Embrittlement of MISSE 5 Polymers After 13 Months of Space Exposure

by on 9 June 2015in Technology Development & Demonstration No comment

Understanding space environment induced degradation of spacecraft materials is essential when designing durable and stable spacecraft components. As a result of space radiation, debris impacts, atomic oxygen interaction, and thermal cycling, the outer surfaces of space materials degrade when exposed to low Earth orbit (LEO). The objective of this study was to measure the embrittlement of 37 thin film polymers after LEO space exposure. The polymers were flown aboard the International Space Station and exposed to the LEO space environment as part of the Materials International Space Station Experiment 5 (MISSE 5). The samples were flown in a nadir-facing position for 13 months and were exposed to thermal cycling along with low doses of atomic oxygen, direct solar radiation and omni-directional charged particle radiation. The samples were analyzed for space-induced embrittlement using a bend-test procedure in which the strain necessary to induce surface cracking was determined. Bend-testing was conducted using successively smaller mandrels to apply a surface strain to samples placed on a semi-suspended pliable platform. A pristine sample was also tested for each flight sample. Eighteen of the 37 flight samples experienced some degree of surface cracking during bend-testing, while none of the pristine samples experienced any degree of cracking. The results indicate that 49% of the MISSE 5 thin film polymers became embrittled in the space environment even though they were exposed to low doses (~2.75 krad (Si) dose through 127 μm Kapton) of ionizing radiation.

Related URLs:
http://dx.doi.org/10.1007/978-3-642-30229-9_35

Post-Flight Characterization of Samples for the MISSE-7 Spacesuit Fabric Exposure Experiment

by on 9 June 2015in Technology Development & Demonstration No comment

Six samples of pristine and dust-abraded outer layer spacesuit fabrics were included in the Materials International Space Station Experiment-7, in which they were exposed to the wake side low Earth orbit environment (LEO) on the International Space Station (ISS) for 18 months in order to determine whether abrasion by lunar dust increases radiation degradation. The fabric samples were characterized using optical microscopy, field emission scanning electron microscopy, and tensile testing before and after exposure on the ISS. Comparison of pre- and post-flight characterizations showed that wake side LEO environment darkened and reddened all six fabrics, increasing their integrated solar absorptance by 7 to 38 percent. There was a decrease in the ultimate tensile strength and elongation to failure of lunar dust abraded Apollo spacesuit fibers by a factor of four and increased the elastic modulus by a factor of two. The severity of the degradation of the fabric samples over this short exposure time demonstrates the necessity to find ways to prevent or mitigate radiation damage to spacesuits when planning extended missions to the Moon.

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BRADOS – Dose determination in the Russian Segment of the International Space Station

by on 9 June 2015in Technology Development & Demonstration No comment

In the frame of the joint experiment BRADOS-1, absorbed dose and average linear energy transfer were assessed by means of 7LiF:Mg,Ti (TLD-700) thermoluminescence detectors for different panels onboard the Russian Segment of the International Space Station in the timeframe between February and October 2001 (248 days). A technique is presented to correct the measured absorbed dose values for thermoluminescent efficiency in the radiation climate onboard the spacecraft. Average linear energy transfer is determined from the high-temperature thermoluminescence emission in the TLD-700 glowcurve and used as a parameter in the thermoluminescent-efficiency correction. Depending on the shielding distribution, the efficiency–corrected absorbed dose varies between 168(2) μGy/d in panel No. 318 (core block ceiling) and 249(4) μGy/d in panel No. 443 (starboard-side commander cabin). The experimental data are compared with model calculations using detailed shielding distributions and orbit parameters as input.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0273117706000251

Degradation of Spacesuit Fabrics on Low Earth Orbit

by on 9 June 2015in Technology Development & Demonstration No comment

Six samples of pristine and dust-abraded outer layer spacesuit fabrics were included in the Materials International Space Station Experiment-7, in which they were exposed to the wake-side low Earth orbit environment on the International Space Station (ISS) for 18 months in order to determine whether abrasion by lunar dust increases radiation degradation. The fabric samples were characterized using optical microscopy, optical spectroscopy, field emission scanning electron microscopy, atomic force microscopy, and tensile testing before and after exposure on the ISS. Comparison of pre- and post-flight characterizations showed that the environment darkened and reddened all six fabrics, increasing their integrated solar absorptance by 7 to 38 percent. There was a decrease in the ultimate tensile strength and elongation to failure of lunar dust abraded Apollo spacesuit fibers by a factor of four and an increase in the elastic modulus by a factor of two.

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Dose distribution in the Russian Segment of the International Space Station

by on 9 June 2015in Technology Development & Demonstration No comment

Absorbed dose and average linear energy transfer (LET) were assessed by means of (7)LiF:Mg,Ti (TLD-700) thermoluminescent (TL) detectors for different panels on-board the Russian Segment of the International Space Station in the timeframe between March and November 2002 (233 d). A technique is presented to correct the measured absorbed dose values for TL efficiency in the radiation climate on-board the spacecraft. Average LET is determined from the high-temperature TL emission in the TLD-700 glow curve and used as a parameter in the TL efficiency correction. Depending on the shielding distribution, the efficiency-corrected absorbed dose varies between 154 +/- 5 microGy d(-1) in panel no. 327 (core block ceiling) and 191 +/- 3 microGy d(-1) in panel no. 110 (core block central axis, floor). The experimental data are compared with the model calculations by using detailed shielding distributions and orbit parameters as inputs.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/16606660

Pre-Flight Characterization of Samples for the MISSE-7 Spacesuit Fabric Exposure Experiment

by on 9 June 2015in Technology Development & Demonstration No comment

A series of six sample spacesuit pressure garment assembly (PGA) fabric samples were prepared for the Materials International Space Station Experiment 7 (MISSE-7) flight experiment to test the effects of damage by lunar dust on the susceptibility of the fabrics to radiation damage. These included pristine Apollo-era fluorinated ethylene-propylene (FEP) fabric, Apollo-era FEP fabric that had been abraded with JSC-1A lunar simulant, and a piece of Alan Bean s Apollo 12 PGA sectioned from near the left knee. Also included was a sample of pristine orthofabric, and orthofabric that had been abraded to two different levels with JSC-1A. The samples were characterized using optical microscopy, field emission scanning electron microscopy, and atomic force microscopy. Two sets of six samples were then loaded in space environment exposure hardware, one of which was stored as control samples. The other set was affixed to the MISSE-7 experiment package, and will be mounted on the International Space Station, and exposed to the wake-side low Earth orbit environment. It will be retrieved after an exposure of approximately 12 months, and returned for post flight analysis.

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Convolution of TLD and SSNTD measurements during the BRADOS-1 experiment onboard ISS (2001)

by on 9 June 2015in Technology Development & Demonstration No comment

The Russian BRADOS experiment onboard the International Space Station (ISS) was aimed at developing methods in radiation dosimetry and radiobiology to improve the reliability of risk estimates for the radiation environment in low-Earth orbit. Experimental data from thermoluminescence detectors (TLDs) and solid state nuclear track detectors (SSNTDs) gathered during the BRADOS-1 (24 February–31 October 2001) mission are reviewed and convolved to obtain absorbed dose and dose equivalent from primary and secondary cosmic-ray particles. Absorbed dose rates in the ISS Russian Segment (Zvezda) ranged from 208 ± 14 to 275 ± 14 μ Gy d – 1 . Dose equivalent rates were determined to range from 438 ± 29 to 536 ± 32 μ Sv d – 1 , indicating a quality factor between 1.95 ± 0.15 and 2.11 ± 0.20 . The contribution of densely ionizing particles ( LET ⩾ 10 keV μ m – 1 ) to dose equivalent made up between 54% and 64%.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S1350448708002539

Component Repair Experiment-1: An Experiment Evaluating Electronic Component-Level Repair During Spaceflight

by on 9 June 2015in Technology Development & Demonstration No comment

The Component Repair Experiment-1 (CRE-1) examines the capability for astronauts to perform electronics repair tasks in space. The goal is to determine the current capabilities and limits for the crew, and to make recommendations to improve and expand the range of work that astronauts may perform. CRE-1 provided two-layer, functional circuit boards and replacement components, a small tool kit, written and video training materials, and 1 hr of hands on training for the crew slated to perform the experiment approximately 7 months prior to the mission. Astronauts Michael Fincke and Sandra Magnus performed the work aboard the International Space Station (ISS) in February and March 2009. The astronauts were able to remove and replace components successfully, demonstrating the feasibility of performing component-level electronics repairs within a spacecraft. Several unsuccessful tasks demonstrated areas in need of improvement. These include improved and longer training prior to a mission, an improved soldering iron with a higher operating temperature and steady power source, video training and practice boards for refresher work or practice before a repair, and improved and varied hand tools and containment system.

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MOSFET dosimetry mission inside the ISS as part of the Matroshka-R experiment

by on 9 June 2015in Technology Development & Demonstration No comment

Radiation measurements of surface and deep organ doses were performed aboard the International Space Station, for the period of January 2006 to April 2007, using a MOSFET dosimetry system combined with the Matroshka-R spherical phantom. The averaged internal and surface dose rates are found to be 0.19 and 0.29 mGy d(-1), respectively. The levels of radiation dose to blood-forming organs (BFO) and to surface organs are compared with recommended safe limits. The maximum measured BFO dose has an average dose rate of 0.23 mGy d(-1) (84 mGy y(-1)), corresponding to 44 % of the recommended annual limit of 0.5 Sv, for a space radiation quality factor of 2.6. The annual surface dose is found to be higher at 126 mGy, corresponding to 16 % of the eye dose limit and to 11 % of the skin dose limit. Doses calculated using the Spenvis software showed deviations of up to 37 % from measurements.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/19933696

System for detecting and estimating concentrations of gas or liquid analytes

by on 9 June 2015in Technology Development & Demonstration No comment

A sensor system for detecting and estimating concentrations of various gas or liquid analytes. In an embodiment, the resistances of a set of sensors are measured to provide a set of responses over time where the resistances are indicative of gas or liquid sorption, depending upon the sensors. A concentration vector for the analytes is estimated by satisfying a criterion of goodness using the set of responses. Other embodiments are described and claimed.

Related URLs:
https://www.google.com/patents/US8024133