"To lift a more useful payload of 6.2 t as required for the James Webb Space Telescope on Kepler-20 b, the fuel mass would increase to 55,000 t, about the mass of the largest ocean battleships," he writes. To put it into perspective, Hippke considers specific payloads being launched from Earth. As a result, a single-stage rocket on Kepler-20 b would have to burn 104 times as much fuel as a rocket on Earth to get into orbit. Whereas escape velocity from Earth is roughly 11 km/s, a rocket attempting to leave a Super-Earth similar to Kepler-20 b would need to achieve an escape velocity of ~27.1 km/s. "Rockets suffer from the Tsiolkovsky (1903) equation : if a rocket carries its own fuel, the ratio of total rocket mass versus final velocity is an exponential function, making high speeds (or heavy payloads) increasingly expensive."įor comparison, Hippke uses Kepler-20 b, a Super-Earth located 950 light years away that is 1.6 times Earth's radius and 9.7 times it mass. As Hippke indicated in his study:Īrtists impression of a Super-Earth, a class of planet that has many times the mass of Earth, but less than a Uranus or Neptune-sized planet. However, when it comes to rocket launches, increased surface gravity would also mean a higher escape velocity. In addition, a planet with higher gravity would have a flatter topography, resulting in archipelagos instead of continents and shallower oceans – an ideal situation where biodiversity is concerned. For instance, planets that are more massive than Earth would have higher surface gravity, which means they would be able to hold onto a thicker atmosphere, which would provide greater shielding against harmful cosmic rays and solar radiation. Hippke's paper, on the other hand, begins by considering that Earth may in fact not be the most habitable type of planet in our universe. A civilization on Proxima b will find it difficult to escape from their location to interstellar space with chemical rockets." At that location, the escape speed is 50 percent larger than from the orbit of the Earth around the sun. "A couple of years ago, it was discovered that this star has an Earth-size planet, Proxima b, in its habitable zone, which is 20 times closer than the separation of the Earth from the sun. "The nearest star to the sun, Proxima Centauri, is an example for a faint star with only 12 percent of the mass of the sun," he said. Using the nearest star to our own as an example (Proxima Centauri), Loeb explains how a rocket using chemical propellant would have a much harder time achieving escape velocity from a planet located within it's habitable zone. This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Similarly, the escape velocity needed to get away from the location of the Earth around the sun is about 42 km/s (151,200 km/h 93,951 mph). Essentially, if a rocket is to escape from the Earth's surface and reach space, it needs to achieve an escape velocity of 11.186 km/s (40,270 km/h 25,020 mph). Whereas Loeb addresses the challenges of chemical rockets escaping Proxima b, Hippke considers whether or not the same rockets would able to achieve escape velocity at all.įor the sake of his study, Loeb considered how we humans are fortunate enough to live on a planet that is well-suited for space launches. The papers, tiled "Interstellar Escape from Proxima b is Barely Possible with Chemical Rockets" and "Spaceflight from Super-Earths is difficult" recently appeared online, and were authored by Prof. ![]() Loeb looks at the challenges extra-terrestrials would face launching rockets from Proxima b, Hippke considers whether aliens living on a Super-Earth would be able to get into space. Harvard Professor Abraham Loeb and Michael Hippke, an independent researcher affiliated with the Sonneberg Observatory, both addressed this question in two recently–released papers.
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