Ground Test Program Research Articles

Numerical and experimental verification of an inverse‐direct approach for load and strain monitoring in aeronautical structures

Aeronautical structures are increasingly aging, and the occurrence of unexpected loads could reduce their operability. A health and usage monitoring system would enable the continuous monitoring of the state of health of a structure and track its aging by a load monitoring system, which aims at the real-time reconstruction of the loads acting on a structure. However, sometimes the loads and the induced strain and stress fields are difficult to be reconstructed exactly, as for complex loading due to flight maneuvers. In this work, the full strain and load fields of a structure are reconstructed by an inverse-direct approach, leveraging on the calibration matrix approach. The latter exploits a least-squares minimization of an error functional, defined as the comparison between measured strains in discrete positions and a numerical formulation of the same, to reconstruct an equivalent, however representative, load set. By assuming a linear relationship between strain and load through a calibration matrix, this minimization can be performed analytically, leading to a computationally very efficient algorithm that can be operated online. Once the equivalent load set is computed, the full strain field can be estimated relying on a second calibration matrix linking the external loads to the strain field of the complete structure. The method has been numerically tested with an unmanned aerial vehicle (UAV) subjected to aerodynamic pressure loads simulating flight maneuvers. Finally, the results are experimentally validated during a ground test program on a real UAV, proving the robustness to different experimental uncertainties.

Solar sailing technology challenges

Solar sailing technology has been demonstrated in the space environment over the past decade, in Earth orbit and on an interplanetary trajectory. These technology demonstration missions, along with a forty-year history of conceptual studies and laboratory development, have provided a foundation for a new era of missions where solar sailing provides the necessary propulsion to achieve space science and infrastructure goals. Numerous challenges remain on the path to flagship-class missions utilizing solar sails. This paper provides a survey of the current state of the art in solar sailing technology, including a taxonomy of solar sail design. A summary of solar sailing missions is provided, along with description of the larger-scale ground test programs. A set of representative next-generation solar sailing mission concepts is then presented, to establish driving requirements for future applications. To meet the objectives for these future missions, sail areas must increase by a factor of 50–500 relative to the largest solar sail flown to date. Sail loading, sailcraft areal density, characteristic acceleration and lightness number must improve by one to two orders of magnitude. Technology advancements required to meet the future solar sailing performance needs are described, providing a technology roadmap for solar sailing capability.

Space docking mechanism technology of spacecraft

The space docking technology is one of the key technologies of manned space engineering. This paper discusses the system schemes of the docking mechanism of Shenzhou spacecrafts, and analyzes the dynamics design, mechanisms design, and connection stiffness insurance of docking mechanism during docking capture and buffer. This paper also discusses the ground test system and test program of docking mechanism, and introduces the conditions of the first docking mission.

Supersonic combustion ramjet missile

During the period of 1962-1978, the Applied Physics Laboratory of Johns Hopkins University developed the technology for a family of missiles named SCRAM for use as fleet defense weapons. SCRAM is the acronym for supersonic combustion ramjet missile. The development work began with the conceptual design of two missile configurations and calculations of the expected performance for a variety of missions to provide defense for the surface fleet. A novel class of multimodule fixed-geometry hypersonic inlets was designed and wind-tunnel models were built and tested at Mach numbers of 4-10 at angles of attack up to 15 deg. Injector and combustor development was carried out in direct connect test apparatus. Considerable effort was directed to the development and testing of a wide variety of storable, reactive liquid fuels including boranes and aluminum alkyls. Many new testing techniques and diagnostic instruments were developed that are still key elements of scramjet test operations. The program culminated with the testing of the entire engine in free jets at Mach numbers of 57.3 and the design of a family of revised vehicle configurations that could exploit the full capability of the performance observed in the ground test program. This article presents the highlights of the technology program and references recently released documents.

Power plants

Based on the outstanding results achieved to date in highly successful flight and ground test programs, GE Aircraft Engines (GEAE) will accelerate certification of the first GE90 growth engine to May 1996.

Mobile transporter concept for extravehicular activity assembly of future spacecraft

This paper details the ground test program for the NASA Langley Research Center mobile transporter concept. The mobile transporter would assist extravehicular activity astronauts in the assembly of the Space Station Freedom. One-£ and simulated 0-g (neutral buoyancy) tests were conducted to evaluate the use of the mobile transporter. A three-bay (44 struts) orthogonal tetrahedral truss configuration with a 15-ft square cross section was repeatedly assembled by a single pair of pressure suited test subjects working from the mobile transporter astronaut positioning devices. The average unit assembly time was 28 s/strut. The results of these tests indicate that the use of a mobile transporter for extravehicular activity assembly of a space station size structure is viable and practical. Additionally, the mobile transporter could be used to construct other spacecraft such as the submillimeter astronomical laboratory* space crane, and interplanetary (i.e., Mars and lunar) spacecraft.

Space construction results: The EASE/ACCESS flight experiment

This paper describes NASA ground and flight test activities in the development of in-space construction techniques for the assembly of Space-Station-sized structures. In November 1985, the first experiments on space construction using EVA astronauts were flown aboard the Space Shuttle, with spectacular and highly visible results. The EASE and ACCESS flight experiments are described and the ground and water tank test program and operations in-flight including instrumentation are presented, together with illustrations of assembly and disassembly of both the EASE and ACCESS experiments. The flight test results are presented and learning and productivity curves are discussed, with differences between free EVA vs EVA using foot restraints compared. Two weeks after the flights, the Space Station structural assembly technique was selected to be EVA astronaut assembly of the truss, based on the flight experiment results.

An Experiment to Determine Nose Tip Transition with Fluctuating Pressure Measurements

Theme A accurate assessment of the altitude at which nose tip boundary-layer transition onset occurs is required to design and evaluate the heat protection system of high performance re-entry vehicles. Theoretical approaches to the transition phenomena are lacking, consequently the re-entry vehicle designer has relied almost exclusively on experimental data. Although transition onset has been determined on the frustum of R/V's in both ground and flight test experiments, and nose tip transition has been obtained and detected in ground tests with thermal instrumentation, there is a noticeable lack of transition detection techniques based on pressure measurements for the nose tip region. The purpose of this paper is to present the results of an exploratory ground test program to assess possible flight pressure instrumentation concepts to detect nose tip transition for full scale R/V flight test applications. l Specific ground test objectives were: a) to determine the feasibility of detecting nose tip transition by fluctuating pressure measurements using a miniaturized solid-state pressure transducer, and b) to demonstrate that the solid-state pressure sensor can make both steady-state and fluctuating pressure measurements simultaneously in a wind tunnel test for possible flight test application. Simultaneous fluctuating and steady-state pressure measurements were made and transition could be detected on the nose tip frustum 3.3 nose radii aft of the stagnation point. Transition onset was not detected at more forward stations possibly due to a porous nose.

Development of noise-reduction concepts for 727 and 737 airplanes

A review is given of various noise-reduction concepts pertinent to JT8D-powered 727 and 737 airplanes, with emphasis on acoustic technology. Acoustic treatment for engine fan noise reduction is shown to result in production airplane configurations that comply with existing FAR Part 36 regulations for new airplanes. Two jet noise suppression concepts aimed at further 727 noise reduction are discussed. An ejector/suppressor concept that has been demonstrated in an FAA-sponsored ground and flight test program is shown to achieve 6- to 8-EPNdB suppression of jet noise at takeoff power. Airplane performance penalties, however, have precluded production application of this configuration. The refan concept, currently under development on a NASA contract, involves JT8D engine modifications to incorporate a higher work-extraction fan. This modification realizes lower jet noise that, when coupled with extensive acoustic treatment, results in significant noise reductions with a minimum impact on airplane performance. Subject Classification: 50.40, 50.50, 50.55, 50.75.