Search NASA⌕ Search

SEARCH · Search NASA

Results for “deployable reflectors”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Geometric modeling of large space antenna deployment

A dynamic visualization of large antenna deployment was created to be used as a precursor to further analysis of the structure as it is being deployed. The configuration chosen for this investigation was a box-truss structure consisting of a large reflector 60 meters wide by 120 meters long with a 120-meter mast. The entire space structure is folded and compressed into a container 17.8 meters long by 3.75 meters in diameter for transportation to orbit by the Space Transportation System (STS). A geometric model of this structure was created using an interactive solid modeling package. The building blocks of the structure are boxes and cylinders which are put together to form elements connected by joints and hinges. The elements, joints, and hinges make up the box-truss structure. The geometric model was then passed to the MOVIE.BYU software package. The "utility" module of this program was used to manipulate the elements of the structure to represent 13 different stages of deployment. The "animate" command was then used to create a smooth sequence between stages. Each step in the sequence was recorded on magnetic tape and a short movie was produced.

Nazemetz, J.↗
NASA NTRS1981

Hoop/column antenna technology development summary

The Langley Research program for development of hoop/column antenna technology was redirected and includes the fabrication and test of models such as the 4 gore segment of a 50 meter antenna and the 15 meter diameter fully deployable antenna. Significant results were obtained in the point design that includes a quad aperture reflector system for multiple beam applications.

Campbell, T. G.↗
NASA NTRS2011

A Deployable 4 Meter 180 to 680 GHz Antenna for the Scanning Microwave Limb Sounder

The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 680 GHz. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. These provide better horizontal and temporal resolution and coverage than were possible with elevation-only scanning at typical Low-Earth orbit spacing in the two previous MLS satellite instruments. Development of the SMLS antenna was the focus of a 2006 Small Business Innovative Research (SBIR) program whose phase II culminated in the fabrication and thermal stability testing of a composite demonstration model of the SMLS primary reflector. This reflector has the full 4m height and 1/3 the width planned for flight. An Instrument Incubator Program (IIP) titled "A deployable 4 Meter 180 to 680 GHz antenna for the Scanning Microwave Limb Sounder" continues development of the SMLS antenna with the study of 5 topics: 1) detailed mathematical modeling of the antenna patterns from which we simulate geophysical parameter retrievals in order to establish FOV performance requirements; 2) thorough correlation of finite element model predictions with measurements made on the SBIR reflector. We will again measure deformations of this reflector, under more flight-like thermal gradients, using higher precision metrology techniques available in a new large-aperture facility at JPL; 3) fabrication of a full-width primary reflector whose asbuilt surface figure will better meet the figure requirements of SMLS than did the SBIR reflector; 4) integration of the primary with other reflectors, and with residual front ends built in a 2007 IIP, in a breadboard antenna; and finally 5) RF testing of the breadboard on a Near Field Range at JPL. We report on significant progress in 3 areas of the current IIP: development of the mathematical model to predict SMLS antenna patterns and their application in a preliminary set of geophysical retrievals; the correlation between surface deformation predicted by finite element models and measurement in the 2009 isothermal stability tests of the SBIR, with implications for the thermal gradient testing to be performed at JPL; and aspects of the conceptual design of the full-width primary reflector to be fabricated and tested in the 2nd and 3rd years of the IIP.

heterodyne radiometer↗
NASA NTRS2006

Radiation Characteristics of Reflectarray Antennas: Methodology and Applications to Dual Configurations

Reflectarrays combines key features of large reflectors and phased array elements to generate a collimated beam as required in high gain antennas. In reflectarrays, a large flat reflecting surface with many resonant patch elements is illuminated by a feed (or by a feed/subreflector in dual reflector configuration). In many space applications, reflectarrays applications can be advantageous because their large surface can be folded or rolled as a part of spacecraft payload before being deployed. Consequently, a reflectarray can significantly reduce both volume and mass requirements in space deployment. To optimize reflectarray antenna performance, a phase correction mechanism must be applied to its individual array elements some of which are well documented in the literatures. In this study, we attempt to extend analytical techniques in reflector analysis to reflectarrays by introducing a number of approaches to estimate the reflectarray antenna performance independent of its phase compensation mechanism. In one approach, a Physical Optics (PO) current will be assigned to the surface of individual reflectarray elements upon which a phase correction will be applied. In the second approach, a transmit/receive (TX/RX) radiation characteristics will be assigned to individual reflectarray elements from which coupling coefficients will be calculated and assigned as the excitation coefficient of individual elements. PO approach is modeled in the UCLA reflector code while coupling (TX/RX) method is implemented in both UCLA code as well as TICRA (GRASP) software. Results are presented for single and dual configurations with the main reflector as a reflectarray. The approach described is used to design a 3-m Cassegrain offset-fed configuration for dual X/Ka-bands application.

reflectors↗
NASA NTRS1984

Two-Stage Off-Axis Cylindrical Solar Concentrator

Concentrator uses off-axis geometry to achieve efficient uniform illumination of photovoltaic cells. Primary reflector is parabolic cylinder and therefore readily adaptable to rolling up for transport and unrolling for deployment. Foldable cylindrical structure has potiential for both terrestrial and space applications.

Winston, R.↗
NASA NTRS2006

Lightweight, Segmented, Mostly Silicon Telescope Mirror

A document presents the concept of a curved telescope primary reflector structure, made mostly of silicon, that would have an areal mass density 1 kg/m2 and would be deployed in outer space, where it would be operated at a temperature in the cryogenic range. The concept provides for adjustment of the shape of the mirror to maintain the required precise optical surface figure despite the flexibility inherent in the ultra-lightweight design. The structure would include a thin mirror layer divided into hexagonal segments supported by flexure hinges on a lightweight two-layer backing structure. Each segment would also be supported at three points by sets of piezoelectric linear microactuators that could impose small displacements along the optical axis. The excitations applied to the aforementioned microactuators would be chosen to effect fine adjustments of the axial positions and the orientations of the segments relative to the supporting structure. Other piezoelectric linear microactuators embedded in the backing structure would enable control of the displacements of the segments along the hexagonal axes; they would also enable control of the curvature of the backing structure and, thus, additional control of the curvature of the reflector.

Yang, Eui-Hyeok↗
NASA NTRS2007

Piezoelectric Polymers Actuators for Precise Shape Control of Large Scale Space Antennas

Extremely large, lightweight, in-space deployable active and passive microwave antennas are demanded by future space missions. This paper investigates the development of PVDF based piezopolymer actuators for controlling the surface accuracy of a membrane reflector. Uniaxially stretched PVDF films were poled using an electrodeless method which yielded high quality poled piezofilms required for this application. To further improve the piezoperformance of piezopolymers, several PVDF based copolymers were examined. It was found that one of them exhibits nearly three times improvement in the in-plane piezoresponse compared with PVDF and P(VDF-TrFE) piezopolymers. Preliminary experimental results indicate that these flexible actuators are very promising in controlling precisely the shape of the space reflectors.

actuators↗
NASA NTRS1989

Advances in large inflatable reflectors

For most applications in space for which they were tried, inflatable structures show a significant weight reduction when compared to mechanical structures. Inflatables are unmatched when compared to mechanical structures when packaged volume is considered. The reliability of deployment of inflatable structures was known for years. When properly designed, such a system is inherently more reliable because it has very few points of failure. Fully inflatable vs. rigidized inflatable structures are discussed. The L'Garde solar concentrator experience is described. Reflector surface and cylinder rigidization, improvement in gore design tools, and expected advances in rigidization schemes with near future are examined.

Thomas, M.↗
NASA NTRS2003

The development of inflatable array antennas

The deployable array antenna using an inflatable or thin-membrane structure has been identified as one of the enabling technologies to achieve low-mass, high packaging efficiency, low cost, and reliable deployment for future NASNJPL spacebome high-gain and large aperture antennas. Array antennas, when compared to parabolic reflectors, although suffering from limited bandwidth performance, offer wide-angle beam scanning capability and a more reliable flat “natural” aperture. To demonstrate the feasibility and capability of this low-mass array technology, three antenna concepts using inflatable and thin-membrane structures were initiated in 1997 at JPL and several breadboard units have been successfully developed. These three concepts are (1) the inflatable phased array, (2) the inflatable reflectarray, and (3) frame-supported thin membrane array antenna. All three concepts utilize the printed microstrip antenna technology. Although all three concepts will be briefly presented, this paper will discuss in more detail of the recent development of the second concept. The first concept of inflatable phased arrays that have been constructed are 3 to 5-meter size L-band dual-polarized synthetic aperture radar (SAR) arrays for Earth remote sensing application. They all consist of a rectangular configuration with inflatable cylindrical tubes that support and tension a multi-layer thin-membrane radiating aperture with microstrip patches and microstrip power divider lines. For the second concept, an inflatable reflectarray was developed for future deep-space telecom applications. It is a 3m Ka-band inflatable reflectarray (1.8 kg/m2). This reflectarray uses inflated torus tubes to support and tension a flat-membrane reflectarray surface. The reflectarray surface emulates a curved parabolic reflecting surface. However, because of its flat surface being a “natural surface”, it is much easier to achieve and more reliable to maintain the required surface tolerance than that of a curved parabola during long space flight. For the third concept, an L-band dual polarized SAR array with a 5m x 3m aperture and 2.5 kg/m2 of mass has recently been demonstrated. It consists of seven foldable panels each having a rectangular frame that supports a two-layer thinmembrane microstrip subarray aperture. Each frame is made of light-weight graphite composite material. The chief advantage of this deployable “frame” concept is that each frame is able to rigidly support an appropriate number of T/R modules and phase shifters to achieve the desired power distribution and beam scanning. Several technology challenges, such as the development of rigidizable inflatable tubes, a controlled deployment mechanism, thin-membrane thermal effects, a low-mass inflation system, membrane mounted T/R modules, means to counter surface tolerance issues, etc. are being investigated and will be discussed in the presentation. With foreseeable success in the development of these challenging areas, the inflatable/thin-membrane array antennas could be mature enough in a few years for actual space flight.

Lou, Michael↗
NASA NTRS2001

Fresnel Concentrators for Space Solar Power and Solar Thermal Propulsion

Large deployable Fresnel concentrators are applicable to solar thermal propulsion and multiple space solar power generation concepts. These concentrators can be used with thermophotovoltaic, solar thermionic, and solar dynamic conversion systems. Thin polyimide Fresnel lenses and reflectors can provide tailored flux distribution and concentration ratios matched to receiver requirements. Thin, preformed polyimide film structure components assembled into support structures for Fresnel concentrators provide the capability to produce large inflation-deployed concentrator assemblies. The polyimide film is resistant to the space environment and allows large lightweight assemblies to be fabricated that can be compactly stowed for launch. This work addressed design and fabrication of lightweight polyimide film Fresnel concentrators, alternate materials evaluation, and data management functions for space solar power concepts, architectures, and supporting technology development.

Bradford, Rodney↗
NASA NTRS1991

Structures technology project summary: Earth orbiting platforms program area of the space platforms technology program

Viewgraphs are presented on the structures technology for the Earth orbiting platforms program. The objective of the work is to develop component and system level structural concepts and design methods to enable in-space construction and deployment of large platform structures in low earth orbit (LEO) and geosynchronous orbit (GEO) including primary platform structures, reflectors and antenna, and habitat and storage modules.

Bush, Harold↗
NASA NTRS1997

Construction of Prototype Lightweight Mirrors

This contract and the work described was in support of a Seven Segment Demonstrator (SSD) and demonstration of a different technology for construction of lightweight mirrors. The objectives of the SSD were to demonstrate functionality and performance of a seven segment prototype array of hexagonal mirrors and supporting electromechanical components which address design issues critical to space optics deployed in large space based telescopes for astronomy and for optics used in spaced based optical communications systems. The SSD was intended to demonstrate technologies which can support the following capabilities; Transportation in dense packaging to existing launcher payload envelopes, then deployable on orbit to form space telescope with large aperture. Provide very large (less than 10 meters) primary reflectors of low mass and cost. Demonstrate the capability to form a segmented primary or quaternary mirror into a quasi-continuous surface with individual subapertures phased so that near diffraction limited imaging in the visible wavelength region is achieved. Continuous compensation of optical wavefront due to perturbations caused by imperfections, natural disturbances, and equipment induced vibrations/deflections to provide near diffraction limited imaging performance in the visible wavelength region. Demonstrate the feasibility of fabricating such systems with reduced mass and cost compared to past approaches. While the SSD could not be expected to satisfy all of the above capabilities, the intent was to start identifying and understanding new technologies that might be applicable to these goals.

Robinson, William G.↗
NASA NTRS1984

Microwave reflector characterization using simple instruments in EVA

An antenna with rigid panels which can be measured under ground conditions, carried to space in a packaged condition, deployed into a form similar to the Earth-measured one, measured under space conditions, restowed, and brought back to Earth so that the original measurements can be verified is the type being proposed for this experiment. The antenna chosen will be measured under ground conditions, carried aloft, deployed into its antenna shape, lifted by the remote manipulator system to a position where it can be sighted by two astronauts at the two theodolites, and held there until the surface characterization can be completed. An alternate method would be to use photogrammetry and take pictures of the surface from the payload handling station. After the surface characterization is completed, the antenna will be folded and restowed into the Shuttle bay for return to Earth. The surface characterization will be repeated on Earth after its return for verification both of the original measurement taken on Earth and the measurement taken in space.

Goslee, J. W.↗
NASA NTRS1986

Near-field testing of the 15-meter model of the hoop column antenna. Volume 3: Near- and far-field plots for the JPL feed

Technical results from near-field testing of the 15-meter model of the hoop column antenna at the Martin Marietta Denver Aerospace facility are discussed. The antenna consists of a deployable central column and a 15 meter hoop, stiffened by cables into a structure with a high tolerance repeatable surface and offset feed location. The surface has been configured to have four offset parabolic apertures, each about 6 meters in diameter, and is made of gold plated molybdenum wire mesh. Pattern measurements were made with feed system radiating at frequencies of 7.73, 11.60, 2.27, 2.225, and 4.26 (all in GHz). This report (Volume 3) gives the detailed patterns measured with the JPL feed (2.225 GHz). Volume 1 covers the testing from an overall viewpoint and contains information of generalized interest for testing large antennas, including the deployment of the antenna in the Martin Facility and the measurements to determine mechanical stability and trueness of the reflector surface, the test program outline, and a synopsis of antenna electromagnetic performance. A detailed listing of the antenna patterns for the LaRC feeds (7.3, 11.60, 2.27, and 4.26 GHz) are given in Volume 2 of this report.

Hoover, J.↗
NASA NTRS1986

Near-field Testing of the 15-meter Model of the Hoop Column Antenna

The technical results from near-field testing of the 15-meter model of the hoop column antenna at the Martin Marietta Denver Aerospace facility are documented. The antenna consists of a deployable central column and a 15 meter hoop, stiffened by cables into a structure with a high tolerance repeatable surface and offset feed location. The surface has been configured to have four offset parabolic apertures, each about 6 meters in diameter, and is made of gold plated molybdenum wire mesh. Pattern measurements were made with feed systems radiating at frequencies of 7.73, 11.60, 2.27, 2.225, and 4.26 (all in GHz). This report (Volume 1) covers the testing from an overall viewpoint and contains information of generalized interest for testing large antennas. This volume discusses the deployment of the antenna in the Martin Facility and the measurements to determine mechanical stability and trueness of the reflector surface, gives the test program outline, and gives a synopsis of antenna electromagnetic performance. Three techniques for measuring surface mechanical tolerances were used (theodolites, metric cameras, and near-field phase), but only the near-field phase approach is included. The report also includes an error analysis. A detailed listing of the antenna patterns are provided for the 2.225 Ghz feed in Volume 3 of this report, and for all other feeds in Volume 2.

Hoover, J.↗
NASA NTRS1986

Near-field testing of the 15-meter model of the hoop column antenna. Volume 2: Near- and far-field plots for the LaRC feeds

The technical results from near-field testing of the 15-meter model of the hoop column antenna at the Martin Marietta Denver Aerospace facility are described. The antenna consists of a deployable central column and a 15-meter hoop, stiffened by cable into a structure with a high tolerance repeatable surface and offset feed location. The surface has been configured to have four offset parabolic apertures, each about 6 meters in diameter, and is made of gold plated molybdenum wire mesh. Pattern measurements were made with feed systems radiating at frequencies of 7.73, 11.60, 2.27, 2.225, and 4.26 (all in GHz). This report (Volume II) gives the detailed patterns measured with the LaRC feeds (7.73, 11.60, 2.27, and 4.26 GHz). Volume I covers the testing from an overall viewpoint and contains information of generalized interest for testing large antennas, including the deployment of the antenna in the Martin Facility and the measurements to determine mechanical stability and trueness of the reflector surface, the test program outline, and a synopsis of antenna electromagnetic performance. A detailed listing of the antenna patterns are provided for the 2.225 Ghz feed in Volume III of this report.

Hoover, J.↗
NASA NTRS1987

Structural concepts for large solar concentrators

The Sunflower large solar concentrator, developed in the early 1970's, is a salient example of a high-efficiency concentrator. The newly emphasized needs for solar dynamic power on the Space Station and for large, lightweight thermal sources are outlined. Existing concepts for high efficiency reflector surfaces are examined with attention to accuracy needs for concentration rates of 1000 to 3000. Concepts using stiff reflector panels are deemed most likely to exhibit the long-term consistent accuracy necessary for low-orbit operation, particularly for the higher concentration ratios. Quantitative results are shown of the effects of surface errors for various concentration and focal-length diameter ratios. Cost effectiveness is discussed. Principal sources of high cost include the need for various dished panels for paraboloidal reflectors and the expense of ground testing and adjustment. A new configuration is presented addressing both problems, i.e., a deployable Pactruss backup structure with identical panels installed on the structure after deployment in space. Analytical results show that with reasonable pointing errors, this new concept is capable of concentration ratios greater than 2000.

Hedgepeth, John M.↗
NASA NTRS1997

Adaptive Full Aperture Wavefront Sensor Study

This grant and the work described was in support of a Seven Segment Demonstrator (SSD) and review of wavefront sensing techniques proposed by the Government and Contractors for the Next Generation Space Telescope (NGST) Program. A team developed the SSD concept. For completeness, some of the information included in this report has also been included in the final report of a follow-on contract (H-27657D) entitled "Construction of Prototype Lightweight Mirrors". The original purpose of this GTRI study was to investigate how various wavefront sensing techniques might be most effectively employed with large (greater than 10 meter) aperture space based telescopes used for commercial and scientific purposes. However, due to changes in the scope of the work performed on this grant and in light of the initial studies completed for the NGST program, only a portion of this report addresses wavefront sensing techniques. The wavefront sensing techniques proposed by the Government and Contractors for the NGST were summarized in proposals and briefing materials developed by three study teams including NASA Goddard Space Flight Center, TRW, and Lockheed-Martin. In this report, GTRI reviews these approaches and makes recommendations concerning the approaches. The objectives of the SSD were to demonstrate functionality and performance of a seven segment prototype array of hexagonal mirrors and supporting electromechanical components which address design issues critical to space optics deployed in large space based telescopes for astronomy and for optics used in spaced based optical communications systems. The SSD was intended to demonstrate technologies which can support the following capabilities: Transportation in dense packaging to existing launcher payload envelopes, then deployable on orbit to form a space telescope with large aperture. Provide very large (greater than 10 meters) primary reflectors of low mass and cost. Demonstrate the capability to form a segmented primary or quaternary mirror into a quasi-continuous surface with individual subapertures phased so that near diffraction limited imaging in the visible wavelength region is achieved. Continuous compensation of optical wavefront due to perturbations caused by imperfections, natural disturbances, and equipment induced vibrations/deflections to provide near diffraction limited imaging performance in the visible wavelength region. Demonstrate the feasibility of fabricating such systems with reduced mass and cost compared to past approaches.

Robinson, William G.↗