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MODEL FUEL FOR ENGINES OF MODELS OF ROCKET
Composition # 1: 60% (9KNO 3 ) + 30% (9SORBIT) + 10% (9S) 9 - higher ductility
Composition # 2: 63% (KNO 3 ) + 27% (Sorbitol) + 10% (S) - maximum specific thrust
This rocket fuel is new as well as a much more improved variation of sorbitol fuel. Its higher burning rate and a high specific impulse make it possible to use it, as it were, in medium, as well as in impressive rocket engines. It was developed by me just now, i.e. finalized because use sorbitol as a binder invented by no means me. Yet similar compositions were published on some Internet web pages. But they also did not become popular among rocket makers. And we think that you know why.
The composition of the new sorbitol fuel includes sulfur, which is involved in the combustion reaction:
6C 6 H 14 O 6 + 26KNO 3 + 13S = 13K 2 S + 36CO 2 + 13N 2 + 42H 2 O (theoretically)
At the very lesson, the reaction proceeds according to a more complex mechanism, according to the redox properties of the elements, that at the very beginning, the reaction will begin to follow exactly the unsophisticated mechanism; The correct ratio of components ensures high efficiency of this fuel. This fuel has relatively high energy characteristics. The lesson is that sulfur is involved here as if the reducing agent also displaces the remaining oxygen atom from the K 2 O molecule, which increases the energy yield of the reaction. In addition, K 2 S does not take CO 2 , as it is K 2 O. The energy released is enough to shift the equilibrium towards raising such low-molecular products, as if CO and H 2 . This contributes to a significant increase in specific fuel thrust. Thus, the efficiency of the engine rises on average by 15–20% (according to coarse estimates), but it can also be greater. So it can be said that this rocket fuel is a worthy substitute for gunpowder and ordinary caramel.
The disadvantages of this fuel compared to conventional sorbitol are: difficulty in manufacturing, low plasticity, impossibility of pouring the composition into the engine block, fast solidification rate, with insufficient heating of the sorbitol fuel quickly hardens. Experience has shown that this fuel is also well prepared to use in the cold season, as if the humidity in the atmosphere is much lower than in summer. Perhaps the most important problem of this fuel is the rapid speed of solidification and the impossibility of pouring fuel directly into the engine block. This fuel also has a very unpleasant thing - with insufficient compaction of the mass inside the fuel charge, voids are formed, which greatly affects the uniformity of combustion of the entire charge. Simply put, the structure is made porous, which contributes to the occurrence of anomalous burning — intermittent intermittent burning caused by a decrease in the supply of heat to unreacted fuel, which lasts from a few fractions up to 2 seconds . Especially this problem is characteristic only for small engines, with a fuel charge of 30 - 35 grams - pressing "Powerful caramel" into such engines - work is also very laborious and difficult, well, but on large engines this thing almost does not affect, because the volume of fuel air voids are insignificant. Although this fuel is also rapidly hardened, this problem can be easily eliminated by placing the fuel tank on the heated sandy steam room. This is a very adapted way, well, do not overdo it with the temperature, however, the sulfur in the fuel will melt and the hodgepodge will become non-uniform.
By the source, in its manufacture, serious problems began. It was difficult to find a balance between the melting point of sorbitol and the melting point of sulfur, but when mixing melts of both components, the fuel turned out to be extremely non-uniform. The variation with the use of glycerin was considered so that the mass retained plasticity for a long time. But the use of glycerin led to a decrease in the strength of the fuel checker and also increased hydroscopicity.
Sorbitol with strong heating and subsequent cooling hardens in no way at once and also retains plasticity for quite a long time, which is enough for refueling 2 - 3 small engines. Sorbitol is forced to be heated up to a sufficiently high temperature (about t kip ). When we heat it up to this temperature, it smokes a little, becomes transparent (slightly yellowish), and small bubbles form at the bottom, which indicates the source of boiling.
Before you start to smelt sorbitol, all components must be prepared in advance.
1. First, weigh the required portion of sorbitol and also set it aside from the place of work.
2. Next you need to grind potassium nitrate. Before grinding, it should be thoroughly dried, the battery can be moistened, but we dried it in the oven at t ≈ 200 0 C , it is impossible to exceed this temperature, because its melting also begins then decomposition. Dried potassium nitrate is easier to grind and also less sticks to the walls of the electric grinder, carried wet. We grind in an electric grinder at some point in about 40 seconds. If it is stuck to the walls, then it can be scraped off with cotton buds or with hands, just not bare, but using disposable gloves.
3. After grinding, weigh the necessary portion of nitrate and also place in a clean jar, I used a plastic one, because he stuck to the glass.
4. Then you need to weigh sulfur.
Sulfur, which we used in fuel, contains coal in the following ratio: 100% (S) + 5% (C) (by weight) .
When using coal, the mass forms fewer lumps, it becomes more crumbly and almost does not stick to the walls of the electric grinder at all during grinding. However, it is necessary to grind intermittently so that sulfur does not melt due to excessive friction. After grinding, it remains strongly electrified and will also form lumps. As we noted, it takes quite a long time for sulfur to become crumbly after grinding, so it should be ground beforehand. ( more >> )
5. Only after that, as if you measured everything, it is possible to melt sorbitol. For these purposes, I used my favorite miniature oven, but at what time I didn’t have it, we did it with a stove. Sorbitol fits in a metal container, but it is better in a stainless steel tank (we personally use a stainless steel mug, which I purchased in the “Everything for fishing and hunting” shop) and heats up to a temperature close to its boiling point.
6. Then, finely ground and also dried potassium nitrate (potassium nitrate) is added to it. Before you fall asleep, shake the bottle of saltpeter thoroughly to make it more crumbly.
7. The mixture is stirred until complete homogeneity. With such a ratio of nitrate, the mash of sorbitol also starts to harden quickly, so you have to heat the contents of the glass again, until the mixture is suitable for mixing.
8. Once the mash has cooled to a temperature below the melting point of sulfur, sulfur itself is added to it. The temperature can be checked by throwing a small amount of sulfur into the above mixture of saltpeter also sorbitol, if the temperature is extremely high, the sulfur will melt also to form small, bright droplets on the surface. You need to stir all the components very quickly so that the hodgepodge does not have time to harden.
10. After that, pull out the plastic mass (preferably using disposable polyethylene gloves) with a knife or other metal object. It seems that the mixture should be scraped off the walls of the mug as well, and still again be bent by hand for greater homogeneity (use polyethylene gloves!).
I want to note that the fuel starts to quickly solidify, so we again place his mug and put it in a heated oven, but just turned off, because It has retained heat. It also perfectly helps to keep the temperature of the fuel melt. It also does not remain plastic for a long time. In the oven you can also put some heat-consuming materials: neat dry sand, metal nuts, nails, lead is perfect. To the extent necessary, pieces of fuel are pinned off from the main mass and are also carefully pressed into the engine block.
The fuel must be pressed in small portions, because if the fuel is not pressed under sufficient pressure, then a lot of atmospheric bubbles will remain inside the fuel block. As the experiment showed, it is better to use a graphite stick soaked in paraffin, also with a polished tip, for pressing in. Fluoroplast will also be suitable for these purposes, but the fuel still sticks to it. It is also advisable to have a cloth at hand with which you will eliminate the plaque. All labor is desirable to carry out in a dry room. As I have already noted, this fuel is more suitable for the manufacture of large fuel charges (from 70g ) for impressive engines.
From the creator: I don’t know in any way whether this fuel will become popular among rocket designers as well as chemists, but during the long work with it we came that it is the only powerful fuel that you can get without much difficulty compared to perchlorate. A lower essence of sorbitol acts its slightly more profitable to use, if undoubtedly your sulfur is cheaper than sorbitol. From the main point, you should not be able to cook it as if you should, but in the course of a long work with it, you will really see the difference. It may seem to you that this method of manufacturing this fuel is unsafe, but throughout my entire practice there was no emergency at all , because we strictly observe the purity of the reagents and also do not allow the ingress of substances that ignite below 200 ° C. With strict adherence to the cleanliness of the workroom, this tool is relatively safe.
PS Material is protected.
Publication date 02.02.2005