Monopropellant



Monopropellants are chemicals or mixtures of chemicals which can be stored in a single container with some degree of safety. While stable under defined storage conditions, they react very rapidly under certain other conditions to produce a large volume of energetic (hot) gasses for the performance of mechanical work. Although solid deflagrants such as oxidizer) that can be made to react with one another to release energy.

Uses

The most common use of monopropellants is in low-impulse rocket motors, such as reaction control thrusters, the usual propellant being Otto fuel". The most recent models of the British Spearfish torpedo (see Torpedo and the references therein for further discussion) are powered by an admixture of this with hydrogen ammonium perchlorate (HAP), a solution that, excluding future developments, would appear to be very nearly optimal. A potential future use for monopopellants not directly related to propulsion is in compact, high-intensity powerplants for aquatic or exoatmosperic environments.

Research in brief

Much work was done in the US in the 1950s and 1960s to attempt to find better and more energetic monopropellants. For the most part, researchers came to the conclusion that any single substance that contained enough energy to compete with bipropellants would be too unstable to handle safely under practical conditions. With new materials, control systems and requirements for high-performance thrusters, engineers are currently re-examining this assumption. Many partially nitrated alcohol esters are suitable for use as monopropellants. Trimethylene glycol dinitrate is isometric with PGDN, and produced as a fractional byproduct in all but the most exacting laboratory conditions; the marginally lower specific gravity (and thus energy density) of this compound argues against its use, but the minor differences in chemistry may prove useful in the future. The related dinitrodiglycol, more properly termed aromatic hydrocarbons are invariably room temperature solids, but many are soluble in simple alcohols or ethers in high proportion, and may be useful in this state.

References

There is an entire chapter on the history of monopropellant development in the book Ignition! An Informal History of Liquid Rocket Propellants (ISBN 0-8135-0725-1) by John D. Clark, first published in 1972.

The otherwise mediocre "Germany's Secret Weapons In World War Two" by Roger Ford (ISBN 0-7603-0847-0 c.2000) contains some useful information on the surprising diversity of fuels and propellants employed by wartime Germany.

"The Chemistry Of Powder And Explosives" by Tenney L. Davis is an outstanding, if outdated, source of information on a great many aspects of high enthalapy compounds. (This work originally published by MIT Press, 1943, as a textbook. Subsidy republication as late as 1995 by Pyrotek Inc., an amateur rocketry supply house. No catalog data given in this edition. Current publication status unknown.).

See also

  • Monopropellant rocket
 
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