Development of carbon nanotube-based composite for spacecraft components

Over the last decade, there have been significant advancements in the material synthesis and processing aspects of the carbon nanotube (CNT) technology, and the basic understanding of its multifunctional properties. Lockheed Martin Space Systems has been evaluating CNTs, vapor-grown carbon nanofibers (VGCF), and CNT sheets, grapheme-based nanocomposites, from different sources for incorporating them into composite components of spacecraft structures. This paper describes the use of CNT-based composite components such as tubes and sandwich panels on the Juno spacecraft. In the last two decades, several composite-based solutions have also been investigated to minimize the Materials and Processing steps and introduce electrical functionality to satisfy electrostatic dissipation (ESD), grounding, and shielding effectiveness (SE) requirements for spacecraft structures. A few of these concepts have had very limited success, compared to the highly-effective approaches such as an outer surface of thin aluminum (Al) foil or electrically conductive coating. In this investigation, several viable nanocomposite-based approaches were evaluated for the spacecraft composite structure applications. A few of these approaches offered the design solution satisfying the ESD and outgassing requirements, and provided good thermal conductivity. More specifically, the dry CNT sheets were incorporated as the outermost ply on the conventional composite layup, which were processed using state-of-the-art (SOA) autoclave process for fabricating the tube elements for the spacecraft. These tubes exhibited excellent surface finish, enhanced surface conductivity, and improved stiffness, compared to the state-of-the-art composite tubes. Building upon this technology development effort, a few flight-quality tubes and a flight-quality sandwich panel were successfully fabricated and qualified for the Juno spacecraft. Successful technology insertion of a CNT sheet for ESD protection on the Juno spacecra- t will pave the way for the extensive use of CNT-based composite structures on future spacecrafts, thus benefiting from CNT´s multifunctional attributes such as electromagnetic shielding effectiveness, thermal and electrical conductivity, and enhanced fracture toughness and interlaminar properties.