Burning Rate Modifiers to Tailor Combustion of ADN/AN-Based Solid Propellants

This paper presents a study, carried out in the framework of the H2020 european project GRAIL, on thermal and catalytic decomposition of a solid ADN/AN mixture. Decomposition pathways of the mixture are proposed thanks to thermal analyses coupled with mass spectrometry. Thirty-four burning rate modifiers have been investigated using thermal analyses. This led to the selection of five candidates considered as promising additives: nano-CuO, CuO, Cr2Cu2O5, ZnO and ferrocene. Finally, a bicatalytic system with nano-CuO and ferrocene was considered for possible improvement of the decomposition. It prove to display a much attractive behavior towards the decomposition of this oxidizer mixture

Improving the Mechanical Properties of Composite Rocket Propellants

Solid composite rocket propellants usually contain ammoniumperchlorate embedded in an elastic polymer binder. The bindercan be based on a liquid prepolymer such as hydroxyl-terminatedpolybutadiene, HTPB, or poly(3-nitratomethyl-3-methyl oxetane,PolyNIMMO. HTPB is today widely used for this purpose whereasPolyNIMMO has not yet found its way to an application. Bothprepolymers can be cured with diisocyanates to formpolyurethane rubber, yielding solid and elastic rocketpropellants. It is essential that the solid propellant has goodmechanical properties to ensure that the rocket will perform asintended. The propellant must also retain its elasticproperties down to the minimum service temperature and thus alow glass transition temperature is important. In fact, themajor cause of failure of solid rocket motors is linked to themechanical properties of the propellants. HTPB has a very lowglass transition temperature but in some applications itstensile strength is insufficient. PolyNIMMO, on the other hand,has too high a glass transition temperature and a suitableplasticizer is needed. The purpose of this work is to increasethe knowledge of the mechanical properties of polymers bystudying how to increase the tensile strength of HTPB and howto decrease the glass transition temperature of PolyNIMMO. The tensile strength of HTPB was studied by increasing thehard segment content, 1,4-butanediol and 1,4-cyclohexanedimethanol being used as chain extenders. The materials werecrosslinked with either isophorone diisocyanate,1,6-hexamethylene diisocyanate or dicyclohexylmethane4,4'-diisocyanate. The results show that the tensile strengthincrease strongly with the addition of up to two moles of diolper mole HTPB. The highest tensile strength was obtained byusing dicyclohexylmethane 4,4'-diisocyanate and1,4-butanediol. The depression of the glass transition temperature ofPolyNIMMO was studied by using a new energetic plasticizer,2,2-dinitro-1,3-bis-nitrooxy-propane. Two commercial energeticplasticizers, namely bis(2,2-dinitropropyl) acetal/formal andN-N-butyl-N-(2-nitroxy-etyl)nitramine were used for comparison.2,2-Dinitro-1,3-bis-nitrooxy-propane andN-N-butyl-N-(2-nitroxy-etyl)nitramine were found to interactstrongly with PolyNIMMOand they were thus very effective inlowering the glass transition temperature.Bis(2,2-dinitropropyl) acetal/formal on the other hand was noteffective, and the depression of the glass transitiontemperature in this case was due only to dilution of thesample.QCR 20161026</p

Experiments for Collection and Characterization of Particles Exiting from Solid Propellant Rocket Nozzles

Metals in solid propellants are used to improve specific impulse and increment the energy density. Their combustion generates condensed products that move along the motor chamber and are expelled through the nozzle. The discharge of liquid or solid particles across the gas dynamic nozzle of large boosters is not only a matter of specific impulse loss. Recent climatological studies are addressing possible short and long term environmental effects that may be attributed to space launch activity by large launchers. In this respect, the knowledge of plume content and, specifically, of physical, chemical, and morphological properties of the exhausted particulate is needed. In the frame of the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) project, an activity financed by the European Space Agency, the Space Propulsion Laboratory (SPLab) of Politecnico di Milano developed a collection method and an analysis protocol for the characterization of the particles contained in the rocket plume. The collection is performed by an intrusive probe capable of capturing the particles directly from the nozzle exit and quenching them. The post-collection protocol enables size measurement, chemical characterization, and morphology observation. In this paper an overview of the collection and analysis activity is presented, along with the final results that were achieved by analyzing the plume of different rocket motors

Determination of fluid properties of the green propellant FLP-106 and related material and component testing with regard to applications in space missions

The obtained results of the work conducted within the scope of the GRASP project showed that the energetic ionic liquid FLP-106 is a very interesting candidate to substitute hydrazine in propulsion systems relevant for attitude control systems of satellites. Its properties show that it is in comparison to hydrazine also space storable, significantly simpler to use, environmentally more benign and shows better specific impulses. In comparison to LMP-103S the specific impulses and the density of FLP-106 are also higher. With the realized experimental durability test setup important information could be obtained. Several tasks could be identified for further investigation, which have to be solved on the way to show if FLP-106 has the potential to be used as a possible new monopropellant for future propulsion systems. It has also been proven that the FCV maintained its full functionality after the durability testing with FLP-106. An FLP-106 model thruster setup was realized and prepared for hot fire testing. The conducted pre-tests gave significant information for the proper test campaign within a subsequent research program to GRASP. Summarizing FLP-106 is a very interesting candidate and could have the potential to replace hydrazine in attitude control systems of satellites, but further detailed investigations have to be conducted to enhance the technology readiness level

Experimental Modeling of Alumina Particulate in Solid Booster: Final Report

The ESA-EMAP project (Saile et al., 2019) is dedicated to the experimental modeling of alumina particulates in solid boosters. The motivation roots in the uncertainty regarding the impact of the alumina particles emitted by the solid rocket motors (SRMs) of European launch systems on the ozone depletion in the stratosphere. This uncertainty needs to be addressed in the face of the expected growth and significantly increased number of rocket launchers as predicted in studies associated with the new space era. For this reason, the ESA-EMAP project focused on the experimental investigation of the particle formation processes and the quantification of the corresponding flow conditions by means of sub-scale tests. The particle formation was assessed from the combustion chamber throughout the nozzle to its final state as it would be expected in the atmosphere. These tests were executed with a solid rocket motor (SRM) mimicking a launch system and operating under flight-realistic conditions with an ambient flow. As it can be seen in fig. 1, this task was accomplished by integrating the rocket motor into a subsonic wind tunnel nozzle of the ’Vertical Test Section Cologne’ (VMK). Numerous measurement techniques were applied to capture the flow conditions and formation of the particles. In detail, the high-speed schlieren measurements were applied to capture the density gradients and the topology of the jet. Spectroscopic measurement methods such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy, alumina emission measurement shed light on the exhaust gas composition and temperature distribution of the jet. The velocity was captured by means of particle image velocimetry, direct image particle size determination, and laser-2-focus (fig. 2). The heat release from the jet was assessed with a Gardon gauge and infrared thermography. Finally, the particle size (fig. 5) was quantified by means of measurements with an aerodynamic particle sizer and rocket plume collector (Maggi et al., 2020). In summary, a vast data base on solid rocket exhaust plume was generated. At three different planes along the path line of the particles, there is now information available on the particle size, the particle velocity, the temperature distribution, the density gradient distribution, and the gas composition of the plume. That data base provides a foundation for further analytical explorations and provides the opportunity to validate models associated with the physics of solid rocket exhaust plumes

Overview to the ESA-EMAP Project: Characterization of SRM Plumes with Alumina Particulate in Subscale Testing

The current paper provides an overview of the ESAEMAP project. This project pursues activities regarding the experimental modeling of alumina particulates in solid boosters. The issue regards the particles residing in the atmosphere after the passage of a launch vehicle with solid rocket propulsion, which might contribute to local and overall ozone depletion. The question is to what extent since the particle size distribution left behind is essentially unclear. For this reason, the ESA-EMAP investigations focus on the characterization of the solid exhaust plume properties for well-defined combustion chamber conditions. Thus, details of the rocket motor assembly, of the developed solid propellant grains and of first measurement results are provided. The paper presents technical findings concerning the rocket motors and reveals aspects to the feasibility of the applied measurement techniques

Characterization of SRM plumes with alumina particulate in subscale testing

The current paper provides an outline and first results of the ESA-EMAP project. This project pursues activities regarding the experimental modeling of alumina particulates in solid boosters (EMAP). The issue regards the particles residing in the atmosphere after the passage of a launch vehicle with solid rocket propulsion, which might contribute to local and overall ozone depletion. The question is to what extent since the particle size distribution left behind is essentially unclear. For this reason, the ESA-EMAP investigations focus on the characterization of the solid exhaust plume properties for well-defined combustion chamber conditions. Thus, details of the rocket motor assembly, of the developed solid propellant grains, and of first measurement results are provided. The paper presents technical findings concerning the rocket motors and reveals aspects to the feasibility of the applied measurement techniques