wow 50 light years is indeed "nearby" in relative terms

nearly 6x the size of earth though, good luck trying to launch a probe off that surface

NASA has a neat "exoplanet catalog" which is about to leap in size next few years with new telescopes and techniques

* https://science.nasa.gov/exoplanet-catalog/lhs-1140-b/

6x time size (diameter?) or 6 times the mass. Evidently the Earth used to be much larger in size but not mass because of large amounts of trapped hydrogen/helium. It's since leaked from the crust and been blown off into space.

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ck2 7 hours ago | parent [-]

the catalog says 6.38x mass in one place and 5.6x mass in another

they must be able to calculate mass from orbital physics?

so you'd need a rocket 6x the size of SaturnV or whatever they are using for Artemis to escape it and most of that rocket is to lift the weight of the fuel for said rocket so it might be physically impossible to build such a creature at current level of tech

(might be yet another angle to "why no ETs" unless they are WAY more advanced)

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inigyou 7 hours ago | parent | next [-]

√(G × mass÷radius) [escape velocity] = v_e × ln(m_0 ÷ m_f) [Tsiolkovsky]

Impossible to tell how much extra mass you need but it's exponential. Adding a unit of v_e [effective exhaust velocity] to escape velocity means you need 2.717 times as much fuel in an ideal rocket.

Earth escape velocity is 11000m/s ignoring atmosphere (which is not ignorable). If the new planet is 6x mass and 2x radius then √3 times escape velocity (about 1.73) would be about 8000m/s extra velocity which is about 3 times a random v_e which means you need about a 25 times bigger rocket. Ignoring the denser atmosphere which makes it even worse.

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shagie 7 hours ago | parent | next [-]

From the archives ... How much bigger could Earth be before rockets wouldn't work? https://space.stackexchange.com/q/14383 Feb 3, 2024 https://news.ycombinator.com/item?id=39243303

https://physics.stackexchange.com/questions/117347/when-a-pl...

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hgoel 6 hours ago | parent | prev [-]

Don't these estimates assume launching from the surface, fully via rocket? On Earth, having air breathing stages to gradually build up speed, or using other launch mechanisms, isn't worthwhile because rockets are more cost effective here, but those tradeoffs change if you're on a planet with higher gravity and a denser atmosphere.

	▲	dogma1138 5 hours ago \| parent [-]
		You still need to get to escape velocity that doesn’t change the delta v required does but not by that much you are looking at 5-10%. Maybe a bit more if the atmosphere is really really thick. Unless you skip chemical rockets altogether there is a pretty hard cap on how much bigger a planet can be than earth before a space capable civilization becomes almost impossible.

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7 hours ago | parent | prev [-]

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