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The printed circuit and GaAs beam lead technology-based, low noise integrated receiver presented was developed for low cost space communications and operates in the 59-64 GHz range, using a phase-locked Gunn oscillator at 51.5 GHz. An IF output of 7.5-12.5 GHz is obtained. With the exception of the IF amplifier, and of the E-plane technology-based RF preselect filter, all circuits of the device employ suspended stripline construction.
The design and construction of models for the National Transonic Facility (NTF) has resulted in significant technology developments in many areas. This lecture covers the development of design criteria and major research and development work that has contributed to the successful design and fabrication models for testing at full scale Reynolds number the NTF. Emphasis is placed on the materials aspect of the design and fabrication proces, including metallic materials, mechanical properties characterization, new steel alloy development, fracture toughness enhancement, and identification of fillers and solders suitable for use in cryogenic models. Quantitative data are provided which will be of value to the potential user of NTF or for application to the design and fabrication of model systems for other cryogenic wind tunnels.
The dynamic verification of spacecraft relies heavily on ground-based tests. These tests usually simulate flight environments or validate analytical models used in establishing design loads and in designing control algorithms. They also provide security against failures resulting from unanticipated or unmodeled hardware behavior. Future orbital antennas, space stations, and solar power systems are likely to be of sizes difficult to test using current ground test technology. In addition to size, other factors such as low natural frequencies, lightweight construction, and the presence of many structural joints, cause significant sensitivity of the test process to the earth-gravity environment. Yet, accuracy requirements on the verification process will be more stringent because of modern flexible-structure control approaches. This paper describes some of the problems and discusses research on potential solutions. The importance of an integrated ground test, analysis, and flight test program is emphasized. An ongoing research program of this type focusing on a 60-meter, deployable, truss-beam test article is described.
In 1977, the Protoflight Manipulator Arm (PFMA) was designed and built. It is one of two space qualified manipulators. A new conceptual design for the next generation manipulator of space applications is presented. The next generation manipulator and the PFMA are described in detail. Their differences could have a major influence on the construction, testing, and performance of a space arm. Assessed in detail are these technologies and their effect on the design. Servicing is an important goal of robotics in space. Parameters such as environment, type of task, time sequence, and dexterity will affect the arm and its ability to accomplish its mission. Requirements such as these are important considerations in the design of the next generation space arm.
A brief general overview of NASA programs and planning is presented. Topics discussed include long-term policy goals (creating commercial opportunities, construction of the International Space Station, and manned planetary missions), the scientific and technological projects planned for the Space Station, the key role of the Space Station in solar-system exploration, the pathfinder-technologies concept, and the comprehensive remote-sensing program Mission to Planet Earth.
The objective was to design a remotely piloted vehicle which is capable of gathering in-flight pressure distribution data on a lifting test specimen, and then test the design by constructing a subscale demonstrator, to prove the flight worthiness of the concept. The technology demonstrator was scheduled for takeoff at approximately, 7:20 AM on Thursday April 27th. There was a light wind from the southeast. The plane was hand-launched and made an initial dip, most likely due to the poor trim conditions at launch. It then began to climb and bank into a left turn. The aircraft climbed to an altitude of approximately 150 ft and circled. The plane flew for several minutes and at times appeared to bump around, which was due to thermal activity disrupting the flight of the aircraft. The aircraft was brought slowly down in a power-off condition and glided in for a belly landing and landed without incident. Results of the flight test proved the general capability of the design to maintain flight stability throughout the take off, cruise, turning, and landing flight regimes. We were not able to demonstrate stability with the test specimen in place as the control surfaces designed to counteract the instabilities induced in the static system, winglets and ailerons, were not included.
The evolutionary approach to space development is discussed in the framework of three overall strategies encompassing four case studies. The first strategy, human expeditions, places emphasis on highly visible, near-term manned missions to Mars or to one of the two moons of Mars. These expeditions are similar in scope and objectives to the Apollo program, with infrastructure development only conducted to the degree necessary to support one or two short-duration trips. Two such expeditionary scenarios, one to Phobus and the other to the Mars surface, are discussed. The second strategy involves the construction of science outposts, and emphasizes scientific exploration as well as investigation of technologies and operations needed for permanent habitation. A third strategy, evolutionary expansion, would explore and settle the inner solar system in a series of steps, with continued development of technologies, experience, and infrastructure.
NASA-Lewis is responsible for the development, fabrication, and assembly of the electric power system (EPS) for the Space Station Freedom (SSF). The SSF power system is radically different from previous spacecraft power systems in both the size and complexity of the system. Unlike past spacecraft power system the SSF EPS will grow and be maintained on orbit and must be flexible to meet changing user power needs. The SSF power system is also unique in comparison with terrestrial power systems because it is dominated by power electronic converters which regulate and control the power. Although spacecraft historically have used power converters for regulation they typically involved only a single series regulating element. The SSF EPS involves multiple regulating elements, two or more in series, prior to the load. These unique system features required the construction of a testbed which would allow the development of spacecraft power system technology. A description is provided of the Power Management and Distribution (PMAD) DC Testbed which was assembled to support the design and early evaluation of the SSF EPS. A description of the integration process used in the assembly sequence is also given along with a description of the support facility.
Pattern recognition may supplement or replace certain navigational aids on spacecraft in docking or landing activities. The need to correctly identify terrain features remains critical in preparation of autonomous planetary landing. One technique that may solve this problem is optical correlation. Correlation has been successfully demonstrated under ideal conditions; however, noise significantly affects the ability of the correlator to accurately identify input signals. Optical correlation in the presence of noise must be successfully demonstrated before this technology can be incorporated into system design. An optical correlator is designed and constructed using a modified 2f configuration. Liquid crystal televisions (LCTV) are used as the spatial light modulators (SLM) for both the input and filter devices. The filter LCTV is characterized and an operating curve is developed. Determination of this operating curve is critical for reduction of input noise. Correlation of live input with a programmable filter is demonstrated.
Liquid mirrors provide an exciting means to obtain large optical telescopes for substantially lower costs than conventional technologies. The liquid mirror concept has been demonstrated in the lab with the construction of a diffraction limited 1.5 m mirror. The mirror surface, using liquid mercury, forms a perfect parabolic shape when the mirror cell is rotated at a uniform velocity. A liquid mirror must be able to support a heavy mercury load with minimal flexure and have a fundamental resonant frequency that is as high as possible, to suppress the amplitude of surface waves caused by small vibrations transmitted to the mirror. To minimize the transmission of vibrations to the liquid surface, the entire mirror rests on an air bearing. This necessitates the mirror cell being lightweight, due to the limited load capabilities of the air bearing. The mirror components must also have physical characteristics which minimize the effects of thermal expansion with ambient temperature fluctuations in the observatory. In addition, the 2.7 m mirror construction is designed so that the techniques used may be readily extended to the construction of large mirrors. To attain the goals of a lightweight, rigid mirror, a composite laminant construction was used. The mirror consists of a foam core cut to the desired parabolic shape, with an accuracy of a few mm. An aluminum hub serves as an anchor for the foam and skin, and allows precise centering of the mirror on the air bearing and drive system. Several plys of Kevlar, covered in an epoxy matrix, are then applied to the foam. A final layer of pure epoxy is formed by spin casting. This final layer is parabolic to within a fraction of a mm. An aluminum ring bonded to the circumference of the mirror retains the mercury, and incorporates stainless-steel hard-points for the attachment of balance weights.
This report covers the third 6 month period, from February 28, 1995 to August 31, 1995, under this contract. The main efforts during this period were the construction of the X-ray furnace, evaluation and selection of the CCD technology for the X-ray camera, solidification experiments with Al alloys and Al-zirconia composites in the prototype furnace, evaluation of specimens for the particle pushing flight experiment - PEPSI, measurements of emitted spectra from X-ray source, testing of the high resolution X-ray test targets, and the establishment of criteria for and selection of peripheral equipment. In addition to these tasks, two presentations were prepared in this period; one for the AIAA Microgravity Symposium and another for the Gordon Conference on Gravitational Effects in Pyisico-Chemical Systems.
Three critical compression splice joint locations in a stitched graphite-epoxy transport wing stub box have been analyzed to determine their expected structural performance. The wing box is representative of a section of a commercial transport wing box and was designed and constructed by McDonnell Douglas Aerospace Company as part of the NASA Advanced Composites Technology (ACT) program. The results of the finite element analyses of the splice joints are presented. The analysis results indicate that failure will not occur in the splice joint regions for loads less than the Design Ultimate Load of the wing box.
The results of a series of tests conducted at the NASA Langley Research Center to evaluate the behavior of an all-composite full-scale wing box are presented. The wing stub box is representative of a section of a commercial transport aircraft wing box and was designed and constructed by McDonnell Douglas Aerospace Company as part of the NASA Advanced Composites Technology (ACT) program. Tests were conducted with and without low-speed impact damage and repairs. The structure with nonvisible impact damage carried 140 percent of Design Limit Load prior to failure through an impact site.
The production of bulk glass and fiber glass in space and on the moon and Mars should lead to superior products. Specifically glass plates for windows and optical elements could be produced with theoretical strengths by production in vacuum. Water vapor is known to decrease glass strength by up to two orders of magnitude from theoretical. A low gravity glass plate apparatus prototype has been designed and built which uses centrifugal force to shape the glass and solar energy to melt the glass. Glass fiber could be produced on the moon or Mars from in-situ materials using standard technologies. This material could then be used as reinforcement in composite materials in construction of bases. Also, it has been shown that processing in reduced gravity suppresses crystallization in certain heavy metal fluoride glasses. It is proposed to reprocess optical fiber preforms on the space station and then pull these into optical fiber. It is estimated that the attenuation coefficient should be reduced by two orders of magnitude.
Researchers at NASA Langley Research Center are developing a new electron beam freeform fabrication (EB F(sup 3)) technique to fabricate metal parts. This process introduces metal wire into a molten pool created by a focused electron beam. Potential aerospace applications for this technology include ground-based fabrication of airframe structures and on-orbit construction and repair of space components and structures. Processing windows for reliably producing high quality 2219 aluminum parts using the EB F(sup 3) technique are being defined. The effects of translation speed, wire feed rate, and beam power on the resulting microstructures and mechanical properties are explored. Tensile properties (ultimate tensile strength, yield strength, and elongation) show little effect over the range of processing conditions tested. Basic processing-microstructure-property correlations are drawn for the EB F(sup 3) process.
The emerging class of direct manufacturing processes known as Solid Freeform Fabrication (SFF) employs a focused energy beam and metal feedstock to build structural parts directly from computer aided design (CAD) data. Some variations on existing SFF techniques have potential for application in space for a variety of different missions. This paper will focus on three different applications ranging from near to far term to demonstrate the widespread potential of this technology for space-based applications. One application is the on-orbit construction of large space structures, on the order of tens of meters to a kilometer in size. Such structures are too large to launch intact even in a deployable design; their extreme size necessitates assembly or erection of such structures in space. A low-earth orbiting satellite with a SFF system employing a high-energy beam for high deposition rates could be employed to construct large space structures using feedstock launched from Earth. A second potential application is a small, multifunctional system that could be used by astronauts on long-duration human exploration missions to manufacture spare parts. Supportability of human exploration missions is essential, and a SFF system would provide flexibility in the ability to repair or fabricate any part that may be damaged or broken during the mission. The system envisioned would also have machining and welding capabilities to increase its utility on a mission where mass and volume are extremely limited. A third example of an SFF application in space is a miniaturized automated system for structural health monitoring and repair. If damage is detected using a low power beam scan, the beam power can be increased to perform repairs within the spacecraft or satellite structure without the requirement of human interaction or commands. Due to low gravity environment for all of these applications, wire feedstock is preferred to powder from a containment, handling, and safety standpoint. The energy beams may be either electron beam or laser, and the developments required for either energy source to achieve success in these applications will be discussed.
The electrician pictured is installing a General Electric Ground Fault Interrupter (GFI), a device which provides protection against electrical shock in the home or in industrial facilities. Shocks due to defective wiring in home appliances or other electrical equipment can cause severe burns, even death. As a result, the National Electrical Code now requires GFIs in all new homes constructed. This particular type of GFI employs a sensing element which derives from technology acquired in space projects by SCI Systems, Inc., Huntsville, Alabama, producer of sensors for GE and other manufacturers of GFI equipment. The sensor is based on the company's experience in developing miniaturized circuitry for space telemetry and other spacecraft electrical systems; this experience enabled SCI to package interruptor circuitry in the extremely limited space available and to produce sensory devices at practicable cost. The tiny sensor measures the strength of the electrical current and detects current differentials that indicate a fault in the functioning of an electrical system. The sensing element then triggers a signal to a disconnect mechanism in the GFI, which cuts off the current in the faulty circuit.
The figure depicts the planned Actuated Hybrid Mirror Telescope (AHMT), which is intended to demonstrate a new approach to the design and construction of wide-aperture spaceborne telescopes for astronomy and Earth science. This technology is also appropriate for Earth-based telescopes. The new approach can be broadly summarized as using advanced lightweight mirrors that can be manufactured rapidly at relatively low cost. More specifically, it is planned to use precise replicated metallic nanolaminate mirrors to obtain the required high-quality optical finishes. Lightweight, dimensionally stable silicon carbide (SiC) structures will support the nanolaminate mirrors in the required surface figures. To enable diffraction- limited telescope performance, errors in surface figures will be corrected by use of mirror-shape-control actuators that will be energized, as needed, by a wave-front-sensing and control system. The concepts of nanolaminate materials and mirrors made from nanolaminate materials were discussed in several previous NASA Tech Briefs articles. Nanolaminates constitute a relatively new class of materials that can approach theoretical limits of stiffness and strength. Nanolaminate mirrors are synthesized by magnetron sputter deposition of metallic alloys and/or compounds on optically precise master surfaces to obtain optical-quality reflector surfaces backed by thin shell structures. As an integral part of the deposition process, a layer of gold that will constitute the reflective surface layer is deposited first, eliminating the need for a subsequent and separate reflective-coating process. The crystallographic textures of the nanolaminate will be controlled to optimize the performance of the mirror. The entire deposition process for making a nanolaminate mirror takes less than 100 hours, regardless of the mirror diameter. Each nanolaminate mirror will be bonded to its lightweight SiC supporting structure. The lightweight nanolaminate mirrors and SiC supporting structures will be fabricated from reusable master molds. The mirror-shape-control actuators will be low-power, high-capacitance lead magnesium niobate electrostrictive actuators that will be embedded in the SiC structures. The mode of operation of these actuators will be such that once power was applied, they will change in length and once power was removed, they will maintain dimensional stability to nanometer precision. This mode of operation will enable the use of low-power, minimally complex electronic control circuitry. The wave-front-sensing and control system will be designed and built according to a two-stage architecture. The first stage will be implemented by a Shack- Hartmann (SH) sensor subsystem, which will provide a large capture range. The second, higher-performance stage will be implemented by an image-based wave-front-sensing subsystem that will include a phase-retrieval camera (PRC), and will utilize phase retrieval and other techniques to measure wavefront error directly. Phase retrieval is a process in which multiple images of an unresolved object are iterated to estimate the phase of the optical system that acquired the images. The combination of SH and phase-retrieval sensors will afford the virtues of both a dynamic range of 105 and an accuracy of <10 nm.