NEXT GENERATION 

FIRE SUPPRESSION TECHNOLOGY 

PROGRAM STRATEGY

Department of Defense 

Office of the Deputy Under Secretary of Defense 

(Science and Technology) 

September 29, 2000
i

Executive Summary 

This document is an update of Next-Generation Fire Suppression Technology: Strategy for a 

National Program, which was issued by the Office of the Director, Defense Research and 

Engineering in October, 1996. 

Fires and explosions continue to be among the greatest threats to the safety of personnel and the 

survivability of military aircraft, ships, and land vehicles in peacetime and during combat 

operations. For these, halon 1301 (CF3Br) had been the fire suppressant of choice. However, 

production of halon 1301 was banned as of January 1, 1994 due to its high ozone-depleting 

potential (ODP). The DoD is relying on a "bank" of halon 1301 as a temporary means of 

continuing protection during the search for alternatives. Spurring that search is the United 

Nations finding that the non-release of all halons would speed the recovery of the ozone layer. 

Aggressively seeking alternatives to halon 1301, by 1997 the DoD had identified the best 

available replacements. Each of these was demonstrated to have potential, but each also had 

unresolved operational features that compromised its implementation. Recognition of these 

limitations led to the formulation of a new research program to develop improved options. 

In 1997, the Next Generation Fire Suppression Technology Program (NGP) was initiated to 

develop and demonstrate, by 2004, retrofitable, economically feasible, environmentally 

acceptable, and user-safe processes, techniques, and fluids that meet the operational 

requirements currently satisfied by halon 1301 systems in existing weapons systems. The new 

technologies would be of low mass and volume and compatible with the host weapons system 

design. Any new chemicals must have high suppression efficiency and perform well in 

evaluations of ODP, global warming potential, atmospheric lifetime, reignition quenching, 

residue level, electrical conductivity, corrosivity to metals, polymeric materials compatibility, 

long-term storage stability, toxicity of the chemical and its combustion and decomposition 

products, speed of dispersion, and occupational safety requirements. These numerous 

requirements were a challenge to the R&D community. The research approach was organized 

into 6 Technical Thrusts: 

1. Risk Assessment and Selection Methodology develops a process for research program 

managers to choose among alternative technologies for each application. 

2. Fire Suppression Principles establish the mechanisms of flame extinguishment, leading 

to new approaches for fire control. 

3. Technology Testing Methodologies develops test methods and instrumentation to obtain 

data on the effectiveness, toxicity, environmental impact, and materials compatibility of 

new suppressants and their principal degradation products during fire extinguishment.

4. New Suppression Concepts define new ideas in processes, techniques, and fluids for fire 

suppression based on chemical and physical principles. 

5. Emerging Technology Advancement accelerates to maturity a variety of processes, 

techniques, and fluids that are currently under development. 

6. Suppression Optimization develops the knowledge to obtain the highest efficiency of 

each candidate technology. 
ii

The NGP would be complete when the generic technical know-how existed to design costeffective alternatives to halon 1301 systems. Success would eliminate DoD dependence on a 

substance no longer in production and minimize readiness impacts from future use restrictions. 

The planned funding was $46.2 M over 8 years, to come from the DoD Strategic Environmental 

Research and Development Program (SERDP), the Military Department Science and 

Technology Programs, and cost sharing from the participating laboratories. As full funding from 

the Military Departments was not forthcoming, the NGP goal was extended to FY2005. 

Despite funding uncertainties, NGP research has been highly successful in providing both 

necessary understanding of fire suppression and direction for new processes, techniques and 

fluids. As the work progressed, the research has coalesced into the following 6 technical areas. 

The individual research reports and compilations of findings are accessible at the NGP web site: 

www.dtic.mil/ngp. The following is a listing of some of the highlights. 

A. New Flame Suppression Chemistry. The NGP is developing both improved understanding 

to guide the search for new chemicals that perform as well as CF3Br, but without the 

environmental drawback, as well as identifying candidates worthy of further consideration. 

 Combining findings from current and pre-NGP research, NGP scientists have evolved a 

model for how fire suppressant additives quench flames. 

 Using published data, quantitative structure-activity relationships, and laboratory 

screening tests, NGP chemists have examined families containing thousands of chemicals 

to identify those with desirable properties: high fire suppression efficiency, short 

atmospheric lifetime, and low toxicity. 

 Over a dozen bromofluoroalkenes and bromofluoroamines appear promising. 

 Iron-, manganese- and phosphorus-containing compounds have low environmental 

impact and high flame suppression effectiveness. Candidates can be selected on the 

basis of physical or toxicological properties. 

 A number of physically active chemicals might be suitable fire fighting agents. In 

particular, the extinguishing (molar) aerosol concentration of C4F9OCH3 (HFE-7100), 

already approved as a solvent, was determined to be half that of halon 1301 gas. 

B. Suppressant Screening Tests. A set of accurate tests that are quick, inexpensive, and 

require little agent have been developed for screening candidate suppressants. NGP research 

has produced: 

 The first bench-scale suppression screen for measuring flame extinction by both gases 

and liquids, adaptable for powders. 

 A screen for the effectiveness of a burst of suppressant (such as from a solid propellant 

gas generator, SPGG), both in quenching open flames and those stabilized behind an 

obstruction. Preliminary tests with an SPGG injection system have been successful. 

 A hierarchical roadmap through the properties involved in screening for toxicity, 

compatibility with storage container and weapons systems materials, and environmental 

impact. The roadmap identifies the best screening tests for the key properties. 
iii

 Completion of a computer model to evaluate the inhalation hazard resulting from short 

exposures (e.g., from an accidental discharge) to a suppressant. Developed for 

halocarbons, the model can be extended to other suppressants with diverse toxic effects. 

C. New and Improved Aerosol and Powder Suppressants. For some applications, clean 

(volatile) suppressants are not essential. NGP research is directed at finding new approaches to 

condensed phase candidates and ways to improve the use of current suppressants. NGP research 

has shown that: 

 For the highly efficient alkali metal powders, surface area controls the rate of release of 

chemically active K and Na atoms into the flame. The particle size and density dictate 

how efficiently the particles reach the flames. 

 It is possible to store a practical mass of a highly efficient, but otherwise undesirable 

(e.g., toxic) chemical on an inert particle and transport it safely to the fire. 

 For fluids, proper droplet size is key to determining suppressant effectiveness. Fine 

droplets can flow around obstacles, but can evaporate early, so their vaporization is not 

available to cool the flame. Large droplets hit surfaces in their path and are less likely to 

reach the flames and may even pass through the flame without fully evaporating. 

 Water droplets that evaporate near a flame are as effective as halon 1301 on a mass basis. 

Tests and calculations show that droplets with diameters under 20 :m evaporated in 

passing through thin laboratory flames, while many with diameters over 30 :m survived. 

A unique set of computer programs for estimating thermophysical property data for fluids is now 

operational for assessing costly or commercially unavailable fluids on the computer. 

D. Better Suppressant Delivery. This comprises improving the efficiency of getting the 

suppressant to the site of the fire through equipment clutter and unsteady, three dimensional air 

flows. Results include: 

 A new, validated computer code for the prediction of transient, two-phase flows through 

a complex pipe run, enabling determination of the change in discharge rate when 

substituting a new suppressant into the current piping. 

 A new, validated model to describe the rate of agent entrainment into flames behind 

different shapes of obstructions. Traditional halon 1301 systems have been overdesigned 

to compensate for these fires. 

 Two approaches for SPGGs with increased flame suppression efficiency, yet reduced jet 

temperatures and momentum: additive-enhanced propellant formulations and entrainment 

of a chemically active additive into the effluent stream. 

E. Viability of New Suppression Technologies. Improved instrumentation in the test articles 

owned by the Military Department laboratories is important for relating bench- and full-scale 

tests. NGP research has produced: 

 A sensor for measurement and detection of combustible mixtures of oxygen and 

hydrocarbon fuels during a 250 ms fire suppression event. These measurements are 

especially important after suppression in order to assess the possibility of reignition. 
iv

 Two approaches to measuring suppressant concentration based on laser-induced 

breakdown spectroscopy and infrared absorption. 

 The first in situ, time-dependent measurements of HF, its dissipation, and its amelioration 

by additives to the suppressant have now been recorded. HF is a corrosive and toxic 

product of any of the fluorinated fire suppressants (e.g., HFC-227ea and HFC-125) and is 

a principal deterrent to the deployment of these agents. 

NGP fire suppression technologies must also be economically feasible. Accordingly, the NGP is 

nearing completion of a methodology to quantify a fire suppression technology by its life cycle 

cost and to enable superimposing on this a subjective value system. 

F. Improved Fuel Tank Inertion. Research in this area has been limited. Only two aircraft, 

the F-16 and the F-117, currently use halon 1301 to inert fuel tanks when entering combat. The 

Air Force is seriously considering choosing CF3I for this application. Should they do so, then 

alternative technologies for fuel tank inerting would not be an NGP task. Nonetheless, to be 

prepared, NGP staff have completed a small project to assess the current status of alternate 

systems that had in prior decades shown promise for fuel tank inerting.

In November 1999, in the wake of continuing disagreement over the appropriate level of 

funding, agreement was reached on a reduced-scale NGP of $20.2 M. The new goal became: 

“Develop and demonstrate, by 2005, technology for economically feasible, 

environmentally acceptable and user-safe processes, techniques, and fluids that meet the 

operational requirements currently satisfied by halon 1301 systems in aircraft.” 

The focus on aircraft fire suppression emerged from the following: 

• The aircraft safety and survivability engineering teams from all three Services have 

fire suppression needs for engine nacelles and dry bays that were not being addressed 

by S&T efforts outside the NGP. 

• The Army has solutions for both current and planned ground vehicles that needs only 

engineering for implementation. 

• The Navy has no current plans to retrofit current ships and has an S&T program in 

water mist technology for forward fit. 

Thus, the revised NGP addresses the fires that the military customers identify as most needing 

additional research. Research issues that arise in adapting fire suppression technologies for 

ground or sea platforms will need to be addressed by the responsible Military Department. 

By the final expenditure of FY2000 funds, the NGP will deliver understanding of how chemicals 

must interact with flames to be comparable to halon 1301 in quenching efficiency, analysis of 

the world of useful chemicals, identification of the best places to look for alternative 

suppressants and a first set of “best looks,” a suite of screening tests and guidance for their use, 

and a method for determining and comparing the life-cycle costs of new fire suppression 

technologies. 

From that point forward, the NGP will be directed toward two targets. 
v

1. New Flame Suppression Chemicals 

This will extend the examination of those chemical families that show promise of successful 

candidates. This includes further evaluation of some families already identified as having high 

potential, e.g., tropodegradable bromocarbons and phosphorus-containing compounds, and 

families not yet systematically evaluated, e.g., nitrogen-containing compounds, copper-, 

manganese- and tin-containing compounds, and iodine-containing compounds. The research 

will identify trends in suppression effectiveness, toxicity, etc. using NGP screening methods and 

QSARs from prior work. The optimal candidates will be flagged for further development. 

The reduced funding level limits the extent to which individual chemicals can be pursued: 

 Extensive and costly testing for full toxicological examinations will not be performed. 

 A few real-scale tests will be conducted to demonstrate the reliability of the bench-scale 

results as a predictor of the success of agents, rather than full characterization of the 

performance of all candidate agents 

2. Improved Suppressant Storage and Delivery 

Empirical tests have shown that changes in the geometry of agent release can reduce the mass of 

agent needed for suppression. Concurrently, NGP research has related suppressant flow 

properties to the enhanced concentrations needed for the quenching of flames in cluttered spaces 

and has shown the importance of the location where a suppressant fluid vaporizes. 

The NGP will now combine these effects in a model of the interactions between the suppressant 

and the fire in cluttered spaces. This will identify optimal dispensing conditions, nozzle 

locations, etc. for suppression of fires in diverse engine nacelle and dry bay configurations. 

Further work will develop new ways of controlling suppressant discharge properties, approaches 

complementary to the traditional pressurized fluid bottles. Combined, these will constitute a set 

of source terms for the above model and offer flexibility and efficiency to the platform designer. 

Again, the reduced funding limits the extent to which concepts for efficient storage and delivery 

can be examined. 

• The NGP will perform a modest number of indicative real-scale experiments to 

demonstrate the effectiveness of the new distribution principles, rather than rigorously 

establishing the validity of the models. 

• These tests will mainly be monitored using video cameras. The instrumentation to 

establish model validity will not be developed or adapted. 

• These models and technologies will be turned over to the platform managers for 

optimization testing in their particular configurations. 

The prognosis for successfully meeting the revised NGP goal is excellent, given the technical 

infrastructure and cadre of experts already advanced by the NGP. The Department of Defense 

will then need to set in place the programs to develop the new technologies for implementation 

in its fleet of aircraft 
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Table of Contents 

Executive Summary ................................................................................ i 

I. Introduction ................................................................................. 1 

II. Prior DoD Halon Alternatives Research ................................................ 2 

A. Background ........................................................................ 2 

B. Halon Alternatives R&D Steering Group (HASG) ........................... 3 

C. Initial Technology Strategy and Technology Development Plan ............ 3 

D. Remaining Fire Suppression System Technology Options ................... 4 

III. The Next Generation Fire Suppression Technology Program 1996-2000 .......... 5 

A. Formulation ........................................................................ 5 

B. Operation ........................................................................... 7 

C. Evolution of NGP Funding ....................................................... 8 

A. Environmental Developments .................................................... 8 

IV. NGP Program and Technical Progress ................................................... 10 

A. New Flame Suppression Chemistry ............................................. 13 

B. Suppression Screening Tests ..................................................... 15 

C. New and Improved Aerosol and Powder Suppressants ....................... 15 

D. Better Suppressant Delivery ...................................................... 17 

E. Viability of New Suppression Technologies ................................... 17 

F. Improved Fuel Tank Inertion ..................................................... 18 

V. Reformulation of the NGP ................................................................. 19 

A. Focussed Goal ...................................................................... 19 

B. Technical Approach of the Revised Program .................................. 20 

C. Additional Efforts .................................................................. 22 

VI. Conclusion ................................................................................... 23 
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I. Introduction

This document is an update of Next-Generation Fire Suppression Technology: Strategy for a 

National Program, which was issued by the Office of the Director, Defense Research and 

Engineering in October, 1996. The reader should examine that document for a full 

understanding of the DoD rationale for and approach to research to replace halon 1301 with 

technologies of comparable performance. 

Since that date, the commercial context in which the search for alternatives to halon 1301 is 

proceeding has sharpened. A number of facilities have ceased fire protection, installed water 

sprinklers, or converted to one of the marketed halon alternatives, notably hydrofluorocarbons 

(HFCs) or mixtures of inert gases. Some have converted to blends of chemicals that include 

ozone-depleting hydrochlorofluorocarbons (HCFCs), even though these are slated for phase-out. 

There remain a small number of essential uses of halon 1301 (in national defense and 

commercial aviation) for which suitable alternative technologies have not yet been found. For 

these, the desire for space- and weight-efficient alternatives continues. To the extent that these 

technologies might involve new chemicals, those chemicals must have significant attributes 

beyond high fire suppression efficiency. They must also perform well in evaluations of their 

ozone depletion potential (ODP), global warming potential (GWP), atmospheric lifetime, 

reignition quenching, residue level, electrical conductivity, corrosivity to metals, polymeric 

materials compatibility, stability under long-term storage, toxicity of the chemical and its 

combustion and decomposition products, speed of dispersion, and safety and occupational health 

requirements. This multiplicity of requirements continues to present a challenge to the R&D 

community. 

The DoD Next Generation Fire Suppression Technology Program (NGP) is still the largest effort 

focussed on finding fire suppression technologies alternate to the use of halon 1301. There is a 

little research in the European Community, some work on the use of water sprays, and an 

occasional new candidate offered by commercial firms. NGP researchers are capitalizing on 

these other efforts. 

NGP research has made considerable technical progress in the nearly four years since its 

inception. The individual research reports and compilations of findings are accessible at the 

NGP web site: www.dtic.mil/ngp. The following text presents the evolution of the NGP in 

response to that technical progress and to commercial and political changes. It begins by 

reiterating the motivation for the NGP, then presents the evolution of the NGP from its 

inception, summarizes the NGP research accomplishments to date, denotes the change in NGP 

scope beginning in FY2000, and delineates the NGP strategy from that point forward. 
3

II. Prior DoD Halon Alternatives Research

A. Background

Fires and explosions continue to be among the greatest threats to the safety of personnel and the 

survivability of military aircraft, ships, and land combat vehicles in peacetime and during 

combat operations. For the past three decades, halon 1301 (CF3Br) had been the agent of choice 

for fire extinguishment and explosion suppression (hereafter referred to collectively as fire 

suppression) in both weapon systems and facilities in the DoD, the private sector, and for other 

countries' armed forces and domestic needs. The DoD applications are shown in Table 1. 

Table 1: Fielded Weapon Systems Applications for Halon 1301 

Army Navy/Marine Corps Air Force 

Ground Armored Vehicles 

 - crew compartments 

 - engine compartments 

Aircraft 

 - engine nacelles 

 - APU compartments 

Maritime Craft 

Hand-Held Extinguishers 

 - air/ground/maritime 

Communications Shelters 

Shipboard 

 - propulsion machinery 

 - flammable liquid 

storerooms 

 - fuel pump rooms 

 - emergency generator 

rooms 

Aircraft 

 - engine nacelles 

 - dry bays 

 - fuel tanks 

 - crew compartments 

Ground Armored Vehicles 

 - crew compartments 

 - engine compartments 

Hand-held Extinguishers 

Aircraft 

 - engine nacelles 

 - dry bays 

 - fuel tanks 

 - weapon bays 

 - cargo bays 

Facilities 

Hand-held Extinguishers 

Due to its high ozone-depleting potential (ODP), halon 1301 was banned from production as of 

January 1, 1994 by the 1992 Copenhagen Amendments to the 1987 Montreal Protocol on 

Substances That Deplete the Ozone Layer. Both domestically under the guidance of the 

Environmental Protection Agency (EPA) and internationally under the guidance of the United 

Nations Environmental Program (UNEP), the fire suppression community has committed to 

reducing its dependence on this chemical. There now exist a limited number of essential halon 

1301 uses - those which are of paramount importance and for which no functional replacement 

exists. The stewards of such uses (e.g., the DoD, NASA, the commercial aircraft industry) have 

created "banks" of existing and recycled halon 1301 as a temporary means of continuing 

protection while a search for viable alternatives is pursued. 

The DoD in particular adopted an aggressive policy concerning technology efforts aimed at 

seeking alternatives to ozone-depleting substances (ODSs). In the February 13, 1989 directive, 
4

it was stated that DoD Components "... shall conduct R&D to identify or develop alternate 

processes, chemicals, or techniques for functions currently being met by CFCs and halons;" that 

the Director, Defense Research and Engineering (DDR&E) "... shall coordinate R&D programs, 

as appropriate, on alternative chemicals or technologies for fire and explosion suppression and, if 

necessary, other CFCs;" and that the Military Departments and Defense Agencies "... shall 

conduct R&D programs, as needed, to support mission requirements, with emphasis on 

substitutes for halons." 

B. Halon Alternatives R&D Steering Group (HASG) 

The Director, Defense Research and Engineering, established the HASG in September 1991 to 

formulate (and oversee the execution of) an integrated DoD near-term technology strategy and 

technology development plan to identify suitable alternatives for all ODSs. 

• Chair: Director, Advanced Technology, in the Office of the Director, Defense 

Research and Engineering (ODDR&E) 

• Vice-chair: Deputy Director, Operational Test and Evaluation/Live Fire Testing 

(DDOTE/LFT), Office of the Secretary of Defense 

• Vice-chair: Staff Specialist for Survivability, Office of Strategic and Tactical 

Systems/Air Warfare (ODDS&TS/AW), Office of the Under Secretary of Defense 

for Acquisition and Technology (OUSD(A&T)). 

C. Initial Technology Strategy and Technology Development Plan 

The HASG formulated the DOD Technology Strategy For Alternatives To Ozone- Depleting 

Substances For Weapon Systems Use, approved by the DDR&E on August 31, 1992, to guide 

the near-term investigation and performance testing of commercially available chemicals: CFCs 

currently used in weapon systems applications for refrigeration and environmental control, and 

for general and precision cleaning, as well as the halons used for fire fighting. The HASG then 

developed an execution plan, the DOD Technology Development Plan for Alternatives to OzoneDepleting Substances for Weapon Systems Use (TDP), which was approved by the DDR&E on 

June 28, 1993 and was updated annually. Executed by the Army, Navy and Air Force, the 

Strategy and the TDP together formed the overall DoD near- term response to the impact of the 

Montreal Protocol on weapon systems. 

Research under the TDP was completed in FY 1997, and the reader is referred to the document: 

Technology Development Plan for Alternatives to Ozone-Depleting Substances for Weapons 

System Use: Final Report (September, 1998). The successes for firefighting were of major 

consequence: 

 two suppressants, NaHCO3 powder and HFC-227ea (C3 F7H) were identified as 

candidates for the engine compartments in ground vehicles; 

 water mist and HFC-227ea were identified for shipboard machinery spaces and 

storage compartments; and 
5

 HFC-125 (C2 F5H) and solid propellant-based inert gas generators were identified 

for aircraft engine nacelles and dry bays. 

Each of these was demonstrated to be a viable approach, and design equations were developed 

for a few applications. However, water mist systems were shown to need further research before 

they could assure fire control in general shipboard applications. Inert gas generators also needed 

further development to overcome the hazards of excessive heat generation and ejection jet 

intensity. HFC-125 and HFC-227ea each have storage volume and weight penalties 2-3 times 

that of an equivalent extinguishing concentration of halon 1301. Additionally, during 

suppression they generate significant levels of toxic and corrosive HF. 

Thus, while the TDP had arrived at alternatives for most ODSs, the best available replacements 

for halon 1301 had limited applicability. Some solutions could be implemented because the 

halon system was overdesigned or because the design requirements had changed. However, in 

many cases, the implementation of TDP technologies would require costly redesign and 

reconfiguration of the installed fire suppression systems and have a negative impact on weapon 

systems capabilities. 

D. Remaining Fire Suppression System Technology Options

As the TDP progressed, it became clear that there were three fire suppression tactics for weapons 

system program managers: utilize identified near-term replacements, vintage the existing halon 

systems, or cease fire protection altogether. Each of these options presented significant trade-off 

considerations. The use of dissimilar fluids required costly re-engineering of the fire suppression 

system (and the host weapon system); the vintaging of fielded weapon systems required 

indefinite dependence on a substance that was no longer in production and which was subject to 

future environmental regulations. The abandonment of fire protection altogether was not 

feasible since personnel safety and weapon systems survivability are high DoD priorities. 

Recognition of these limitations led to a decision to formulate a successive research program 

focused on improved options for fire suppression in fielded weapons systems. 
6

III. The Next Generation Fire Suppression Technology Program 

1996-2000

A. Formulation

After nearly 3 years in development and review, the NGP was initiated in FY 1997 with the goal 

to develop and demonstrate, by 2004, retrofitable, economically feasible, environmentally 

acceptable, and user-safe processes, techniques, and fluids that meet the operational 

requirements currently satisfied by halon 1301 systems in aircraft, ships, land combat vehicles, 

and critical mission support facilities. The results would be specifically applicable to fielded 

weapon systems and would provide fire suppression technologies for preserving both life and 

operational assets. Successful completion of the NGP would eliminate DoD dependence on a 

substance no longer in national production and minimize any readiness impacts that could result 

if halon 1301 use restrictions were imposed in the future. 

The new fire suppression technologies would be of low mass and volume and compatible with 

the host weapons system design. Successful candidates would also perform satisfactorily in a 

wide variety of tests for fire suppression efficiency, reignition quenching, ODP, global warming 

potential (GWP), atmospheric lifetime, suppressant residue level, electrical conductivity, 

corrosivity to metals, polymeric materials compatibility, stability under long-term storage, 

toxicity of the chemical and its combustion and decomposition products, speed of dispersion, and 

safety and occupational health requirements. 

The research approach, developed by government, industry and academic experts, was 

organized into 6 Technical Thrusts and 24 Research Elements. The Research Elements, listed 

here, are described more fully in Appendix B of the 1996 Strategy Document. 

1. Risk Assessment and Selection Methodology develops a process for research 

program managers to choose among alternative technologies for each application 

by applying modern decision-making techniques. 

 A. Development of Model Fires from DoD Fire Data 

B. Ullage Inerting In-Flight Data Collection 

C. Relative Benefit Assessment of Fire Protection System Changes 

2. Fire Suppression Principles establish the mechanisms of flame extinguishment 

using detailed experimental studies and computational models, leading to new 

approaches for fire control. 

A. Mechanisms of Ultra-High Efficiency Chemical Suppressants 

B. Suppression Dynamics of Fine Droplets and Particles 

C. Stabilization of Flames 

D. Explosion Inhibition Processes 

3. Technology Testing Methodologies select, adapt, and develop test methods and 

instrumentation to obtain data on the effectiveness, toxicity, environmental 

impact, and materials compatibility of new suppressants and their principal 

degradation products during the fire extinguishment process. 

A. Suppression System Effectiveness Screening 
7

B. Agent Compatibility With People, Materials and the Environment 

C. Instrumentation for Gaseous Fuels, Oxygen, and Suppressant 

Concentration Measurements During Suppression of Flames and 

Explosions

4. New Suppression Concepts define new ideas in processes, techniques, and fluids 

for fire suppression based on chemical and physical principles.

A. Powder-Matrix Systems 

B. Evaluation of Highly Effective Chemical Suppressants 

C. Super-Effective Thermal Suppressants 

D. New and More Effective Fire Suppression Technologies that are Presently 

Conceptual 

5. Emerging Technology Advancement accelerates to maturity a variety of 

processes, techniques, and fluids that are currently under development. 

 A. Liquid Mist Systems 

B. Advanced Flame Arresting Foams for Fuel Tank Inerting 

C. Active Suppression for Fuel Tank Explosions 

D. Advanced Propellant/Additive Development for Gas Generators 

E. Enhanced Powder Panels 

6. Suppression Optimization develops the knowledge to obtain the highest 

efficiency of each candidate technology. 

A. Fire Suppressant Dynamics in the Fire Compartment 

B. Suppressant Flow Through Piping 

C. Mechanism of Unwanted Accelerated Burning 

D. Development and Evaluation of Automatically Actuating Pre-Dispersed 

Agent Storage Containers 

E. Full-Scale Optimization of Advanced Fire Suppression Technologies 

The planned funding for the NGP was estimated to be $46.2 M over 8 years. Support was to 

come from the DoD Strategic Environmental Research and Development Program (SERDP), the 

Military Department Science and Technology Programs, and cost sharing from the participating 

laboratories. 
8

The major milestones for the NGP were: 

• Description and tabulation of the broad classes of model fires to be suppressed by the end 

of FY 1998. 

• Implementation of improved laboratory-scale test methods for measuring the 

performance, compatibility, and degradation of new suppressants during the fire 

extinguishment process during FY 1998-1999. 

• Selection for further R&D of the first set of new technologies resulting from a broad 

public solicitation of ideas by the end of FY 1999. 

• Completion of a core methodology for DoD program executives/managers to evaluate the 

impact of selecting alternative fire suppression systems on each weapons system by the 

end of FY 2001. 

• Demonstration of a suite of computer models of the fire suppression processes for 

creating new suppression approaches and optimizing current ones (based on specific 

critical physical and chemical principles) by the end of FY 2001. 

• Identification of next-generation mist, inert gas generator, and powder technologies by 

the end of FY 2001. 

• Establishment of engineering models for an array of techniques to optimize the use of 

next-generation fire suppression technologies by the end of FY 2004. 

• Demonstration of the effectiveness of a wide variety of new technologies and/or 

techniques over the period FY 1999-2004. 

The NGP technology development process was considered to be complete when the generic 

technical know-how existed to design cost-effective alternatives to halon 1301 systems. 

B. Operation

In 1996, Dr. Richard G. Gann of the National Institute of Standards and Technology was 

appointed as Technical Program Manager. The following were appointed as members of the 

Technical Coordinating Committee: 

Mr. Michael J. Bennett, AFRL 

Dr. William L. Grosshandler, NIST 

Dr. Andrzej W. Miziolek, ARL 

Dr. Ronald S. Sheinson, NRL 

In 1998, Mr. Martin L. Lentz of AFRL replaced Mr. Bennett, and in 1998, Mr. E. Lawrence Ash 

of NAVAIR was added to the TCC. 

The HASG provided program oversight to the NGP. It met annually to review program 

progress, coordinated the recommended next-year program and solicitations for new proposals, 

and forwarded the proposed program and solicitations to SERDP for funding consideration. In 

addition to the Chair and Vice-chairs listed above, the HASG included members from: 
9

 the Office of the Deputy Under Secretary of Defense for Environmental Security 

 the Military Departments 

 DoD Agencies 

 liaison personnel from other Federal agencies. 

Gamboa International Corporation continued to provide the HASG Secretariat and was selected 

to serve as the NGP Program Support Office. 

Each year, the topics for new research were selected by the TCC, with review from the HASG, 

and SERDP. Proposals were solicited broadly from government laboratories, academia and the 

private sector. The proposals were peer reviewed, with the TCC formulating a program for 

approval by HASG and SERDP. 

Communication among the research team members was enhanced by an annual autumn 

introduction session, an annual NGP research meeting, and extensive participation in the annual 

Halon Options Technical Working Conference. All NGP reports and publications are posted on 

an NGP web site, www.dtic.mil/ngp.

C. Evolution of NGP Funding 

NGP research began as planned in the start-up year of FY1997, with funding from SERDP and 

cost sharing from the participating laboratories. A successful solicitation for a full slate of 

projects for FY1998 was completed. However, while the Army applied some funds to the 

FY1997 and FY1998 program, it became clear that full funding from the three Military 

Department Science and Technology Programs would not be forthcoming. As an interim 

consequence, the NGP goal was extended to FY2005, and a number of projects that had been 

approved to begin in FY1998 were deferred to future years. 

Further solicitations for proposals were conducted for FY1999 and FY2000. No funding from 

the three Military Department Science and Technology Programs materialized. Thus, a number 

of approved projects were again deferred. 

D. Environmental Developments 

The international community responded dramatically to the potential for severe environmental 

hazard from depletion of the earth’s ozone layer. Replacements for refrigerants and solvents 

were identified and implemented. The use of the halon fire suppressants was greatly reduced by 

a number of measures: 

 implementing the use of alternative agents for those applications where commercial 

chemicals were feasible, 

 eliminating fire protection altogether in some applications, 

 using non-ozone-depleting chemicals for fire fighting training, for certifying halon 

systems, etc. 
10

In 1994, the UNEP announced that just after the turn of the century, the mass of chlorine and 

bromine (and the accompanying ozone depletion) in the stratosphere would have peaked and 

would begin to diminish. Their report also identified four principal actions that would speed this 

decrease. The second most effective of these was the non-release of all halons currently in 

existing equipment. This was a clear signal to the fire protection community that the world was 

watching the effort to identify and implement alternatives to the halons and that an accelerated 

phase-out was a clear possibility. In related activity, research was underway to develop 

processes for the economical conversion of the halogenated hydrocarbons into other useful 

chemicals. 

As the ozone depletion threat was being successfully addressed, worldwide concerns over global 

warming continued to rise. These culminated in the drafting of the Kyoto Accords late in 1997. 

While these have not yet been universally accepted and while no action plans for reducing 

greenhouse emissions have been implemented, this document makes it essential that current and 

future chemicals be examined for their absorption of infrared solar radiation. 

The reality of both stratospheric and tropospheric impact of released chemicals led to the general 

recognition of atmospheric lifetime as a principal property for consideration in the development 

of alternatives. Focusing on chemicals that did not persist in the environment would provide 

some assurance that they would not be major factors in ODP, GWP, and any future deleterious 

environmental effects. 
11

IV. NGP Program and Technical Progress

NGP research has been highly successful in providing both necessary understanding of fire 

suppression and direction for new processes, techniques and fluids. As the work progressed, the 

research has coalesced into 6 technical areas: 

 New Flame Suppression Chemistry 

 Suppressant Screening Tests 

 New and Improved Aerosol and Powder Suppressants 

 Viability of New Suppression Technologies 

 Better Suppressant Delivery 

 Fuel Tank Inertion 

Table 1 shows a listing of the project titles. A crosswalk with the original Thrusts and Research 

Elements can be discerned from the project numbers. These have the code: AB/C/xxx, where A 

is the Thrust number, B is the Research Element letter, C is the sequential number of project 

under that Research Element, and xxx are the last numbers of the fiscal years that the project was 

supported. 
12

 Table 1. NGP Project Titles and Investigators

______________________________________________________________________________________________ 

1A/1/78. DEVELOPMENT OF MODEL FIRES FOR FIRE SUPPRESSION RESEARCH 

 Principal Investigator: Anthony Finnerty, ARL

 Associate Investigators: James Tucker, AFRL and Juan Vitali, ARA; Ronald Sheinson, NRL 

1C/1/890. RELATIVE BENEFIT ASSESSMENT OF FIRE PROTECTION SYSTEM CHANGES 

 Principal Investigator: Michael Bennett, Eglin AFB 

 2A/1/7890, /2/890. MECHANISMS OF ULTRA-HIGH EFFICIENCY CHEMICAL SUPPRESSANTS 

 Principal Investigator: Kevin McNesby, ARL 

 Associate Investigator: James Fleming, NRL 

2B/1/7890. SUPPRESSION EFFECTIVENESS OF AEROSOLS AND PARTICLES 

 Principal Investigator: Ronald Sheinson, NRL 

 

2B/2/89. DROPLET INTERACTIONS WITH HOT SURFACES 

Principal Investigator: Yudaya Sivathanu, En’Urga, Inc. 

COR: William Grosshandler 

2B/3/89. TECHNICAL SUPPORT FOR THE STUDY OF DROPLET INTERACTIONS WITH HOT 

SURFACES 

 Principal Investigator: Jiann Yang, NIST 

2C/1/789. STABILIZATION OF FLAMES 

Principal Investigator: Vincent Belovich, AFRL 

3A/1/789. DISPERSED LIQUID AGENT FIRE SUPPRESSION SCREEN 

 Principal Investigator: Jiann Yang, NIST 

3A/2/890. TRANSIENT-APPLICATION-RECIRCULATING-POOL-FIRE AGENT 

EFFECTIVENESS SCREEN 

 Principal Investigator: William Grosshandler, NIST 

3B/1/89. TOXICOLOGICAL ASSESSMENT OF HUMAN HEALTH CONSEQUENCES 

ASSOCIATED WITH INHALATION OF HALON REPLACEMENT CHEMICALS 

Principal Investigator: Darol Dodd, AFRL 

3B/2/8. AGENT COMPATIBILITY WITH PEOPLE, MATERIALS AND THE ENVIRONMENT

Principal Investigators: Marc Nyden, NIST 

 Stephanie Skaggs, Universal Technical Services 

3C/1/789. LASER-BASED INSTRUMENTATION FOR REAL-TIME, IN-SITU MEASUREMENTS 

OF COMBUSTIBLE GASES, COMBUSTION BY-PRODUCTS, AND SUPPRESSANT 

CONCENTRATIONS

Principal investigator: Kevin McNesby, ARL 

3C/2/890. FAST RESPONSE SPECIES CHARACTERIZATION DURING FLAME SUPPRESSION 

Principal Investigator: George Mulholland, NIST 
13

4A/1/89. POWDER-MATRIX SYSTEMS 

Principal Investigators: Gregory Linteris, NIST 

4B/1/8. TROPODEGRADABLE BROMOCARBON EXTINGUISHANTS 

Principal Investigator: J. Douglas Mather, NMERI 

COR: Ronald Sheinson 

4B/2/8,4D/3/7. FLAME INHIBITION BY PHOSPHORUS-CONTAINING COMPOUNDS 

Principal Investigator: Elizabeth M. Fisher, Cornell University 

COR: Andrzej Miziolek, ARL 

4B/3/890. ENVIRONMENTAL IMPACT OF NEW CHEMICAL AGENTS FOR FIRE 

SUPPRESSION 

Principal Investigators: Robert Huie, NIST, and Andrzej Miziolek, ARL 

4B/4/0. PERFORMANCE DATA ON COLD TEMPERATURE DISPERSION OF CF3I AND ON 

MATERIALS COMPATIBILITY WITH CF3I

 Principal Investigator: Jiann Yang, NIST 

4B/5/0. ASSESSMENT OF COMPLETENESS OF SEARCH FOR ALTERNATIVE 

SUPPRESSANT CHEMICALS 

 Principal Investigator: Richard G. Gann, NIST 

4C/1/890. SUPER-EFFECTIVE THERMAL SUPPRESSANTS 

 Principal Investigator: William M. Pitts, NIST 

4D/1/7. ELECTRICALLY CHARGED WATER MISTS FOR EXTINGUISHING FIRES 

 Principal Investigator: Charles H. Berman, Titan Corp. 

 COR: Ronald Sheinson, NRL 

4D/2/7. IDENTIFICATION AND PROOF TESTING OF NEW TOTAL FLOODING AGENTS 

 Principal Investigator: Robert E. Tapscott, NMERI 

 COR: Andrzej Miziolek, ARL 

4D/4/7. DEVELOPMENT OF A SELF ATOMIZING FORM OF WATER 

 Principal Investigator: Richard K. Lyon, EER, Inc. 

 COR: William Grosshandler, NIST 

4D/5/8. MAIN GROUP COMPOUNDS AS EXTINGUISHANTS 

 Principal Investigator: J. Douglas Mather, NMERI 

 COR: Ronald Sheinson, NRL 

4D/6/8. DUAL AGENT APPROACH TO CREW COMPARTMENT EXPLOSION SUPPRESSION 

 Principal Investigator: Douglas Dierdorf, ARA Corp. 

 COR: Andrzej Miziolek, ARL 

4D/7/8. DENDRITIC POLYMERS AS FIRE SUPPRESSANTS 

 Principal Investigator: Nora Beck Tan, ARL 

4D/13. EFFECTIVE, NON-TOXIC METALLIC FIRE SUPPRESSANTS 

 Principal Investigator: Gregory Linteris, NIST 
14

4D/14. FLUOROALKYL PHOSPHOROUS COMPOUNDS 

 Principal Investigator: Robert Tapscott, NMERI 

4D/15/0. TROPODEGRADABLE BROMOCARBON EXTINGUISHANTS II 

 Principal Investigator: J. Douglas Mather, NMERI 

 COR: Ronald Sheinson, NRL 

4D/17/0. A METHOD FOR EXTINGUISHING ENGINE NACELLE FIRES BY USE OF 

INTUMESCENT COATINGS 

 Principal Investigator: Ginger Bennett, Booz-Allen 

 COR: Martin Lentz, Eglin AFB 

5A/1/0. PARAMETRIC INVESTIGATION OF DROPLET ATOMIZATION AND DISPERSION 

OF LIQUID FIRE SUPPRESSANTS 

 Principal Investigator: Cary Presser, NIST 

5C/1/9. ACTIVE SUPPRESSION FOR FUEL TANK EXPLOSIONS

 Principal Investigator: Leonard Truett, Eglin AFB 

5D/1/90. ADVANCED PROPELLANT/ADDITIVE DEVELOPMENT FOR GAS GENERATORS 

 Principal Investigator: Gary Holland, Primex Aerospace 

 Associate Investigator: Russell Reed, NAWC-WPNS 

 COR: Lawrence Ash, NAVAIR 

5E/1. ENHANCED POWDER PANELS 

 Principal Investigator: John Vice, Skyward, Inc.

 COR: Marty Lentz, Eglin AFB

6A/1/0. FIRE SUPPRESSANT DYNAMICS IN THE FIRE COMPARTMENT

 Principal Investigator: David Keyser and Lawrence Ash, NAVAIR 

6B/1/89. SUPPRESSANT FLOW THROUGH PIPING 

 Principal Investigator: John Chen, Lehigh University

 COR: William Grosshandler, NIST

6C/1. MECHANISM OF UNWANTED ACCELERATED BURNING 

 Principal Investigator: William Pitts, NIST

______________________________________________________________________________________________ 

The following is a brief summary of the key NGP research accomplishments to date. For more 

detail, the reader is referred to the NGP Annual Reports at the NGP web site. 

A. New Flame Suppression Chemistry

An economical way to effect retrofit of a fire suppression system would be with a new chemical 

that performs as well as CF3Br, but without the environmental drawback. The NGP is 

developing both improved understanding to guide the search as well as identifying candidates 

worthy of further consideration. 
15

1. Combining findings from current and pre-NGP research, NGP scientists have evolved a 

model for how fire suppressant additives quench flames. Flame propagation relies on fast 

reactions of the free radical pool (OH radicals and O and H atoms) with fuel molecules. In 

uninhibited flames, these three species are in equilibrium with each other, but are well above 

equilibrium with their surroundings. High efficiency suppressants (e.g., those containing 

bromine, phosphorous or metal atoms) catalytically reduce the radical pool to a near-equilibrium 

level. However, the flame can still continue to burn at these lower radical concentrations. 

Significant thermal mass must also be added to reduce the flame temperature and thus decrease 

the flame propagation kinetics to non-combustion-sustaining rates. Extinguishing concentrations 

thus have a lower fundamental limit, perhaps of the order of 1-2 mass percent, regardless of the 

degree of chemical activity. 

2. Using published data, quantitative structure-activity relationships, and laboratory screening 

tests, NGP chemists have examined families containing thousands of chemicals to identify those 

with desirable properties: high fire suppression efficiency, short atmospheric lifetime, and low 

toxicity. 

a. Compounds with a bromine atom and a tropospherically reactive chemical feature 

should manifest high flame suppression efficiency and low atmospheric lifetime. Eight 

bromofluoroalkenes have calculated atmospheric lifetimes of the order of a week and 

measured extinguishment concentrations not far from that of CF3Br. Inhalation toxicity 

screening data, conducted by the Advanced Agent Working Group, indicates that 4 of 

these show no aftereffects in rats from a 15-minute exposure to 5 volume percent. An 

additional 8 bromofluoroamines also appear promising. 

b. The phosphorus atom is effective in flame retardancy and phosphorus-containing 

chemicals (PCCs) should have low environmental effect. NGP research indicates that 

most PCCs should show high flame suppression effectiveness, largely determined by 

phosphorus loading, so candidates can be selected on the basis of physical or 

toxicological properties. 

c. Examination of over 1500 thermal agents identified about 25 compounds which might 

be suitable fire fighting agents, some of which are already in use. A variety of families 

including ethers, furans, amines, and straight-chain hydrocarbons are represented, almost 

all highly fluorinated. In particular, C4F9OCH3 (HFE-7100), already approved by EPA 

as a solvent, shows promise. Calculations indicate it is environmentally benign. Using 

the Dispersed Liquid Agent Screen (see Screening Tests below), the extinguishing 

(molar) concentration of the aerosol was determined to be half that of halon 1301 gas. 

d. To enable quantification of this aerosol evaporation effect, NGP research has 

developed two devices (an electrostatic atomization system and an inductively coupled 

plasma nebulizer) for seeding the air streams of laboratory burners with fine droplets of 

controlled dimension. The ability to vary the droplet size makes it possible to study both 

chemical effects, after droplet vaporization, and the physical effects of the droplets. 

e. Previous research had shown that Fe(CO)5 is a near ideal flame radical reducer, but is 

highly toxic. Ferrocene, a decidedly less toxic iron-containing compound, produced 

nearly identical results, indicating that the binding state of the iron does not alter the 
16

flame suppression behavior. Thus, future examination of iron compounds can focus on 

their toxicity and their physical properties. 

f.. A flame quenching mechanism for manganese-containing compounds was developed. 

It showed that these known combustion modifiers operate chemically like iron-containing 

compounds. 

B. Suppressant Screening Tests

Of the large number of chemicals to be considered in the search for replacement suppressants, 

many can be discarded based on available information. For the rest, screening tools are needed 

to identify those relatively few agents that should be investigated aggressively. A set of accurate 

screens that are quick, inexpensive, and require little agent will be completed in calendar 2000. 

1. A measure of fire suppression efficiency for high volatility (gaseous) and low volatility 

(liquid) fluids is mandatory. The NGP has developed the first bench-scale suppression screen 

for comparing the flame extinction performance of both gases and liquids and can do adapted for 

powders. The Dispersed Liquid Agent Screen (DLAS) is now in steady use both to obtain 

suppression efficiency data on candidate suppressant fluids and as a research tool. Fabrication 

drawings and an operations manual have been prepared for distribution to interested laboratories. 

2. A second NGP apparatus can screen the effectiveness of a short burst of suppressant (such as 

would emerge from a solid propellant gas generator, SPGG), both in quenching open flames and 

those stabilized behind an obstruction. Preliminary tests with an SPGG injection system have 

been successful. 

3. The NGP has produced a hierarchical roadmap through the maze of properties involved in 

screening for toxicity, with storage container and weapons systems materials, and with the 

environment. It also identifies the best screening tests for the key properties. 

4. The NGP sponsored completion of a physiologically based pharmacokinetic (PBPK) model 

of a human system that incorporates a breath-by-breath description of respiration and follows the 

inhaled suppressant to the bloodstream. Developed for halocarbons, the model can be extended 

to other suppressants with diverse toxic effects. 

5. Computational screening capacity tool for a suppressant’s atmospheric lifetime is continuing 

and has been validated for halomethanes. Calculations for fluoroethanes and the ethers derived 

from them have reproduced the experimental trends. 

C. New and Improved Aerosol and Powder Suppressants

For some applications, clean (volatile) suppressants are not essential. To this end, fine water 

mist and efficient powders have been the subjects of real-scale testing; however, the approaches 

to date have not met with universal success. As with gaseous and vapor suppressants, NGP 

research is directed at finding new approaches to condensed phase candidates and ways to 

improve the use of current suppressants. 
17

1. Sodium and potassium bicarbonate powders are more efficient fire suppressants than halon 

1301 on a mass basis. However, once released these powders obscure vision and are corrosive to 

some surface materials, such as aluminum. Thus alternative approaches are needed. 

a. The alkali metal atoms released when sodium or potassium bicarbonate powders 

decompose in a flame tie up the reactive flame radicals. The surface area of the particles 

controls the rate of release of these species into the flame. The powder particle size and 

density dictate how closely the particles follow the flame gas velocity streamlines and 

thus how efficiently the particles reach the flames. 

b. It is possible to store a practical mass of a highly efficient, but otherwise undesirable 

(e.g., toxic) chemical on an inert particle and transport it safely to the fire. As much as 

200 weight percent of Fe(CO)5 can be absorbed into aerogels; and at 250 °C a large 

fraction is desorbed. The speed of agent liberation is being determined. Pyrophoric 

chemicals, such as Fe(CO)5, are not appropriate for this type of transport, as they can 

react with water adsorbed on the host. 

2. Nearly all suppressant fluids emerge from pressurized storage containers as liquids along with 

a gaseous component. The properties of the liquid (a) determine its transport effectiveness to the 

fire, (b) the magnitude of its effect on the flames, (c) its ability to quench condensed fuels, and 

(d) its impact on preventing reignition. It is not known if the optimal values of these liquid 

properties are uniform for these four impacts. Consideration of droplet size is especially 

important. Very fine droplets follow the propellant gas streamlines and thus can flow around 

obstacles. However, they can evaporate before reaching the flame zone, and their heat of 

vaporization is not available to cool the flame. Large, high-momentum droplets impact surfaces 

in their path, reducing their likelihood of reaching the flames. Too large droplets may pass 

through the flame without fully evaporating. There is thus a premium in knowing and thus 

specifying the optimal droplet size and velocity ranges. 

a. If water droplets can evaporate in or near the flame, water is as effective as halon 1301 

on a mass basis. NGP experiments showed that droplets with diameters under about 20 

:m completely evaporated in passing through the thin flames of laboratory burners, while 

a significant number of droplets with diameters over about 30 :m survived. Calculations 

verify that water droplets with diameters under about 50 :m should evaporate near the 

flame front. 

b. In storage facilities and machinery spaces, the quenching of flame spread over liquid 

and solid fuels is of concern. Experiments showed that flame spread decreases with the 

mass of water incident on the surface, with little effect of droplet diameter. However, 

buoyancy from the hot surface may keep small droplets from reaching the surface. 

c. A unique set of computer programs for estimating the thermophysical property data 

for fluids is now operational. As the NGP examines new fluids, some not commercially 

available, and as solutions emerge as serious candidates (e.g., aqueous sodium lactate) 

these estimates will become pivotal. 

D. Better Suppressant Delivery
18

The complement to identifying new suppressants is improving the efficiency of getting the 

suppressant to the site of the fire. This comprises storage and discharge technology, transport 

through any distribution piping and transport throughout the compartment space (with equipment 

clutter and unsteady, three dimensional air flows) once the agent has been dispensed from the 

storage/distribution hardware. 

1. Replacement fluids must function within the existing distribution plumbing to avoid the major 

cost of replacing the piping. NGP engineers have completed and validated a new computer code 

for the prediction of transient, two-phase fire suppressant flows through a complex pipe run, 

enabling determination of the change in discharge rate when substituting a new suppressant into 

the current piping. 

2. Traditional halon 1301 systems have been overdesigned to compensate for (a) the transient 

release of the suppressant and (b) the presence of numerous obstructions or clutter. NGP 

engineers have developed and validated a model to describe the rate of agent entrainment into 

flames behind different shapes of obstructions. The model develops design criteria for the free 

stream agent concentration and injection period needed for extinguishment. 

3. NGP research is developing new types of SPGGs that have increased flame suppression 

efficiency with reduced jet temperatures and momentum. One approach is to create additiveenhanced propellant formulations. A second approach directs the hot gas generator discharge 

from an “inert” solid propellant across an “activated” agent bed, entraining a chemically active 

additive into the gas stream. 

E. Viability of New Suppression Technologies

1. The success of new NGP technologies requires (1) characterization of critical fire suppression 

parameters under real-scale weapons system fire scenarios to guide laboratory research and (2) 

demonstration that candidate fire suppression methods are quenching flames as they would under 

the threats experienced in the field. Meeting these needs entails improved instrumentation in the 

test articles owned by the Military Department laboratories. Making these measurements of 

concentrations of fuel, oxygen, the suppressant, and harmful combustion byproducts during and 

after the fire suppression process requires rapid data acquisition during a period of shock and 

vibration, high temperatures and rapidly changing flow patterns. 

a. NGP researchers have developed a time-resolved (10 ms), multi-point, fieldable, nearinfrared tunable diode laser-based sensor for measurement and detection of combustible 

mixtures of oxygen and hydrocarbon fuels during a fire suppression event as little as 250 

ms in duration. Detection of fuel and oxygen concentration is especially important after 

suppression in order to predict the possibility of reignition. 

b. Measurement of the distribution of the suppressant is essential to characterize the fire 

extinguishment process and for certification of a suppression system. Since there are 

likely to be a multiplicity of candidate agents, with potentially different capabilities of 

being monitored, the NGP has developed approaches based on two distinct principles: 

laser-induced breakdown spectroscopy and infrared absorption. 
19

c. Excessive generation of HF, a corrosive and toxic degradation product of any of the 

fluorinated fire suppressants (e.g., HFC-227ea and HFC-125), is a principal deterrent to 

the deployment of these agents. The first in situ, time-dependent measurements of the 

concentration of HF, its dissipation, and its amelioration by additives to the suppressant 

have now been recorded. 

d. Making these measurements requires a fiber optic probe system capable of operation 

at high temperatures. NGP scientists have designed a probe for use at temperatures up to 

1200 K in the presence of powder, smoke, and fine water mist. 

e. The NGP team has also developed a cell for use in measuring the high temperature (up 

to 1000 K) infrared properties of candidate suppressants. This information enables 

finding spectral lines for detection and developing calibration curves for the temperaturedependent sensitivity of the measurements. 

2. The NGP goal specifies that the new fire suppression technologies must also be economically 

feasible. There are many contributing factors to be considered when deciding how or whether to 

adopt a fire suppression system design. These include both objective cost factors and subjective 

value factors. Accordingly, the NGP is developing a methodology to quantify a fire suppression 

technology by its life cycle cost and to enable superimposing on this a subjective value system. 

The data gathering for and formation of the baseline (halon 1301) case has been completed, as 

has the structuring of the cost benefit analysis process. This provides a framework for evaluating 

a range of weapons systems, considering both financial and technical variables. 

F. Improved Fuel Tank Inertion

Research in this area has been limited. There are only two aircraft that currently use halon 1301 

to inert fuel task when entering combat, the F-16 and the F-117. The Air Force is seriously 

considering the use of CF3I for this application. Should this decision be positive, then alternative 

technologies for fuel tank inerting would not be an NGP task. Nonetheless, to be prepared, NGP 

staff are near completion of a small project to assess current status of alternate systems that had 

in prior decades shown promise for fuel tank inerting. 
20

V. Reformulation of the NGP

A. Focused Goal

In November 1999, in the wake of continuing disagreement over the appropriate level of 

funding, agreement was reached on a reduced-scale NGP. The new goal became: 

“Develop and demonstrate, by 2005, technology for economically feasible, 

environmentally acceptable and user-safe processes, techniques, and fluids that meet the 

operational requirements currently satisfied by halon 1301 systems in aircraft.” 

The planned funding was to be $20.2 M, of which $13.6 M had been allocated during FY1997-

2000. 

The focus on aircraft fire suppression emerged from discussions with representatives of the 

Military Services: 

• The aircraft safety and survivability engineering teams from all three Services stated 

that they have fire suppression needs for engine nacelles and dry bays that were not 

being addressed by S&T efforts outside the NGP. 

• The Army stated that it had solutions for both current and planned ground vehicles 

that needed only engineering (not research) for implementation. Thus they had not 

budgeted S&T funds for fire suppression research in FY2000. 

• The Navy stated that it had no current plans to retrofit current ships, that they release 

very little halon 1301, and that the DoD reserves will suffice. ONR had an 

approximately $1 M/year S&T program in water mist, their planned technology for 

forward fit. 

Thus, the revised NGP addresses the predominant fires that the military customers identify as 

most needing additional research: fires occurring in the aircraft dry bays and engine nacelles in 

both current and planned platforms. Research issues that arise in adapting fire suppression 

technologies for ground or sea platforms will need to be addressed by the responsible Military 

Department. 

The Air Force has transitioned the use of CF3I for fuel tank inerting to the F-16 Program Office, 

where engineering determinations of key properties are underway. The EPA has endorsed this 

chemical for this use. Thus, fuel tank inerting does not appear in the reduced NGP plan. It could 

be added if CF3I were to prove unacceptable. 

While the research is directed at solutions for aircraft, there are clear implications for other DoD 

applications. The technologies developed for dry bays would merit consideration for crew 

compartments, where the fires and suppression conditions are similar. Technologies of benefit in 

addressing the obstructed fires and spray fires in engine nacelles would also apply to machinery 

and storage spaces on ships. 
21

B. Technical Approach of the Revised Program

Because of the substantial technical accomplishments of the initial years, the NGP has a solid 

base from which to develop new fire suppression technology for weapons systems. By the final 

expenditure of FY2000 funds, the NGP will deliver the following: 

 understanding of how suppressant chemicals must interact with flames in order to be 

comparable to halon 1301 in quenching efficiency; 

 analysis of the world of useful chemicals, identification of the best places to look for 

alternative suppressants, and a first set of “best looks;” 

 a suite of screening tests and guidance for their use; and 

 a method for determining and comparing the life-cycle costs of new fire suppression 

technologies. 

These results complete NGP efforts under Thrust 2 (Fire Suppression Principles), Thrust 3 

(Technology testing Methodologies), and Thrust 1 (Risk Assessment and Selection Criteria). 

From that point forward, the NGP will be directed toward two targets. 

1. New Flame Suppression Chemicals 

This effort continues mainly under Research Element 4B (Evaluation of Highly Effective 

Suppressant Chemicals), encompassing fluid and solid candidates. Several families of 

chemicals have already been examined, e.g.: 

 Main group compounds 

 Iron-containing compounds 

 Non-chemically active compounds 

 Tropodegradable bromocarbons 

 Phosphorus-containing compounds 

In each case, some promising candidates have been identified. These will be screened 

further to establish legitimate options for further development. A second look at the last 

two families is also likely. 

In addition, a recent project has examined the full realm of chemical categories, 

identifying those areas that have been well-studied, those that show little promise of 

successful candidates, and those meriting fuller study. The last set includes: 

 Nitrogen-containing compounds (e.g., amines and nitrides) 

 Copper-, manganese- and tin-containing compounds 

 Iodine-containing compounds 
22

Research into each of these chemical families will identify trends in suppression 

effectiveness, toxicity, etc. using NGP screening methods and QSARs from prior work. 

The optimal candidates will be flagged for further development. 

The reduced funding level limits the extent to which individual chemicals can be 

pursued: 

 Extensive and costly testing for a full toxicological examination will not be 

performed. 

• A few real-scale tests will be conducted to demonstrate the reliability of the 

bench-scale results as a predictor of the success of agents, rather than full 

characterization of the performance all candidate agents 

2. Improved Suppressant Storage and Delivery

Building on results from Thrust 2, this focus continues work under Thrusts 5 (Viability of 

New Suppression Technologies) and 6 (Better Suppressant Delivery). During the early 

years of the NGP, the Navy and Air Force aircraft safety and survivability teams have 

demonstrated how changes in the flow properties and geometry of suppressant release 

can enhance the efficiency of suppression. Concurrently, NGP research has developed 

principles for the relationship between suppressant flow properties and the enhanced 

concentrations needed for the quenching of flames in cluttered spaces. The research has 

also shown the importance of the location (relative to the flame) where a suppressant 

fluid vaporizes. 

What remains, then, is the development of modeling of the interactions between the 

suppressant flow and the fire in cluttered spaces. This will serve as a guide for the 

selection of optimal dispensing conditions, nozzle locations, etc. for effective suppression 

of fires in the various engine nacelle and dry bay configurations. 

Further work will also develop new ways of positioning the suppressant and controlling 

its discharge properties, approaches complementary to the traditional pressurized fluid 

bottles. Combined, these will then constitute a set of source terms for the above models 

and offer flexibility and efficiency to the platform designer. 

Again, the reduced funding limits the extent to which concepts for efficient storage and 

delivery can be examined. 

• The NGP will perform a modest number of indicative real-scale experiments 

to demonstrate the effectiveness of the new distribution principles, rather than 

rigorously establishing the validity of the models. 

• These tests will mainly be monitored using video cameras. The 

instrumentation to establish model validity will not be developed or adapted. 

• These models and technologies will be turned over to the platform managers 

for optimization testing in their particular configurations. 
23

C. Additional Efforts 

Over the past 4 years, the NGP has solicited proposals for “outside the box” approaches to fire 

suppression under Research Element 4D, “New and More Effective Fire Suppression 

Technologies that are Presently Conceptual.” Some of these novel ideas have proven successful 

at broadening the NGP thinking. A modest continuation of these solicitations is possible. 

Much of the innovation in NGP projects has resulted from interactions among a large set of 

investigators in diverse but related aspects of fire suppression. The number of concurrent 

projects, which peaked at 23, will decrease to 12 in FY2001 and to about 5 in FY2002. The 

NGP will continue to co-sponsor and participate actively in the spring Halon Options Technical 

Working Conference. The NGP will broaden the participation in its autumn Annual Research 

Meeting, inviting past investigators and other experts. It is hoped that these two meetings will 

continue to broaden the perspective and stimulate the innovation of the NGP investigators. 
24

VI. Conclusion

The NGP has generated three types of products: 

• extensive new knowledge of fire suppression of the types of fires experienced in 

current Department of Defense weapons systems, 

• methods for screening new suppressants, and 

• a number of chemicals for further examination. 

Funding constraints have led to a focus of future research on fire suppression for aircraft: 

• new suppressant chemicals and 

• precepts for optimizing their delivery to the flames. 

A methodology for determining and comparing the life-cycle costs of new fire suppression 

technologies in aircraft is nearing completion. 

The prognosis for successfully meeting the revised NGP goal is excellent, given the technical 

infrastructure and cadre of experts advanced by the NGP. The Department of Defense will then 

need to set in place the programs to develop the new technologies for implementation in its fleet 

of aircraft.