Future spaces could use black holes as powerful launch pads to explore the stars.
A new study envisions laser beams that would curve around a black hole and come back with added energy to help propel a spacecraft to near the speed of light. Astronomers could look for signs that alien civilizations are using such a "halo drive," as the study dubs it, by seeing if pairs of black holes are merging more than expected.
Study author David Kipping, an astrophysicist at Columbia University in New York, came up with the idea of the halo drive through what he calls "the gamer's mindset."
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A the challenge is to use rockets to fly through space is the propellant they carry with them has mass. Long trips need a lot of propellant, which makes the rockets heavy, which in turn requires more propellant, making the rockets even heavier, and so on. That problem gets exponentially worse the bigger the rocket gets. Instead of carrying propellant for propulsion, however, spacecraft equipped with mirror-like sails could rely on lasers to push themes outward. The $ 100 Million Breakthrough Starshot Initiative announced in 2016, plans to use powerful lasers to propel swarms of spacecraft to Alpha Centauri, the closest star system to our own, up to 20 percent the speed of light. 19659002] The spacecraft that Breakthrough Starshot aims to launch each and every one of the size of a microchip. In order to accelerate larger spaceships to relativistic speeds – to a significant fraction of light speed – Kipping the aid of gravity.
Spacecraft now regularly use "slingshot maneuvers," in which the gravity of a body, such as a planet or moon, hurls the vessels across space and boosts their speed. In 1963, famed physicist Freeman Dyson suggested that spaces of any size could rely on slingshot maneuvers around compact pairs of white dwarfs or neutron stars to fly at relativistic speeds. (Dyson came up with the notion of what became known as a Dyson sphere a megastructure that encapsulates a star to capture as much of its energy as possible to power and advanced civilization.)
However, a "Dyson slingshot" runs the risk of damaging a spacecraft through extreme gravity forces and hazardous radiation from those pairs of dead stars. Instead, Kipping suggests that gravity might assist spaces by increasing the energy of laser beams fired at the edges of black holes.
Black holes possess gravitational fields such that nothing can escape them once it gets close enough, not even light. Their gravitational fields can also distort the paths of photons of light that do not fall into the holes.
In 1993, physicist Mark Stuckey suggested that a black hole could, in principle, act as a "gravitational mirror," in that the black hole's gravity could slingshot a photon around so that it was back at its source. Kipping calculated as a black hole was moving toward a photon's source, the "boomerang photon" would siphon away some of the black hole's energy.
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Using what he called a "halo drive" – named for the ring of light it would create around a black hole – Kipping found that even spaces with the mass of Jupiter could achieve relativistic speeds. "A civilization could exploit black holes as galactic waypoints," he wrote in a study accepted by the Journal of the British Interplanetary Society and detailed online. 28 in the arXiv preprint server
The faster a black hole moves, the more energy a halo drive could draw from it. As such, Kipping is focused on using pairs of black holes spiraling toward each other before a merger.
Astronomers can look for signs that are civilizations are exploiting pairs of black holes for travel with such an engine. For example, halo drives would effectively steal energy from such binary black hole systems increasing the rates at which pairs of black holes merge above what one would expect to see naturally,
His findings were based on boosts from pairs of black holes orbiting each other to relativistic speeds. Although there are an estimated 10 million pairs of black holes in the Milky Way, Kipping noted that many of them probably orbited at relativistic speeds for long, since they would merge rather quickly.
Still, it was noted that isolated, spinning black holes could also be launched at relativistic speeds, "and we already know of numerous examples of relativistic, spinning supermassive black holes."
The major drawback of a halo drive would be that "one has to travel to the nearest black hole," Kipping said. "It's time to pay a one-time toll fee to ride the highway system. energy to reach the nearest access point, but after that, you can ride for free as long as you like. "
The halo drive works only in close proximity to a black hole, at a distance of about five to 50 times the black hole's diameter. "This is why you have to travel to the nearest black hole first and [why you] you can simply do this across light-years of space," Kipping said. highway system.
"If we want to achieve relativistic flight, it takes immense energy levels no matter what propulsion system you use," he added. "One way to get around this is to use astronomical objects as your power source, since they possess literally astronomical levels of energy within them. In this case, the black-hole binary is essentially a battery waiting for us to lose it. The idea is to work with nature and not against it. "
Kipping is now investigating ways to exploit other astronomical systems for relativistic flight. Such techniques" may not be quite as efficient or fast as the halo-drive approach, but these systems have the deep energy reserves needed for these journeys, "Kipping said.