1:45 PM - SF04.01.03
Multifunctional Polyethylene Based Composite Material for Space Applications
Lembit Sihver1,2,3,Cody Alison Paige4,Svetlana Boriskina4
Cosmic Shielding Corporation1,Technische Universität Wien2,Chalmers University of Technology3,Massachusetts Institute of Technology4
To enable the planned rapid growth of both government and private operators in space, including satellites, space tourism and manned missions to the Moon and to Mars, a realistic and holistic approach to radiation risk reduction is needed. In deep space, ionizing radiation from Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) from the sun pose a critical threat to both humans and electronic equipment. GCRs provide a chronic, slowly varying, highly energetic background source of High-Z high-Energy (HZE) particles, while the Sun's activity varies with an 11-year cycle during which the Sun produces Solar Wind (SW) at varying intensities and unpredictable bursts of Solar Particle Events (SPEs). SPEs can be a nightmare for the astronauts and cause acute radiation damage, while GCRs can cause long term damage including cancer, cataracts, central nervous system and cardiovascular system damage, fibrosis, neurodegeneration, digestive diseases, and immunological, endocrine, hereditary effects, and cognitive impairment.
The GCRs and SPEs can also cause degradation of micro-electronics, optical components and solar cells. Spacecraft electronics are especially susceptible to radiation effects that emerge from interactions with HZE particles, but highly energetic gamma photons, neutrons and protons can also damage electrical components. Since the exposure of humans and electronics to GCRs and SPEs in deep space, and on the surface of the Moon and Mars, will cause huge radiation risks, it is very important to apply the best possible protection for both humans and electronics. Currently, the only proven and practical countermeasure to reduce the exposure to GCRs and SEPs is passive shielding. It is well known that low atomic number (Z) materials are most effective for shielding in space, and liquid hydrogen has the maximum theoretical performance as a shielding material. Hydrogen is not, however, a practical shielding material, being a low temperature liquid associated with practical handling problems and explosion risks. Hydrogen concentrated in specially engineered and doped polyethylene based composites, however, is ideal for stopping primary cosmic and solar radiation, as well as secondary neutrons created when the primary particles are impinging on the spacecraft. Low atomic number (Z) materials also produce less electron-positron pairs and Bremsstrahlung than materials with higher Z, such as aluminum alloys, which are used in conventional satellites and spacecraft.
Additives can improve the flame retardancy and inhibit the release of toxic gases as well as absorption of neutrons created when HZE particles hit the shielding and other components of the spacecraft. The material can also be produced for protection against micrometeoroids, debris, extreme temperature variations and protection against atomic oxygen present at low Earth orbit (LEO).
We will present the basic physics, as well as simulated and experimental properties of a 3D printed specially engineered and doped polyethylene based composite, which can be manufactured with different degrees of flexibility, stiffness and thermal conductivity. We have demonstrated that hierarchical engineering of PE materials and composites enables drastic modification of their light absorption, thermal emission, heat, and moisture transport properties [1,2]. The material can therefore be used for many different applications, ranging from radiation shielding of components inside a satellite or spacecraft, to a construction material for satellites, to spacecraft and space habitats, and components in intravehicular (IVA) and extravehicular (EVA) spacesuits.
1. S.V. Boriskina, An ode to polyethylene, MRS Energy & Sustainability, 6, E14, 2019.
2. M. Alberghini, et al, Sustainable polyethylene fabrics with engineered moisture transport for passive cooling, Nature Sustainability, 2021, doi: 10.1038/s41893-021-00688-5.