Monopropellant

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Monopropellants

propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with bipropellants that release energy through the chemical reaction between an oxidizer and a fuel. While stable under defined storage conditions, monopropellants decompose very rapidly under certain other conditions to produce a large volume of its own energetic (hot) gases for the performance of mechanical work. Although solid deflagrants such as nitrocellulose, the most commonly used propellant in firearms, could be thought of as monopropellants, the term is usually reserved for liquids in engineering literature.[2]

Uses

The most common use of monopropellants

catalyst mesh,[9] or comes in contact with manganese dioxide impregnated ceramic beads, or Z-Stoff permanganate
solution is co-injected, which causes hydrogen peroxide to decompose into hot steam and oxygen.

Monopropellants are also used in some

Otto fuel
". A potential future use for monopropellants not directly related to propulsion is in compact, high-intensity powerplants for aquatic or exoatmospheric 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[when?] re-examining this assumption.[citation needed]

Many partially nitrated alcohol esters are suitable for use as monopropellants. "Trimethylene glycol dinitrate" or

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.[citation needed
]

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.[citation needed
]

Hydrazine,[6][11] ethylene oxide,[12] hydrogen peroxide (especially in its German World War II form as T-Stoff),[13] and nitromethane[14] are common rocket monopropellants. As noted the specific impulse of monopropellants is lower[3][15] than bipropellants and can be found with the Air Force Chemical Equilibrium Specific Impulse Code tool.[16]

One newer monopropellant under development is nitrous oxide, both neat and in the form of nitrous oxide fuel blends. Nitrous oxide offers the advantages of being self-pressurizing and of being relatively non-toxic, with a specific impulse intermediate between hydrogen peroxide and hydrazine.[17] Nitrous oxide generates oxygen upon decomposition, and it is possible to blend it with fuels to form a monopropellant mixture with a specific impulse up to 325 s, comparable to hypergolic bipropellants.[18] In 2018 a new precious metal catalyst was invented for use with nitrous oxide -  rhodium oxide on alumina spheres – which is more stable at higher temperatures than pure rhodium or iridium.[19]

Direct comparison of physical properties, performance, cost, storability, toxicity, storage requirements and accidental release measures for hydrogen peroxide, hydroxylammonium nitrate (HAN), hydrazine and various cold gas monopropellants shows that hydrazine is the highest performing in terms of specific impulse. However, hydrazine is also the most expensive and toxic. In addition HAN and hydrogen peroxide have the highest density impulse (total impulse per given unit volume).[20]

See also

References

  1. ISBN 978-0-07-042313-8
    . A rocket propellant consisting of a single substance, especially a liquid, capable of creating rocket thrust without the addition of a second substance.
  2. ISBN 978-1-349-06904-0
    .
  3. ^ a b RAND Corporation (1959). "Propellants". In Horgan, M. J.; Palmatier, M. A.; Vogel, J. (eds.). Space handbook: astronautics and its applications (Technical report). United States Government Printing Office. pp. 42–46. 86.
  4. ^ "Resources". Rocket Motor Components, Inc. Archived from the original on January 14, 2012.
  5. ^ [1] Archived September 28, 2009, at the Wayback Machine
  6. ^ a b Sutton 1992, p. 230
  7. ^ "Aerojet Bipropellant Engine Sets New Performance Record". Aerojet Rocketdyne. December 8, 2008. Archived from the original on March 7, 2017. Retrieved July 13, 2014.
  8. ^ Sutton 1992, pp. 307—309
  9. ^ a b RAND Corporation (1959). "Propulsion systems". In Horgan, M. J.; Palmatier, M. A.; Vogel, J. (eds.). Space handbook: astronautics and its applications (Technical report). United States Government Printing Office. pp. 31–41. 86.
  10. ^ Sutton 1992, ch. 7.
  11. ^ "Monopropellant Hydrazine Thrusters". EADS Astrium. Archived from the original on March 27, 2010.
  12. ^ "ethylene_oxide.pdf" (PDF). Archived from the original (PDF) on March 21, 2012.
  13. ^ "h2o2.pdf" (PDF). Archived from the original (PDF) on March 21, 2012.
  14. ^ "nitromethane.pdf" (PDF). Archived from the original (PDF) on March 21, 2012.
  15. ^ Sutton 1992, p. 36
  16. ^ Dunn, Bruce P. (2001). "Rocket Engine Specific Impulse Program". Dunn Engineering. Archived from the original on October 20, 2013.
  17. doi:10.1016/S0094-5765(01)00047-9
    .
  18. ^ Morring, Frank Jr. (May 21, 2012). "SpaceX To Deliver Green-Propulsion Testbed To ISS". Aviation Week and Space Technology. Retrieved July 13, 2014.
  19. ^ "Catalysts". American Elements. Retrieved 2024-01-05.
  20. ISBN 978-1-62410-038-3
    .

External links

Wikimedia Commons has media related to Monopropellants.

John D. Clark (1972). Ignition! An Informal History of Liquid Rocket Propellants (PDF).

ISBN 0-8135-0725-1
.

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