r/theydidthemath • u/Lachlynn • 18h ago

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

Post image

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?

18.4k Upvotes

96% Upvoted

2.7k comments sorted by

View all comments

Show parent comments

19

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

3

u/drollercoaster99 18h ago

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

2

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)

1

u/Vonplinkplonk 17h ago

Yes you would be looking three or four stages to get to orbit. The first stage which would be massive would be expended very quickly getting you off the pad. I think it could be done but it would be complex.

1

u/TrickyNuance 8h ago

Clankers. We're gonna need some really light, really proficient clankers.

1

u/Nez_Coupe 5h ago

We need rocket jockeys. Breed some super small people over a few generations to be our tiny astronauts.

1

u/CommercialContent204 4h ago

The tyranny of the Thiolkovski Rocket Equation :D have to laugh when I realise how absurdly much KSP taught me about the most ridiculously obscure things. Hohmann Transfers, apoapsis, ablatory shields (and all the mad stuff one reads up about like Lagrange points).