|Agena Engine - |
Credit: Bell. 24,273 bytes. 397 x 248 pixels.
Drawing on the German World War II Wasserfall rocket, nitric acid (HNO3) became the early storable oxidiser of choice for missiles and upper stages of the 1950's. To overcome various problems with its use, it was necessary to combine the nitric acid with N2O4 and passivation compounds. These formulae were considered extremely secret at the time. The propellant combinations WFNA/ JP-4 and later IRFNA/JP-4 were the first storable systems given serious consideration in the United States. Problems which caused the abandoning of these propellants were the absence of reliable hypergolic ignition and unstable combustion. IRFNA/UDMH and IRFNA/JP-X finally did prove satisfactory.
By the late 1950's it was apparent that N2O4 by itself was a better oxidiser. Therefore nitric acid was almost entirely replaced by pure N2O4 in storable liquid fuel rocket engines developed after 1960. The composition of propellant-grade nitric acids is covered by Military Specification MIL-N-7254. The nitric acids are fuming liquids which vary from colorless to brown, depending on the amount of dissolved N2O4. The vapours from these acids have a characteristic pungent odour. They are highly corrosive, toxic, oxidising agents and attack most metals. They react with most organic materials violently enough to cause fire. The acids are soluble in water in all proportions, with an accompanying evolution of heat. They cannot be made to explode. Approximately 90 per cent of the nitric acid is made by the catalytic oxidation of ammonia with air or oxygen to yield nitric oxide (NO). The latter is oxidised to N2O4 which, when treated with water, yields nitric acid (HNO3) and may be concentrated by distillation with sulphuric acid. Red fuming nitric acids may be produced by passing gaseous N2O4 into nitric acid, a slight modification of the above process. Production of nitric acid was estimated at 3 million tonnes in 1959. The price of RFNA was $ 0.20 per kg in drum lots; IRFNA was slightly higher. The varieties of nitric acid propellants include:
Unsymmetrical Dimethylhydrazine ((CH3)2NNH2) became the storable liquid fuel of choice by the mid-1950's. Development of UDMH in the Soviet Union began in 1949. It is used in virtually all storable liquid rocket engines except for some orbital manoeuvring engines in the United States, where MMH has been preferred due to a slightly higher density and performance. Unsymmetrical dimethylhydrazine (UDMH) is 98 to 99 per cent pure and is described by Military Specification MIL-D-25604. The normally expected impurities are dimethylamine and water. UDMH is a clear, hygroscopic liquid which yellows on exposure to air. It absorbs oxygen and carbon dioxide. UDMH is a toxic volatile liquid. It exhibits the sharp ammoniacal or fishy odour which is characteristic of organic amines. It is completely miscible with water, ethanol, and most petroleum fuels. It is not shock sensitive. The vapours are flammable in air over 2.5 to 95 per cent concentration range. UDMH can be produced commercially by nitrosation of dimethylamine, to N-nitro-sodimethylrtmine, followed by reduction of the intermediate to UDMH and subsequent purification. UDMH can be prepared, also, by a modification of the Raschig process (see discussion of hydrazine), in which the chloramine intermediate is with dimethylamine rather than with ammonia. The price in 1959 for tank-car quantities was under $ 1.00 per kg. Engineering studies indicated a price of $ 1.00 per kg with large scale sustained production. But due to its toxic nature, production and transport costs soared in response to environmental regulations. By the 1980's NASA was paying $ 24.00 per kg.
|Eng-engineslink||Thrust(vac)-kgf||Thrust(vac)-kN||Isp-sec||Isp (sea level)-sec||Designed for||Status||RM-100B||45||283||KDU-414||200||1.96||272||Upper Stages||Out of Production||Isayev DOS-3/4||400||3.92||Upper Stages||Out of Production||KTDU-35||417||4.09||280||Upper Stages||Out of Production||KTDU-53||417||4.09||280||Upper Stages||Out of Production||KTDU-66||417||4.09||280||Upper Stages||Out of Production||KTDU-417||1,929||18.92||314||Upper Stages||Out of Production||RD-851||3,310||32.48||279||243||First Stages||Out of Production||AJ10-118D||3,436||33.70||278||160||Upper Stages||Out of Production||AJ10-118||3,447||33.80||271||150||Upper Stages||Out of Production||AJ10-101||3,500||34.30||270||240||Upper Stages||Out of Production||AJ10-104||3,579||35.10||278||Upper Stages||Out of Production||AJ10-118E||3,579||35.10||278||Upper Stages||Out of Production||AJ10-118F||4,218||41.40||306||Upper Stages||Out of Production||AJ10-118H||4,427||319||AJ10-118G||4,427||314||RD-852||4,920||48.25||255||Upper Stages||Out of Production||Bell 8048||7,031||68.90||276||Upper Stages||Out of Production||Bell 8081||7,257||71.20||285||Upper Stages||Out of Production||Bell 8096||7,257||71.20||300||Upper Stages||Out of Production||Nodong||14,718||144.00||255||232||First Stages||In Production||11D49||16,060||157.50||303||Upper Stages||In Production||YF-2A||31,218||306.10||268||241||First Stages||In Production||Von Braun-3||40,000||392.30||286||230||Upper Stages||Study 1952||Von Braun-2||47,058||461.50||286||230||Upper Stages||Study 1952||RD-853||47,682||467.60||301||Upper Stages||Developed 1960-63||U102-000||47,723||468.00||307||Upper Stages||Out of Production||AJ10-33||52,000||RD-215||88,100||864.00||291||248||First Stages||Out of Production||RD-217||88,200||865.00||289||246||First Stages||Out of Production||RD-219||89,950||883.00||293||Upper Stages||Hardware||RD-225||90,653||889.00||294||251||First Stages||Out of Production||RD-220||109,518||1,074.00||306||270||First Stages||Developed 1960-||RD-221||114,004||1,118.00||318||Upper Stages||Developed 1960-||RD-222||166,622||1,634.00||302||272||First Stages||Developed 1960-61||RD-223||173,046||1,697.00||314||Upper Stages||Developed 1960-61||RD-216||177,400||1,728.00||291||248||First Stages||In Production||RD-224||181,306||1,778.00||294||251||First Stages||Out of Production||S5.45||200,000||1,961.00||267||Upper Stages||Out of Production||RD-218||266,000||2,592.00||289||246||First Stages||Out of Production||Von Braun-1||311,764||3,057.30||286||230||First Stages||Study 1952|