To everyone saying launching to orbit is impossible, I have two words: Orion Drive
so it’s possible, once
Imagine a terrestrial planet that is Earthlike in all respects, but it simply has more persistent cloud cover, such that seeing an open cloudless sky is miraculously unlikely, as unlikely as humans directly witnessing an asteroid impact.
No ground based astronomy.
No technological discoveries or culture that derives from ground based astronomy.
No celestial navigation on the ground.
Very different / stunted / more difficult cartography.
Technological civilization is capable of emerging, but it would not be able to well understand anything beyond the terra firma, not untill it generated aircraft capable of breaching the cloud cover layer, and then developed airborne observatories.
I would instantly buy your book!
That just sounds like a hollow world…
Well, the church threw us back about a millenia, so what’s a few centuries.
Is there a particular instance you’re referring to here? Because contrary to popular belief, the church has historically been big on investing in what we now call science.
For instance, although the trial of Galileo is often characterised as “big bad church holds us back because religion is opposed to heliocentrism”, there was actually a lot of legitimate scientific beef against Galileo. Although he ended up being right about heliocentrism, he didn’t really have good evidence to support his claims; He didn’t understand Kepler’s laws of planetary motion, and his telescope produced so many aberrant artifacts that astronomers who use it were reasonable to be dubious of his claims.
If you’d like to learn more, here’s an excellent video by Dr Fatima, an astrophysicist turned science communicator. The philosopher of science, Paul Feyerabend also uses Galileo as a case study in his book Against Method
Well, as soon as they invent radio and experience interferens radio astronomi will evolve… I guess?
Have you read Hitchhiker’s Guide to the Galaxy?
Yea but they were playing cricket with the Galaxy
Hah, actually no I have not.
-1 nerd point lol
Good news: it’s all public domain. If you want to read it, it is here. Whole series is there, at least the public domain ones. There was a newer one that wasn’t public domain when I last checked, though that was a long time ago and it might be now.
Don’t read it for nerd points. Read it to find out why it’s associated with nerd points.
Don’t want to spoil anything because you really should, but this is very reminiscent of a plot point in one of the books.
This hoopy frood really knows where the towel is.
Damn, only now did I realize I’ve only read one book in a series
If you want to read the others, check my comment history for a link (it’s public domain).
I wrote and tried publishing a short story about a species like that.
where only occasionally people on top of mountains see stars, and they chuck it as a consequence of low pressure. eventually they invented flight, and assume pilots going high enough to see stars are having cognitive issues due to lack of air.
They asked pilots to draw the stars they see, and they get different drawings (they sent pilots at different times of the year because they couldn’t ever expect stars to shift) and assume its proof that thise stars are a cognitive artifact.
Eventually a pilot swears they are real and can actually use then to navigate, skepticism, he proves it. brand new research field emerges.
Although the story focuses more on deep DEEP time an omniengineering. (A term I just made up because mega engineering is a concept way too small compared to the one in the story).
If you want I don’t mind putting that story in the conversation.
Post it for sure
https://docs.google.com/document/d/1PTzQQKXLnBL1ICUK8IYa8YoUSD2ncQk5-jse-FaFPAI/edit?usp=drivesdk
tried putting the text in a comment, but it’s too long, I enabled comments.
I liked it. It seems to fall apart at the end a bit but this is a really cool concept for sure.
if you don’t mind. could you elaborate? it’s ok if you don’t, I am rudely asking for free labor.
I loved it. Thanks for sharing!
Given who you are, it means a lot.
That was a good read! I liked the pacing, the dawning not quite horror.
Shit yeah go for it, I love those kinds of stories!
https://docs.google.com/document/d/1PTzQQKXLnBL1ICUK8IYa8YoUSD2ncQk5-jse-FaFPAI/edit?usp=drivesdk
tried putting the text in a comment, but it’s too long, I enabled comments.
thank u, good read
I’d read it
https://docs.google.com/document/d/1PTzQQKXLnBL1ICUK8IYa8YoUSD2ncQk5-jse-FaFPAI/edit?usp=drivesdk
tried putting the text in a comment, but it’s too long, I enabled comments.
Heck yeah, I’d read that. Feels like it could have been a Hal Clement story idea.
https://docs.google.com/document/d/1PTzQQKXLnBL1ICUK8IYa8YoUSD2ncQk5-jse-FaFPAI/edit?usp=drivesdk
tried putting the text in a comment, but it’s too long, I enabled comments.
Thanks! Will review.
no pressure. and be honest, if some parts are shite tell me. and especially if it is all shite.
Project Hail Mary has a bit about this, don’t want to say more to keep it spoiler free.
Haven’t seen it yet, I appreciate the nonspoiling =D
iirc that detail they are refering to, didnt make it into the movie.
Yes, correct, they skipped a lot of the harder science for the movie to keep it a reasonable length. Movie was still very good though!
Definitely read the book. The book is about the existential elation at discovering a solution to a dire problem, so knowing a poorly-communicated version of every solution will likely ruin the book for anyone serious about the hard Sci-Fi.
The interesting thing about this is that it could be a double whammy. The collision that formed the Moon not only made Earth smaller, it also ejected a lot of material away from the orbit. This made Earth even smaller than it would otherwise have been, had the two bodies merged. And the Moon also formed in the process. The Moon causes the tides which are theorized to have a significant beneficial effect on evolving more complex forms of life.
So just being small might not be enough and having a big moon might also not be enough, but Earth was lucky enough to have both. And that’s just some of the things in a long list of things that have to go right to get complex life on a planet.
My feeling is that life is pretty rare, but given there are so many star systems in our galaxy there might be a lot of it still. But most of it is probably very simple stuff. Getting to where Earth is, might be a once every couple of millions of years event within our entire galaxy. So there really might be nothing intelligent out there at this moment in time, there might have been earlier and there might be in the future, but for right now we are it.
Yup, I wonder sometimes, all those sci-fi tales about a long lost ancient civilisation that spread throughout the galaxy before everyone else did, what if we’re set to become that, before space-faring life eventually emerges, then thrives and flourishes all over the galaxy?
One can dream anyway…
What gets me are the people that insist that humans can’t be exceptional and be the first civilization in the galaxy because we’re really dumb… which is it’s own exceptionalism.
If you really thing humans are ‘meh’, the solution to the Fermi Paradox that fits best is that we’re lucky and among the first civilizations. Especially when you consider that the universe hasn’t been hospitable to life until very recently
And that’s just some of the things in a long list of things that have to go right to get complex life on a planet.
There’s ground bacteria that adapted to live in human-made tar lakes, digesting tar instead of straw.
Jokes on us: Because of the gravity issue, alien life on such planets jumps right to stargate technology.
“They spent almost a thousand years fooling around with rockets!”
Waddayamean a « ro-ket »? You guyas don’t use the three seashell system for liftoff?
Uhh, one stargate doesn’t go anywhere.
You can accelerate it into space at g forces which would liquify living beings, perhaps?
I’d say they stand a whelks chance in a supernova of that succeeding.
Actually I’m a marine astrobiologist and that chance is really really high
Using what?
(Remember the premise of this subthread is that they’re doing this instead of rockets.)
Just frisbee those things in random directions until one works.
According to Wikipedia this planet has an estimated surface gravity of 12.43 m/s^2 with a margin of error of about 2 m/s^2. That’s only up to 50% higher than Earth’s 9.8 m/s^2 (on the high end of the error margin) so it probably would be possible to get into orbit.
That said we don’t actually know much about it for sure. We don’t know if it’s a terrestrial planet for example. It could be composed mostly of gases and liquids like Neptune.
(Not a rocket scientist or mathematician, but I spent 100s of hours playing KSP RP-1)
Just doing some estimates using data from the wikipedia page:
The dV (delta-V) needed to get into low Earth orbit is around 9.4km/s.
The dV for K2-18b might be around 19km/s, more than double that of Earth’s.It’s practically impossible I think, you would need such a massive launch vehicle. For double the dV, you would need exponentially more fuel assuming current rocketry tech (fuel+oxidizer tanks and engines). There wouldn’t be any single-stage or two-stage rockets that could do this. With a 3 or 4 stage rocket maybe? But you would be sending nearly 100% fuel off the launchpad with virtually zero payload.
Check out the “tyranny of the rocket equation”. The more propellant you need to lift heavier rockets, the more propellant you need to lift that extra propellant and so on and so on.
I tried to factor in:
spoiler
- Atmospheric drag - K2-18b’s atmosphere is quite dense with a huge radius:
The density of K2-18b is about 2.67+0.52/−0.47 g/cm3—intermediate between that of Earth and Neptune—implying that the planet has a hydrogen-rich envelope. […] Atmosphere makes up at most 6.2% of the planet’s mass
-
Since the atmosphere is so thick and takes up a lot of mass, I’ve picked 500km as the low orbit altitude (comparing to Earth’s ~100km Karman line, it makes you appreciate how thin our atmosphere is ).
-
Rotational assist - I’m assuming it’s tidally locked since it orbits so closely to its star (33 day years), and so you wouldn’t get the assist from rotation like you do on Earth:
The planet is most likely tidally locked to the star, although considering its orbital eccentricity, a spin-orbit resonance like Mercury is also possible.
Kerbal Space Program is such an amazing game that secretly teaches you physics.
With a denser atmosphere, wouldn’t that mean that you could get more lift from a traditional aerofoil than on earth? And if so, wouldn’t that technically make it easier to start from a high enough altitude that at least some of the gravity is mitigated?
That’s what i was thinking - the dense atmosphere might even allow for platforms which are permanently suspended in the air like an inverse submarine, offsetting a large amount of needed fuel for a space launch
Check out the “tyranny of the rocket equation”.
Or ask Randall Munroe How many model rocket engines would it take to launch a real rocket into space?
tidally locked
Wouldn’t that be a non starter for life? One side would be perpetually baked and the other would be frozen.
I guess there could be a planetary Goldilocks Zone in the dusk area
I figured that area would be full of extremely violent megastorms due to the heat differential.
What about something like nuclear pulse propulsion, or some kind of massive spin launch?
Nuclear propulsion, like Project Orion, would probably make it more likely they’d manage to get out of orbit. No idea on the math here, tho
https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)
If it’s tidally locked, no spin assist.
Likely tidally locked
Missed that part but that doesn’t preclude what I was saying, just requires “more” of it
Build a large enough magnetic rail launcher and you could save shit tons of fuel. Get a ship doing 2000 mph before it leaves the ground and needs its rockets and you’ll have a pretty good head start.
Could even take a scramjet to the upper layers of the atmosphere before kicking in the chemical propulsion
It’s probably still a lot harder though. You’re not just heavier, but also slower which means you’ll spend more time fighting gravity. And all the extra fuel you bring for that makes the rocket heavier which means you need even more fuel to launch the fuel. Higher surface gravity likely means a thicker atmosphere too which is a big issue and a more massive body also has a faster orbital velocity. Although in this case the larger diameter might counteract that a bit because higher orbits have slower velocities.
My point is that this would probably still be a lot harder than just building a 50% bigger rocket. If you’ve ever tried launching from Eve in Kerbal Space Program you know the pain. Although in that case you also have to fly the entire rocket there first which is its own challenge.
you’ll spend more time fighting gravity
Aw man. This is already a significant portion of my day.
It would actually be impossible for them to get to orbit using chemical rocketry, like we use. They could theoretically do it with nukes.
I’ve been wondering what a hypothetical perfect habitable planet for spacefaring would look like. Could you have one where a plane line the SR-71 Blackbird or an even less capable aircraft could simply “fly” into orbit? Or what about something Earth-like but with a flat plateau at 15,000 m where you could launch rockets from?
Classic planes require an atmosphere to generate lift. There’s an outer limit where that would be a viable mechanism, and on Earth it’s still far below LEO. Still too deep in the gravity well for ion thrusters to be viable. It requires chemical rocket fuels to bridge that gap.
Maybe someday fusion propulsion will break that limitations, but for now the best you can do is reduce the amount of fuel needed by flying to the upper atmosphere and reaching hypersonic speeds before kicking into rocket fuel propulsion.
Then after orbital injection, switching to ion thrusters to move around, and solar sails for exiting orbit into interplanetary/lunar routes.
I think Mars, assuming you terraform it, would be pretty close to that on both counts. Space planes might still be difficult, but the delta V is much lower and Olympus Mons would pretty much sit above the atmosphere.
Holy shit, I hadn’t considered that you could use Olympus Mons as a launch site cause it sticks so high up.
The best part about it is that it’s an extremely gradual slope completely unlike the mountain ranges on Earth, so you could haul stuff up there on trucks or trains easily.
The problem is you can’t have mountains like that on tectonically active planets (a mountain that big on earth would sink into the mantle), which is kind of a prequisite for a long-term magnetosphere so its unfortunately not something a species could likely ever have except as a result of terraforming a world like mars and setting up some kind of artificial magnetosphere.
If that’s true, how did Olympus mons get there in the first place? I thought it was a volcano.
Mars was geologically active but its core cooled.
Is there a lower density limit for having a magnetosphere though? A habitable planet with 1.5x earth radius and the same mass would be much easier to get off of.
I guess that could work? Earth is actually the densest planet in the solar system so our baseline mass > size ratio might actually be a bit abnormal.
Orbital speeds would be very hard to reach compared to low Earth orbits. Also a much deeper gravity well to escape for travel.
I assume it’s not just about the gravity, but also the much larger radius of the planet would mean much larger distance from the surface, and thus much more fuel needed.
That’s not how…what???
F = G * (m1 * m2) / r^2
Note that radius is both squared and the dividing term. More distance = less gravity
I stated an assumption and was contributing to the conversation. Even if that assumption is incorrect, there’s no need to be a dick about it.
It seems like a larger atmosphere would result in a longer duration exposed to atmospheric drag, thus requiring more fuel to overcome it.
Escape velocity does scale with (square root of) radius so its not a dumb thought.
And I’m not a rocket surgeon but I could imagine earth rockets might be operating near some physical limits that make a 50% increase (or whatever) infeasible.
Wikipedia says
energy = GMm/r.if
g=GM/r²thenenergy = mgr, proportional to r given g is constant.apologies
My previous comment was wrong, I derivated while integrating.
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That’s, uh, not really how that works. A taller atmosphere would mean you have to go through more of it, but unless it’s not a terrestrial then the atmosphere won’t be that much taller.
If it is a non-terrestrial planet, it’s unlikely anyone would be building rockets on there to begin with.
If it has a higher gravity would the atmosphere technically be lower since it will squish up closer to the planet?
And your username would also be relevant.
You’re sort of right. The change in distance from the surface is insignificant, but a spacecraft orbiting a bigger planet has to travel further with each orbit so its speed must be faster to avoid falling out of orbit, even if the gravitational acceleration at its orbital height is the same.
Or Uranus.
Or your mother’s.
Maybe it was “”“too easy”“” for us to get to space so that chemical propulsion was good enough. Who knows where we would be if that wasn’t the case.
i’ll tell you where. we’d be eating empanadas and drinking coffee at the good cuban place that bought the yellow shack restaurant that i’ve been trying to buy for 20 years.
damn good empanadas.
That’s what the martians said about Earth
No rockets maybe, but what about a space elevator?
Space elevators require a counterweight on the other end, but there are various (theoretical for us, for now) launch systems that could be used. Spin launch and a launch loop for example. There’s also orbital rings which are somewhat similar to space elevators but AFAIK don’t require materials as strong as a space elevator would.
Those would be harder too though. Right now we humans don’t have a material strong enough and the higher the gravity the stronger the material you would need.
I mean, that’s probably what’s keeping US down. The aliens out there are probably from worlds with low enough gravity to make a proper space elevator. And they never come to visit us because our world is just too damn big, you’d need some kind of controlled explosion to get back up from a gravity well that deep.
I assume the amount of energy required for ‘only’ 50% more is massive.
Apparently with 50% higher gravity it would be pretty much impossible with chemical rockets, but with the median of the estimate (so about 12.43 m/s2) it would be possible, you’d just need an incredibly large rocket, or non-chemical propulsion (e.g. nuclear).
A space program on that planet would definitely advance much slower than on Earth.
Much slower as in hundreds or thousands of years, so practically no difference at all.
How well funded have our space programs been? Maybe they aren’t diverting massive portions of their resources to war and can actually focus on space.
They were well funded back when their real goal was to develop ICBMs capable of delivering nukes.
I get what you are saying, but the Saturn V was never intended to be an ICBM. Depending on what numbers you look at too, they weren’t actually that well funded. Some of the largest estimates that I’ve seen place NASA’s inflation adjusted budget between 1960 and 1973 at just under $600 billion. Or roughly half of what we’re spending in one year on the military currently.
To put it another way, at its absolute peak budget NASA received roughly 4.6% of the current military budget.
Iirc near that +50% level you end up needing a saturn 5 to launch sputnik, so its more expensive to the degree that it might just be deamed unfeasable, at least at the technology level humans started launching rockets at.
Also i wonder since the diameter is larger, is this effectively like putting everything in a higher orbit which is also more difficult then if it was just twice as dense.
That really depends on the atmosphere. The lower the orbit the easier, but if you have too much drag from the atmosphere, you ain’t staying on that orbit easily
A while back I read an article that stated earth was about as high G as you could get and still be able to get to orbit with chemical rockets (barring huge leaps in tech). I could be remembering that badly though, so take it with a grain of salt
It might take them a few more centuries than us to develop the tech, but just because we use chemical engines doesn’t mean it’s the only viable method. I’m sure they’d figure something out eventually.
Getting to orbit? I don’t know if they can even stand up 😆
What does not kill them makes them stronger? 😎
John Carter of Mars? That you?
Now try escaping birch world.
You call Kepler I call it heaven, because if you think of it heaven is either fictional or a real existing place and I chose that planet as my impossible to reach place.
Ask your nearest local Mormon about Kolob.
Idk any Mormon but I had to Google it:
“Kolob is described in the Book of Abraham as the celestial body nearest unto the throne of God in LDS theology. In contrast, K2-18b is an exoplanet located 124 light-years away, known for its potential to host water and possibly life.”
Honestly didn’t know that religious people actually believe that heaven is a physical planet, always thought that it’s something spiritual, but good to know thanks for the enlightenment -
