A SURVEY OF ROCKET PROPELLANTS

A SURVEY OF ROCKET PROPELLANTS

Another in the Series of Chemical Studies

PART 2

THE TERMS “exotic” or “zip” fuels are frequently mentioned in the literature and newspapers. The description “exotic” was applied in the early stages of rocket fuel development when new combinations, not in common usage at the time, were proposed. In 1952 the Navy set up Project Zip to develop superior fuels and some of the combinations to come from this research were dubbed “zip” propellants. Neither of these designations refer to any one specific system but either of them could apply to the boranes.

In theory, pure hydrogen with a yield of 52,000 BTU/lb is the most logical choice for a fuel; its density, however, is too low and even when liquidfied is ten times as bulky as gasoline. Beryllium, on combustion, gives up 29,000 BTU/lb but is rare, costly and highly toxic in chemical compounds. Boron’s 25,000 BTU/lb places it 40 percent above the less than 19,000 BTU/lb hydrocarbon rating and on combination with hydrogen produces an even higher heat content. Boron, therefore, seemed a likely candidate for investigation as a fuel possibility and the three basic compounds listed below were considered.

Diborane is the basic substance in the group from which the others are derived. An interesting sidelight on its combustion in air is that it yields boric oxide, the active reaction product in the extinguishing mechanism of trimethoxyboroxine, a recently developed agent used on fires involving certain metals. Like any other gas fire, diborane, burning with the green Hame characteristic of boron compounds, should not be extinguished unless its source can be shut off. Small laboratory leaks resulting in minor fires can be extinguished by carbon dioxide or dry chemical. Chlorinated hydrocarbons should never be used. The fire hazard of diborane and derivatives such as aluminum borohydride, Al(BH), is intensified by their spontaneous flammability in air.

The Callery Chemical Company advises that, “Diborane is now supplied as a compressed gas in 100-gram, 1-pound, 2-pound and 4-pound lots. The special returnable cylinders and crates are shipped by Railway Express. Since not more than five days are allowed in transit, diborane is shipped only on Mondays and Thursdays, so that the fifth day will not occur on a weekend.”

In addition to the use of boranes as a primary fuel, investigation is also in progress to test its use as an additive for increasing the efficiency of other systems. Pentaborane, for instance, added to aircraft fuel can increase range by 50 percent. One boron-based aircraft fuel related to the boranes, designated as HEF-2 by the Olin Mathieson Chemical Corporation, and used for oxygen breathing engines, while not spontaneously flammable can ignite on contact with hot surfaces. If it is involved in fire, foam is the most effective extinguishing agent.

Although the boranes are toxic, it is difficult to specify all the effects on the human body due to a lack of clinical experience. Diborane attacks the lungs in contrast to pentaborane and decaborane which affect the central nervous system. Detection of low concentrations of boranes is an exacting procedure because of the problems of chemically analyzing for them. Several monitoring devices are under development but there is no commercial borane detector on the market. A 3 percent aqueous solution of ammonia will neutralize spills and wash boranes from the skin, garments or floors.

While the exact composition of borane fuels is a secret, one surmise is that they are probably modifications of decaborane which changes to the liquid state upon the addition of hydrocarbon groups to its molecule. They are stable, can be transported safely and stored without deterioration. Because precise information on any one borane-based rocket fuel with regard to its chemical composition and physical characteristics is classified information, it is not possible to discuss specific fuels in this light and assign to each the proper extinguishing methods based upon stated properties.

Storage compatability

Where operations involve materials that are highly reactive and in addition are hypergolic on contact with certain other chemicals, the storage problem becomes a primary consideration and requires specification in the most minute detail.

Marine Corps anti-aircraft missile, an adaptation of Navy's Terrier, uses a solid propellant booster. Twin missile carrier is used for field transportation

—U. S. Marine Corps

Compatible Storage Groups

Group “A”

Nitric acid

Mixed acid (Nitric and Sulfuric)

Group “B”

Aluminum borohydride

Diborone

Other metal borohydrides

Pentaborone

Group “C”

Anhydrous ammonia

Hydrazine, anhydrous

Hydrazine, hydrate

Group “D”

Aniline

Monoethylaniline Furfuryl alcohol

Group “E”

Calcium permanganate

Solid sodium permanganate

Group “F”

Compressed hydrogen gas

Compressed inert gas

Group “G”

Compressed oxygen gas

Compressed inert gas

Group “H”

Ethyl alcohol

Methyl alcohol

Group “I”

Gasoline

Heptane

Kerosene

Octane

Pentane

Group “J”

Hydrogen peroxide

Group “L”

Liquid fluorine

Group “N”

Liquid hydrogen

Group “O”

Liquid oxygen

Group “R”

Nitromethane

Tetramethane

Fueling specialists prepare to service Jupiter-C rocket at Cape Canaveral, Fla. Note use of demand breathing apparatus and 0-10-type crash unit behind fuel truck

—U. S. Army

Army fueling specialist stands ready to wash down crew members should spillage occur during fueling of missile on launching pad at Cape Canaveral

—U. S. Army

Storage computability is one phase of these requirements and listed at left is a portion of the table set up by the Army for fuels and oxidizers. Those chemicals in the same group are deemed to be compatible for storage because individual characteristics are such that their presence together does not increase the normal hazard of storage alone.

Quantity-distance tables are also charted for fuels and oxidizers. They specify minimum allowable distance between storage of fuels and oxidizers, minimum distance of each substance from inhabited buildings, public railways, public highways and the minimum distance between storage facilities in order that flame or explosion in one will not propagate to another.

Fire hazard

The fire hazard of propellants varies with the components involved. A consideration of physical and chemical characteristics will give some understanding of extinguishment problems. Among the important related properties are density, solubility or miscibility in water, vapor pressure, flammability limits, toxicity and combustion temperatures of the propellants.

Many of the fuels are alcohols or hydrocarbons and fires can be handled in accordance with standard procedures for this type of operation. In some cases, how’ever, these basic fuels contain additives which may be highly toxic and indicate the use of a self-contained breathing apparatus.

In general, the rocket fuels of today, unless otherwise indicated, are miscible with water which continues to be our primary extinguishment agent in the forefront as the most potent weapon for fighting propellant fires. Application in the form of a coarse fog or spray at not less than 100 pounds per square inch pressure, will fulfill the requirements for extinguishment and dilution. One Army test involved a propellant system containing an aniline-furfuryl alcohol as the fuel and red fuming nitric acid as the oxidizer. Each component was in a small earthen pool separated by a wall which was blasted away to initiate the combustion. Application of water at the rate of 1,500 gallons per minute extinguished the fire in 45 seconds.

Jupiter-C rocket with mounted Explorer satellite stands on Cape Canaveral launching pad as technicians make final adjustments

In the laboratory, small quantities can be handled efficiently with carbon dioxide or dry powder extinguishers.

Where more stringent requirements are not specified, storage and handling should be in conformance with I.C.C. regulations.

The future in fuels

While the results of present research and development may appear to approach the ultimate, still more seemingly fantastic possibilities are being explored. On the boards are a number of nuclear fission designs, one of which envisions a small atomic pile to heat hydrogen several thousand degrees and blast it through the exhaust nozzle.

Power through the utilization of free radicals may be the supreme achievement in space technology. Free radicals are unstable fragments of chemical compounds which have been observed in flame and high speed reactions, existing only for millionths of a second. Upon recombination, these free radicals release the enormous heat necessary to approach a maximum degree of efficiency. Normally gases such as oxygen and hydrogen exist in the molecular form of two atoms combined (O2,H2). In the upper atmosphere there is a large source of these gases in the uncombined single atom or free radical state (O, H). Two directions of research are in progress to harness this vast reservoir of power. An attempt is being made to isolate and freeze free radicals in the laboratory and another announced method makes use of the atmospheric free radicals. Nitric oxide has been used as a catalyst in the 60 to 70 mile atmosphere region, the level of the single-atom oxygen layer. A solid catalyst to line the rocket cents so that the recombination process can take place within the device and create thrust producing heat has been reported by the Air Force’s Cambridge (Mass.) Research Center as a promising possibility.

BIBLIOGRAPHY

Lippmann, “Tailoring Molecules for Rockets”; (Aeronautical Engineering Review, Vol. 16, No. 3, March 1957)

Schneider, “Rocketry: A New Means of Transportation”; (Background material for Rocket Exhibition—Queens College, Feb. 1958)

“Liquid Propellant Roundup”; (Missiles and Rockets, Vol. 2, No. 9, Sept. 1957)

“Solid Fuel Roundup”; (Missiles and Rockets, Vol 2, No. 8, August 1957)

“Jet Aircraft Fuels”; National Board of Fire Underwriters (Special Interest Bulletin No. 182, January 1958)

“The Storage and Handling of Jet Fuels at Airports”; American Petroleum Institute, (API Bulletin 1503, second Edition, May 1956)

Lessing, “Hydrazine”; (Scientific American, Vol. 189, No. 1, July 1953)

Strunk, “Dimazine Comes of Age as Rocket Fuel”; (Missiles and Rockets, Vol. 2, No. 9, Sept. 1957)

“Four Killed in ‘Space Age’ Fire Blast”; (Fire Engineering, Vol. Ill, No. 4, April 1958)

Boehm, “The Search For the Ultimate Fuel”; (Fortune, Vol. LVI, No. 6, December 1957)

Canright, “Chemical Lessons Learned From Nike-Ajax Development”; (Industrial and Engineering Chemistry, Vol. 49, No. 9, Sept. 1957)

Terlizzi and Streim, “Liquid Propellant Handling, Transfer and Storage”; (Industrial and Engineering Chemistry, Vol. 48, No. 4, April 1956)

Neumark and Holloway, “Fluorine Tamed For Rockets”; (Missiles and Rockets, Vol. 2, No. 9, Sept. 1957)

Deschere, “Applied Research and Project Development for Rocket Propellants”; (Industrial and Engineering Chemistry, Vol. 49, No. 9, Sept. 1957)

Davis and Keefe, “Concentrated Hydrogen Peroxide as a Propellant”; (Industrial and Engineering Chemistry, Vol. 48, No. 4, April 1956)

“Rocket Engine Propellants”; (Rocketdyne, A Division of North American Aviation, Inc.)

Schechter, “How Toxic are High Energy Fuels?”; (National Safety News, Vol. 77, No. 4, April 1958)

“Ordnance Safety Manual”; Department of the Army, (ORD-M-7-224, Washington, D.C., 1951)

Malcolm, “New Fuel Extinguishment Research”; (Proceedings U.S. Naval Civil Engineering Research and Evaluation Laboratory Symposium on Fire Extinguishment Research and Engineering, November 1954)

New York Times, “Moon Shot Date in Dispute”, Vol. CVII, No. 36, 663, Page 1 Col. 7, June 11, 1958)

New York Times, “U.S. Likely to Make SolidFuel Missiles Key Defense by ’65,” Vol. CVII, No. 36,667, Page 1 col. 3, June 15, 1958.

New York Times, ” ‘Super Fuel’ to Drive Rocket Indefinitely in Space,” Vol. CVI, No. 36,324, Section 4, Page 47 col. 5, July 7, 1957)

New York Times, “New Satellite Is Regarded as Test Sphere and Is Expected to Yield Little Data,” Vol. CVII, No. 36,578, Page 15 col. 1, March 18, 1958)

New York Times, “8 Nikes Explode at Jersey Base; 10 Killed, 3 Hurt,” Vol. CVII, No. 36,644, Page 1, col. 8, May 23, 1958)

“Diborane”; (Callerv Chemical Company, Technical Bulletin C-020, March 15, 1958)

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A SURVEY OF ROCKET PROPELLANTS

25

A SURVEY OF ROCKET PROPELLANTS

Another in the Series of Chemical Studies

This survey is merely the introduction to the subject of rocket propellants. It is not a study that will of necessity affect every one involved in fire protection, but the time is here to start your file. Undoubtedly, new techniques or extinguishing agents will be developed to improve our present knowledge. It is fervently hoped that this will come about as a result of successful research rather than information gathered in the ruins of future holocausts.

ROCKETRY, like many new developments on the scene, poses a problem in fire protection. The fuels employed in the propulsion of these most modern of vehicles possess inherent flammability and explosibility characteristics that require a consideration of top priority.

Keeping informed on the innovations in this field is a task of major proportions. Events move so swiftly that it is as important to consult the daily press as the basic references.

When the Navy’s Vanguard I kicked off its launching pad at 7:15:41 a.m., March 18, 1958, the firing ended months of frustration and the three-stage rocket set its satellite in orbit with the power of a variety of fuel and oxidizer combinations.

The first stage utilized kerosene for the basic fuel and liquid oxygen as the oxidizer. Both tanks were pressurized by helium to prevent spasmodic starvation of the fuel chamber and each ingredient was pumped into the combustion chamber by high pressure steam generated by the decomposition of hydrogen peroxide.

The second stage, which boosted the speed from 3700 to 9000 miles per hour, was fueled with unsymmetrical dimethylhydrazine and white fuming nitric acid. It was a leak in the nitric acid line that prevented a previous attempt from successfully orbiting the satellite.

Two small solid propellant rockets, mounted perpendicular to the direction of travel, fired as designed, giving the third stage a spinning motion to maintain directional stability. Then two similar “retro” rockets produced a thrust opposite the direction of travel to separate the second stage from the third, which, powered by a solid propellant also, proceeded to attain the 18,000 mileper-hour speed required to complete the mission.

In order to consider the fuel in proper perspective, it is important to observe its function in relation to the entire device. As in many new inventions, the reaction motor is a new application of an old principle. A long time ago Newton recorded his laws of motion, one of which states, “Every action has an equal and opposite reaction.” Gases generated under high pressure as a result of fuel combustion push out of the rocket’s open end to supply the action. The body of the rocket is forced away from the expelled gases in the “reaction” phase of the phenomenon, measured in pounds of thrust.

While in the basic principle the rocket and jet plane are related, there are differences. The jet operates on a fuel that requires oxygen for combustion. The rocket or reaction motor carries as part of its chemical propellant an oxidizing agent that makes it independent of any external supply of oxygen. This variation is of paramount importance and accounts for the fact that the jet plane is limited to operation within the earth’s atmosphere. On the other hand, the rocket is not confined to lower space boundaries. By virtue of self-contained design, it can operate in the outermost regions of space and attain any altitude or position in the universe to which fuel is capable of propelling it.

It is interesting to note the difference between a rocket and a missile. A rocket is utilized for any non-military purpose such as transportation or gathering scientific data from outer space. The missile is a rocket, the sole purpose of which is to carry an explosive warhead to a military target. When the missile contains a system, either self-contained or operated from the ground, to direct the target approach, it is known as a “guided missile.” A “ballistic missile” has its direction and target set before firing and once in flight continues on its trajectory subject to the influence of winds, pressure, temperature and other atmospheric conditions.

The rocket motor is in essence a heat engine which converts the chemical energy of propellants into heat and the heat into motion. The thrust achieved by the rocket motor is developed in proportion to the exhaust velocity of the reaction products. To generate a high exhaust velocity, the reaction propellants must yield a large quantity of heat per unit mass and this accounts for the use of the lightest elements as propellants.

Aluminum, lithium and magnesium are among the favored metals. Carbon and boron are desirable non-metals. Oxygen, hydrogen, fluorine and nitrogen are also on the list of those chemicals that satisfy the required criteria. By incorporating high energy configurations such as — C = C-, >N-N<, and -O-Oin combination with other elements, the heat yield is greatly enhanced.

Navy Vanguard rocket explodes on launching pad at Cape Canaveral, Fla., during unsuccessful attempt to launch space satellite into orbit

U. S. Navy photo

Once the propellant has produced its maximum heat, the efficiency with which it is converted into motion is dependent upon the molecular weight of the exhaust gases. The lighter the products of combustion, the greater the energy yield. Therefore an attempt is made to develop propellants giving off such light products as hydrogen, carbon dioxide and water vapor. While no one propellant will have maximum rating in all characteristics that develop the highest efficiency, in addition to stability and high density, research is directed toward developing propellants with the optimum balance of properties.

Fuels and oxidizers

Classification of propellants sets apart fuels, oxidizers and monopropellants. The bipropellant system, a combination of a fuel and an oxidizer, is used in the majority of propulsion systems. A monopropellant is a single liquid or mixture of substances that contains all the necessary ingredients to generate the required energy.

There are also two major groupings that are resolved into liquids and solids. Each has its own advantages and disadvantages. Liquid fuels give greater energy but require more intricate accessory equipment in the nature of piping, nozzles, ignition and pumping devices. The mechanical components are subjected to severe stresses and strains due to the high speeds and temperature variations. A major flaw that plagued three long-range missiles, Thor, Jupiter and Atlas, was traced to a pump that delivers fuel and liquid oxygen to the combustion chamber. Redesigning the parts to correct burrs on one pump gear and a weak spline shaft on which it turned resulted in satisfactory performance.

Solid fuels are more easily handled, necessitate few moving parts and eliminate many of the objections to liquid propellants. As if in compensation for this advantage, however, the solids have a much lower energy yield and are used for smaller vehicles in the present state of development. The fuel and oxidizer are intimately mixed. In some cases the fuel is a binder for the crystalline oxidizer, while the nitrated type of propellant has the oxidizer chemically linked to the fuel. Ammonium nitrate and potassium chlorate have been used as oxidizers mixed with a variety of thermoplastic or thermosetting plastics as the combination fuel and binder. Among the criteria that dictates the use of one solid propellant in preference to another are the energy released per unit weight and volume, burning rate and variation with temperature and pressure, ease of ignition under control, accidental ignition potential, property changes in storage and method of installing propellant in rocket motor.

Considering the advantages of solid fuels, the trend is definitely toward increased application as their energy level is improved. An estimate, among some leaders of the nation’s missile program, highlights the likelihood of the solid propellant missiles, Polaris (Navy-sea based) and Minuteman (Air Force-land based), taking over the bulk of the nation’s defense by 1965.

Among fuels that have been investigated are liquid ammonia, ethyl alcohol, aniline mixtures, hydrazines, hydrogen and various petroleum products and derivatives. In the category of oxidizers are liquid oxygen, fuming nitric acid, fluorine, chlorine, trifluoride, ozone, ozone-oxygen mixtures and concentrated hydrogen peroxide. As monopropellants, ethylene oxide, hydrazine, hydrogen peroxide and nitromethane have been used. With the exception of ethylene oxide, the monopropellants named can also be used as a fuel or an oxidizer. Although some of these names are familiar, they are loaded in such high concentrations that ordinary handling and precautionary measures are inadequate.

One measurable reference, specific impulse, is common to all propellants and a fundamental basis of comparison. By definition, specific impulse is thrust in pounds, obtained from chemical reaction of a pound of mixture per second and the unit is pounds per pound per second. Propellant volume is also of great significance and specific impulse multiplied by bulk density is another piece of data upon which selection is based. In the table on the preceding page is listed a number of propellant combinations with some important characteristics of each.

JP-4—a modern jet fuel

JP-4, used in a number of rocket propellant systems, was originally a fuel for jet-propelled military aircraft. It is a blend of gasoline and kerosene containing a wide variety of hydrocarbons and as such has no one specific chemical formula. Flash points range from 30 to as low as —10 degrees F. and ignition temperatures from 485 to 625 have been recorded. For all practical purposes it should be considered as having the same hazards as gasoline and handled accordingly. Where foam is provided for other petroleum product storage tanks, the American Petroleum Institute recommends that it should also be made available for protection of JP-4. Relatively non-conducting, generation of static electricity will depend on turbulence during transfer and presence of finely divided conductive impurities such as rust or water. Because JP-4 is more viscous than gasoline, it will tend to hold the impurities in suspension longer and is therefore more susceptible to static generation. Once the suspended materials have settled, however, the tendency toward inducing a static charge is the same in both liquids.

Fluorine

The most powerful oxidizing agent known, fiuorine reacts with most substances, often accompanied by ignition. Liquid fluorine spills can be rendered harmless by neutralizing with sodium bicarbonate applied from a dry powder type of extinguisher. This form of application is also effective in extinguishing any fire caused by the contact of fluorine with a combustible substance. Water is not recommended for use on fluorine. A violent reaction results with the generation of hydrogen fluoride which is almost as dangerous as the fluorine itself, although it will not support combustion.

Worcester, Mass., firemen control flames involving wreckage of a jet plane and three dwellings sprayed with blazing fuel when plane crashed into residential area

Fluorine is one of the oxidizing agents successfully used with a variety of fuels. Its combination with fuels had to be curtailed for some time because of the difficulty in handling and shipping. Formerly, shipping restrictions limited the contents to 6 pounds of fluorine in a 200pound cylinder under 400 pounds of pressure. This uneconomical ration of 1 pound of gas to 33 pounds of container sharply restricted its use until Allied Chemical and Dye Corporation developed a practical tank system permitting bulk storage and shipment of liquid fluorine under ICC approval.

The unique tank system containing no moving parts or mechanical refrigeration took over two years to develop. It consists of three horizontal tanks, one inside the other. The fluorine is maintained in a liquid state in the center tank by liquid nitrogen in the second which is surrounded by an insulating shield in the space between the second and third tanks. Liquid nitrogen boils at —320 degrees F., 14 degrees below the —306 degrees F. boiling point of liquid fluorine. The temperature difference maintains the liquid fluorine in a condition free from any pressure rise as long as there is liquid nitrogen in the second tank and the insulating shield is so efficient that nitrogen losses are maintained at a very low level. This system can be used for bulk storage, trailer or railroad car transportation.

Army anti-aircraft missile Nike-Ajax is liquidpropelled and carries high explosive warhead.Nike-Hercules solid propellant missile which will replace Ajax. It can carry thermo-nuclear warhead

U. S. Army photos

Hydrazine

Hydrazine, an extremely active substance with the formula H2NNH2, fueled the German rockets that were used in the closing days of World War II. The four hydrogen atoms are quick to unite with an oxidizing agent in chemical combustion. With a lower explosive limit of 4.7% by volume in air, it varies from other fuels because there is no upper limit to the explosive range and it will dissociate with explosive violence in 100 percent concentration. Flash point varies with concentration of the liquid from 126 degrees F. for a pure hydrazine to 235 degrees F. for 40 percent hydrazinewater solution. Ignition temperature is 518 degrees F. Utmost care in handling is essential to prevent contamination with decomposition catalysts such as iron, molybdenum and copper oxides which can cause spontaneous ignition. Ignition will also occur when hydrazine is exposed to the atmosphere on porous substances such as asbestos, carbon or iron filings. Large quantities of water are recommended for extinguishing fires involving hydrazine.

Engineers fire rocket-powered fire extinguishers carrying borate solution in warhead during tests to determine their possible use in fighting inaccessible forest and brush fires

Unsymmetrical dimethylhydrazine

Unsymmetrical dimethylhydrazine (CH3)2NNH2, is similar in many respects to hydrazine from which it is derived. With widely separated flammability limits of 2.5 percent to 95 percent by volume, a flash point of 34 degrees F. and an ignition temperature of 482 degrees F., it possesses a high hazard potential and like hydrazine is stored under nitrogen. For all practical purposes a flammable mixture is present whenever it is exposed to air. UDMH, as it is abbreviated, burns cleanly and smoothly. Application of large volumes of water achieves both extinguishment of a UDMH fire and a dilution effect. Two or more volumes of water to one of UDMH is sufficient to extinguish a fire involving it. While a higher concentration in water will support combustion, the flame intensity can be observed to diminish as dilution occurs. Carbon dioxide is an effective extinguishing agent but standard and alcohol-type foams are unsatisfactory due to deactivation of the foam-forming surfactant.

Hypergolicity is the characteristic of spontaneous ignition on contact of a fuel and oxidizer. The hypergolicity of UDMH and fuming nitric acid makes it an outstanding rocket fuel. Having the shortest ignition delay of any known combination, this system spontaneously ignites in only a few thousandths of a second.

Addition of UDMH to other systems gives reliability to an otherwise nonhypergolic combination. The Army “Nike-Ajax” missile makes use of this principle. A JP-4 with small amounts of UDMH, is designated as M-3, and used with red fuming nitric acid. The fuel is supplied in premetered tanks to preclude the disadvantages of transfer from bulk storage. The twisted wreckage of launching platforms and the death of 10 men at Middletown, N. J., missile base on May 22, 19581 attests to the damage that can be done when a system gets out of control. Eight Nike-Ajax missiles exploded on the ground and scattered debris three miles from the 526th Missile Battalion installation.

Hydrogen peroxide

Hydrogen peroxide (H2O2), a strong oxidizing agent, is most usually employed in 90 percent concentration for propulsion applications in this country and can be utilized either as an oxidizer or a monopropellant. While this is a highenergy material requiring systematic care in handling, it lacks the hazard of volatile flammable liquids because it presents no hazard in the presence of a spark.

The dangerous features of hydrogen peroxide include possibility of fire when spilled on clothing or combustible materials. Neither Dynel nor Dacron fabrics, however, ignite on exposure to this oxidizer. Any fire caused by hydrogen peroxide and ordinary combustible materials can be extinguished by water. Water will also dilute any spill and reduce the oxidizing potential to the point where it will prevent ignition on contact with combustible material.

Testing for detonation sensitivity by a number of laboratories has revealed little likelihood of explosion. Contact with a soluble organic substance, however, can lead to an explosion by creating a condition comparable to a hydrocarbon and air mixture. Alcohols, glycols, acetates, acids and ketones combined with 90 percent hydrogen peroxide result in a highly explosive solution. It also forms explosive mixtures with gasoline, kerosene, petroleum ether and fuel oil.

Continued on page 763

‘Fire Engineering, July, 1958

ROCKET PROPELLANTS

Continued, from page 679

Hydrogen peroxide is usually shipped in special aluminum drums containing 300 pounds or in 4000, 6000, or 8000 gallon railway tank cars. Mobile selfcontained units for servicing missiles have been developed for field transfer.

The ease with which hydrogen peroxide can be decomposed catalytically into oxygen and steam enhances its value as a propellant. This is particularly true in application as a monopropellant when it is necessary to power a steam turbo pump within the missile.

An interesting related application as a monopropellant is the use of a 280 pound tank of 90 percent hydrogen peroxide on the rotor shaft of a helicopter. The propellant is fed to a small catalyst chamber at the tip of each rotor by centrifugal force and decomposed with the exhaust jet supplying auxiliary driving power for the rotor. As a result of this power assist, pay load, rate of ascent and hovering ceiling are considerably increased.

To be continued