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Spaceship made of carbon foam bubbles could zoom from Earth to Alpha Centauri in 185 years, driven only by the power of the sun, finds a new study.
A swarm of these probes could help discover and study the mysterious solar system Planet nine, if this hypothetical world exists, the scientists added.
Conventional rockets driven by chemical reactions are currently the main form of space propulsion. However, they are not effective enough to reach another star in a human lifetime.
Related: Ultra-fast spacecraft propulsion concepts (images)
For example, Alpha Centauri, the closest star system to Earth, is about 4.37 light-years away – over 25.6 trillion miles (41.2 trillion kilometers), or about 276,000 times the size of distance from Earth to Sun. It would take NASA Voyager 1 Spaceship, which launched in 1977 and reached interstellar space in 2012, about 75,000 years to reach Alpha Centauri if the probe was headed in the right direction (which it did not).
The problem with all conventional spacecraft thrusters is that the thruster they use has mass. Long trips require a lot of thruster, which makes spaceships heavier, which in turn requires more thruster, making them heavier, etc. This problem worsens exponentially as the spacecraft gets bigger.
Previous research has therefore suggested that “light sail“may be one of the only technically feasible methods of getting a probe to another star in a human lifetime. Although light doesn’t exert much pressure, scientists have determined that what little it does apply could have a major effect, as many experiments have shown that “solar sails” can rely on sunlight for propulsion, given a sufficiently large mirror and a sufficiently light spacecraft.
The $ 100 million Revolutionary Starshot Initiative, which was announced in 2016, aims to launch swarms of microchip-sized spacecraft to Alpha Centauri, each sporting extraordinarily thin and incredibly reflective sails. The plan makes these “starches” fly at speeds up to 20% of the speed of light, reaching Alpha Centauri in about 20 years.
One downside to the Starshot Project is that it requires the most powerful laser array ever built to propel the starches outward. Not only does the technology to build this bay currently not exist, but the estimated total costs of the project could reach between $ 5 billion and $ 10 billion.
In the new study, astrophysicists suggested that a cheaper option could involve carbon foam bubbles. Probes made of this stuff could do interstellar travel faster than any rocket when powered solely by sunlight, without the need for a giant laser array, the researchers found.
In order to develop a way for sunlight to propel a light sail at useful interstellar speeds, the researchers analyzed previous scientific research looking for strong and light materials. They opted for aerographite, a carbon-based foam 15,000 times lighter than aluminum.
Scientists calculated that a hollow airbrush sphere about 3.3 feet (1 meter) in diameter with a shell 1 micron thick (about 1% of the width of an average human hair) would weigh than five millionths of a pound (2.3 milligrams).
Related: Starshot breakthrough in pictures: laser-navigating nanocraft to study alien planets
If such a sphere carrying 0.035 ounces (1 gram) of payload were released about one astronomical unit (AU) from the sun, sunlight would push it at a speed of up to about 114,000 mph (183,600 km / h) – three times that of Voyager 1. Such a sphere would take about 3.9 years to reach the orbit of Pluto. (One AU is the average Earth-Sun distance, which is approximately 93 million miles, or 150 million km.)
If such a sphere were released about 0.04 AU from the sun – closest to that of NASA Parker solar probe happens to our star – the more intense sunlight would accelerate the spacecraft to almost 15.4 million mph (24.8 million km / h). It could travel the distance of 4.2 light years from Earth to Proxima Centauri, the closest star to our solar system, in 185 years, the researchers say. The larger the sphere, the faster it can go or the more payload it can carry. (Proxima Centauri is one of the three stars of the Alpha Centauri system.)
“What I find amazing about our results is the fact that the output power of a star, in our case the sun, can be used to propel an interstellar probe to the nearest stars without the need for an additional power source on board, “he added. Author René Heller, an astrophysicist at the Max Planck Institute for Solar System Research in Göttingen, Germany, told Space.com.
“We don’t need a billion-dollar Earth laser array to shoot a sail in space,” Heller said. “Instead, we can use green energy, so to speak.”
The researchers noted that a few grams of electronics or other payload isn’t much to take on a mission. Still, they argued that the payload of such craft would be 10 times the mass of the spacecraft, while the payload of chemical interstellar rockets would typically be a thousandth of the rocket’s weight.
The researchers suggested that these spacecraft could potentially carry a 32-watt laser weighing only two thousandths of a pound (1 gram). Analyzing any disturbance to this laser beam could help researchers detect gravitational effects, which in turn could help reveal the presence of worlds otherwise too dark and too cold to spot, like the hypothetical Planet nine, Heller said.
Scientists have estimated that developing a prototype bubble ship could cost $ 1 million. They calculated that each foam ship could then be built for around $ 1,000 or less, and a rocket launch to deploy and test these craft could cost $ 10 million.
The biggest caveat with this work right now “is that no one has ever built an airbrush structure larger than a few inches, when we need something that’s a few feet tall,” said Heller. Yet the researchers are in contact with experimenters who suggest that the creation of such large structures is in principle possible, he noted.
Another point of caution about this concept is that there is currently no way to control the trajectory of the spheres once they are deployed. “In order to achieve a certain goal, this has to be rectified,” Heller said.
If the electronics and on-board equipment could allow active maneuvers, “then it might be possible to transport small masses – 1 to 100 grams – between Earth and Mars in a matter of weeks,” Heller said.
Scientists envision conventional rockets bringing the bubble ship into space, then deploying them to propel sunlight. It remains uncertain to what extent these bubbles would survive transport.
“A good thing about airbrush is its compressibility,” Heller said. “Even after extreme compression, an airbrush sample can re-inflate to its original state. So if we compress a meter-long airbrush sail in the lab, maybe we can ship it to space. and pump it back up there before launch. The question is, what happens to its on-board electronics? “
Scientists are currently running experiments to test how well airbrush absorbs and reflects light. They detailed their discoveries online July 7 in the journal Astronomy & Astrophysics.
Follow Charles Q. Choi on Twitter @cqchoi. Follow us on Twitter @Spacedotcom and on Facebook.
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