The mesh reflector is the only type of large, in-space deployable antenna that has successfully flown in space. However, state-of-the-art large deployable mesh antenna systems are RF-frequency-limited by both global shape accuracy and local surface quality. The limitations of mesh reflectors stem from two factors. First, at higher frequencies, the porosity and surface roughness of the mesh results in loss and scattering of the signal. Second, the mesh material does not have any bending stiffness and thus cannot be formed into true parabolic (or other desired) shapes.
To advance the deployable reflector technology at high RF frequencies from the current state-of-the-art, significant improvements need to be made in three major aspects: a high-stability and highprecision deployable truss; a continuously curved RF reflecting surface (the function of the surface as well as its first derivative are both continuous); and the RF reflecting surface should be made of a continuous material. To meet these three requirements, the Membrane Shell Reflector Segment (MSRS) antenna was developed.
A MSRS antenna is composed of a deployable tetrahedral truss that supports a set of MSRSs to form a high-definition, smooth, and continuous surface. This high radio-frequency (RF) deployable reflector is implemented by leveraging and integrating several recently developed material technologies: shape memory polymer (SMP) composite material; high-precision MSRS casting process; near-zero coefficient of thermal expansion (CTE) membrane material; and polyvinylidene fluoride (PVDF) electro-active membrane. This reflector technology can potentially offer almost one order of magnitude higher precision than current state-of-the-art reflectors, and can provide very complex reflector shapes.
The structural part of this MSRS antenna is a tetrahedral truss that provides rigidity and integrity for the reflector. Tetrahedral trusses offer much higher precision than tensioning cable trusses that are employed by all current state-ofthe- art mesh reflectors. However, it is extremely difficult to package a tetrahedral truss by using traditional deployment mechanisms. The unique characteristic of the SMP composite makes it possible to package and deploy the whole reflector. The fundamental requirement on a high RF reflector, high precision, will naturally be met by the intrinsic accuracy characteristic of the tetrahedral configuration. The high-definition RF reflective surface is composed of a number of MSRSs made of either near-zero CTE Novastrat or PVDF membrane. The thickness and curvature of each MSRS provide sufficient shell stiffness for it to be supported by the tetrahedral truss at three points.
This work was done by Houfei Fang and Eastwood Im of Caltech, John Lin of ILC Dover LP, and Jim Moore of NeXolve Corporation for NASA’s Jet Propulsion Laboratory.
This Brief includes a Technical Support Package (TSP).
Membrane Shell Reflector Segment Antenna
(reference NPO-48317) is currently available for download from the TSP library.
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Overview
The document discusses the development of a new in-space deployable reflector technology, specifically the Membrane Shell Reflector Segment Antenna, sponsored by NASA's Earth Science Technology Office (ESTO) Advanced Concepts Team (ACT). This technology aims to support future missions that require large antennas operating at high radio frequencies, which are crucial for various scientific applications.
Key missions that would benefit from this technology include the Aerosol/Cloud/Ecosystem (ACE) mission, the NEXRAD In Space (NIS) initiative, and the Global Atmospheric Composition Mission (GACM). The deployable reflector technology is designed to significantly reduce launch costs, making it a valuable asset for missions like the Precipitation and All-weather Temperature and Humidity (PATH) mission.
To enhance the current state-of-the-art in deployable reflector technology, the document identifies three major areas for improvement:
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High Stability and Precision Deployable Truss: This component is essential for maintaining the structural integrity and operational precision of the reflector once deployed in space.
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Continuously Curved RF Reflecting Surface: The design requires that both the surface and its first derivative be continuous, ensuring optimal performance in reflecting radio frequencies.
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Continuous Material for the RF Reflector: The use of a continuous material is crucial for achieving the desired lightweight and high-precision characteristics necessary for space applications.
The document also acknowledges the collaborative efforts of various researchers and institutions, including the Jet Propulsion Laboratory (JPL) and other contributors to the field of aerospace technology. It highlights the unique characteristics of the materials being developed, which are aimed at creating ultra-lightweight, large, and high-precision space structures.
In conclusion, the Membrane Shell Reflector Segment Antenna represents a significant advancement in deployable reflector technology, with the potential to enhance scientific research capabilities in space while also providing cost-effective solutions for future missions. The document serves as a technical support package, providing insights into the ongoing research and development efforts in this area, and invites further inquiries for those interested in the innovative technology being explored.
