2023-10-20 23:00:00
Spin Launch, an aerospace startup, is developing technology to launch a projectile by placing it in a large vacuum centrifuge and then rotating it quickly and throwing it. Provided by SpinLaunch When thinking of a launch into space, most people think of a ‘rocket’ that emits an intense flash of light. The reason a powerful rocket that can overcome the Earth’s gravity is needed to send something into space is to quickly reach the orbital speed to orbit the Earth or the escape speed to escape the gravitational sphere. The International Space Station, which orbits at an average altitude of 430 km, must maintain a speed of 7.7 km per second to remain in orbit. Fuel accounts for 80-90% of the total weight of the rocket. A rocket launch can be a dream come true because the sight of the launch itself is cool, but looking at it another way, it raises the question, ‘Isn’t this a huge waste of fuel?’ Moreover, since fossil fuels are mainly used, various types of exhaust gases and residual substances emitted after launch immediately cause global warming and adverse effects on health. So, eco-friendly technologies are being developed as an alternative, but there are many technical barriers that must be overcome. When you think of a launch into space, most people think of a ‘rocket’ that emits an intense flash of light. Provided by Getty Image Bank Let’s look at hydrogen rockets as a representative example. It is known that when hydrogen combines with oxygen and burns, only water is released, but this only occurs when low-temperature combustion occurs. Due to the nature of rockets, hydrogen must burn at high temperatures, and about 80% of the atmosphere is nitrogen. Therefore, where high-temperature combustion occurs in the atmosphere, nitrogen oxides (NOx), an environmental pollutant, are inevitably released. Of course, hydrogen rockets have much less environmental impact than existing fossil fuel rockets. Several methods are being developed to slightly reduce the fuel use of these rockets. Ultimately, it will not use rockets, but the principle of the method currently being developed is generally the same. Before ignition of the rocket, the kinetic energy is increased in advance by using velocity or potential energy. Attach a rocket to an airplane and launch it. Provided by Virgin Orbit In the future, the air launch method is expected to be commercialized the fastest as a rocket launch method that reduces fossil fuels. Although Virgin Orbit, the representative company involved, went bankrupt in May of this year, its technology is still valid. If you attach a rocket to a large airplane, reach a certain altitude and speed, and then launch it from there, you can save a lot of energy and fuel. Additionally, in the case of existing rockets, the launch location and direction must be fixed, including damage to residential areas, but air launches are free here. Of course, sea launches are being considered in many ways as an alternative to the shortcomings of ground launches. This is a good alternative for Korea, where the location of the launch site is limited due to geopolitical reasons. The aerial launch that Virgin Orbit has attempted has been met with criticism from a critical point of view: ‘Isn’t the airplane itself a first-stage propellant?’ The ultimate method of air launch using an airplane is ‘Single Stage To Orbit (SSTO)’. You fly like an airplane, go to space, and after completing your mission, you fly like an airplane or glider and come back. However, this is still under research and there are no practical examples. Although there was first talk of launching an aerial launch using a balloon or balloon, it is difficult to control the direction or location of the floating balloon. Even if it is a device that can be controlled to some extent, the slow speed is a barrier that must be overcome. Throw the rocket around and launch it. In addition to providing pinLaunch, a feasible method is the ‘fast throwing’ technology. The principle is not much different from slinging stones. SpinLaunch, a representative company of this method, has a technology that hangs a launch vehicle carrying a payload on a large arm, rotates it at high speed, and shoots it into the sky when it reaches a certain speed. According to currently available information, the speed at which the launch vehicle is thrown from the ground device exceeds 2 km per second, and the rocket is ignited when it reaches an altitude of 60 km to increase the speed to orbit. However, the problem is that centrifugal force cannot be avoided because the speed is increased through rotational movement. Additionally, the maximum centrifugal acceleration reaches 10,000g. Therefore, people can never ride it, and the payload inside it has no choice but to be designed stronger and heavier to withstand this centrifugal acceleration. Instead, according to the company’s explanation, launch costs can be implemented more than 20 times cheaper than currently. At first glance, anyone may seem to be able to make the throw easily, but it requires precise control technology to throw the projectile in the exit direction from the exact location after reaching the target speed. For reference, the throwing speed of 2km per second is much faster than a bullet or shell, so you can roughly imagine how important it is to have precise control technology to accurately release it while spinning at high speed. The concept of ‘shooting’ a projectile like a cannonball by accelerating in a straight line from the beginning, rather than converting the rotational motion into a straight line and throwing it, already appeared in Jules Verne’s novel ‘From the Earth to the Moon’ in the late 19th century. Since then, many detailed ideas have been developed at the laboratory level, but there are many constraints due to the need to withstand rapid acceleration close to shock during the launch process and the need for facilities that require a very long cannon. However, there is a lot of research being done on accelerating metal bullets or shells with electromagnetic waves rather than gunpowder, so the day when Bern’s imagination becomes a reality will come soon. This is a drawing created by the National Aeronautics and Space Administration (NASA) imagining a space elevator arrival station to be installed in a geostationary orbit at an altitude of 36,000 km. A space elevator is the ultimate solution that does not use NASA-provided rockets. It was designed with an extremely scientific idea by Konstantin Tsiolkovsky, a Russian space engineering pioneer. This concept later became popular when it appeared several times in the works of Arthur Clark, the master of science fiction novels. The most advanced construction method studied so far involves lowering ropes to Earth from beyond geostationary orbit rather than building them up from below. In other words, the principle is not to withstand an enormous weight from below, but to withstand tension from above. The problem is that so far, high-purity carbon nanotubes are the only material that can withstand the tension of a huge structure over 36,000 km long. There is still no way to make this high-purity carbon material in large enough quantities and long enough to be practical for use in space elevators. Although it is true that no practical method of escaping Earth’s gravity has yet emerged other than chemically propelled rockets, many challenges are still continuing in various parts of the Earth. Even for profit-seeking businesses, efforts to protect the global environment and realize wonderful dreams are still ongoing. Kim Sang-don, Starburst Korea Branch Manager ※ About the author Kim Sang-don, Starburst Korea Branch Manager, graduated from the Department of Aerospace Engineering at Seoul National University and received a master’s degree in aerodynamics from the same graduate school. He later worked at KAI for 12 years in aircraft development and international marketing, and later moved to France to run ‘VMTS’, a telecommunications company for mobile devices. Starting in 2010, he developed the gas turbine business for aircraft and ships at Rolls-Royce’s Korean branch for seven years. Since 2021, he has been working as the Korea branch manager for Starburst, a global aerospace accelerator and investment company. ※Related article Math Donga October, [Space Math] Shooting in the air, flinging stones, and launching eco-friendly rockets
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