Magnesium is unique among the earth’s metals. The eighth most common element in the earth's crust and third most abundant element in seawater (which is an average of about 0.13% magnesium by weight), magnesium is the lightest of all known metals. It is non-toxic, non-magnetic, has high-impact strength and is resistant to denting. Its applications are numerous and varied: from automotive and aerospace manufacturing, to biodegradable medical devices and consumer products including computers and cell phones.
Now magnesium is being used as a primary component of a new, literal space-age material known as RPIA--Radiation and Particle Impact Absorber--that can withstand impacts from cosmic dust, micrometeorites and cosmic ionizing radiation.
RPIA is designed to meet the challenges of the next generation of space exploration, including long voyage space journeys to Mars, and is seen to be deployable as structural material for habitats there and on the Moon.
A crucial issue in space exploration is the space vehicle’s ability to endure harmful radiation, while at the same time ensuring safe passage for both people and electronics along its journey. Threats to that safety include ionizing radiation as well as high velocity particles, i.e. projectiles such as micrometeoroids and space dust. Thus, there is high demand for an effective absorber material against these outside forces for future space exploration activities. RPIA is just such an innovative and effective material.
RPIA is capable of absorbing ionizing space radiation and withstanding the impact of space dust. The proposed material, Syntactic Foam Multilayered Composite Material (Patents: US Patent pending; EU PCT/IB2016/057281, GB1521183.2), exhibits the following properties: low-density (0.8-1.2 g/cm3); vibro-resistant; cosmic ray absorptive; non-permeable for space dust; the ability to form complex shaped parts, and the ability to dissipate energy.
The syntactic foam material (named EMbloq) consists of a matrix and lightweight filler, hollow microspheres. The key aspects of the proposed material are: specific coating of microspheres, voids and spherical shape of the microspheres and layered micro- and macro-scale structure of composite. Unlike solid materials that are susceptible to cracks, this layered non-porous composite material will stop crack propagation. The voids operate as energetical traps. The multilayered structure of EMbloq is comprised of metal and polymer matrix syntactic foams, working to absorb energy of the projectile of the incoming cosmic particles. These are redirected into and trapped by the material instead of passing through it.
The matrix itself is at least two different layers: one with metal matrix and another with polymer matrix e.g. polypropylene. Each matrix layer works to protect from high and low energy ionizing radiation. The matrix material is composed of magnesium alloys, since magnesium possesses the best damping and vibration absorption ability of all lightweight materials and also has the lowest density of all industrial metals (Li and Na are very reactive to water and Be is very toxic). Another layer contains a high percentage of hydrogen atoms-- the material can be polypropylene, polyethylene or a derivative of polymer materials, reinforced by W-B composite micro rods.
The developer of EMbloq is experienced in developing and producing innovative lightweight absorber materials. The scope of previous work includes both ionizing and non-ionizing radiation protection, and impact absorption of kinetic energy. The developer’s team possesses high scientific knowledge and experience and is capable of simulating, synthesizing and testing the material, as well as modeling and testing space dust permeability by simulating cosmic dust particles at very high energy levels and velocities (400-500 m/sec). The testing is based on high-energy controlled explosions conducted with unique specialized custom-made equipment. The team is proficient and equipped in digital synthesis technologies, including computational modeling, which helps reduce material development time as well as time spent on testing and evaluation.
An example of the successful application of syntactic foam materials like EMbloq is indicated by the shift in recent years in the technology for hull design from solid-state metals to syntactic foams. For example, the United States Navy has successfully tested syntactic foam based materials in the hulls of Zumwalt-class ships. The Navy has subsequently placed a new order for dozens of ships in this configuration. The Navy's transition to Zumwalt class is based on the above-discussed characteristics of the material and also on its ability to withstand impact from directed energy weapons.
About Ceramic Hollow Microspheres
The material contains multilayered microspheres covered by micro- and nano- level coatings. The material may contain various types of cenospheres with different single or multi-layer metal coatings. The hollow microspheres are covered with radiation absorbing materials such as Pb (Lead), W (Tungsten), as high-energy radiation absorbers, and B (Boron), as a low energy radiation absorber. High-energy particles colliding with the materials containing Mg, W and Pb decrease the energy level to lower energy which then gets absorbed by the boron and hydrogen atoms in the next polymer layer. The hollowness of the spheres will work as an energy dissipator for the space dust particles. Waves meet multiple obstacles, change direction and the inbound energy is dissipated.
Multiple layers provide greater protection than a single piece of thick material (e.g. aluminum sheet). Multiple layers of the shield work to dissipate the overall mass and energy of the inbound projectile, so that it will pose no harm to the innermost 3 mm-thick aluminum wall, which is the inner pressure shell of the spacecraft. An additional benefit of the material is its very low density, whereas the very dense material contains (W, Pb).
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