Advances in Astronautics Science and Technology最新文献

With the increasing number of both functional and defunct space assets being present in orbit, and having a better understanding of the space environment, it is clear that there is a need for active debris removal (ADR) today if not in the very near future. Previous demonstrators have been successful such as the RemoveDEBRIS mission which was co-funded by the European Commission and produced by a set of partners. Airbus have also worked extensively on other projects to develop the capability to rendezvous and capture objects in space (such as the ATV with 5 successful flights, e-Deorbit, DEOS, and Space Tug). Airbus have been working with agencies and industry to create a removal service with the aim of being both technically feasible and at an attractive price point to potential customers. The capture solutions have been outlined and an example mission profile is shown for providing the service for a mega-constellation operator. With this setup, a total of 20+ spacecraft could be deorbited with a single ADR vehicle which would provide an affordable price point.

Regenerative cooling of thrust chamber is the unique solution for the thermal management of high heat flux generated inside the combustion chamber of Cryogenic rocket engine. Heat is transferred from combustion hot gas to coolant through the channels provided on inner copper shell, thereby cools the inner wall of the nozzle. A novel technique of providing copper foam inside the channels will act as an infinite fin and also act as barrier for coolant stratification. This will improve the heat transfer to the coolant and reduce the nozzle wall temperature. Heat transfer improvement with copper foam inserts to the coolant channel is demonstrated through experiments with simulated fluids. Experiments are conducted with simulated hot gas chamber and coolant channels using water as the coolant. Copper foam with high porosity is selected to fill the channels. Hot tests are carried out with copper foam filled coolant channels and measured the coolant temperature rise and pressure drop across the channels. Tests are repeated with similar hot gas condition, but without inserting copper foam inside the channels. A substantial enhancement in heat transfer to the coolant is observed with copper foam inserts experiments, which will reduce the wall temperature. This gives a good handle on the life cycle improvement of multi-start cryogenic engines for future space transportation systems. This paper details the specification of copper foam, hardware design, experiments and measurements, and the application of the augmentation of heat transfer coefficient in operating cryogenic engines.

Radioluminescent nuclear battery is an important representative type of indirect conversion in nuclear batteries. Design, fabrication, and performance optimization of such batteries have been studied in detail. The specific research contents including optimization of material parameters of fluorescent layers, fluorescent layer structure design, radioluminescent spectra regulation, and radioluminescence emission intensity enhancement. The electrical properties of nuclear batteries with different fluorescent layers were tested under beta particles and X-ray excitation. As the mass thickness of the fluorescent layer increases, the electrical performance parameters first increase and then decrease, and there is an optimal mass thickness. A series of ZnS:Cu phosphor layers with different structure geometric parameters were prepared by tape adhesion method. When the thickness of the phosphor layer is close to the radioactive particle range, a good output performance can be achieved. Moreover, the effect mechanism of nano-fluorescent materials has also been introduced to improve battery performance. CsPbBr₃ perovskite quantum dot thin film materials and their applications in the radioluminescent nuclear batteries have been studied. CsPbBr₃ can effectively enhance the spectral response coupling degree, and greatly improve the output power of the battery. Further, a novel type of radioluminescent material using CdSe/ZnS core–shell quantum dot coupled with Au nanoparticles was prepared. The results show that the nano-coupling system can indeed improve the luminescence emission intensity and battery output performance. This research work can provide a new direction for future space battery technology.

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.