Ground Test Facilities Research Articles

Active fault-tolerant control with prescribed performance and reachability judgement for the altitude ground test facility

This research proposes an active fault-tolerant control (AFTC) method based on reachability judgement with asymmetric appointed-time prescribed performance to ensure the safety of altitude ground test facility (AGTF) under potential valve actuator and sensor faults. Firstly, a long short-term memory (LSTM) neural network is employed for fault diagnosis. Given the unique characteristics of AGTF, the equivalent multiplicative fault is introduced to ensure the successful fitting of the fault diagnosis network. Then, a reachability judgement network based on the distance field on grids (DFOG) method is designed to assess the impact of faults on subsequent tasks of the system, thereby ensuring the safety of the AGTF. Subsequently, this study proposes an error transformation function of prescribed performance control (PPC) that ensures error convergence even in cases of asymmetric performance function. This enables the performance boundaries to be further reduced to improve the control performance of the system. Finally, experiments validate the effectiveness of the methods proposed in this manuscript.

Unsteady conjugate heat transfer simulation around the throat insert in a high enthalpy shock tunnel

High enthalpy shock tunnel is a critical ground testing facility for evaluating the aerodynamic performance of hypersonic vehicles by simulating high-enthalpy, hypersonic flows. However, as the total temperature or pressure of the stagnant gas rises, the throat insert may be subjected to melting or oxidation, leading to a degradation in flow quality or a reduction in effective test time. This study investigates the unsteady heat transfer between the gas flow and the throat insert using a conjugate heat transfer model. The effects of test time, total temperature, and total pressure on the throat temperature are presented. An increase in any of these factors will raise the throat temperature. Moreover, oxidation will cause the copper throat insert to melt more quickly under the same conditions, which should be considered when addressing throat melting issues.

Advancements on the use of Filtered Rayleigh Scattering (FRS) with Machine learning methods for flow distortion in Aero-Engine intakes

In-flight measurements of aerodynamic quantities are a requirement to ensure the correct scaling of Reynolds and Mach number and for the airworthiness certification of an aircraft. The ability to obtain such measurement is subject to several challenges such as instrument installation, environment, type of measurand, and spatial and temporal resolution. Given expected, more frequent use of embedded propulsion systems in the near future, the measurement technology needs to adapt for the characterization of multi-type flow distortion in complex flow, to assess the operability of air-breathing propulsion systems. To meet this increasing demand for high-fidelity experimental data, the Filtered Rayleigh Scattering (FRS) method is identified as a promising technology, as it can provide measurements of pressure, temperature and 3D velocities simultaneously, across a full Aerodynamic Interface Plane (AIP). Τhis work demonstrates the application of a novel FRS instrument, to assess the flow distortion in an S-duct diffuser, in a ground testing facility. A comparison of FRS results with Stereo-Particle Image Velocimetry (S-PIV) measurements reveals good agreement of the out of plane velocities, within 3.3% at the AIP. Furthermore, the introduction of machine learning methods significantly accelerates the processing of the FRS data by up to 200 times, offering a substantial prospect towards real time data analysis. This study demonstrates the further development of the FRS technique, with the ultimate goal of inlet flow distortion measurements for in-flight environments.

Mixing efficiency optimization of Tesla-type flow channel for total temperature simulation device

The space vehicle total temperature simulation device introduces the actual gas total temperature signal into the vehicle development process. It enables the simulation of flight environments, reduces development time, and decreases overall costs. The uniform and stable temperature signal is paramount in accurately simulate the vehicle's real flight speed and altitude. However, the existing ground test facilities for space vehicles, characterized by their large scale, face significant challenges including insufficient uniformity in gas mixing and inadequate simulation accuracy. The Tesla-type flow channel (TFC) is widely applied for its excellent mixing capabilities in gas and liquid mixing across various domains. In this paper, from the working principle of the total temperature simulation device of space vehicle, according to the characteristics of TFC, a high mixing efficiency optimization design method of TFC is proposed by using RBF neural network response surface and NSGA-II algorithm. The optimized TFC is implemented in the mixing chamber of the total temperature simulation device to enhance the mixing efficiency. This improvement ultimately leads to enhanced accuracy in simulating the flight environment of space vehicles during semi-physical simulations. By utilizing the Pareto optimal solution, the optimal pressure drop is 985.50 Pa, while the standard deviation of temperature is 39.37 K. The results demonstrate a significant improvement in mixing efficiency within the total temperature simulation device due to the introduction of the TFC. This study serves as a valuable reference for enhancing the mixing performance of the total temperature simulation device for space vehicles, while also addressing the need for total temperature simulation in smaller laboratory environments.

A practical parameter tuning algorithm for super-twisting algorithm-based differentiator and its application in altitude ground test facility

The super-twisting algorithm (STA)-based robust exact differentiator (RED) proposed by Levant has been widely applied in control, observation, and fault detection. With properly set parameters, STA-RED is able to estimate exactly and robustly the derivatives of an input. With a given input signal, however, a practical parameter tuning rule still lacks. To this end, a general parameter tuning algorithm with the full stability proof for STA-RED is proposed. In particular, the time linear transformation and the coordinate transformation are performed on a given base signal, allowing the deterministic relationship between the parameters of STA-RED and the amplitude and the frequency of the input to be obtained. The full stability of the STA-RED based on the proposed parameter tunning algorithm (denoted as PSTA-RED) with perturbations is given using the Lyapunov function method. The simulations are carried out using given input signals and the pressure signals from the altitude ground test facility to illustrate the effectiveness of the proposed PSTA-RED.

A review of the impact of ground test-related facility effects on gridded ion thruster operation and performance

A key consideration in the interpretation of ground test data of electric propulsion devices purposed for spaceflight is understanding how facility-effects influence thruster operation. This understanding is critical to the prediction of actual thruster performance in space. The necessity of science-based predictions gleaned from ground tests are particularly critical at higher thruster power levels. Operation of engines at higher power levels in vacuum chambers leads to considerable elevation in background pressure, background plasma density, and backsputter rates. This review examines the influence of ground test facility effects on gridded ion thruster operation. Ground test operation is compared with flight data, where available, to obtain a clear picture of operational differences. Mitigation strategies to alleviate facility effects are also commented upon.

Multiline molecular tagging velocimetry of nitric oxide at 100 kHz using an injection-seeded burst-mode OPO.

An injection-seeded, burst-mode optical parametric oscillator (OPO) operating at a repetition rate of 100 kHz is used to demonstrate the multiline molecular tagging velocimetry of an underexpanded jet using nitric oxide fluorescence. The very narrow linewidth of the OPO system, along with the relatively high pulse energies of the burst-mode system, enables efficient single-photon excitation of nitric oxide along multiple laser beam lines at a high repetition rate. Simultaneous one-dimensional velocity profile measurements were obtained of an underexpanded jet system at six different locations using a reference initial image and single-shot delayed images. A methodology for calculating the uncertainty of single-shot velocity is also described. Mean and root-mean-square velocity profiles are obtained at multiple locations simultaneously over a sampling time of 1 ms. The high-repetition-rate velocity measurements also appear to capture the onset of velocity oscillations and has the potential to reveal velocity frequency content occurring in the tens of kHz. The demonstrated velocimetry technique could be paired with other emerging burst-mode laser capabilities for a quantitative multiparameter gas property or multicomponent gas velocity measurements for supersonic and hypersonic flows, especially within ground test facilities that are limited to very short run durations.

Temperature-pressure interaction analysis of altitude ground test facility’s air intake system in negative temperature simulation

Temperature-pressure interaction analysis of altitude ground test facility’s air intake system in negative temperature simulation

A changeable boundary prescribed performance control for the altitude ground test facility

A changeable boundary prescribed performance control for the altitude ground test facility

Solid Rocket Boosters Separation System Development for the ILR-33 Amber 2K Rocket

Abstract The paper presents the development process of the solid rocket boosters (SRBs) separation system of the ILR-33 AMBER 2K rocket. A redesign of the system was required due to the development of new, larger SRBs. The main system requirements were transmission of forces and moments between the SRBs and the main stage, execution of the separation process at a given moment in flight and mechanical integration simplification. A set of aerodynamics calculations were performed. With the use of computational fluid dynamics software, forces acting on the booster during separation for several angles of attack, as well as the critical booster deflection angle, have been determined. Next, a mathematical model was created to define the load spectrum acting on the system during the flight and separation phases, covering both static and dynamic loads. All the internal and external force sources were considered. A series of motion dynamics simulations were conducted for representative flight cases. Then, the system operational parameters were verified with the use of dedicated ground test facilities. Necessary calibrations of the mathematical model were then implemented, leading to a high level of confidence with the empirical data obtained, thereby leading to a successful system qualification for the flight campaign.

Numerical simulation of an iron meteoroid entering into Earth’s atmosphere using DSMC and a radiation solver with comparison to ground testing data

Observation missions of meteoroids entering the Earth’s atmosphere are conducted regularly. Meanwhile a method to replicate the flight in a ground test facilities has been established. However, numerical simulations with subsequent comparison of the spectroscopic data, on the other hand, are not yet widely used in this field. This is mainly due to the complex flow environment, which includes not only non-equilibrium radiation, but also the outgassing of species from the meteoroid that do not enter the shock since they have only the thermal velocity of the wall without macroscopic flow and therefore cannot heat up as much as the other species. This paper presents a numerical approach to replicate experimental measurements. The Direct Simulation Monte Carlo (DSMC) method is used and bi-directionally coupled with a radiation solver to simulate the atmospheric entry in 80km of an iron meteorite with a diameter of 38mm. The paper provides information and references on the numerical models used, the challenges encountered, and the simulation results. The study shows that the simulation models are well-suited to handle the non-equilibrium effects of meteorite entry and show good agreement with the experimental measurements.

Structural development of the high-speed free jet test facility

The 2 m×2 m high-speed free jet test facility is a 2 m level intermittent blowdown-ejector ground test facility, which has the ability of tri-sonic operation. The closed test section is replaced with a large test chamber. In the development process of the project, the main focus is the uncertainty influences of the jet pressure pulsation action on the facility, the functional realization of step change test Ma number by adjusting semi-flexible nozzle profile in a wide operating range for 2 m level facility, etc. These difficulties have been solved in various ways, such as theoretical analysis and calculation, adoption of multidisciplinary optimization techniques, a reasonable choice of vibration suppression means, and accumulation of rich experience in the field of wind tunnel design. At present, this facility has been built and debugged, and the integrity of the structure has been verified.

Intake pressure control based on improved super-twisting for altitude ground test facilities

This paper focuses on the problem of rapid tracking of engine transient pressure, an improved super twisting algorithm (STA) is adopted to control the intake pressure of the engine. The high altitude platform is analyzed systematically, the mathematical model is derived, and the system and control object model are established. It is improved on the basis of classical STA method and has better control effect than PID control methods and LADRC. Transient state tests of the engine under three different working conditions(acceleration/deceleration state of pushing/pulling accelerator lever, engine intake pressure changing from 50kPa to 60kPa, and engine intake pressure changing from 60kPa to 70kPa) are simulated and verified. The simulation results show that, compared with the traditional PID and active disturbance rejection control(LADRC)strategies, the method proposed in this paper can track the inlet pressure of the engine in transition state quickly, and can reach and stabilize the given set value accurately and quickly.

Novel design of variable Mach number nozzle operated by a single jack

The increasing demand for the wide-range aircraft technique requires the ground test facilities with continuous variation of the Mach number. Owing to the rigorous aerodynamic foundation and simple operation, the single-jack flexible nozzle is widely used. However, there are still some problems in the original single-jack flexible nozzle, such as low Mach number and insufficient flow uniformity. This paper presents a novel design of the single-jack flexible nozzle with high flow uniformity and continuous variable Mach number, adopting flow field inverse design and elasticity inverse design. The new nozzle adopts a three-order transonic asymptotic solution and a B-spline axial velocity distribution, designed by the method of characteristics. By comparing with the original nozzle, the new nozzle no longer requires the conical flow assumption, and the flow fields are more uniform. Another improvement is the continuous contour curvature to ensure the coincidence of the aerodynamic profile and the elastic profile, avoiding the negative Mach waves generated by the curvature discontinuity. In addition, the new nozzle has the advantage of two Mach number design points. Similar to the squeeze theorem, the flow fields are uniform at the non-design points between two design points. The numerical results show that the new nozzle eliminates the Mach waves at different Mach number cases. Within the design range of Mach 2.0–4.0, the flow angle's maximum deviations do not exceed 0.2°, and the average deviations do not exceed 0.1°, meeting the national standard of 0.3°. The Mach number's maximum deviations are around 0.5% of Ma¯, the average deviations are less than 0.2% of Ma¯, and the standard deviations meet the national advanced standard. Even at Mach 1.5 and Mach 4.5 outside the design range, the new nozzle still performs well. The evaluation results validate the feasibility of the novel design, supporting the future construction of the variable Mach number facility.

Development of a Novel Ground Test Facility for Aircraft Environmental Control System

Abstract In this article, the development and experimental investigation of a Boeing 737 aircraft environmental control system (ECS) passenger air conditioner (PACK) has been reported. The PACK is the heart of the ECS that conditions bleed air prior to supplying it to the cabin and avionics bay. Its capability to mask fault occurrences has resulted in increased unscheduled maintenance of the system. As such it has been a key research topic to understand PACK performance characteristics in order to support an accurate diagnostic solution. This article is a continuation of the authors’ work on the development of a systematically derived PACK simulation model and reports the overall development and qualification of a novel in situ ground test facility (GTF) for the experimental investigation of a B737-400 aircraft PACK under various operating modes, including the effect of trim air system. The developed GTF enables the acquisition of the temperature, pressure, and mass flow data throughout the PACK. The overall process of instrumentation selection, installation, sensor uncertainty, and testing in terms of data repeatability and consistency has been reported. The acquired data are then employed to conduct verification and validation of the SESAC (simscape ECS simulation under all conditions) simulation framework. The reported research work therefore enables the advancement in the level of scientific understanding corresponding to the ECS PACK operation under real operating conditions, and therefore supports the development of a robust simulation framework for ECS fault diagnostics at the system level.

Design and characterization of the Sandia free-piston reflected shock tunnel

A new reflected shock tunnel capable of generating hypersonic environments at realistic flight enthalpies has been commissioned at Sandia. The tunnel uses an existing free-piston driver and shock tube coupled to a conical nozzle to accelerate the flow to approximately Mach 9. The facility design process is outlined and compared to other ground test facilities. A representative flight-enthalpy condition is designed using an in-house state-to-state solver and piston dynamics model and evaluated using quasi-1D modeling with the University of Queensland L1d code. This condition is demonstrated using canonical models and a calibration rake. A 25-cm core flow with 4.6-MJ/kg total enthalpy is achieved over an approximately 1-ms test time. The condition was refined using analysis and a heavier piston, leading to an increase in test time. A novel high-speed molecular tagging velocimetry method is applied using in situ nitric oxide to measure the freestream velocity of approximately 3016 m/s. Companion simulation data show good agreement in exit velocity, pitot pressure, and core flow size.

Modeling, analysis and validation of the structural response of a large-scale composite wing by ground testing

This article presents a methodology for the detailed sizing of a composite materials aircraft wing subject to wind tunnel testing design requirements. Aiming at the comparison among the numerical and experimental models in terms of structural response, a ground testing campaign has also been conducted. The present wing, designed and manufactured within the scope of the GRETEL project, consists of several internal, external and interface components, since provision is being made for a wind tunnel test campaign. The Finite Element Method (FEM) modeling technique for all the relevant parts of the wing is initially provided, taking into account the boundary conditions as well as the externally applied aerodynamic loads. The sizing methodology and subsequent compliance of the relevant parts and their connectivity elements with respect to design requirements is also explored in detailed fashion. Certain manufacturing requirements and aspects are also manifested and discussed. Following an introduction on the ground testing facilities and measuring equipment, the results of the static tests and the Ground Vibration Testing (GVT) are compared with the corresponding numerical values. Overall, the numerical and experimental results, in terms of displacements, natural frequencies and eigenmodes are in close agreement.

Ground Testing Facility for Hypersonic Materials

A plasma wind tunnel capable of creating high enthalpy flow conditions is required to overcome the critical performance challenges when developing thermal protection systems

Orbital hopping maneuvers with Astrobee on-board the International Space Station

Interest in space robotic free-flyers for orbital tasks such as fabrication, observation, and on-obit servicing has led to research with Astrobee, a cuboid free-flying spacecraft-manipulator system on-board the International Space Station (ISS). Astrobee is equipped with a three degree-of-freedom robotic arm composed of a two-revolute-joint, two-link perching arm, with a three-finger gripper end effector. Astrobatics is a campaign of experiments designed to explore the use of Astrobee’s robotic arm for orbital self-toss hopping maneuvers. This paper provides an overview of the Astrobee vehicle, followed by a description of the Astrobatics experiments in ground test facilities and on the ISS. Equations of motion for robotic self-toss maneuvers are developed. The results from the first Astrobatics experimental session are then compared against simulation, and the results from the second Astrobatics experimental session are provided, with a discussion of experimental observations and limitations, and followed by a description of future Astrobatics research.

Absolute Measurements of Air Shock-Layer Radiation in the T6 Aluminium Shock Tube

This paper presents the first experimental measurements of shock-layer radiation from a new high-enthalpy ground-test facility: the T6 Aluminium Shock Tube mode. A dual-channel imaging emission spectroscopy system was used to record spatially and spectrally resolved, absolute radiation data from air shock layers at velocities ranging from 7 to . The presented conditions are designed to provide overlap with other experimental datasets in the literature, from both the NASA Electric Arc Shock Tube and an atmospheric plasma torch. Comparisons with these data (as well as computational tools) was favorable, thereby benchmarking the data from the new shock tube against established sources. The measurements made in this paper also confirm that T6 is now the first European facility capable of performing such superorbital shock-layer radiation studies, thereby providing a new capability to support current and future missions in the solar system.