TOPIC 25 ULTRALIGHT STRUCTURES AND SPACE OBSERVATORIES

The objectives of this topic are to stimulate technology breakthroughs in ultra-lightweight space structures, advanced materials, and large optical systems that will enable new visions of the Earth and the Universe, allow future missions to reach new vantage points in space, and expand the frontiers of exploration with lower cost and more capable spacecraft. The Ultra-Lightweight Structures and Space Observatories topic encompasses subtopics in inflatable structures, low density materials, smart materials and actuators, optical systems, thermal protection systems, and space environmental effects. High-priority mission applications for the technologies developed in these areas include: 1) very large aperture telescopes and interferometers for detecting extra-solar planets, imaging galaxies at the edge of the Universe, and remote sensing of the Earth from distant vantage points; 2) large antennas for space-based radio astronomy, microwave radiometers, synthetic aperture radar, and deep-space communications; 3) solar sails for low cost rapid transit, station-keeping in non-Keplerian orbits, and interstellar exploration; and 4) hypersonic vehicles, planetary entry vehicles, and spacecraft operating in extreme environments.

Innovative concepts are sought for the development of materials, processes, electronics and systems to mitigate, and/or survive the space environment, and techniques that predict the environment experienced by spacecraft in the near-Earth and deep space environments. This subtopic is concerned with the electromagnetic fields, ionizing radiation, meteoroid and orbital debris, contamination, plasma and thermosphere, and thermal and solar components of the environment. Specific areas for which proposals are sought include:

• Miniature sensors to measure the vehicle environment and life-predicting tools based on previous flight-experiment data and models.
• Elimination of contamination on spacecraft surfaces and/or mechanisms for in-flight cleaning.
• Approaches for measuring, predicting, and verifying spacecraft molecular and particulate contamination, including reliable molecular monitoring systems, compact particulate-monitoring systems, and mass-transport models to predict molecular direct-transfer, backscattering, particle transport, and surface effects.
• Low cost, lightweight materials and protective coatings that mitigate environmental effects.
• New processing and application techniques that reduce the cost of current, space-qualified materials and coatings.
• Cost-effective methods for ground-based simulation of the environment.
• Techniques for electrically grounding spacecraft to mitigate spacecraft charging and mitigation design guidelines.
• Preventing or mitigating the effects of space plasma electrical discharges on solar arrays and surfaces.
• Instrumentation to determine absolute electrical potentials of interplanetary and planetary surface spacecraft.
• Stable, electrically conductive but thermally advantageous coatings for spacecraft surfaces.
• Electrically insulating materials with the capability of "bleeding off" buried charge.
• Instrumentation to detect in-situ buried charge in insulators.
• Controlling spacecraft potentials actively or passively.
• Other methods to mitigate harmful effects of space plasma and spacecraft charging.
• Damage location and mitigation technologies for meteoroids /orbital debris.
• Development of mitigation design guidelines for ionizing radiation.
• Electromagnetic Interference (EMI) susceptibility characterization of new technology devices.
• Developing innovative, low cost electronic components or systems that show tolerance to the infrared (IR) environment.
• New materials and coatings, including electrically conductive, thermal-control coatings that mitigate the environmental effects.

Device for cleanrooms to measure particulate and/or molecular contamination of surfaces exposed to gaseous environment. Adaptation of quartz crystal microbalance technology, or other innovative technology, for use in monitoring cleanrooms and sample processing enclosures. Sensitivity of ng/cm2 deposition desired, and the device should be portable and designed to not add contamination to the cleanroom.

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Large ultralight inflatable structures have the promise of revolutionizing 21st century spacecraft. Such a spacecraft would no longer consist of a collection of heavy electronics "boxes" and frames, but instead, of extremely lightweight membranes, fibrous materials, foams and flexible microelectronics components imbedded into polymers. This new "Gossamer" spacecraft will occupy very small stow volume at launch but be capable to assume a large form in space through inflation or self-deployment. Proposals are solicited for breakthrough Gossamer spacecraft architectures and ultralight structure technology development.

In particular, one of the most attractive propulsion systems for Gossamer spacecraft are solar sails. Solar sails are expected to significantly improve low-Earth orbit and deep-space missions and enable ambitious missions such as non-Keplerian orbits and interstellar probes. To achieve this promise requires integrated sail systems with areal densities between 0.1-10 g/m2 and sail areas from 10 m to greater than 1000 m in diameter. Innovative technologies in the areas of sail systems, booms, films and hybrid fiber-film-inflatable structures will be considered.

Proposals are solicited for the following:

• Sail systems characterized by low packaging volume while enabling large deployed sizes at very low areal densities. Concepts, modeling and demonstration of sail systems including sail configurations, sail assembly, storage, integration to spacecraft, deployment, and control.
• Boom concepts for inflatably deployed booms, composite booms, and other innovative new boom concepts with emphasis on materials and rigidization concepts. Innovative methods to reduce film stress and boom loads are particularly important.
• Thin film fabrication methods, metallization, ripstop, handling, folding and storage, and film characterization.
• Breakthrough Gossamer spacecraft architectures using ultralight large structures.

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Innovative approaches are being sought for the development of low-density materials, processing and fabrication technology, forming and joining technology, and process modeling to lower the weight, improve structural efficiency, and reduce the acquisition costs of airframe structures, launch vehicles, and spacecraft. Low-density materials include polymers, polymer-matrix composites, light metallic alloys, metal-matrix composites, metal laminates, inorganic glasses, ceramics, ceramic-matrix composites, carbon-carbon composites, refractory-matrix composites, material system blends, composite reinforcement architectures, adhesives, films, sealants, coatings and insulating systems. The anticipated airframe structural applications of low-density materials include a variety of service environments and temperatures ranging from cryogenic to elevated temperatures projected for supersonic and hypersonic airframe structures. These low-density materials also may have applications on small satellites, manned platforms and associated instrument subsystems in space environments ranging from low Earth orbit to geosynchronous orbit.

Future spacecraft designs require substantial weight reduction in order to reduce cost yet maintain equivalent or improved performance. New materials technology that provides high thermal conductivity with reduced mass is sought. In many applications, these materials must be capable of carrying structural loads as well. Low coefficient of thermal expansion (CTE) is also beneficial in many applications. Low cost manufacturing methods of these materials are sought, as many current materials are prohibitively expensive to produce. Applications in both cryogenic and room temperature regimes are solicited.

Specific areas for which proposals are sought include the following:

• Spacecraft structural material.
• Aeroshells.
• Low CTE optical benches and mirrors.
• Instrument and electronics box enclosures.
• Mechanical interface material between electronics boxes and spacecraft baseplates.
• Cost reduction methods for producing candidate materials.

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Mechanical and Electromechanical Systems

New concepts are sought in active structures, multifunctional structures, mechanisms, control systems, transducer technology, and electronics as they apply to the development of advanced mechanical and electromechanical components or systems for use in spacecraft or precision space flight instruments. The scope includes new techniques and tools for modeling, analysis, design, and test of mechanical and electromechanical components and systems. Development of new materials and/or fabrication processes should be geared toward producing concepts that will directly enable reliable operation in the space environment with increased performance and efficiency while reducing design and production costs.

• Regulating and tracking mechanisms like precision scanning and pointing mechanisms and fast beam steering mirror mechanisms.
• Low power and long life mechanisms, including magnetic bearings that can be used in instruments operating in cryogenic environments of a few degrees Kelvin.
• Low vibration reaction and momentum wheels and high speed flywheels for the integration of the spacecraft attitude and power systems.
• Micro-Electro-Mechanical Systems (MEMS) and Micro-Opto-Electro-Mechanical Systems (MOEMS), including packaging, for instruments.
• Active vibration control of large lightweight structures and vibration isolation platforms that counter microphonic disturbances to delicate mechanisms or the detector assembly in a precision instrument.
• Active and adaptive optics such as deformable and segmented mirrors.
• Low cost manufacturing techniques for small and large flight structures which are not mass-produced.
• Lightweight precision deployable structures. Structures must be extremely compact for launch and have a reliable and repeatable deployment scheme. Structural stability over wide temperature ranges is emphasized.
• Multifunctional structures (e.g., structures that combine electronics and/or thermal management) and structures with extremely high or extremely low thermal conductivity.
• Novel deployment-to-orbit mechanisms for multiple (micro, nano, or pico) satellite systems.

Optical Components and Processing

The continued need to reduce cost and improve performance of future scientific payloads involving optics requires innovations in optical component technologies encompassing the electromagnetic spectrum from the gamma ray through the infrared. These innovations are to support new astronomy, astrophysics, planetary- and Earth-observing experiments, which must be miniaturized, made significantly lighter, and/or include significant improvements in capabilities. Aspects of instrument development that can benefit from new technology cover the spectrum from optical system design and modeling, through optical materials, fabrication technologies and thin-film coatings and their characterization, to wavefront sensing and component and subsystem testing. These need to be applied to integrated optical system components such as spectrometers, hyperspectral systems, and diffractive elements.

• Improved optical techniques for image-motion compensation and image quality.
• Novel techniques for producing high-performance, low-scatter, optical materials and coatings for use from soft X-ray through far IR in reflector, filter, polarizer, and beamsplitter applications.
• High-accuracy measurements of refractive index at cryogenic temperatures.
• Thin foil filters and proportional counter windows and high-throughput, rugged support meshes for the x-ray and EUV regions.
• High-performance, diamond-turned optics and lightweight silicon carbide optics and structures are desired.
• Techniques for producing smooth diamond membranes for X-ray and IR window applications.
• Thin film technology for the soft X-ray through EUV spectral regions, including advances in high-throughput, low-scatter, defect-free coatings, and defect-mapping methodology, particularly for mirrors in the 13-nm region.
• State-of-the-art optical characterization instrumentation for miniaturized components.
• Novel optical system design and analysis software, particularly with regard to factoring in as-manufactured performance and programmatic parameters.

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Novel optical materials, specialized optical fabrication techniques, and new optical metrology instruments and components for Earth- and space-based applications are needed, as follows:

• Develop novel materials and fabrication techniques for producing ultra-lightweight mirrors, high-performance diamond turned optics, and ultra-smooth (2-3 angstrom rms) replicated optics that are both rigid and lightweight. Lightweight silicon carbide optics and structures are also desired.
• Develop optics for focusing EUV and x-ray radiation, where reductions in fabrication time and cost are sought. Developments are also needed in the areas of surface roughness and figure characterization of EUV and curved x-ray optics, especially Wolter systems.
• Develop novel materials and fabrication techniques for producing cryogenic optics. Testing techniques, including both full- and sub-aperture testing, for cryogenic optics are needed. Also desired are techniques for testing the durability of and stress in coatings used in harsh environments, particularly cryogenic optics.
• Develop novel techniques for producing and measuring coatings and polarization control elements. Optical coatings for use in the EUV, UV, visible, IR and far IR for filters, beamsplitters, polarizers, and reflectors will be considered. Broadband polarizing- and non-polarizing cube-type beamsplitters are also needed.
• Perform development related to fabrication of x-ray, gamma-ray, and neutron collimators that have the precision necessary to achieve arcsecond or sub-arcsecond imaging in solar physics and astrophysics when used in stationary multi-grid arrays or as rotating modulation.
• Develop portable and miniaturized state-of-the-art optical characterization instrumentation and rapid, large-area surface-roughness characterization techniques are needed. Also, develop calibrated processes for determination of surface roughness using replicas made from the actual surface. Traceable surface roughness standards suitable for calibrating profilometers over sub-micron to millimeter wavelength ranges are needed.
• Develop instruments capable of rapidly determining the approximate surface roughness of an optical surface, allowing modification of process parameters to improve finish, without the need to remove the optic from the polishing machine. Techniques for testing the figure of large, convex aspheric surfaces to fractional wave tolerances in the visible are needed.
• Develop efficient, analytical, optical modeling and analysis programs capable of determining the ground-based and space-based performance of complex aberrated optical telescopes and instrument systems will be considered. Also, simple, well documented, flexible programs which generate commands to operate a numerically controlled polishing machine, given the tool wear profile and surface error map are desired.
• Develop very low scattered light optical material thin film mirror coatings or mirrors for broad-band white light applications to planet detection space telescopes.
• Develop a novel material for producing doubly curved, ultra-thin, unsupported shell optical quality telescope mirrors which are capable of being rolled for storage and transport. These mirrors will exceed one meter in diameter, have an areal density of < 1.5 kg/m2, and have sufficient "memory" to enable it to return to its original configuration when unfurled. Fine adjustment to ½ wave will be achieved using actuator material embedded within the shell mirror or with a two-stage optics system or both. The reflective surface would not be damaged when the mirror is rolled. This material must tolerate the space environment without dimensional changes, stiffness changes, or loss of mechanical integrity.

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Future hypersonic vehicles and spacecraft require new thermal protection materials (both ablative and reusable) and novel thermal protection systems that are lightweight and durable with lower fabrication and operational costs than those currently available. Design, analysis, and optimization of such materials systems requires innovative applications of computational and experimental technology to account for complex high-temperature multiphase phenomena that occur in the external flow, on the heatshield surface, and inside the materials.

This subtopic solicits innovative concepts for novel lightweight and durable, rigid or flexible, reusable or ablative materials and systems having good thermal-shock resistance and temperature capabilities in the range from 800 to 3100 K. Possible reusable materials include refractory oxides, carbides, nitrides, borides and certain refractory metals. Mass efficient ablative materials using novel technologies are also sought. Possible material forms are fiber-fiber composites, fiber matrix composites, foams and felts, and various woven systems, as well as thin film, multilayer technologies. New minimum-weight, load-bearing or non-structural thermal protection systems using new components and processing methods are of interest, as are concepts for new and innovative lightweight solutions to cryogenic tank insulation for application to new reusable launch vehicles. Important proposal considerations are reduced weight, reduced fabrication or operational costs, improved performance, and improved robustness in adverse environmental conditions.

This subtopic also solicits new computational and experimental technologies for accurate measurement and modeling of mass and energy transport through Thermal Protection System (TPS) materials with detailed treatment of conductive, convective, and radiative heat transfer effects; for investigation of gas/solid interaction phenomena in reacting flow environments; and for rapid trajectory-based computational techniques. Technology applications of interest include the extension of computational and experimental methodologies to the phenomena listed above; diagnostics for high enthalpy and ballistic range test facilities; and experiments to validate computational methods and to measure relevant TPS material physical properties.

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