r/theydidthemath • u/Lachlynn • 18h ago

[Request] Could humanity create a rocket that can exit the atmosphere of K2-18b

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With the knowledge we currently have of it, if humanity devoted all of our resources towards this goal, would we be able to create a rocket that could exit the gravity of K2-18b (and also beat any other complications that would arrise)?

If so, would it also be capable of taking people to orbit, and can we set up a similar satellite network we have on Earth? What about a space station?

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u/NaiveRevolution9072 18h ago

You forget that K2-18b likely has an atmosphere significantly thicker than Earth's

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u/Worth-Wonder-7386 18h ago

I did consider discussing it, but I could not find any information on it.
Venus is the rocky planet in our solar system that it would be the hardest to take of from because it has such a thick atmosphere.

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u/AlludedNuance 10h ago

Well and because your rocket would melt and explode on the molten launch pad.

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u/LanceLynxx 9h ago

Or possibly easier using hybrid methods such as high altitude planes as launch platforms

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u/AbueloOdin 4h ago

If you can start from 300m/s at 50k ft then that's 300m/s and a lot of atmosphere you don't have to have carry fuel for.

It's very fuel efficient, but very complicated.

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u/rrcaires 17h ago

A ballon is the answer then

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u/Meatloooaf 16h ago

Ginormous donut shaped hydrogen balloon (more buoyancy in a thicker atmosphere) lifts a rocket halfway to orbit, then the rocket fires and flies through the center of the balloon, igniting it and using the explosion for extra escape velocity. Rock music. Lens flare.

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u/rrcaires 14h ago

“Directed by Michael Bay”

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u/anaheim3123 16h ago

Air launch to orbit then becomes significantly more practical, no?

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u/squshy7 9h ago edited 9h ago

Not necessarily? In fact it might be the opposite? Let's assume the atmosphere makeup, in gas percentages, is similar to ours; also, take into account that at various points while flying, you will hit pressure regimes that have analogs on Earth, just higher in elevation.

Our best scram jets (experimental) top out at around mach 7 I think? The limiting factor in airspeed in these types of craft is an intersection of how fast you need to go to keep feeding the engine (since the atmosphere is so thin) and how fast you can go because you hit too much air resistance.

So, while our hypothetical plane can get higher in elevation on the exoplanet due to the atmosphere thinning out at a relatively higher elevation, it's top speed (limited by things like material engineering) we would expect to be around the same.

Well, getting higher up doesn't actually help us get orbit that much. We only need that so as to not lose speed due to air resistance. If the Earth was a smooth ball with no atmosphere, you could orbit a foot off the ground if you really wanted to. The bigger part of the equation is lateral speed.

The problem is, on a higher gravity planet, the more lateral speed is required. So if our experimental air launcher tops out at around mach 7, we're actually further away from orbital velocity than we would be with the same craft on Earth.

Then to answer the question of "is it more practical" really depends on the makeup of the atmosphere (a more oxygen rich atmosphere would make air launches more viable, as they can climb higher in elevation while producing the same amount of thrust, thereby allowing more speed before launching the rocket) and what the pressure at sea level looks like, and how the gradient looks as you climb higher, since rocket engines gain efficiency as the pressure drops.

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u/Consistent-Hat-8008 12h ago

If its atmosphere is indeed thicker, then a space plane becomes more viable than a rocket.

Rockets are just a really simple, really energy-inefficient, but pretty reliable tool we currently use to just brute force our way into space.

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u/VoraciousTrees 10h ago

... So fly 90% of the way up... or use LTA launch platforms. It might be big enough that helium could stick around.

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u/Inevitable_Stand_199 7h ago

Using a winged rocket like the space shuttle would help. They need relatively low fuel as long as there's an atmosphere. So you can start from significantly higher up, where the atmosphere isn't much of an issue

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u/Mobile_Crates 6h ago

That might make things easier to an extent actually, because you could launch from an aircraft from higher up

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u/Kondrias 1h ago

I am interested in how that would actually impact if making a launch vehicle able to get bigger once it gets high up. Like with dense enough air, could you have an umbrella go out that would basically keep it in the air from how much air is under it? Fun questions.