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Halo Drive: Lasers and black holes could launch spaceships at near light speed

Future spaceships could use black holes as powerful launch pads to explore the stars.

A new study envisages firing laser beams that curl around a black hole and come back with extra energy to bring a spacecraft near the speed of light. Astronomers may be looking for evidence that alien civilizations use such a "halo drive" as the study names them, looking into whether pairs of black holes merge more often than expected.

Study author David Kipping, an astrophysicist at Columbia University, New York, came up with the idea of ​​the halo drive by what he calls "the player's mindset."

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9659002] "Sometimes you find in a computer game an" exploit, "a hack that allows you to do something overwhelming, otherwise by the rules of the game prohibited, "Kipping told Space.com. "In this case, the game is the physical world and I've been trying to think about exploits that would allow a civilization to make a relativistic flight through the galaxy without the enormous energy costs that one could naively assume. "

A The main challenge for the use of rockets to fly through space is that has the propellant mass carried along with it. Long trips require a lot of fuel, which makes the rockets heavy, which in turn requires more fuel, making the rockets even heavier, and so on. This problem becomes more exponential as the missile gets bigger.

Instead of driving propellants to drive, however, spacecraft equipped with mirror-like sails could rely on lasers to push them outward. Announced in 2016, the Breakthrough Starshot Initiative (19459006), announced in 2016, aims to use powerful lasers to propel flocks of spacecraft up to 20 percent of the speed of light to Alpha Centauri, the nearest star system of ours. 19659002] The spacecraft Breakthrough Starshot is about to launch is about the size of a microchip. To accelerate larger spaceships to relativistic speeds – at a significant fraction of the speed of light – Kipping sought the help of gravity.

Spaceships now regularly use "skid maneuvers" in which the gravitational force of a body, such as a planet or a planet, is lying Moon launches the ships across space and increases their speed. In 1963, the well-known physicist Freeman Dyson suggested that spaceships of any size could rely on skid maneuvers around compact pairs of white dwarfs or neutron stars to fly at relativistic speeds. (Dyson came up with the idea of ​​a so-called Dyson Sphere ), a megastructure that includes a star to capture as much energy as possible for an advanced civilization.

a Dyson Slingshot is in danger of being damaged by extreme gravitational forces and dangerous radiation from these pairs of stars. Instead, Kipping suggests that gravity could help spaceships by increasing the energy of laser beams fired at the edges of black holes.

Black holes have gravitational fields that are so strong that nothing escapes them when they are not close enough, not even light. Their gravitational fields can also distort the paths of photons of light that do not fall into the holes.

Physicist Mark Stuckey proposed in 1993 that a black hole could, in principle, act like a "gravity mirror". The gravity of the black hole could spin a photon around it, causing it to fly back to its source. Kipping calculated that if a black hole moved towards the source of a photon, the "Boomerang photon" would skim off some of the energy of the black hole.

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With his so-called "Halo Drive" – ​​named after the ring of light he has around black hole – Kipping found that even spaceships with the mass of Jupiter could reach relativistic speeds. "A civilization could exploit black holes as galactic waypoints," he wrote a study that was accepted by the Journal of the British Interplanetary Society and detailed on February 28 in the arXiv Preprint Server.

Black hole moves the more energy a halo engine can pull out of it. Therefore, Kipping focused mainly on using pairs of black holes, which face each other spirally towards each other before a merger.

Astronomers may be looking for evidence that alien civilizations use pairs of black holes to travel with such an engine. For example, halo drives would effectively steal energy from such binary black hole systems thereby increasing the speed with which pairs of black holes go beyond what one naturally expects, Kipping said.

His findings were based on boosts of black hole pairs orbiting at relativistic velocities. Although there are an estimated 10 million pairs of black holes in the Milky Way, Kipping found that only a few of them would likely orbit relatively quickly at relativistic speeds, as they would unite quickly. However, he noted that sporadic, spinning black holes could also trigger relativistic-speed halo drives, "and we already know numerous examples of relativistic, spinning supermassive black holes."

The biggest drawback of a Halo drive would be that "you have to travel to the nearest black hole," Kipping said. "It's almost like paying a one-time toll to drive the highway system, you have to pay some energy to get to the next access point, but after that you can drive for free as long as you like."

The halo drive operates only in the immediate vicinity of a black hole, at a distance of about 5 to 50 times the diameter of the black hole. "That's why you have to travel to the nearest black hole first, and [why you] can not do that over light years," Kipping said. "We still need a means to travel to nearby stars to navigate the freeway system.

" If we want to achieve a relativistic flight, energy consumption is immense, regardless of the drive system used, "he added To circumvent this, use astronomical objects as a source of power, since they literally have astronomical energy levels in which case the black hole binary is essentially a huge battery waiting to knock with it The idea is to work with nature and not to oppose it. "

Kipping is exploring ways to use other astronomical systems for the relativistic flight. Such techniques "may not be as efficient or fast as the Halo Drive approach, but these systems have the deep energy reserves required for these trips," Kipping said.

Follow Charles Q. Choi on Twitter @cqchoi . Follow us on Twitter @SpaceTotcom and Facebook .

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