Overview of Al-based nanoenergetic ingredients for solid rocket propulsion

The introduction of nano-sized energetic ingredients first occurred in Russia about 60 years ago and arose great expectations in the rocket propulsion community, thanks to the higher energy densities and faster energy release rates exhibited with respect to conventional ingredients. But, despite intense worldwide research programs, still today mostly laboratory level applications are reported and often for scientific purposes only. A number of practical reasons prevent the applications at industrial level: inert native coating of the energetic particles, nonuniform dispersion, aging, excessive viscosity of the slurry propellant, possible limitations in mechanical properties, more demanding safety issues, cost, and so on. This paper describes the main features in terms of performance of solid rocket propellants loaded with nanometals and intends to emphasize the unique properties or operating conditions made possible by the addition of the nano-sized energetic ingredients. Steady and unsteady combustion regimes are examined. Keywords: Nanoaluminum, Solid rocket propellant, Burning rate, Combustion, Propulsion, Performanc

innovative solid formulations for rocket propulsion

Solid rocket propulsion enjoys several unique properties favoring its use in space exploration and military missions still for decades to come, in spite of being by far the most mature propulsion technology among those currently employed. Yet, solid rocket propellants also suffer a limited performance in terms of gravimetric specifi c impulse. Although many high-energy density materials have been identifi ed, most of them are far from being practically usable in the short range due to a variety of severe diffi culties, including cost considerations. Presently, no integrated vehicle designs make use of these potential propellant ingredientsand formulations. Work is continuing worldwide and a broad overview will be discussed in this paper based on a joint international editorial effort just completed. After a quick historical survey, the current situation in terms of advanced solid oxidizers, metal fuels, and binder systems is scrutinized. Particular attention is paid to Ammonium Dinitramide (ADN)-based formulations to overcome the limitations of the currently used ones based on Ammonium Perchlorate (AP). The latter imply not only a limited gravimetric specifi c impulse but also a negative impact on the environment because of copious emissions of hydrochloric acid (HCl) as well as personal health because of perchlorate competition with iodide in entering the thyroid gland. Based on recent experimental investigations, due to its intrinsic ballistic properties, it turns out that ADN-based dual-oxidizer systems with Albased dual-metal fuels and inert or energetic binders are promising solutions for a variety of solid rocket propulsion aiming respectively at minimizing environmental impact (ADN + Ammonium Nitrate AN) or maximizing performance (ADN + AP). Yet, a lot of work remains to be done in order to upgrade these formulations to industrial applications. In particular, adequate analyses of manufacture, mechanical, and hazard properties are required

Universality of rain event size distributions

We compare rain event size distributions derived from measurements in climatically different regions, which we find to be well approximated by power laws of similar exponents over broad ranges. Differences can be seen in the large-scale cutoffs of the distributions. Event duration distributions suggest that the scale-free aspects are related to the absence of characteristic scales in the meteorological mesoscale.Comment: 16 pages, 10 figure

Medical Professionals' Perspectives on Prescribed and Over-The-Counter Medicines Containing Codeine: A Cross-Sectional Study

Objectives: To explore prescribing practitioners' perspectives on prescribed codeine use, their ability to identify dependence and their options for treatment in the UK. Design: Cross-sectional design using a questionnaire containing closed-ended and open-ended items. Setting: A nationally representative sample of prescribing professionals working in the UK. Participants: 300 prescribing professionals working in primary care and pain settings. Results: Participants stated that they regularly reviewed patients prescribed codeine, understood the risks of dependence and recognised the potential for codeine to be used recreationally. Over half the participants felt patients were unaware of the adverse health consequences of high doses of combination codeine medicines. One-quarter of participants experienced patient resentment when asking about medicines containing codeine. Just under 40% of participants agreed that it was difficult to identify problematic use of codeine without being informed by the patient and did not feel confident in identification of codeine dependence. Less than 45% of all participants agreed that codeine dependence could be managed effectively in general practice. Slow or gradual withdrawal was the most popular suggested treatment in managing dependence. Education and counselling was also emphasised in managing codeine-dependent patients in primary care. Conclusions: Communication with patients should involve assessment of patient understanding of their medication, including the risk of dependence. There is a need to develop extra supports for professionals including patient screening tools for identifying codeine dependence. The support structure for managing codeine-dependent patients in primary care requires further examination

Contemplative Science: An Insider's Prospectus

This chapter describes the potential far‐reaching consequences of contemplative higher education for the fields of science and medicine

Relaxation of classical many-body hamiltonians in one dimension

The relaxation of Fourier modes of hamiltonian chains close to equilibrium is studied in the framework of a simple mode-coupling theory. Explicit estimates of the dependence of relevant time scales on the energy density (or temperature) and on the wavenumber of the initial excitation are given. They are in agreement with previous numerical findings on the approach to equilibrium and turn out to be also useful in the qualitative interpretation of them. The theory is compared with molecular dynamics results in the case of the quartic Fermi-Pasta-Ulam potential.Comment: 9 pag. 6 figs. To appear in Phys.Rev.

Experiments and simulations on interactions between 2,3-bis(hydroxymethyl)-2,3-dinitro-1,4-butanediol tetranitrate (DNTN) with some energetic components and inert materials

Abstract In order to survey the application prospects of 2,3-bis(hydroxymethyl)-2,3-dinitro-1,4-butanediol tetranitrate (DNTN, NEST-1, SMX) in high - energy solid rocket propellants and explosives, the interactionsbetween DNTN with some energetic components and inert materials were investigated by means of differential scanning calorimetry (DSC) and molecular dynamic (MD) methods, where glycidyl azide polymer (GAP), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitroamine (HMX), lead 3-nitro-1,2,4-triazol-5-onate (NTO-Pb), hexanitrohexaazaisowurtzitane (CL-20), aluminum powder (Al) and magnesium powder (Mg), 3,4-dinitrofurzanfuroxan (DNTF), N-guanylurea-dinitramide (GUDN), N-butyl-N-(2-nitroxy-ethyl)nitramine (Bu-NENA), bis(2,2-dinitropropyl) acetal (BDNPA)/bis(2,2-dinitropropyl) formal (BDNPF) mixture (A3), nitrocellulose - nitroglycerine (NC-NG) and ammonium dinitramide (ADN) were used as energetic components and hydroxyl terminated polybutadiene (HTPB), polyoxytetram ethylene-co- oxyethylene (PET), addition product of hexamethylene diisocyanate and water (N-100), 2,4-toluene diisocyanate (TDI), 1,3-dimethyl-1,3-diphenyl urea (C2), carbon black (C.B.), aluminum oxide (Al2O3), lead phthalate (φ-Pb), N-nitro-dihydroxyethylamine dinitrate (DINA), cupric 2,4-dihydroxy-benzoate (β-Cu) were used as inert materials. The impact and friction sensitivities of DNTN and DNTN in combination with energetic materials were obtained. . It was concluded that the binary systems of DNTN with RDX, HMX, NTO-Pb, Al, Mg, ADN, NC-NG, HTPB, PET, C2, C.B., β-Cu and Al2O3 are compatible, whereas systems of DNTN with GAP, CL-20, A3, N-100, TDI and DINA are slightly sensitive, and those containing DNTF and GUDN are incompatible. It is demonstrated that no consequential trend between sensitivity and compatibility is found. The mechanical properties and safety performance of GAP mixtures plasticized with three plasticizers decrease in the following order: [BTTN] > [TMETN] > [Bu-NENA]