Radiation Effects on Spacecraft Structural Materials

MRS Proceedings, 2006

ABSTRACTFuture manned space travel will go beyond the Lower Earth Orbit into deep space exploration and providing protection from space radiation is a major challenge. It is essential to study the effects of the space environment on materials to ensure safe and successful missions.This paper summarized the studies of two materials, in-site regolith composites and LTM 45 composites, for potential applications in space radiation environments. The effects of radiation on the mechanical and thermal properties of the composites were investigated. The radiation shielding effectiveness of in-situ composites and low temperature molding materials was analyzed. The work was part of the efforts in study and development of the multifunctiaonal materials for long-term radiation exposures to ensure effective radiation shielding and maintaining integrity of materials' mechanical and thermal properties for future space missions.

Journal of Composite Materials, 2013

Fiber-reinforced composites are of great interest to NASA for deep-space habitation missions due to the specific strength, modulus and potential radiation shielding properties. However, the durability of these materials on long-duration missions has not been evaluated. Few studies have been conducted on the radiation effects of fiber-reinforced composites in space and even fewer have been conducted with high-energy protons, which replicate portions of the deep-space radiation environment. Furthermore, previous studies of carbon fiber-reinforced composites focused on pure epoxy composites, and aerospace composites in use today include toughening agents to increase the toughness of the material. These toughening agents are typically either rubber particles or thermoplastics, known to be susceptible to ionizing radiation, and could affect the overall composite durability when exposed to high-energy protons. Thus, NASA has undertaken a study to understand the long-term radiation effects...

2003

Radiation hardness assurance for space applications needs to be based on extended radiation experiments. SCK·CEN, the Belgian Nuclear Research Center, is operating different gamma irradiation facilities, with gamma dose rates ranging from 10 rad/h up to 5 Mrad/h and with environmental control and on-line instrumentation capabilities. In addition, we have designed a vacuum-chamber module that can be adapted in our gamma irradiation facilities. The vacuum-system operates in the high-vacuum regime even in the presence of moderate outgassing conditions produced by polymer materials. The minimal design pressure guaranteed is 10-5 mbar but lower pressure can be expected in the case of inert and mineral materials.

Acta Astronautica, 2011

During the design process, the configuration of space vehicles and habitats changes frequently and the merits of design changes must be evaluated. Methods for rapidly assessing astronaut exposure are therefore required. Typically, approximations are made to simplify the geometry and speed up the evaluation of each design. In this work, the error associated with two common approximations used to simplify space radiation vehicle analyses, scaling into equivalent materials and material reordering, are investigated. Over thirty materials commonly found in spacesuits, vehicles, and human bodies are considered. Each material is placed in a material group (aluminum, polyethylene, or tissue), and the error associated with scaling and reordering was quantified for each material. Of the scaling methods investigated, range scaling is shown to be the superior method, especially for shields less than 30 g/cm 2 exposed to a solar particle event. More complicated, realistic slabs are examined to quantify the separate and combined effects of using equivalent materials and reordering. The error associated with material reordering is shown to be at least comparable to, if not greater than, the error associated with range scaling. In general, scaling and reordering errors were found to grow with the difference between the average nuclear charge of the actual material and average nuclear charge of the equivalent material. Based on this result, a different set of equivalent materials (titanium, aluminum, and tissue) are substituted for the commonly used aluminum, polyethylene, and tissue. The realistic cases are scaled and reordered using the new equivalent materials, and the reduced error is shown.

1991

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

9th Meeting of the Ionizing Radiation and Polymers Symposium (IRaP 2010), 2010

NASA is studying the effects of long-term space radiation on potential multifunctional composite materials for habitats to better determine their characteristics in harsh space environments. Two epoxy-matrix composite materials were selected for the study and were mounted in a test stand that simulated the biaxial stresses of a pressure vessel wall. The samples in the test stand were exposed to radiation at fast (0.1478 krad/s) and slow (0.0139 krad/s) dose rates, and the strain and temperature were recorded during the exposure. During a fast dose rate exposure, negative strain was recorded, decreasing with time, an indication of matrix shrinkage. Given previous radiation studies of polymers, this is expected to be a result of radiation-induced crosslinking in the epoxy matrix. However, with a slow dose rate, the materials exhibited a positive strain that increased with time, corresponding to stretching of the materials. This result is consistent with scission or degradation of the matrix occurring, possibly due to oxidative degradation.

MRS Proceedings, 2004

In this paper the ESA internal approach regarding the assessment of materials for inner solar system missions is presented. A main part of the work is devoted to the assessment of thermal control materials and space environmental testing at elevated temperature. As these materials are the most exposed it is important to understand how they will interact with the relevant space environment at elevated temperature. Driving parameters for materials degradation are discussed and ongoing testing efforts are described. An important input parameter for thermal models is the knowledge of the end of life values for the thermooptical properties as these determine the equilibrium temperatures. In certain cases end of life testing needs to be done when the uncertainty of extrapolation is too high.

IEEE Transactions on Plasma Science, 2008

Journal of Nuclear Materials, 1994

Blends containing 3 wt % low molecular weight polybutadiene ( P B ) in a polystyrene (PS) matrix were prepared via a precipitation technique that yielded spherical, submicron pools of PB. Tensile specimens made from these blends were then irradiated with high energy electrons in air a t dose levels from 0 to 70 Mrads. The blends, which previously showed high levels of toughness approaching that of high impact PS, lost all enhanced toughness when irradiated above 10 Mrads. Analysis of pure PS specimens irradiated over the dose range from 0 to 45 Mrads showed no appreciable dependence of mechanical behavior on dose level. Molecular weight studies of the polybutadiene demonstrated only a very modest increase in molecular weight in the dose range studied here; therefore, reduced mobility of the P B in the blends was not the reason for the dramatic drop in toughness with radiation dose. It was concluded that radiation-induced scission of the PS near the surface of the blends resulted in a significant local reduction in molecular weight. This degraded layer led to premature craze failure and hence a low level of toughness. It was demonstrated that the absence of oxygen during the irradiation process or the removal of the scissioned surface layer via mechanical abrasion resulted in a recovery of toughness. 0