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Higher-performance solid rocket propellants are used in large strategic missiles (as opposed to commercial launch vehicles). HMX, C4H8N4(NO2)4, a nitramine with greater energy than ammonium perchlorate, is the main ingredient in NEPE-75 propellant used in the Trident II D-5 Fleet Ballistic Missile.[12] It is because of explosive hazard that the higher energy military solid propellants are not used in commercial launch vehicles except when the LV is an adapted ballistic missile already containing HMX propellant (example: Minotaur IV and V based on retired Peacekeeper ICBMs).[13] The Naval Air Weapons Station at China Lake, CA developed a new compound, C6H6N6(NO2)6, called simply CL-20 (China Lake compound #20). Compared to HMX, CL-20 has 14% more energy per mass, 20% more energy per volume, and a higher oxygen-to-fuel ratio.[14] One of the motivations for development of these very high energy density military solid propellants is to achieve mid-course exo-atmospheric ABM capability from missiles small enough to fit in existing ship-based below-deck vertical launch tubes and air-mobile truck-mounted launch tubes. CL-20 propellant compliant with Congress' 2004 insensitive munitions (IM) law has been demonstrated and may, as its cost comes down, be suitable for use in commercial launch vehicles, with a very significant increase in performance compared with the currently favored APCP solid propellants.
An attractive attribute for military use is the ability for solid rocket propellant to remain loaded in the rocket for long durations and then be reliably launched at a moment's notice.
[edit]Propellant families
[edit]Black Powder (BP) Propellants
Composed of charcoal (fuel), potassium nitrate (oxidizer), and sulfur (additive), black powder is one of the oldest pyrotechnic compositions with application to rocketry. In modern times, black powder finds use in low-power model rockets (such as Estes and Quest rockets), as it is cheap and fairly easy to produce. The fuel grain is typically a mixture of pressed fine powder (into a solid, hard slug), with a burn rate that is highly dependent upon exact composition and operating conditions. Due to its sensitivity to fracture (and, therefore, catastrophic failure upon ignition) and poor performance (specific impulse around 80 s), BP does not typically find use in motors above 40 Ns.
[edit]Zinc-Sulfur (ZnS) Propellants
Composed of powdered zinc metal as the fuel and powdered sulfur as the oxidizer, ZnS or "micrograin" has no practical application outside of specialized amateur rocketry circles due to its poor performance (as most ZnS burns outside the combustion chamber) and incredibly fast linear burn rates on the order of 2 m/s. ZnS is most often employed as a novelty propellant as the rocket accelerates extremely quickly, leaving a spectacular large orange fireball and smoke trail behind it.
[edit]"Candy" propellants
In general, candy propellants contain an oxidizer (typically potassium nitrate) and a sugar or similar compound (typically dextrose, sorbitol, or sucrose)as fuel and binder. These propellants are usually cast into shape by gently melting the propellant constituents together and pouring or packing the amorphous mixture into a mold. Candy propellants generate a specific impulse of only ~130 s and, thus, are of interest only by amateur and experimental rocketeers.
[edit]Double-Base (DB) Propellants
DB propellants are composed of two monopropellant fuel components where one typically acts as a high-energy (yet unstable) monopropellant and the other acts as a lower-energy stabilizing (and gelling) monopropellant. In typical circumstances, nitroglycerin is dissolved in a nitrocellulose gel and solidified with additives. DB propellants are implemented in applications where minimal smoke is required yet medium-high performance (Isp of roughly 235 s) is required. The addition of metal fuels (such as aluminum) can increase the performance (around 250 s), though metal oxide nucleation in the exhaust can turn the smoke opaque.
[edit]Composite propellants
A powdered oxidizer and powdered metal fuel are intimately mixed and immobilized with an elastomeric binder (that also acts as a fuel). Composite propellants are often either ammonium nitrate-based (ANCP) or ammonium perchlorate-based (APCP). Ammonium nitrate composite propellant often uses magnesium and/or aluminum as fuel and delivers medium performance (Isp of about 210 s) whereas Ammonium Perchlorate Composite Propellant often uses aluminum fuel and delivers high performance (vacuum Isp up to 296 s with a single piece nozzle or 304 s with a high area ratio telescoping nozzle).[8] Composite propellants are cast, and retain their shape after the rubber binder, such as Hydroxyl-terminated polybutadiene (HTPB), cross-links (solidifies) from addition of a curing agent. Because of its high performance, moderate ease of manufacturing, and moderate cost, APCP finds widespread use in space rockets, military rockets, and hobby and amateur rockets, whereas cheaper and less efficient ANCP finds use in amateur rocketry and gas generators. Ammonium dinitramide, NH4N(NO2)2, is being considered as a 1-to-1 chlorine-free substitute for ammonium perchlorate in composite propellants. Unlike ammonium nitrate, ADN can be substituted for AP without a loss in motor performance.
In 2009, a group succeeded in creating a propellant containing water as the oxidizer and nanoaluminum as the fuel (ALICE).
The Constellation program used a mix of aluminum, ammonium perchlorate, a polymer of polybutadiene and acrylonitrile, epoxy and iron oxide.[15]
[edit]High-Energy Composite (HEC) propellants
Typical HEC propellants start with a standard composite propellant mixture (such as APCP) and add a high-energy explosive to the mix. This extra component usually is in the form of small crystals of RDX or HMX, both of which have higher energy than ammonium perchlorate. Despite a modest increase in specific impulse, implementation is limited due to the increased hazards of the high-explosive additives.
[edit]Composite Modified Double Base propellants
Composite modified double base propellants start with a nitrocellulose/nitroglycerin double base propellant as a binder and add solids (typically ammonium perchlorate and powdered aluminum) normally used in composite propellants. The ammonium perchlorate makes up the oxygen deficit introduced by using nitrocellulose, improving the overall specific impulse. The aluminum also improves specific impulse as well as combustion stability. High performing propellants such as NEPE-75 used in Trident II D-5, replace most of the AP with HMX, further increasing specific impulse. The mixing of composite and double base propellant ingredients has become so common as to blur the functional definition of double base propellants.
[edit]Minimum-signature (smokeless) propellants
One of the most active areas of solid propellant research is the development of high-energy, minimum-signature propellant using CL-20 (China Lake compound #20), C6H6N6(NO2)6, which has 14% higher energy per mass and 20% higher energy density than HMX. The new propellant has been successfully developed and tested in tactical rocket motors. The propellant is non-polluting: acid free, solid particulates free, and lead free. It is also smoke free and has only a faint shock diamond pattern that is visible in the otherwise transparent exhaust. Without the bright flame and dense smoke trail produced by the burning of aluminized propellants, these smokeless propellants all but eliminate the risk of giving away the positions from which the missiles are fired. The new CL-20 propellant is shock-insensitive (hazard class 1.3) as opposed to current HMX smokeless propellants which are highly detonable (hazard class 1.1). CL-20 is considered a major breakthrough in solid rocket propellant technology but has yet to see widespread use because costs remain high.[14]
http://www.google.co.in/url?sa=t&rc...J6MU4Th9uW3INt-dg&sig2=rN9OJGeKBT77azAATAWK_g
the 1st paragraph is important. after reading this i am thinking that DRDO has invented a new high performance solid propellant for A 5.
