On information sites, news often appears about modern technologies or the invention of new progressive materials. Still, such discoveries often do not leave the walls of laboratories or remain the lot of a narrow field of application. Today we will try, using one specific example, to consider how some of these discoveries and unconventional engineering solutions are changing our lives. From a theoretical point of view, this review will be of interest to those fond of popular science, and from a practical point of view, it will be helpful for tourism lovers.
For the review, we have chosen a rather strange at first glance piece of equipment – the Survival Tube. More common names for such products are space blankets, thermal blankets, emergency blankets. The material used to make them is called Mylar, but it is better known as lavsan. To understand what a thermal blanket is in more detail, we will list several specific examples of its use. If you want to delve into a more entertaining topic, we recommend reading the review of how to play online kasino. Some many different techniques and tactics that will be interesting to learn even without the need to apply!
Life blankets were widely used during the Fukushima-1 accident, are an integral part of rescue equipment, are sometimes used by the military, are increasingly used in tourism, and are even used by athletes to keep warm during the triathlon.
The progenitor of the material used in these blankets was created in the 70s by order of NASA and was intended for orbital space stations. The material is a thin film with aluminum sputtering, which gives the lavsan its characteristic silver color. Mylar was initially used to protect the interior of the ship from overheating. For this, the film was placed on the outer side of the skin, where it reflected heat without letting it in.
Mylar’s thermal properties can be used with equal success for keeping warm. In a sense, this is just a matter of perspective. In the example described above, it could be said that the thermal blanket helped the outer space retain heat and not waste it on heating the ship’s interior.
Let’s go back to the daily use of life blankets. Their main advantage lies in the extreme lightness and compactness of the material. When packaged, the veil is about the size of a cigarette pack and weighs about 100 g. That is why it is a must-have item in any first aid kit, where it is used primarily to prevent hypothermia. For this, the victim is covered with a thermal blanket during transportation or waiting for the vehicle.
Types of heat loss
Heat loss occurs in anybody with a temperature other than absolute zero. It is because chaotic movements of atoms and molecules lead to collisions and changes in the internal kinetic energy, part of which is given off into the external space in the form of radiation. The thermal blanket with aluminum sputtering allows you to reflect 80% -97% of such losses and has no competitors in this regard, especially in terms of weight, volume and cost.
However, radiation loss is only one type of heat loss. Much heat is also lost due to convection and heat conduction. Convection is especially pronounced when a person gets wet. Rapid moisture evaporation into the environment leads to significant heat losses and accelerates hypothermia. The thermal blanket allows you to surround a person with an additional barrier.
The most common form of heat loss is conduction. For example, try lying on the snow in winter, and you will immediately feel the heat transfer from a warmer body to a less heated one. It is thermal conductivity.
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Advantages and Disadvantages of Classic Thermal Blankets
The classic thermal blanket means its most common form (90% + cases). Rectangular blanket (blanket) measuring approximately 1.5 x 2 meters, or a bag for one person, resembling a regular large garbage bag.
- The main advantages of a mylar cape, as already mentioned, are its small size (about a pack of cigarettes) and lightweight (about 100 g), which allows you to carry the thermal blanket not even in your bag but in your pocket. In addition, to the pluses, you can add cheapness (a few dollars), the best indicator of reflection of thermal radiation (ordinary clothes and sleeping bags, in principle, do not have such properties but only create a layer of warm air around the body, thus reducing the temperature difference and slowing down heat loss for due to the lack of direct contact between the body and cold air/ground).
- A cape, especially a bag, helps to stay dry during rain and significantly reduces convective heat loss during strong winds, keeping warm air around a person. Unlike clothes and a regular sleeping bag, the thermal blanket does not get wet and therefore does not lose its heat-preserving properties in the rain.
Thermal blankets do not have one drawback that negates all the advantages mentioned above, but several minor disadvantages exist. First, a thin film does not prevent heat loss due to conduction. If you lie on the snow in a thermal blanket, then a thin layer with a thickness of less than a millimeter will not make any difference in heat loss. Similar heat loss will occur if the thermal blanket touches human skin, which is difficult to avoid in rain or strong winds.
Mylar itself is a pretty noisy material. Imagine that instead of a sleeping bag, you are lying in a large grocery bag rustling with active movement inside. However, if you do not forget that thermal blankets are often used to prevent hypothermia and save lives, it is hardly worth complaining about such a feature of the material.
Mylar is also not the most damage-resistant material, and if handled carelessly, punctures or tears can appear in it. The material does not lose its properties after this, and however, obviously, it will be worse to protect from rain and wind. Considering that the strength of Mylar can again be compared with an ordinary grocery bag, you should not be afraid that it will tear at the first opportunity. With appropriate careful handling, the thermal blanket will last for several years, and in an inviolable state, it will stay even longer.
Even if you breathe outside the bag, condensation can be pretty noticeable due to the natural release of moisture through the pores on the skin. This moisture build-up should not be confused with perspiration as it appears even at low temperatures. In extreme cold, a person may never get warm inside the thermal bag, but moisture will still accumulate on the walls and be absorbed by clothes. Condensation can be reduced from time to time by opening the bag and allowing the water that has not yet condensed to come out.
Using Mylar as a cape reduces condensation, but at the same time, increases heat loss due to the appearance of open areas around the body and less reliable protection from wind and rain.
Some manufacturers combat condensation by creating an extra hole near the feet or by adding micro holes in the material itself. In these cases, condensation is reduced, but again together with a heat retention factor and protection against bad weather conditions.