Wanda C. Peters

Variable Emittance Materials Based on Conducting Polymers for Spacecraft Thermal Control

Ashwin‐Ushas has developed a unique, patented Variable Emittance technology based on the infrared (IR) electrochromism of unique Conducting Polymers. This has features of: very thin ( 104 cycles; low power consumption ( 104 cycles; low power consumption (< 40 μW/ cm2); and most importantly, space environment durability (space vacuum and −40 °C to + 75 °C, Solar Wind, gamma radiation to 7.6 Mrad). A demonstrator spaceflight is tentatively planned on NASA‐Goddard’s ST5 mission. This paper describes the features and current status of the technology, including results from the most recent tests. It is shown that the technology is the most promising among proposed new Variable Emittance technologies, and possibly one of the only technologies applicable to microspacecraft, besides also being applicable to large spacecraft, space bas...

Desert Research and Technology Studies Exposure of Lotus Coated Electrodynamic Shield samples

The Lotus dust mitigation coating and the electrodynamic shield (EDS) are two new technologies currently being developed by NASA as countermeasures for addressing dust accumulation for long-duration human space exploration. These combined technologies were chosen by the Habitation Demonstration Unit (HDU) program for desert dust exposure at the Desert Research and Technologies Studies (D-RaTS) test site in Arizona. Characterization of these samples was performed prior to, during and post D-RaTS exposure.

Development of molecular adsorber coatings

As mission, satellite, and instrument performance requirements become more advanced, the need to control adverse onorbit molecular contamination is more critical. Outgassed materials within the spacecraft have the potential to degrade performance of optical surfaces, thermal control surfaces, solar arrays, electronics, and detectors. One method for addressing the outgassing of materials is the use of molecular adsorbers. On Goddard Space Flight Center missions such as Hubble Space Telescope (HST), Tropical Rainfall Measuring Mission (TRMM), and SWIFT, Zeolite-coated cordierite molecular adsorbers were successfully used to collect and retain outgassed molecular effluent emanating from spacecraft materials, protecting critical contamination sensitive surfaces. However, the major drawbacks of these puck type adsorbers are weight, size, and mounting hardware requirements, making them difficult to incorporate into spacecraft designs. To address these concerns, a novel molecular adsorber coating was developed to alleviate the size and weight issues while providing a configuration that more projects can utilize, particularly contamination sensitive instruments. This successful sprayable molecular adsorber coating system demonstrated five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was refined and a procedure for spray application was developed. Samples were spray coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. The tested formulation passes coating adhesion and vacuum thermal cycling tests between +140 and -115C. Thermal radiative properties are very promising. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate coatings.

EFFECTS OF MANUFACTURING AND DEPLOYMENT ON THIN FILMS FOR THE NGST SUNSHADE

The Next Generation Space Telescope (NGST) is being developed as an advanced astronomical observatory. The NGST proposes to utilize several thin film membrane layers to create a shield for protection of the telescope from solar thermal energy and stray light, The shield will take the form of a polygon, approximately 15 x 30 m, with individual membrane layers positioned so that they do not come in contact with one another. The membrane shield will be deployed and supported by a series of booms, which will be packed into a small volume for launch. Finally, the shield will be deployed on orbit. Several film materials are being considered for the membrane shield, including CPI, Kapton E, Kapton RN, and Upilex. Each of these polyimide materials was tested to determine their durability over the 10-year mission. New facets of materials testing have been introduced in this study to develop performance data with greater realism to actual use, particularly that of degradation from packing, launch and deployment processing. Materials were exposed to handling that simulated the life of the materials from manufacture through deployment with standardized fixtures and then exposed to a simulated, L2, 10-year radiation environment. Mechanical and thermal radiative properties were measured before and after each phase of testing. This paper summarizes the program and test results.

Weathering of Thermal Control Coatings

Spacecraft radiators reject heat to their surroundings. Radiators can be deployable or mounted on the body of the spacecraft. NASAs Crew Exploration Vehicle is to use body mounted radiators. Coatings play an important role in heat rejection. The coatings provide the radiator surface with the desired optical properties of low solar absorptance and high infrared emittance. These specialized surfaces are applied to the radiator panel in a number of ways, including conventional spraying, plasma spraying, or as an applique. Not specifically designed for a weathering environment, little is known about the durability of conventional paints, coatings, and appliques upon exposure to weathering and subsequent exposure to solar wind and ultraviolet radiation exposure. In addition to maintaining their desired optical properties, the coatings must also continue to adhere to the underlying radiator panel. This is a challenge, as new composite radiator panels are being considered as replacements for the aluminum panels used previously. Various thermal control paints, coatings, and appliques were applied to aluminum and isocyanate ester composite coupons and were exposed for 30 days at the Atmospheric Exposure Site of the Kennedy Space Center s Beach Corrosion Facility for the purpose of identifying their durability to weathering. Selected coupons were subsequently exposed to simulated solar wind and vacuum ultraviolet radiation to identify the effect of a simulated space environment on the as-weathered surfaces. Optical properties and adhesion testing were used to document the durability of the paints and coatings. The purpose of this paper is to present the results of the weathering testing and to summarize the durability of several thermal control paints, coatings, and appliques to weathering and postweathering environments.

Evaluation of Coatings and Materials for Future Radiators

Radiators are used to reject energy from space vehicles through radiant heat transfer. They are typically the largest component in a vehicles thermal control system and can have a large impact on the vehicle design and operation. NASA s current vision for exploration dictates that radiators for a Crew Exploration Vehicle (CEV), a Lunar Surface Access Module (LSAM), and a lunar base will need to be developed. These applications present new challenges when compared to previous radiators on the Space Shuttle and International Space Station (ISS). In addition, many technological advances have been made that could positively impact future radiator design. This paper outlines new requirements for future radiators and documents a trade study performed to select the some promising technologies for further evaluation. The technologies include K1100 based carbon composites for the radiator surface as well as Optical Solar Reflectors (OSRs), a lithium based white paint, and electrochromic thin films for optical coatings. Coupons were made using these materials and tests were performed to characterize their performance. Testing included evaluating structural and thermal properties of the carbon composites, thermal cycling, launch pad weather simulation, and exposure to solar wind, and Ultraviolet (UV) radiation.