The presence in the space of micrometeoroids and orbital debris, particularly in the lower earth orbit, presents a continuous hazard to orbiting satellites, spacecrafts, and the international space station. Space debris includes all nonfunctional, man-made objects and fragments. As the population of debris continues to grow, the probability of collisions that could lead to potential damage will consequently increase. This work addresses a short review of the space debris "challenge" and reports on our recent results obtained on the application of self-healing composite materials on impacted composite structures used in space. Self healing materials were blends of microcapsules containing mainly various combinations of a 5-ethylidene-2-norbornene (5E2N) and dicyclopentadiene (DCPD) monomers, reacted with ruthenium Grubbs' catalyst. The self healing materials were then mixed with a resin epoxy and single-walled carbon nanotubes (SWNTs) using vacuum centrifuging technique. The obtained nanocomposites were infused into the layers of woven carbon fibers reinforced polymer (CFRP). The CFRP specimens were then subjected to hypervelocity impact conditions-prevailing in the space environment-using a home-made implosion-driven hypervelocity launcher. The different self-healing capabilities were determined and the SWNT contribution was discussed with respect to the experimental parameters.

A self-consistent thermodynamic model of the Mg-Mn, Al-Mn and Mg-Al-Mn systems has been developed. The major difference between this work and the already existing assessments of these systems is the application of the modified quasichemical model for the liquid phase in each system while most of the existing descriptions use the random mixing model. In the absence of key data for the Mg-Mn system, the calculated thermodynamic properties from the model have been found comparable to other similar systems and the estimated critical temperature of the Mg-Mn liquid miscibility gap using the available empirical equation has been found to be in acceptable agreement with the calculated value. A comparison between the current work and the most recent work on the Al-Mn system that uses the same model for the liquid phase reveals that better agreement with the experimental data with less number of model parameters has been achieved in the current work. Kohler symmetric extrapolation model with only one ternary interaction parameter has been used to calculate the ternary Mg-Al-Mn system. The thermodynamic description of the Mg-Al-Mn system has been verified by extensive comparison with the available experimental data from numerous independent experiments. The model can satisfactorily reproduce all the invariant points and the key phase diagram and thermodynamic features of the ternary as well as the constituent binary systems.