Title of Invention

"A PROCESS FOR PREPARING MAGNESIUM BASED FUEL RICH PROPELLANT COMPOSITION"

Abstract

This invention relates to a process for preparing magnesium based fuel rich propellant composition comprising: 50-70% of Magnesium powder of particle size 50-200 µm, 5-30% of solid organic binder as herein described of particle size 150-250 µm, 20-30% of Sodium nitrate of particle size 50-250 µm, 1-2% of Graphite powder, wherein the process steps comprising of: i) mixing magnesium powder and solid organic binder in a planetary mixer at room temperature; ii) adding sodium nitrate and graphite powder to the said reacting mixture of step (i); iii) the mixture of step (ii) is pressure moulded to obtain the propellant.

Full Text

FIELD OF INVENTION This invention relates to a process for preparing magnesium based fuel rich propellant composition. BACKGROUND OF INVENTION Fuel rich propellants for air-breathing remjet systems exhibit very high specific impulse in comparison to the rockets using double base and composite propellants. This is because air-breathing ramjets give much higher fuel efficiency than the rockets as ramjets use atmospheric air for complete combustion. In view of their great potential for producing higher specific impulse (Isp 600-1000 s), they have found wide applications to produce sustained in the propulsion of tactical missiles. Magnesium based fuel rich propellants are known to be used in air-breathing ramjets due to their high heat potential and high combustion efficiency as compared to the hydrocarbon based fuel rich propellants. Fuel rich propellants based on other metals like boron, aluminium, beryllium etc. have several combustion problems and are not much preferred particularly for low air/fuel applications though they possess high heat potential. Magnesium based fuel rich propellant consists of magnesium as the main fuel, a solid organic binder (like anthracene, phenanthrene, naphthalene etc.) which also functions as a fuel and an oxidiser preferably sodium nitrate due to its high oxygen content. These prope11ants are made either by pressure moulding technique or by slurry casting method. Propellants made by slurry cast method using liquid binder give low burning rates and therefore not much preferred. Propellants made by pressure moulding technique though possess comparatively lower mechanical properties but provide high burning rates required for high fuel flow rate applications. The propulsion system with fuel rich propel1ant is required to deliver modulated fuel flow rate for high altitude application as an essential parameter since the availability of atmospheric air for complete combustion of the fuel diminishes with the increase of altitude. This system also needs fixed fuel percentage independent of its delivered rate to have constant air—to-fuel ratio to maintain stable performance throughout the operation. The required modulated fuel flow rate can be achieved either by having typical grain geometry or by using different burning rate compositions in the propellant. Achieving this with either of the methods is difficult because in the former case the propellant processed by pressure moulding technique has comparatively low mechanical strength to have any complicated grain design and in the latter case the use of different burning rate compositions would not meet the requirement of maintaining the constant fuel value of the propellant. However, the modulated fuel flow rate can be achieved through the modulated burning rate of the propellant maintaining its constant fuel value by selecting different particle size spectrum of the ingredients and using suitable process conditions. OBJECTS OF THE INVENTION An object of the present invention relates is to propose a magnesium based fuel rich propellants of a wide spectrum of burning rate with a constant fuel value to achieve modulated fuel flow rate of the propellant for higher altitude application. DESCRIPTION OF THE INVENTION According to this invention there is provided a process for preparing magnesium based fuel rich propellant composition comprising: 50-70% of Magnesium powder of particle size 50-200 ^m, 5-30% of solid organic binder as herein described of particle size 150-250 µm, 20-30% of Sodium nitrate of particle size 50-250 µm, 1-2% of Graphite powder, wherein the process steps comprising of : i) mixing magnesium powder and solid organic binder in a planetary mixer at room temperature; ii) adding sodium nitrate and graphite powder to the said reacting mixture of step (i); iii) the mixture of step (ii) is pressure moulded to obtain the propellant. In accordance with this invention, magnesium powder has a size of 50-200 µmm, binder has a size of 150-250 µm, and sodium nitrate has a size of 50-250 µmm. The fuel ingredients of the propellant namely magnesium powder (Mg) and solid organic binder of required particle sizes are mixed in a planetary mixer at room temperature. He oxidizer sodium nitrate (NaNO3) alognwith graphite are added and further mixed. The propellant composition is pressure moulded to a density of for example 1.6 g/cc using a remote. controlled hydraulic press and the propellant is inhibited with suitable resin. If required, magnesium powder is coated with the organic binder dissolved in suitable solvent to achieve low burning rates of the compositions. The preparation of the compositions and -~"~~ the propellant processing are carried out at 40—50% condition. Burning rate of the propellants is determined by static firing in a vented vessel. An understanding of the present invention can be obtained from the following examples. Burning rate spectrums varying from 23 to 56 mm/s in the pressure range 15 to 40 kg/cm with 554 binder and from 14 to 43 mm/s in the pressure range 10 to 30 kg/cm 2 with 10% binder have been achieved. Lower burning rates upto 5 mm/s were also obtained with the increased binder contents. 1. EXAMPLE-I (Table Removed) The burning rate and chamber pressure of the propellant achieved are given in Table-1 TABLE - 1 (Table Removed) EXAMPLE-II (Table Removed) The burning rate and chamber pressure of the propellant achieved are given in Table-2 TABLE - 2 (Table Removed) WE CLAIM; 1. A process for preparing magnesium based fuel rich propellant composition comprising: 50-70% of Magnesium powder of particle size 50-200 µm, 5-30% of solid organic binder as herein described of particle size 150-250 µm, 20-30% of Sodium nitrate of particle size 50-250 µm, 1-2% of Graphite powder, wherein the process steps comprising of : i) mixing magnesium powder and solid organic binder in a planetary mixer at room temperature; ii) adding sodium nitrate and graphite powder to the said reacting mixture of step (i); iii) the mixture of step (ii) is pressure moulded to obtain the propellant. 2. A process as claimed in claim 1 wherein the propellant processing is carried at 40-50% relative humidity. 3. A process for preparing magnesium based fuel rich propellant composition substantially as herein described and exemplified in the example.

Documents:

1311-del-1998-abstract.pdf

1311-del-1998-claims.pdf

1311-del-1998-correspondence-others.pdf

1311-del-1998-correspondence-po.pdf

1311-del-1998-description (complete).pdf

1311-del-1998-form-1.pdf

1311-del-1998-form-19.pdf

1311-del-1998-form-2.pdf

1311-del-1998-gpa.pdf

1311-del-1998-petition-138.pdf