Monopropellant

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Monopropellants [1] are 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]

Contents

Uses

The most common use of monopropellants [3] is in low-impulse monopropellant rocket motors, [4] such as reaction control thrusters, the usual propellant being hydrazine [5] [6] which is generally decomposed by exposure to an iridium [7] [8] catalyst bed (the hydrazine is pre-heated to keep the reactant liquid). This decomposition produces the desired jet of hot gas and thus thrust. Hydrogen peroxide [9] has been used as a power source for propellant tank pumps in rockets like the German WWII V-2 and the American Redstone. [10] The hydrogen peroxide is passed through a platinum 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 air-independent propulsion systems (AIP) to "fuel" reciprocating or turbine engines in environments where free oxygen is unavailable. Weapons intended primarily for combat between nuclear-powered submarines generally fall into this category. The most commonly used propellant in this case is stabilized propylene glycol dinitrate (PGDN), often referred to as "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 1,3-propanediol dinitrate is isomeric 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.[ citation needed ]

The related "dinitrodiglycol", more properly termed diethylene glycol dinitrate in modern notation, was widely used in World War 2 Germany, both alone as a liquid monopropellant and colloidal with nitrocellulose as a solid propellant. The otherwise desirable characteristics of this compound; it is quite stable, easy to manufacture, and has a very high energy density; are marred by a high freeze point (-11.5 deg. C) and pronounced thermal expansion, both being problematic in spacecraft. "Dinitrochlorohydrin" and "tetranitrodiglycerin" are also likely candidates, though no current use is known. The polynitrates of long chain and 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

Related Research Articles

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<span class="mw-page-title-main">Hybrid-propellant rocket</span> Rocket engine that uses both liquid / gaseous and solid fuel

A hybrid-propellant rocket is a rocket with a rocket motor that uses rocket propellants in two different phases: one solid and the other either gas or liquid. The hybrid rocket concept can be traced back to the early 1930s.

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<span class="mw-page-title-main">Hydrazine</span> Colorless flammable liquid with an ammonia-like odor

Hydrazine is an inorganic compound with the chemical formula N2H4. It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydrazine hydrate.

<span class="mw-page-title-main">Hypergolic propellant</span> Type of rocket engine fuel

A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other.

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<span class="mw-page-title-main">Hydroxylammonium nitrate</span> Chemical compound

Hydroxylammonium nitrate or hydroxylamine nitrate (HAN) is an inorganic compound with the chemical formula [NH3OH]+[NO3]−. It is a salt derived from hydroxylamine and nitric acid. In its pure form, it is a colourless hygroscopic solid. It has potential to be used as a rocket propellant either as a solution in monopropellants or bipropellants. Hydroxylammonium nitrate (HAN)-based propellants are a viable and effective solution for future green propellant-based missions, as it offers 50% higher performance for a given propellant tank compared to commercially used hydrazine.

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<span class="mw-page-title-main">Rocket propellant</span> Chemical or mixture used as fuel for a rocket engine

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The Green Propellant Infusion Mission (GPIM) was a NASA technology demonstrator project that tested a less toxic and higher performance/efficiency chemical propellant for next-generation launch vehicles and CubeSat spacecraft. When compared to the present high-thrust and high-performance industry standard for orbital maneuvering systems, which for decades, have exclusively been reliant upon toxic hydrazine based propellant formulations, the "greener" hydroxylammonium nitrate (HAN) monopropellant offers many advantages for future satellites, including longer mission durations, additional maneuverability, increased payload space and simplified launch processing. The GPIM was managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, and was part of NASA's Technology Demonstration Mission Program within the Space Technology Mission Directorate.

Cavea-B is a mixture of 1,4-Diaza-1,2,4-trimethyl bicyclo[2.2.2]octane dinitrate, dissolved in white fuming nitric acid. It was researched during the 1960s by teams associated with NASA as an alternative to the more commonly used hydrazine monopropellant for use in spacecraft's attitude control and thruster systems. It was derived from an earlier, similar formulation which came to be called Cavea-A, which showed less promise due to its excessively high melting point.

References

  1. ↑ Sybil P. Parker (2003). McGraw-Hill dictionary of scientific and technical terms (6 ed.). McGraw-Hill. p. 1370. 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. ↑ Vere, Ray (1985). Aviation Fuels Technology. Macmillan Education UK. p. 223. ISBN   978-1-349-06904-0.
  3. 1 2 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. ↑ Archived September 28, 2009, at the Wayback Machine
  6. 1 2 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. 1 2 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. ↑ Zakirov, Vadim; Sweeting, Martin; Lawrence, Timothy; Sellers, Jerry (2001). "Nitrous oxide as a rocket propellant". Acta Astronautica. 48 (5–12): 353–362. Bibcode:2001AcAau..48..353Z. 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. ↑ Wernimont, Eric (2006). "System Trade Parameter Comparison of Monopropellants: Hydrogen Peroxide vs Hydrazine and Others" (PDF). 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit. doi:10.2514/6.2006-5236. ISBN   978-1-62410-038-3.
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