Advances in Astronautics Science and Technology最新文献

Nowadays, numerous global spacecrafts are launched, transported, or served in marine environment, but corrosive chloride salts can attack their structures. It is considered in this paper that the chloride salt corrosion failure under low loads consists of pitting, pit-to-SCC transformation, SCC, and brittle–ductile fracture. During the pit-to-SCC transformation processes, the relationships among the normal stress on cleavage planes, the applied stress and the crystal orientations are expressed quantitatively on the basis of the crystallographic features. A typical brittle–ductile fracture mode is sequential or simultaneous occurrence of cleavage and shear. The stress intensity factor and the crack length are employed to evaluate the no-omen SCC and HE failure inside the structural solids. The corrosion area and depth, the weight change and the current density are often applied to characterization of general corrosion damage in multi-scale spacecraft structures. Further, the chloride salt corrosion should be protected systematically from three aspects of anti-corrosion materials, service environment, and concentrated stress. Meanwhile, the acidic cleaning processing must be forbidden to be used in the whole spacecraft life.

The sustainability of Outer Space in a context of increased human activity in low Earth orbit (“LEO”) has been much debated lately. The discussion focuses on how space debris appears, how they can be limited and, possibly, removed. Commercial proposals for Active Debris Removal (ADR) and providing life-extension services to satellites are slowly emerging as precursory technological tools. Those technologies will involve so-called on-orbit servicing activities (“OOS”), i.e., activities performed on a spacecraft, while it is in or near its operational orbit and will require that one spacecraft approach, rendezvous, and interact with the asset/the debris to be removed; they raise a host of legal, regulatory, and policy challenges that need to be discussed as those projects progressively mature. Those cutting-edge technologies have potent capabilities and a potential for military and missile technology applications. As a result, they will likely be controlled by export control regulations (possibly by US export control regulation) and might fall under the stringent ITAR requirements. OOS inevitably involves the coupling of two different actors, the servicing spacecraft performing the services, and the asset to service. From an export control perspective, depending on the circumstances of each mission, in particular on the nationality of the servicing spacecraft and the one of the debris, the exchange of information between them might qualify as an export of technical data and would need to be licensed and authorized accordingly. In addition, because of the coupling of those two actors, the OOS model presents an inherent complexity: it creates a greater risk of technical failures, in particular of on-orbit collisions. As a consequence, it can induce more opportunities to exchange technical data in a context of urgency that prompts omissions and ultimately, more opportunities for violating export controls. This would apply even if technical data are exchanged for insurance or investigation purposes. Thus, any situation of on-orbit failure in the context of an OOS presents a risk of inadvertent export control. In the past, inadequately managed launch-failure investigations of satellites launched on non-US launchers caused major export control violations and were to have a profound impact on the US export control system. After observing how technological measures can mitigate risks of export control violations, this paper will propose a normative suggestion to mitigate potential ITAR violations and to avoid inadvertent export control situations in case of on-orbit failures in the context of OOS.

Current investigations on space tethers include their application to space debris deorbiting, specifically on the set of manoeuvres performed by a chaser tug to change the orbital parameters of a target body. Targets can be cooperative spacecraft at the end of their life or uncontrolled objects such as defunct satellites without clearly available capturing interfaces. In this latter case, a link joining tug and target may be misaligned with the target body inertia axes, influencing the attitude of both bodies; in case of rigid links, torques transmitted during tugging operations may overcome the tug attitude control system. This issue is clearly less significant in case of non-rigid connections, such as tethers; furthermore, with such connections the chaser can remain at a safe distance from the target during the whole deorbiting operation. On the other side, the initial phase of tethered space debris removal manoeuvres can be influenced by transient events, such as sudden tether tension spikes, that may cause longitudinal and lateral oscillations and, in case of resonance with the target attitude dynamics, could represent a serious issue for tug safety. In this paper it is proposed to provide the tug with a tether deployer mechanism capable to perform reel-in and reel-out, smoothing loads transmission to the target and damping oscillations. This concept is validated through a representative test campaign performed with the SPAcecRraft Testbed for Autonomous proximity operatioNs experimentS (SPARTANS) on a low friction table. A prototype of the deployer is manufactured and the deployment and rewind of a thin aluminium tape tether is proven. Test results include the verification of the tether visco-elastic characteristics with the direct measurement of spikes and oscillations and the estimation of the proposed system damping capabilities.

Nanomaterials and nanostructures have a broad impact on space missions and programs (e.g., launchers, planetary science, and exploration). Their main benefits are related to reduced vehicle mass improved functionality and durability of space systems and increased propulsion performance. For these reasons, in this paper, we would like to explore the recent evolutions of nanomaterials and nanostructures for space systems, with a focus on patents and market trends related to lightweight structures, damage-tolerant nanoscale systems, nanocoatings and adhesives, nanomaterials, and structures for thermal protection and control. Our analysis examines patent information from a database containing more than 54 M worldwide patent families and combines the data retrieved with market indicators. Such evaluation is useful to assess the technological trends and evaluate their current stage of maturity, within the overall Technology Life Cycle. Using specific sectoral keywords, our study takes into consideration about 3000 patent data on nanostructures, materials, and processes for space applications evaluating, among others, patents trends (2010–2019), International Patent Classifications, country distribution, top assignees, legal state, and forward and backward citations. As a result, we can assess which International Patent Classification is more common and which geographical area is more active. In the area under investigation, we identified that explosives and similar materials (C06B) are widely protected as well as heterocyclic compounds (C07D) and spacecraft and its related equipment (B64G). For what the geographical distribution is concerned, while China and United States confirm their predominance, it is worthwhile noticing that Canada, one of the ESA Member States, is highly active, as well. Our focus on the European patenting activity shows that Great Britain, Germany, and France are the most active countries. From the analysis of the other indicators (e.g., citations, assignees, etc.), we can assess which type of nanomaterial and nanostructure for space applications is growing more rapidly. Furthermore, patent indicators, integrated with market information, provide a clear evaluation of the related technology trends and readiness level. In conclusion, patent metrics provide a valuable asset to measure innovation performance. These data can also be used to monitor activities of worldwide players, create a performance evaluation system in R&D entities, and foresee specific technological trends. Thanks to this type of analysis, we can capture differences in innovation performances. The resulting indicators support strategic roadmapping and contribute to mapping knowledge and competences worldwide. In addition, they provide information on technological gaps and possible opportunities, measuring the results of space valorisation and technology transfer.

A formulation, based on indirect approach, that uses both the aerodynamic angles: angle of attack and bank angle as control variables and maximizes the parachute deployment altitude of a Mars entry vehicle is presented. The complexity of handling the control variable ‘angle of attack’ in the indirect approach is overcome by expressing the aerodynamics coefficients as a quadratic polynomial of angle of attack. The problem is formulated as a two point boundary value problem using the Pontryagin’s principle of the optimal control theory. The solution is obtained using differential evolution technique, a heuristic optimization technique. This is an alternative formulation to the commonly used direct approach using non-linear programming. The solution procedure based on indirect approach reduces the number of unknowns drastically compared to the direct approach. The benefit of using angle of attack modulation in addition to bank angle modulation is quantified. The implication of constraints on minimum allowable altitude and maximum deceleration on the optimized trajectory is analyzed using the new formulation and the solution approach.

A radioisotope thermoelectric generator (RTG) is a device that directly converts the decay heat of a radioisotope into electrical energy using the Seebeck effect of a thermoelectric material. The constant decay of the radioisotope heat source produces heat as a system energy source. The thermoelectric module uses materials to obtain electric energy by Seebeck effect. The structure and size of the thermoelectric converter need to be optimized for different radioisotope heat sources. The power has stable output performance, sustainable operation, and strong environmental adaptability. Space micro-scientific instruments require power supplies that are sustainable, stable, and long-life. The micro radioisotope thermoelectric generator can be invoked as a sustainable long-life power supply in low-power device applications. The miniaturized RTG can be applied in long-term service meteorological/seismic monitoring stations that are widely distributed on the surface of the planet, small landing vehicles at extreme latitudes or areas with low solar flux, atmospheric-surface-flow monitoring systems, underground detectors, deep space micro spacecraft, wireless sensor networks, self-powered radiation sensors, deep-space robot probes, and radio observatories on the lunar surface. This study innovatively proposes micro stacked-integrated annular-radial radioisotope thermoelectric generator and prepares an integrated prototype to drive an RF2500-based radiofrequency wireless sensor network, and monitors the temperature of each node for a long time as a demonstration. A high-performance micro radioisotope thermoelectric generators module based on the flexible printed circuit and bismuth telluride thick film was designed and prepared by screen printing. They are tested by a loading electrically heated equivalent radioisotope heat source. The output performance of the micro-RTG at different ambient temperatures is further evaluated. When loaded with ²³⁸PuO₂ radioisotope heat sources, an integrated prototype would generate an open-circuit voltage of 0.815 V, a short-circuit current of 0.551 mA, and an output power of 114.38 µW at 0.408 V. When loaded with a ⁹⁰SrTiO₃ or ²⁴¹AmO₂ radioisotope heat source, the prototype produced 66.38% and 6.15% of the output power (compared to ²³⁸PuO₂), respectively. In the impact evaluation on ambient temperature, the electrical output performance of the prototype increases with increasing temperature (− 30 to 120 °C). In the evaluation of the effects of long-term radioisotope irradiation, the output performance decreased slightly as the irradiation dose was increased during the service period. The stack-integrated micro radioisotope thermoelectric generator developed in this study is expected to provide reliable power support for space micro-scientific instruments, especially distributed wireless sensor networks.

This paper extends the analysis of empirical methods for describing vehicle–terrain interactions in lunar terrain. Given analytical formulation to predict mobility performance in extraterrestrial environments requires reliable in situ testing campaigns, this imposes fundamental restrictions to conceive a more consolidated theory, and further any possibility to use improved empirical methods to design better space hardware. Hence, we propose an analytical approach to extrapolate data taken in parabolic flights to model vehicle performance in multiple gravity regimes. The extrapolation technique and respective reported uncertainties can be used, therefore, to tune fitting parameters of a set of general formulas in the domain of Terramechanics, allowing to have empirical estimates of the wheel mobility in cases where testing is inherently very complex. Finally, by the analysis of previous Moon and Mars rover missions with the fitted equations, we report an empirical design criterion that allows to generate first estimates of the optimal wheel dimensions, taking into account the eventual longitudinal slip of the rover and including the desired mass of the payload. The introduced rules for geometry optimization can be important for future space rover missions in remote soils.

Rovers, ultimate automobile for the investigation of the nearby planetary group, are capable of assisting researchers in their exploration as well as the breakdown of the formation of Mars. In this research, we are proposing a model of wanderer which is fit for self-adjusting to various landscapes along with environments with the end goal of fruitful investigation. In addition, it is designed to make a trip to various zones, gather earth samples, measure pH, compute weight, screen different states of weather such as warmth, dampness and wind velocity, sense the formation of toxic gas, and not to mention conduct rescue mission. Notably, the wheels are constructed using buoyant substances like polyvinyl chloride (PVC). Moreover, a unique suspension framework is designed on the basis of the modified rocker-bogie system to make the wanderer adaptive to the uneven surface of Mars. Besides, a global positioning system (GPS) is incorporated with the vehicle so that its movement can be tracked and the prototype can roam autonomously. In other words, the rover is capable of conducting self-sustained exploration even if the condition is inhospitable. Another key point is that the proposed prototype is more cost-effective than the existing ones which have already been reported in the literature. As a result, the suggested model may have a decent potential not only in space exploration but also in the quest of life on Mars.

The United Nations’ Committee on the Peaceful Uses of Outer Space (COPUOS), through its consensus process, has accomplished much over the decades, most notably helping to produce the five space treaties and related guiding principles. But it has been unable to produce the international framework of laws that the Moon Treaty calls for to facilitate humanity’s departure from the home planet. This has created a gap in space law that has had a detrimental effect on private activity in outer space. The Moon Treaty, with the proper implementation agreement, now offers the best hope for closing that gap. Such an agreement would need to address many issues, most involving private enterprise and settlements. Although some argue that the Moon Treaty would hinder private space activities, with the proper IA, it would in fact support them. The Space Treaty Project has proposed a ten-paragraph Implementation Agreement that is based on four organizational principles: (1) The Agreement must be comprehensive and support all private activity; (2) The Grand Bargain: Trade private property rights for public policy obligations; (3) Defer issues currently at impasse (e.g., monetary sharing of benefits) by creating a governance process for making future decisions; (4) Build upon and integrate current institutions and processes. Why is this proposal necessary? As of January 2020, there is no internationally recognized mechanism for granting property rights to anyone for any location or natural object in outer space. The current controlling international law is the Outer Space Treaty of 1967, which prohibits any one country from appropriating anything in outer space: “Article II: Outer space, including the moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.” Many countries agree that the prohibition against appropriation prevents any one country from granting property rights on its own authority. Some disagree, enough to create a potential for conflict and uncertainty for businesses and investors. Since the functions of law include avoiding conflicts and reducing uncertainties, it is imperative to create an international legal framework for private activity in outer space. The Moon Treaty provides the international authority to grant property rights. Article 11 does not prohibit ownership; it just prohibits any one country from granting it on its own authority. It is important to note that Article 11 begins by stating that the “common heritage of mankind” is defined by the Moon Treaty and its implementation agreement. The CHM has no legal meaning or force of law beyond the framework that the States Parties adopt. The proposed Implementation Agreement provides the minimum framework of international law that is necessary at this time for public and private activity on the Moon and beyond. The hopes and dreams of individuals and groups to create new societies in out