For long duration solar sail missions, the sail membrane needs to survive large temperature fluctuations, ultraviolet (UV) and ionizing radiation, ultrahigh vacuum, and micrometeoroid impacts. Since the degradation of the sail... [ view full abstract ]
For long duration solar sail missions, the sail membrane needs to survive large temperature fluctuations, ultraviolet (UV) and ionizing radiation, ultrahigh vacuum, and micrometeoroid impacts. Since the degradation of the sail material affects operational lifetime, a quantitative study of space environment effects on the solar sail can provide design guidelines to increase the reliability of solar sails, resulting in reduced risk in the acceptance of this type of propulsion system. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success.
In this study, we simulated the partial effect of space environment of ionizing radiation on thermal, optical, and mechanical properties of a commercial off the shelf (COTS) polyester solar sail membrane to assess the degradation mechanisms on a feasible solar sail. The solar sail membrane was fabricated from polyethylene naphthalate (PEN, 2 μm thick) film by metallization with aluminum (100 nm thick) for the reflective side and chrome (15 nm thick) for the emission side. To evaluate the effect of ionizing radiation, the solar sail membrane was exposed to high energy electrons (about 70 keV and 10 nA/cm2). The thermal, optical and mechanical properties were characterized before and after exposure to the electrons. After about 8.3 Grad dose, the tensile modulus, tensile strength, and failure strain of the sail membrane decreased by about 20 ~ 95%. However, it did not show any significant change in optical properties of solar absorbance and thermal emittance of the reflective side (aluminum layer). The electron radiation induced molecular degradation was observed using various experimental techniques such as Fourier transform-infrared (FT-IR) spectroscopy, dynamic mechanical analysis (DMA) and electron paramagnetic resonance (EPR) spectroscopy. Also discussed are the effects on mechanical properties of puncture, simulating micrometeoroid impact of the sail membrane, as well as thermal effects on PEN, in comparison with other candidate solar sail membranes.
Testing / Mitigation , Radiation , Space Weather