New photonic devices are about to allow the next jump in the exploration of deep space

Imagine a very small spacecraft powered by a laser light capable of reaching speeds greater than a quarter of the speed of light, and this, quickly enough to reach the closest star to our system solar in the next 20 years, or something closer to you, like sending people to Mars a month. By harnessing photonic-based propulsion, researchers are in the process of achieving this seemingly impossible achievement of science fiction, said Lubin, a professor of physics at the University of California at Santa Barbara.

The results of the research described by Lubin will come from NASA's Starlight and Breakthrough Starshot programs, both of which support advanced photonics research. Lubin is director of the Starlight program.

"Photonics, light production and manipulation are already part of our everyday life – from cell phones to computers to light-emitting diode (LED) bulbs and fiber optics carrying your data everywhere – not even seeing it. "said Lubin. "You can cite concrete examples of photonics in everyday life, which apparently has nothing to do with interstellar flight, but it is, because it is synergistic with the technology you need to to make an interstellar flight. "

According to Lubin, one of the biggest challenges in validating this concept of photonics with respect to propulsion is the demonstration of the laser power required to accelerate the hypothetical proposed / hypothetical vehicle.

Synthetic optics for directed energy propulsion systems

The high-energy directed systems are not built with the help of a single gigantic laser, but rely on the combination of beams, which involves the use of many very modest power laser amplifiers.

"Our system relies on an established typology called master oscillator power amplifier design," Lubin said. "This is a distributed system, so that every" building block "of a laser amplifier is between 10 and 1000 Watts.You can hold it in your hand.Instead of building a gigantic laser, you combine many small laser amplifiers that, when combined, form an extremely powerful and revolutionary system. "

Lubin suggests an badogy with supercomputers, which use a large number of central processing units (CPUs). "By consistently combining billions of low base layer laser power amplifiers, similar to the same power as a clbadic domestic LED, you suddenly get that incredibly capable managed energy system." , did he declare.

Interstellar probes powered by laser light

Directed energy systems can allow the use of interstellar probes as part of human exploration in the not too distant future. They are at the heart of the NASA Starlight program and the Breakthrough Starshot Initiative to enable the first interstellar missions of humanity. The same basic technology has many other applications, such as rapid interplanetary movement for large-scale missions, including those carrying people; planetary defense; and the search for an extraterrestrial intelligence (SETI).

"Our main focus is currently very small robotic spacecraft, they will not carry humans, it's not the purpose of the interstellar part of our program," Lubin said. "If humanity wants to explore other worlds outside of our solar system, there is no other propulsion option that can be physically obtained to do it, with two exceptions.

"One solution would be to master a technological approach known as the antimatter annihilation engine, which is a theoretical propulsion system that generates an energy-driven thrust released by the interactions at the level of the engine. Subatomic particles, but we currently have no way of doing this, "said Lubin," and this involves a number of complexities that we do not have a current path to resolve.

"The other option is directed energy or photonic propulsion, the one we focus on as it seems feasible," Lubin said. In a variant, the directed energy propulsion is similar to using the force of the water of a watering hose to push a ball towards the front. Tiny interstellar spacecraft (usually less than a kilogram, some of which are spacecraft on a platelet) can be propelled and directed via laser light, he said.

"The miniaturization of spacecraft is not required for every mission scenario we envision, but the lower its mbad, the faster you can go," Lubin said. "This system evolves differently from ordinary mbad-ejection propulsion."

Until now, all Earth's rockets are based on chemical propulsion systems whose basic design dates back to the Second World War. They are barely able to pull it out of the Earth's surface and into orbit. Making a bigger rocket does not make it faster, it just allows the rocket to carry more mbad. Photonic propulsion works differently, because the lower the payload, the faster you go. So, you want to reduce the mbad to go faster.

Like driving in a rain storm, in space

A major challenge for relativistic spacecraft is the hardening of radiation, because "when we start to reach velocities close to the speed of light, particles of interstellar space, protons in particular, in which you dive – ignore dust grains at the moment – are: primary source of radiation, "said Lubin." The space is not empty; it contains approximately one proton and one electron per cubic centimeter, as well as a handful of helium and other atoms. "

The penetration of these particles can be significant at high speed because, even if they move slowly in their own frame of reference, they cause high-speed impacts in the case of fast-moving spacecraft.

"When you hit them, you have the impression of driving in the pouring rain.Even if the rain falls directly from the sky, your windshield is stuck because you're going fast – and that's a pretty good effect serious for us, "said Lubin. "We are getting huge loads of radiation on the leading edge while the front is completely clogged, while the rest of the probe that is not the front edge and which is facing in different directions is not affected at all.It is an interesting and unique problem and we are working on what happens when you cross them. "

As for the implementation schedule for the guided energy propulsion technology, "we are doing laboratory demonstrations of every part of the system," said Lubin. "Full capacity is in over 20 years, although demonstration missions are achievable in a decade."

Arrive on Mars quickly

The same basic photonics technology from NASA's Starlight program also allows for extremely fast interplanetary missions, including Mars missions that can carry people in a minimum of one month. This would greatly reduce the dangers to humans during the long trip to the red planet and is currently under study as an option.

Trillion Planet Survey

Advances in photonics also mean that we can now leave light on the extraterrestrial intelligence of the universe if we want to be found – if there is another intelligent life that also wants to know the answer to the question "Are we alone"?

Lubin students are exploring this concept as part of their "Trillion Planet Survey" experience. This experiment is now actively looking for the neighboring galaxy Andromeda, which has about a trillion planets, as well as other galaxies and ours, looking for light signals.

By combining Lubin's research with the experience of his students, there are opportunities to report life. When technological advances allow the demonstration of lasers powerful enough to propel tiny spacecraft, these lasers could also be used to direct a lighthouse to the Andromeda galaxy in the hope that any life form can discover them there. and detect this light source in the sky. .

The opposite case is more interesting. Perhaps another civilization exists with a capacity similar to what we are currently developing in photonics. They may realize, like us, that photonics is an extremely effective way of detecting great distances, far from our galaxy. If there is an extraterrestrial civilization that diffuses its presence via optical beams, such as those proposed for photonic propulsion, they can be detected by a large-scale optical survey such as the team's Trillion Planet Survey. of Lubin.

"If the transmission wavelength of an extraterrestrial beam is detectable and that it has been lit up long enough, we should be able to detect the signal from a source located n '. anywhere in our galaxy or nearby galaxies with relatively small telescopes on Earth, even if no "party" knows that the other exists and does not know "where to point," said Lubin.This "blind-blind" scenario is the key to "directed intelligence research" as this Lubin strategy is called.

Planetary Defense

One of the most intriguing uses of photonics – closer to home – is to capture it to better defend the Earth against external threats such as asteroid and comet strikes.

The same system that researchers are beginning to develop for propulsion can be used for planetary defense by focusing the beam on the asteroid or comet. This damages the surface and, when parts of the surface are ejected during the reaction with the laser light, the momentum would push the debris in one direction and the asteroid or comet in the opposite direction. So, little by little, it will deflect the threat, said Lubin.

"The long-term implications for humanity are very important," he added. "Although most asteroid threats are not existential threats, they can be quite dangerous, as we saw in Chelyabinsk in Russia in 2013 and in Tunguska in Russia in 1908. Unfortunately, Dinosaurs lacked photonics to prevent their disappearance, and perhaps we will be wiser. "

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