Filippo Maggi

Politecnico di Milano | Polimi · Department of Aerospace Engineering

Composite solid propellants have used cast molding production technology for many decades, with intrinsic limitations on production flexibility, promptness, and grain geometry, as well as environmental implications on toxicity and global carbon footprint. This traditional method involves the use of toxic chemicals, has a long processing time, requi...

Conventional storable bipropellants make use of hydrazine and its derivatives as fuels and nitrogen tetroxide as an oxidizer. In recent years, the toxicity character of these chemicals pushed the propulsion community towards “green” alternatives. Several candidates have been proposed among existing and newly developed chemicals, highlighting the ne...

This work presents a parametric analysis of corona thrusters performance as function of electrodes geometry, focusing on collector electrodes. A set of airfoil-shaped collectors with fixed chord and different profiles is tested on a propulsion system at bench. The setup consists in a parallel array of thruster units with adjustable spacing. The dow...

This paper describes an inexpensive, non-invasive, and highly adaptable surface reconstruction device for opaque liquids. The instrument was developed to study the lateral sloshing of ferrofluids in microgravity as part of the UNOOSA DropTES 2019 StELIUM project. Its design is driven by the geometrical and mechanical constraints imposed by ZARM’s d...

The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers and operators. Those include the generation of significant attitude disturbances, the uncontrolled displacement of the center of mass of the vehicle or the production of gas bubbles, among others. Magnetic fields can be used to induce the reorientat...

This paper addresses the operation in microgravity of the surface reconstruction device whose design is detailed in the first part of the manuscript. The system, employed during the drop tower campaign of the UNOOSA DropTES 2019 StELIUM experiment, studies the axisymmetric and lateral oscillations of a ferrofluid solution in microgravity. The free...

An innovative collection methodology based on a recently developed supersonic probe enabled the collection of alumina particulate from the exhaust plume of a sub-scale solid propellant rocket motor and the comparison with quench collection bomb analysis of propellant incipient agglomeration. Laser diffraction, scanning electron microscopy, and X-ra...

A programmatic and unified framework of techniques, targeting the particles size evolution in solid rocket motors (SRMs) from the combustion chamber to the nozzle exit, is delivered. On one hand, quench bomb tests enable to obtain the statistical distribution of particles diameter at the release from the propellant burning surface. On the other, an...

The established state-of-the-art for composite solid propellant grain manufacture consists in mix-cast-cure process using hazardous chemicals and specific molds for propellant forming. In most of the cases, polyaddition of oligomers involves isocyanate functional groups. Construction constraints limit the feasibility of propellant geometries, confi...

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 t...

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 t...

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 lo...

The pursuit of solid rocket motor and hybrid rocket engine performance enhancements is pushing toward the research of novel energetic materials replacing the conventional micron-sized aluminum. Nanotechnology opened the way to new concepts, introducing very promising ingredients like nano-sized aluminum powders. Their effectiveness in increasing en...

Ammonium perchlorate (AP)-based solid rocket propellants generate hydrochloric acid (HCl) as an exhaust product during combustion. This latter displays numerous environmental problems such as the depletion of the ozone layer and the increase of the concentration of acid rains. This paper offers a theoretical analysis concerning the employment of me...

Liquid sloshing represents a major challenge for the design and operation of space vehicles. In low-gravity environments, a highly non-linear movement can be produced due to the lack of stabilizing forces. This gives rise to significant disturbances that impact on the propulsion and attitude control systems of the spacecraft. The employment of magn...

Fuel‐rich propellants are used in ducted rocket technology. The reduced content of oxidizer and the use of atmospheric air improve the gravimetric specific impulse far above the level of standard rocket motors, granting longer operating range. Peculiar requirements of ducted rockets favor either high or low‐pressure exponent propellants, depending...

[The final version of this paper can be found in https://doi.org/10.1016/j.actaastro.2021.06.045] The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers and operators. Those include the generation of significant attitude disturbances, the uncontrolled displacement of the center of mass of the vehicle o...

The sloshing of liquids in microgravity is a relevant problem of applied mechanics with important implications for spacecraft design. A magnetic settling force may be used to avoid the highly non-linear dynamics that characterize these systems. However, this approach is still largely unexplored. This paper presents a quasi-analytical low-gravity sl...

[The final version of this work can be found at https://doi.org/10.1016/j.actaastro.2021.08.029 and https://doi.org/10.1016/j.actaastro.2021.07.020] Liquid level measurement devices are required in experimental sloshing research. Several techniques with different capabilities and degrees of complexity have been historically proposed to cover this n...

Liquid sloshing represents a major challenge for spacecraft design and operation. In low-gravity environments, a highly non-linear movement is produced due to the lack of stabilizing forces. This gives rise to significant disturbances that impact on the attitude control system of the vehicle. The employment of magnetically susceptible fluids may op...

The current paper provides an overview of the ESA-EMAP project. This project pursues activities regarding the experimental modeling of alumina particulates in solid boost-ers. 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 oz...

Solid propellant rocket boosters release metal oxide particulate in the atmosphere, as a result of the combustion of the aluminum powder contained in the energetic material. The characterization of these particles is still an open question regarding the environmental impact of space launch activities. For this reason an innovative collection techni...

Abstract presented to the 26th European Low Gravity Research Association Biennial Symposium and General Assembly.

The sloshing of magnetic liquids has distinctive characteristics that may become useful for the control of propellants in space. Magnetic fields can be used to shift the natural frequencies and damping ratios of an oscillating fluid. In the framework of the UNOOSA DropTES Programme, StELIUM (Sloshing of magnetic LIqUids in Microgravity) will study...

The present work focuses on the alumina particles size evolution inside the nozzle. For this purpose, an experimental and numerical investigation is proposed, focusing on two main topics: (1) development of a novel experimental device enabling nozzle-flow visualization. This apparatus consists of a two-dimensional windowed rocket motor operating at...

Use of mechanical milling to increase micrometric powder reactivity is of interest due to several intrinsic advantages of this technique (e. g. versatility and safety). In this work, 30 μm propulsion‐grade aluminum has been activated with and without metal oxides. The powders so obtained were characterized in terms of particle size distribution, me...

In the framework of a cooperation agreement between SPLab of Politecnico di Milano and ICMATE-CNR (National Research Council), two different configurations of a rectangular geometry small scale model engine fuelled with gaseous hydrogen were tested at Mach 5.4 in a high enthalpy pulse facility. A dual-mode scramjet setup was first studied and the m...

The term sloshing refers to the forced movement of liquids in partially filled containers. In a low-gravity environment, the liquid mixes with pressurizing gas bubbles and adopts a random position inside the tank, resulting in unwanted perturbations and a complicated design. Liquid sloshing has consequently been a major concern for space engineers...

The present work aims at giving an overview of the current experimental activity status of an intrusive technique for particles capturing in supersonic-high temperature flows for the use in solid rocket motors plume. The innovative technique was conceived in the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) framework, an ini...

Nano-sized Al (nAl) features high reactivity implying possible issues related to its aging during storage. In this work, the aging behavior of micron-sized Al and nAl is investigated considering different relative humidity (RH) conditions (10% and 80%) at the temperature of 333 K. The marked aging sensitivity of nAl (100 nm) is testified by an almo...

Nano-sized Al (nAl) is an attractive candidate for the performance enhancement of current solid propellant formulations, and its characteristics are relevant for the development of innovative solid fuels for hybrid rocket propulsion. Nano-sized Al powders feature a higher reactivity than their micron-sized counterpart. While desirable for effective...

The present work aims at giving a comprehensive overview of the current development status of an intrusive probe, capable of collecting the condensed combustion products present in the exhaust of a solid rocket motors. The innovative technique was conceived in the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) framework, a pr...

Hematite represents the most common burning rate modifier used in propellant production. The tuning of burning rate is obtained even for amounts ranging below 1 wt% of the total composition. Different studies have evidenced a role in ammonium perchlorate dissociation while there are not enough literature documents to clearly support or oppose its c...

An intrusive technique for particles capturing in supersonic-high temperature flows to be used in solid rocket motors plume characterization is proposed. A supersonic probe for the collection of the condensed combustion products in the proximity of the rocket nozzle has been designed to handle a progressive deceleration and cooling down of the exha...

The employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The...

Ammonium nitrate finds application in explosives and chlorine-free slow-burning propellants. Different phases are known for this ammonium salt, each of them featured by peculiar bulk densities. As a consequence, the variation of storage temperature induces processes of expansion-contraction in the crystals, unless specific stabilization is performe...

Nano-sized Al (nAl) features high reactivity that, while desirable for effective energy conversion during the combustion, yields possible issues related to its storage. This paper investigates the ageing behavior of nAl under different relative humidity conditions (RH, from 80% to 10%) at the temperature of 333 K. Fresh and aged powders are charact...

The experimental study presented in this paper aims at investigating the influence of mechanically activated Al-Mg powders on the burning behavior of ADN-based composite propellants. Three different powders were employed: a non-treated blend of Al and Mg and two others batches produced with different intensities of the activation process. As binder...

The current development status of a vortex flow pancake (VFP) hybrid rocket engine is presented. The characterization of the VFP configuration is focused on internal flow-field investigation and combustion behavior analysis. The internal flow-field is characterized by highspeed visualizations and numerical analyses showing the effects of oxidizer m...

The main aim of the article is to investigate the vortex pancake hybrid motor (VPH), which is being consider to be a perspective solution for future small thrusters based on hybrid technology. Developed numerical simulation solves Navier-Stokes equations taking into account complex multi-step chemical kinetics, radiation and solid-fluid interaction...

Deorbiting missions by means of a solid rocket motor represent a viable solution to implement mitiga-tion actions against the proliferation of new debris population. This specific technology is flight-proven, simple to implement, and fits the main performance requirements for the mission (particle-free exhaust gases, readiness, specific impulse) bu...

The EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) activity is a project funded under ESA's Basic Technology Research Program (TRP) for the characterization of the plume exhausted from a metalized solid rocket motor and measurement technique improvement. In this framework, the development of a probe for supersonic high-temper...

The ammonium nitrate (AN) represents a cheap and chlorine-free alternative to ammonium perchlorate but it suffers from low reactivity. The literature is populated by a large number of papers regarding the catalysis of ammonium nitrate decomposition but data are quite inhomogeneous. In the frame of the GRAIL project an experimental campaign was cond...

An intrusive technique for the collection of the condensed combustion products in the proximity of the rocket nozzle is proposed. In particular, a supersonic probe able to withstand the harsh environment of a plume was sized to handle a progressive deceleration and cool down of the exhaust gas, preventing from liquid particle breakup. The task was...

Hematite represents the most common burning rate modifier used in propellant production. The effect of burning rate fine tuning is obtained even for amounts ranging below 1 wt% of the total composition. Different studies have evidenced a role in ammonium perchlorate dissociation while few data are available regarding its capability to enhance binde...

The ballistic response of hydroxyl-terminated polybutadiene (HTPB)- and paraffin-based fuel formulations burning under quasi-steady and transient operating conditions is analyzed by different diagnostics developed at the Space Propulsion Laboratory (SPLab) of Politecnico di Milano. The analysis of different fuel formulations under quasi-steady oper...

The use of metals as high-energy fuels has been for long time a common approach to increase performance of chemical rocket propulsion in general. This effort was initially triggered by theoretical thermochemical considerations, but under real operating conditions, a series of collateral and unforeseen effects occurred, with both positive and negati...

Nano-sized aluminum (nAl) particles have several features that make them interesting for energetic applications. Compared to micron-sized aluminum (μAl) higher reactivity, lower ignition temperature and condensed combustion products of reduced size can be achieved. This work focuses on the pre-burning characterization of nAl. In the analysis, diffe...

Oral presentation

Compactness, reliability, readiness, and construction simplicity of solid rocket motors make them very appealing for commercial launcher missions and embarked systems. Solid propulsion grants high thrust-to-weight ratio, high volumetric specific impulse, and a Technology Readiness Level of 9. However, solid rocket systems are missing any throttling...

Oxamide (OXA) and azodicarbonamide (ADA) are among the known burning rate suppressants used in composite solid rocket propellants. Much research has been carried out to understand mechanism of suppression but literature about the action of OXA and ADA on the combustion characteristics of propellant is still scarce. Here, a systematic study on coola...

In recent years, packing codes have become a successful alternative to experimental data collection for microstructure investigation of heterogeneous materials. Composite solid rocket propellants are interesting representatives of this category, consisting of a mix of fuel and oxidizer powders embedded in a polymeric binder. Their macroscopic prope...

Several industrial - and research - type composite solid propellants containing different nano - metric metal oxide catalysts (Fe2O3, Co3O4, CuO, and PbO) with similar nominal composition, were prepared and experimentally analyzed. The effects of different nano-sized metal oxide catalysts on the rheological properties, and hazardous properties were...