The James Webb Space Telescope (JWST) is an on axis three mirror anastigmat telescope with a primary mirror, a
secondary mirror, and a tertiary mirror. The JWST mirrors are constructed from lightweight beryllium substrates and the
primary mirror consists of 18 hexagonal mirror segments each approximately 1.5 meters point to point. Ball Aerospace
and Technologies Corporation leads the mirror manufacturing team and the team utilizes facilities at six locations across
the United States. The fabrication process for each individual mirror assembly takes approximately six years due to
limitations dealing with the number of segments and manufacturing & test facilities. The primary mirror Engineering
Development Unit (EDU) recently completed the manufacturing process with the final cryogenic performance test of the
mirror segment assembly. The 18 flight primary mirrors segments, the secondary mirror, and the tertiary mirror are all
advanced in the mirror production process with many segments through the final polishing process, coating process, final
assembly, vibration testing, and final acceptance testing. Presented here is a status of the progress through the
manufacturing process for all of the flight mirrors.
The paper will describe the new technologies utilizing aluminum beryllium (AlBeMet®) for optical systems. Focusing
on advances in gimbal / structures through the use of electron beam welding. The paper will also discuss the
characterization of material as an optical substrate, at room temperature and at cryogenic temperatures.
A new grade of beryllium, O-30, has been chosen for the primary, secondary, and tertiary cryogenic optics for the James Webb Space Telescope (JWST) program. This paper will describe the characterization of O-30 beryllium for this cryogenic space telescope, including cryogenic material properties. It will also show the cryogenic performance data that resulted in the selection of the O-30 beryllium for the JWST primary mirror, as compared to the other material candidate ULE. The paper will also describe the consolidation process of this 1.315-meter hexagon segment to produce a highly isotropic mirror segment. In addition, this paper will describe a technology effort called near net shape (NNS), to significantly reduce the cost of beryllium substrates for future cryogenic telescopes like SPICA, SAFIR, and GMST.
The use and manufacturing of AlBeMet 162 material as an optical substrate for head mirrors, night vision systems and fire control optics is discussed. The paper discusses the validation AlBeMet 162's thermal stability over the military environmental temperature range of -40F to +140F. The paper will discuss the manufacturing processing to yield dimensional stable optics in AlBeMet material. It will also discuss the results of interferometric testing on 150 mm diameter flats produced by 3 separate optical fabrication companies. Demonstrating the ability of the process and material to produce optical mirrors over temperature with thermal distortions of less than 0.25 wavelengths P-V. The paper will show interfermetrically that AlBeMet and nickel have an excellent coefficient of thermal expansion match over the temperature range of interest, so that there is no bi-metallic issue or distortion due to the electroless nickel. The paper will also discuss the continuing characterization program with the initial results from testing a light weighted substrates with a spherical surface.
The paper will focus on three main areas; thermal and physical characterization of the new O-30 optical grade of beryllium at cryogenic temperatures; the development of a leachable mandrel technology for near net shaped (NNS) parts in beryllium and AlBeMet®; finally the paper will report on the optical characterization of AlbeMet® as an optical substrate material.
This paper will discuss the state of these technologies: Vacuum Hot Press Bonding, Near Net Shape Forming with re- useable mandrels, and the development of the O-30 material. The paper will also attempt to show how these new manufacturing technologies addresses the perception that beryllium is an expensive, long lead material.
Beryllium has been used as an optical and structural material for astronomical/IR telescope applications for the past 20 years. Some of the most recent applications have been for the VLT (Very Large Telescope) M2 secondary mirror, SIRTF (Space Infrared Telescope Facility), plus many other space based IR sensors. The traditional forms and optical grades of the material, I-70H and I-220H, are well characterized from a mechanical and thermal standpoint over a wide range of temperatures. Beryllium's limiting factor's for astronomical and/or IR telescopes has been traditionally two fold: cryogenic stability and perceived higher cost than some of the other material options, such as glass, silicon carbide, and some composites. To address those two factors, Brush Wellman has developed a new optical grade of Beryllium produced by gas atomization (spherical powder) called O-30. This paper will detail the development of this grade of Beryllium, with emphasis on the cryogenic properties of the material from a thermal and mechanical view. It will also report on the results of the optical polishing/thermal cycling work done under government sponsored contracts. Finally the paper will describe the process of producing Near Net Shape parts utilizing O-30 spherical powder in order to reduce manufacturing cost and schedule.
A newly developed family of Aluminum Beryllium (AlBeMet®) metal matrix composite materials has been developed for use in. satellite, structures to address the needs of the designer for lightweight, stiff, thermally stable structures. This paper will present a overview of the development of these metal matrix composites materials and their use in satellite structures.
Lightweight and high modulus Aluminum - Beryllium composites offer significant performance advantages over traditional aluminum and organic composite materials. Aluminum- Beryllium composites also can be fabricated using conventional aluminum machining, joining, and coating technologies thereby reducing the cost of the final assembly and eliminating any special tooling or non destructive testing(NDT) that is sometimes required when designing and fabricating structures out of fiber reinforced composites.
This paper will present the thermal, physical, and mechanical properties of these composites, as well as providing structural test data for satellite components that have utilized aluminum - Beryllium materials, such as the ORBCOMMsm 1 satellites.
REOSC has been selected for the design, manufacturing and integration of the four ESO very large telescope (VLT) secondary mirrors. The VLT secondary mirrors are 1.12 m lightweight convex hyperbolic mirrors made of beryllium. Despite the VLT active optics correction capabilities, the use of a metal for the mirror structure implies specific manufacturing processes and associated design rules in order to ensure its dimensional stability during the telescope required life time. This paper describes how the fabrication process of the VLT secondary mirror has been optimized in order to maximize the dimensional stability of its structure. The beryllium properties are analyzed in parallel with the mirror requirements, the choices for the manufacturing, at all levels, are presented. A short work progress is presented, with the achieved mirror properties.
Stability of beryllium mirrors is said to be unpredictable. Three recent mirrors demonstrate excellent stability. JPL produced a plano-concave, 0.5 m solid test mirror that was machined from a HIP'ed billet of special I-70 Be powder, polished bare and tested to 4K. It was thermally stable and had no hysteresis. The JPL ITTT 0.85 m primary mirror used similar material and processes, but with more stress relied treatments. Tests of this bare-polished, very lightweight single arch hyperboloidal mirror to 5K showed similar excellent results. The ESO VLT chopping secondary is a 1.12 m, machined lightweight, nickel plated, convex paraboloid. Similar fabrication processes are being used but with higher strength I-220 Be. In-processes testing indicates a stable mirror. The results show beryllium to be a stable and predictable mirror material.
The properties of four candidate mirror materials--beryllium, silicon carbide,
a silicon carbide/aluminum iretal-matrix carposite and aluminum--are corrpared.
Because of its high specific stiffness and dirrensional stability under changing
mschanical and thermal loads , beryllium is the best choice . Berjllium mirrors have
been made irore cost-conpetitive by new processing technologies in which mirror
blanks are isostatically pressed to near-net shape directly fran beiyllium pc1ers.
Isostatic pressing also improves material properties and mskes it possible to
develop mirror rraterials with superior properties.