Lightweight, deployable antennas for a variety of outer-space and terrestrial applications would be designed and fabricated according to the concept of cold hibernated elastic memory (CHEM) structures, according to a proposal. Mechanically deployable antennas now in use are heavy, complex, and unreliable, and they utilize packaging volume inefficiently. The proposed CHEM antenna structures would be simple and would deploy themselves without need for any mechanisms and, therefore, would be more reliable. The proposed CHEM antenna structures would also weigh less, could be packaged in smaller volumes, and would cost less, relative to mechanically deployable antennas.
The CHEM concept was described in two prior NASA Tech Briefs articles: "Cold Hibernated Elastic Memory (CHEM) Expandable Structures" (NPO-20394), Vol. 23, No. 2 (February 1999), page 56; and "Solar Heating for Deployment of Foam Structures" (NPO-20961), Vol. 25, No. 10 (October 2001), page 36. To recapitulate from the cited prior articles: The CHEM concept is one of utilizing open-cell foams of shape-memory polymers (SMPs) to make lightweight, reliable, simple, and inexpensive structures that can be alternately (1) compressed and stowed compactly or (2) expanded, then rigidified for use. A CHEM structure is fabricated at full size from a block of SMP foam in its glassy state [at a temperature below the glass-transition temperature (Tg) of the SMP]. The structure is heated to the rubbery state of the SMP (that is, to a temperature above Tg) and compacted to a small volume. After compaction, the structure is cooled to the glassy state of the SMP. The compacting force can then be released and the structure remains compact as long as the temperature is kept below Tg. Upon subsequent heating of the structure above Tg, the simultaneous elastic recovery of the foam and its shape-memory effect cause the structure to expand to its original size and shape. Once thus deployed, the structure can be rigidified by cooling below Tg. Once deployed and rigidified, the structure could be heated and recompacted. In principle, there should be no limit on the achievable number of compaction/deployment/rigidification cycles.
Thus far, several different designs of a 3.5-m-long CHEM conical corrugated horn antenna have been analyzed (see figure). A small CHEM structural antenna model was fabricated and a thin, electrically conductive layer of aluminum was deposited on the inner surface of the model. This structural model was then subjected to the compaction and deployment treatments described above to demonstrate the feasibility of a CHEM corrugated horn antenna.
This work was done by Witold Sokolowski, Steven Levin, and Peter Rand of Innovative Technology for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Electronics/ Computers category. NPO-30272
This Brief includes a Technical Support Package (TSP).
Lightweight, Self-Deploying Foam Antenna Structures
(reference NPO-30272) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory, focusing on Lightweight, Self-Deploying Foam Antenna Structures, specifically highlighting the Cold Hibernated Elastic Memory (CHEM) technology. This innovative approach addresses the critical need for ultra-light, deployable systems in various aerospace missions, including the proposed JASSI (Juniper Deep Atmospheric Sounder and Synchrotron Imager) deployable horn antenna.
CHEM technology utilizes shape memory polymers in open cellular foam structures, which undergo a specific processing cycle. Initially, the foam is fabricated in a glassy state below its glass transition temperature (Tg). It is then warmed above Tg to allow for compressed stowing, followed by cooling below Tg to induce a hibernation state. When heated above Tg, the foam returns to its original shape, and upon cooling below Tg, it achieves rigidization. This process allows for a high full/stowed volume ratio, making it efficient for storage and deployment.
The document details the development of various designs for a 3.5-meter long conical corrugated horn antenna, with structural and dynamic analyses performed on each configuration. A small CHEM structural antenna model was fabricated, demonstrating the feasibility of this technology. The model successfully underwent the CHEM processing cycles, showcasing its ability to self-deploy, restore its original shape, and become rigid.
The advantages of CHEM foam antennas over traditional mechanically deployable antennas are significant. They are lighter, simpler, and more reliable, addressing issues of complexity and inefficiency in packaging volume associated with current designs. The CHEM technology promises to revolutionize antenna structures by providing a self-deployable solution that is cost-effective and efficient.
The document also emphasizes the broader implications of this technology, suggesting potential applications beyond aerospace, given its versatility and effectiveness. For further information, the document references additional resources available through NASA's Scientific and Technical Information (STI) Program Office, encouraging exploration of the wider technological, scientific, and commercial applications of these developments.
In summary, the Technical Support Package presents a compelling case for the CHEM technology as a transformative solution for lightweight, self-deploying antenna structures, with significant implications for future aerospace missions and beyond.
