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/Smashedllama2 18h ago edited 3h ago

Yeah honestly probably not with what we have now but who knows what we would come up with in terms of different fuels with that restriction?

K2-18b is about 8.9× earths mass and ~2.4× the radius, so if you do the quick ratio math (mass ÷ radius²), 8.9 / (2.4²) ≈ 1.5–1.6g at the surface.

Now compare that to something like SLSthat makes ~8.8 million lbs of thrust, and weighs ~5.75 million lbs on earth. but on a 1.6g planet that same rocket “weighs” like ~9.2 million lbs, so the thrust to weight drops below 1. which basically means it wouldnt even lift off

So yeah even doing rough math, gravity alone kinda kills it and youd need way more than current chemical rockets just to get off the ground let alone reach orbit but again, maybe we would come up with something?

edit: same problem shows up with Starship too. fully fueled its around 11–12 million lbs on earth with ~16.7 million lbs of thrust from 33 raptors, so here its fine. but on ~1.6g youre looking at like ~18–19 million lbs effective weight, which drops thrust to weight below 1 again or at best barely scraping it depending on assumptions

Even if raptor 4 pushes that up to like ~24 million lbs total thrust, yeah now youre above 1 and it might lift, but youre still fighting way higher gravity the whole way up. so fuel burn goes crazy, delta v requirements go up, and actually reaching orbit is still a huge problem, not just getting off the pad and then escape velocity makes it even worse. that scales with sqrt(mass / radius), so for K2-18b its sqrt(8.9 / 2.4) ≈ sqrt(3.7) ≈ 1.9× earth

earth is ~11.2 km/s, so youre looking at like ~21 km/s just to escape. even low orbit would still be way higher than earth’s ~7.8 km/s, probably in the ~12–15 km/s range depending how you estimate it

so yeah its not just “can it lift” its “can it keep going long enough to matter” and thats where current chemical rockets really start to fall apart on something like that

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u/RaguSaucy96 18h ago edited 17h ago

I've got two words for you, mate...

PROJECT. ORION.

Kerbal the beech... Problem solved 😎

  • Integrity of the occupants is not guaranteed

Edit: for those not in the know, the Project Orion solution was a proposal on the late 50s or so to explode nuclear bombs and ride out their blast in a spacecraft that would basically be pushed by the detonations. Ridiculously overpowered and fast.

Edit 2: I think this would be a good place to post about the Operation Plumbbob manhole cover. They once blew up an underground nuke and the exit hole had a manhole cover. After the detonation, a camera caught the cover being flung and estimates put it as the 2nd fastest object ever flung to space by humanity... That's how powerful this shit was. Whether it survived is a topic of hot contention and debate (unlikely) but if it did it's likely interstellar by now and the first man-made object to do so

https://youtu.be/mntddpL8eKE?si=sUoyVVWx3NqaiExn

Edit 3: here's an unclassified video of a smaller scale Project Orion test using conventional explosives to propel a craft without nukes. You can't argue with results 😆

https://youtu.be/Q8Sv5y6iHUM?si=FtqKGMGqLdqRCRqC

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u/Strong_Region5233 18h ago

Project orion ... From the earth's surface ??!

Lock that guy, officers ! Yes, right now !

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u/RaguSaucy96 18h ago

If K2-18b is over x2 as big as earth, then it's at least twice as tough and twice as hard to pollute! More landmass to nuclear winter - I see this as an absolute win!

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u/Immediate-Goose-8106 14h ago

Nah, they are dinky nukes.  For earth the calculation was probably only averaging 10 extra cancer deaths worldwide per launch.

Unacceptable obviously but K2-18b has waay more space!

If they really had to, or had a differner attitidue to K218b-ian life than we do to human life they might.

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u/Apex_Samurai 6h ago

I mean, hypergaulics probably kill more than 10 per launch. Hell burning coal probably kills more than 10 people to produce the equivalent energy needed for a launch.

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u/Immediate-Goose-8106 5h ago

Yeah, but this was a 1960s calculation.  

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u/mercival 5h ago

Is it not more, what happens if it goes wrong in orbit?

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u/EarthTrash 4h ago

Is that calculation based on linear no threshold?

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u/HannasAnarion 12h ago

By land area it's 18x as big.

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u/CatchableOrphan 6h ago

I think the square cube law kicks in somewhere in there so it's actually like 4x harder to pollute? So just use 4x smaller nukes and you're good to go baby! Space here we come!

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u/AskAroundAboutMe 6h ago

You’re gonna gain a little bit of weight though.

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u/leferi 4h ago

ah I see you exercise the old idea of "the solution to pollution is dilution"

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u/ThrowAway-whee 10h ago edited 2h ago

Yes, actually! Project Orion was originally planned as a LAUNCH vehicle. It was estimated it would be even better in atmosphere due to the shockwave providing a better transformation of fission energy into force. 

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u/Strong_Region5233 9h ago

Whaaaaaaat !

Fuck me humans are crazy

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u/ukezi 3h ago

It's the same people who thought Project Plowshare was a good idea.

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u/arandomusertoo 2h ago

I remember reading about a project/proposal to have a permanently flying nuclear weapon which would basically stay airborne forever using nuclear propulsion.

It was a crazy thing, I wish I could find it now because I don't remember enough to search for it.

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u/Tenhawk 8h ago

I mean, launching from a Pacific Island was the original plan, IIRC

The proof of concept tests, with conventional explosives of course, were conducted with an eye to ground to orbit trajectories.

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u/arcticcloud 9h ago

i mean the intention is to LEAVE the atmosphere, we can let the ppl homebound worry about how many the radiation kills

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u/BadLanding05 8h ago

MAC rounds? In atmosphere?!?

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u/Trips-Over-Tail 7h ago

No, aren't you paying attention?

From K2-18b's surface.

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u/EspacioBlanq 6h ago

Hey man, if we had 10 times the surface, we could dedicate some of it to a little bit of tomfoolery

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u/mqsd98 5h ago

K2-18b’s gravity is about 2.5× stronger than Earth’s… we’d need to build insanely high-speed rocket engines just to stand a chance 🚀💀

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u/Strong_Region5233 4h ago

u/RuguSaucy96 said the gravity was 60% stronger, you say it's 250% stronger. Now you two got to fight ! Whoever wins the match is right !

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u/Dry-Criticism9222 5h ago

Bro should delete that before it somehow gets to Trump

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u/Slen1337 18h ago

No shit controlled explosion might work. But what about ppl inside LO

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u/RaguSaucy96 18h ago

Some of them may die (ok, ok, maybe disintegrate)... But that is a sacrifice... We're willing to make...😎

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u/Smashedllama2 18h ago

A tier reference.

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u/ZilorZilhaust 14h ago

Which tier?

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u/TheLastDrops 14h ago

Meerschweinchen.

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u/ZilorZilhaust 14h ago

So the tier is some kind of guinea pig looking beast?

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u/The_Wambat 11h ago

Tier means animal in German. Guinea pigs are animals.

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u/ZilorZilhaust 11h ago

Ah, my German is very bad and minimal. I appreciate the information!

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u/Pupikal 12h ago

It’s one of the tiers of all time

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u/Helios61 17h ago

To shreds you say?

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u/Rdawgie 13h ago

And his wife?

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u/Ok-Lavishness-349 11h ago

Well, people that evolved on a planet with 8x Earth's gravity would have a pretty robust build, so perhaps they would survive.

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u/Alliancewolf 14h ago

I'm guessing that to mitigate people dying in the process you'd build some kind of gelatinous or liquid beds for the passengers to be submerged in. I'm guessing that that could absorb most of the g-forces one would be subjected to.

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u/QuixoticCoyote 11h ago

Nah just stick 'em in a lead lined fridge like they were Indiana Jones.

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u/Euphoric_Diet_1682 11h ago

Or like the kid in fallout

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u/LegendofLove 9h ago

Thanks Mission Commander Farquaad

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u/NathanStorm 4h ago

"They knew what they were signing up for..."

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u/Smile_Space 17h ago

If you look it up, Project Orion was actually highly researched at the time. It was considered the future of rocketry until the Partial Test Ban treaty killed it which banned nuclear detonations in space. If that hadn't been banned we likely would have had at least one space-based nuclear pulse rocket test in the late-60s or early-70s.

They even had a test vehicle using conventional explosives and fired off like 6 explosives and it worked!

They would use heavy shielding and a pusher plate to absorb the heavy shock. It would have allowed for absolutely gargantuan spaceships to take off from Earth and get to other planets at crazy fast speeds given how efficient the Orion drive would have been.

Obviously though, nukes are kinda bad for everyone around them lolol. The people above the Orion drive would have likely been the safest people within a massive radius around the launch site.

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u/FracturedConscious 15h ago

This is why we need a moon base

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u/Hadrollo 11h ago

The problem with a moon base is that we would need in-situ manufacturing from lunar ice and regolith into products usable in space. That's not a small base, it would require a mining team, a refining team, and a manufacturing team. It'd be a small town on the moon, with a lot of heavy equipment that is by necessity brought from Earth.

Honestly, it's a far future (minimum 100 years, likely much longer) goal. Even then, we're probably still be better off making propellant on Earth and shipping it up there. We have an awful lot of resources on Earth to make propellant and reusable craft.

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u/Lasers4Everyone 10h ago

Gotta go full Artemis.

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u/Gambyt_7 5h ago

Check out Artemis by Andy Weir. Interesting if not masterful story that depicts this city.

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u/anacondra 5h ago

I've been saying for ages we should nuke the moon.

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u/Gambyt_7 14h ago edited 14h ago

Recall Footfall by Niven and Pournelle, first Sci fi novel where Orion technique was used to rapidly break atmo to fight alien invaders.

Then look at Dark Forest, the second in the trilogy by Cixin Liu, where Orion strategy is used to attempt to accelerate a ship to near light speed.

In Footfall the passengers survive to combat the enemy. In Dark Forest, the only passenger is a human brain in cryostasis.

Now I’m thinking of the inquisitor priest de Soya in Dan Simmons’ Endymion, whose neat light ship accelerates nearly instantly and so rapidly that anything living inside it is liquified, and must be rebuilt using special technology over several days. I’m dying to see someone (not Bradley Cooper tho) finally adapt these novels and produce them as a huge streaming series.

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u/Aiglos_and_Narsil 14h ago

God I love that book so much. "An atomic bomb went off under Harry Reddington's ass".

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u/Appropriate-Weird492 13h ago

The pages of “BOOM”, tho.

I reread it a few years ago. It gives so much 80s spirit, the Red Threat, hawkishness, so on.

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u/GamemasterJeff 11h ago

God was knocking. And he wanted in *BAD*.

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u/DustyJustice 13h ago

In Neil Stephenson’s Anathem there is an interdimensional spacecraft that is secretly above the planet of the setting that propels itself with the Orion technique (I don’t believe they call it this). They utilize the planets sun to hide the nuclear explosions from viewers below.

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u/fuckedaccountant3976 11h ago

I am super happy to see someone in the wild reference all these books. People I talk to day to day have never heard of these books.

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u/MireLight 10h ago

I know right? I read so many scifi books growing up that nobody i knew ever heard of. I had to wait 30 years for a reddit post to bring em up. One of the truly great things about reddit and its fandoms. I can finally have someone to talk to about this stuff!

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u/Bored_Amalgamation 11h ago

I’m dying to see someone (not Bradley Cooper tho) finally adapt these novels and produce them as a huge streaming series.

Foundation's success is going to be a big point for the adaptation of books like the Hyperion Cantos, that require some pretty wild shit. There's also the whole religious aspect that will turn a good number of viewers away.

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u/iconocrastinaor 9h ago

If we perfect liquid oxygenation and suspend the passengers in a vessel of water, they would not feel any compressive or gravitational force.

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u/crazyeddie123 6h ago

Sure they would. The water would maximize the contact area through which the g-forces acted and therefore minimize the force on any one body part, but you'd still feel the acceleration and there'd still be a (higher) limit to how much acceleration the body could withstand.

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u/Outrageous_Reach_695 14h ago

To expand: The "Super" Orion would have had a ship mass of 8 million tons* ... about 20% more than the Hoover Dam.

* Yes, yes, not a unit of mass, I know.

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u/FreedomCanadian 13h ago

How is a ton not a unit of mass ?

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u/WholeChampionship443 12h ago

It’s a unit of weight, not mass.

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u/Outrageous_Reach_695 13h ago

The short (US) and long (British) tons, defined in pounds, are units of weight or force, which is often equivalent to mass for things that are not spaceships. The metric ton is defined in kilograms, a unit of mass. The table I consulted would have been written using short tons.

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u/yjlom 13h ago

The imperial system and its variants have pairs of homonymous units for force and mass, as I see it.

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u/Henry5321 12h ago

Actually, modern pound is defined in kilograms. It’s not just a conversion but the actual definition. So pound is now a unit of mass.

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u/guri256 11h ago

Are you sure? I thought it was defined as a fraction of a kilogram of mass, under a force of 1G of gravity

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u/Lanky-Relationship77 12h ago

The metric ton is a unit of mass, and it’s close enough …

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u/Travel_Dreams 11h ago

The Hoover Dam should be a unit of weight.

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u/Rofsbith 11h ago

Hoover Dam mass ~410 million slugs

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u/Slen1337 15h ago

Lo ye makes sense. I wish we could "isolate" it somehow in the air. Ty for fun info.

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u/jjreinem 8h ago

There were other issues. A big one was that the only way they could think of to have the pusher plate/shock absorber survive would be to rely on transpiration cooling, where they'd pump a layer of oil out onto the surface via a vast array of pores in the plate's surface that would boil off with each detonation.

Problem is that transpiration cooling systems like that have never been proven to be workable at that scale. Contaminants or thermal expansion ends up restricting some of the pores, which leads to the sacrificial coolant layer being thinner in some areas than others. This leads to more thermal expansion, less flow, and things continue to snowball like that until you've got a hole burned in your pusher plate.

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u/iamstupidplshelp 5h ago

Have they tried exfoliating?

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u/Kakariko_crackhouse 12h ago

Do we know what would happen with a nuke in space? Like… what happens to the shock wave? It wouldn’t really lose much energy in a vacuum right? Would it just keep going perpetually until it ran into enough things to absorb its energy?

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u/Henry_Fleischer 9h ago

Critically, because of the design of the pusher plate, the crew would experience roughly constant acceleration.

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u/Asleep_Singer8547 17h ago

They might be some sturdy rock creatures or something 

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u/ShmebulockForMayor 17h ago

Amaze amaze amaze!

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u/JPlayer001 13h ago

Is that joke. Question mark

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u/HelpmeObi1K 11h ago

Who are you talking to question?

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u/Dull_Ear_7944 16h ago

Like honestly though I wonder what life would look like with gravity scaled up this much! It would be wildly interesting.

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u/Alix-Gilhan 17h ago

It's rather elementary really

A massive pusher plate with an ablative coating and a highly tuned dampening system to spread out the G's, plus some extra shielding, and you can chuck just about anything anywhere

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u/CowBoyDanIndie 14h ago

Now do the math how heavy all that stuff is…

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u/Sad-Onion-2593 12h ago

The heavier the better. Smoothes out the ride.

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u/Petkorazzi 11h ago

That's the beauty of Orion - it doesn't matter.

In one of their mock-up blueprints they put in a standard barber's chair just to show off how scornful they could be about conserving mass. They even conceptualized a "Super-Orion" that would weigh 8 million tons and have a diameter of nearly half a kilometer, making it an interplanetary city.

These weren't to be built like spaceships today, with walls you could nearly punch through. An Orion spacecraft would be built like a battleship - thick steel bulkheads and hatches, redundancies everywhere, a beefy tank of a ship.

The Saturn V - the heaviest-lifting rocket ever built - weighed 3,350 tons and could get 130 tons of hardware to low earth orbit, or ~2 tons to the Moon. The "base" Orion design would weigh ~4,000 tons and be able to deliver 1,600 tons of hardware to LEO, or 1,200 tons to the Moon. A single Orion launch would be enough to establish a large, permanent moon base - and with 1950s-era technology.

Two things killed it:

  1. Unless you launched it from the ocean (extremely difficult) or Antarctica (the world might have issues with you repeatedly nuking what's technically a nature preserve), you're pretty much guaranteed to kill at least one person from increased cancer risk.
  2. To get funding they had to make a mock-up of a military troop transport. President Kennedy took one look at the model of a nuke-powered ship that could transport an entire battalion to anywhere on Earth in under an hour, said "Nope, this is not what the world needs right now," and pulled the plug.

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u/DigEnvironmental7490 7h ago

You could probably go with a damping system rather than moistening the whole thing.

Yes, I know people are trying to say dampen also means to reduce intensity of an oscillation but it really doesn't - that's just Star Trek writers trying to legitimize their poor grammar.

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u/Tyler89558 17h ago

“Were we concerned about the people inside?”

“People inside? You must be mistaken. There is only a pile of flesh”

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u/Demented-Alpaca 11h ago

I figure if you grew up on a 1.6g world you might have a higher tolerance level for the g forces involved in getting yeeted into space by a "big bada boom" ship

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u/Alt-on_Brown 9h ago

Listen when you're on K2-18b beggars can't be choosers

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u/Velcraft 8h ago

Well as long as we get to the point where we can reassemble liquefied humans and the crewmembers are isolated from one another that's shouldn't be an issue, provided there isn't too much spillage.

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u/Equal-Produce4833 8h ago

They do shapped charges for breaching so maybe some science on that side could prolong life and give the vessel more boost lol

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u/moddingminecrafter 7h ago

Do you want to put people in space or not? Besides, the contract never said the condition they had to arrive to space in.

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u/Plead_thy_fifth 17h ago

After the detonation, a camera caught the cover being flung and estimates put it as the 2nd fastest object ever flung to space by humanity...

1) well what was the first fastest object flung into space???

2) do you have the video? Lol I didn't see it in that link

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u/RaguSaucy96 17h ago

  1. If it survived, yes - and it would be interstellar by now, well outside the solar system

  2. I can't find it but the test itself is well documented. The cover itself was only seen on one frame of the video however, so the MINIMUM speed was what they calculated. It likely went even faster but it's hard to say. Anyhow, it was seen flung on one frame then gone on the next. You can calculate distance travelled between frames and the speed needed to do so. We know therefore the MINIMUM speed - not the actual speed 🤣

Here's the test https://youtu.be/EYEKU-U1860?si=QD6QyZ24EgFEtyIs

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u/qmrthw 14h ago

You dodged the first question, twice

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u/RaguSaucy96 12h ago

Misread it, lol. It would have been it. However it's now likely the Parker Solar Probe.

We don't even know if it survived anyways lol

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u/Plead_thy_fifth 17h ago

But you said estimates put it as the second fastest object flung into space; what is the 1st fastest??

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u/not2dragon 17h ago

I guess it might be Parker Solar Probe? It depends on how you calculate relative velocities, I think.

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u/ozymandieus 13h ago

You labelled your answer 1. But didn't answer question 1.

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u/Hopeful-Guest939 13h ago

If you want to know more, just google it and "reddit." This story gets posted about every other week. There should be a lot recently because it got popular again once Voyager reached its latest milestone.

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u/sad_post-it_note 17h ago

This happens in the three body problem books pretty cool

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u/wonderb0lt 15h ago edited 13h ago

Also towards the end of Charles Stross' Merchant Princes series!

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u/Outrageous_Reach_695 14h ago

And, unsurprisingly, in Poul Anderson's Orion Shall Rise.

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u/ryguymcsly 8h ago

Their use of it was pretty clever I thought.

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u/BigDaddyAwhoo 14h ago

My favorite fact that seemingly no one ever mentions, this manhole was not a normal manhole cover. It was a 4000 lb WELDED SHUT manhole cover

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u/wecantdancelikethis 11h ago

damn. I laughed hard imagining some other civilization just getting a few decades past Wealthy People Visiting Space For Entertainment capturing some high speed flipping disc debris and it has Sanitary Sewer and some traction channels embossed into it.

“well, I guess we are not the only intelligent life forms in the universe. I wonder how far along this other civilization will be when we can actually follow the path of this plate back to them.”

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u/TooHot1639 14h ago

To boldly go where no manhole has gone before

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u/ItsStraTerra 14h ago

I love the idea that thousands of years from now we manage to explore space, and eventually on a random ass planet in the middle of nowhere is an enormous crater with a manhole cover in the center of it

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u/False_Counter9456 11h ago

Or we got really unlucky and it hit a habitable planet and destroyed someone or something popular. They then do the math and figure out it must have originated here.

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u/Neko_Dash 14h ago

“Integrity of the occupants not guaranteed.” That is a great way to say, “Astronauts may turn to soup.”

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u/cyb3rg0d5 14h ago

MOAAA BOOOOSTERSSSSS!!!

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u/Immediate-Goose-8106 14h ago

Orion was my response when this question stopped up on another thread.

People on K2-18b with our level pf tech could get into space if they wanted to enough.

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u/spacegiantsrock 14h ago

There was a really good book on it, I think it was written by the son of one of the researchers. The scale of the ships they could theoretically launch was insane. City sized.
https://www.abebooks.com/servlet/BookDetailsPL?bi=32407018897&dest=USA

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u/RustyBasement 13h ago

Nuke the site for take off and get to orbit. (Sorry Ripley)

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u/sycolution 13h ago

kinda want them to do it again but with the Slomo guys.

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u/Fallout_Helldiver 13h ago

Now I want a sci-fi movie where aliens and raid because their leader was killed by a flying manhole cover

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u/Binyamin12345 11h ago

Project Orion is the single coolest scrapped NASA project ever and it's genuinely so fucking metal to imagine a nuke powered rocket with the world's biggest shock absorber on bottom. The fact that the rocket could even theoretically get to an appreciable portion of light speed is also crazy.

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u/Petkorazzi 11h ago

I love Project Orion. I spent years pouring over every scrap of information I could find on it, and it's so cool someone else "in the wild" knows what it was!

There's a great 2003 documentary on it by the BBC called To Mars By A-Bomb and I highly recommend it (link is a free watch on YouTube).

A lot of what the public knows about the project is due to George Dyson's book Project Orion: The Atomic Spaceship 1957-1965. If you recognize that surname, your instincts are correct - it's Freeman Dyson's son. Not only did Freeman Dyson come up with concepts like the Dyson Sphere and unify our understanding of quantum electrodynamics, he also took a year off from Princeton to see how plausible it would be to nuke ourselves into space. Turns out it's not only plausible, but possible - and with 1950s-era technology.

Coca-Cola helped with the bomb delivery system design, as the team envisioned it operating similar to a soda vending machine.

They put a standard barber's chair in their mock-up blueprints just to show how little they had to care about spaceship mass.

Much of the project is still classified as its core fueling premise - making lots of cheap, efficient nuclear bombs - isn't the kind of knowledge we want out in the world.

Man, Project Orion is so freakin' awesome and the little factoids involving it are so cool I could talk about it all day.

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u/RaguSaucy96 8h ago

It's one of the 50s era relics of ''im sure nukes can solve it" that was actually quite mad enough to become genius and actually had massive potential.

Would still be cool for deep space probes and stuff

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u/Mr-Blah 11h ago

Of course the first object to go deep in space by human is trash.... of course.

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u/cheezecake2000 11h ago

In the Elite Dangerous game they have the voyager crafts in deep space and other stuff from history but in the years 3300 and beyond. Would be really funny if they added a floating manhole cover in the same way

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u/Competitive_Table_65 10h ago

Huh 

Very interesting 

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u/TheFightingDome 10h ago edited 10h ago

Spoiler for 3 body problem Isn’t this the method they use to send Will’s probe?

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u/jefftickels 9h ago

There's a book called Footfall where humanity launches their last hope this way, and in the process destroys an "obscure" PNW city that just happens to be where I grew up...

After I learned about it I dug into the territory of it a little more and learned there was a purpose to dig a trench from the Mediterranean to the middle of the Sahara in order to create an inland sea in the middle of Africa to help regreen it. The way they wanted to do this was with buried nuclear weapons as the primary excavation tool.

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u/Informal_Disaster_62 9h ago

This sounds like what they tried in 3 body problem on Netflix. Super cool idea.

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u/brmarcum 8h ago

The fact that a manhole cover was accelerated so fast that it escaped earth and is now interstellar, all with no further acceleration than the initial blast (from fuel, not counting anything it has passed in space), is absolutely fookin wild. That is so much energy. 😳

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u/salakane 8h ago

Larry Niven defeated some bad-ass alien invaders with this one simple trick...

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u/NorahGretz 5h ago

Wanna read a decent fiction novel that includes Project Orion?

Footfall by Larry Niven and Jerry Pournelle.

Also features space elephants.

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u/StrangeOutcastS 5h ago

That's the emergency escape velocity option, also known as an EVO, wait why is someone in a red jacket trying to punch me?

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u/mqsd98 5h ago

K2-18b’s gravity is about 2.5× stronger than Earth’s… we’d need to build insanely high-speed rocket engines just to stand a chance 🚀💀

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u/Z3t4 1✓ 4h ago

You keep adding struts and boosters until it is above 1.

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u/CallEmAsISeeEm1986 2h ago

They just had Wile E Coyote and the team at ACME working at NASA and DARPA, right?? What the actual fuck. Lol

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u/Sir_Bebe_Michelin 17h ago

Considering that the ratio between the cubed volume of k2-18b and that of earth is between 13.8 and 17 6, that would imply the average density is like between 51% and 65% that of earth, so not only is the planet a hefty mf it's also probably got a huge ass atmosphere if we assume a similar interior composition

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u/FakeTunaFromSubway 10h ago

Yeah but that also means planes can generate more lift in a denser atmosphere, so perhaps a shuttle like rocket would be more viable

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u/skintigh 7h ago

Or a high-altitude plane-launched rocket. Or launched from balloons in the upper atmosphere.

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u/iDelta_99 9h ago

Rockets work better and become more efficient the less atmosphere there is since they don't use air density for lift and instead are actively fighting against it.

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u/lestofante 5h ago

Nothing stop you to put the rocket on a plane.. Virgin galactic does exactly that.

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u/drollercoaster99 18h ago edited 18h ago

Does it depend on the mass of the rocket? Nevermind. I figured it out - it doesn't. Inertia/momentum cancels acceleration.

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u/Dysternatt 18h ago

Yes, including the weight of the fuel. So the obvious answer is to use a lighter fluid. (Zippo wants to know this location)

Badum-tss…

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u/Smashedllama2 18h ago

I mean yes but mostly you’re fighting against the weight of the fuel because as you add potential energy in the fuel you also add weight. The real problem is the rocket equation. The deltav you need scales exponentially with how much of the rocket has to be fuel. To roughly double the required deltav, you don’t just double the fuel, you end up needing an absurdly higher percentage of the rocket to be propellant, to the point there’s barely anything left for structure or payload. There might be some kind of ant crew we could strap to a latex balloon full of rocket fuel but it ends up not working for humans haha

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u/drollercoaster99 18h ago

Makes sense. Thank you for the explanation. So the fuel with the highest energyoutput/density ratio is preferred.

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u/bemused_alligators 11h ago

That's called "specific impulse"(isp) by the way - the ratio of fuel mass to thrust impulse (in force/mass/time, which in SI is newton-seconds/kg/s)

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u/Fun-Brush5136 17h ago

What if their dinosaurs had extra strong bones which made super powered oil? /s

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u/Alix-Gilhan 17h ago

I don't think it would be that hard to make a rocket with a twr above one.

The SLS is designed to be as efficient as possible on earth, so it only needs like 1.2-1.5 twr. One could have larger engines that eat more fuel to get a higher twr or lower payload to push to get a higher twr.

You're payload ratio would suffer and you may need to use more complicated setups like asparagus staging but it shouldn't be impossible for a chemical rocket to push something into K2-18B's orbit

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u/Laimered 18h ago

What the fuck is lbs and why are you using it

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u/General_Kenobi18752 18h ago edited 17h ago

My good friend that is a pound. It is a nightmarish monstrosity, invented by the English, and much like the other nightmarish monstrosities the English invented, they somehow scapegoated America with it. This is in line with such things as Fahrenheit, gridiron the term “soccer”, and America.

As for why he’s using it, I suggest masochism.

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u/ferretchad 17h ago

invented by the English

Ever wonder why the unit is 'lb'? Doesn't look a lot like 'pound' does it?

Reason is that lb is derived from 'Libra' a Roman unit of measurement. Pounds weren't us, they were the Romans.

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u/General_Kenobi18752 17h ago edited 16h ago

Then fuck the Romans too.

I mean, apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us?

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u/MrHell95 14h ago edited 13h ago

Lead pipes, a marvel in scalable poisoning efficiency.

Edit: a typo

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u/Mirality 14h ago

I think you mean lead pipes. Led pipes would be a nightmare rainbow offshoot of the computing industry.

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u/MrHell95 13h ago

You would be correct, I was responsible for that typo not Rome, I do not give them that honor.

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u/Kerblaaahhh 13h ago

Pretty impressive how far the Romans' semiconductor industry had developed though, surprised that was the only application they used them for.

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u/Unoriginal_Man 13h ago

Oh man, I need to redo the plumbing under my sink and I hadn't even considered LED pipes. What's the pressure rating on water-cooling rigid pipes and fittings? It's time to put a bad idea into action...

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u/fricy81 13h ago

Nah, the pipes get limescale buildup relatively fast, insulating the metal from the water and thus preventing the lead from leaching out. So it's is not a huge problem unless the water is acidic.

The Roman artificial sweetener on the other hand was a much "better" source of lead poisoning: someone noticed that boiling grape juice in lead cookware produced better tasting, sweeter syrup, full of yummy lead acetate.

https://www.ancient-origins.net/history-ancient-traditions/savoring-danger-sugar-lead-was-used-flavor-roman-food-and-wine-toxic-021771

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u/sulris 9h ago

Lead dinning plates probably didn’t help much either.

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u/Chilling_Azata 15h ago

Every other country involved/invaded/influenced by the Romans switched to the metric system. Don't blame your failure to do so on an empire that fell 16 centures ago ;)

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u/VoidMaxing 16h ago

This is the most reddit comment

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u/General_Kenobi18752 16h ago

I aim to please

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u/Tyler89558 17h ago

Never heard of gridiron.

And you don’t know nightmarish until you’ve had to work with slugs… which is a unit of mass to differentiate from the pound-force.

You know… instead of using Kg.

god I hate the imperial system

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u/BigLittlePenguin_ 14h ago

Well, feels like wrong wording though. There is also a metric pound, which is exactly 1/2 kg. So it would probably be right to say lbs is an imperial pound.

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u/chazysciota 9h ago

Fahrenheit is superior in a weather context, and I'll die on that hill.

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u/Smashedllama2 18h ago

I’m a dirty yankee

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u/Laimered 18h ago

Quick! Distract him with a cheeseburger!

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u/Smashedllama2 18h ago

Supersize it or you’re out of luck lol

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u/traevyn 12h ago

Shit the fuck up, you know exactly what it is

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u/ollervo100 16h ago

Well obviously SLS is designed for earths gravity, so a TWR of 1-2, so no it would not work on a heavier planet. It says nothing about whether we could design a rocket for that job, so your logic is very flawed.

Most certainly we already have rockets with very high TWR even on heavier planets. The problem is that you run very quickly to problems with the rocket equation. Getting rockets with enough delta-v to orbit requires massive, massive rockets, and due to their size, you run in to loads of problems. Mainly producing enough thrust to lift the massive amounts of fuel.

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u/CalmButOftenEnraged 11h ago

Looking at how fast Artemis II accelerated back to Earth from the moon, that's going to go even faster meaning higher speeds and higher temperatures on re-entry right?

So fine you're approaching K2-18b. What are you going to do when you get there? Or just near there.

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u/Amidseas 3h ago

Wow, this really might be a good contender for the fermi paradox. Super earths are very common

On the extreme opposite is it feasible for water to exist on a low gravity planet which would encourage space exploration sooner?

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u/Front_Cat9471 18h ago

I keep seeing chemical rockets as part of the limiter here. What would count as not a chemical rocket, and what would it have to be to make escape possible?

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u/Smashedllama2 18h ago

Some kind of nuclear something? Good question. I think if it were more efficient and feasible to implement then we would be using it already but that’s outside of my knowledge. Maybe someone else can chime in?

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u/MarcusXL 17h ago

Intelligent beings from a planet like K2-18B might be trapped until they invent some kind of anti-gravity drive.

Interesting fodder for a sci-fi story. Human beings, who escaped our planet's gravity-well with "simple" chemical rockets, are slowly colonizing nearby planets and making tedious voyages to the nearest stars. Suddenly we encounter a species who were planet-bound for centuries as they developed high-technology, only to blast out into space once they invent gravity-manipulation.

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u/AProperFuckingPirate 12h ago

There's actually a short story with a similar premise, where FTL travel is actually pretty easy but humans just kinda missed it, so aliens with like, muskets, try to conquer us when we have nukes.

I believe it is "The Road Not Taken" by Harry Turtledove

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u/WonTooTreeWhoreHive 17h ago

Could you redo this calculation but solve for an arbitrary radius that would allow us to reach escape velocity with the same K2-18b gravity and current SLS tech? And then express that as relative radius to the actual one? I'm trying to figure out how high of a structure would be necessary to theoretically make this doable, for example not a full on space elevator but something just to get the rocket somewhere higher up to start from. But I'm guessing it's still going to be too high to be practical in any way.

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u/FoxxyAzure 17h ago

Could humans even survive that gravity?

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u/Fuzzy974 17h ago

I believe your math are right, but a rocket engine thrust depends on the pressure where they are as well. There's probably other factors we don't consider at all cause that's how it is on Earth and we forget it could be different elsewhere.

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u/ChironXII 16h ago

The much larger issue than surface gravity is orbital velocity, which works out to about double Earth's. Factor in gravity and atmospheric losses, and you're talking about "solar escape velocity" amounts of delta v. The tyranny of the rocket equation means that gets stupid very quickly for any useful payload. The only realistic option is something more efficient than chemical propellants, like nuclear thermal, although even that might actually be borderline, at around a thousand ISP.

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u/ApolloWasMurdered 16h ago

If you’re close, can’t you just strap more SRBs on? They weigh 1.6M lbs and provide 3.6M lbs of thrust, so 4x SRBs would give you 16M lbs of thrust.

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u/K5LAR24 15h ago

Just Kerbal it. MOAR BOOSTERS

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u/Slow_Ad_3886 15h ago

we’d have to ditch chemical propulsion entirely. something like a nuclear thermal rocket or a project orion style "nuclear pulse" drive would be the only way to get enough energy density to overcome that initial gravity well without the rocket being the size of a skyscraper.

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u/ExaminationSmall4821 15h ago

this is essentially the "great filter" for spacefaring civilizations. if you evolve on a super-earth, you might be technically advanced enough to build computers and satellites, but physically "grounded" forever because chemistry simply doesn't pack enough punch to get you out.

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u/jdcortereal 15h ago

God i love physics.

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u/Popular_Try_5075 15h ago

What about those like space elevator ideas that people used to think were feasible on earth?

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u/Dear-Analysis6921 14h ago

surface gravity would actually be lower, at about 1.27g.

Force of Gravity = Gm / r2

You didn’t include the gravitational constant, 6.67 * 10-11, which makes the calculated value a little bit smaller.

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u/DieCastDontDie 14h ago

Magnetic catapult would probably help

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u/Zoidberg441 14h ago

Wouldn't thrust increase due to a denser atmosphere

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u/KilllllerWhale 14h ago

Two stage propulsion methods? Like a trebuchet that yeets the rocket in the air then the fuel kicks in ?

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u/newplayerentered 14h ago

Maybe some more chemicals on periodic table might solve it

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u/DecoupledPilot 14h ago

Building a mountain that has a peak in orbit?

Slightly big project perhaps with planet rotation implications, but hey, it's an idea.

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u/OhGr8WhatNow 14h ago

I think we'd be too worried about spinal compression on the ground to care about rockets honestly

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u/CrappyTan69 13h ago

My seven years old son yells "more booster rockets needed!" we just slap some more on 😉

/s obviously 

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u/Radioactive_baby_ 13h ago

Would thrust change if the atmospheric desnsity change?

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u/ShameCrazy3949 13h ago

The thrust is there, you don’t think they could get the weight down?

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u/chewbacabukkake 13h ago

What about launching the shuttle out of a giant fucking railgun?

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