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China and the United States are immersed in a race that is not fought on the mainland, but in the air with a common goal: to achieve speeds of more than 7,000 km/h. Both have several hypersonic airplanes projects With potential both military and civil And, although the US seems more reserved, China from time to time goes out to the arena to talk about Your technological achievements. The latest is an engine capable of going to Mach 6 thanks to a fuel formula with a special ingredient: magnesium. Mach 6. When we talk about hypersonic speeds, what we use to measure it is the Mach 1. is the one that represents the speed of sound, established in 1,235 km/h. Thus, a Mach 2 speed would be twice the speed of sound. Well, what are testing At Beihang University in Beijing it is a technique that allows to double the thrust of current hypersonic engines to reach Mach 6 and higher speeds. It is difficult to get an idea of ​​the amounts we talk about, since we are talking about speeds of more than 2,000 meters per second or around 7,000 kilometers per hour. It would be like going from Madrid to New Delhi in an hour. That journey, currently, has between eight and ten hours. EITHER cross the Atlantic in three. Scramjets. The objective of the researchers is to redefine hypersonic aviation thanks to a combustion technique that, as we read in South China Morning Postpractically doubles the thrust of a scramjet engine. It is the abbreviation of “Supersonic Combustion Ramjets”, these Ramjets being reaction engines created to reach Mach 3 speeds. To function, the air enters the engine at high speed. They are motors without turbines that compress that air at supersonic speed (do not slowly subsuite like Ramjets) and then the fuel is injected. It can be hydrogen, but also kerosene, which is mixed with compressed air and, as a result, a supersonic jet of hot gases that propels the vehicle is generated. When it occurs for the first time, it is when the sound barrier is broken and something similar to an explosion is heard. “Secret” ingredient. The problem of Scramjet engines is that, at extreme speeds, the energy generated by fuel is stabilized, but adding magnesium to the fuel formula, the thing changes. The Chinese team chose magnesium being a metal with a violent reactivity. When the kerosene burns it generates residual, but when they inject magnesium dust, that CO₂ acts as an oxidant lighting the magnesium particles. Yang Qingchun is the project director and comments that “magnesium does not need atmospheric oxygen”, so those magnesium dust particles react in explosive shapes with the residual gases that were previously wasted, now releasing an additional energy. China hypersonic test vehicle Evidence. And they have tested. Under conditions that simulate a Mach 6 to 30 kilometers altitude flight and using commercial aircraft fuel, magnesium injection increased the thrust by 86.6% with a combustion efficiency of 65.1%. This allows to increase the 613 Newtons-second motor thrust per kilogram at 1,126 Newtons-Second per kilogram. At that speed, the kerosene burns practically completely, the magnesium dust turns to the contact and releases the heat between two and three times faster than only the kerosene. But speed is not the only advantage. Something crucial is not to overheat the turboreactor, so researchers have studied how to optimize the process to increase performance without a temperature increase. Thus, it is the kerosene that acts as a refrigerant of the motor walls through regenerative cooling. The magnesium, which is added later, burns in a “storm of supersonic fire”, according to the researchers, which is stabilized thanks to an optimized flow route that, in turn, helps to achieve that more powerful thrust. Challenges. But of course, the higher the speed, the greater the challenges. We have already commented that the temperature is something that plays against supersonic ships Because they must resist friction that makes the temperature rise above 1,500 degrees Celsius. In addition, at more speed, more turbulence. The team states that this supersonic turbulence entails the risk of an unequal dispersion of magnesium dust inside the postquemor. If there is a bad penetration of the particles, or an irregular injection, the thrust gain falls to almost 20%. It is something that causes the engine to be very unstable. In addition, those magnesium particles that “exploit” are a double -edged sword. On the one hand, the explosion generates that violent reaction that increases the thrust, but at the same time the particles become microcuchillas that can damage the engine. Therefore, you have to investigate engines with the capacity to resist impacts inside. On the other hand, you have to stabilize magnesium injection because it is postulated as something ideal to quickly reach hypersonic speeds and maintain them, but a ship fluctuates in speed, it is an unstable fuel. They have added nitrogen gas to stabilize the entrance of the particles, but the team confesses that it is “as difficult as threading a needle in the middle of a hurricane.” Projects. It is something that China will continue working because it is the team itself that states that it is not something only for airplanes: Yang comments that its design can reduce the launch weight or extend the range of missiles. They will try to inject magnesium on a nanometric scale to see if it is more efficient, but it is clear that it is a project that interests the country. And, yes, China has already tested higher speedsbut what they are looking for is more stability and the way to change between speeds at pleasure, not in such a linear way. And he does it because the United States is also working on it. Not only in aircraft like Blackbirdbut also in systems such as Dark Eagle, a missile with a range of more than 3,000 kilometers and capable of reaching speeds greater than Mach 17 (about 20,000 km/h) with systems to … Read more