Solid propellant for missile

By Armando Mateo

Early development of explosive

The first breakthrough in making a truly workable smokeless powder came in France in 1886. Paul Vieille found ways to nitrate cotton so that it was possible to dissolve it in solvents which led to gelatinized masses of nitrocellulose that could be formed into gunpowder grains.

In 1887, Alfred Nobel patented Ballistite, based on Nitrocellulose plasticized by nitroglycerine under a process similar to the cellulose process invented by J. W. Hyatt in 1870. It was a first step in the direction of extruded double-base(EDB) propellant grains.

Development of solid propellant

Solid propellant rockets

Solid propellant motors are the simplest of all rocket designs. They consist of a casing, usually steel, filled with a mixture of solid compounds (fuel and oxidizer) which burn at a rapid rate, expelling hot gases from a nozzle to produce thrust. When ignited, a solid propellant burns from the center out towards the sides of the casing. The shape of the center channel determines the rate and pattern of the burn, thus providing a means to control thrust. Unlike liquid propellant engines, solid propellant motors can not be shut down. Once ignited, they will burn until all the propellant is exhausted.

Composite propellants

The two most common binders are polybutadiene acrylic acid acrylonitrile (PBAN) and hydroxy-terminator polybutadiene (HTPB). PBAN formulations give a slightly higher specific impulse, density, and burn rate than equivalent formulations using HTPB. However, PBAN propellant is the more difficult to mix and process and requires an elevated curing temperature. HTPB binder is stronger and more flexible than PBAN binder.

Component diagram of solid propellants

Basic composition of solid propellants

Oxidizer Fuel Binder CatalystPlasticizerEpoxy curing agent

Terminologies

CDB –cast double base propellantEDB – Ejected double base propellantXLDB- Cross-linked double base propellantECMDB-Elastomeric Modified Cast double basePBAA- Polybutadiene Acrylic AcidPBAN-Polybutadiene AcrylnitrileCTPB- Carboxyl Terminated Polybutadiene

Effect of binder on propellants

Chemical Composition of solid propellantsAmmonium Perchlorate (AP) (200-Micron Particle Size) 35Ammonium Perchlorate (AP) (50-80 Micron Particle Size) 35Aluminum Powder (< 200 Micron particle Size) 14Hydroxy Terminated Poly Butadiene (HTPB) 11-12Dioctyl Azelate (DOZ) - or - Dioctyl Adepate (DOA) 3.5Ferric Oxide 12,4-Toluene Diisocyanate (TDI) ~1Tri[1-(2-Methyl Aziridinyl)] Phosphine Oxide (MAPO) 0.3

C-4 explosive

High-Energy Propellants

NEPE75-polyoxyethylene glycol-255 sec Specific Impulse

XLDB- 250 sec Specific Impulse

The chemistry of propellants

Explosive is sudden release of energy in the forms of shock waves, sound and heat damaging the container.

Propellant is sudden release of energy in the form of shockwaves, sound and heat without damaging its container.

Both are same on the sudden expansion of gas products.

When 2 moles of hydrogen react with 1 moles of oxygen it sudden release of energy of about 13,260 joules per gram.

Roger Bacon Black powder composition(1214)

Later composition improvements to adjust reaction quantity

Explosive chemical formula

Performance parameters

Heat of explosion

Ammonium Nitrates is oxygen excess and TNT is oxygen deficient.

Burning- Piobert’s Law

Vielle’s Law 1893

Gun propellant grain geometry

Extruded double base propellants

Polymer composite