On the pages of ITC.ua there are often news about modern technologies or the invention of new progressive materials, but often such discoveries either do not leave the laboratory walls, or remain a lot of narrow scope. Today, we will try, with one concrete example, to consider how some such discoveries and unconventional engineering decisions change our lives. This review in the theoretical plan will be of interest to those who are fond of popular science, but from a practical point of view it will be useful for tourists.
For review, we chose a rather strange at first glance element of the equipment – Survival Tube. The name is translated unaccustomed to our ear by the phrase “pipe for survival”.
More familiar names of such products are: space blanket, thermal blanket, emergency blanket. The material used for their manufacture is called Mylar, but here we are more known as lavsan. To get a better understanding of what a thermal blanket is, let’s list some concrete examples of its use.
Rescue blankets were widely used during the accident at Fukushima-1, are an integral part of the rescue equipment, in some cases used by the military, are increasingly used in tourism, and even used by athletes to warm up during the triathlon.
The progenitor of the material used in such blankets was created in the 1970s by order of NASA and was intended for space orbital stations. The material is a thin film with aluminum deposition, which gives the lavsan a characteristic silver color. Initially, the Mylar was used to protect the internal parts of the ship from overheating. To do this, the film was placed on the outside of the skin, where it reflected heat, not passing it inside.
With the same success, mylar thermosvings can also be used to preserve heat. In a sense, this is only a matter of perspective. In the example described above, it could be said that the thermo blanket helped the outer space to retain heat and not spend it on heating the interior of the ship.
Let us return to the daily use of rescue blankets. Their main advantage lies in the extreme lightness and compactness of the material. In a packaged form, the blanket has the size of a cigarette pack and weighs about 100 g. That is why it is an indispensable element of any first aid kit, which is used primarily to prevent hypothermia. For this, the victim is covered with a thermo-blanket for the period of transportation or waiting for the vehicle.
Types of heat losses
Thermal losses occur in any body with a temperature different from absolute zero. Chaotic movements of atoms and molecules lead to their collisions and changes in internal kinetic energy, part of which is given to the external space in the form of radiation. Thermo blanket with aluminum spraying allows to reflect 80% -97% of such losses and does not have competitors in this respect, especially in terms of unit weight, volume and cost.
However, losses in the form of thermal radiation are only one type of heat loss. A significant part of the heat is also lost due to convection and thermal conductivity.
Convection is especially pronounced when a person is wet. Rapid evaporation of moisture into the external environment leads to large heat losses and accelerates hypothermia. The thermal blanket allows to surround the person with an additional barrier, inside which the humidity rises rapidly and thus the heat losses to the external environment with lower humidity cease. Having said this, it should be clarified that the use of thermal blankets is much more effective and rational in dry clothes.
The most common form of heat loss is heat conduction. Try to lie down on the snow in winter, and you will immediately feel how heat passes from a warmer body to a less heated one. This is the thermal conductivity.
The thermo blanket fights all the above types of heat losses, most efficiently coping with radiation losses – reflecting up to 97% of the heat back. However, the figure of 97% misleads some people, and they believe that using a thermo blanket will be able to stand in the frost in one T-shirt and at the same time will not be cold at all. About what level of protection can be expected from rescue blankets, we’ll talk more low.
Advantages and disadvantages of classical thermo-clothes
A classic thermal blanket means its most common form (90% + cases). A rectangular cape (blanket) measuring approximately 1.5 x 2 meters or a bag for one person, reminiscent of a normal large-sized garbage bag.
The main advantages of Mylar capes, as already mentioned, is a small size (with a pack of cigarettes) and light weight (about 100 g), which makes it possible to wear a thermal blanket even in a bag, but in a pocket. In addition, you can add to the pluses cheapness (a few dollars), the best indicator of the reflection of heat radiation (conventional clothes and sleeping bags in principle do not have similar properties, but only create a layer of warm air around the body, thus reducing the temperature drop and slowing the heat loss in account for the lack of direct contact between the body and cold air / earth).
The cloak, especially the sack, helps to stay dry during rain and significantly reduces convective heat loss during a strong wind, keeping warm air around the person. Unlike clothes and a usual sleeping bag, the thermo blanket does not get wet and therefore does not lose its thermo-preserving properties in the rain.
There is no one special drawback that negates all the above-mentioned advantages, there are no thermo-goals, but there are several small disadvantages. Thin film does not save from heat loss due to thermal conductivity. If you lie in a thermal blanket on the snow, a thin layer with a thickness of less than a millimeter will not create any difference in terms of heat loss. Similar heat losses will occur if the thermal blanket touches the human skin, which is difficult to avoid in the case of rain or strong wind.
Mylar itself is quite noisy material. Imagine that instead of a sleeping bag you are lying in a large package for foods rustling with active movement inside. However, if you do not forget that thermo blankets are often used to prevent hypothermia and literally save lives, it’s hardly worth complaining about such a feature of the material.
Mylar is also not the most resistant to damage material, and with inaccurate handling, punctures or tears may appear in it. The material does not lose its properties after that, however, it will obviously be worse to protect it from rain and wind. Given that the strength of mylar again can be compared with the usual product package, do not be afraid that it will break at the first opportunity. With appropriate careful handling, the thermo blanket will last several years, and in untouchable form it takes even longer.
Depending on the form (cape or package), mylar may or may not have one drawback. If this is a package, then condensation of moisture on the inner walls is much more pronounced. To reduce it, you can collect the neck of the bag around your neck and exhale outward, that the truth is not always possible, for example, during rain or in extreme cold.
Even if you breathe outside the package, condensation due to the natural release of moisture through the pores on the human skin can be very palpable. Do not confuse this accumulation of moisture with sweating, since it manifests itself even at low temperatures. In severe cold, a person may not get warm inside a thermal pack, but moisture will still accumulate on the walls and soak up clothing. Reduce condensation from time to time opening the bag and letting condensed moisture come out.
Obviously, the use of Mylar in the form of a cape reduces condensation, but at the same time increases heat loss due to the appearance of open zones around the body, and also due to less reliable protection from wind and rain.
Some manufacturers try to fight with condensation, creating an additional hole near the legs or adding micro-holes in the material itself. In these cases, condensation is reduced, but again, together with the coefficient of heat conservation and protection from bad weather conditions.
Blizzard Survival Tube
Considering all the above advantages of Mylar, and especially its cheapness, the creation of new types of tourist equipment based on this material was only a matter of time. Mylar is already used in NeoAir mats by Therm-r-Rest, making NeoAir XTherm the most efficient mat in terms of the ratio of the thermal insulation coefficient to the gram weight. At exactly the same weight as the usual Izhevsk karemat (400 grams) and an order of magnitude smaller (1.5 l in the folded state), such a rug can be used at temperatures down to -25 degrees and it is much more convenient for sleeping due to its thickness (6 cm).
However, today we are talking about another piece of equipment – Blizzard Survival Tube. Such accessories have long been used by military and rescue workers, and recently – by tourists.
Blizzard Survival Tube is a modified and improved version of thermo-ideas and can successfully replace both a single tent and a sleeping bag.
The Survival Tube uses the Reflexcell material, which is a modified version of mylar. There are two main improvements. The first of these is multi-layered. This in itself does not give any special advantages, because several layers of mylar will only make the thermal blanket heavier and more voluminous without improving its thermo-preserving qualities.
The catch is that, like the NeoAir XTherm, the Survival Tube uses a diamond-shaped Mylar structure that allows you to keep the air inside, and this allows you to kill two birds with one stone at a time. Additional layers of mylar slow heat loss in the form of thermal radiation, returning it back, if the first layer failed. And the use of diamond-shaped traps, in fact, turns Survival Tube into a sleeping bag. Only in the usual sleeping bag, warm air is retained with fluff or synthetic insulation, and in Survival Tube due to the very structure of the material.
Thus, air traps reduce heat loss due to thermal conductivity, which radically distinguishes the Survival Tube from conventional rescue blankets from dolcans, a similar property not possessing.
Compared with the usual Mylar, Reflexcell also significantly (by sensations – several times) increased the strength of the material, making it more resistant to damage.
To combat condensation, the Survival Tube is equipped with two entrances with puffs on each side. To maintain heat, they can be tightened more forcefully, and to reduce condensation – on the contrary, slightly open. Such a small, seemingly modification allows you to sleep better in the Survival Tube, as in conventional thermo-blankets, an unattached throat around your neck can open during sleep, which entails a rapid loss of heat.
Double input also performs one more function. Survival Tube, if necessary, can be used as a refuge for two people. You can lie with this as head to head, and feet to the head. Blizzard recommends the second option, because in this case, two people more effectively use the inner space of the shelter, without stretching the film and not reducing the interlayer of air bags.
Notes from fields
Survival Tube takes about 1 liter in a backpack in the original packaging and weighs about 540 g. In emergency situations, the packaging is torn over the applied red line, and Survival Tube turns into a small shelter.
At the same time, Survival Tube can be used as a normal element of tourist equipment to replace both sleeping bags and tents.
After the person is inside the Survival Tube, it is necessary to fully tighten the entrance near the legs and around the neck. In this case, heat losses are minimized. Given the characteristics of Reflexcell and the need to preserve the rhombic structure of internal packages, it is also necessary to collect material around it. In a more understandable language, this means – making the tube as narrow as possible, so that the air bags become larger and warmer. Nothing is complicated in this, and Reflexcell itself aspires to this form, but in the area of the torso the material can be slightly corrected.
The rigidity of Reflexcell also reduces the noise of the Survival Tube, as the material does not rustle under the gusts of strong winds and from the chest rising during respiration.
For the best results with Survival Tube it is advisable to use the karemat, however, in its absence, the heat loss can be reduced by placing a backpack, clothes or small branches with leaves or spruce needles. Branches should be placed not from the inside, but from the outside. They isolate the worst, but it’s better than nothing at all.
There were no particular condensation problems with Survival Tube. Again, purely subjective, it is lower than in conventional thermal packs. In the first place, apparently, it affects the ability to leave the entrance near the legs a little open (enough openings the size of an orange). Given the length of the Survival Tube, the legs are at some distance from the entrance and do not freeze.
When using Survival Tube, as, in principle, and other thermo-clothes, one unusual effect is observed. If you get warm at night in a normal sleeping bag, you will not notice anything unusual, but in a rescue blanket you will feel that a small infrared radiator has been sent to you and you receive heat from outside. The source of heat, of course, is the heat of its own body, radiated, and then reflected back. However, in everyday life we are not accustomed to such heat returns, especially on a cold night, and therefore they are perceived rather unusual.
Describe in words how much warms Survival Tube, it is difficult, if only because people perceive the temperature differently. When one is cold, others are hot. And yet, Survival Tube, no doubt, warms considerably better than conventional thermo-clothes, and at the expense of an integrated approach to preventing heat losses it protects well even on cold nights. While inside this small shelter was very warm during the tests, a relatively strong wind blew from the outside all night long, on which it was easy to freeze for 5-10 minutes. Emphasizes the effectiveness of Survival Tube and the fact that it was lying on a cold and slightly damp sand after a recent rain.
Probably, the main, though not very significant drawback of Survival Tube is connected with the use of air packages in it. Because they are inside the material, Survival Tube is difficult to pack up to its original compact state. In ordinary tourist sleeping bags, this is not a problem, since their material flows through the air, but in Mylar small holes are only at the edges of the pipe and it is quite difficult to force air through them through numerous channels. At home, this can be done with a vacuum cleaner, however, in field conditions, it is necessary to put up with the fact that after packing the thermowell will occupy more space than in the original packaging.
In conclusion, you can add that Survival Tube, like an ordinary sleeping bag, despite the unintuitive nature of this fact, it is better to use with a minimum of clothing on the body. This way the body will be better warmed from the reflected and stored around it heat, while in tight pants and a jacket, not to mention shoes, under completely analogous conditions, you can lie all night without warming yourself.
How Survival Tube protects against weather
Survival Tube completely protects the person from the wind, and due to the rigidity Reflexcell reduces heat loss due to skin contact or clothes with the material. Clinging to a man under the gusts of a strong wind, mylar in classical thermo-suits quickly brings heat outward, and in the Survival Tube this does not happen, or occurs on a much smaller scale.
During the rain inside Survival Tube you can hide without problems, taking with you a backpack. This is achieved due to the impressive length of the pipe – 2.45 m.
Survival Tube warms better than conventional thermo-clothes. The main difference is achieved due to the possibility of capturing air in special packages. As already mentioned, they reduce the heat loss from thermal conductivity. The peculiarity of these packages is that it takes some time to warm up the air inside them. If you get a little frozen in the Survival Tube, then the packages around the torso will warm up quickly, but the heat will get to the feet unusually slowly compared to the sleeping bag. During the Survival Tube check it took about 40 minutes. It can not be said that at this time it was uncomfortable to be inside, but the bottom part of the package was definitely warming up longer than expected.
Blizzard Survival Tube is an innovative element of equipment, first adopted by the military and rescuers, and now penetrated into the sphere of tourism. By the ratio of the quality of protection against cold and bad weather (rain, wind, dust) in terms of weight and volume per unit, Survival Tube has no competitors and can be used by experienced tourists as a super compact and easy replacement for both the sleeping bag and the tent. If someone is not ready for such drastic changes, then Survival Tube can be used as a heater for light sleeping bags. This approach is much cheaper and more universal than buying one more sleeping bag. Using Survival Tube as a cover for an existing sleeping bag, you can add to it about one season (for example, from summer to turn into autumn) with minimal influence on the weight of the backpack.
Depending on the application, Survival Blizzard can be taken in one of three colors. Silver with a reflective surface and orange are perfect for rescuers and those who plan to use Survival Tube as a safety hiding place in case of unforeseen circumstances in difficult hikes. Such a coloring is clearly visible from afar and will help rescuers find victims faster. For those who want to remain unnoticed, there is a more secretive green version, inconspicuous from a distance and almost not attracting attention.