History and Technology - Naval Propellants - A Brief Overview (2024)

In 1892, the Austro-Hungarian Imperial Navy started using a single-based "smokeless powder" designated as M.92 consisting of 100% nitrocellulose (12.3% nitrogen). There appears to have been three variations of M.92 manufactured, with slight differences between the different types. Like other pure nitrocellulose propellants of this time, the M.92 types were unstable and in 1893 the Navy switched to a double-based nitrocellulose/nitroglycerin propellant designated as M.93. This had no stabilizer elements and again proved unstable.

In 1897 the Navy introduced a new double-based propellant designated as M.97 that included barium nitrate as an oxidizer and vaseline as a stabilizer. This proved more stable than the earlier propellants and became the basis for all subsequent propellants in use until the end of World War I and the dissolution of the Austo-Hungarian Empire. Over the next two decades, the percentages of ingredients of this propellant were changed several times but all were known as M.97 with a letter suffix indicating the change.

The table below shows the composition of these propellants - percentages given in official documents do not always add up to 100%.

M.93, M.97d, M.97e and M.97h were produced prior to 1914 but we have been unable to find details on their composition.

The chemical composition of the M/97a propellant manufactured in Blumau differed slightly from the one made by the Dynamit Nobel Pozsony (Bratislava). The nitroglycerin content of the Blumau powder was a little higher than that of the Pozsony powder.

The use of barium nitrate in the M.97 series gave their muzzle flashes a greenish tint.

Almost all propellants were manufactured in the form of hollow tubes (Rohrenpulver). Rohrenpulver was used in most guns 12 cm and larger but at least in the early 1900s 15 cm guns used propellants in strip form (Bandpulver).

Cordite was widelyused by the British with Mark I being the first version produced,with manufacturing starting in 1889. This propellant was much morepowerful and thermally efficient than gunpowder or brown powder, as shownby tests with early British 6 inch (15.2 cm) QF guns. These gunsreplaced their 55 lbs. (25 kg) charge of brown prismatic powder with only13 lbs. (6 kg) of the new Mark I cordite propellant. Mark I corditeconsisted of 37% nitrocellulose (13.1% Nitrogen), 58% ntroglycerin and5% petroleum jelly. This last ingredient had originally been usedas a lubricant during the manufacturing process, but it was found thatit also acted as a stabilizer as its unsaturated hydrocarbons counteractedthe byproducts of the decomposition process.

As can be easilyguessed by the name, Cordite was primarily manufactured in thin cylindricalor cord form, with the different sizes denoted by a number representingthe hole diameter of the extrusion die. For Mark I cordite, thesenumbers were in 0.010 inch (0.254 mm) increments. For example, Cordite30 meant Cordite Mark I extruded through a die having holes 0.300 inches(7.62 mm) in diameter. It should be noted that using propellant incord form means that the burning surface decreases as the propellant burnsand that with hindsight it would have been better to adopt a tubular form,as was done in Germany. Tubular forms have a constant burning surfaceand thus produce more gas to fill the expanding volume as the projectiletravels up the barrel.

Cordite Mark I wasfirst issued for 3-pdr, 6-pdr, 4.7-inch and 6-inch guns in 1893 and for12-inch guns in May 1895. Generally, the larger the gun, the largerthe cord sized used. For example, the 12" (30.5 cm) Mark VIII andIX guns used Cordite 50, the 6" (15.2 cm) guns used Cordite 30and the Hotchkiss 3-pdr guns used Cordite 5.

Mark I cordite didburn very hotly and this was found to be detrimental to gun barrel life,as the high temperatures caused rapid wear. For this reason, theproportions of ntroglycerin and nitrocellulose were revised in orderto increase the barrel life. This new propellant was designated MD(for Modified) and it came into service in 1901. MD cordite consistedof 65% nitrocellulose (13.1% N), 30% ntroglycerin and 5% petroleum jelly.MD charges were about 25% heavier than Mark I for the same ballistic resultbut doubled the life of the guns. MD did have a high shrinkage rateduring the drying process, with cords that were extruded at 0.45 inches(1.14 cm) in diameter shrinking down to as little as 0.34 inches (0.86cm) after they dried. A tube form was made for at least the 4-inch(10.2 cm) QF Mark III, but most guns still used the cord form. LikeMark I cordite, the different sizes of MD were denoted by a number representingthe hole diameter of the extrusion die and the numbers were in 0.010 inch(0.254 mm) increments. The most common sizes were MD4.5, whichwas used for 3-pdr guns, MD8, MD11, MD19, MD26,MD37, which was used for 9.2-inch (23.4 cm) guns and MD45which was used for the 12-inch (30.5 cm) and larger guns. A largerdiameter MD55 cord was tried as this would have been advantageousfor the larger caliber guns, but it was found to be impossible to removeall of the volatile solvent.

Both Mark I and MDwere in use during World War I, and both had poor storage characteristicswith their stability degrading over time. A study performed afterWorld War I found that MD tended to form highly unstable micro-sized dustparticles consisting of nitrocellulose and iron pyrites. These unfortunatetraits led to several ships suffering magazine explosions during WorldWar I, both in action and in harbor.

By April 1917 considerableimprovements had been made in the manufacture of cordite by changing tothe use of clean carded sliver cotton, substituting cracked mineral jellyfor petroleum jelly, using guncotton which had been nitrated for a minimumof 2.5 hours and in using inspectors for quality control at all stagesof the process. This improved propellant was known asMC (forModified Cracked) and the substitution of cracked mineral jelly in placeof petroleum jelly was in a bid to improve stability. With this exception,MC cordite was chemically similar to MD cordite. Plans were put inplace during the spring of 1917 to replace some 6,000 tons (6,100 mt) ofold cordite with MC cordite as soon as production permitted. However,after the battleship Vanguard exploded in harbor in July 1917, this programwas expedited and the exchange was completed in ships of the Grand Fleetby March 1918 and in all ships by September 1918. MC cordite wasa fairly satisfactory propellant if properly and carefully made and itwas still in use during World War II, primarily as an alternative propellantfor certain guns.

In 1927, followinga study of the GermanRP C/12 solventless propellant (see below)used during World War I, British chemists developed a more stable versionof cordite called SC (solventless cordite, also known as solventlesscarbamite). This was used to replace the older propellants as rapidlyas possible and remained in service until well after World War II.SC was primarily manufactured in cords (strings) but some was also madein tubular form. The nomenclature was changed such that the corddie hole diameter was now given in 0.001 inch (0.0254 mm) increments.SC consisted of 49.5% nitrocellulose (12.2% N), 41.5% ntroglycerin and9% centralite (also known as "carbamite"), which was used as a stabilizer.Centralite not only improved the stabilization of SC cordite, it did nothave to be removed during the manufacturing process, which gave it betterdimensional stability as well. This also permitted the use of largerdiameter cords, with the largest being SC500 which was used forthe 14-inch Mark VII guns at Dover for cross-channel firings. However,SC was a stiff material to extrude and needed much higher pressures thandid the Cordite MD type. SC was used extensively during World War II and had a better safety record than did the previous cordites, although the loss of HMS Hood may be partially attributed to it.

A hotter burning propellant known as HSC (for Hot Solventless Carbamite) or HSCT (for Hot Solventless Carbamite Tubular) for 6-pdr, 3-pdr and 2-pdr guns was also produced. This was composed of 49.5% nitrocellulose, 47% ntroglycerin and 3.5% centralite.

Cordite W was introduced about 1935 and was extensively used for Bofors 40 mm ammunition for the early part of World War II. This burned hotter than SC and was composed of 65% Nitrocellulose, 29% Nitroglycerin, 3% Mineral Jelly (Vaseline) and 2% Carbamite.

Due to the presenceof calcium in the small amount of chalk used to counteract traces of residualacids, SC cordite had a very bright "flash," a characteristic which ledto the development of flashless propellants. British flashless propellantsin use during World War II were produced in primarily in slotted tubularform. The most used was NF, originally known as NFQ,and this was composed of 55% picrite (nitroguanidine), 16.5% nitrocellulose(12.1% N), 21% ntroglycerin, 7.5% centralite and 0.3% cryolite.NF was not easy to make and the basic initial material required for picritewas calcium carbide, which required large amounts of electricity duringthe manufacturing process. For this reason, the only plant makingthis propellant was located at Welland near Niagara Falls in Canada.Canada also producedCordite N during World War II which was widelyused as a propellant for aircraft gun ammunition. Cordite N is anothertriple-base propellant that was very cool burning and produced little smokeand almost no flash. The composition was 55.0% nitroguanidine, 19.0%nitrocellulose, 18.5% nitroglycerin and 7.5% ethyl centralite. CorditeN does not appear to have been used as a naval gun propellant in the RoyalNavy, but a variation of it was used by the USN (see below).

Flashless propellantwas in great demand during the war, however, for guns larger than 5.25"(13.3 cm), full flashless charges became too bulky for existing turretarrangements and so the only larger weapon issued these was the 6" (15.2cm) Mark XXIII. These were actually "reduced flash" or "non-blinding"charges and were designated as NQFP. This propellant was issuedin cord form and differed from NF by having 4.5% more nitrocellulose, 4.5%less centralite and 2% potassium sulfate.

As noted above, Britishcordite propellants were designated by the type and a number representingthe hole diameter of the extrusion die. For Mark I, MD and MC formulations,these numbers were in 0.010 inch (0.254 mm) increments and for SC corditethey were in 0.001 inch (0.0254 mm) increments. For example, MD45meant MD-type cordite manufactured with dies having 0.450 inch (11.4 mm)diameter holes while SC350 meant SC-type cordite manufactured withdies having 0.350 inch (8.89 mm) diameter holes.

Propellant grainsmade in the form of tubes were designated by the type of propellant followedby two numbers, with the first number indicating the external diameterand the second the internal diameter, both in 0.001 inch (0.0254 mm) increments.SC in tubular form was designated in the form ofSC T 100-40.HSC and HSCT designations were in the form ofHSCT/K 134-055 withthe K indicating that potassium cryolite was used as a moderator.NF designations were of the form NF 164-048.

The nominal diameterof the Japanese cords was given in units of 0.1 mm (0.004"). Forexample, the Japanese propellant 80DC was cordite with cords of8.0 mm (0.315") diameter.

By 1896 the USN hadbegun small-scale production of a single-base nitrocellulose propellantat Newport, Rhode Island. Major manufacturing of this "smokelesspowder" SP at the Naval Ordnance Station (later known as the NavalPowder Factory), at Indian Head, Maryland was begun in 1900 and continuedthere for decades.

Smokeless powderwill deteriorate over time as it contains nitrocellulose and two volatilesubstances, ether and alcohol. Its length of usefulness depends largelyon the conditions under which it is stowed. Moisture or heat speedsits deterioration and the combination of the two is extremely damagingto the propellant. In 1905, George Patterson, the key civilian researcherat Indian Head, was experimenting with the addition of rosaniline dye tothe propellant, designating these lots as SPR. This dye didnothing to stabilize the deterioration of the propellant, but instead showedthe status of the deterioration by changing color as it combined with theforming acids.

Patterson recommendedthe abandonment of rosaniline dye in 1908 in favor of adding diphenylamineas a stabilizer. Known as SPD, this new propellant was firstproduced in 1908 and adopted as the standard propellant formulation by1912. SPD was found to have good stability characteristics when properlystored, with some lots manufactured prior to World War I staying in storagefor as long as twelve years without loss of stability. During WorldWar II, the primary USN propellant was SPD in a multi-tube form made upof 99.5% nitrocellulose (12.6% N), 0.5% diphenylamine. The USN useda flat, short cylindrical grain design that usually had seven perforationswith the websize varying from 0.023 in (0.58 mm) for the short 3 in (7.62cm) gun to about 0.174 in (4.42 mm) for the 16 in (40.64 cm) guns.SPD had a good safety record partly due to the harder-to-ignite and slowburning nature of its single-base nature and partly due to the qualityof its manufacturing process.

In the mid-1920's,both the Naval Powder Factory at Indian Head and the DuPont Co. developedflashless powders. The Powder Factory had also obtained good resultsby mixing flash-reducing chemicals with the conventional powder charge.Flashlessness, however, was gained only by an increase in the amount ofsmoke, which was unacceptable to the fleet as it interfered with searchlightillumination and fire control. By 1928, BuOrd had stopped work onflash suppression. With the advent of radar in World War II, smokebecame less objectionable and the fleet was willing to accept considerablymore smoke in order to obtain a significant reduction in flash. Atthe time the request for flashless powder was received, BuOrd had alreadyaccumulated large inventories of smokeless powder. In order to preventthis material from being discarded, some means of converting it into acceptableflashless charges had to be found.

By the summer of1942, the Naval Powder Factory had the answer in a chemical tablet madeof a mixture of potassium nitrate and potassium sulfate, to which was addeda small amount of graphite to facilitate pelleting. After extensivetesting by the Naval Proving Ground had worked out the details, productionwas begun in September 1942. The use of these flashless pellets waslimited to guns between 3 to 6 inches (7.62 to 15.2 cm) as larger caliberswould have required too many pellets. Even in these calibers performancewas not always perfect. A fused mass of clinkers could form in thegun chambers, a result of incomplete combustion of the pellets. Athigh angles of gun elevation, these clinkers could cause gun casualtiessuch as jammed breech mechanisms. To eliminate the hazard, the ResearchDivision of BuOrd, working with the Naval Powder Factory, developed a flashlessgrain. Known as SPDF, this new material consisted of 5 to7 percent potassium sulfate mixed with nitrocellulose, colloided as a normalsmokeless powder, and extruded in the form of a powder grain. Satisfactoryin both ballistic and flash suppression properties, flashless grains ofthis type were in production at the Naval Powder Factory when the war ended.Meanwhile, pellets continued to serve the need for a flash suppressor forexisting propellants. While not completely satisfactory, these twocompositions provided the fleet with an essentially flashless charge longbefore it was possible to have true flashless powder.

During World WarII some Cordite N (see above) flashless propellant was importedfrom Canada and this was used for full charges for at least 6 inch (15.2cm) and 8 inch (20.3 cm) guns and in reduced charges for 16 inch (40.6cm) guns during the war and for other guns afterwards. Known as SPCGin USN service, the composition of this propellant differed from BritishNF and consisted of 19.0% nitrocellulose (13.1% N), 18.7% ntroglycerin,55% nitroguanidine and 7.3% centralite. BuOrd was unhappy with thispropellant, as Cordite N was brittle and, even worse, it contained ntroglycerin,which the USN considered to be highly undesirable for use in naval propellants.BuOrd instituted a major research program to develop a flashless propellantthat did not use ntroglycerin. After testing dozens of possibilities,scientists narrowed the field to two likely candidates - dinitrodiethanolnitramine (DINA) and Fivonite. Experimental firing at Dahlgren showedlittle difference between the two, but DINA was selected because of itssuperior physical properties.

Albanite,the name given this new flashless powder because of its white color, appearedto have all the desirable features of Cordite N and few of the objectionableones. Studies of Albanite by DuPont demonstrated the feasibilityof large-scale production, and by V-J Day BuOrd had launched an ambitiousprocurement program which called for monthly deliveries of 4,000,000 poundsof the new propellant. Albanite was composed of 20.0% nitrocellulose(12.6% N), 19.5% DINA, 55.0% nitroguanidine, 4.0% dibutyl phthalate and1.5% centralite. To this mixture was added a small amount of potassiumsulfate and lead which acted as a decoppering agent. These chargesweighed about 10% more than those for nitrocellulose.

In the early 1950sexperiments with a solventless propellant known as NOSOL progressedinto the current formulations of single-base propellant known as "NavyCool" or NACO which is composed of 91% nitrocellulose (12.0% N),1% ethyl centralite, 3% butyl stearate, 1% basic lead carbonate, 1% potassiumsulfate and 3% volatiles.

The cancelled ERGM rocket projectile was to use a special mixture known as EX-99 propellant which, according to one open-source document, is composed of 76% RDX (cyclonite, cyclomethylene trinitramine), 12% cellulose acetate butyrate (CAB), 7.6% acetal/formal (A/F), 4% nitrocellulose and 0.4% ethyl centralite. The high percentage of RDX gives this propellant the unusually high "kick" necessary for this relatively heavy projectile and is one of the reasons why the 5"/62 (12.7 cm) gunhouse was greatly strengthened over the earlier 5"/54 (12.7 cm) gunhouse.

The designations below are normally followedby a number that indicates the sequence of manufacture. The combinationof the letters and the number is termed the index or the lot of the powder.

SP - Smokeless Powder, the original single-based propellant adopted by the USN around 1896

SPR - Smokeless Powder with Rosaniline dye, in service with the USN for a brief period between 1905 and 1908

SPD - Smokeless Powder with Diphenylamine as a stabilizer, adopted by the USN in 1908

SPDB - A blend of diphenylamine stabilized powders of different lots. The purpose of blending is to provide a uniform index of ample size and desired characteristics from smaller remnant lots.

SPDF - A flashless formulation of SPD

SPDN - SPD with nonvolatile materials added to reduce its hydroscopic tendencies. The N stands for nonhygroscopic.

SPDW - Reworked propellant intended for target use. Propellant is ground down, reprocessed and then made into new grains.

SPWF - Reworked propellant to which a flashless element has been added

SPDX - Water-dried SPD

SPC - Smokeless Powder with Carbamite (ethyl centrality) added for stability

SPCF - A flashless formulation of SPC

SPCG - Flashless triple-based propellant stabilized with carbamite. The G is short for NG, the designation for Nitroguanidine.