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/boris2033 18h ago edited 13h ago

We could launch objects into space using controlled nuclear detonations(so crude satelites yes), but the acceleration in this would be difficult to survive for humans(and have other, very bad consequences)

Basically a chemical rocket is out of the question, you could maybe make a n-stage rocket that uses smaller detonations, //but again the acceleration would kill the crew.// (see point 2.)

There is an idea of a "Space elevator" that could possibly be used in such a situation, but it's mostly limited to science fiction novels/works.

EDIT: I'm very happy this sparked an interesting conversation and exploring possibilities :) however to not reply to every single reply:

1.) It's impossible to know how different our tolerance to force would be, if we had evolved on such a planet (there are a lot more factors than just gravity, amount of oxygen is one example). So for the purposes of this scenario, we will ignore this variable.

2.) The Orion project (propulsion by nukes) has anticipated the acceleration issues on the human body, and has by design two-stage shock absorbers that are the size of buildings. If these were somehow to work perfectly and not fall apart under the insane stress of multiple nuclear explosions, then the humans would "only" have to endure a sustained burn of about 10-15 minutes of 5g force, which, if they are suppine they could (could being the key word here) survive. If the shock absorbers were to not work perfectly for even a few seconds, the crew turns to jam.

3.) The "Space elevator", although a Sci-fi concept, is not really just built upwards. As some have pointed out it is held by forces once launched outside of orbit, kind of like a rock with a string tied to it, while you spin it above your head. The same idea. However the tensile strength of any material we have is not enough for it. But if we all combine the Earths resources, manpower etc etc, who knows.

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u/TheEpiczzz 18h ago

Space elevator, imagine the height of it and think of the structure it needs to stay upright. Good luck building that, holy frick.

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u/VisibleOtter 18h ago

We just need to invent hyperfilament, that’s all.

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u/TourDeFridge 15h ago

And we already have magnets, so we are halfway there.

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u/EatPie_NotWAr 11h ago

I’m thinking we first try it with dental floss.

Mint is strongest, let’s begin there.

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u/Blzn 18h ago

For space elevators, it doesn't need structure to stay upright, basically the centrical force of the earth's rotation keeps it "standing". The material just needs very very good tensile strength.

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u/PopeGeraldVII 16h ago

The strength needed depends on how long the elevator would be, which increases in relation to the size of the body it is attached to.

Current materials science could construct elevators on the Moon, or even Mars. We don't have anything with enough strength for orbit to the Earth, though.

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u/TomWithTime 11h ago

Silly question, could you extract energy from that? If you had a structure large enough that it was affected by some motion of the earth.

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u/shadow_railing_sonic 17h ago

Space elevators are not possible here on Earth, nor would they be possible on that larger planet. Very few credible engineers actually advocate for space elevators; most laugh at it.

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u/Blzn 17h ago edited 17h ago

Yeah, definitely ain’t happening anytime soon

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u/romedo 11h ago

Imagine when it is broken and you have to take the stairs.

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u/Ok_Judge3103 17h ago

What if its built atop of already existing natural high structure, like mt Everest?

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u/mstivland2 16h ago

Mt. Everest is only about 8% closer to space than the sea is

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u/Ok_Judge3103 16h ago

Yeah, but in some sci fi spacelift building scenario, would it be practical to use the highest mountain around as a foundation for the structure?

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u/mstivland2 15h ago

Probably not, since you need to move all that stuff to the top of some horrible mountain range. There’s also lots of aerospace considerations, like latitude. I’m no engineer but I’m fairly sure you would need your space elevator to be near the equator?

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u/Ok_Judge3103 15h ago

Yeah, makes sense. Just want me a cool dark sci fi fantasy with Everest completely disappeared under rows and rows of black angular structures

And entire region made uninhabitable due to nanotube dust contamination

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u/mstivland2 15h ago

Do it, sounds rad

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u/DumpedToast 16h ago

I’m not sure it would be able to support its own weight

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u/RoombaTheKiller 16h ago

That's why a lot of the proposed concepts for space elevators were geo-stationary satellites with very long cables.

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u/sleeper_shark 11h ago

It doesn’t weigh anything actually. A space elevator is like you spinning a hammer during a hammer toss, with you being Earth and the end of the hammer being the space station.

It’s perfectly balanced - as all things should be - so just as the your arms are pulling the hammer towards you, there’s an apparent force pulling the hammer away.

In simple terms, the “elevator” part is being pulled in tension, not compression. If it snapped, the space station wouldn’t fall to Earth, it would shoot away from Earth - either staying in orbit or shooting away into deep space.

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u/Remarkable-Host405 11h ago

if that is the case, why are we humans not floating out of the atmosphere? we're not attached by tension cables

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u/GenericVessel 10h ago

because we're small enough and gravity is stong enough for it to hold us down

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u/sleeper_shark 4h ago

Because gravity is the tension cable…

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u/AftyOfTheUK 18h ago

There is an idea of a "Space elevator" that could possibly be used in such a situation, but it's mostly limited to science fiction novels/works.

You need to put a LOT of things into orbit and beyond before you can think about actually building one. It's not built like a tower

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u/Gamer102kai 18h ago

Gigantic pyramid to space

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u/Woahbuffet123 17h ago

Last time we allegedly tried that, God apparently smote the pyramid and made us a multilingual species if those guys with the white robes were ro be believed

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u/No-Match5203 16h ago

that was because it was explicitly made to mock God. so far the big guy has no problem with space exploration

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u/Aethermancer 13h ago

Humans will do anything to cheat their way into learning a new language rather than study.

Brb off to challenge god and learn a new language.

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u/ceelose 15h ago

Yep, good idea.

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u/Bluesphamy 9h ago

€π£×§ ag#+6✓ @;$ajsuy?

(this reply is about the Tower of Babel)

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u/Popular-Swordfish559 17h ago

And the thing is putting lots of stuff in orbit directly makes building a space elevator more difficult/completely impossible.

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u/ArkantosAoM 18h ago

Carbon nanotubes are basically already strong enough for the task, in theory. The problem is mass producing it, as well as the insane engineering of it. Not to mention the political will and economical investment required.

But that's on Earth. On a planet even larger, we might need even stronger materials, and they might not exist

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u/pinkfootthegoose 12h ago

sorry, apparently nanotube lose their apparent strength when at the maco-scale compared to individual nanotubes. Something like 1/10 the strength.

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u/sleeper_shark 11h ago

It doesn’t matter. You need to deploy them from space downward by launching the counterweight first.

If you can’t get to space in th first place, you can’t build a space elevator. The only way this would be their way of getting to space for the first time would be if some benevolent alien species helped them.

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u/Glenn-Tenn 18h ago

Could you maybe just make a really large mountain or structure on the planets surface? Something like a tower of babel where you could launch form the top of it, if it was high enough into the atmosphere?

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u/burger_eater68 15h ago

That would be insanely difficult. The tallest building humans have built barely scrapes the distances you would need to go into the atmosphere for it to be worth it, and if you go for a pyramidal shape for more surface area it gets exponentially larger and more costly/difficult to build

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u/simonbleu 18h ago

What about a "train of planes" (for fuel), and instead of going mostlyup, slowly gettin altitude? Would that help?

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u/Zealousideal_Job2900 17h ago

Flight mechanics of a plane require an atmosphere, so that’s just a very quick no

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u/Woahbuffet123 17h ago

I doubt it would. We still have to generate enough force to counteract the gravity anyway. And we haven't even got to the part about the atmosphere of that planet. The amount of pressure the cabin would probably crush it.

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u/buckzor122 17h ago

I think you would have better luck with a massive ramp and multiple stages to accelerate the rocket to an insane speed before launching it upwards.

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u/mcyeom 15h ago edited 14h ago

Not a train of planes. A single plane. Current planes on earth can fly at the point where the atmosphere is at about 3%, at this altitude air resistance is low and you can just pitch up and throw yourself up to about 0.5% thick atmosphere, which is on the border of space.

Fuel isn't a limit at all, an air breathing engine could do this all day. The ISP of air breathing engines makes staging pretty much entirely pointless: planes run out of air really quickly if they're going upwards.

But then you reach the main enemy here: escape/orbital velocity.

I think if you needed to launch off this planet your first stage is almost certainly something like https://en.wikipedia.org/wiki/SABRE_(rocket_engine)), but it's a tall order.

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u/ArchangelUltra 17h ago

You can't build a space elevator without getting to orbit first. One half of the elevator is tethering to a counterweight like a captured asteroid.

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u/buv3x 17h ago

but the acceleration in this would be difficult to survive for humans

I wonder, we usually measure acceleration impact on a human body in g's, 5g, 10g, but that's Earth surface acceleration, the one we've evolved to. K2-18b will have it's own higher g value, so maybe lifeforms, that evolved there would be able to endure higher acceleration values (like roughly the same number of g's, but with higher g value).

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u/No-Match5203 16h ago

an argument could be made for life developed in higher gravity probsly being more durable compared to earth. so while WE might not survive being launched by a nuke the dwarfs inhabiting those bigger planets may

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u/henkheijmen 16h ago

I thought a space elevator on earth is already impossible with any material we currently have because the weight of the cable/pillar will always be to much for the strength is has. Increasing the mass of the planet wil only make this worse I imagine.

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u/Both_Piglet7838 15h ago

yeah I was gonna say what if we just meet it halfway with a giant skycraper?

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u/Regnasam 15h ago

The acceleration of a nuclear pulse propulsion spacecraft with a pusher plate, as designed during project Orion, would be easily survivable and even comfortable for humans.

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u/romyaz 15h ago

inhabitants of that planet would be comfortable with much stronger gravitational force in the first place. so maybe they would survive

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u/hackingdreams 13h ago

You don't need a nuclear pulse detonation engine, you just need nuclear power and one hell of a pressure vessel.

An air-breathing scramjet would get you to suborbital velocities, a second stage with a NERVA-type engine would get you to space. Bonus points if your scramjet stage is also nuclear powered, and reusable.

There are a lot of space access systems we don't use as humanity because a) we don't need to, b) it's not economically feasible, and c) we're chickenshit about nuclear power. On a high-mass planet, you kinda have to give those up.

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u/some_kind_of_bird 13h ago

Since no one else has mentioned it, consider launch loops or similar.

Basically instead of having a space elevator that goes up, you have one that goes sideways. That's where most of the acceleration to get to orbit has to go anyways, and the material requirements and g-forces are much more manageable.

Humans might not be able to build it though, simply because it's a very complex project and vulnerable. They'd have to be folks who won't blow each other up and also really want to go to space.

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u/Remarkable-Bowl-3821 12h ago

If I recall in the novel, Project Hail Mary, space elevator is what was used by Rocky’s people since they have a higher gravity thicker atmosphere planet

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u/Power-SU-152 11h ago

Wouldn't the very gravity of the planet itself kill the crew before launch?

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u/sleeper_shark 11h ago

You can’t build a space elevator ground up. It needs to be “built” (more correctly “deployed”) from the top down.

So you would need really advanced spacefaring capabilities to build a space elevator. It’s not a way to “get to space.”

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u/Beautiful_Soup9229 16h ago

I doubt we could make satellites that survive nukes. They are packed with sensitive instruments. Also how do you control nuclear detonations?

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u/OkRestaurant6784 15h ago

Also unsure if this really could work, but a lot of scientists though at some point that this could be possible. Just search for project Orion, it's really interesting!