Iodine eliminates the need for your tank because it can be stored in solid form.
Most people are probably familiar with iodine through its role as a disinfectant. But if you stayed up until the end of high school chemistry, you might have seen appearances where iodine powder is heated up. Because the melting and boiling points are very close to atmospheric pressures, iodine readily forms a purple gas when heated. At low pressure, it is converted directly from a solid to a gas, a process called sublimation. p>
As it turns out, it could make a great fuel for a type of highly efficient spacecraft propulsion device called ion thrusters. Although it has been considered a promising candidate for some time, a commercial company called ThrustMe has now reported that it has demonstrated for the first time an iodine ion propellant in space.
Rockets rely on chemical reactions to eject large clumps of material as quickly as possible, allowing them to generate enough thrust to lift something into space. But this isn't the most efficient way to create momentum - we end up trading efficiently so we can get the quick push we need to beat gravity. Once in space, this need quickly disappears. We can use more efficient devices to expel the material, because a lower rate of acceleration is acceptable for moving objects between different circuits. The spacecraft uses electricity (usually generated by solar panels) to separate the electron from the neutral atom and form ions. The electrified grid then uses electromagnetic interactions to push it out of the spacecraft at high speeds and generate thrust. The ions eventually leave at speeds that can be higher than a chemical motive. p> Advertising
A relatively small amount of material can be accelerated at once, so it cannot be produced. Anything close to the thrust generated by a chemical rocket. But it uses much less material to produce the same amount of thrust, and can easily produce equivalent acceleration, if given enough time. In other words, if you can be patient with the acceleration, the ion engine can do the equivalent in a way that uses less mass and less space. These are two very important considerations in a spacecraft. p>
To do this according to the spacecraft's energy budget, it is a substance that can ionize without requiring much energy. Currently, the material of choice is xenon, a gas that ionizes easily and is located in the bottom few rows of the periodic table, which means that each ion is relatively heavy. But Zenon has its drawbacks. This is relatively rare (in the atmosphere we have only 1 part per 10 million) and must be stored in high pressure containers, which reduces weight loss. p>
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Iodine appears to be an ideal substitute. It is located next to xenon in the periodic table and is usually found as a molecule made up of two atoms of iodine, so it has the potential to produce more thrust for each substance released. It ionizes easier than xenon and takes 10% less energy to lose an electron. And unlike xenon, it happily exists in solid form under the right conditions, which makes storage much easier. Just a little heating turns it into the gas needed to run the ion engine.
The significant drawback is that it is a corrosive material, which forces ThrustMe to use ceramic for most of the materials that go in. Connection. p>
The extruder design consists of a solid iodine fuel tank that can be heated by resistive heaters powered by solar panels. The iodine itself was contained in a porous material called aluminum oxide, which prevented it from disintegrating due to the vibrations it was subjected to during firing (aluminum oxide is 95% open space, so it didn't reduce fuel storage much). The tank is connected to the ionization chamber through a small tube. When the system cools down after use, enough iodine freezes in the tube to shut off the fuel from the outside world. Other electrons are turned off to form plasma. Then the electrical network adjacent to the positive ions of this plasma accelerated and created a thrust. Electrons are extracted from the plasma and injected into the ion beam to keep everything electrically neutral. Thermal extractors are attached to the electronic components and the walls of the iodine tube, and the heat is circulated into the iodine fuel. The fan was shooting. This keeps the energy needed to vaporize the iodine to just one watt after the extruder has reached a steady state. p>
The entire setup was very compact, taking up about 10 square centimeters of space. It was cubic and weighed only 1.2 kg. And by some standards, it performed 50 percent better than a xenon-based repellent. Beihang Kongshi -1. And over the past two years or more, propellants have been used several times to control satellite motion to prevent potential collisions. Satellite tracking and on-board thrust monitoring show that the iodine-based thrust was operating as it did on the ground during the test. p>
It is important to reiterate that the actual payment rate is negligible. - About 0.8 million N during operation. But the thruster could easily hold it for more than an hour and provide enough thrust to move it into an orbit at an altitude of a few hundred metres. So, while nothing can ever be put into orbit, ThrustMe devices can certainly move things into orbit. p>
The big limitation is speed again. It moves slowly and takes about 10 minutes for the iodine to heat up enough for the extruder to start working. If an emergency maneuver is necessary, he will not interrupt it. But, assuming no one blows up a satellite near you, most of the risks to satellites can be determined in advance. Nature, 2021. DOI: 10.1038/s41586-021-04015-y (about DOIs).
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