Smoke propellant

AP composite propellants without aluminum particles are termed reduced-smoke propellants and are employed in tactical missiles to conceal their launch site and flight trajectory. No visible smoke is formed when the relative humidity of the atmosphere is less than about 40%. However, since high-frequency combustion oscillation tends to occur in the combustion chamber in the absence of solid particles that serve to absorb the oscillatory energy, a mass fraction of 0.01-0.05 of metallic particles is still required for the reduced-smoke propellants. These particles and/or their oxide particles generate thin smoke trails. The white smoke trail includes the white fog generated by the HCl molecules and the condensed water vapor of the humid atmosphere. 

Thus, AP is a valuable oxidizer for formulating smokeless propellants or smokeless gas generators. However, since the combustion products of AP composite propellants contain a relatively high concentration of hydrogen chloride (HCI), white smoke is generated when they are expelled from an exhaust nozzle into a humid atmosphere. When the HCI molecules diffuse into the air and collide with H2O molecules therein, an acid mist is formed which gives rise to visible white smoke. Typical examples are AP composite propellants used in rocket motors. Based on experimental observations, white smoke is formed when the relative humidity exceeds about 40 %. Thus, AP composite propellants without any metal particles are termed reduced-smoke propellants. On the other hand, a white smoke trail is always seen from the exhaust of a rocket projectile assisted by an aluminized AP composite propellant under any atmospheric conditions. Thus, aluminized AP composite propellants are termed smoke propellants. 

There were 1) Smoke Propellants (or Nonsmoke less Propellants), called Yuenyaku, which were Black Powder called Kokushokuyaku (Ref 1, p 27) and Brown Powder called Kassho-kuyaku (Ref 1, p 30). They are described here under K s and 2) Smokeless Propellants of general term Muenkayaku or Muenyaku. 

Flynn, S., Fossey, D.R., Catton, D.G., and Wagstaff, D. (1998) Evaluation of poly(NiMMO) in reduced smoke propellants. Proc. 29th Inti Ann. Conf. ICT, Karlsruhe, Germany, June 30-July 03,1998, Paper 42. 

Reduced Smoke. Propellants without metals or primary smoke, but containing oxidizers such as AP which gives HC1 gas as a principal combustion product, are called reduced smoke propellants. If HC1 is exhausted in atmospheres of high or moderate humidity, water droplets will coalesce about the HC1 molecules, resulting in a visible exhaust trail of what is called secondary smoke. In atmospheres of low humidity, the exhaust plume of reduced smoke propellants is not visible. 

Minimum Smoke. Propellants with no metals, and having exhaust free of nucleating species such as HC1, are termed minimum smoke propellants. 

The addition of AP particles within AN-PU propellants increases the burning rate and reduces the pressure exponent without catalysts. The specific impulse is also increased from 225 s to 235 s at 10 MPa by the replacement of 30% AN by the same amount of AP. However, the smokeless nature is eliminated because of the production of HC1, and these propellants are classified as reduced smoke propellants. 

Powell J (2005) Reduced vulnerability minimum smoke propellants for taetieal roeket motors. In 41st AIAA/ASME/SAE/ASEE joint propulsion conference and exhibit, Tueson... 

Liquid food can be filled into pressurized containers and, when needed, using a propellant, discharged in the form of a cream or paste (e.g. cream cheese, ketchup), a foam (whipping cream) or a mist (herb or spice extracts in oil liquid barbecue smoke). Propellants used are N2, N2O, and CO2. 

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