Aerospace Missions Research Articles

Hall-effect sensors functioning up to at least 600 degrees Celsius

After functioning successfully at 600 C, Hall-effect sensors show a full operational recovery, hinting towards potential applications in aerospace missions.

Experimental investigation of abnormal pressure drop in branch feedlines with a five-port spherical cavity in liquid oxygen engines

The stable and safe transport of liquid oxygen in a feeding system of cryogenic rockets is of great significance for the normal operation of aerospace missions, especially the multi-branch feedlines connected with multiple engines. During flight of a cryogenic rocket with four parallel engines, an abnormal pressure drop about 0.09 MPa was observed at the entrances of two symmetrical engines. Although this unusual phenomenon is within the control range of safe operation, it is still an unstable factor for the reliability of cryogenic engines. In order to reveal the mechanism of flow instability in the liquid oxygen feedlines with the five-port spherical cavity, an experimental system considering actual feedlines of a 1:1 model was set up. Three flow tests were performed with liquid oxygen as the working media to investigate the unstable flow behaviors. The theoretical and experimental results show that the abnormal pressure drop that is far greater than the normal resistance loss surely appears under a certain condition, which means that the pressure drop exists objectively. Through numerical simulation, it is found that the instability flow might be caused by formation of a longitudinal vorticity structure which is distributed at two symmetrical outlets of the five-port spherical cavity. The degree of abnormal pressure drop might be dependent on the dimension of the five-port structure, the fluid properties and the inlet conditions of liquid oxygen. As a result, the eddy dissipation caused by a perturbation needs to be considered in the design of cryogenic feeding systems besides the normal flow resistance loss. These results are of significance and can guide the design of complex feedlines for cryogenic rocket engines.

Thermal Analysis and Stability of Boron/Potassium Nitrate Pyrotechnic Composition at 180 °C

Aerospace missions require that pyrotechnic compositions are able to withstand 180 °C. Therefore, this paper studies the thermal stability and output performance of boron/potassium nitrate (abbreviated BPN) used in pyrotechnic devices. Firstly, differential scanning calorimetry (DSC) and thermogravimetric (TG) tests are used to analyze the thermal reaction process of KNO3, boron, and BPN to qualitatively judge their thermal stability. Then, apparent morphology analysis, component analysis, and the p-t curve test, which is the closed bomb test to measure the output power of the pyrotechnic composition, are carried out with BPN samples before and after the high-temperature test to verify BPN stability at 180 °C. The weight change of boron powder caused by chemical reactions occurs above 500 °C. When the temperature is lower than the peak exothermic temperature of decomposition, no obvious chemical reaction occurs with KNO3, and only physical changes (crystal transformation and melting) occur. Combined with a verification test at 180 °C for two days, it is concluded that boron and KNO3 components are stable at 180 °C. With an increase in boron content, the thermal stability of BPN is improved, with the best performance achieved when the ratio is 25:75 (B:KNO3). BPN samples without binder have the best thermal stability. In a test at 180 °C for five days, the binder affects the weight loss and p-t curve of BPN, and BPN with fluororubber binder is better than BPN with unsaturated polyester binder.

Evaluation of atomic oxygen effects on nano-coated carbon-carbon structures for re-entry applications

Since the beginning of Space Age, the re-entry phase represents a crucial task for both manned and unmanned aerospace missions. Along with high temperatures and plasma created by the spacecraft/atmosphere dramatic interaction, several issues must be considered in order to use new technologies and materials for re-entry systems. In particular, the effects of space environment due to ultraviolet (UV) and atomic oxygen (AO) have to be taken into account, in order to design and realize aerospace structures useful also for long duration missions. Such damaging factors, in fact, affect the spacecraft outer surfaces by degrading the thermo-mechanical properties of the materials designed to withstand re-entry conditions, thus frustrating their specific effectiveness. Carbon/Carbon (C/C) composites are widely used for high temperatures applications, including Thermal Protection Systems (TPS) for re-entry vehicles. In this work, a treatment of artificial aging was performed over in-house produced C/C material by means of AO ground facility at the Aerospace Systems Laboratory (LSA) of Sapienza University of Rome, evaluating erosion rate and surface oxides creation due to UV + AO irradiation. The experimental test was carried out setting the AO generator at a fluence of 8.7 × 1020 atoms/cm2, for an exposure time of 3000 equivalent sun hours. The material involved was manufactured by a customized vapor infiltration process; moreover, a protective coating was applied by using an aluminum oxide varnish charged with silicon di-oxide nano-spheres. The effect of coating is established by comparing with the results obtained for the uncoated material; an insight about the coating degradation due to the exposure is then assessed by morphological and chemical analyses.

Short note - assessment of the required human capacity factor using flight simulator as an appropriate accelerated test vehicle

Flight simulator can be employed as an appropriate and successful test vehicle that could be used to quantify, on the probabilistic basis, the required level of the human capacity factor (HCF) with respect to the expected mental workload (MWL) during fulfillment of a particular aerospace mission or in an extraordinary situation. In the analysis that follows it is shown how this could be done. The main concepts are illustrated by a numerical example.

Short note - adequate trust, human-capacity-factor, probability-distribution-function of human non-failure and its entropy

This note is an extension, a generalisation of and an attempt to quantify, on the probabilistic basis, the message of the recent Kaindl and Svetinovic (2019) publication Avoiding Undertrust and Overtrust. The author of the present analysis addresses some important aspects of the human-in-the-loop problem for safety-critical missions and situations, in which trust can be viewed as an essential part of the human-capacity-factor (HCF). This factor, as has been recently suggested, should be evaluated vs. mental workload (MWL), when there is a need to assure a successful and safe outcome of a particular human effort, such as, e.g., an aerospace mission or an extraordinary situation. The double exponential probability distribution function (DEPDF) for the random HCF is revisited. It is shown particularly that the entropy of this distribution, when applied to the trustee (a human, a technology, a methodology or a concept), can be viewed as an appropriate quantitative characteristic of the propensity of a decision maker to an under-trust or an over-trust judgment and, as a consequence of that, to the likelihood of making a mistake or an erroneous decision.

Short note - assessment of the required human capacity factor using flight simulator as an appropriate accelerated test vehicle

Flight simulator can be employed as an appropriate and successful test vehicle that could be used to quantify, on the probabilistic basis, the required level of the human capacity factor (HCF) with respect to the expected mental workload (MWL) during fulfillment of a particular aerospace mission or in an extraordinary situation. In the analysis that follows it is shown how this could be done. The main concepts are illustrated by a numerical example.

Hardware in the Loop Simulation for Model Predictive Control Applied to Satellite Attitude Control

Space systems are extremely complex and expensive robotic devices used in scientific, military and communication applications. Attitude control for aerospace systems is responsible for ensuring that the space object is in position, velocity and correct trajectories, stabilizing the spacecraft and guiding in the desired directions during the mission, regardless of external disturbances. Therefore, control systems design must satisfy the satellite’s operating requirements and deal with several physical constraints to guarantee safety and performance. In this paper, a parameterized Model Predictive Control (MPC) for attitude control of an artificial satellite is developed. The main feature of the proposed control scheme consists of obtaining an optimal solution at each sampling instant respecting structurally satellite operational constraints ensuring stability, tracking performance and operational reliability, which is a crucial point for aerospace missions. To address real-time operational conditions, Hardware-in-the-loop (HIL) technique was developed to test and validate an embedded MPC strategy under realistic implementation conditions.

MBSE for Satellite Communication System Architecting

The risk of failure for aerospace missions can be reduced if architects model the product in a systematic way and make decisions for physical implementation based on stakeholder needs. Satellite communication system architecting should take one of its dominating elements, the communication satellite, into account for consistent modeling during the whole product lifecycle. Model-based system engineering (MBSE) serves as a useful tool for system modeling activities and connections with manufacturing. In this paper, satellite communication system architecting is investigated in the preliminary design stage via MBSE methodologies and the system modeling language (SysML). Application scenarios and use cases are built up aiming at satisfying stakeholder needs. System black-box analysis and white-box logical decomposition are further realized. The logical architecture is then partitioned for physical implementation and system optimization is carried out to give architecting suggestions. Requirement traceability is examined to finish the current design stage. The models realized by the MBSE method are reusable and easily extendible to detailed system design and implementation in the whole product lifecycle.

Suppression of stray light based on energy information mining.

The star tracker plays a critical role in precision aerospace missions due to its high accuracy, absolute attitude output, and low power consumption. For an optical sensor, the problem of stray light is always an important research issue. A star energy information mining method for stray light suppression is proposed in this study. The gray-level co-occurrence matrix and k-nearest neighbor algorithm are adopted to identify the types of stray light that enter the optical system. Effective recognition of the stray light types is an important premise for the following steps. Then the parameters are optimized during background estimation. When star spots are extracted, the local differential encoding combined with Levenshtein distance filtering is conducted to eliminate the interference noise spots. The proposed algorithm can achieve accurate star spot extraction even when stray light exists in real night sky observation experiments.

Electronics and Packaging Intended for Emerging Harsh Environment Applications: A Review

Several industrial applications require specific electronic systems installed in harsh environments to perform measurements, monitoring, and control tasks such as in space exploration, aerospace missions, automotive industries, down-hole oil and gas industry, and geothermal power plants. The extreme environment could be surrounding high-, low-, and wide-range temperature, intense radiation, or even a combination of above conditions. We review, in this paper, the main leading applications that demand advanced technologies to fit the unconventional requirements of extreme operating conditions, discussing their main merits and limits compared to established and emerging technologies in this field, including silicon (Si), silicon on insulator (SOI), silicon germanium (SiGe), silicon carbide (SiC) as well as III–V semiconductors particularly the gallium nitride (GaN) semiconductor. In spite of successfully exceeding extreme conditions borders by developing advanced semiconductor devices dedicated for harsh environments, especially in high-temperature applications, the packaging challenges are still limiting the reliability of the developed technologies. Those challenges are examined in this review in terms of limitations and proposed solutions.

Aerospace Mission Outcome: Predictive Modeling

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Scalable bath cell method for reversible lithium management towards near zero volt tolerance in lithium-ion cells

Improving the safety of lithium-ion batteries has become an increasingly important issue in recent years due to a number of fires and other events including fires aboard airplanes, fires at storage facilities, and personal electronics fires. When in an inactive state, the safety of lithium ion batteries can be improved with methods unique from when the battery is in an active state due the battery not requiring stored energy to perform a task. Namely, completely discharging the cells of an inactive battery to a near zero volt state with an applied resistor can bring a number of safety advantages; 1) no rapid discharge from an internal/external short that can spark thermal runaway, 2) elimination of battery shorting and severe injury risk when assembling large battery packs with voltage >50 V, 3) low-risk, onboard storage of delayed-deployment batteries for aerospace missions, 4) inert battery for insertion of implantable medical devices and 5) enabling formulation of succinct, enforceable and comprehensive regulations for shipping and storing lithium-ion batteries. If lithium-ion batteries can be fabricated to tolerate a near zero volt state without performance loss they can also have improved general overdischarge tolerance, which can lend itself to several advantages beyond safety such as 1) dead-bus recovery, 2) recovery of difficult to access cells such as those in medical implants, 3) asset loss-prevention due to inadvertent overdischarge during storage, and 4) decrease in maintenance requirements for stored cells. It is well known that a near zero volt state in a conventional lithium-ion cell will lead to severe cell degradation, mainly due to dissolution of the anode copper current collector that results from the high potential (i.e. >3.1 V vs. Li/Li+) that the anode experiences when the cell is in the near zero volt state. Recent developments using reversible lithium management to prevent electrode damage in a near zero volt state have yielded LiCoO2/MCMB and HE5050/MCMB pouch cells with high tolerance to multiple 3 and 7 day near zero volt storage periods. Specifically, the amount of reversible lithium in a cell is modified during cell construction to prevent the anode potential from increasing to higher than the copper dissolution potential (i.e. 3.1 V vs. Li/Li+ at room temperature) and prevent the cathode potential from decreasing to less than the damage potential (1.3 V vs. Li/Li+ for LiCoO2) when the cell is in a near zero volt state. The amount of reversible lithium is iteratively modified based on feedback from reference electrode measurements. The reversible lithium management approach has several advantages over current commercial approaches in that it does not require secondary active materials, electrode/electrolyte additives, or alternative current collector materials. A reversible lithium management step was also recently integrated into a Solith® semi-automated pouch cell construction line to produce a cell-phone sized pouch cell that maintained nearly 100% of its discharge energy after a 14-day near zero volt storage period under a fixed resistive load. Thus, the reversible lithium management approach is scalable. A challenge present for the reversible lithium management approach to near zero volt storage tolerance is the detrimental changes of the cathode active material that can result from a low cathode potential (i.e. <1.5 V vs. Li/Li+) in a reversible lithium modified cell in a near zero volt state. Thus, strategies to suppress detrimental changes to the cathode material are important to further improving the reversible lithium management approach to near zero volt storage tolerance. A LiCoO2 cathode was over-inserted with lithium for 10 cycles (Constant current charge to 140 mAh/g, constant current discharge to 3.0 V vs. Li/Li+, fixed resistive load discharge to an additional 7 mAh/g) and found to fade to 96% of its original discharge energy. X-ray diffraction (XRD) data corroborated with previous studies shows that cation exchange in the octahedral layers occurs during the over-insertion of lithium and is responsible for the degraded performance. A solution deposited coating of AlPO4, known to stabilize LiCoO2 to charge potentials >4.2 V vs. Li/Li+, was applied to a LiCoO2 cathode and the same over-insertion cycling was performed. The AlPO2 coated LiCoO2 cathode maintained >99% of its discharge energy after 10 over-insertion cycles, and XRD data showed that the AlPO4 coating decreased the extent of irreversible cation exchange between the octahedral layers in the LiCoO2. Thus, AlPO4 surface coatings can prevent crystal structure changes detrimental to charge/discharge performance in LiCoO2 caused by over-insertion of lithium ions, which can improve the near zero volt storage tolerance of lithium ion cells for which reversible lithium management was applied during cell construction.

TC-42 Photonic Technology in Instrumentation and Measurement [Society News

Photonics plays a critical role in everyday life. Telecommunications, sensor technology, medicine and spectroscopy, to name a few, all rely on this 20th-century discovery. Photonic technology is increasingly used in instrumentation and measurement for applications in the oil and gas industry, electric power systems, aerospace missions, transport, civil structure, military, defense, ocean exploration, biomedical detection, environmental monitoring and other areas. The field is related to many of the fastest evolving engineering professions in a challenging time but with increasing opportunities.

Quantifying the roles of human error and his/her state-of-health: use of the double-exponential-probability-distribution-function

The probabilistic predictive modelling (PPM) approach in human-in-the-loop (HITL) related aerospace problems enables one to predict, quantify, assure and even specify the probability of the outcome of an aerospace mission or a situation when the performance of a never-perfect human, never-100%-reliable instrumentation (equipment), never absolutely predictable response of the object of control (aero or spacecraft), uncertain and often harsh environment, as well as the interaction (interfaces) of these uncertainties, contribute jointly to the likelihood of such an outcome. The objective of this paper is to generate thinking on how to advance the state-of-the-art in today's aerospace human psychology and particularly, on how to quantify, by both modelling and experimentation, the HITL related effort when the HF and equipment/instrumentation performance contribute jointly to the outcome (success and safety) of an aerospace mission or an extraordinary situation.

Quantifying the roles of human error and his/her state-of-health: use of the double-exponential-probability-distribution-function

The probabilistic predictive modelling (PPM) approach in human-in-the-loop (HITL) related aerospace problems enables one to predict, quantify, assure and even specify the probability of the outcome of an aerospace mission or a situation when the performance of a never-perfect human, never-100%-reliable instrumentation (equipment), never absolutely predictable response of the object of control (aero or spacecraft), uncertain and often harsh environment, as well as the interaction (interfaces) of these uncertainties, contribute jointly to the likelihood of such an outcome. The objective of this paper is to generate thinking on how to advance the state-of-the-art in today's aerospace human psychology and particularly, on how to quantify, by both modelling and experimentation, the HITL related effort when the HF and equipment/instrumentation performance contribute jointly to the outcome (success and safety) of an aerospace mission or an extraordinary situation.

CFD investigation on helium pressurization behaviors in liquid hydrogen tank

Pressurization system plays a significant role in aerospace missions, and non-condensable helium is usually used to provide pressurization effect to a cryogenic propellant tank. In the present paper, the helium effect on the pressurization behaviors of cryogenic propellant tanks are concerned and investigated, and an enhanced computational fluid dynamic (CFD) approach, which could simultaneously account for the species transfer as well as its effect on phase change, is introduced to assist the analysis. Two pressurization events, including depressurization after an active helium pressurization and pressurized discharge process, are selected as the research objectives, and the pressure responses, species concentration distribution, as well as mass transfer amount evolutions are obtained and analyzed. The results show that species transfer on pressure behaviors is strongly related to the pressurization time. When a pressurization lasts within several hundred seconds, the multicomponent effect generally has a relatively small influence on the thermodynamic performance. However, when the multispecies system experiences a longer time, the species transfer effect appears. For the depressurization performance after a pre-pressurization operation, the residual helium in the helium-existence case leads to a continuous liquid evaporation in the depressurization, while a pure hydrogen case experiences a vapor condensable process. Moreover, the helium and hydrogen could sufficiently diffuse with each other within the depressurization period. For a typical pressurized discharge process, the species diffusion as well as its effect on mass transfer rate affects the physical field distribution in a certain degree but a weak influence on the general pressurization performance. The specie concentration along radial direction causes a distinguishable radial temperature gradient. Generally, the present study gives a clear exhibition on the pressure and thermodynamic behaviors of pressurization using helium. Through the present CFD model, the multicomponent diffusion as well as its influence on phase change rate could be achieved.

Qualification extension of automotive smart power and digital ICs to harsh aerospace mission profiles: Gaps and opportunities

Historically the aerospace market has always chosen high level reliability solutions through customized technologies and processes, in order to cope with the requirement driven by mission profiles and application environment severity.In parallel, Automotive market required more and more high reliability targets. As a consequence, the qualification activity has evolved, passing from a stress driven approach strictly based on AEC-Q100 standard to a failure mode driven approach oriented to satisfy the robustness criteria required by TIER1 and Car Makers.Starting from this scenario, new market opportunities for Automotive devices can be identified, since the most reliable of them are today eligible to be sold to aerospace manufacturers with important cost saving thanks to massive production volumes of consolidated technologies.A gap may still persist and has to be carefully explored. First of all, a study of the different application constraints has to be carried out and the potential failure modes activated by Aerospace cold unbalanced mission profile, atmospheric pressure and radiations have to be analysed.Experimental evidences have been collected as first step on advanced CMOS technologies, and their extension to the smart-power families, where digital and power coexist together, will be shortly discussed in this paper.

Euresis-filter: a robust multiple-model FDI technique for small satellites' thruster faults

Fault detection and isolation (FDI) techniques are properties of critical importance for any aerospace missions where autonomy and fault identification (malfunction diagnosis) must be present all the time. Current work provides an extended presentation of the Euresis-filter, a multiple model-based FDI technique suitable for small satellites' thruster faults. The main scope of the proposed multiple model-based FDI function is to maintain the spacecraft (S/C) operational and safe (healthy status) as required by the mission, including the analysis, development and design of the Euresis-filter to the LPF model and Monte Carlo simulation results related to thruster faults. Results reveal that the Euresis-filter can serve as an advanced FDI and fault tolerance control (FTC) technique in terms of reliability, safety and mission success when compared to classical FDI/FDIR approaches.

Human-in-the-loop: application of the double exponential probability distribution function enables one to quantify the role of the human factor

The probabilistic predictive modelling approach in human-in-the-loop related aerospace problems enables one to predict, quantify, assure and even specify the probability of the favourable outcome of an aerospace mission or a situation, when the performance of the never perfect human, never 100%-reliable instrumentation (equipment), never absolutely predictable response of the object of control (aero- or space-craft), uncertain and often harsh environment, as well as the interaction (interfaces) of the above uncertainties, contribute jointly to the likelihood of such an outcome. As to the human factor, it includes two major aspects: human performance (error) and his/her state of health. While the reliability of the navigation instrumentation (equipment) could be evaluated using suitable and more or less well established modelling means, the role of the human factor, when quantification of the human role is critical, could be considered by using the double-exponential-probability-distribution-function (DEPDF).