Ladder polymers for use as high temperature stable resins or coatings

An object of the invention is to synthesize a new class of ladder and partial ladder polymers. In accordance with the invention, the new class of ladder and partial ladder polymers are synthesized by polymerizing a bis-dienophile with a bis-diene. Another object of the invention is to provide a fabricated, electrically conducting, void free composite comprising the new class of the ladder and partial ladder polymers described above. The novelty of the invention relates to a new class of ladder and partial ladder polymers and a process for synthesizing these polymers. These polymers are soluble in common organic solvents and are characterized with a unique dehydration property at temperatures of 300 to 400 C to provide thermo-oxidatively stable pentiptycene units along the polymeric backbone. These polymers are further characterized with high softening points and good thermo-oxidative stability properties. Thus these polymers have potential as processable, matrix resins for high temperature composite applications

Light shield and cooling apparatus

A light shield and cooling apparatus was developed for a high intensity ultraviolet lamp including water and high pressure air for cooling and additional apparatus for shielding the light and suppressing the high pressure air noise

High-temperature polymer matrix composites

Polymers research at the NASA Lewis Research Center has produced high-temperature, easily processable resin systems, such as PMR-15. In addition, the Polymers Branch has investigated ways to improve the mechanical properties of polymers and the microcracking resistance of polymer matrix composites in response to industry need for new and improved aeropropulsion materials. Current and future research in the Polymers Branch is aimed at advancing the upper use temperature of polymer matrix composites to 700 F and beyond by developing new resins, by examining the use of fiber reinforcements other than graphite, and by developing coatings for polymer matrix composites to increase their oxidation resistance

Root Cause Classification of Breakup Events 1961-2018

This paper uses the updated NASA History of On-Orbit Satellite Fragmentations 15th Edition, to examine and categorize the root cause of historical breakup events to the greatest degree possible. Classes of debris progenitors have evolved, as many classes of Cold War-era spacecraft are now extinct, only to be replaced by new classes of payloads and rocket bodies statistically likely to experience debris-producing events. The efficacy of international debris mitigation implementation and root cause/fault tree analyses and lessons learned is examined in relation to the breakup of satellite classes or specific events. In select cases, the remaining on-orbit inventory of specific classes is identified in the context of possible future events. The environmental impact of these specific classes is examined and compared to nominal space environment projections. When appropriate, recommendations for debris remediation are made for specific satellite classes

A critical analysis of the Grad approximation for closing out the magnetohydrodynamic equations for plasmas

Error analysis on moment distribution functions of magnetohydrodynamic plasma equation

A semiempirical collision model for plasmas

Semiempirical collision model for plasma

Orbital Debris Quarterly News

No abstract availabl

Addition polymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and Bis-dienes: Processable resins for high temperature application

1,4,5,8-Tetrahydro-1,4;5,8-diepoxyanthracene reacts with various anthracene endcapped polyimide oligomers to form Diels-Alder cycloaddition copolymers. The polymers are soluble in common organic solvents, and have molecular weights of approximately 21,000 to 32,000. Interestingly, these resins appear to be more stable in air then in nitrogen. This is shown to be due to a unique dehydration (loss of water ranges from 2 to 5 percent) at temperatures of 390 to 400 C to give thermo-oxidatively stable pentiptycene units along the polymer backbone. Because of their high softening points and good thermo-oxidative stability, the polymers have potential as processible, matrix resins for high temperature composite applications

Addition polymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and Bis-dienes. 2: Evidence for thermal dehydration occurring in the cure process

Diels-Alder cycloaddition copolymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and anthracene end-capped polyimide oligomers appear, by thermogravimetric analysis (TGA), to undergo dehydration at elevated temperatures. This would produce thermally stable pentiptycene units along the polymer backbone, and render the polymers incapable of unzipping through a retro-Diels-Alder pathway. High resolution solid 13C nuclear magnetic resonance (NMR) of one formulation of the polymer system before and after heating at elevated temperatures, shows this to indeed be the case. NMR spectra of solid samples of the polymer before and after heating correlated well with those of the parent pentiptycene model compound before and after acid-catalyzed dehydration. Isothermal gravimetric analyses and viscosities of the polymer before and after heat treatment support dehydration as a mechanism for the cure reaction

An 82 Inclination Debris Cloud Revealed by Radar

The statistical debris measurement campaigns conducted by the Haystack Ultrawideband Satellite Imaging Radar on behalf of the NASA Orbital Debris Program Office are used to characterize the long-term behavior of the small, low Earth orbit (LEO) orbital debris environment. Recent analyses have revealed the presence of a persistent LEO small debris cloud, which has no accompanying large component, cataloged by the U.S. Space Surveillance Network. This cloud, at an inclination of approximately 82 and below 1200 km in altitude does, however, correspond to the heavily trafficked region of space that has suffered several known, accidental collisions, e.g., Cosmos 1934 and Cosmos 2251. In this paper, we describe the observed cloud and model it using the NASA Standard Satellite Breakup Model. Key features of the cloud model, including source attribution and debris mass constraints, are presented to enable further observations and characterization