1,721,135 research outputs found
Performance comparison of green propulsion systems for future Orbital Transfer Vehicles
No full textThis paper explores the relevance of a new class of upper stages commonly referred to as Orbital Transfer Vehicles (OTVs) or Kick-Stages, and the importance of green propellants in the development of such systems.
Orbital Transfer Vehicles are currently developed for diverse applications by many entities and are expected to
have a major impact in the future of space missions and overall space sector. Such systems are commonly
connected to the topic of On-Orbit Servicing with the promise of unlocking new missions, including active space
debris removal, multi-payload to multi-orbit delivery, in-orbit experiments, in-orbit refuelling and other generic
services. Green propulsion is an increasingly prevalent trend in the space industry that has experienced significant growth in recent decades with the main objective of identifying suitable alternatives to commonly used,
toxic liquid propellants for in-space applications. The study investigates the synergies between the two themes,
underlining the advantages that a widespread use of green technologies could bring to the overall sector, but also
examining the final benefits to the system design of OTVs. Due to the numerous and challenging propulsive
system requirements associated with these systems, green technologies are analysed to determine their advantages and disadvantages in comparison with current concepts, outlining current trends and expected future
developments. The focus is on attainable performances of propulsion systems with respect to the required dry
and inert mass. Various architectures of the different green alternatives based on hydrogen peroxide and the
more peculiar self-pressurized propellants are proposed, exploring green propellants-based designs that can offer
synergies and advantages over classical ones. These new architectures offer performance comparable to classical
and widely available toxic alternatives and present the important advantage of using easy-to-handle propellants.
The development of such new options has the potential to enable innovative future designs by improving mass
and size requirements of new propulsion systems, thereby enhancing the current landscape
Lumped Parameter Analysis of Autogenous Propellant Pressurization System for Nuclear Thermal Rocket
No full textThis work proposes a new propellant management configuration for an ammonia-fueled nuclear thermal propulsion system. The suggested configuration maximizes the advantage deriving from the autogenous pressurization of ammonia by exploiting the thermal power lost by the nuclear reactor toward the vacuum space due to leaking radiation. In this layout, a tank containing ammonia in saturated conditions is placed near the nuclear reactor and receives an input thermal power proportional to the dose of gamma rays and neutrons absorbed by the tank walls and the ammonia itself. Such a thermal power accelerates the vaporization process of the saturated ammonia, thus increasing the pressure in the tank. A pressure regulator valve exploits this overpressure to pressurize the ammonia propellant contained in a run tank to the level required by the mission by connecting the two ammonia volumes. The pressure achieved inside the run tank pushes the propellant with an adequate mass flow rate inside the nuclear reactor. The developed lumped parameter analysis shows how this propellant management system can provide a constant mass flow to the nuclear reactor without using a turbopump assembly. Moreover, it is shown how the proposed concept allows for a reduction in the radiation shield mass
A holistic approach for efficient greener in-space propulsion
No full textThis paper presents a comprehensive framework for designing in-space propulsion systems, integrating four
criteria: global propulsive performance, environmental impact, cost efficiency, and architectural reliability. The
study focuses on the emerging class of Orbital Transfer Vehicles to illustrate the application of this method. By
examining the synergistic potential of OTVs and greener propellants, the paper addresses different mission
scenarios, including LEO, GEO, and lunar missions, with both scientific and commercial objectives. The proposed
framework aims to go beyond traditional cost-centric approaches, offering a more complete evaluation method
for early design phases. A case study comparing three liquid bipropellant options, pressure-fed MON-3/MMH,
98%-HTP/RP-1, and self-pressurizing N2O/Ethane, demonstrates the utility of the tool. Findings suggest that
scientific missions benefit most from 98%-HTP/RP-1, while traditional propellants remain preferable for costdriven commercial missions to GEO and the Moon, though greener alternatives are competitive for less
demanding LEO missions. This innovative framework aims to guide the selection of propulsion systems to
achieve greener space missions, aligning traditional performance figures with environmental responsibility
Simulation of Deployable Cable Nets for Active Debris Removal in Space
Full text linkDeployable cable nets have been proposed as promising systems for the active removal of space debris. The modelling and analysis of such systems during deployment, capture, and post-capture phases are crucial for the effective design of an operative mission. To this aim, accurate and effective simulation tools are necessary. We propose a finite element model of the cable net with lumped nodal masses and first-order cable elements. The nodal positions are assumed as the main unknowns of the problem. The large displacements and finite deformations are described by the Green-Lagrange strain tensor. The cable elements are assumed to react only in tension. Global damping is considered in line with Rayleigh's hypothesis. The governing equations are solved numerically by means of the Runge-Kutta method with a variable time step. As an illustrative example, we present the simulation of the in-plane deployment of a planar, square-mesh net. The proposed approach turns out to be computationally effective, even if the accuracy of the numerical integration scheme needs to be improved, particularly in the final stages of deployment
A Reduced Order Model for Preliminary Design and Performance Prediction of Tapered Inducers
Full text linkA reduced order model for preliminary design and noncavitating performance prediction of tapered axial inducers is illustrated. In the incompressible, inviscid, irrotational flow approximation the model expresses the 3D flow field in the blade channels by superposing a 2D crosssectional vorticity correction to a fully-guided axisymmetric flow with radially uniform axial velocity. Suitable redefinition of the diffusion factor for bladings with non-negligible radial flow allows for the control of the blade loading and the estimate of the boundary layer blockage at the specified design flow coefficient, providing a simple criterion for matching the hub profile to the axial variation of the blade pitch angle. Carter’s rule is employed to account for flow deviation at the inducer trailing edge. Mass continuity, angular momentum conservation and Euler’s equation are used to derive a si..
Dynamics of the Blade Channel of an Inducer Under Cavitation-Induced Instabilities
No full textA high-head three-bladed inducer has been equipped with pressure taps on the hub along the blade channels with the aim of more closely investigating the dynamics of cavitation-induced instabilities developing in the impeller flow. Spectral analysis of the pressure signals obtained from two sets of transducers mounted both in the stationary and rotating frames has allowed to characterize the nature, intensity, and interactions of the main flow instabilities detected in the experiments: subsynchronous rotating cavitation (RC), cavitation surge (CS), and a high-order axial surge oscillation. A dynamic model of the unsteady flow in the blade channels has been developed based on experimental data and on suitable descriptions of the mean flow and the oscillations of the cavitating volume. The model has been used for estimating at the inducer operating conditions of interest the intensity of the flow oscillations associated with the occurrence of the CS mode generated by RC in the inducer inlet
Pumping and Suction Performance of a Whirling Inducer
Full text linkThe experimental characterization of the rotordynamic fluid forces acting on a whirling inducer and the analysis of their influence on its pumping and suction performance are presented and discussed as functions of the operational conditions. The paper illustrates the first application of the novel approach recently developed at Alta for the simultaneous measurement of the relevant experimental data, demonstrating its remarkable versatility and effectiveness
Green Propellants Research at Alta S.p.A
Full text linkA summary of the activities carried out in the last four years by Alta S.p.A. on hydrogen peroxide for propulsive applications is given. In the framework of European Space Agency and Italian Government funded projects, a significant know-how on this matter has been gained by Alta in collaboration with the Universities of Messina and Pisa. Tests have been carried out in the GPRT facility, an easily reconfigurable and expandable experimental apparatus for the characterization of the propulsive performance of small monopropellant thrusters. After an intensive phase of development and characterization, several advanced catalytic beds capable of effectively decomposing hydrogen peroxide have been obtained. In order to characterize the catalysts under real working conditions two reconfigurable monopropellant thruster prototypes were simultaneously designed and successfully tested at Alta. Endurance tests on the LR-III-106 and CZ-11-600 catalysts allowed for accumulating respect..
PulCheR – Pulsed Chemical Rocket with Green High Performance Propellants: First Year Project Overview
Full text linkPulCheR (Pulsed Chemical Rocket with Green High Performance Propellants) is a research project co-funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°313271. The project officially started as of January 1st, 2013, and is mainly aimed at demonstrating the feasibility of a pulsed propulsion system in which the propellants are fed in the combustion chamber at low pressure and the thrust is generated by means of high frequency pulses, reproducing the defence mechanism of a notable insect: the bombardier beetle. The feasibility of this new propulsion concept will be investigated at breadboard level in both mono and bipropellant configurations through the design, realization and testing of a platform of the overall propulsion system including all its main components. As an added value, the new propulsion concept will be investigated using green propellants. The present paper aims at introducing the project, its structure, its main objectives and at presenting an overview of the activities performed in the first year of the project and its current status
Development and Testing of Pt/Al2O3 Catalysts for Hydrogen Peroxide Decomposition
Full text linkSupported Pt/Al2O3 and Pt/SiC catalysts for hydrogen peroxide (HP) decomposition have been prepared by means of two innovative implantation techniques on spheres and granules of several alumina-based carriers (lanthanum-doped alumina, bimodal delta –alumina and theta –alumina, silicon carbide and alpha–alumina) with BET surface areas between 4 and 200 m2/g. In order to evaluate the chemical activity and thermal shock resistance of the supporting pellets, two focused sets of experiments have been carried out in a specifically-designed test bench. Scanning electron microscopy (SEM) measurements of the platinum load on the supporting surface have been used to assess the effectiveness of the deposition and monitor the degradation induced by hydrogen peroxide decomposition. Two of the Pt/α−Al2O3 catalysts showed excellent activity, high thermo-mechanical strength, and negligible loss of platinum after repeated cycles of hydrogen peroxide decomposition. In addition, h..
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