.
Self-heating is assessed either experimentally or by calculation. DTA,
DSC or TGA tests are used.
DTA or DSC: ≤ 10°C ∆T of exotherm peak T @ < 10°C/min; explosive in 1:1 mixture w/ material being tested
The shock sensitivity of the candidate rocket propellant is compared to a qualified propellant used in a similar role.
No advisory criterion is provided.
No advisory criterion is provided.
Assessed if propellant is shown to detonate in the shock sensitivity test.
Statute
Toxicity
Material Safety
Data Sheets
(MSDS)
Mandatory
Mandatory. Part of the qualification process.
Assessments of ingredients, combustion products & by-products of HE processing.
NR
Advisory
Assessments of ingredients, combustion products & by-products of propellant processing
Criteria: None; Info purposes only, assure safe handling & use
Not Required

Safety Tests: The safety tests for solid rocket propellants qualification are discussed in the following section. Note that in MIL-STD-1751A, solid propellants are discussed, and unlike AOP-7, no distinction is made between solid gun propellants and solid rocket propellants.
The requirements for solid rocket propellants are very similar to those for solid gun propellants. In instances where the discussion for solid rocket propellants would be repetitive to that of solid gun propellants, the reader will be referred back to the appropriate section for solid gun propellants.
Impact Sensitivity: The possible origin of the impact testing was described previously in the section on solid gun propellants. A 1994 letter by RADM Rempt noted significant progress in IMAD explosives, but major sensitivity problems still existed with large rocket motors. (R. L. Beauregard 2005)
Fisher noted that replacing the hydroxy terminated polybutadiene (HTPB) polymer traditionally used in ammonium perchlorate (AP) filled composite propellants, with an hydroxyl-terminated polyether- (HTPE) based polymer “was primarily the result of other changes in the propellant ingredients to reduce the propellant sensitivity”, as AP was sensitive to impact, but not shock. (Fisher, Powell and Watt 2005)
Friction Sensitivity: The rational for friction sensitivity was discussed previously in the solid gun propellants section. In AOP-7 the candidate rocket propellant is compared to a Type I or II, Class 5 RDX conforming to MIL-
DTL-398, and, if possible, to a qualified rocket propellant used in a similar application. No advisory criterion is provided; however, the sensitivity of the candidate material should compare favorably with that of a Comparison
Explosive.
Electrostatic Sensitivity: The discussion for electrostatic sensitivity in the solid gun propellants section applies to solid rocket propellants as well. A slight difference exists in AOP-7: The propellant is compared to a Type I or II,
Class 5 RDX conforming to MIL-DTL-398, measured contemporaneously with the candidate material, and, if possible, to a qualified propellant used in a similar application. No advisory criterion is provided; however, the sensitivity of the test material should compare favorably with that of a Comparison Explosive.
Ignition Temperature: The discussion for ignition temperature in the solid gun propellants section also applies to solid rocket propellants.
Thermal Stability: The discussion for thermal stability in the solid gun propellants section applies to solid rocket propellants also.
Aging Properties: The rationale for aging properties was discussed previously in the solid gun propellants section.
The U.S. Army experienced early on the deterioration of rockets during long-term storage: Following a Mexican battle in 1847, the U.S. Army “rocketeer battalion was disbanded and the remaining rockets were placed in storage.
They remained in mothballs for about 13 years -- until 1861 when they were hauled out for use in the Civil War. The rockets were found to have deteriorated”. (NASA n.d.)
Self-heating: The rationale for self-heating was discussed in the solid gun propellants section.
MIL-STD-1751A called for self-heating to be assessed either experimentally or by calculation. The critical temperature could be estimated using the thermal stability test, which is used for determination of critical temperature and self-heating properties associated with a given energetic material or propellant. Thermal stability is a mandatory test in AOP-7 in which the advisory criterion is that there should be no more than 2 ml gas evolved per gram of propellant per 48 hours at 100°C using the VTS, Modified VTS or STANAG 4556 tests.
Compatibility: The rationale for compatibility is identical to that discussed in the section for solid gun propellants.
Shock Sensitivity: The discussion for shock sensitivity in the solid gun propellants section also applies to solid rocket propellants.
The NOL LSGT was found to be inadequate for shock sensitivity testing of large rocket motors. Beauregard noted that in 1958, “Navy scientists questioned the validity of extrapolating the data from the NOL LSGT to support the

shock sensitivity assessments being made for large composite rocket propellants”, hence a test much larger than the
NOL LSGT, called the BEAUREGARD test, was configured to perform large-scale shock sensitivity tests on the
Polaris rocket motor. (R. L. Beauregard 2005)
The SLSGT (Method 1044) described in MIL-STD-1751A is an acceptable alternate test procedure for the large rocket motor hazard classification SLSGT described in Chapter 6 of TB 700-2. (DoD 1998) The SLSGT, with certain instrumentation modifications, “when applied to a solid propellant, and using the pass/fail criterion provided in TB 700-2, may serve to demonstrate that a large rocket motor qualifies for assignment to hazard division 1.3.
(NATO 2007)
Critical Diameter: Critical diameter was in the list of mandatory data and appropriate tests for propellants in MIL-
STD-1751A. The critical diameter assessment used either the critical diameter test or the very small critical diameter test. There were no pass/fail test criteria provided. In AOP-7 the critical diameter of the candidate rocket propellant is assessed if it is shown to detonate in the shock sensitivity test. Data from critical diameter performance assessment are used to find the smallest diameter that can support a steady state detonation.
Statute Requirements: Statute requirements are mandated as a result of government laws or regulations. This information allows for the safe handling of the explosive and/or ingredients during production and use in order to assure personnel safety. Data are provided for informational purposes.
Toxicity: The rationale for toxicity in the solid gun propellants section also applies to solid rocket propellants.
Material Safety Data Sheet (MSDS): The rationale for MSDS in the solid gun propellants section applies to solid rocket propellants also.
Qualification Tests for Liquid Propellants
The U.S. DoD first defined Qualification requirements for explosive materials in NAVORD OD 44811 and ADA-
086259, which was the tri-service version. This was to assure that the materials approved were safe and suitable for production and could be considered for service use in the roles identified. The roles identified were primary, booster and main charge explosives. Propellants and pyrotechnics were not covered in the OD or the AD. These documents contained advisory and mandatory pass/fail criteria for selected tests.
The focus of this section will be the rationale for mandatory qualification tests and pass/fail criteria (Table 3) for liquid propellants as identified in MIL-STD-1751A (DoD 2001), STANAG 4170 (NATO 2008), and AOP-7
(NATO 2007).
Safety Tests: The safety tests for liquid propellant qualification are discussed in the following section. For the mandatory data and appropriate tests for liquid propellants in MIL-STD-1751A, no pass/fail criteria were assigned and no advisory criteria were provided; data from the tests were required to evaluate the overall safety characteristics of the liquid propellants.
Impact Sensitivity: Impact sensitivity tests are required to determine the relative sensitivity of an explosive material to a material that is known to be acceptable for service use.
In MIL-STD-1751A, the impact sensitivity of the candidate liquid propellant was compared to that of n-propyl nitrate, using one of the impact sensitivity test methods listed in MIL-STD-1751A that can be used with liquids. In
AOP-7 the candidate liquid propellant impact sensitivity is compared to that of n-propylnitrate using the liquid explosive (JANNAF Method) impact sensitivity test or the appropriate NATO STANAG 4489 test. No advisory criterion is provided.
The liquid monopropellant, n-propyl nitrate, is used in ASTM D2540 as a reference test liquid. The ASTM E50
(defined as the 50% ignition condition) value for n-propyl nitrate is 8.4 kg-cm. (ASTM 1982)

Table 3 — Pass/Fail Criteria for Liquid Propellant Qualification
Test
Impact
Sensitivity
Friction
Standard
Sensitivity
MIL-STD-1751A
(2001)
Safety
The impact sensitivity shall be compared to that of n-propyl nitrate, using a test method that can be used with liquids.
NATO AOP-7 U.S. Section
(2007)
The friction sensitivity shall be compared to that of n-propyl nitrate, using a test method that can be used with liquids.
The impact sensitivity of the candidate liquid propellant is compared to that of npropylnitrate. No advisory criterion is provided.
The friction sensitivity of the candidate propellant is compared to that of npropylnitrate. No advisory criterion is provided.
Electrostatic
Sensitivity
The electrostatic sensitivity shall be compared to that of n-propyl nitrate, using a test method that can be used with liquids.
The electrostatic sensitivity of the candidate propellant is compared to that of n-propylnitrate. No advisory criterion is provided.
NR Thermal
Stability
Self-heating
No criteria given
Compatibility
Aging Properties
No criteria given
No criteria given
NR
NR
DTA or DSC: ≤ 10°C ∆T of exotherm peak T @ < 10°C/min; HE in 1:1 mixture w/ material being tested
An aging protocol shall be established.
Reasonable assurance that no unanticipated aging problems exist.
Technical assessment required.
Shock Sensitivity
Freezing Point
Flash Point
Minimum
Pressure for
Vapor Ignition
No criteria given The shock sensitivity is assessed. No advisory criterion is provided.
Any scientifically acceptable method can NR
For Informational purposes. No criteria given. The test is performed and the results are reported for information purposes. No advisory criterion is provided.
No criteria given. be used. No advisory criterion is provided.
The test is performed and the results are reported for information purposes. No advisory criterion is provided.
Toxicity
Material Safety
Data Sheets
(MSDS)
Mandatory
Statute
Mandatory. Part of the qualification process.
Assessments of ingredients, combustion products & by-products of HE processing.
NR
Advisory
Assessments of ingredients, combustion products & by-products of HE processing
Criteria: None; Info purposes only, assure safe handling & use
Not Required

Friction Sensitivity: The rationale for friction sensitivity is discussed in the solid gun propellant section.
In MIL-STD-1751A, the friction sensitivity of the candidate liquid propellant was compared to that of n-propyl nitrate, using one of the friction sensitivity test methods for liquid propellants listed in MIL-STD-1751A. In AOP-7 the candidate liquid propellant friction sensitivity is compared to that of n-propylnitrate using the ABL Sliding
Friction Test or the appropriate NATO STANAG 4487 test. No advisory criterion is provided.
Electrostatic Sensitivity: The rationale for electrostatic sensitivity is discussed in the solid gun propellant section.
In MIL-STD-1751A, the electrostatic sensitivity of the candidate liquid propellant was compared to that of n-propyl nitrate, using one of the electrostatic discharge sensitivity test methods for liquid propellants listed in MIL-STD-
1751A. In AOP-7 the candidate liquid propellant electrostatic sensitivity is compared to that of n-propylnitrate using the Electrostatic Discharge test and one of the following methods: ARDEC (Picatinny Arsenal), Naval Air Warfare
Center (NAWC), or the Naval Surface Warfare Center (NSWC); an equivalent test may also be used. No advisory criterion is provided.
Thermal Stability: The rationale for thermal stability is discussed in the solid gun propellant section.
For MIL-STD-1751A, no criterion was provided. Thermal stability is not a requirement in AOP-7.
Self-heating: For MIL-STD-1751A, no criterion was provided. Self-heating is not a requirement in AOP-7.
Compatibility: The rationale for compatibility is discussed in the solid gun propellant section.
For MIL-STD-1751A, no criterion was provided. In AOP-7, the results for the liquid propellant in a 1:1 mixture with the material being tested are compared with the results for the candidate propellant alone. The guidance in
AOP-7 provides that when using DTA or DSC procedures, a change of no more than 10°C in the exotherm peak temperature can occur, measured at a heating rate of 10°C/minute or less.
Aging Properties: The rationale for aging properties was discussed previously in the solid gun propellants section.
Shock Sensitivity: In MIL-STD-1751A, the shock sensitivity was assessed using one of the explosive shock sensitivity tests – NOL LSGT, NOL SSGT, ELSGT, SLSGT, IHE Gap Test, or the wedge test. No criteria were provided. In AOP-7 the shock sensitivity is assessed, but is not mandatory. AOP-7 states that “tests such as NOL
LSGT, IHE Gap Test or STANAG 4488 tests can be modified to accommodate liquids. No advisory criterion is provided.
Freezing Point: No test for freezing point was listed in MIL-STD-1751A. Freezing point is a mandatory test in AOP-
7 in which “any scientifically acceptable method can be used”. No advisory criterion is provided in AOP-7.
Additionally, for freezing or melting point, information in accordance with UN or national procedure shall be provided (NATO 2008a).
Flash Point: From MIL-STD-1751A, the purpose of the flash point test is to “measure the temperature where the sample will emit vapors that may be ignited by an open flame”. In MIL-STD-1751A, flash point testing was conducted for information purposes. There was no advisory criterion when using the ignition test to determine the flash point for liquid explosives. In MIL-STD-1751A, the ignition test was used for hazard classification in storage, shipping, and operational conditions. MIL-STD-1751A allowed for the use of the Thermogravimetric Analysis
(TGA) for thermal stability testing of liquid propellants of low volatility. The TGA, which measures the change in weight of a test sample as a function of temperature and time, can be useful in distinguishing between phase changes
(e.g., melting) and weight changes resulting from chemical reactions. In AOP-7 the flash point test is performed and the results are reported for information purposes. No advisory criterion is provided. The test normally used is the flash point test for liquid propellants; the thermal stability TGA test may be used for liquid propellants with low volatility. No advisory criterion is provided in AOP-7.
Minimum Pressure for Vapor Ignition: In MIL-STD-1751A, a sensitivity test is conducted to determine the minimum pressure for vapor phase ignition for liquid propellants. This test determines the pressure below the point where it is impossible to ignite a monopropellant vapor or fuel vapor-air mixture by using a fixed quantity of energy applied in a well-defined manner. However, no advisory criterion was provided. In AOP-7, the test is performed and

the results are reported for information purposes. The minimum pressure for vapor phase ignition is verified using the sensitivity test for liquid propellants. No advisory criterion is provided.
Statute Requirements: Statute requirements are mandated as a result of government laws or regulations. This information allows for the safe handling of the explosive and/or ingredients during production and use in order to assure personnel safety. Data are provided for informational purposes.
Toxicity: The rationale for toxicity in the solid gun propellants section also applies to solid rocket propellants.
Material Safety Data Sheet (MSDS): The rationale for MSDS in the solid gun propellants section applies to solid rocket propellants also.
Observations and Conclusions
This paper is the result of a review of many historical documents, and interviews with members of the energetic materials community who were instrumental in developing the requirements for Qualification. In general, the sensitivity tests developed over the years were in response to incidents or accidents with explosive materials, and were designed to gather information that would alleviate the problem in the future. A literature search of pre-World
War I and II documents (see References) demonstrated that friction, impact, heat, shock and electrostatic discharge were known to create hazards to personnel and equipment, and efforts were made to evaluate and eliminate materials that were too sensitive to these stimuli.
This paper has been broadened in the area of energetic materials testing to include an international perspective
(Great Britain, Germany, and France) going back to the 19 th century. In particular these tests relate to impact, friction, and electrostatic sensitivity, thermal or heat stability, and aging.
This paper is an effort to answer some of the questions often raised as to the origin and applicability of tests, and pass/fail criteria required by the military services. We found that prior to World War I, sensitivity tests were devised to evaluate the means to identify and minimize the hazards in the manufacture, transportation, storage and use of explosive materials. Many of the pass/fail criteria were based on historical information and data evaluated by experienced explosive materials professionals in an effort to establish a baseline to evaluate, by comparison, new materials, to materials that have been shown to be safe and suitable for use in specific applications.
An oral historical documentation, canvassing the IM community and technical experts to compile their thoughts and recollection of requirements and pass/fail criteria, should be given serious consideration for future work.
The qualification of solid and liquid propellants has evolved from a series of defined tests in MIL-STD-1751A to a well-developed list in AOP-7. These qualification tests will continue to evolve as they are synchronized with NATO
STANAGs and harmonized with DDESB, NATO, and the UN. The qualification tests discussed in this paper, which were designed and developed by experienced explosive materials professionals, were structured to provide sufficient data for which an explosive qualification decision could be made.
It is strongly recommended that during subsequent revisions to NATO test STANAGs, a conscious effort be made to include a section addressing the technical purpose for conducting a test, and a technical rationale for establishing rigid or advisory pass/fail criteria. The U.S. canceled MIL-STD-1751A in May 2005, replacing it in the acquisition community with AOP-7, thus moving closer to linking procurement of munitions to agreed-to NATO standards.
The authors are enthusiastic that this review will stimulate active participation and debate in discussions in the review of test rationale and pass/fail criteria identified in current and future Qualification requirements documents.
Readers of this paper who have additional knowledge, information, or insight into the requirements and pass/fail criteria described in this paper are asked to contact NOSSA (Mr. Ken Tomasello).

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Biography
K. Tomasello, Navy Insensitive Munitions Office, 3817 Strauss Ave, Indian Head, MD, 20640, USA, telephone –
(301) 744-6078, facsimile – 301-744-6046, e-mail – ken.tomasello@navy.mil
.
Mr. Tomasello is experienced in conventional Ordnance R&D and manufacturing for the U.S. Navy, was head of the
Detonation Science and Chemistry Division at NSWC Indian Head, and currently is the program manager for the
IMAD program at Naval Ordnance Safety and Security Activity. He holds a BS in Chemical Engineering from the
University of Maryland.
M. Sharp, MSIAC/NATO, Avenue Leopold III, B-1110 Brussels, Brussels, Belgium, telephone – 32 2 707 5558, facsimile – 32 2 707 5363,email – m.sharp@msiac.nato.int
.
Dr. Sharp currently is a specialist in munition systems at MSIAC. He previously worked for the UK MOD in the fields of munition vulnerability, Insensitive Munitions, whole life assessment, hazard classification and safety policy.
J. Adams, Booz Allen Hamilton, 1550 Crystal Drive, Arlington, VA, 22202-4158, telephone – (703) 412-7762, facsimile – 703-412-7525, email – adams_john@bah.com
Mr. Adams is experienced in analysis and hydrocode modeling of munitions and explosive to IM threats. He currently provides engineering support for system safety and IM programs. He holds a Mechanical Engineering degree from the University of Dayton.