Assessment of Propulsion System Architectures for Green Propellants-based Orbital Stages

Green Propulsion is a recurring trend in the space sector that has grown exponentially over the last decades. The researchers’ shared goal is to find good alternatives to current liquid propellants, usually toxic and hard-to-manage during ground operations. The current toxic leading compounds are Hydrazine and its derivatives that covered and still cover a key role in the space propulsion arena: as a matter of fact, despite the well-known complications for incompatibilities with human health, and despite the dozens of proposed replacements, the propellants still have some advantages over many of the suggested alternatives and are commonly used. The main and natural application of green technologies is doubtlessly the in-space propulsion since the main features of long-term storability, stability and acceptable performance are a perfect match for engines working outside the atmosphere and far from the support of ground operations. In this study, the identified most attractive technologies are evaluated on their applicability to upper stages. A specific class of systems, often referred to as kick-stages, are taken as reference. These systems are designed, as usually, to remain as light as possible to carry more payload, but concomitantly to be able to fulfil a very diverse type of missions. Between others: active space debris removal, multi-payload to multi-orbit delivery, in-orbit experiments with a few providers planning also the reusability and return to the ground. With such diverse and arduous purposes, it is clear that, in terms of propulsive system requirements, the challenges are many. The analysis expands on utilization of green technologies for these systems, outlining advantages and disadvantages in comparison with current concepts. Particular focus is dedicated to the attainable performance with respect to required dry mass. In particular, it is analysed the different inert mass rate of various architectures considering also full-green-propellants-based designs that can offer synergies and advantages respect to classical ones

Cold-Flow Testing of Various Injector Designs for a Novel Hypergolic and Green Propellant Combination Developed at DLR Lampoldshausen

In the field of space propulsion, the Green Propellants topic is a renowned recurrent trend. Between the many options available, a combination recently developed at DLR Lampoldshausen appears particularly promising, possessing most of the correct features to lead the switch to greener compounds: storability, reduced toxicity, good performance and especially hypergolicity. The propellant combination is an ionic liquid fuel, coupled with highly concentrated hydrogen peroxide as oxidizer, the so called HIP_11. The present study describes various injection approaches, describing the multifaceted challenges encountered. The study is completed by a cold-flow test campaign that investigated the spray pattern of the various designs

Eco-Design of future reusable launchers: insight into their life cycle and atmospheric impact

Reusable launch vehicles (RLV) are slowly emerging as a solution to reduce space access costs, bringing potential benefits from novel breakthrough space application. Whilst space presents an ideal platform for addressing global issues, it raises an "adaptation-mitigation dilemma". Launch vehicles are the only anthropogenic object emitting directly into every layer of the atmosphere, and reusability may introduce additional burdens. Although it may ensure a rational use of materials through the recycling of major components, its potential sustainability gains with respect to equivalent expendable launch vehicles (ELV) has not been quantified. The correct understanding of these are therefore critical to ensure sustainable design choices for space transportation. This study reviews current state of knowledge on launchers environmental impact and eco-design before introducing a preliminary life cycle and atmospheric impact assessment of the different technologies for first stage reusabiltiy. Reusabiltiy showed possible early reductions in material resource depletion which was independent of propellant choice and recovery strategies. In terms of climate forcing, reusability was only beneficial when fully carbon neutral propellant production was assumed for hydrolox, ammolox technologies, and possibly for methalox if soot production is kept under sustainable limits. VTHL performing In-Air-Capturing recoveries also showed reduced climate forcing potential. Stratospheric ozone depletion potential was estimated to increase by 18-34 % for VTVL vehicles, and 12-16% for VTHL with respect to ELV. In addition, high sensitivity with mixture ratios, flight profiles, staging condi- tions and aerodynamic capabilities was identified, which require detailed assessments with higher fidelity design methods. Future launch impacts from large scale space activities were also estimated to no longer be negligible, although some margin for mitigation exists among the various design options, and recent regulatory developments internalizing climate change costs might significantly affect the business case of RLVs. In addition, high altitude atmospheric impacts, particularly those from soot emissions, appear to dominate the potential life cycle impact and uncertainty, especially for hydrocarbon fuelled launch vehicles. This is further exacerbated by the commonly used but unsuitable weighting based on aviation and ground based emissions. These might affect the absolute and relative comparisons significantly and therefore, results from this study must be taken with caution. Future studies should employ state of art atmospheric modelling and adequate approaches to weight the various life cycle impacts, enabling design for mitigation while avoiding burden shifts

Eco-design of future reusable launchers : insight into their life cycle and atmospheric impact

Reusable launch vehicles (RLV) are slowly emerging as a solution to reduce space access costs, bringing potential benefits from novel breakthrough space application. Whilst space presents an ideal platform for addressing global issues, it raises an "adaptation-mitigation dilemma". Launch vehicles are the only anthropogenic object emitting directly into every layer of the atmosphere, and reusability may introduce additional burdens. Although it may ensure a rational use of materials through the recycling of major components, its potential sustainability gains with respect to equivalent expendable launch vehicles (ELV) has not been quantified. The correct understanding of these are therefore critical to ensure sustainable design choices for space transportation. This study reviews current state of knowledge on launchers environmental impact and eco-design before introducing a preliminary life cycle and atmospheric impact assessment of the different technologies for first stage reusabiltiy. Reusabiltiy showed possible early reductions in material resource depletion which was independent of propellant choice and recovery strategies. In terms of climate forcing, reusability was only beneficial when fully carbon neutral propellant production was assumed for hydrolox, ammolox technologies, and possibly for methalox if soot production is kept under sustainable limits. VTHL performing In-Air-Capturing recoveries also showed reduced climate forcing potential. Stratospheric ozone depletion potential was estimated to increase by 18-34 % for VTVL vehicles, and 12-16% for VTHL with respect to ELV. In addition, high sensitivity with mixture ratios, flight profiles, staging condi- tions and aerodynamic capabilities was identified, which require detailed assessments with higher fidelity design methods. Future launch impacts from large scale space activities were also estimated to no longer be negligible, although some margin for mitigation exists among the various design options, and recent regulatory developments internalizing climate change costs might significantly affect the business case of RLVs. In addition, high altitude atmospheric impacts, particularly those from soot emissions, appear to dominate the potential life cycle impact and uncertainty, especially for hydrocarbon fuelled launch vehicles. This is further exacerbated by the commonly used but unsuitable weighting based on aviation and ground based emissions. These might affect the absolute and relative comparisons significantly and therefore, results from this study must be taken with caution. Future studies should employ state of art atmospheric modelling and adequate approaches to weight the various life cycle impacts, enabling design for mitigation while avoiding burden shifts

RLV applications: challenges and benefits of novel technologies for sustainable main stages

Within the scope of the European Green Deal, the aerospace industry is currently staking on sustainability. To fulfil the objectives and in order to ensure Europe's independent and cost-effective space access capabilities, the ASCenSIon (Advancing Space Access Capabilities - Reusability and Multiple Satellite Injection) project, funded by H2020, is connecting fifteen Early-Stage Researchers (ESRs) and twenty-four partner organizations all across Europe. The pillar concept within the project is to adopt a Concurrent Research Network (CRN) methodology. Accordingly, different host institutions, each one with its main research program and vision, are connected to develop the design under a new perspective. This approach emphasises the cooperation between the fifteen ESRs, thus covering the design of a Reusable Launch Vehicle (RLV) in its overall complexity, facing the new challenges deriving from the required sustainability in a more efficient manner. Corresponding to work package two (WP2) of ASCenSIon, this paper focuses on main stages for RLVs, and how the goal of sustainability affects their design. Therefore, many different interconnected disciplines, such as propulsion system, structural design, fatigue-life analysis and Health Monitoring (HM) have to be taken into consideration. These different domains are represented by the individual research projects of the ESRs, supported by a collaborative environment which promotes the foreseen interactions. At first, this contribution gives a general State-Of-The-Art overview of the mentioned topics. A preliminary trade-off on RLV architectures is established through multi-disciplinary design analysis and optimization methods based on propulsion modelling, optimal staging and structural sizing. These use performance and cost design metrics as objective functions, accounting for operability and maintainability factors. This investigation is then used to discuss the different Advanced Nozzle Concepts (ANCs) tailored on the system requirements and mission constraints. At this point, a one-dimensional performance analysis addresses the performance gain deriving from altitude-compensation properties of ANCs. Subsequently, the identification of a suitable green propellant will give the needed/accurate/required inputs to conduct a trade-off between engine cycles w.r.t. the fatigue-life of their most critical components. Consequently, fatigue-life analysis contributes to HM and sensing requirements for RLV systems. As a common approach between the ESRs, the data collection is organized in various Databases accessible within the network, which encourages their interconnections and collaborative research. This paper provides a preliminary analysis of the above discussed topics and their interconnections within the framework of ASCenSIon, aiming to develop novel technologies for future sustainable main stages

Mass flow rate measurement and control for a space propulsion Iodine feeding system

[ENG] The continuous increase in market demands for innovative and cheaper propulsion systems has led researchers to investigate for new solutions, from which the adaptation of existent technologies with more efficient modifications. In this perspective, the exploitation of new propellants for space propulsion electric devices, in particular Hall effect thrusters, is currently under evaluation around various research centres. The thesis work deals with the results of an ongoing activity focused on further development of an existing prototype of an iodine feeding system for space propulsion. The project background in which the activity has developed is described in Chapter 2 along with a general description of iodine advantages as alternative propellant, the problematics generated by its use and the solutions proposed by the team. The prototype geometry is then described in Chapter 3 as well as the development process which led to the final configuration. Components are illustrated outlining the operation principles and theoretical models and simulations, exploited to predict the assembly behaviour, are reported. Particular emphasis is dedicated on predicted thermal performances which play a primary role during operations. Mass flow rate measurement and control strategies are illustrated besides the proposal of an innovative mass flow meter based on optical techniques in Chapter 4. Experiments aimed at understanding the feasibility of the device utilization for the project scopes are described and commented, together with the consequent exploitation scenarios opened by the results. In the end, Chapter 5 describes the experimental activity. Test procedures are illustrated in conjunction with experiments set-up for current and future test campaigns. Preliminary results and studies are reported and commented. [ITA] L'interesse continuo del mercato nella ricerca di nuovi e meno costosi sistemi propulsivi ad uso spaziale ha portato i ricercatori a studiare nuove soluzioni, tra cui l'adattamento di tecnologie esistenti con nuove e più efficaci modifiche. In questa prospettiva, lo studio di nuovi propellenti per la propulsione spaziale elettrica, in particolare per i motori a effetto Hall, è correntemente in via di sviluppo in vari centri di ricerca in tutto il mondo. Il lavoro di tesi tratta i risultati di una attivit\'a tuttora in corso di svolgimento finalizzata allo sviluppo di un prototipo esistente di un sistema di alimentazione per propulsione spaziale alimentato a iodio. Dopo una breve introduzione, nel Capitolo 2 viene illustrato il progetto da cui l'attività nasce, seguito da una descrizione dello iodio come propellente alternativo coi relativi vantaggi e soluzioni proposte ai problemi eventuali derivanti da un suo utilizzo. Nel Capitolo 3 viene illustrata la geometria del prototipo insieme al processo di sviluppo che ha portato alla configurazione finale del sistema. I componenti sono descritti nello spiegare il funzionamento dell'assemblato e i modelli teorici. Sono inoltre descritte le simulazioni svolte, con particolare enfasi al comportamento termico del sistema che svolge un ruolo cruciale per il corretto funzionamento. Nel Capitolo 4 sono illustrate le strategie proposte per misurare la portata del sistema, insieme alla proposta e processo di sviluppo di un innovativo sistema di misurazione di portata massica basato su tecniche ottiche. Gli esperimenti dedicati allo studio di questo apparecchio e alla sua applicabilità al sistema in studio sono descritti, e i risultati commentati. Infine il Capitolo 5 descrive le attività sperimentali svolte. Le procedure sono descritte in dettaglio insieme al set-up degli esperimenti per prove ancora in atto e future. I risultati preliminari, derivanti dagli studi finora svolti, sono riportati e commentati

Experimental Investigation of Combustion Performances of a Green Hypergolic Bipropellant based on Hydrogen Peroxide

The present study examines the advancement of a promising low-toxicity hypergolic propellant combination called HIP_11 for in-space applications, developed as alternative to common toxic propellants. The fuel is an Energetic Ionic Liquid, storable, stable and simple to handle at ambient conditions, developed at the Institute of Space Propulsion, German Aerospace Centre (DLR). The compound shows hypergolicity behaviour when in contact with Hydrogen Peroxide and is a promising substitution to typical propellants. The present work describes the advancements in the development of HIP_11 through a dedicated experimental campaign, consisted in more than 50 successful firings, analysing and investigating the performances. The experiments are based on a small modulable thruster that allowed to study the efficiency and stability of combustion of the propellant combination while varying various design parameters of the thruster. Specifically, the effects of different injector designs, as well as variations in combustion chamber shape, characteristic length, and operating pressure have been thoroughly examined and analysed

Analytical Hierarchy Process-based trade-off analysis of green and hybrid propulsion technologies for upper stage applications

As an emerging trend, Green Propulsion has been exponentially growing over the last decades in the space sector. This paper assesses different technologies in a trade-off study weighting their applicability to a specific class of upper stage systems currently developed by many companies and often referred to as kick-stages or orbital stages. In a generic two-stage-to-orbit scenario, many launchers require a system able to go the ‘extra mile’ to deliver one or multiple payloads on orbit(s). That is where the kick stage comes into playing a crucial role. The trade-off study reported here is based on a well-known decision-making tool, the Analytical Hierarchy Process, and is divided into two parts: low-thrust class engines such as monopropellants, including pre-mixed blends, usually employed for attitude and reaction control; and high-thrust engines such as hypergolic bi-propellants combinations used for apogee manoeuvres. Hybrid thrusters are also considered in the analysis with a dedicated parallel trade-off.info:eu-repo/semantics/publishe

Trade-off study of green technologies for upper stage applications

As an emerging trend, Green Propulsion has been exponentially growing over the last decades in the space sector. This paper assesses different technologies in a trade-off study weighting their applicability to a specific class of upper stage systems, currently developed by many companies and often referred to as kick-stages or orbital stages. In a generic two-stage-to-orbit scenario, many launchers require a system able to go the ‘extra-mile’ to deliver one or multiple payloads on orbit(s). That is where the kick stage comes into playing a crucial role. The trade-off study reported here is based on a well-known decision-making tool, the Analytical Hierarchy Process. The main results are a technologies evaluation framework, strongly requirements-oriented, that allows to select the most promising candidates for various scenarios, and a preliminary technology selection. The screening is divided into liquid low-thrust class engines, usually employed for attitude and reaction control thrusters; and liquid high-thrust engines such as hypergolic bi-propellants combinations, commonly used for apogee manoeuvres. Finally, the evaluation framework is tested on Hybrid thrusters to examine its flexibility in a dedicated parallel trade-off.info:eu-repo/semantics/publishe