Post by dividavi on Dec 11, 2021 1:17:24 GMT
This thread you're reading right now is a partial reaction to the earlier thread Excuses for Why Humans Haven't Found Aliens Yet. It seems that the Earth is in the proper location and of the proper size to permit space exploration with chemically powered craft. Other civilizations might be trapped on their home planets due to the vastly greater difficulty of achieving escape velocity. I got the following paragraphs from the clickable article titled The Challenges of an Alien Spaceflight Program: Escaping Super Earths and Red Dwarf Stars.
Click on www.universetoday.com/139052/the-challenges-of-an-alien-spaceflight-program-escaping-super-earths-and-red-dwarf-stars/ to find out more.
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 and Hippke, respectively. 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.
As Prof. Loeb told Universe Today via email:
“Chemical propulsion requires a fuel mass that grows exponentially with terminal speed. By a fortunate coincidence the escape speed from the orbit of the Earth around the Sun is at the limit of attainable speed by chemical rockets. But the habitable zone around fainter stars is closer in, making it much more challenging for chemical rockets to escape from the deeper gravitational pit there.”
“Chemical propulsion requires a fuel mass that grows exponentially with terminal speed. By a fortunate coincidence the escape speed from the orbit of the Earth around the Sun is at the limit of attainable speed by chemical rockets. But the habitable zone around fainter stars is closer in, making it much more challenging for chemical rockets to escape from the deeper gravitational pit there.”
“The nearest star to the Sun, Proxima Centauri, is an example for a faint star with only 12% of the mass of the Sun,” he said. “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. At that location, the escape speed is 50% larger than from the orbit of the Earth around the Sun. A civilization on Proxima b will find it difficult to escape from their location to interstellar space with chemical rockets.”
