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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Dynamic considerations of dust on the television camera mirror

The mirror on the Surveyor 3 television camera was subjected to tests which modified its surface. Lunar dust was removed by rubbing, by acetate and metallic film stripping techniques, rinsing, scraping, and by inadvertently touching the surface. A second shadow line was revealed. Second and third generation peels were taken across the upper shadow line, and a study was made in order to define the source(s) or events(s) responsible for creating the two shadow lines occurring on the lower part of the mirror.

Nickle, N. L.↗
NASA NTRS1972

Evaluation of the thin deformable active optics mirror concept

The active optics concept using a thin deformable mirror has been successfully demonstrated using a 30 in. diameter, 1/2 in. thick mirror and a 61 point matrix of forces for alignment. Many of the problems associated with the design, fabrication, and launch of large aperture diffraction-limited astronomical telescopes have been resolved and experimental data created that can provide accurate predictions of performance in orbit.

Robertson, H. J.↗
NASA NTRS1972

Nuclear light bulb propellant heating simulation using a tungsten/argon aerosol and radiation from a dc arc surrounded by a segmented mirror cavity

Experiments were conducted to simulate radiant heating of the propellant stream of a nuclear light bulb engine to obtain high bulk exit temperatures in the flowing simulated propellant stream by absorption of large fractions of the incident thermal radiation. A high-power, vortex-stabilized dc arc within an uncooled fused silica tube was used as the radiant energy source. It was surrounded by a mirror system to increase the radiation incident on the simulated propellant. The 12.7-cm-long by 2.3-cm-wide, diverging-duct test section had a transparent front wall and a reflecting rear wall. The central stream of seeded gas, a tungsten-particle/argon aerosol, had unseeded argon buffer layers on both sides to prevent coating of the duct walls. Arc operating times were approximately 0.5 sec with power levels up to 780 kW. Bulk exit temperatures were measured using a calorimeter downstream of the duct. The maximum simulated propellant bulk exit temperature obtained was 4515 K, compared with 3860 K in previous tests, 3300 to 3700 K expected in in-reactor tests in the Nuclear Furnace, and 6660 K in the reference nuclear light bulb engine. The maximum temperature in these tests was limited primarily by the amount of radiation incident on the test section (determined by the arc operating characteristics and the effectiveness of the mirror cavity).

Klein, J. F.↗
NASA NTRS1972

Special report, exit slit mirrors for the Ebert spectrometer

The use of a very long straight entrance slit in an Ebert grating spectrometer with two plane mirrors at the shorter exit slit to increase the energy density is described. This system has been employed in a far ultraviolet rocket spectrometer to provide higher sensitivity than has been achieved previously. The imaging properties and required slit and mirror adjustments are presented. Experimental results are included.

Fastie, W. G.↗
NASA NTRS1974

Inexpensive lightweight mirror

Aluminized Mylar film is bonded to polyurethane foam mold; Mylar is then removed, leaving highly reflective coating of aluminum on foam. Mold may be used repeatedly to make mirrors for several optical instruments. Large mirrors of almost any shape may be made singularly or in quantity.

Badhwar, G. D.↗
NASA NTRS1974

LST secondary mirror articulation mechanism

The analysis, design, manufacture, test, and delivery of one secondary mirror articulation mechanism for the large space telescope (LST) are reported. The mechanism provides angular freedom about two axes that are perpendicular to the optical axis of the secondary mirror. Motion in each axis is controlled from two sources; one source provides alignment, the other source provides stabilization. Two articulation mechanism configurations were evaluated. In one configuration the stabilization system was assembled with piezoelectric actuators. In the second configuration the stabilization system utilized flexure torque motor actuators. The alignment system was the same for both configurations. System testing confirmed performance that met or exceeded all operational requirements. The two types of stabilization actuators had different performance characteristics. Both types demonstrated position resolution and frequency response better than specified limits.

Source record↗
NASA NTRS1974

Test program on the contamination of ultraviolet region mirrors by Apollo Telescope Mount materials

Results are presented of testing performed to measure the effects of material outgas products on the reflectances of ultraviolet-region mirrors. These tests were to provide data on changes of ultraviolet reflectances of first-surface mirrors which had been exposed to the outgas products of selected materials under specific time and thermal-vacuum conditions. The requirement for such data was based on the extreme sensitivity of the sophisticated optical instruments in the Skylab mission's Apollo Telescope Mount (ATM) to condensed outgas products from materials, and on the desire to insure that no serious hazard of contaminating these instruments existed.

Austin, J. D.↗
NASA NTRS1975

Analysis and trade-off studies of large lightweight mirror structures

A candidate mirror, hexagonally lightweighted, is analyzed under various loadings using as complete a procedure as possible. Successive simplifications are introduced and compared to an original analysis. A model which is a reasonable compromise between accuracy and cost is found and is used for making trade-off studies of the various structural parameters of the lightweighted mirror.

Soosaar, K.↗
NASA NTRS1975

Phase correction for a Michelson interferometer with misaligned mirrors

The phase correction for a Michelson interferometer with misaligned mirrors in converging light is shown to give rise to a quadratic phase shift. In general, the calculation of a spectrum from the measured interferogram needs phase correction. Phase corrections have been well worked out for the cases of a linear phase shift and a phase that is slowly varying. The standard procedures for correcting calculated spectra need to be modified, however, to remove any phase errors resulting from misaligned mirrors.

Goorvitch, D.↗
NASA NTRS1976

Polishing technique for beryllium mirror

Performance tests, accomplished by inserting entire X ray telescope and polished mirror into vacuum line 67 m long and taking photographs of an X ray resolution source, indicate that polishing increases mirror efficiency from 0.06 percent for X rays at 0.8 nm and increases resolution from 15 to 3.75 arc-seconds.

Froechtenigt, J. F.↗
NASA NTRS1975

Effects of high energy simulated space radiation on polymeric second-surface mirrors

A radiation effects experimental program was performed, in which second surface mirror type thermal control coatings were exposed to ultraviolet radiation, electrons, and protons simultaneously. Stability was assessed by making periodic spectral reflectance measurements in situ (and in air after testing for comparison). Solar absorption coefficients were derived by computer. Many of the exposed materials showed large amounts of degradation in reflectance absorptance, principally due to the electron exposure. A series of tests was conducted, leading to the identification of a modified second surface mirror that shows considerable improvement and promise for stability during thermal control applications in a charged particle space radiation environment.

Eogdall, L. B.↗
NASA NTRS1976

Coma of modified Gregorian and Cassegrainian mirror systems

The equivalence of the classical Newtonian, Cassegrainian, and Gregorian mirror systems with respect to the first two Seidel aberrations is rederived by means of a simple congruence. The effects of arbitrary small modifications of the two mirror systems are then studied and general formulas are derived for the effects of such modifications on the spherical aberration and coma. Spherical aberration is corrected to the third order if the amount of glass removed from one surface is replaced at the corresponding zone of the other surface. Modifications in which one surface is made spherical while the other is adjusted to eliminate spherical aberration result in large increases of coma for systems having the usual amplifying ratios.

Jones, R. T.↗
NASA NTRS1976

A high resolution, adjustable, lockable laser mirror mount

A prototype high resolution, adjustable, lockable mirror mount is described, suitable for use as a resonator end mirror mount in fieldable lasers. The prototype was vibrated to 15g levels, 10-2000 Hz, and was shown to be stable to within 1 arc second and settable to an accuracy of 10 arc seconds. Improvements to be made to the prototype are outlined which will significantly improve the accuracy without sacrificing the other attributes of the prototype.

Chadwick, C. H.↗
NASA NTRS1976

Active image restoration with a flexible mirror

The 30 by 5 cm aperture telescope described uses six moveable mirrors to compensate for phase distortions induced by the atmosphere. A feedback system is used to adjust the mirrors in real time to maximize the intensity of light passing through a narrow slit in the image plane. Using the telescope, diffraction-limited images of objects were obtained, using both laser and white light, through 250 meters of turbulent atmosphere.

Buffington, A.↗
NASA NTRS1977

Auger spectroscopic examination of MgF2-coated Al mirrors before and after UV irradiation

Magnesium fluoride protected Al films were studied since these mirrors are commonly used in astronomical instruments whenever a highly reflecting optical surface is required in the wavelength region from 1100 A to 2000 A. Freshly prepared samples of evaporated Al + 250-A thick MgF2 on glass were analyzed by Auger electron spectroscopy in conjunction with surface erosion by Ar(+) ion bombardment before and after UV irradiation. The analysis showed that a very thin layer of surface contamination and not bulk photolysis in the MgF2 film was reponsible for the irradiation-induced reflectance loss. Postirradiation polishing with a mild calcium carbonate abrasive can restore a mirror's reflectance by removing the photolyzed surface film without disturbing the MgF2 layer.

Heaney, J. B.↗
NASA NTRS1978

Alignment displacements of the solar optical telescope primary mirror

Solar optical telescope is a space shuttle payload which is at the present time (1978) being planned. The selected alignment method for the telescope's primary mirror is such that the six inclined legs supporting the mirror are at the same time motorized alignment actuators, changing their own length according to the alignment requirement and command. The alignment displacements were described, including circumvention of some apparent NASTRAN limitations.

Medenica, W. V.↗
NASA NTRS1978

Reflection polarizers for the vacuum ultraviolet using Al + MgF2 mirrors and an MgF2 plate

Consideration is given to the design and operation of a three-mirror reflecting polarizer where one of the reflecting surfaces is an MgF2 plate, the other surfaces are Al + MgF2 coatings, and one reflection occurs at or near the true Brewster angle. It is found that the polarizer is most efficient in the 1200-2000 A wavelength region, and that by optimum selection of the angle of incidence on the MgF2 plate, polarization values of 100 and over are yielded from 900 to 3000 A. The polarizer may be used at wavelengths as short as 500 A, although it is observed that at such wavelengths the polarization value decreases to about 10. It is noted that all reflecting polarizers operating in the vacuum ultraviolet wavelength may manifest changing characteristics as their mirrors become contaminated, and that polarization must therefore be occasionally remeasured.

Hass, G.↗
NASA NTRS1979

Evaluation of cellular glasses for solar mirror panel applications

An analytic technique was developed to compare the structural and environmental performance of various materials considered for backing of second surface glass solar mirrors. Cellular glass was determined to be a prime candidate due to its low cost, high stiffness-to-weight ratio, thermal expansion match to mirror glass, evident minimal environmental impact and chemical and dimensional stability under conditions of use. The current state of the art and anticipated developments in cellular glass technology are discussed; material properties are correlated to design requirements. A mathematical model is presented which suggests a design approach which allows minimization of life cost; and, a mechanical and environmental testing program is outlined, designed to provide a material property basis for development of cellular glass hardware, together with methodology for collecting lifetime predictive data. Preliminary material property data from measurements are given. Microstructure of several cellular materials is shown, and sensitivity of cellular glass to freeze-thaw degradation and to slow crack growth is discussed. The effect of surface coating is addressed.

Giovan, M.↗