'-f Order No. T-39882(G) Manned Spacecraft Center NASA, Houston, Texas I I (ACCESSION NUMBER) (THRU) I I' EXPLOSIVES RESEARCH CENTER EXPLORATORY STUDY OF HYPERGOLIC IGNITION SPIKE PHENOMENA GPO PRICE $ Phase II, Part II CFSTI PRICE(S) $ July 1 to September 30, 1966 ~ Hard copy (HC) '1 ,, Microfiche (MF) ~6k ff 653 July 65 BUREAU OF MINES, PITTSBURGH. PA. ,.hWlCAC LIBPAXY BUILDING 45 T!?C !-!N I h: A L !? 4 RY FEB 16 1967 Manned Spacecraft Center Houston, Texas 77058 UNITED STATES DEPARTMENT OF THE INTERIOR UNITED STATES DEPARTMENT OF THE INTERIOR BUREAU OF MINES Pittsburgh, Pennsylvania EXPLORATORY STUDY OF WPERGOLIC IGNITION SPIKE PHENOMENA . Phase 11, Part I1 July 1 to September 30, 1966 by Theodore Christos Yael Miron Harry James Henry E. Perlee APPROVED : David Burgess (Actid) Robert W. Van blah Research Director Explosives Research Center Bureau of Mines 4800 Forbes Avenue Pittsburgh, Pennsylvania 15213 for Manned Spacecraft Center National Aeronautics & Space Administration Houston, Texas EXPLORATORY STUDY OF HYPERGOLIC IGNITION SPIKE PKENOMENA Phase 11, Part I1 July 1 to September 30, 1966 INTRODUCTION During recent test firings of Aerozine-50/nitrogen tetroxide 100-pound thrust engines at environmental pressures of about 0.005 psia, Manned Spacecraft Center (MSC) Personnel observed the formation and accumulation of a residual material on the engine's diffuser bell. Chemical analyses of this material, supplied to the Bureau of Mines by MSC, has subsequently shown it contains water, hydrazine nitrate, and other unidentified compounds. Since these residues apparently contain an appreciable amount of hydrazine nitrate, an explosive material, it has been suggested that these residues could be contributing to the pressure spikinb ,phenomena often observed during ignition of the engines at attitude. On July 7, 1966, the Bureau of Mines agreed to conduct, as part of its experimental program, an exploratory study of the physical and com- bustion characteristics of hydrazine nitrate and its water solutions. It is believed this information will permit a more critical evaluation of the potential hazard in the engines. Table 1 lists the suggested experimental studies as outlined and agreed upon at the July 7 conference. TABLE 1. - Suggested studies of the physical and combustion charac- teristics of hydrazine nitrate and its solutions. Physical Properties Combustion Characteristics Viscosity Critical film detonation Surface tension thickness Vaporization rate Shock and impact sensitivity Phase diagram Detonation parameters Thermal stability This r.eport describes the results of the physical and combus- tion characteristic study and in addition, the residue chemical analysis. The first section contains the results of the chemical analysis of the engine post shutdown residues received from MSC. The second section discusses the physical characteristics of hydrazine nitrate and its per- tinent solutions. The remaining section contains the results of studies conducted at the Bureau and other laboratories concerning the combustion characteristics of these same systems. EXPERIMENTAL STUDIES Materials The hydrazine nitrate used in these experiments was prepared by the procedure recommended by the Thiokol Corporation in their report RMD 239-ql (Period June-September 1958, Contract No. as 58-644C). The nitric acid used in this preparation was A.C.S. grade with a purity of 70 percent; the hydrazine was purchased from Olin Mathieson Chemical Corporation with a stated purity of 97.5 percent. The methanol used for recrystallizing the hydrazine nitrate was a Reagent Grade product with a purity of 99.9 percent. Commercial distilled water was used in preparing the various solutions. Residual Analvsis The residues were obtained by MSC personnel following engine shutdown from various locations in the environmental chamber and rocket engine. The samples received from MSC were divided into two equal por- tions, one for immediate analysis and the other was reserved for use in case of accidental loss of the first sample. The first sample was freeze-dried at a pressure of about 0.1 psia, thereby separating it into solid and liquid portions. The liquid portions were water clear, and the solid portions, a dark straw color. The liquid portion was analyzed by a gas-liquid chromatograph using a 3-foot column of Carbowax 1540 at a temperature of 113°F. The solid portion was mixed with potassium bromide and pressed into a pellet for infrared analysis. Table 2 shows the results of these analyses conducted on the various samples to date. Physical and Thermochemical Characteristics To understand the role of hydrazine nitrate (HN) in the hard start phenomena, it is pertinent to have available information concerning its physical and thermochemical characteristics. In this regard, several literature searches were conducted for the Bureau by The Chemical Pro- pulsion Information Agency and Defense Documentation Center. Table 3 contains a list of the known physical and thermochemi- cal properties of HN. As shown in the table, there exists two crystal- line forms of HN, and cy and the p. The f3 form melts at 158"~with no apparent decomposition or sublimation. Robinson and McCroneg found that the resulting melt supercools readily and usually crystallizes as the cy form. However, on seeding the (y form with fl crystals, it reverts to the /3 form at a rate which decreases with decreasing temperature. Due to the unstable nature of the cy form, it has not been possible to determine from the MSC residue samples whether this or the f3 form is actually generated in these engines. Furthermore, these authors found no indi- cation of any additional thermal (phase) changes in the crystalline 2 $2- om a, a, P P cd cd k k P v i2 a.rl 00 a0 Gcn dcn -4 A .ti A N N a2 h %X X onn aocu cnnom cn rnJ c; cn rr) cn M 31 0 -2 0 rl k a, P E! ld d 4 0 a, rl N N ,2 0 P h, x xa, V 0 2 2 cu cu cu cu rl I-i rl rl M \ \ 1 \ r- t- r- -2 a3 0 cu rl rl TABLE 3. - Physical and thermal chemical properties of hydrazine nitrate. Formula weight 95.06 Density (X-ray) 95.35 lb/ft3 Melting point CY form 159°F fl form 144OF Heat of formation +lO7,000 Btu/mole Heat of solution -l5,7OO Btu/mole Heat of decomposit Lon -15,900 Btu/lb Combus tion temperature 4, 350°F 4 structure of HN between -94°F and the melting point; the system is therefore probably monotonic. These results are in accord with results of similar w rk conducted at the Bureau, using a differential scanning calorimeter29 . Moisture absorption experiments were conducted on HN by Meaard3l using various Regnault mixtures (sulfuric acid of 11" Be, 21" Be, and 31" Be) to obtain various water vapor pressure environments. Figure 1, repro- duced from Medard's report, shows the results of these experiments. The figure shows that at 60"~HN will absorb moisture from an environment at 90 percent relative humidity at a rate of 0.01 pounds of water per pound of HN per day. Medard also examined the weight loss of anhydrous HN during intermittent heating to 230°F for a period of 315 hours (apparently the author attributes this weight loss to thermal degradation). He found this loss to be linearly dependent,with time, amounted to a loss of about 0.005 weight percent per hour. Kissingerag , in similar work, found that the HN decomposition at 280'~ is "barely noticeable by the standard vacuum stability technique." He also reported that it can be stored under 95 percent ethyl alcohol at a maximum temperature of 86°F for as long as four months wi hout any "apparent ill effects." Shidlovskii, Semishin, and Simutird in their work observed "an intense thermal decom- position of HN at 392-428°F and a flash at 518"~."This latter obser- vation seems to be in accordance with the Bureau's results where impur HN was found to decompose explosively at a temperature of about 518"F2J . The solubility of HN in water and in hydrazine has been studied ber of investigators; among these Corcoran, Kruse, Skolnik, and Lieber6by a nY conducted the most extensive study. Their results for the three component system HN-water-hydrazine are shown in figure 2. The concen- tration triangular grid has not been included in the figure to avoid obscuring the pertinent features of the phase diagram structure. The figure shows the isothermal contours for the liquidous surfaces of the ternary system and also shows that the system has four invariant points: two ternary eutectics, a ternary peritectic, and the eutectic of the quasi-binary system hydrazine hydrate (hydrazine nitrate-1-hydrazinate). Figures 3 and 4 show the liquidous lines for the HN-water and HN-hydra- zine binary systems drawn from the results shown in figure 2. Figure 4 indicates the formation of the compound hydrazine nitrate-1-hydrazine (N,H,NO, .NE&) which melts at 37.4"F and the eutectic composed of 47.: weight percent Hw which melts at -50.8"~. The data used to prepare these curves can be found in the author's original papers. It is inter- esting to note (figure 3) that HN does not form a hydrate, although several authors reported that HN exhibits hydroscopic characteristics. It is also interesting that, although water solvates with hydrazine (figure 1) and hydrazine hydrates with HN (figure 4), water does not hydrate with HN. 5 Another binary system of interest in this irive:stigation wa:; HN and ammlsniurn nitrate, materials that were reported liy v.ltrious inves- tigators to be products of the reaction between hydrazine and nitrogen tetroxide7, 8, 9/. Barlot and MarsaulelO/ examined the phase re1at)icnship for this system; their results are shown in figure 5.