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 | Glycidyl Azide Polymer-based Enhanced Energy LOVA Gun Propellant
Author : Sanghavi, R.R.;Kamale, P.J.;Shaikh, M.A.R.;Chakraborthy, T.K.;Asthana, S.N.;Singh, Amarjit
Source : Defence Science Journal ; Vol:56(3) ; 2006 ; pp 407-416
Subject : 662.3 Propellants
Keywords : Low vulnerable ammunition;LOVA;Glycidyl azide polymer;GAP;Gun propellant;Triacetin;Cellulose acetate;Energetic plasticiser;Force constant;Combustion characteristics;HFCI;Hot fragment conductive ignition
Abstract : In this study, cyclotrimethylene trinitramine propellants with triacetin (TA)-plasticised cellulose acetate (CA) and nitrocellulose (NC) combination as binders were evaluated for low vulnerable ammunition (LOVA). Triacetin was replaced by energetic plasticiser; glycidyl azide polymer (GAP) in increments to enhance the performance in terms of force constant . In addition to ballistics, parameters like vulnerability, mechanical and thermal properties of GAP-based propellants in comparison to those of TA-based propellants, were also determined. The study brings out that the incorporation of 2-6 per cent GAP in place of TA resulted in the enhancement of force constant by 22-70 J/g and improved overall combustion characteristics. DSC revealed that thermal decomposition of GAP-LOVA propellants evolved more energy than TA-LOVA propellants. GAP-based LOVA propellant similar to TA-plasticised LOVA propellant, was found superior to NQ propellant in vulnerability tests as well as in hot fragment conductive ignition (HFCI) studies. As regards mechanical properties, incorporation of GAP resulted in improved compression strength. |
| | Detonating Cord for Flux Compression Generation using Electrical Detonator No. 33
Author : Wagh, P.B.;Ingale, S.V.;Rav, A.S.;Kaushik, T.C.;Gupta, Satish C.;Asthana, S.N.;Wasnik, R.D.;Sohoni, R.B.;Adya, M.N.
Source : Defence Science Journal ; Vol:61(1) ; 2011 ; pp 19-24
Subject : 620.261 Explosives
Keywords : Electric detonators;Jitter;Exploding bridge wire detonators;Detonating cord;Synchronisation;Magnetic flux compression
Abstract : The paper highlights the use of electrical detonators for magnetic flux compression generator applications which requires synchronisation of two events with precise time delay of tens of ms and jitter within a few ms. These requirements are generally achieved by exploding bridge wire type detonators which are difficult to develop and are not commercially available. A technique has been developed using commercially available electrical detonator no. 33 to synchronise between peak of seed current in stator coil and detonation of explosive charge in armature. In present experiments, electrical signal generated by self-shorting pin due to bursting of electrical detonator has been used to trigger the capacitor discharge and the detonating cord of known length has been used to incorporate predetermined delay to synchronise the events. It has been demonstrated that using electrical detonator and known length of detonating cord, the two events can be synchronised with predetermined delay between 31 and 251 ms with variation of ± 0.5ms. The technique developed is suitable for defence applications like generation of high power microwaves using explosive driven magnetic flux compression generators. |
| | Thermal Behaviour of AP Based CMDB Propellants with Stabilizers
Author : Asthana, S.N.;Divekar, C.D.;Khare, R.R.
Source : Defence Science Journal ; Vol:42(3) ; 1992 ; pp 201-204
Subject : 66 Chemical Technology;662.3 Propellants
Keywords : Molecular sieve;Resorcinol based composition
Abstract : Stability test results and DTA studies indicate the superiority of molecular sieve (MS) over zirconium silicate (ZrSiO/sub 4/) as the stabilizer for a composite modified double base (CMDB) system. Shelf life as computed from autoignition test results was 30 years for MS-based composition which is almost double the life of ZrSiO/sub 4/, but approximately half the life of resorcinol-based composition which was used as a reference. Higher stabilizing effect of MS as compared to ZrSiO/sub 4/ has been explained on the basis of the presence of channels and cavities in its structure, which makes it an effective adsorbent for decomposition catalysing species. Poor stabilization capability of m-dinitrobenzene as compared to resorcinol suggests the catalytic involvement of acidic decomposition products of nitrate esters in autodecomposition process of CMDB propellants. |
| | Advances in High Energy Materials
Author : Nair, U.R.;Asthana, S.N.;Rao, A. Subhananda;Gandhe, B.R.
Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 137-151
Subject : 536 Thermodynamics;53 Applied Physics;Defence Science Journal
Keywords : HEMs;performance;insensitive;explosives;propellants;high energy materials;green energetic materials;trinitrotoluene;cyclotrimethylenetrinitramine
Abstract : Research and development efforts for realizing higher performance levels of high energy materials (HEMs) are continued unabated all over the globe. Of late, it is becoming increasingly necessary to ensure that such materials are also eco-friendly. This has provided thrust to research in the area of force multiplying HEMs and compounds free from pollution causing components. Enhancement of the performance necessitates introduction of strained structure or increase in oxygen balance to achieve near stoichiometry. The search for environment friendly molecules is focused on chlorine free propellant compositions and lead free primary explosives. Energetic polymers offer added advantage of partitioning of energy and thus not necessitating the concentration of only solid components (HEMs and metal fuels) in the formulations, to achieve higher performance, thereby leading to improvement in energetics without adversely affecting the processability and mechanical properties. During recent times, research in the area of insensitive explosives has received impetus particularly with the signature of STANAG. This paper gives a review of the all-round advances in the areas of HEMs encompassing oxidizers, high-energy dense materials, insensitive high-energy materials, polymers and plasticizers. Selected formulations based on these materials are also included. |
| | Combustion Behaviour of Advanced Solid Propellants
Author : Asthana, S.N.;Mundada, R.B.;Phawade, P.A.;Shrotri, P.G.
Source : Defence Science Journal ; Vol:43(3) ; 1993 ; pp 269-273
Subject : 662.3 Propellants;66 Chemical Technology
Keywords : Ammonium perchlorate;Propellants;Burning rates;Propellant combustion;AP based compositions
Abstract : The study reports the effect of incorporation of Al and ammonium perchlorate (AP) individually and in combination with each other on combustion pattern and specific impulse (Isp) of minimum signature propellants. Incorporation of Al obviates the combustion instability problems; however, it has marginal effect on burning rates. The composition containing AP and zirconium silicate combination gives superior performance; however, its Isp is considerably lower than the composition incorporating 9 per cent AP. A combination of 6 per cent Al gave 20 per cent enhancement in burning rate and 12 s increase in Isp as compared to purely nitramine-based composition, cal-val results also reveal increase in energy output on incorporating AP and Al. Hot stage microscopic and propellant combustion studies indicate occurrence of intense decomposition reaction in case of AP-based compositions. |
| | Polyurethane Based Inhibition for High Flame Temperature Nitramine Based Composite Modified Double Base propellant
Author : Asthana, S.N. ;Kadam, U.B.;Divekar, P.K.;Khangaonkar, D.G.;Vaidya, M.V.;Kakade, S.D.
Source : Defence Science Journal ; Vol:48(4) ; 1998 ; pp 371-377
Subject : 662.3 Propellants;66 Chemical Technology
Keywords : Inhibition systems ;Propellant inhibition bond strength
Abstract : The findings for polypropylene glycol (PPG) and hydroxyl-terminated polybutadiene (HTPB)-based inhibition systems are reported. These findings established that the inhibition system comprising HTPB-IPDI-IDP binder and Sb/sub 2/O/sub 3/-C black filler is most suitable for advanced nitramine-based composite modified double-base propellants in terms of mechanical properties and processibility. The promising composition was characterised for glass-transition behaviour and propellant-inhibition bond strength. Propellant grains inhibited with selected formulations were subjected to static evaluation at extreme temperatures and limited aging studies to obtain data of practical value. |
| | Impact Friction Shock Sensitivities and DDT Behaviour of Advanced CMDB Propellants
Author : Asthana, S.N.;Athawale, B.K.;Singh, Haridwar
Source : Defence Science Journal ; Vol:39(1) ; 1989 ; pp 99-107
Subject : 66 Chemical Technology;662.3 Propellants
Keywords : PETN based compositions;AP based compositions;Composite propellants
Abstract : This paper reports results of impact, friction and shock sensitivities of CMDB propellants containing AP, RDX, PETN and their combinations. Results of impact and friction sensitivities indicate that CMDB propellants containing AP are highly sensitive and AP-based compositions are more impact and friction sensitive than RDX and PETN-based compositions, and that these sensitivities are proportional to oxygen balance of the composition, which is in agreement with earlier findings. Inclusion of high explosives like RDX and PETN increases the shock sensitivity of CMDB formulations, whereas AP-based compositions are least shock sensitive. There exists a relationship between shock sensitivity and VOD of the individual oxidiser/high energy ingredient incorporated in the formulation. Shock amplitude values of 87 and 46 k bar in CMDB propellants are much more shock sensitive than DBP. Composite propellants are insensitive to shock, as they did not undergo detonation even at zero card gap. Results of DDT behaviour of CMDB propellants show that they are more prone to deflagration to detonation transition under adverse conditions. |
| | Influence of Various Process Parameters on Mechanical Properties and Ballistics of Nitramine-Based Advanced CMDB Propellants
Author : Asthana, S.N. ;Gore, S.R. ;Vaidya, M.V. ;Venkatesan, K. ;Shrotri, P.G.
Source : Defence Science Journal ; Vol:41(4) ; 1991 ; pp 357-362
Subject : 66 Chemical Technology;662.3 Propellants
Keywords : Tensile strength ;Burning rate ;Double base propellants
Abstract : This paper reports the influence of important process parameters, namely mixing time and batch size; on the mechanical properties and ballistics of nitramine-based advanced CMDB propellants. Considerable improvement to the tune of 67 per cent in tensile strength was observed at a mixing time increase of 60-135 min. Scaling up of batch size from 8 to 25 kg resulted in 30 per cent higher tensile strength. Recorded enhancement of burning rate was of the order of 8 per cent in both the sets of experiments. Ballistically modified composition revealed 11-12 per cent increase in burning rate at all the pressure ranges, on combined increase in mixing time (55 to 85 min) and batch size(5-17kg). These findings are in line with those reported for composite and ballistically modified double-base propellants. |
| | Metallised Fuel rich Propellants for Solid Rocket Ramjet: A Review
Author : Singh, Haridwar ;Asthana, S.N.;Athawale, B.K.
Source : Defence Science Journal ; Vol:44(4) ; 1994 ; pp 269-278
Subject : 662.3 Propellants;66 Chemical Technology
Keywords : Metal combustion ;Binders;Combustion;Oxides;Metallised propellants;Metallised fuel rich propellants
Abstract : This paper reviews the research work carried out in the field of metallised fuel-rich propellants (FRP). Limitations and merits of various potential metals (Al, Mg, B, Be, or Zr) as a component of FRP are discussed. The paper also includes a discussion on the combustion mechanism of metallised propellants, including problem areas and probable remedial measures. Zirconium and Ti appear to have potential to offer FRP with efficient combustion. Ideal performance is not achieved with current systems based on Al and B and further work is needed to develop FRP having all three desirable attributes, viz., ease of ignition, stable combustion and high specific impulse (I/sub sp/) in a single composition. |
| | Synthesis and characterisation of bis azido methyl oxetane and its polymer and copolymer with tetrahydrofuran
Author : Nair, J.K. ;Satpute, R.S. ;Polke, B.G. ;Mukundan, T. ;Asthana, S.N. ;Singh, Haridwar
Source : Defence Science Journal ; Vol:52(2) ; 2002 ; pp 147-156
Subject : 623.4 Armaments and Ballistics;623 Military Science and Engineering
Keywords : Explosives ;Armament ;Copolymers ;Tetrahydrofuran
Abstract : "Bis-azido methyl oxetane (BAMO) was synthesised from pentaerythritol in two steps. Pentaerythritol was chlorinated to yield a mixture of mono, di, tri and tetra chloro compounds. The trichloro compound on ring closure gives bis-chloro methyl oxetane (BCMO). It was reacted with sodium azide in aqueous medium to obtain BAMO. The latter was polymerised using BF3 etherate catalyst and 1,4-butanediol initiator. Similarly, the BAMO- THF copolymer was also synthesised. All the monomers and polymers were characterised by IR, 1H-NMR, 13C-NMR, and refractive index. The polymers were also characterised for molecular weight, hydroxyl value, etc. Thermal analysis showed that both polymers degrade exothermically with T max of 237 °C for poly BAMO and 241°C for BAMO- THF copolymer with activation energy of 39 kcal/mol and 40 kcal/mol, respectively. Explosive properties like impact and friction sensitivity of BAMO and the other polymers were also determined. " |
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