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SELF-FUEL FUEL FOR ROCKET MODEL ENGINES
Glossary of terms
Composition No. 1: 60% (9KNO 3 ) + 30% (9SORBITA) + 10% (9S) 9 - higher plasticity
Composition No. 2: 63% (KNO 3 ) + 27% (SORBITA) + 10% (S) - maximum specific gravity
This rocket fuel is a new and much more advanced variation of sorbitol fuel. Its higher burning speed is also a high specific impulse, allowing it to be used as if in medium, as well as in impressive rocket engines. It was designed by me just now, i.e. finalized, because Use sorbitol as a binder invented not by me. Yet similar compositions were published on some Internet web pages. But they also did not become popular among rocket-builders. And we think that you know why.
The composition of the newly made sorbitol fuel includes sulfur, which participates in the combustion reaction:
6C 6 H 14 O 6 + 26 KNO 3 + 13S = 13K 2 S + 36CO 2 + 13 N 2 + 42 H 2 O (theoretically)
At the very session, the reaction proceeds according to a more complex mechanism, and on the oxidation-reduction properties of elements it is possible to get excited that at the very beginning, the reaction will proceed exactly by an unsophisticated mechanism, but then the reaction products will interact with each other, giving already other compounds. The correct ratio of components ensures high efficiency of this fuel. This fuel has relatively high energy characteristics. The lesson is that sulfur participates here as if the reductant 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 K 2 O does. The energy released is enough to shift the equilibrium toward the upbringing of such low-molecular products, as if CO and H 2 . This contributes to a significant increase in the specific thrust of the fuel. Thus, the efficiency of the engine increases by an average of 15 - 20% (based on rough estimates), but it can also be more. So it can be said that this rocket fuel is a worthy replacement for gunpowder and ordinary caramel.
Disadvantages of this fuel in comparison with conventional sorbitol are: complexity in manufacturing, low plasticity, impossibility of casting the composition in the engine casing, fast rate of solidification, with insufficient heating of sorbitol, the fuel quickly solidifies. Experience has shown that this fuel is well prepared to be used also in the cold season, as if the humidity in the atmosphere is significantly lower than in the summer. Perhaps the most important problem of this fuel is the rapid rate of solidification and the impossibility of pouring fuel directly into the engine casing. Even this fuel 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 becomes porous, which contributes to the occurrence of anomalous combustion - an unstable intermittent combustion caused by a decrease in the supply of heat to unreacted fuel, lasting from several parts up to 2 seconds . Especially this problem is typical only for small engines, with a fuel charge of 30-35 grams - pressing "Powerful caramel" into such engines - the work is very painstaking and complicated, but on large engines such a thing almost does not affect in any way, volume of fuel, air voids are insignificant. Although this fuel also hastily hardens, but this problem can easily be eliminated by putting the fuel tank on the heated sand bath. This is a very suitable way, well, look not to overdo it with the temperature, but the sulfur in the fuel will melt and the mishmash will become heterogeneous.
At the source, when it was made, serious problems began. It was difficult to find a balance between the melting point of sorbitol and the melting temperature of sulfur, but when mixing the melts of both components, the fuel was not extremely homogeneous. A variation with the use of glycerol 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 pellet and also increased hydroscopy.
Sorbitol under strong heating also after subsequent cooling hardens in no way at once and also retains plasticity for a sufficiently long time, which is enough for refueling 2 to 3 small engines. Sorbitol is forced to be heated up to a sufficiently high temperature (about t bp ). When we warm it up to such a temperature, it smokes a little, it becomes transparent (slightly yellowish), and small bubbles form on the bottom, which indicates the source of the boiling.
Before you start to melt sorbitol, you should prepare all the ingredients in advance.
1. First, weigh the necessary amount of sorbitol also put it away from the place of work
2. Next you will need to grind the potassium nitrate. Before grinding it should be carefully dried, it is possible on the battery, but we dried it in the oven at t ≈ 200 0 C , more than this temperature is impossible, t. begins its melting and then decomposition. Dried potassium nitrate is easier to grind and also less adheres to the walls of the electric coffee grinder, carried wet. We made the milling in the electric coffee grinder in which place for about 40 seconds. If it sticks to the walls, then it can be scraped with cotton buds or hands, just not naked, but using disposable gloves.
3. After grinding, weigh the necessary portion of saltpeter and place it in a clean jar. he stuck to my glass.
4. Then you need to hang sulfur.
The sulfur that we use in fuel contains coal in the following ratio: 100% (S) + 5% (C) (by weight) .
When using coal, the mass forms less lumps, becomes more crumbly, and almost does not adhere to the walls of the electric coffee grinder during grinding. However, you need to grind intermittently so that sulfur does not melt away from excessive friction. After grinding, it remains highly electrified and will also form lumps. As we have noticed, it takes quite a long time for the sulfur to become crumbly after the grinding, so it should be milled in advance. ( more details >> )
5. Only later, as if you measured everything you can melt sorbitol. For these purposes, I used my favorite miniature oven, but at what time I did not have it at all we managed with a stove. Sorbitol fits into a metal container, but it is better to use a stainless steel container (we personally use a stainless steel mug, which I bought in the shop "Everything for fishing is hunting" ) and heats up to a temperature close to its boiling point.
6. Then, finely ground, also dried potassium nitrate (potassium nitrate) is added to it. Before you fall asleep, shake the vial with saltpetre well enough to make it more friable.
7. The mixture is stirred until complete homogeneity. With this ratio of saltpeter and sorbitol, the mishmash starts to harden quickly, so you will have to reheat the contents of the glass until the mixture becomes agitated.
8. After the mishmash has cooled to a temperature below the melting point of sulfur, sulfur is added to it. The temperature can be checked by throwing a small amount of sulfur in the above mixture of niter also sorbitol, if the temperature is extremely high, then the sulfur will melt also to form small, bright droplets on the surface. Stir all the components must be very quickly, so that the mashing did not have time to harden.
10. After that, pull out the plastic mass (preferably use disposable polyethylene gloves) with a knife or other metal object. The mixture should also be scraped off from the walls of the mug, and again again with hands for greater uniformity (use polyethylene gloves!).
I want to note that the fuel starts to harden quickly, so we again place its mug also put in a heated oven, but only already turned off, because it kept the heat in it and it also helps to keep the temperature of the fuel melt very well and it does not stay plastic for a long time. In the oven, you can also put some heat-consuming materials: neat dry sand, metallic nuts, nails, lead is excellent. By measure of need, the pieces of fuel are plucked from the main mass and also carefully pressed into the motor housing.
To make pressing of fuel follows small portions, because if the fuel is pressed in any way not under sufficient pressure, then a lot of air bubbles will remain inside the fuel saber. As shown experiment for pressing it is better to use a graphite stick impregnated with paraffin, also with a polished tip. For these purposes, the fluoroplast is also suitable, but the fuel still sticks to it, and it is also desirable to have a rag with your hand to remove the plaque. All work is desirable to be carried out in a dry room. As I already mentioned, this fuel is more suitable for manufacturing large fuel charges (from 70g ) for impressive engines.
From the creator: I do not know if this fuel will become popular with rocket scientists as well as chemists, but in the course of a long work with him we came that this is the only powerful fuel that can be received without much difficulty, in comparison with perchlorate. And the lower essence of sorbitol makes it a little more profitable to use, if you certainly have sulfur is cheaper than sorbitol. Since the main time, to cook it as if necessary, you will not succeed, but in the course of a long work with it, you really will see the difference. It may seem to you that this method of manufacturing this fuel is unsafe, but in all my practice there was not a single state of emergency , because we strictly observe the purity of the reagents and do not allow any substances that ignite below 200 0 C. With strict adherence to the cleanliness of the workplace, this remedy is relatively safe.
PS The material is protected.
Date of publication 22.02.2005гг