Ground-based Testing Research Articles

Personnel Risk in Assessing the Effectiveness of Ground-based Tests of Complex Technical Systems

The article provides an original approach to taking into account the risk ofpersonnel in the process of assessing the effectiveness of testing complextechnical systems. Models of assessment and predictive models of personnelrisks based on the study of their qualification level are considered. The advan-tages and limitations of the given approach to the analysis and accounting ofpersonnel risks are shown.

An analytical method for the dynamic response prediction and produced test modes generated by vibro-shock test benches

This article describes a methodology for the computational forecasting of dynamic characteristics and test modes, implemented by vibro-shock stands of explosive action. Vibro-shock stands are widely used in ground-based experimental testing of onboard equipment of spacecraft for non-stationary broadband impact arising from the operation of pyrotechnic separation means. The principle of operation of these stands is based on the excitation of an intense non-stationary broadband vibration mode using an explosive energy source in a system of elastic-inertial elements (resonator), affecting the test object. The presented analytical technique is used to predict the test modes implemented by the vibro-shock stand in the form of a shock spectrum and for pre-test calculations in order to adjust the characteristics of the stand, ensuring the implementation of the necessary test modes. The reliability of the calculation results performed according to this technique is confirmed by experimental data. Key words: dynamic stiffness, method of initial parameters, shock loading, pyrotechnic separation means, ground experimental development, vibro-shock strength, vibro-shock stands of explosive action.

Means of measurement of heat flows in thermal vacuum research and testing of products of space engineering

We present the results of the comparative analysis of the characteristics of the domestic-made heat flux sensor PTP-1B with widely used foreign-made area sensor FOA-020. The conditions are typical to the ground-based thermovacuum research and testing of space technology products, conducted in the absence of validated converter-sensors of the aggregated heat flux within the density range of up to 2000 W/sq. m and a spectral range of 0.2 - 20 µm. Experimental studies were performed in a thermal vacuum chamber of the experimental stand TEC-2.5 at the temperature of its internal surfaces of 20 0C. Recommendations regarding the possible use of the PTP-1B sensor as a working instrument of measurements in monitoring and diagnostic systems during the processes of ground testing of space technology objects are given

Plume Contamination Measurements of an Additively Printed, Green-Propellant Hybrid Thruster

The dielectric breakdown properties of additively printed acrylonitrile butadiene styrene are leveraged to develop a green hybrid thruster family with capability for on-demand start, stop, and restart. Because acrylonitrile butadiene styrene is a new material for propulsion applications, no exhaust plume database exists, and the associated contamination potential for spacecraft surfaces is unknown. Analytical calculations of associated exhaust plume species are presented to identify predicted concentrations of primary condensable species , , and carbon (soot). When the hybrid thruster is operated near optimal equivalence ratio, the analytical studies show that combined mass concentrations of and constitute between 10 and 35% of total exhaust plume. Condensable carbon does not occur. This result is compared to 50% or greater mass concentrations of condensable species, and residual , for monopropellant hydrazine. Thus, the 3-D printed hybrid fuel is likely to burn cleaner than hydrazine. Results from ground-based and space-flight plume contamination experiments are presented. The contaminant sensor uses a light-sensitive photoresistor, mounted behind a quartz glass window to simulate spacecraft optical surfaces. Ground-based tests demonstrate approximately 12–13% optical attenuation after a 10-pulse burn sequence. Space flight data collected from a five-pulse burn sequence demonstrate optical attenuation levels approximately 2% higher.

Active Tissue Equivalent Dosimeter: A Tissue Equivalent Proportional Counter flown onboard the International Space Station

The Active Tissue Equivalent Dosimeter (ATED) is a low-cost, easy-to-use and compact tissue equivalent proportional counter designed for use aboard spacecraft, satellites, aircraft, unmanned aerial vehicles and high-altitude balloons. ATED was rigorously tested at particle accelerator facilities utilizing heavy ions of charge and energy similar to Galactic Cosmic Rays (GCRs). Upon completion of the ground-based testing and calibration, the ATED was operated aboard the International Space Station (ISS) during July–August of 2018. ATED measurements from the ISS were then analyzed in terms of time, latitude, longitude, and altitude in order to correlate with the radiation fields in the ISS orbit. When ATED measurements were correlated with orbital position, elevated absorbed dose rates due to the South Atlantic Anomaly (SAA) were clearly evident. ATED measurements were also separated based on their orbital location into three different regions. The results from the July–August 2018 flight show that ATED functioned as designed while onboard the ISS. The hypothesis that lineal energy and linear energy transfer can be used interchangeably with measurements by a TEPC in Low Earth Orbit (LEO) was tested by ATED measurements. Lastly, a direct comparison was made between linear energy transfer (LET) converted from lineal energy spectra from a spherical TEPC in LEO and model-calculated LET values. Such a comparison is highly challenging with the TEPCs with cylindrical geometry previously used in space.

Aerothermal databases and load predictions for Retro Propulsion-Assisted Launch Vehicles (RETALT)

The assessment of thermal loads occurring on reusable launch vehicles during the entire trajectory is essential for the correct dimensioning of the thermal protection system. Due to the costs and limitations of ground-based testing for large-scale vehicles, these predictions rely intensively on numerical simulations (CFD). The need of aero-thermal databases, as a fast-response surrogate model for the aero-thermodynamic heating, arises from the practical impossibility of performing unsteady CFD analysis over the entire trajectory due to the large disparity of fluid mechanical and structural time scales. The construction of these databases is based on a representative set of CFD simulations which cover, at a minimum, the flight regimes with significant thermal loads. The aim of this paper is to analyse the results of these representative CFD simulations during both the ascent flight and atmospheric entry for the RETALT1 vehicle to show typical flow field phenomena occurring during these phases and the resulting heating patterns.

Assessment of the State of Forests Based on Joint Statistical Processing of Sentinel-2B Remote Sensing Data and the Data from Network of Ground-Based ICP-Forests Sample Plots

The research was carried out on the territory of the Karelian Isthmus of the Leningrad Region using Sentinel-2B images and data from a network of ground sample plots. The ground sample plots are located in the studied territory mainly in a regular manner, laid and surveyed according to the ICP-Forests methodology with some additions. The total area of the sample plots is a small part of the entire study area. One of the objectives of the study was to determine the possibility of using the k-NN (nearest neighbor method) to assess the state of forests throughout the whole studied territory by joint statistical processing of data from ground sample plots and Sentinel-2B imagery. The data of the ground-based sample plots were divided into 2 equal parts, one for the application of the k-NN method, the second for checking the results of the method application. The systematic error in determining the mean damage class of the tree stands on sample plots by the k-NN method turned out to be zero, the random error is equal to one point. These results offer a possibility to determine the state of the forest in the entire study area. The second objective of the study was to examine the possibility of using the short-wave vegetation index (SWVI) to assess the state of forests. As a result, a close statistically reliable dependence of the average score of the state of plantations and the value of the SWVI index was established, which makes it possible to use the established relationship to determine the state of forests throughout the studied territory. The joint use and statistical processing of remotely sensed data and ground-based test areas by the two studied methods make it possible to assess the state of forests throughout the large studied area within the image. The results obtained can be used to monitor the state of forests in large areas and design appropriate forestry protective measures.

Теоретическая оценка времени захолаживания бака жидкого водорода при испытании на прочность

Russian enterprises continue developing rocket and space vehicles based on cryogenic propellants, i.e. liquid hydrogen, oxygen, and methane. Hence, the issues of fuel tanks’ thermal strength are increasingly important. During structural tests, the operating temperatures of the test object should be simulated, since the temperature condition affects the strength and rigidity of the structure. Consequently, during ground-based experimental tests, hydrogen tanks must be cooled down to 20 K, the boiling point of hydrogen. JSC TsNIIMash is developing a helium system capable of cooling large-sized structures to a temperature of 20 K. Helium can be used in a gaseous state to cool down the structure, since the boiling point of helium, 4 K, is lower than the boiling point of hydrogen. Until now, the tanks were cooled only by filling with liquid nitrogen, therefore the temperature state of the tanks during the tests was simulated only for this case. In order to determine the applicability of the method developed, the cooling time of large-sized containers was estimated by cooling a hydrogen tank, which by its dimensions is typical for an advanced medium-class second stage launcher, to 20 K by gaseous helium.

Teleoperation and Visualization Interfaces for Remote Intervention in Space

Approaches to robotic manufacturing, assembly, and servicing of in-space assets range from autonomous operation to direct teleoperation, with many forms of semi-autonomous teleoperation in between. Because most approaches require one or more human operators at some level, it is important to explore the control and visualization interfaces available to those operators, taking into account the challenges due to significant telemetry time delay. We consider one motivating application of remote teleoperation, which is ground-based control of a robot on-orbit for satellite servicing. This paper presents a model-based architecture that: 1) improves visualization and situation awareness, 2) enables more effective human/robot interaction and control, and 3) detects task failures based on anomalous sensor feedback. We illustrate elements of the architecture by drawing on 10 years of our research in this area. The paper further reports the results of several multi-user experiments to evaluate the model-based architecture, on ground-based test platforms, for satellite servicing tasks subject to round-trip communication latencies of several seconds. The most significant performance gains were obtained by enhancing the operators’ situation awareness via improved visualization and by enabling them to precisely specify intended motion. In contrast, changes to the control interface, including model-mediated control or an immersive 3D environment, often reduced the reported task load but did not significantly improve task performance. Considering the challenges of fully autonomous intervention, we expect that some form of teleoperation will continue to be necessary for robotic in-situ servicing, assembly, and manufacturing tasks for the foreseeable future. We propose that effective teleoperation can be enabled by modeling the remote environment, providing operators with a fused view of the real environment and virtual model, and incorporating interfaces and control strategies that enable interactive planning, precise operation, and prompt detection of errors.

Evaluation of burning rate in microgravity based on the fuel regression, flame area, and spread rate

The fuel burning rate and heat-release rate (HRR) play key roles in determining the fire intensity and hazard. On Earth, the burning rate of a condensed fuel is normally measured by the mass loss, but in microgravity, the impossibility of measuring the weight loss with a balance makes the measurement of burning rate challenging. This work proposes three methods to quantify the burning rate of condensed fuels in microgravity by measuring (i) the regression rate of the fuel surface, (ii) the spread rate of the flame leading edge, and (iii) the flame-sheet area, which all rely on video imaging of the flame or fuel surface geometry. The accuracies of these methods are quantified first in the ground-based tests with representative fuels, 1) solid candle and PMMA rods with diameters from 8 to 15 mm, 2) liquid fuels including propanol, hexane, and kerosene, and 3) the methane and propane gases. Results show that the burning rate obtained optically by tracking the flame leading edge and the fuel regression were less accurate due to strong sensitivity to camera resolution and background light. Comparatively, measuring the flame-sheet area is easier and gives more accurate results, and microgravity PMMA-rod flame (BASS-II project in the International Space Station) show that the fuel mass flux across the flame sheet is almost constant (0.15 mg/cm2-s) for a given fuel configuration and environment. This work offers a useful way to measure fuel burning rate and HRR in spacecraft and provides a path for the performance-based spacecraft fire safety design.

The Ground-Based BIOMEX Experiment Verification Tests for Life Detection on Mars.

The success of an astrobiological search for life campaign on Mars, or other planetary bodies in the Solar System, relies on the detectability of past or present microbial life traces, namely, biosignatures. Spectroscopic methods require little or no sample preparation, can be repeated almost endlessly, and can be performed in contact or even remotely. Such methods are therefore ideally suited to use for the detection of biosignatures, which can be confirmed with supporting instrumentation. Here, we discuss the use of Raman and Fourier Transform Infrared (FT-IR) spectroscopies for the detection and characterization of biosignatures from colonies of the fungus Cryomyces antarcticus, grown on Martian analogues and exposed to increasing doses of UV irradiation under dried conditions. The results report significant UV-induced DNA damage, but the non-exceeding of thresholds for allowing DNA amplification and detection, while the spectral properties of the fungal melanin remained unaltered, and pigment detection and identification was achieved via complementary analytical techniques. Finally, this work found that fungal cell wall compounds, likely chitin, were not degraded, and were still detectable even after high UV irradiation doses. The implications for the preservation and detection of biosignatures in extraterrestrial environments are discussed.

Ground-Based Testing of the Lunar Manipulator Complex of the Luna-25 Project

Ground-Based Testing of the Lunar Manipulator Complex of the Luna-25 Project

Stages of information support of development of on-board equipment for spacecraft

The ground-experimental testing of the elements of space technology is a crucial stage in the creation of space products, in fact, this is the ground «flight» of the devices being created. And how well the operating conditions will be reproduced at this stage and the successful functioning of the devices under the expected conditions is ensured, its successful operation in real flight during the service life depends. The radio electronic devices of the onboard equipment of the spacecraft are one of the essential elements that ensure the fulfillment of target tasks, which should confirm their readiness for the forthcoming work at the stage of groundbased experimental testing. The article discusses the stages of information support for the development of spacecraft onboard equipment, showing the ways to improve the technology of ground-based experimental testing of spacecraft onboard equipment. It is shown that at the present stage of development of the space industry, it has become possible to introduce the methodology of mathematical planning of an experiment into engineering practice. A backlog of applied work on radio-electronic topics h as appeared, showing the possibility of revealing in a full factorial experiment the influence of internal uncontrollable parameters (factors) of electronic components on the experimental results. This removed the obstacle to the implementation of the capabilities of the method in research and improvement of radio electronic devices onboard equipment.

On simulating the effect of gravity on concurrent flame spread over thin paper through variations in ambient pressure

The environment inside a spacecraft, or a space habitat, can greatly differ from those on earth, affecting the burning behavior of solid fuels. Because in a gravity field there is a flame-induced buoyancy, it is very difficult to reproduce on Earth the environmental conditions of a spacecraft, or a habitat in the Moon or Mars, thus making fire testing and burning predictions harder. A potential alternative approach to overcome this problem is to reduce buoyancy effects by using reduced ambient pressure in normal gravity. The objective of this work is to explore the possibility of simulating the effect of gravity, and in turn buoyancy, through changes in ambient pressure, on upward/concurrent flame spread over a thin combustible solid. Comparisons with available data at different gravity levels are used to determine the extent to which low-pressure can be used to replicate flame spread characteristics at different gravities. Experiments of the upward/concurrent flame spread over thin Kimwipe paper sheets were conducted in normal gravity inside a pressure chamber with ambient pressures ranging between 100 and 30 kPa and a forced flow velocity of 10 cm/s. Results show that reductions of pressure slow down the flame spread over the paper surface, and also reduces flame intensity. Comparison with published partial gravity data shows that as the pressure is reduced, the normal gravity flame spread rate approaches that observed at different gravity levels. The data presented is correlated in terms of a mixed convection non-dimensional number that describes the convective heat transferred from the flame to the solid, and that also describes the primary mechanism controlling the spread of the flame. The correlation provides information about the similitudes of the flame spread process in variable pressure, flow velocity and gravity environments, providing guidance for potential ground-based testing for fire safety design in spacecraft.

Spectroscopic investigations on impurities and their effect on the electron number density in the shock tube

An accurate estimation of electron number density is significant in many plasma physics studies. In this paper, the effect of impurities in test gas on the electron number density of the plasma generated in the hypersonic flow of a free-piston driven hypersonic shock tube has been studied using optical emission spectroscopy. Emission spectra of argon plasma showed the presence of following impurities: sodium, potassium, nitrogen, oxygen and hydrogen. The electron number density calculated from the spectral broadening of argon emission lines, is one order of magnitude higher than the electron number density calculated from the thermochemical equilibrium flow model that does not include the impurities. Hence the results show that the presence of impurities has a significant impact on the shock tube plasma and warrants the need to include these effects in the thermochemical equilibrium flow model while investigating magneto-aerodynamic interaction flows and communication blackout studies in the hypersonic ground-based test facilities.

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster.

The goal of this work is to set up an electric propulsion (EP) sputtering test section as a feasibility study for ground-based sputter testing of spacecraft materials with a radio-frequency ion thruster. Such experiments deliver valuable data, which are scarce but highly desired to model EP-based space missions, for example, with the Spacecraft Plasma Interaction System in order to predict the performance and lifetime of spacecraft components. This study assessed if sufficient testing conditions can be met to produce reliable experimental material data in the future. Therefore, the thruster was operated at ion energies of 1.5 and 1.8 keV, and a quartz crystal microbalance (QCM) was installed to detect sputter deposition rates. Molybdenum (Mo) and silver (Ag) were chosen as sputter targets. Wafer substrates served as a passive sampling method to characterize the composition of sputtered material by Rutherford backscattering spectrometry. Additionally, sputtering simulations matching the experimental conditions were performed with the software SDTrimSP. We obtained comparable experimental and computational data, as measured sputter deposition rates lie within the simulated order of magnitude and to some extent show the predicted angular dependence. Analysis of the deposited sputter material revealed the formation of metal oxides, which requires a future adaption of the material specific QCM settings. Furthermore, the cooling system of the QCM sensor head was not sufficient, limiting the comparability of results.

Experimental Study on the Flow Behavior of Grout Used in Horizontal Directional Drilling Borehole Grouting to Seal Mining-Induced Overburden Fractures

The development of water-conducting fractures from underground coal mining is a geological cause of groundwater loss. Sealing mining-induced rock fracture channels through borehole grouting is an effective way to protect groundwater resources. A ground-based engineering test was conducted at the Gaojiabao coal mine that utilized horizontal directional drilling (HDD) to grout and seal water-conducting overburden fractures. This study carried out a theoretical and experimental exploration using HDD to evaluate the development characteristics and grout hydraulic conductivity of these mining-induced fractures. The results showed that, as a result of varying fracture morphologies in different zones of the mining overburden, multiple fracture types were sequentially exposed as the HDD borehole advanced from the original rock mass outside the mining area towards the mining-induced fractured rock mass. The fracture types were exposed in the following order: compressive shear fractures, tensile failure fractures, and bed separation fractures. Moreover, the void characteristics of the exposed fractures in the borehole were significantly different at different drilling horizons, which affected the flow behavior and sealing performance of the injected grout. Lastly, three typical orders in which the different types of fractures were sequentially exposed by the borehole were summarized, and further analysis of the orders led to a scheme for determining drilling horizons favorable for efficient fracture sealing. The results of this study will enable efficient grout sealing of the fractures caused by mining and reduce groundwater loss.

Surface modification of flat cable conductors: a path to withstand the aggressive space environment

A novel ion-beam surface treatment process with simultaneous surface renewal (IB/SSR) providing charge-dissipative properties to the treated surfaces was developed at ITL and successfully used for treatment of both sides of variously shaped and sized flat conductor cables (FCC) that are being used in various applications in aerospace, space and commercial programs. The results of surface resistivity (SR) measurements of the front side of FCC’s used as interconnects in solar panel arrays on satellites in Geostationary (GEO) orbit averaged around 10 MΩ/sq for short FCC units and around 8 MΩ/sq for long units. The SR values for back sides averaged around 18 MΩ/sq for both short and long FCCs. These values remained unchanged during ~ 1 month storage of the treated FCCs at lab conditions, and after a following 2-2.5 year’s storage. Extended long-term ground-based GEO environment simulation testing experiments (15 years space equivalent) that involved simultaneous exposure to all three GEO environmental factors, i.e. protons, electrons, and UV have been performed on two specially selected FCC sets. These sets included pristine and IB/SSR-treated FCCs, with both front and back FCC surfaces being exposed. It was demonstrated that the surface conductivity obtained on the insulating space polymer films is almost insensitive to space radiation during the 15 years in GEO. It was also shown that the long-term influence of GEO radiation on thermal optical characteristics of both FCCs sides does not significantly differ for pristine and ion-beam treated samples.

Algorithm for conducting autonomous tests of radio electronic means

Due to the increasing complexity of radio electronic equipment, the problem of its reliability becomes much more acute. At the same time, the task of evaluating on-board equipment at the design and production stages becomes very urgent. An important issue is also the reliable determination of numerical values of its reliability indicators. Ground-based experimental testing of samples of on-board radio-electronic facilities, devices, assemblies and units facilitates the solution of this problem. Inthe course of this testing, various tests conducted. It been shown that the timeliest information about the quality and reliability of the equipment can be obtained from autonomous tests. In the article, the choice of an autonomous test facility has made. Amicroprocessor-based temperature controller chosen as an autonomous test object. The expert evaluation method used to select the object. Analysis of specifications carried out. The scope of autonomous tests was determined. An algorithm for autonomous testing of on-board radio electronic equipment of spacecraft was developed. It has properties of discreteness, determinacy, limb and mass. The development of the autonomous test algorithm takes more account of the specifics of the technology used to manufacture the product under test and the test sequence. One of the options for mathematical modelling of the process of selecting test equipment for autonomous tests been considered.

Оценка температурного состояния и методические вопросы газодинамических испытаний образцов высокотемпературной керамики

Material selection for aerospace structural and power plant units subjected to thermal stresses is based on thorough investigation of their physical, mechanical and optical properties in a wide range of temperatures up to 2500--3000 K, which are in practice the highest possible. However, it is exceptionally difficult and expensive to obtain the whole extent of data on the properties of structural and refractive materials currently in development that is required to analytically estimate the thermal state and performance of the structures designed to be subjected to thermal stresses. Moreover, the theoretical thermal state models in use are most often based on a number of assumptions, which means that they will need to be validated against experimental investigation data. As a result, integral methods of estimating material performance under intended real-world thermal and force loads become highly important. Ground-based development testing using simulation installations will solve this problem. While testing, it is important to ensure that the simulated thermal modes of the object being tested match its real-world thermal modes. The paper considers these issues regarding estimating refractory ceramics performance subjected to a high-temperature gas flow