Ground Test Environment Research Articles

An Analysis of Time-delay for Remote Piloted Vehicle

Time-delay is one key factor affecting handling qualities of remote piloted vehicle. In this paper, the composition elements of time-delay were analyzed, in order to determine the relationship between latency and handling qualities. Then, comparing with the definition of time-delay in manned aircraft operation, the expression of time-delay was proposed for remote piloted vehicle and the measuring method of time-delay in piloted airplane was used as a reference. Moreover, considering different types of time-delay in RPV operation, typical open-loop and closed-loop experiments were designed and conducted based on ground testing environment. According to these results, the relation between time-delay and handling qualities was obtained. Finally, validity of this relationship was demonstrated through simulated approach and landing during flight testing. Time-delay is a critical element of RPV handling qualities, the research of which will be helpful and meaningful in unmanned aerial vehicle design and flight testing.

Analysis of radiation induced effects in high-density commercial memories on-board Alsat-1: The impact of extreme solar particle events

This paper presents a long-term study on radiation effects in non-hardened high density memory devices operating within the main on-board computer system of the Algerian microsatellite Alsat-1 in Low Earth Orbit (LEO). A statistical analysis of single-event upset (SEU) activity is presented for commercial SRAM devices, and their response to extreme solar events shows SEU rate significant increases correlated with high-energy protons (E>100MeV). Ground based neutron monitor data are used to illustrate the long-term correlation between galactic cosmic rays and Alsat-1 upsets. The short-term effects of energetic solar particles are illustrated with space environment data from GOES-11. The Alsat-1 observed SEU rates are compared to the predicted rates based on ground test data and environment models. The prediction results are in good agreement with in-flight data.

Establishment of the Ground Testing Environment for Verification and Integration of Micro-satellite

Establishment of the Ground Testing Environment for Verification and Integration of Micro-satellite

Ablation, Thermal Response, and Chemistry Program for Analysis of Thermal Protection Systems

In previous work, the authors documented the Multicomponent Ablation Thermochemistry (MAT) and the Fully Implicit Ablation and Thermal response (FIAT) programs. In this work, key features from MAT and FIAT were combined to create the new Fully Implicit Ablation, Thermal response, and Chemistry (FIATC) program. FIATC is fully compatible with FIAT (version 2.6) but has expanded capabilities to compute the multispecies surface chemistry and ablation rate as part of the surface energy balance. This new methodology eliminates B' tables, provides blown species as a function of time, and enables calculations that would otherwise be impractical (tables with 4 or more independent variables) or impossible (such as stacked pyrolyzing ablators). Equations and solution procedures are presented, then representative calculations of equilibrium and non-equilibrium ablation in flight and ground-test environments are discussed. Nomenclature

Design and Optimize the Supporting Structure of Large-Diameter Lightweight Mirror

This paper describe design and optimize of the lightweight primary mirror assemblies for the space telescope, aim at supporting structure of the primary mirror with an aperture of 530mm for the Cassegrain optical. We design three kinds of flexible support structure for the mirror, and numerical simulation analysis the accuracy of reflective shape for mirror assemblies on the ground test and in-orbit work environment, compare the results of analysis and optimize parameters of flexible structure, determine the final project and put it into production. The results show that the component should be aligned and tested in the same direction of the mirror optical axis and the gravity, the accuracy of reflective shape is PV<λ/25 and RMS<λ /125 (λ = 632.8nm), under the state ofΔ4oC temperature change, the RMS<λ/234 (λ = 632.8nm), the project meet design requirements of the optical system.

저궤도 관측위성 GPS 수신기 궤도상 성능 분석

본 논문은 저궤도 관측위성에 탑재된 GPS 수신기의 궤도상의 성능과 지상 시험 결과를 비교 분석하였다. 지상 시험 환경을 구축하여 다양한 환경에서 시험을 수행하였으며 2006년 발사 이후 6년째 운영 중인 GPS 수신기의 궤도상의 데이터 분석도 수행하였다. 궤도상의 데이터는 초기 운영, 1차 임무 완료 시점 및 최근 결과를 선택하여 정리하였다. 위치 및 시각 동기 정밀도에 대하여 지상 시험과 궤도상의 성능이 일치하여 지상 시험의 유효성을 확인하였다. 본 논문에서 제시한 시험 환경 및 분석 방법은 향후 위성용 GPS 수신기 개발 및 검증에 도움이 될 것으로 예상한다. This paper presents a performance analysis of the GPS(Global Positioning System) receiver on board in LEO satellites, based on the comparison of its in-orbit performances and corresponding ground test results. An extensive ground tests on the subject GPS receiver has been performed in diverse conditions under the right frame of ground test environments and the analysis of in-orbit performances has also been performed with the huge amount of accumulated GPS data which has been in operation for 6 years since its launch on 2006. For this analysis, we chose three sets of in-orbit data; the data during the early mission period, the data at the 3-year mission completion time, and the most recent in-orbit data. As the performance measures, we selected the position and time synchronization accuracy, and the comparative analysis shows the concurrency between the in-orbit performances and the ground test results with in these performance measures, verifying the validity of the ground test. It is expected that the test configuration and analysis method presented in this paper can be applied to developing and verifying the future Koreanized satellite GPS receivers.

A Flight Simulation Vision for Aeropropulsion Altitude Ground Test Facilities

Testing of a gas turbine engine for aircraft propulsion applications may be conducted in the actual aircraft or in a ground-test environment. Ground test facilities simulate flight conditions by providing airflow at pressures and temperatures experienced during flight. Flight-testing of the full aircraft system provides the best means of obtaining the exact environment that the propulsion system must operate in but must deal with limitations in the amount and type of instrumentation that can be put on-board the aircraft. Due to this limitation, engine performance may not be fully characterized. On the other hand, ground-test simulation provides the ability to enhance the instrumentation set such that engine performance can be fully quantified. However, the current ground-test methodology only simulates the flight environment thus placing limitations on obtaining system performance in the real environment. Generally, a combination of ground and flight tests is necessary to quantify the propulsion system performance over the entire envelop of aircraft operation. To alleviate some of the dependence on flight-testing to obtain engine performance during maneuvers or transients that are not currently done during ground testing, a planned enhancement to ground-test facilities was investigated and reported in this paper that will allow certain categories of flight maneuvers to be conducted. Ground-test facility performance is simulated via a numerical model that duplicates the current facility capabilities and with proper modifications represents planned improvements that allow certain aircraft maneuvers. The vision presented in this paper includes using an aircraft simulator that uses pilot inputs to maneuver the aircraft engine. The aircraft simulator then drives the facility to provide the correct engine environmental conditions represented by the flight maneuver.

A Systems Approach to Solder Joint Fatigue in Spacecraft Electronic Packaging

Differential expansion induced fatigue resulting from temperature cycling is a leading cause of solder joint failures in spacecraft. Achieving high reliability flight hardware requires that each element of the fatigue issue be addressed carefully. This includes defining the complete thermal-cycle environment to be experienced by the hardware, developing electronic packaging concepts that are consistent with the defined environments, and validating the completed designs with a thorough qualification and acceptance test program. This paper describes a useful systems approach to solder fatigue based principally on the fundamental log-strain versus log-cycles-to-failure behavior of fatigue. This fundamental behavior has been useful to integrate diverse ground test and flight operational thermal-cycle environments into a unified electronics design approach. Each element of the approach reflects both the mechanism physics that control solder fatigue, as well as the practical realities of the hardware build, test, delivery, and application cycle.

On-Orbit Evaluation of the Control System/Structural Mode Interactions on OSO-8

The Orbiting Solar Observatory-8 experienced severe structural mode/control loop interaction problems during the spacecraft development. Extensive analytical studies, using the hybrid coordinate modeling approach, and comprehensive ground testing were carried out in order to achieve the system's precision pointing performance requirements. A recent series of flight tests were conducted with the spacecraft in which a wide bandwidth, high resolution telemetry system was utilized to evaluate the on-orbit flexible dynamics characteristics of the vehicle along with the control system performance. This paper describes the results of these tests, reviewing the basic design problem, analytical approach taken, ground test philosophy, and on-orbit testing. Data from the tests was used to determine the primary mode frequency, damping, and servo coupling dynamics for the on-orbit condition. Additionally, the test results have verified analytically predicted differences between the on-orbit and ground test environments. The test results have led to a validation of both the analytical modeling and servo design techniques used during the development of the control system, and also verified the approach taken to vehicle and servo ground testing.

Graphite Sublimation Chemistry Nonequilibrium Effects

The implications of the assumption of local solid-gas phase equilibrium for subliming carbon species for graphite ablation calculations in an air environment is investigated. The equilibrium assumption is eliminated by considering the Knudsen-Langmuir equation at the interface for each carbon species. Calculated equilibrium and nonequilibrium results are compared for a very wide range of flight and ground-test environments. The nonequilibrium mass addition parameter is always less than the equilibrium value, and the nonequilibrium wall temperature is always larger for a given environment. Calculations made to determine the convective heat flux required to reach an incipient melt temperature of 3800 K indicate that the required flux determined from an equilibrium calculation can be too high by as much as 200-300% for stagnation enthalpies less than 5000 Btu/lb. Calculations for superorbital re-entry conditions show large differences in the mass addition parameter B' when the convective heating rate is low and the external radiation heating level is relatively high. Similar large differences in R' could be simulated in an existing ground-test facility if the reported external radiation heating level could be increased. Such an experiment would provide data to test the validity of present convectiveheating-rate blowing correlations in a combined heating environment.

Mechanical erosion of charring ablators in ground-test and re-entry environments.

The use of charring ablators as thermal-protection materials for advanced ballistic re-entry is partially limited by the problem of char-layer structural integrity. The dynamic thermal/structural response of carbon/phenolic is analyzed for a high-performance ballistic-reentry environment and for hyperthermal ground-test simulation of this environment. Normal pyrolysis-gas pressure stress along with radial and tangential thermal stresses are predicted based on thermal response of the char layer, pyrolysis zone, virgin sublayer, and a metallic substructure. An in-depth char failure mode is postulated and repetitive char spallation calculated for exposure to a high-pressure ground-test environment. This mechanical recession, added to surface chemical consumption, substantially agrees with measured surface erosion of carbon/phenolic cylinders in the ground tests. Analysis of elastic/plastic thermal stresses in a carbon/phenolic heatshield during atmospheric re-entry shows high tangential char stresses and accompanying high-frequency char spallation before, at, and after peak heating. In this example, mechanical erosion accounted for two-thirds of the total re-entry surface recession.