A European Co-Operative Programme for New Rocket Propellants

Transcription

1 ABSTRACT Yves Longevialle SNPE Propulsion Le Bouchet VERT LE PETIT FRANCE New energetic raw materials (polymers: GAP, PNMMO, PGLYN; oxidisers: ADN, CL20, ) are available to formulate rocket propellants. They can lead to a better answer than current propellants to requirements of future tactical missiles. An European co-operative programme, sharing the work among 12 industrial entities from 8 nations (France: SNPE Italy: FIAT AVIO Norway: NAMMO Raufoss Portugal: LEDAP The Netherlands: APP, TNO Turkey: TUBITAK SAGE, MKEK ELROKSAN, ROKETSAN U.K.: RO Defence, Nobel Explosives ICI) has been initiated to assess different propellant candidates using these energetic materials. After a full characterisation of the new energetic raw materials, formulations works have been carried out on a large range of compositions. At the end of the programme, new families of rocket propellants are available and their main characteristics (i.e. processability, ballistics, mechanical properties, safety) have been assessed. They will offer a basis and various alternatives for future rocket motors development. 1.0 INTRODUCTION The operational trends for future tactical missiles are to improve performances (such as specific impulse, burning rate, operational temperature range), safety (insensitive munitions requirements) and cost, in conjunction with a reduction of plume signature. Together with the recent need to comply with environmental aspects, it appears that these requirements can not be met by current double base or composite propellants. New energetic raw materials (polymers: GAP, PNMMO, PGLYN; oxidisers: ADN, CL20, ) are available to formulate rocket propellants. They can lead to a better answer than current propellants to above mentioned requirements [1,2,3,4,5,6,7]. The EUCLID Research and Technology Program Clean Rocket Propellants addresses, tailors and assesses different propellant candidates using these energetic materials. This paper presents the works performed during this five years program from characterisation of raw materials, to formulation of propellants and manufacture of small motors for performance evaluation. 2.0 RESEARCH AND TECHNOLOGY PROJECT STRUCTURE The works have been shared among 12 Industrial Entities (SNPE, FIAT AVIO, NAMMO Raufoss, LEDAP, UEE, APP, TNO, TUBITAK SAGE, MKEK ELROKSAN, ROKETSAN, RO Defence, Nobel Explosives ICI) from 8 Nations (France, Italy, Norway, Portugal, Spain, The Netherlands, Turkey, United Kingdom.) within a Consortium led by SNPE. Paper presented at the RTO AVT Specialists Meeting on Advances in Rocket Performance Life and Disposal, held in Aalborg, Denmark, September 2002, and published in RTO-MP-091. RTO-MP

2 The breakdown of the works is presented below in the tables 1 and 2. Table 1: Characterisation of Raw Materials Nations F I No Po Sp NL Tr UK Industrial Entities SNPE FIAT AVIO NAMMO LEDAP UEE APP TNO TUBITAK SAGE MKEK ELROKSAN RO Defence Nobel Explosives ICI ADN x x x x x x x x x CL20 x x x GAP x x x x x PNMMO x x PGLYN x x x Table 2: Propellant Families Studies Nations F I No Po Sp NL Tr UK Industrial Entities SNPE FIAT AVIO NAMMO LEDAP UEE APP TNO TUBITAK SAGE MKEK ELROKSAN ROKETSAN RO Defence Nobel Explosives ICI ADN x x x x x x x CL20 x x x PNMMO/ x x x PGLYN/ x x x PNMMO/ADN x x x DNAM x The management of the programme is led by French MOD (DGA/DSA/SPNuc/ST/PES), with contribution of the M.o.D. s of the 7 others Nations. 3-2 RTO-MP-091

3 3.0 TECHNICAL RESULTS 3.1 Novel Energetic Materials New energetic materials available for rocket propellant formulations works have been considered. They proceed from the azido or nitro types. Three polymers (GAP, PNMMO, PGLYN) and three oxidisers (CL20, ADN, ) have been considered as potential major components of new compositions and fully characterised Oxidisers Different sources of the 3 studied fillers have been supplied and characterised: ADN or Ammonium DiNitramide : SNPE, Bofors or Hydrazinium NitroFormate : APP CL20 or Hexanitro hexaaza isowurtzitane : SNPE, Thiokol The three new energetic fillers are produced at lab pilot scale (tens of kg) for the first two or industrial pilot scale (hundreds of kg) for CL20. While both CL20 and are available in a range of particle sizes, ADN is not yet well specified. CL20 has a compact shape, which is positive to process well, while and ADN have tendency to crystallise with needle shape. If particle shape of has been lightly improved during the program, rounded ADN is not yet commercially available. Crystallisation and/or prilling processes are studied in different companies [8,9,10,11]. The availability of these improved raw materials has been identified as an important need. The analysis of the fillers have shown high purity, and confirmed density between 1.8 (ADN) and 2.04 (CL20). CL20 is of similar thermal stability to traditional energetic fillers while the stability of ADN (but for temperature above 80 C) and particularly is poorer at this stage in their development, but not such as to preclude their use in propellant research. The hygroscopicity of ADN requires particular caution for storage and handling. All the studied materials show a wide range of impact sensitiveness depending on the grades and test centres. All have sensitiveness to impact. In general was the most sensitive to friction with ADN the least. None of the materials, in the grades tested, showed susceptibility to ESD. Each of the materials, although sensitive to impact and friction, are considered acceptable for processing with appropriate precautions. CL20 shows no compatibility problems with the propellant ingredients to be used in the program. The reactive nature of both ADN and leads to chemical incompatibilities with some isocyanates. Other incompatibilities with potential ingredients have been observed with. RTO-MP

4 Table 3: Fillers Main Characteristics Characteristics (*) ADN CL20 Oxygen balance (O 2 /CO 2 +H 2 O) % Enthalpy of formation (kj/mole) Density Particle size/shape µm /needle shape µm /needle shape 3-170µm /compact Safety Sensitiveness to impact and friction Not sensitive to ESD Thermal stability (V.T.S.) (200h-80 C) (48h-60 C) <1 (200h-80 C) Compatibility Incompatibilities with some isocyanates Incompatibilities with some isocyanates and others potentials ingredients No major problems * Range taking into account results obtained in the field of the programme including different grades and analytical techniques Polymers The three main new energetic polymers available at commercial scale have been considered: GAP (Glycidyl Azide Polymer) PNMMO (Poly Nitrato Methyl Methyl Oxetane) PGLYN (Poly Glycidyl Nitrate) : SNPE, 3M : Nobel Explosives ICI : Nobel Explosives ICI GAP is produced at industrial pilot scale (hundreds of kg), while PNMMO and PGLYN are synthesised at pilot scale (ten or so kg). Both GAP and PNIMMO are available as di and tri functional materials, which gives a useful tool to monitor binder properties. PGLYN on the other hand is only available in a trifunctional form. All three pre polymers have lower molecular weight than current pre polymers such as HTPB, but exhibit higher viscosity and density in connection with their chemical structure. The molecular weights (Mn) of standard GAP and PNMMO diols are slightly below The tri functional grades have Mn around 1000 and 2000 for GAP, 1500 for PGLYN and 1800 for PNMMO. Glass transition temperature range of GAP is around -40/-50 C, while Tg s in higher range are noticed for the nitropolymers: -20 C/-30 C. Tg s in the range of -30 to -40 C are easily achievable for each of the polymers when plasticised. Adaptation of nature and content of plasticisers has led to Tg as low as -50/-60 C (respectively for PGLYN / NENA plasticiser and TMETN/BTTN). All the three pre polymers show no significant problems in safety and are of acceptable stability [12]. 3-4 RTO-MP-091

5 With the exception of reactivity of PGLYN with and ADN attributed to the presence of the 1,2 diol within the polymer terminal group, generally the pre polymers show good compatibility with the considered propellant ingredients. Table 4: Polymers Main Characteristics Characteristics GAP PNMMO PGLYN Enthalpy of formation(kj/kg) Density Molecular weight Diol Mn ~1700( ->2600) Mw ~1800(->2900) Triol long Mn ~2000 Mw ~2400 Triol short Mn ~970 Mw ~1060 Diol Mn ~1900 Mw ~3200 Triol Mn ~1800 Mw ~2600 Triol Mn ~1100 (->1500) Mw ~1700(->3000) Glass transition ( C) -41/-53 C -22 C -18/-31 C Safety No significant problem to impact, friction, ESD. Acceptable thermal stability. Compatibility Good compatibility with main propellants ingredients Good compatibility with main propellants ingredients Incompatibilities with ADN and (-> High molecular weight grades) 3.2 New Propellant Families Propellants Considered Seven combinations of new raw materials have been taken into account for propellant formulation works (Table 2). While GAP was tested with all the potential fillers (ADN, CL20, and DNAM or DiNitroAminoMelamine), PNMMO was only tested with two (ADN and ) and PGLYN with Signature Low signature been a requirement of the program, all the propellants have been formulated to be classified in AA from thermodynamic calculations and according to STANAG Theoretical Performances With exception of DNAM filled composition (for which, as a consequence, only limited works have been performed), high theoretical specific and volumetric impulses are achievable with these potential RTO-MP

6 propellant formulations. At the optimum filler levels, theoretical specific impulses in the range 240 to 280s are produced, with loaded systems giving the highest computed values. Taking into account actual limitations for processability, mechanical properties or other characteristics, formulations with reasonable filler levels were achieved. The ones produced up to pilot scale have theoretical specific impulse from 246 up to 262s for ADN. The volumetric impulse range is in the range sg/cm3 with the highest values achieved by CL20 and ADN propellants; the similar figures obtained for these 2 propellants are a result of the antagonist effect of the difference of density of the fillers and of the nature of the plasticisers used (BDNPA/F and TMETN/BTTN). For missiles applications where very high impulse is required but some sacrifice in smoke signature could be tolerated, the addition of fuels could be usefully considered Processability The works performed show good castability and processability with CL20 in combination with GAP. Compact shape and adapted range of particle sizes of this oxidiser, on one hand, and good binder-filler compatibility, on the other hand, lead probably to this behaviour. Due to non-optimised filler morphology and non-availability of different range of particle sizes, both high solids loading and ADN compositions will need improvement of processability. In order to optimise actual characteristics of processability and furthermore mechanical properties, limited content of these new oxidisers (around 50-55%) and addition of a low content of current nitramine (10-15% of HMX or RDX) have been used. Limitations of processability and/or chemical incompatibilities have led to a cessation of work on and PGLYN/ at the end of the first stage of the programme, leading to obtain only partial and limited characterisation. Reasonable filler levels (around 60-70%) were achieved with all the fillers and binders combinations studied at pilot scale (some kg). These compositions have been assessed by casting successfully ballistic test motors (2-3 5) or around 1 kg samples Mechanical Properties Tgs of at least -25 C were determined for all classes of compositions considered. Tgs depend on Tg of polymers and plasticisers and their ratio, so the lower glass temperature is reached using TMETN/BTTN binders. Propellant ADN CL20 DNAM PNMMO/ PNMMO/ ADN PGLYN/ Tg range ( C) # -58 # -45 # to to to -43 # -28 Mechanical properties at low temperature are strongly connected with these glass temperatures. 3-6 RTO-MP-091

7 Mechanical Properties (tensile test- 50mm/mn) ADN CL20 PNMMO/ PNMMO/ADN +60 C Sm (MPa) C Sm (MPa) E (MPa) em (%) Low T re em (%) (-54 C) 4 (-30 C) 39 (-25 C) 3 (-40 C) Ballistics The ballistics of propellant families have been measured using the Crawford bomb or small motor firings. Depending of the families, a large range of burning rates is covered. Burning rates of between 9 and 33 mm/s at 7 MPa were obtained. For example, some CL20/GAP formulations showed burning rates as low as 9 mm/s and ADN/GAP and ADN/PNMMO the highest burning rates, /PNMMO being around of 18 mm/s. Propellant ADN CL20 DNAM PNMMO/ PNMMO/ ADN PGLYN/ Rb (mm/s) at 7 MPa > Even if, with some formulations within ADN, CL20, and PNMMO/ADN propellant families, pressure exponent around 0.5 have been obtained, generally the pressure exponents for the propellants are high and need to be reduced to permit them to be used in many motors applications Safety Vulnerability The sensitiveness data (friction and impact) remain in a range that can be managed based on experiences with current propellants. Limited vulnerability tests have been performed in the duration of the RTP, and only using 2 families of propellants, however encouraging results have been obtained: Small analogs filled with PNNMO/ have been tested, showing only combustion reactions and the same behaviour as HTPB propellants for the tests performed (S.C.O., F.C.O., Bullet Impact). Good results have been obtained for PNMMO/ADN at SCO (combustion), Shot Gun (Critical.Impact.Velocity. > 200m/s) and High Velocity Shot Gun Tests (C.I.V. > 600 m/s) performed at laboratory scale Ageing The results from vacuum stability tests indicate an increase of stability in the order: Least stable [PNMMO/ < PNMMO/ADN # ADN < CL20] Most stable and that the propellants are sufficiently stable for continued research. RTO-MP

8 Only preliminary ageing tests have been performed on PNMMO/, PNMMO/ADN and ADN propellants. No strong deterioration has been detected, however a more complete evaluation of ageing has to be done. It will be necessary to take into account the humidity sensitivity of ADN propellants. 4.0 CONCLUSIONS The combined effort of the 12 Industrial Entities involved in EUCLID Research and Technology Program Clean Rocket Propellants has led to: A detailed physical, chemical and safety characterisation of the novel energetic raw materials available for formulation of propellants (polymers: GAP, PNMMO, PGLYN; oxidisers: ADN, CL20, ). A study of a large range of propellants compositions using these novel energetic raw materials (ADN, PNMMO/ADN, CL20, PNMMO/, PGLYN/,, DNAM propellants). After preliminary works, the first four propellant families have been selected and assessed up to pilot scale. They lead to energetic performances higher than current double base formulations and in the range of conventional HTPB/AP propellants with advantage in term of signature and environmental aspects. Burning rates cover a wide range from around 9 to 30mm/s at 7MPa. Tests performed in the different companies have shown acceptable safety characteristics. Only limited vulnerability tests have been performed in the duration of the programme, however encouraging results have been obtained. At the end of the programme, the main goals of the RTP have been achieved. The results obtained constitute a demonstration of the viability of using novel energetic materials in propellants. New families of rocket propellants are available to be considered as a basis for future rocket motors developments for which they offer various alternatives. However complementary works are necessary before these propellants can be incorporated in full scale motors development, including tuning of combustion properties, adaptation of mechanical properties, extension of safety, IM and ageing tests, and cost/ performances balance analysis. The EUCLID co-operation Clean Rocket Propellants has been regarded as very fruitful by all the Industrial Entities within the sharing of effort and knowledge in the field of novel energetic raw materials and new rocket propellants. 5.0 ACKNOWLEDGEMENTS Points of Contact of the Industrial Entities: FIAT AVIO: APP: TNO: NAMMO RAUFOSS: LEDAP: UEE: TUBITAK SAGE: MKEK ELROKSAN: ROKETSAN: RO Defence: Nobel Explosives ICI: Francesca LILLO Williane WELLAND-VELTMANS Jos MUL Johanne HUSDAL Eurico CORTEZ DE ALMEIDA José A.SANCHIDRIAN Fikret PEKEL Didem KOKDEN Selma SIMSEK Douglas WAGSTAFF Eric MARSHALL 3-8 RTO-MP-091

9 National Representatives: FRANCE: ITALY: THE NETHERLANDS: NORWAY: PORTUGAL: SPAIN: TURKEY: The United Kingdom of Great Britain and Northern Ireland: DGA/DSA/SPNuc/ST/PES DGAT Officio Coordinamento Technico LBBKL Munitie Betrijf FFI (Norwegian Defence Research Establishment) LEDAP Laboratorio Quimico Central de Armamento MSB/ARGE ve Tekno D DSTL 6.0 REFERENCES [1] Demay, S., and al., Use of New Oxidisers and Binders to Meet Clean Air Requirements Propulsion and Energetics Panel Aalesund, Norway, August 29 September 2, [2] Chan and al., Minimum Signature Propellant with Mixed Oxidiser Concept RTO/AVT Symposium Corfu, Greece April 19-23, [3] Schoyer, H. and al. Overview of the Development of Hydrazinium Nitroformate-Based propellants Journal of Propulsion and Power Vol.18, N 1, January-February 2002 p [4] Pak, Z., Some Ways to Higher Environmental Safety of Solid Rocket Propellant Application AIAA , Monterey, CA, USA, June [5] D Andrea and al., A New Generation of Solid Propellants for Space Launchers IAF 99 S [6] Longevialle and al., New Generation of Propellants for High Performances Solid Rocket Motors RTO/AVT Symposium Corfu, Greece April 19-23, [7] Coleno, R., Nugeyre, J.C., Longevialle, Y., Lassus, B., Demonstrators for Insensitive Tactical Rocket Motors IMEMTS Symposium Bordeaux France - October 8-11, [8] Veltmans, W. and al, The Effect of Different Cristallisation Techniques on Morphology and Stability of ICT 31st International Annual Conference June [9] Teipel and al., Cristallization of Spherical Ammonium Dinitramide (ADN) Particles, Propellants, Explosives, Pyrotechnics 25, (2000). [10] Johansson and al., Production of Prills of Ammonium Dinitramide for Use in Explosives Patent WO 99/ [11] Highsmith, Th. and al., Thermally-Stabilized Prilled Ammonium Dinitramide Particles, and Process for Making the Same Patent WO 99/ [12] Paul, N. and al., An Improved PolyGLYN Binder through End Group Modification ADPA Symposium September 1995 Phoenix, AZ, USA. RTO-MP

10 Discusser s Name: Klause Menke SYMPOSIA DISCUSSION PAPER NO: 3 Question: 1) What is the reason for the incompatibility between POLYGLYN and ADN or? 2) What are the pressure exponents and temperature coefficients of ADN and formulations? Author s Name: Yves Longevialle Author s Response: 1) The compatibility between POLYGLYN and ADN or has been identified in the UK, outside this program, as the link with the 1,2 diol termination of the polymer. 2) Pressure exponents around 0.5 have been obtained in some cases with ADN (and CL-20) propellants. In general, however, further work will have to be done to improve pressure exponents of all the propellants families studied. When determined, temperature coefficients of around or below 0.3% have been measured. Discusser s Name: Ron Derr Question: Will there be a follow-on program to the Euclid Program, Clean Rocket Propellants? If so, will the follow-on program address the improvements of raw materials such as and ADN? Author s Name: Yves Longevialle Author s Response: Different works are performed inside various companies to improve raw material. In addition, a new Euclid research and technology program is planned in the near future. It will take into account the improvements of some of the raw materials considered in this and other programs. Discusser s Name: Hans Besser Question: What was the design of the small analog motors used in safety testing? What is the confidence for extrapolate results to full-scale motors? Author s Name: Yves Longevialle Author s Response: Small analog motors used in vulnerability tests were 2-inches in diameter with metallic cases. Encouraging results have been obtained in these preliminary tests with no violent events. However, it will be necessary to perform tests at larger scale and in different configurations to obtain information in a broader range before full-scale motors are developed and tested. Discusser s Name: Luigi DeLuca Question: Did you try to assess the combustion stability characteristics of your formulations? If so, how did you do this and what were the results? Author s Name: Yves Longevialle Author s Response: In some firing test conditions, using radial burning test motors, combustion instabilities have been noticed. This area has been identified as one of the fields of complementary work to be performed before the use of these new propellants in rocket motors developments RTO-MP-091