Introduction: Using the energy generated by nuclear fusion as a driving force can greatly increase the speed of interstellar travel.
When exploring space, the speed of light is a big limitation. The speed of light refers to the speed at which light travels in a vacuum, precisely 186,282 miles per second (29,972,458 meters per second, or 300,000 kilometers per second). The speed of light is constant. As far as humans know, nothing can exceed the speed of light. Moving at 300,000 kilometers per second may seem fast, but compared to the vast cosmic space, it's no different than trekking through syrup.
To get a better idea of the speed of light, here are some interesting facts that will help us understand how fast the speed of light can be. The Moon is about 238,855 miles (384,400 km) from Earth; It takes about 2.51 seconds for light to travel back and forth from Earth. It takes 3 minutes and 2 seconds to reach Mars, and 6 minutes and 4 seconds to get to Mars. It takes a beam of light 4.6 hours to reach Pluto and another 4.6 hours to return. Finally, if traveling at the speed of light, it will take 4.24 years to reach Alpha Centauri, the closest planet to Earth, which is already the fastest speed.
Too slow!
Unfortunately, technology has not yet developed enough to propel a spacecraft equipped with astronauts through space at the speed of light. If our technology allows us to do so, astronauts will experience time in a strange way; For astronauts, the speed at which they experience time seems to flow differently than on Earth. For example, a 5-year trip on a spacecraft at 99% of the speed of light is equivalent to about 50 years on Earth. Einstein's special theory of relativity, however, tells us that there are some hurdles to overcome before humans can achieve light-speed travel.
Once an object reaches the speed of light, its mass becomes infinitely large. In order to push this infinitely heavy object, it naturally requires unlimited energy. This universal law effectively limits the speed at which objects move. In order to create an object that can travel at the speed of light or faster, we need to change the laws of physics to achieve it.
Cutting edge of science and technology
Some of the world's top astrophysicists have been working on how to solve this problem, proposing many different theoretical engines and propellants that could drive objects to move at the speed of light. One of the most promising devices is the use of nuclear fusion energy to drastically reduce travel time. Physicists involved in the project estimate that the technology could shorten the travel time to reach Titan, one of the most interesting places in the solar system (about 1 billion miles from Earth) to two years!
This conceptual technique is called Direct Fusion Drive (DFD). The technique relies on the energy generated by a reaction similar to nuclear fusion in the sun's interior to drive objects. Scientists have begun to find ways to harness the thermal and energetic by-products of nuclear reactions to generate electricity. Scientists are said to be about to release the first commercial fusion reactor.
Nuclear fusion dynamics have long been a research hotspot for astrophysicists and engineers working to develop spaceflight technology. Fusion reactors are essentially the use of energy released by the combination of two lighter atoms into a heavier nucleus, a process that takes place in the center of the star. This technology is like preserving the enormous energy of a hydrogen bomb explosion in some form — and the hydrogen bomb is powered by the aggregation of hydrogen isotopes at extremely high temperatures to form helium, and the huge amount of energy generated in the process to propel you through space. That's exciting, right?
Of course, there's a reason the world isn't powered by fusion reactors. They are an ideal source of energy because nuclear fusion reactors are theoretically more stable than nuclear fission reactors, so there is less risk of meltdowns like the Chernobyl and Fukushima nuclear disasters. Second, fusion reactors do not produce nuclear waste or toxic by-products. But the problems caused by fusion reactions are also very difficult. In order for the reaction to begin, we need to heat the hydrogen to a temperature of 6 times more than the sun's core, or 100 million degrees Celsius. This is so hot that the material used to build the reactor is kept firm for months at extremely high temperatures and pressures of high-temperature plasmas (active ions and free electrons composed of ionized gases at very high temperatures). This poses a huge challenge to building materials.
Direct fusion device
But not all hopes are dashed. Physicists are now working on something that was once considered nearly impossible: direct fusion drives (DFDs). In fact, scientists at Princeton's Plasma Physics Laboratory have been working on a way to shorten the travel time to Titan, arguably Saturn's most interesting moon, to as little as two years. The device is known as the Princeton Field Reversed Configuration-2 Reactor. The researchers hope it will one day become the primary device for launching satellites and probes into space and carrying the burden of carrying humans through space.
A 2019 developer at Princeton Plasma Physics Laboratory, said: "DFD employs a unique plasma heating system to achieve a nuclear fusion engine in the range of 1 to 10 megawatts. This engine is best suited for human exploration of the solar system, robotic solar system missions, and interstellar missions. ”
A October 2020 press release read: "The engine itself takes advantage of many of the advantages of neutron-free fusion, the most notable of which is the extremely high power-to-weight ratio. "The DFD-driven fuel can vary slightly in mass and contains the deuterium and helium-3 isotopes." Essentially, the DFD incorporates the excellent specific impulse of an electric propulsion system and combines it with the excellent thrust of a chemical rocket, thus fusing the advantages of both flight systems. ”
The Reverse Field Reactor (FRC Reactor) employs linear solenoids, magnetic coil arrays to limit plasma and can operate at higher plasma pressures than other designs allow, providing a higher fusion power density than other magnetically constrained plasma devices at a given magnetic field strength.
In general, nuclear fusion systems are considered the best option for interstellar missions because they use hydrogen as fuel, and hydrogen happens to be the most abundant element in the universe, so the spacecraft does not need a lot of gas to replenish fuel. This is also useful for detectors. Unfortunately, with current technology, the 2 billion miles between Earth and Saturn, the probe will take about 7 years to reach. Launched in 1997, the famous Cassini-Huygens probe reached its destination in 2004 at a speed of 42,500 mph (68,397 km/h) and encountered temperatures between 130 degrees Celsius and -210 degrees Celsius. New Horizons' first mission was Pluto, and it took nearly 10 years to complete the journey.
Interestingly, it is important for astronomers to consider the arrangement of the planets when launching a probe. For example, the Cassini-Huygens probe was launched during a period of time when Venus was relatively close to Earth. It travels from Earth to Venus, back to Earth, to Jupiter, and then to Saturn. With each passing planet, the probe was able to get a little gravitational help from each planet, which increased Cassini's speed.
To map the best route to Saturn's largest moon, the Italian team worked with DFD developers at princeton's Plasma Physics Laboratory and was given access to performance data from the test engine. They then extracted some data on the arrangement of the planets and began studying orbital mechanics. They developed two different possible paths, one to apply a constant thrust only at the beginning and end of the journey, and the other to keep the thrust constant throughout the journey. ”
Both schemes require a shift in thrust direction to slow the ship down into the Saturn system. If a constant thrust is provided, the journey will take less than two years, and simply applying thrust at the beginning and end of the journey could shorten the total journey time of a much larger spacecraft than Cassini to 2.6 years. Neither path requires the help of gravity, and spacecraft traveling to exoplanets often benefit from gravity. ”
If this device doesn't work out, there are several other devices in the works, but this is still one of the most promising ideas. However, since the next ideal window to Titan is in 2046, researchers have about 30 years to perfect the DFD technology.
BY: Jaime Trosper
FY: LUMEN
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