Asteroid mining has been proposed as an approach to complement Earth-based supplies of rare earth metals and to supply resources in space, such as water. However, existing studies on the economic ...viability of asteroid mining do not provide much guidance on which technological improvements would be needed for increasing its economic viability. This paper develops a techno-economic analysis of asteroid mining with the objective of providing basic recommendations for future technology development and performance improvements. Both, providing water in space as well as returning platinum to Earth are considered. Starting from first principles of techno-economic analysis, gradually additional economic and technological factors are added to the analysis model. Applied to mining missions involving spacecraft reuse, learning curve effect, and multiple spacecraft, their economic viability is assessed. A sensitivity analysis with respect to throughput rate, spacecraft mass, and resource price is performed. Furthermore, a sample asteroid mining architecture for volatiles based on small CubeSat-class spacecraft is presented. It is concluded that key technological drivers for asteroid mining missions are throughput rate, number of spacecraft per mission, and the rate in which successive missions are conducted. Furthermore, for returning platinum to Earth, market reaction strongly influences its economic viability and it seems to be economically viable only under unlikely conditions.
•Extended profitability model for asteroid mining is proposed.•Application to water and platinum mining.•Mining missions with multiple spacecraft per mission and reuse look promising.•Viability of returning resources to Earth depends on market reaction.
Forming and sustaining an industrial symbiosis depends on several actors. Actors that have an interest in the symbiosis and the possibility to influence it are called “stakeholders”. According to ...social exchange theory and resource dependence theory, the power of actors in a network depends on the dependence of other actors on the resources they control. We adapt the stakeholder value network approach from the strategic management literature to the industrial symbiosis context as a means to provide insights into the power of stakeholders of an industrial symbiosis. The approach is applied to a waste incinerator steam network symbiosis case study in France, which has been successfully operated and extended over decades. The results from the case study show that using the stakeholder value network approach enables the assessment of the relative power of symbiosis stakeholders and the identification of key resources on which their power is based. We propose the application of the approach to further case studies in order to identify patterns in the power distribution within symbiosis networks.
•Analyze the power of stakeholders and resources in an industrial symbiosis.•Stakeholder value network approach adapted to industrial symbiosis.•Application of approach to incinerator symbiosis network in France.
The first definite interstellar object observed in our solar system was discovered in October of 2017 and was subsequently designated 1I/‘Oumuamua. In addition to its extrasolar origin, observations ...and analysis of this object indicate some unusual features which can only be explained by in-situ exploration. For this purpose, various spacecraft intercept missions have been proposed. Their propulsion schemes have been chemical, exploiting a Jupiter and Solar Oberth Maneuver (mission duration of 22 years) and also using Earth-based lasers to propel laser sails (1–2 years), both with launch dates in 2030. For the former, mission durations are quite prolonged and for the latter, the necessary laser infrastructure may not be in place by 2030. In this study Nuclear Thermal Propulsion (NTP) is examined for chasing interstellar objects after they have left the inner solar system, taking 1I/‘Oumuamua as an example. NTP has yet to materialise as far as real missions are concerned, but due to its research and development in the US government sponsored Rover/NERVA programs, actually has a higher Technology Readiness Level (TRL) than laser propulsion. Various solid reactor core options are studied, using either engines directly derived from these programs, or more advanced options, like a proposed particle bed nuclear thermal rocket (NTR). With specific impulses at least twice those of chemical rockets, NTP opens the opportunity for much higher ΔV budgets, allowing simpler and more direct, time-saving trajectories to be exploited. For example a spacecraft with an upgraded NERVA/Pewee-class NTR travelling along an Earth-Jupiter-1I trajectory, would reach 1I/‘Oumuamua within 14 years of a launch in 2031. The payload mass to 1I/’Oumuamua would be around 2.5 tonnes, but even larger masses and shorter mission durations can be achieved with some of the more advanced NTR options studied. In all 4 different proposed NTRs and 5 different trajectory scenarios are examined. It is concluded that NTP has the potential to increase payload size by an order of magnitude and trip durations reduced to < 15 years compared to > 20 years for chemical propulsion.
•Missions to 1I/‘Oumuamua using Nuclear Thermal Rockets are studied.•Four different NTR engines using LH2 and NH3 propellant are assumed.•Different trajectory options including direct transfer, are explored.•Results are assessed and reveal NTR is a potential game-changer for reaching ISOs.
Abstract
Background
Despite advancing automation, employees in many industrial and service occupations still have to perform physically intensive work that may have negative effects on the health of ...the musculoskeletal system. For targeted preventive measures, precise knowledge of the work postures and movements performed is necessary.
Methods
Prototype smart work clothes equipped with 15 inertial sensors were used to record reference body postures of 20 subjects. These reference postures were used to create a software-based posture classifier according to the Ovako Working Posture Analysing System (OWAS) by means of an evolutionary training algorithm.
Results
A total of 111,275 posture shots were recorded and used for training the classifier. The results show that smart workwear, with the help of evolutionary trained software classifiers, is in principle capable of detecting harmful postures of its wearer. The detection rate of the evolutionary trained classifier (
$$\bar{a}_{ccr} = 0.35$$
a
¯
ccr
=
0.35
for the postures of the back,
$$\bar{a}_{ccr} = 0.64$$
a
¯
ccr
=
0.64
for the arms, and
$$\bar{a}_{ccr} = 0.25$$
a
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=
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for the legs) outperforms that of a TensorFlow trained classifying neural network.
Conclusions
In principle, smart workwear – as prototypically shown in this paper – can be a helpful tool for assessing an individual’s risk for work-related musculoskeletal disorders. Numerous potential sources of error have been identified that can affect the detection accuracy of software classifiers required for this purpose.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
On 2019 August 30, a second interstellar object 2I/Borisov was discovered 2 years after the discovery of the first known interstellar object, 1I/’Oumuamua. Can we send a spacecraft to this object, ...using existing and near-term technologies? In this paper we assess the technical feasibility of a near-term mission to 2I/Borisov. We apply the Optimum Interplanetary Trajectory Software (OITS) tool to generate trajectories to 2I/Borisov. As results, we get the minimal ΔV trajectory with a launch date in 2018 July. For this trajectory, a Falcon Heavy launcher could have hauled an 8 ton spacecraft to 2I/Borisov. For a later launch date, results for a combined powered Jupiter flyby with a Solar Oberth maneuver are presented. For a launch in 2027, we could reach 2I/Borisov in 2052, using the Space Launch System (SLS), up-scaled Parker probe heat shield technology, and solid propulsion engines. Using a SLS a spacecraft with a mass of 765 kg could be sent to 2I/Borisov. A Falcon Heavy could deliver 202 kg to 2I/Borisov. Arrival times sooner than 2052 can potentially be achieved but with higher ΔV requirements and lower spacecraft payload masses. 2I/Borisov’s discovery shortly after the discovery of 1I/’Oumuamua implies that the next interstellar object might be discovered in the near future. The feasibility of a mission to both, 1I/’Oumuamua and 2I/Borisov using scaled versions of existing technologies indicates that missions to at least some future interstellar objects are feasible as well.
•Missions to Interstellar Object, 2I/Borisov are studied.•Chemical/High Impulsive Thrust Propulsion is assumed.•A direct trajectory as well as a Jupiter/Solar Oberth Maneuver are examined.•Viable missions are found using the NASA Space Launch System or the SpaceX Falcon Heavy.
The main benefit of an interstellar mission is to carry out in situ measurements within a target star system. To allow for extended in situ measurements, the spacecraft needs to be decelerated. One ...of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds. This leads to deceleration durations of several decades depending on the spacecraft mass. Within the context of Project Dragonfly, initiated by the Initiative of Interstellar Studies (i4is), this paper proposes a novel concept for decelerating a spacecraft on an interstellar mission by combining a magnetic sail with an electric sail. Combining the sails compensates for each technology's shortcomings: a magnetic sail is more effective at higher velocities than the electric sail, whereas an electric sail demonstrates superior performance at low speeds. It is shown that using both sails sequentially outperforms using only the magnetic or electric sail for various mission scenarios and velocity ranges, at a constant total spacecraft mass. For example, for decelerating from 5% c, to interplanetary velocities, a spacecraft with both sails needs about 29 years, whereas the electric sail alone would take 35 years and the magnetic sail about 40 years with a total spacecraft mass of 8250kg. Furthermore, it is assessed how the combined deceleration system affects the optimal overall mission architecture for different spacecraft masses and cruising speeds. Future work would investigate how operating both systems in parallel instead of sequentially would affect its performance. Moreover, uncertainties in the density of interstellar matter and sail properties need to be explored.
Self-replicating probes are spacecraft with the capacity to create copies of themselves. Self-replication would potentially allow for an exponential increase in the number of probes and thereby ...drastically improve the efficiency of space exploration. Despite this potential, an integrated assessment of self-replicating space probes has not been presented since the 1980s, and it is still unclear how far they are feasible. In this paper, we propose a concept for a partially self-replicating probe for space exploration based on current and near-term technologies, with a focus on small spacecraft. The purpose is to chart a path towards self-replication with near-term benefits, rather than attempting full self-replication. For this reason, components such as microchips and other microelectronic components are brought with the initial probe and are not replicated. We estimate that such a probe would be capable of replicating 70% of its mass. To further increase this percentage, we identify technology gaps which may be usefully addressed. We conclude that small-scale, partially self-replicating probes are feasible near-term. Their benefits would become significant in exploration missions requiring in the order of a dozen of probes.
•Self-replicating probes may enable exponentially accelerating space exploration•We present a concept for a near-term self-replicating probe•At least 70% of its dry mass can be replicated•Operations would be limited to the inner solar system•A technology roadmap for achieving full replication and interstellar exploration
The potential detection of phosphine in the atmosphere of Venus has reignited interest in the possibility of life aloft in this environment. If the cloud decks of Venus are indeed an abode of life, ...it should reside in the "habitable zone" between ∼50-60 km altitude, roughly coincident with the middle cloud deck, where the temperature and pressure (but not the atmospheric composition) are similar to conditions at the Earth's surface. We map out a precursor astrobiological mission to search for such putative lifeforms in situ with instrument balloons, which could be delivered to Venus via launch opportunities in 2022-2023. This mission would collect aerosol and dust samples by means of small balloons floating in the Venusian cloud deck and directly scrutinize whether they include any apparent biological materials and, if so, their shapes, sizes, and motility. Our balloon mission would also be equipped with a miniature mass spectrometer that should permit the detection of complex organic molecules. The mission is augmented by contextual cameras to search for macroscopic signatures of life in the Venusian atmospheric habitable zone. Finally, mass and power constraints permitting, radio interferometric determinations of the motion of the balloons in Venusian winds, together with in situ temperature and pressure measurements, will provide valuable insights into the poorly understood meteorology of the middle cloud region.
Digital platforms are an omnipresent phenomenon that challenges incumbents by changing how we consume and provide digital products and services. Whereas traditional firms create value within the ...boundaries of a company or a supply chain, digital platforms utilize an ecosystem of autonomous agents to co-create value. Scholars from various disciplines, such as economics, technology management, and information systems have taken different perspectives on digital platform ecosystems. In this Fundamentals article, we first synthesize research on digital platforms and digital platform ecosystems to provide a definition that integrates both concepts. Second, we use this definition to explain how different digital platform ecosystems vary according to three core building blocks: (1) platform ownership, (2) value-creating mechanisms, and (3) complementor autonomy. We conclude by giving an outlook on four overarching research areas that connect the building blocks: (1) technical properties and value creation; (2) complementor interaction with the ecosystem; (3) value capture; and (4) the make-or-join decision in digital platform ecosystems.
Quality assurance in research helps to ensure reliability and comparable results within a study. This includes reliable measurement equipment and data-processing. The Azure Kinect DK is a popular ...sensor used in studies with human subjects that tracks numerous joint positions with the Azure Kinect Body Tracking SDK. Prior experiments in literature indicate that light might influence the results of the body tracking. As similar light conditions are not always given in study protocols, the impact needs to be analyzed to ensure comparable results. We ran two experiments, one with four different light conditions and one with repeated measures of similar light conditions, and compared the results by calculating the random error of depth measurement, the mean distance error of the detected joint positions, and the distance between left and right ankle. The results showed that recordings with similar light conditions produce comparable results, with a maximum difference in the median value of mean distance error of 0.06 mm, while different light conditions result in inconsistent outcomes with a difference in the median value of mean distance error of up to 0.35 mm. Therefore, light might have an influence on the Azure Kinect and its body tracking. Especially additional infrared light appears to have a negative impact on the results. Therefore, we recommend recording various videos in a study under similar light conditions whenever possible, and avoiding additional sources of infrared light.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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