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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.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Design of optical mirror structures

The structural requirements for large optical telescope mirrors was studied with a particular emphasis placed on the three-meter Large Space Telescope primary mirror. Analysis approaches through finite element methods were evaluated with the testing and verification of a number of element types suitable for particular mirror loadings and configurations. The environmental conditions that a mirror will experience were defined and a candidate list of suitable mirror materials with their properties compiled. The relation of the mirror mechanical behavior to the optical performance is discussed and a number of suitable design criteria are proposed and implemented. A general outline of a systematic method to obtain the best structure for the three-meter diffraction-limited system is outlined. Finite element programs, using the STRUDL 2 analysis system, were written for specific mirror structures encompassing all types of active and passive mirror designs. Parametric studies on support locations, effects of shear deformation, diameter to thickness ratios, lightweight and sandwich mirror configurations, and thin shell active mirror needs were performed.

Soosaar, K.↗
NASA NTRS2004

JWST: A New Kind of Space Telescope

Contents include the following: Why are the mirrors segmented? Why lightweight segmented mirrors? Why cold (cryogenic) mirrors? Why a space telescope? How did NASA go about developing the mirror technology to enable this? Why was beryllium selected for JWST s mirrors? How are the Beryllium mirrors made? What happens to the mirrors once they are complete?

Keski-Kuha, Ritva↗
NASA NTRS2002

Status of NASA Mirror Technology Development for Large Space Telescopes

This talk will present the current status of several NASA technology development activities, including: SBMD, NMSD, AMSD (Advanced Mirror System Demonstrator), etc.. And will discuss how these activities map into future NASA mission requirements, including: NGST (Next Generation Space Telescope), SAFIR, SUVO, etc.

Stahl, H. Philip↗
NASA NTRS1993

Hubble Space Telescope COSTAR asphere verification with a modified computer-generated hologram interferometer

To correct for the spherical aberration in the Hubble Space Telescope primary mirror, five anamorphic aspheric mirrors representing correction for three scientific instruments have been fabricated as part of the development of the corrective-optics space telescope axial-replacement instrument (COSTAR). During the acceptance tests of these mirrors at the vendor, a quick and simple method for verifying the asphere surface figure was developed. The technique has been used on three of the aspheres relating to the three instrument prescriptions. Results indicate that the three aspheres are correct to the limited accuracy expected of this test.

Feinberg, L.↗
NASA NTRS2002

A Piezoelectric Unimorph Deformable Mirror Concept by Wafer Transfer for Ultra Large Space Telescopes

Future concepts of ultra large space telescopes include segmented silicon mirrors and inflatable polymer mirrors. Primary mirrors for these systems cannot meet optical surface figure requirements and are likely to generate over several microns of wavefront errors. In order to correct for these large wavefront errors, high stroke optical quality deformable mirrors are required. JPL has recently developed a new technology for transferring an entire wafer-level mirror membrane from one substrate to another. A thin membrane, 100 mm in diameter, has been successfully transferred without using adhesives or polymers. The measured peak-to-valley surface error of a transferred and patterned membrane (1 mm x 1 mm x 0.016 mm) is only 9 nm. The mirror element actuation principle is based on a piezoelectric unimorph. A voltage applied to the piezoelectric layer induces stress in the longitudinal direction causing the film to deform and pull on the mirror connected to it. The advantage of this approach is that the small longitudinal strains obtainable from a piezoelectric material at modest voltages are thus translated into large vertical displacements. Modeling is performed for a unimorph membrane consisting of clamped rectangular membrane with a PZT layer with variable dimensions. The membrane transfer technology is combined with the piezoelectric bimorph actuator concept to constitute a compact deformable mirror device with a large stroke actuation of a continuous mirror membrane, resulting in a compact A0 systems for use in ultra large space telescopes.

continuous mirror↗
NASA NTRS2006

Space Optics for the 21st Century

Technological advances over the last decade in metrology, fabrication techniques and materials have made a significant impact on spacebased astronomy and together with advances in adaptive optics offer the opportunity for even more radical changes in the future. The Hubble Space Telescope primary mirror is 2.4 meters in diameter and weighs on the order of 150 kilograms per square meter. The technology demonstration mirrors developed for the James Webb Telescope had an order of magnitude less in area density and developments in membrane optics offer the opportunity to achieve another order of magnitude decrease. Similar advances in mirrors for x-ray astronomy means that across the spectrum future space based telescopes will have greater and greater collecting areas with ever increasing resolution.

Bilbro, James W.↗
NASA NTRS1998

The Case for Aggressive Segmentation of the Primary Mirror of the Next Generation Space Telescope and Future ORIGINS Missions

Optical performance variations are considered from several factors including the gap between regular hexagonal mirror segments, the relative ability of segments of different size to be manufactured with low wavefront error, and expected mirror deformations. Additionally a weight variation function will be driven by recently postulated relationships which can be expressed so as to determine thickness of the mirror segment to satisfy: (1) polishing pressures (2) 1-g sage deflection, and (3) thermal induced stress as well as ancillary masses including actuators, wiring, and electronics. The result will be to survey the trade space of segment number and size for a range of apertures from 4 to 20 meters.

Montgomery, Edward E., IV↗
NASA NTRS2013

Segmented X-Ray Optics for Future Space Telescopes

Lightweight and high resolution mirrors are needed for future space-based X-ray telescopes to achieve advances in high-energy astrophysics. The slumped glass mirror technology in development at NASA GSFC aims to build X-ray mirror modules with an area to mass ratio of approx.17 sq cm/kg at 1 keV and a resolution of 10 arc-sec Half Power Diameter (HPD) or better at an affordable cost. As the technology nears the performance requirements, additional engineering effort is needed to ensure the modules are compatible with space-flight. This paper describes Flight Mirror Assembly (FMA) designs for several X-ray astrophysics missions studied by NASA and defines generic driving requirements and subsequent verification tests necessary to advance technology readiness for mission implementation. The requirement to perform X-ray testing in a horizontal beam, based on the orientation of existing facilities, is particularly burdensome on the mirror technology, necessitating mechanical over-constraint of the mirror segments and stiffening of the modules in order to prevent self-weight deformation errors from dominating the measured performance. This requirement, in turn, drives the mass and complexity of the system while limiting the testable angular resolution. Design options for a vertical X-ray test facility alleviating these issues are explored. An alternate mirror and module design using kinematic constraint of the mirror segments, enabled by a vertical test facility, is proposed. The kinematic mounting concept has significant advantages including potential for higher angular resolution, simplified mirror integration, and relaxed thermal requirements. However, it presents new challenges including low vibration modes and imperfections in kinematic constraint. Implementation concepts overcoming these challenges are described along with preliminary test and analysis results demonstrating the feasibility of kinematically mounting slumped glass mirror segments.

McClelland, Ryan S.↗
NASA NTRS2001

Mirror Technology Development at MSFC for the Next Generation Space Telescope and Other Space Telescope Missions

Large-aperture low-areal-density mirrors are critical to the success of the Next Generation Space Telescope (NGST) as well as other related space missions such as the Space Based Laser (SBL). Currently fabrication technology has demonstrated areal densities of 50 kg/sq m. NASA and its DOD partners are conducting a series of risk reduction projects to demonstrate mirror fabrication technology for mirror systems with areal densities of 15 kg/sq m. This talk will present an overview of these risk reduction experiments.

Stahl, H. Philip↗
NASA NTRS1973

A technique for designing active control systems for astronomical telescope mirrors

This paper considers the problem of designing a control system to achieve and maintain the required surface accuracy of the primary mirror of a large space telescope. Control over the mirror surface is obtained through the application of a corrective force distribution by actuators located on the rear surface of the mirror. The design procedure is an extension of a model control technique developed for distributed parameter plants with known eigenfunctions to include plants whose eigenfunctions must be approximated by numerical techniques. Instructions are given for constructing the mathematical model of the system, and a design procedure is developed for use with. typical numerical data in selecting the number and location of the actuators. Examples of actuator patterns and their effect on various errors are given.

Active optics↗
NASA NTRS2013

Advanced Mirror Technology Development (AMTD) for Very Large Space Telescopes

Accomplishments include: Assembled outstanding team from academia, industry and government with expertise in science and space telescope engineering. Derived engineering specifications for monolithic primary mirror from science measurement needs & implementation constraints. Pursuing long-term strategy to mature technologies necessary to enable future large aperture space telescopes. Successfully demonstrated capability to make 0.5 m deep mirror substrate and polish it to UVOIR traceable figure specification.

Stahl, H. Philip↗
NASA NTRS2000

Finite Element Modeling of a Semi-Rigid Hybrid Mirror and a Highly Actuated Membrane Mirror as Candidates for the Next Generation Space Telescope

Advanced space telescopes, which will eventually replace the Hubble Space Telescope (HTS), will have apertures of 8 - 20 n. Primary mirrors of these dimensions will have to be foldable to fit into the space launcher. By necessity these mirrors will be extremely light weight and flexible and the historical approaches to mirror designs, where the mirror is made as rigid as possible to maintain figure and to serve as the anchor for the entire telescope, cannot be applied any longer. New design concepts and verifications will depend entirely on analytical methods to predict optical performance. Finite element modeling of the structural and thermal behavior of such mirrors is becoming the tool for advanced space mirror designs. This paper discusses some of the preliminary tasks and study results, which are currently the basis for the design studies of the Next Generation Space Telescope.

Craig, Larry↗
NASA NTRS1992

Arm deploy mechanisms to help correct the Hubble Space Telescope's vision

As has been well publicized, the primary mirror of the Hubble Space Telescope was manufactured with an incorrect curvature which results in an aberrated output image. Ball Aerospace, under contract to GSFC, is designing the Corrective Optics Space Telescope Axial Replacement (COSTAR) to provide correcting optics for the existing axial science instruments in the telescope. Integral to COSTAR are the arm deploy mechanisms which position and hold the corrective optic mirrors.

Copeland, F. Kent↗
NASA NTRS1985

Temperature control of silica mirrors for cryogenically-cooled telescopes in space

The SIRTF (Space Infrared Telescope Facility) optical subsystem, including the primary mirror, has been modeled using lumped-parameter techniques and a thermal and cryogenic transient analysis program developed previously. Since silica mirrors have been shown to have significantly less distortion due to cryogenic cooldown, a silica primary mirror of approximately 1 m diameter is being considered. Thermal responses to variations in aperture heat load and heat sink temperature have been explored. Calculations have been made of system noise components from primary mirror spatial and temporal temperature variations. Background-limited infrared observations can be made at wavelengths out to 200 micrometers. Mirror thermal performance with and without copper wires for cooling is also considered.

Melugin, R. K.↗
NASA NTRS1987

Space ten-meter telescope (STMT) - Structural and thermal feasibility study of the primary mirror

The structural and thermal behavior of a ten-meter primary mirror for a space optical/near-IR telescope in geosynchronous orbit is studied. The glass-type lightweighted mirror is monolithic, of the double arch type, and is supported at only three points. The computer programs SSPTA (thermal), NASTRAN (finite element), and ACCOS V (optical) are used in sequence to determine the temperature, deformation, and optical performance of the mirror. A mirror temperature of 130 K or less appears to be obtainable by purely passive means. With a fused silica or standard Zerodur blank, thermally-induced deformation is unacceptable and cannot be fully corrected by an active secondary mirror over the desired field. Either active thermal control or a blank of lower thermal expansion coefficient would be required.

Bely, Pierre Y.↗