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![Growth of the catalogued population of objects in Earth orbit [3].](profile/Francesca-Letizia/publication/323084323/figure/fig2/AS:596219470561280@1519161207126/Growth-of-the-catalogued-population-of-objects-in-Earth-orbit-3.png)
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![Fig. 2 Growth of the catalogued population of objects in Earth orbit [3].](profile/Francesca-Letizia/publication/323084323/figure/fig2/AS:596219470561280@1519161207126/Growth-of-the-catalogued-population-of-objects-in-Earth-orbit-3_Q320.jpg)
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Environmental indices for space objects have been proposed to identify good candidates for active debris removal missions and to deal with the licensing process of space objects before their launch. A way to rank the environmental impact of spacecraft may be based on the assessment of how their fragmentations would affect operational satellites. In...
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... was observed that the long term evolution of the space debris environment is highly affected by the fragmentation of large intact objects. Figure 2 shows the evolution of the number of objects in orbit with time and one can observe the effect of the fragmentation of Fengyun-1C and of the Iridium-Cosmos collision. A frag- mentation can be caused by explosion (for example due to a failure on-board) or by a collision with another object. ...
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... (1), A c is the average cross section of the spacecraft, N represents the number of released fragments, t i indicates the dwelling time in the i-th orbit. The main limitation regarding the analysis of the impact of different materials for space applications is that the determination of the number of fragments under hypersonic ballistic impact is performed by means of an empirical formula, irrespective of the materials constituting the systems of the spacecraft (Colombo et al., 2017;Letizia et al., 2018;Maury et al., 2019). Fracture mechanics indicates that materials behave in a different manner, depending on their capability to dissipate impact energy before breaking. ...
Space debris are a primary environmental concern for the sustainability of space mission activities. When considering terrestrial applications, the Life Cycle Assessment represents a widely standardised technique for estimating the environmental impacts of human activities; however, its implementation in the space-related value chain is still in an early stage. In this study, the implications of two alternative materials in the development of a CubeSat structural bus are investigated with reference to the well-established categories for the Life Cycle Impact Assessment. Moreover, the potential impact of these materials on the orbital environment is quantified by the evaluation of the number of generated fragments upon collision for different significant low Earth orbits. The results of this study allow to quantify the impact of alternative design solutions for space systems on the terrestrial environment as well as the degradation of the orbital resources as a result of the space debris generation.
... The number of generated fragments predicted by the NASA SBM, in case of an explosion, depends on the parameter , as defined in [26]. Its value is set according to the expression reported in [43], where the parameter is related to the object mass as follows. ...
Neglecting small fragments in space debris evolutionary models can lead to a significant underestimation of the collision risk for operational satellites. However, when scaling down to the millimeter range, the debris population grows to over one million objects, making deterministic approaches too computationally expensive. On the contrary, probabilistic models provide a more efficient alternative, which however typically work under some simplifying assumptions on the dynamics, limiting their field of applicability. This work proposes an extension of the density-based collision risk models to any orbital dynamics and impact geometry. The impact rate with a target satellite is derived from a multi-dimensional phase space density function in Keplerian elements, which discretely varies over both phase space and time. The assumption of a bin-wise constant cloud density allows for the analytical transformation of the six-dimensional distribution in orbital elements into the three-dimensional spatial density function, guaranteeing an efficient and accurate evaluation of the fragments flux. The proposed method is applied to the assessment of the collision risk posed by real fragmentation clouds in different orbital regions on a high-risk target object. The effect on the impact rate of the additional model features, compared to previous probabilistic formulations, is discussed.
... According to the NASA SBM, the number of objects generated by an explosion depends on the parameter S (Johnson et al., 2001), which, as motivated in Krisko (2011), can vary between 0.1 and 1 according to the fragmentation type. Following the same approach proposed in Letizia et al. (2018), the parameter S is set according to the following relations: ...
The permanent power loss and the deviation of the trajectory of satellites impacted by centimetre and sub-centimetre sized debris have highlighted the need of taking into account such small fragments in the evolutionary models of the debris population and in the assessment of the in-orbit collision risk. When scaling down to the centimetre-millimetre range, deterministic models for propagating the fragments’ orbit suffer from the massive computational cost required. The continuum approach for modelling the debris clouds is a well-established alternative to the piece-by-piece propagation. A density function is formulated to describe the distribution of fragments over a suitable phase space. Accurate and efficient continuum formulations have been developed to propagate clouds of fragments under atmospheric drag and J2 perturbations, but a general model able to work under any dynamical regime has still to be found. This paper proposes a continuum approach that combines the method of characteristics with the discretisation of the domain in Keplerian elements and area-to-mass ratio into bins. The problem of using a binning approach with such a multi dimensional phase space is addressed bounding and partitioning the domain, through probabilistic models on the way the fragments distribute over the phase space, as consequence of a fragmentation event. The proposed approach is applied to the modelling and propagation of a space debris cloud under the full set of orbital perturbations, and compared against a Monte Carlo simulation in terms of objects’ number and distribution. The method proves to be accurate on the medium scale, in both space and time, and guarantees statistical validity with a reduced computational effort, leveraging its probabilistic nature.
... The MASTER-2009 model allows us to obtain and discriminate the complete spectrum of the relative velocity of collision for given orbital coordinates (Klinkrad et al., 2006;Technische Universität Braunschweig, 2011;Technische Universität Braunschweig, 2014). As previously described in Letizia et al. (2018), the peak in the spectrum corresponds to the most probable velocity of collision (~14.5 km/s). Instead of taking this parameter, the weighted average velocity is obtained by summing the relative contribution of each impact velocity class. ...
By analogy to conventional environmental impacts, the potential release of debris or generation of fragments can be considered as the emission of an environmental stressor damaging the orbital ‘natural’ resource which supports space activities. Hence, it appears relevant to integrate systematically the impact of the emission of debris on the orbital resource within the life cycle impact assessment (LCIA) step to broaden the scope of life cycle assessment (LCA) for space systems.
The main objective of this article is to propose a set of characterization factors to compute the impact caused by the generation of debris within the orbital environment. To do so, the proposed approach follows the methodology of emission-related characterization models in LCIA. the characterization model enables to link the emission of debris and final economic damages to space activities through a complete impact pathway including the fate of debris in downstream orbital compartments, the exposure of targeted space objects to this debris, and the economic damage in case of collision between the debris and the space object. The model is computed for different compartments of the low earth orbit (LEO) region thanks to a discretization of the orbital environment.
Results show that the potential damages are the highest for orbital compartments located in the orbital bands of altitude/inclination: 550–2000 km/52–54°, 1,200–2000 km/86–88°, 400–2000 km/96–100°, because of the downstream location of Starlink constellation, OneWeb constellation, and earth observation satellites, respectively. The proposed set of CFs can be used in the LCA of different space systems in order to include impacts and damages related to space debris, along with other environmental impacts.
This original development fully in line with the standardized LCIA framework would have potential for further integration into harmonised sector-specific rules for the European space sector such as product environmental footprint category rules (PEFCR).
... This aspect, i.e. looking at the effects on operational satellites specifically instead of at the environment as a whole, is what differentiate this formulation from other available space debris indices. The reason for this choice is to switch from a generic debris risk to a more specific collision risk, which resonates more directly with operators [41]. In this sense, an object with a high index is characterized as one having a large impact on other operators' activities and push operators to act to reduce the numbers of such instances. ...
The ever-increasing amount of space debris continues to pose a threat to valuable space assets. The reliance on space assets coupled with an expected growth of large constellations of micro-satellites and nano-satellites emphasize the critical need to foster responsible behaviour by all actors to ensure long-term sustainability of the space environment. The Space Sustainability Rating (SSR) was first conceptualized within the World Economic Forum Global Future Council on Space Technologies. The SSR aims to provide a new, innovative way of addressing the orbital challenge by encouraging responsible behaviour in space through increasing transparency of actors' debris mitigation efforts designed to support long-term sustainability of the space environment. This paper presents the work of an international and interdisciplinary team to contribute to the early definition of the technical element and operations of the SSR. The paper presents the SSR design methodology to provide a comprehensive rating for sustainability of space missions in the context of the general status of the environment and global level of adherence to space debris mitigation practices. The SSR would act as a voluntary mechanism, whereby actors undergo an evaluation of their mission through a questionnaire; existing indices and other information should be used in addition to a specific questionnaire in establishing a rating. By sharing its rating, the actor would provide a single point of reference externally for their mission, thereby increasing transparency and placing emphasis on its debris mitigation approach, without disclosing any mission-sensitive or proprietary information. The rating will act as a differentiator and trigger positive outcomes (e.g., impact insurance cost or funding conditions), incentivizing other actors to improve their behaviour. The design, development and implementation of the SSR requires a number of steps including the creation of a technological platform among the space actors to ensure awareness, promote positive concepts and guarantee transparency of the approach. Based on input from different stakeholders (eg. governments, regulators, space agencies, industry trade associations etc.), the paper proposes potential steps to design the technical metrics and parameters of the SSR. The paper further explores the feasibility of the SSR to positively impact elements of the Space value chain-from manufacturers and insurers to launch providers and operators, as well as end customers.
Neglecting small fragments in space debris evolutionary models can lead to a significant underestimation of the collision risk for operational satellites. However, when scaling down to the millimetre range, the debris population grows to over a hundred million objects, making deterministic approaches too computationally expensive. On the contrary, probabilistic models provide a more efficient alternative, which however typically works under some simplifying assumptions on the dynamics, limiting their field of applicability. This work proposes an extension of the density-based collision risk models to any orbital dynamics and impact geometry. The impact rate with a target satellite is derived from a multi-dimensional phase space density function in orbital elements, which discretely varies over both phase space and time. The assumption of a bin-wise constant cloud density allows for the analytical transformation of the six-dimensional distribution in orbital elements into the three-dimensional spatial density function, guaranteeing an efficient and accurate evaluation of the fragments flux. The proposed method is applied to the assessment of the collision risk posed by occurred fragmentation events in different orbital regions on a high-risk target object. The effect on the impact rate of the modelling improvements, compared to previous probabilistic formulations, is discussed.
The space sector is a new area of development for Life Cycle Assessment (LCA) studies. However, it deals with strong particularities which complicate the use of LCA. One of the most important is that the space industry is the only human activity crossing all stages of the atmosphere during the launch event or the atmospheric re-entry. As a result, interactions occur not only with the natural environment but also with the orbital environment during the use phase and the end-of-life of space missions. In this context, there is a lack of indicators and methods to characterise the complete life-cycle of space systems including their impact on the orbital environment. The end-of-life of spacecraft is of particular concern: space debris proliferation is today a concrete threat for all space activities. Therefore, the proposed work aims at characterising the orbital environment in term of space debris crossing the orbital resource. A complete methodology and a set of characterisation factors at midpoint level are provided. They are based on two factors: (i) the exposure to space debris in a given orbit and (ii) the severity of a potential spacecraft break-up leading to the release of new debris in the orbital environment. Then, we demonstrate the feasibility of such approach through three theoretical post-mission disposal scenarios based on the Sentinel-1A mission parameters. The results are discussed against the propellant consumption needed in each case with the purpose of addressing potential ‘burden shifting’ that could occur between the Earth environment and the orbital one.
