DARPA and NASA have recognized ultra-lightweight shape memory Rigidizable Inflatable (RI) structures as an enabling technology for future space and interplanetary missions requiring large space systems. There are many benefits of using advanced Shape Memory Polymer (SMP) materials in large space structures such as high compaction ratio, increased design flexibility, and reduced complexity. These benefits are similar to the benefits of pure inflatable applications, but without the disadvantages of high coefficient of thermal expansion (CTE) and the need of constant make up gas for maintaining inflation. Furthermore, it has higher structural stiffness and higher accuracy as compared to pure inflatable applications. To date, ILC Dover has developed and continued to mature and test several types of SMP material systems. These material systems include single glass transition temperature (T g) systems with customizable T g ranging from 0°°°°C to 120°°°°C and dual T g systems that have an initial low T g and can be triggered on command by heat, radiation (UV, etc.) or chemical exposure to a higher T g. It is important for the space community to understand the major differences the SMP technologies bring to large space systems. This paper will discuss current SMP materials and then examine the implication of SMP technology as it relates to large space systems and how it can enable future missions.

A novel mission concept, namely NEXRAD in Space, has been developed for detailed monitoring of hurricanes, cyclones, and severe storms from a geostationary orbit. This mission concept requires a space deployable 35-m diameter reflector that operates at 35-GHz with a surface figure accuracy requirement of 0.21 mm RMS. This reflector is well beyond the current state-of-the-art. To implement this mission concept, several potential technologies associated with large, lightweight, spaceborne reflectors have been investigated by this study. These spaceborne reflector technologies include mesh reflector technology, inflatable membrane reflector technology and Shape Memory Polymer reflector technology. Nomenclature T d= deformation temperature T g = glass transition temperature T r = recovery temperature T s = storage temperature I. Introductionnder NASA's Earth Science Technology Program, a novel mission concept has been developed for detailed monitoring of hurricanes, cyclones, and severe storms from a geostationary orbit 1,2 . This mission concept is named as "NEXRAD in Space (NIS)". NIS is designed to operate in the geostationary orbit at an altitude of 36,000 km. It would provide Ka-band (35 GHz) radar and line-of-sight Doppler velocity profiles over a circular Earth region of approximately 5200 km in diameter with a 12-km horizontal resolution, and a minimum detectable signal of 5 dBZ. The NIS radar achieves its superb sampling capabilities by use of a 35-m diameter in-space deployable spherical reflector. The antenna has two transmit-receive array feeds that create a three-dimensional image of both reflectivity and Doppler velocity inside and surrounding the storm systems approximately every 60 minutes. Both the reflector and the spacecraft will remain stationary as the feeds perform spiral scans to 4 o to cover a 5200-km diameter circular area on the Earth's surface. U

Ge content and thickness variations of epitaxial Si1-xGex layers on Si(100) were nondestructively measured using a long-focal-length, polychromator-based, multiwavelength micro-Raman spectroscopy system, which is designed for noncontact, in-line process and material property monitoring. The Ge content and thickness variations measured using the Raman system showed good agreement with results from both high-resolution X-ray diffraction (HRXRD) and secondary ion mass spectroscopy (SIMS) analysis. The nondestructive depth profiling capability of the multiwavelength Raman spectroscopy was verified on Si1-xGex layers on Si(100) intentionally profiled with a Ge content gradient.

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