1.1. Types of radiation3. External structure 3.1. Radiation shieldingBecause Syzygy will be the future home of 10.000 people we have to make sure we will provide the best and most efficient shielding against nocive ionizing radiation.
The settlemet will be situated in Low Earth Orbit (LEO) at an altittude between 400 and 500 km, area where the geomagnetic field deflects a significant quantity of radiation. In space there are four different types of ionizing radiation:? Trapped radiation (trapped by earth’s magnetic field)? Solar energetic particles (SEP)? Ultraviolet radiation? Galactic Cosmic Rays (GCR)The Galactic Cosmic Rays are the most dangerous type of radiation, posing a threat to human health if they are not stopped. GCR originate from sources situated outside our solar system and there are a number of various such rays.
Alpha rays are the weakest at penetrating solid masses, as an example they can be stopped by a simple sheet of paper or by our exterior layers of skin (they can’t penetrate the deep skin layer). These rays, while weak at penetrating objects, are also extremely dangerous if ingested or inhaled (through contaminated elements) leading to radiation poisoning.Beta rays can be stopped by thin sheets of aluminium or brass foils (usually elementswith low atomic numbers) can be extremelly harmful if ingested or inhaled.
X and Gamma rays have a shorter wavelength than alpha and beta and can be stopped only by dense materials with a high atomic number such as lead.Neutron radiation consists in its structure of a free neutron making this kind of radiation able to travel through air more than the previous radiations presented. In order to efficiently block it, rich hydrogen materials are required, such as water.At the same time, the SEP present in Solar Particle events (SPEs) are a threat to our settlemet’s inhabitants. Even though the magnetosphere shields us from some of these particles we must provide protection in case intense solar bursts occur.
22 3.1.2. Layers of shieldingIn order to protect our colony as best as we can we came up with the next layers of shielding against ionizing radiation:?? ?2 cm of anodized Titanium aluminide: TiAl alloy (resistant to oxidation, extreme heatand corrosion). The main intermetallic compunds are 😮 gamma TiAlo 2-Ti3Al.o TiAl3 (this layer will ensure the structural integrity of Syzygy and the support surfacefor the next layers to be built) 0.5 mm of aluminium foil1 mm of lead plate?1 cm layer of water with boric acid (H3BO3)o useful against the neutron radiationo the walls of the tank that make up the water layer and those of the watter supply ofSyzygy (15 m high) will be made out of Hastelloy C (about 0.5 cm thick) composed of chromium, nickel, molybdenum and iron; these materials have an outstanding corrosion resistance in all sorts of environmets, especially against acids, such us the one used in the 1 cm layer of H2O to protect the colony against neutron radiation.oThermal insulation (airloy):4 cm? The thermal conductibility coeficient of airloy equals 0.020-0.021; its densityequals 0.11g/cm3? We chose to use airloy (a new developing technology) instead of silica aerogelbecause of its superinsulator properties and beacuse it doesn’t change its properties once it interacts with water (important to us due to the proximity of the water layer with boric acid)