Papers by Luciano Galfetti
The population of space debris in low Earth orbit is growing uncontrolled because of the collisio... more The population of space debris in low Earth orbit is growing uncontrolled because of the collisional cas-cading predicted by Kessler. This process is supported by the fragmentation of items already present into orbit due to explosions, collisions, or degradation. NASA predictions suggest that, if appropriate measures are not put into action, the space junk population can represent a threat for future manned and unmanned space missions. The reduction of fragment generation can be obtained only if current population is reduced by number. The action of active debris removal is currently on study but represents a far perspective. In the meantime, only mitigation measures can be enacted by the international community such as the correct disposal of space systems at the end of their operating life. In the present work a preliminary study on an active on-board deorbiting system for Cosmos 3M is reported. The system uses gasified propellant left-overs for the the disposal of the stage to an...
Progress in Propulsion Physics, 2009
The experimental results obtained within a joint international research e¨ort regarding the forma... more The experimental results obtained within a joint international research e¨ort regarding the formation of condensed combustion products from nanoaluminum-based solid propellants (SPs) are reported. Data on the size, structure, chemical composition, and quantity of condensed combustion products (CCPs) as well as conditions of their formation are discussed. On the basis of the collected experimental data, a general physical picture of condensed combustion products formation is portrayed. The results of this study allow carrying out the analysis of good quality propellants using nanoaluminum.
Modern Research Topics in Aerospace Propulsion, 1991
Modeling and stability of solid rocket propellant combustion waves, featuring spacewise thick fla... more Modeling and stability of solid rocket propellant combustion waves, featuring spacewise thick flames and characteristic gas phase time depending on pressure as well as temperature, are discussed. Within the usual framework of monodimensional deflagration and quasi-steady gas phase, this comprehensive approach is applied to double-base compositions by implementing an extended macrokinetics for the fizz-zone and a two-step distributed pyrolysis for the condensed phase. The proposed general model includes other models commonly accepted in the literature as particular cases and yields reasonable results over a large pressure range. Both the thickness of the flame and the temperature dependence of the characteristic gas phase time conspire against combustion stability but, being well understood, their influences can be fully settled. Exothermic thermal degradation of the condensed phase also strongly conspires against combustion stability, mainly in the super-rate burning region. It is found that distributed heat release in the high temperature degradation layer helps the static stability of super-rate burning, but worsens dynamic stability properties; in turn, this is improved by heat release distributed in the low-temperature degradation layer. Overall, properly partitioning the heat release removed from the surface concentrated layer to volumetrically distributed degradation layers sensibly augments intrinsic combustion stability. The results obtained may be sensitive to the data cited here. Nevertheless, the two-step consecutive pyrolysis mechanism deserves attention for all processes in which nitrate ester decomposition is relevant and in any case is a prerequisite for super-rate burning modeling.
43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2007
ABSTRACT
Progress in Propulsion Physics, 2009
Composite propellants feature a di¨usion §ame. The size of oxidizer particles leverage some combu... more Composite propellants feature a di¨usion §ame. The size of oxidizer particles leverage some combustion properties (mainly, burning rate and pressure sensitivity) along with §ame structure. Macroscopic combustion features are strictly related to those events occurring inside the gas phase and close to the burning surface. The §ame of nonaluminized composite energetic materials is considered and a simpli¦ed combustion model is tested for this case. Combustion of a laminate propellant with varying lamina size is simulated. The benchmark consists of some movies taken from ammonium perchlorate (AP) / hydroxyl-terminated polybutadiene (HTPB) propellant combustion with a high-speed video camera. Three di¨erent powder sizes are used in propellant manufacturing.
Progress in Propulsion Physics, 2009
Solid rocket propellants based on dual mixes of inorganic crystalline oxidizers (ammonium nitrate... more Solid rocket propellants based on dual mixes of inorganic crystalline oxidizers (ammonium nitrate (AN) and ammonium perchlorate (AP)) with binder and a mixture of micrometric-nanometric aluminum were investigated. Ammonium nitrate is a low-cost oxidizer, producing environment friendly combustion products but with lower speci¦c impulse compared to AP. The better performance obtained with AP and the low quantity of toxic emissions obtained by using AN have suggested an interesting compromise based on a dual mixture of the two oxidizers. To improve the thermal response of raw AN, di¨erent types of phase stabilized AN (PSAN) and AN/AP co-crystals were investigated. 1 BACKGROUND Ammonium nitrate, an inorganic solid oxidizer already used in rocket propulsion years ago, is still a widely employed oxidizer yielding, with common organic
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Progress in Propulsion Physics, 2011
47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2011
Solid fuels for hybrid rockets were characterized in the framework of a research project aimed to... more Solid fuels for hybrid rockets were characterized in the framework of a research project aimed to develop a new generation of solid fuels, combining at the same time good ballistic and mechanical properties. A rheological, mechanical and ballistic characterization of paraffin-based hybrid rocket solid fuels was performed, considering pure wax-based fuels and fuels doped with suitable metal additives. Nano-Al powders and metal hydrides (Magnesium hydride (MgH2), Lithium Aluminum hydride (LiAlH4)) were used as fillers in paraffin matrices. Results of this investigation show a strong correlation between the measured viscosity of the melted paraffin layer and the regression rate: a decrease of viscosity increases the regression rate. This trend is due to the increasing development of entrainment phenomena, which strongly increase the regression rate. Addition of Lithium Aluminum Hydride (mass fraction 10%) can further increase the regression rate up to 378% with respect to the pure HTPB regression rate, taken as baseline reference fuel. The highest regression rates were found for the Solid Wax (SW) composition, added with 5% MgH2 mass fraction; at 350 kg/m 2 s oxygen mass flux, the measured regression rate, averaged in space and time, was 2.5 mm/s, which is approximately five times higher than that of the pure HTPB composition. Compositions added with nano-sized Aluminum powders were compared with those added with MgH2, using gel or solid wax.
57th International Astronautical Congress, 2006
ABSTRACT This work describes some studies on hybrid propulsion performed at Space Propulsion Labo... more ABSTRACT This work describes some studies on hybrid propulsion performed at Space Propulsion Laboratory of Politecnico di Milano. Regression rate and ignition delay are the focus of the activities. A micro-sized hybrid rocket motor was designed to investigate the combustion behavior of different HTPB-based solid fuel compositions. Air and mixtures of oxygen and nitrogen (up to 40% of oxygen) were used as oxidizer, injected at the head-end of the motor. The oxidizer mass flux was changed in the range from 5 to 10 kg/m2-s, and the average chamber pressure from 3.5 to 6.5 bar. Preliminary experiments on ignition delay were run on a dedicated facility. Samples of aluminized and nonaluminized HTPB-based solid fuel were exposed to radiant flux in presence of an oxidizing atmosphere. Ignition was detected by means of a photodiode. The goal of the experimental activity is to investigate different formulations containing nano-sized energetic particles. In the present paper a micro 2-D hybrid configuration is used to determine aluminized fuel regression rate, not yet the micro rocket motor.
International Journal of Energetic Materials and Chemical Propulsion, 2008
ABSTRACT A micro-sized hybrid rocket motor was designed, built, and implemented to investigate th... more ABSTRACT A micro-sized hybrid rocket motor was designed, built, and implemented to investigate the comparative combustion behavior of a variety of solid fuel compositions. The goal of this experimental effort is to obtain a relative grading of different solid fuel ...
47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2011
This paper describes an optical time-resolved technique capable of measuring regression rates of ... more This paper describes an optical time-resolved technique capable of measuring regression rates of solid fuels for hybrid rocket propulsion under steady or unsteady operating conditions. Representative results for quasi-steady burning of HTPB- or paraffin-based formulations, loaded with a variety of energetic additives, are discussed. The standard constant power dependence on the oxidizer mass flux, commonly used in the literature, is found to underestimate the regression rates observed at the beginning of tests. Some preliminary results of unsteady regression from forced transient burning are also discussed. Nomenclature D a = multiplicative factor in Eq. 2, D n s mm / r a = multiplicative factor in Eq. 12, [ ] r n s kg/(m mm ) / 2 D = fuel grain diameter, mm 0 D = nominal initial diameter, mm i h D , = horizontal diameter (sampled discrete value), mm i v D , = vertical diameter (sampled discrete value), mm D = space-averaged diameter (fitted continuous value), mm i D = space-averaged diameter (sampled discrete value), mm ign D = space-averaged diameter at strand ignition, mm ox G = oxidizer mass flux, kg/(m 2 s)
Metal Nanopowders, 2014
Following a comprehensive literature survey about use of Al nanopowders in a range of HEM applica... more Following a comprehensive literature survey about use of Al nanopowders in a range of HEM applications — including rocket propulsion, pyrotechnics, and explosives - a through treatment is offered of the ideal and delivered thermochemical performance of the most interesting metallic ingredients to augment solid and hybrid rocket propulsion. The particular but fundamental class of nAl powders is then investigated in detail: critical issues such as coating and characterization of the powders, rheological and mechanical properties, combustion and ballistic behavior are all examined under a variety of operating conditions. Although attractive for fundamental studies and much used in laboratory experiments, no rocket propulsion operational systems are yet reported in use for nAl powders. Loss of active metal, cold cohesion, and poor propellant castability globally overcome advantages such as increased burning rate (easily achievable by other ways) and reduced specific impulse losses assoc...
Materials Science and Engineering: C, 2007
... Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and X-ray Photoelectron Spectros... more ... Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS), was performed in order to evaluate their performance in solid propellant. These aluminum powders were used in manufacturing composite rocket propellants, that are ...
Journal of Propulsion and Power, 2010
Experiments concerning the ballistic characterization of several nanoaluminum (nAl) powders are r... more Experiments concerning the ballistic characterization of several nanoaluminum (nAl) powders are reported. Most studies were performed with laboratory composite solid rocket propellants based on ammonium perchlorate as oxidizer and hydroxyl-terminated polybutadiene as inert binder. The ultimate objective is to understand the flame structure of differently metallized formulations and improve their specific impulse efficiency by mitigating the two-phase losses. Ballistic results confirm, for increasing nAl mass fraction or decreasing nAl size, higher steady burning rates with essentially the same pressure sensitivity and reduced average size of condensed combustion products. However, aggregation and agglomeration phenomena near the burning surface appear noticeably different for microaluminum (μAl) and nAl powders. By contrasting the associated flame structures, a particle-laden flame zone with a sensibly reduced particle size is disclosed in the case of nAl. Propellant microstructure is considered the main controlling factor. A way to predict the incipient agglomerate size for μAl propellants is proposed and verified by testing several additional ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum formulations of industrial manufacture.
Journal of Physics: Condensed Matter, 2006
The characterization of several differently sized aluminium powders, by BET (specific surface), E... more The characterization of several differently sized aluminium powders, by BET (specific surface), EM (electron microscopy), XRD (x-ray diffraction), and XPS (x-ray photoelectron spectroscopy), was performed in order to evaluate their application in solid rocket ...
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Papers by Luciano Galfetti