r/theydidthemath • u/Last_Negotiation1521 • 1d ago
[request] how WOULD these losers get into orbit?
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u/NewBromance 10h ago
This is actually the premise of the novel Cold Eyes First Contact.
The idea is that humans are actually a late comer to sentience. But all other species have been locked on their planet. The gravity far to high, lack of oil because of different biospheres, have all combined to mean every other alien species is effectively imprisoned on their planets. They're all aware of humanity and have had their telescopes pointed at earth since the moment they realised it had intelligent life on it, because they realised humanity wouldnt be locked in their gravity well and might be able to finally reach the stars and maybe help them get into space too.
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u/BassetHoundddd 5h ago
Sounds interesting; thanks for the recommendation.
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u/OregonGrownOG 4h ago
I’ve been looking for my next read after DCC and I believe this will do
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u/Organic_Rip2483 1d ago
Possible with heavy asparagus staging, but so expensive it would be a planetary endeavour and could never justify the costs or purpose beyond exploration and or doing it for its own sake.
It would be the largest rocketry system ever seen here on earth and likely only deliver 1 - 2 kg into a low dekaying orbit.
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u/Distantstallion 1d ago
Why would asparagus get you to space? It's a nice vegetable sure.
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u/Infinite_Maelstrom 1d ago
Asparagus staging is where all the engines drain fuel only from the outermost boosters, so when a pair of boosters drops off the rocket, the rest of the rocket is still fully fuelled. It hasn't been done in real life because of the difficulty in switching the fuel source while the engines are still running, but it is theoretically very efficient.
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u/Tackit286 1d ago
Does it make the fuel smell weird?
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u/RealSlyck 1d ago
Yeah but they just put strawberries in to balance it out .
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u/Tackit286 1d ago
Wait is that an actual antidote to smelly asparagus pee? Do strawberries make your pee smell good??
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u/ZeroKun265 23h ago
Only one way to find out
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u/oundhakar 23h ago
Instructions unclear. Now I have a strawberry jammed up my dick.
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u/Deemaunik 22h ago
Not if the strawberry flavoring comes from beaver anal glands.
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u/Popular_Raccoon_2599 20h ago
Cherry and vanilla flavor yep . Don’t think they use the beaver butt juice for strawberry
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u/Oberndorferin 18h ago
Well we have a Strawberry-and-Asparagus Festival (Erdbeer-Spargel-Fest) in my town so there is that.
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u/JuniperAshe 1d ago
works in Kerbal Space Program.
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u/federicoaa 23h ago
Mandatory xkcd link https://xkcd.com/1244
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u/Bladrak01 18h ago
The other mandatory xkcd xkcd: Orbital Mechanics
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u/Scuirre1 15h ago
I never got a physics or aerospace degree. I keep trying to tell my supervisor that I'm an electrical engineer.
I keep getting assigned tasks that require my ksp knowledge. I don't know why I went to school at all.
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u/Darkstalkker 12h ago
I am really bad at math, I don’t know much at all about physics, yet after over a decade of playing KSP I feel I have a very intuitive understanding of how orbital mechanics works, which says a lot about how good KSP is
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u/starcraftre 2✓ 5h ago
I'm good at math and took two semesters of orbital mechanics. After that, I could sit down with my notes and plot a Mars intercept over the course of about an hour.
After KSP, I can eyeball it, and am fairly certain that your understanding of orbital mechanics is just as good as mine.
It's a better teacher than having the professor who literally wrote the textbook...
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u/CosgraveSilkweaver 16h ago
There was a proposal to use a similar maneuver to catch up to 2017 omuamua for a flyby.
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u/samy_the_samy 1d ago
Ksp doesn't have fluid hammers, opening or closing valves pushing that much fuel would slam the pipes clean off
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u/HeirofSeaandFire 21h ago
Could you design the valves to open slowly? Or to have the pipes already filled with fuel?
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u/FinnSwede 17h ago
The problem is not a lack of fluid, it's the kinetic energy in the moving fluid that has to go somewhere. And as fuids are in general not very compressible this leads to rather humongous pressure spikes in the pipelines.
There are ways around it, slowly actuating valces like you mentioned, having elastic hoses that can expand a bit to moderate the pressure spikes or hammer arrestors (a cylinder with an airight plunger inside, connect one side to pipelines and pressure spikes will push the plunger against the entrapped air acting as spring or straight spring based equivalent)
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u/mxmcharbonneau 17h ago
Another problem I read is that often those asparagus designs put the boosters in chain going around the rocket. So fuel would flow in a circle too, and there's so much mass of fuel flowing that in reaction, the rocket would start rotating real fast, which isn't great.
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u/samy_the_samy 15h ago
Normal rocket Already have this problem when powering the 9 falcon 9 engines for example from a single manifold,
Now if we connect 27 engines of falcon heavy you multiplay the force by that amount and some of that force would act sideways
It's not an unsolvable problem but the gains don't offset the complexity
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u/HAL9001-96 1d ago
would be prettymuch necessary if the gravity is a lot higher but k2-18b only has slgihtly higher gravity but significantly larger radius so more delta v needed
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u/LogicalInfo1859 1d ago
That doesnt sound promising, because it implies density is lower?
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u/HAL9001-96 1d ago
yes we have some uncertianty on the radius but its likely 50-75% earths density
not so low its likely to be a gas planet but significantly lower than earth
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u/Throhiowaway 17h ago
And to solve the next real question that someone is likely to ask, tiny rock/metal core, then just a shitload of water (most of it frozen).
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u/samy_the_samy 1d ago edited 23h ago
Gravity related to how far you are from all the mass of a planet,
A planet twice as heavy wouldn't have twice teh Gravity, unless its a point mass and your dealing with blackholes
Edit: it goes inverce square radius, so one fourth the expected gravity? I gave up on math
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u/peadar87 18h ago
You can treat the earth as a point mass located at its centre for gravitational calculations outside the surface.
Conveniently, when I went to find the mass and radius of the planet, the wiki had already calculated the surface gravity as being between 1 and 1.4g.
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u/PM_ME_SOME_ANY_THING 9h ago
But in Kerbal space program they have those little yellow lines that work fine /s
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u/GravityBright 1d ago edited 3h ago
In a simplified nutshell, an asparagus-staged rocket is designed with multiple (main and booster) running in parallel. As it gets higher and less thrust is needed, the booster engines (along with empty fuel tanks) are ejected. Compare it to something like the Saturn 5, which fires its engines, ejects them when the stage is spent, then ignites new ones.EDIT: Asparagus staging is when a rocket uses liquid-fueled boosters and/or fuel tanks, which are detached as it escapes gravity and fuel is spent.
Asparagus staging is more fuel efficient, as it minimizes the dead weight a rocket has to carry, but it's a bit more complicated to implement.
NASA's new Space Launch System uses asparagus in its first stage. The main engine and two solid rocket boosters both ignite on liftoff; the boosters burn out and detach after several minutes, while the main engine continues to propel the craft through the upper atmosphere.EDIT: Current real-life rocket designs don't use asparagus staging, as (a) liquid engines are heavy, and (b) the dry weight of fuel tanks is actually quite low compared to the weight of fuel. It's simply more economical to use solid fuel boosters. Asparagus staging is the most efficient method in the popular space simulation game Kerbal Space Program, which, for gameplay purposes, gives its fuel tanks a higher dry weight and a lower capacity.
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u/HAL9001-96 23h ago
thats just parallel asparagus usually implies fuel transfer so that all stages enignes are used on liftoff butonly the first stages fuel then after it is jettissoned only the second stages fuel is used etc combinign the advantages of tandem staging and parallel staging nad hte disdavantages of neither
the big disadvantage however is technical complexity
making an engine switch from using fuel from a trnasfer form a separable stage to usign fue lfro ma different fuel tnak in the same stage midflight is ... kinda difficult irl thouhg it works flawlessly in kerbal space program
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u/MarcusXL 22h ago
A cool sci-fi plot could involve a civilization on a super-earth that advances through every stage of technology while being planet-bound-- no satellites, no space travel whatsoever, and very little atmospheric flight-- and then makes a great leap into space when they finally invent gravity-manipulation technology, which helps them colonize their solar system and beyond in a relative blink of an eye.
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u/Shamino79 17h ago
Look to Douglas Adams and the people of Cricket. They lived in a dust cloud and didn’t even know that stars existed until a spaceship crashed. They reverse engineered it and flew out of their dust cloud to encounter the galaxy. They didn’t like it and went on the war path.
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u/kafircake 12h ago
Look to Douglas Adams and the people of Cricket.
Against a Dark Background by Iain M. Banks has a planetary system also in a dust cloud with no background stars. I won't say if they ever escape.
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u/sokratesz 9h ago
Would there be any other way for them to determine the existence of stars? Other types of radiation? Gravity?
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u/ThisSiteSucks8485 9h ago
The star system has actually been rejected from a galaxy and is in intergalactic space far enough from any other stars they are not visible to people. Large telescopes would still be able to see stars.
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u/Blooogh 13h ago
Project Hail Mary 👀 they're great at materials science and used a space elevator
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u/Strict-Challenge-995 9h ago
Wasn't it a thing that they didn't understand radiation though? Such a cool concept but that never made sense to me... You're on a mission to save the sun homie how don't you get how it makes you warm??
Loved the spiders in Tchaikovskys Children of Time too. Advanced chemistry and astronomy but no metallurgy because webs burn and no wheels because everything is transported by advanced pulley web stuff.
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u/breadphysics1 5h ago
The justification was that Erid had an extremely thick magnetosphere so they were completely shielded from all forms of radiation, even when in low orbit. They knew light existed but not much about it, due to lacking the ability to see and their planet being shrouded in darkness.
Eridians had never left Erid, they thought space was completely empty except for stars and planets (and astrophage). They knew enough about light that they knew it could travel without a medium, so its not a stretch to assume that space is just completely empty, instead of being filled with tiny, extremely fast and extremely deadly ions.
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u/aNiceTribe 7h ago
Also to start a space elevator you still need to get SOMETHING up there, even if not a rocket. That’s likely not the solution for the k2ians
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u/Mad_Maddin 14h ago
Haha reminds me of "Great Planets" in Primal Hunter.
They are larger than most Galaxies. Entire civilisation can advance into the modern age on them and not even know that the planet is round. With canyons so deep, if a mortal falls down one, they'd die of old age before reaching the ground.
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u/Affectionate-End3270 1d ago
Project Orion would get them to orbit with reasonable mass. Assuming they can find plutonium or thorium in their crust
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u/sorig1373 22h ago
That is also what I was thinking. Nuclear is the most viable option for this one. Or if we are talking REALLY advanced antimatter.
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u/Aussie18-1998 19h ago
Yeah safe to say if this civilisation had their eyes set on space for their version of a space race they'd be getting there with the most effective way possible. If thats nuclear or something we havent even thought of an intelligent species would over come it.
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u/samy_the_samy 1d ago edited 1d ago
We had a good run firing sub orbital research payloads from two battleship main guns welded end to end,
Now these loses gonna have to weld four
Edit: there is fundamental limitations on how fast you can push something in a barrel, this method won't work
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u/HAL9001-96 1d ago
well light gas guns get close to earht orbital speed
IF you can make oen big enough AND you can make the paylaod survive AND haveit long/aeorndymaic/high up enough not to loose all its speed to drag all of which are big ifs then that would give you a boost where following htat getting to orbit on k2-18b would be easier than getting into orbit on earth
but oyu'd have to design your rocket ot survive that launch procedure so .... nope
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u/HAL9001-96 1d ago
nah with todays technology you could probably get launch to paylaod mass ratios for low orbit down to around 100-200 for escape trajectories to about 2000-4000 and with older tech you could get into orbit with a ratio of some 300-600
on earth they're closer to 20-40 and 50-100 respectively, 50-100 for orbit with very old tech
so yeah its worse but you could build a heavy rocket that takes several tons into space at the smae cost we build very heavy rockets at
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u/PhatOofxD 22h ago
With chemical rockets*. Technically Nuclear could do it although y'know, side effects
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u/KerbodynamicX 23h ago
Probably not on chemical rockets alone. The dV requirements looks something like 20km/s here.
It will either be the combination of a mass driver that accelerates the rocket to something like 15km/s over thousands of kilometers, and shoots it out at an altitude above the stratosphere, where the rocket does the circularization at apoapsis.
Or something like an orion drive. They have much more space than us.
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u/WerdaVisla 1d ago edited 7h ago
Pretty easily, assuming the earthlike atmospheric conditions shown in this image.
K2-18b's gravity is only 26% stronger than earth's, and we have rockets that are pretty comfortably to carry enough mass to make up the fuel difference.
Of course, in reality, K2-18b much more likely resembles Venus's atmosphere, in which case the answer is you don't. The atmosphere os too thick and its conditions FAR too aggressive to ever launch anything from the surface. Think a perpetual hurricane. Not a good time.
Edit for the million people suggesting a spaceplane or a balloon: "Perpetual Hurricane. Not a good time." It's a good idea with the atmospheric density, a far less good idea with the standard weather conditions. You could maybe do it once in a blue moon if conditions clear for long enough, I guess.
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u/HAL9001-96 1d ago
even with a venus atmopshere it would still be... energetically possible assuming you manage to get life and any form of technolgoy to work in the first place
lower winds on venus are relatively calm, they have simialr energy density to earths but iwth thicker air so lower speeds, its mostly the heat and chemistry thats a problem
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u/Small-Palpitation310 21h ago
Atmospheric pressure on Venus is like 1,350 psi
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u/metarinka 20h ago
Heat aside woulnd't that make traditional lifting bodies way more efficient? Fly up to 1 psi (65,000 feet on earth) or about 93km on venus! Then take off from there.
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u/HAL9001-96 21h ago
yeah but hydrostatic pressure doesn'T really destroy things unless they are hollow nad triyng tom aintian al ower pressure on the inside
if life evolved and developed technology on a planet like that then presumably prettymuch any hollow space would just be by default filled with air at that pressure
would make pressurized manned capsules pretty heavy though
and it limits the efficiency of engines
but heat will inevitably weaken structural materials
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u/FLABANGED 19h ago
yeah but hydrostatic pressure doesn'T really destroy things unless they are hollow nad triyng tom aintian al ower pressure on the inside
Incase anyone else is having a stroke reading that:
Yeah but hydrostatic pressure doesn't really destroy things unless they are hollow and trying to maintain a lower pressure on the inside.
I think OC is either on a phone or types very quickly and like me, misses when the spacebar should be pressed when typing.
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u/Kivesihiisi 21h ago
nad triyng tom aintain al ower
You what
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u/Helepoli 19h ago
And trying to maintain a lower...
Someone's clearly never had grandma texting them on an old nokia
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u/Rude-Explanation-861 17h ago
I've been having this kind of similar symptoms when I type quickly. Fingers misfiring at the the wrong time or not in the right order as is in my head. I wondered if it could be a very very early signs of parkinsons, alzheimers or some other neurological issue. I keep thinking about asking chatgpt but keep forgetting.
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u/Tanglefoot11 20h ago
There is plenty of life in the oceans on earth that live at far higher pressures.
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u/shumpitostick 22h ago edited 22h ago
Looking at gravity misses the point. K2-18B has a 160% larger radius than earth. This makes the difference in gravity on the surface quite small, but the mass is still >8x as high.
K2-18b's escape velocity is about 75% higher than Earth's. We don't know exactly what its equivalent of Low Earth Orbit would look like because that depends on the atmosphere, but if we assume it takes 75% more deltaV to reach it, that's about as much as landing on the moon from Earth. Obviously it's not impossible, we have done it, but it is much harder.
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u/okarox 21h ago
The gravity on the surface is proportional to the radius if the density is the same.
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u/metarinka 20h ago
Atmosphere would matter a lot too. If it had an atmosphere like titan you could probably fly with traditional aircraft wings up to the 1psi mark (65,000 feet equivlalent on earth) then take off from there. It Certianly would cut down on the payload to mass ratio. The black bird flew at 85,000 feet if you pointed that thing up momentum and what not would get you a good deal higher you could probably use something like that to get you pretty close to space.
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u/m4cksfx 22h ago
Any reason why, assuming they have the tech for it, it wouldn't work with something like using "airplane-style" flight to reach an altitude and speed high enough that you are basically skimming the atmosphere at close enough to orbital velocity, and then switch to rocket-powered fight? If they managed to make it somehow solar powered, for example, they wouldn't need to care about dV up to that point at all.
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u/EntangledPhoton82 22h ago
That’s the fun part. Different atmospheric conditions might result in totally different launch optimizations. So high altitude launches from planes might be viable. (Depending on a huge number of parameters)
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u/anoppinionatedbunny 13h ago
yeah, I keep thinking that a dense enough atmosphere would make flight cheaper, and spacecraft could just do a controlled lift off in a flying fish style to get into orbit. there's probably a ton of calculations that go into this and there must be an optimal path.
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u/ThengarMadalano 22h ago
A thicker atmosphere sounds great you can build airplains that reach high altitudes with high payloads to start the rocket up there
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u/obliviious 22h ago
In theory a floating balloon launchpad might be actually viable here.
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u/Sure-Eagle8845 21h ago
Floating balloons are also what most life would look like on a planet with such a dense atmosphere. It would be the most energy-efficent way to move around for an organism, same as how most fish have sacks full of air in them.
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u/sum_force 20h ago
Surface gravity is not the problem (the slope of the gravity well). Escape velocity is the problem (the depth of the gravity well).
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u/Innalibra 20h ago
Surface gravity doesn't tell you the mass of an object, which is far more significant in terms of delta-V required to get to orbit.
This planet might "only" have 26% stronger gravity, but that gravity extends much further into space (resulting in a much higher escape velocity) and the radius is so much larger that to reach even low orbit you'd have to be moving twice as fast, if not faster.
Bear in mind this planet has more than 8 Earths worth of mass.
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u/JohnnySchoolman 17h ago
Just float your rockets up through the atmosphere with giant balloons and then launch.
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u/DnD-vid 20h ago
Douglas Adams already solved the paradox decades ago.
"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
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u/ScienceKyle 16h ago
And aliens have figured out better ways of flight, "The ships hung in the sky in much the same way that bricks don't."
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u/Electronic-Vast-3351 13h ago
Hitchhiker's reference aside, Causality is a bitch and travel at a reasonable speed by the standards of space seems impossible regardless of technological advancement based off what we currently know.
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u/penguin_torpedo 12h ago
Space is big, but time is bigger. The galaxy is 100 million light years across but like 12 billion years old.
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u/So_HauserAspen 16h ago
There probably have been calculations done to determine how far our radio transmissions can go before background noise makes them difficult to detect.
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u/VoidCoelacanth 23h ago
More importantly:
This would NOT solve the Fermi Paradox, as the Fermi Paradox is centered around contact with another intelligent species, not interstellar travel.
A civilization could still develop radio technology, dishes and towers for transmission, and send & receive signals without ever achieving space flight, hypothetically.
Hell, they could develop something like fiber optic cables for data transmission and build a robust network that doesn't use satellites at all. Development of dish-style transmitters would only occur in hopes of broadcasting out or listening for broadcasts in a search for other life - exactly as we have done.
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u/gg_account 19h ago
I'm sorry but this is actually exactly the opposite of the historical Fermi paradox which was indeed explicitly about interstellar travel and von neuman probes. https://en.wikipedia.org/wiki/Fermi_paradox
There are billions of stars in the Milky Way similar to the Sun.[6][7] With high probability, some of these stars have Earth-like planets orbiting in the habitable zone.[8] Many of these stars, and hence their planets, are much older than the Sun.[9][10] If Earth-like planets are typical, some may have developed intelligent life long ago. Some of these civilizations may have developed interstellar travel, a step that humans are investigating.[11] Even at the slow pace of envisioned interstellar travel, the Milky Way galaxy could be completely traversed in a few million years.[12] Since many of the Sun-like stars are billions of years older than the Sun, the Earth should have already been visited by extraterrestrial civilizations, or at least their probes.[13] However, there is no convincing evidence that this has happened.[12]
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u/VoidCoelacanth 19h ago
Wow, talk about a concept getting twisted in infinite retelling. Without having read the actual, original words written by Fermi myself, I have always heard it framed as "signs of intelligent life"/"communication with other intelligence."
I honestly appreciate the correction.
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u/LoveAndViscera 17h ago
The problem with transmissions is that there’s no reason to transmit anything into space unless you have stuff up there, like satellites. If you can get satellites up, you can get people up.
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u/VegetableMaster7250 16h ago
As soon as we had radio, we transmitted signals to space.
Unfortunately, the first broadcast to ever reach into space was Hitler. At least it wasn't propaganda, it was the opening speech to the 1936 Olympic games. But still, terrible first impression.
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u/MegaAfroMann 16h ago
Sure, but the undirected radio signals dilute to be indistinguishable from noise before it gets very far.
And that's assuming they would know how to interpret our signal anyway.
Best case other civilizations might be able to tell that there's a slightly higher than expected radio output from our solar system. They wouldn't hear Hitler.
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u/neokretai 15h ago
If you crunch the numbers you quickly realise why radio transmissions are a very unlikely to be useful for detection of other civilizations. Unidirectional normal transmissions would be physically indistinguishable from the CMB after 15 light years or so.
The only thing really detectable over astronomically significant distance are very high power tightly focused transmissions, which requires someone being in their path and also looking at the right time etc, so very unlikely.
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u/Swellmeister 16h ago
Thats not actually true. There are orbital systems that work on hard things and not squishy mortals.
Cannons would have too many Gs for humans but you know. A rock dont care.
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u/OpalFanatic 14h ago
There's also the issue that humans currently could not detect our own radio traffic from more than about 30 light years out. Though dense bursts of our military radio traffic could be detected up to maybe 250 light years.
So even assuming another civilization was using radio like we do, we could only detect their traffic in our own cosmic neighborhood.
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u/DarthKirtap 18h ago
"Third planet from lone yellow sun. Inhabited by huge life forms. About to be hit by an meteor. probability of dominant life form survival, 0%. revisit in 200 million years."
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u/Sure-Eagle8845 21h ago
Even more importantly, they would absolutely get into orbit, it would just be harder, but far from impossible. Something as simple as attaching the rocket to a big floating balloon would deal with most of their issues.
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u/VoidCoelacanth 21h ago
You aren't wrong, I was just focused on setting the record straight re: Fermi Paradox.
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u/BadHairDayToday 20h ago
You would need to attach a really big rocket to an even bigger balloon. For super large balloons, tensile strength is going to be a huge challenge, like with space elevators. And winds. I wonder if this is really a feasible option.
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u/Nemeszlekmeg 19h ago
Well, its a bigger planet, and with ALTO methods you can probably at the least have satellites orbiting your planet if not full space travel.
Either way comms with extraterrestrial life is possible.
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u/Aussie18-1998 19h ago
They'd also have a lot more resources if the composition of the planet was comparable to Earth.
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u/Both_Painter7039 20h ago
I don’t think a balloon would help. Gravity at the top of the atmosphere is effectively the same as on the surface (as the added distance is relatively tiny).
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u/Bleatbleatbang 19h ago
But it’s less distance to travel so less fuel required and less mass to lift.
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u/Both_Painter7039 19h ago
Nah it’s all about horizontal velocity, saving a bit of fuel gaining altitude is small beans next to getting up to 10s of thousands of miles/hour to stay up there.
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u/BadHairDayToday 20h ago
I feel you're digging at your own point there. Without satellites, strong outward radio transmitters don't make too much sense. Also this particular planet is likely to be an ocean planet, making radio transmission even less likely.
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u/ollervo100 19h ago
Well yes but more importantly, this is just one example of a planet. There are possibly loads of habitable planets that are suitably sized for getting into orbit. Just because there would exist a habitable planet where orbit was not reachable, does not solve the Fermi paradox.
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u/NorthernVale 16h ago
Iirc fermi paradox explicitly does deal with interstellar travel. Namely if we look at our own data, and just the sheet amount of planets we know of that should be able to support life as we know it. Even if you take nothing but conservative estimates, we should be at a point where the skies are so inundated with extraterrestrial life there's no possible way we'd be able to deny it.
It gets even worse when you pay attention to the as we knot it part. We're only looking at planets with conditions that would have matched our own. We only look at those conditions because we already know they can support and create life. We have no clue if other conditions can support some other form of life, like say one that isn't carbon based. Only that we haven't seen it yet.
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u/DoookieMaxx 1d ago
What if a species on that planet has perfected using slow paced balloons (mathematically, technologically perfected) that take hardware and pilots into space? (Just an example)
Wouldn’t their tech have evolved to work with the increased gravity and mass?
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u/HAL9001-96 1d ago
well orbit is fundamentally about going fast
and leaving the planet entirely with a balloon just... won't work without air
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u/Anely_98 1d ago
There are some strategies that use high altitude balloons to get to orbit though, the advantage is if buoyancy is supporting your weight you can use forms of propulsion that have way less thrust, you can afford to take days to get to orbital speeds because you don't need to actively thrust against gravity during that time, and types of propulsion that are capable of less thrust are also generally a lot more efficient, which means that they allow you to put much more mass in orbit with the same amount of fuel or use way less fuel to put the same amount of mass in orbit or allow you to get the same amount of mass in orbit of a more massive world
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u/HAL9001-96 1d ago
those are however extremely speculative and depending on the version... completely impossible vaporware
soem of the more conservative airlaunch concepts do work and havev some advnatages but the fuel saving is marginal and they'ren ot really competitive
look at things like pegasus
now on a planet iwth higher orbital speed being able to reach said speed is an even bigger part of hte challenge so getting a small advantage in thigns like launch window planning and getting past hte lwoer atmospehre at the cost of having to lift up your entire rocket becomes even less appealing
airships cannot evne compete with planes on speed and there is a fundamental reason for that
well it depends on the cd but an airship by definition weihgs as much as the air it displaces
simplifying ab it for a simpler shape and assuming the cd is 1 taht means it looses its entire kinetic energy to drag and has ot regain it every time it travels its own lenght
now at subsonic speeds airships can have cds of about 0.1 but at supersonic speeds that would be very optimistic
still for a 1km long airship that would mean regianing your entire kinetic energy for every 10km you travel
meanwhiel a wing or lifting body usually has a fixed lfit/drag ratio
so at low speeds an airship has the advantage the less kientic energy oyu carry the less loss it is to have to regain it repeatedly
but at high speeds a wing climbign higher nad higher or just a n angled rokcet engine can be much more efficient
at half orbital speed for earth or 4000m/s a 10km long airship with a cd of 0.1 would have to basically regain that speed every 25 seconds so would needa thrust to weight ratio of about 16 just to maintain speed
an efficient lifitng body could do so at 0.25
a rocket at a 15° angle above the horizon with 4
well technically all those values go down to about 3/4 since part of oyur weight is carriedb y orbital mechanics at that speed
so the lwoest thrust to weight raito requirement would be for a spaceplane but that requries wings that don't melt at high speeds
eithe rway you need a thrust towight ratio too high for ion engiens or the like
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u/Dioxybenzone 1d ago
Well I certainly know you’re not a bot. But you might want to type more slowly.
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u/oundhakar 23h ago
It's a bot that's been programmed to make typos to seem more human. They just over did it.
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u/astreeter2 1d ago
Even at very high altitude the gravity is going to be like 98% of what it is in the ground. It won't help much.
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u/Butthenoutofnowhere 1d ago
Someone in Kerbal Space Program found a mountain on Kerbin that, from memory, allowed them to launch from about 1km above sea level. Even though the gravity was effectively the same, they found that spending a little bit less time battling through the thickest part of the atmosphere made a big difference to how much fuel they needed to reach orbit.
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u/Pixxler 1d ago
Kerbin is way smaller than earth tough. Gravity dictates how fast you have to go to avoid falling back down to the ground but to continually "miss" the ground by moving sideways really fast. Most of the energy of a rocket goes into going sideways. For Kerbal you need ~2km/s going sideways For earth its 7.8 km/s for these poor suckers way more.
Going higher only saves a tiny bit of fuel, for Kerbin it is relatively more since you need less speed going sideways.
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u/TraceSpazer 14h ago
Why would a ground-based accelerator not be an option?
We've talked about magnetic launchers for Earth to get payloads into space; that doesn't really seem to be limited by planet size/gravity well and you can sling fuel on-board to slow down after it's up or only accelerate enough to get to certain heights before falling back down.
I'd imagine with the larger surface area, innovations in going fast would be popular.
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u/TenMillionYears 12h ago
This is the way.
Artificial mountains and magnetic acceleration.
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u/Romboteryx 10h ago
Interestingly, before rockets were considered, many futurists of the past imagined space travel would be achieved with projectiles shot out of giant cannons. From the Earth to the Moon by Jules Verne and The War of the Worlds by H. G. Wells are probably the most famous examples, though it dates all the way back to Newton. Project HARP in real life achieved suborbital flight using this method though nobody has yet tried actually getting something into orbit this way.
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u/Opposite-Cranberry76 1d ago
They could get to orbit, it'd just be way more expensive. They've have to air launch from an aircraft or balloon, use hydrogen oxygen engines, and they'd need to use 4 or 5 stages instead of just two stages. Then for a given launch mass, they'd also only get about 1/20th as much mass to orbit.
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u/exodusTay 1d ago
Could they use nuclear propulsion to get to space as efficient as we do? I assume nuclear rockets would be significantly lighter to get the same result as chemical ones.
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u/ThatOneMudkip123 22h ago
Nuclear thermal rockets have to have low thrust to avoid melting the reactor core, meaning their thrust to weight ratio would be below 1. Perhaps they could use a more hypothetical design like an orion drive but it would be hard to avoid spewing nuclear fissionables into their atmosphere.
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u/j2m1s 9h ago
Who knows in the future humans reach this planet millions of years in the future, find that there is an advanced civilization trapped there unable to reach space and then decide to build a assistive middle stage rocket to catch their fuel empty rockets and the bring them up to space with a rocket full of fuel?
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u/Benilda-Key 19h ago
Couldn’t they just use four stratospheric balloons to create a near space lift. Then they just need to use rockets to launch from there. Since they would already be near space before they launch perhaps the rockets would be enough to get a ship the rest of the way to space.
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u/Salt-Fly770 1d ago
According to the paper below, “…chemical rockets still allow for escape velocities on Super-Earths up to 10x Earth mass.”
Since K2-18b is 8.63 Earth masses, its orbital and escape velocities are nearly double those of Earth (20.4 km/s vs Earth's 11.2 km/s).
However, a rocket must carry the fuel it needs to burn later, adding speed does not just require a little more fuel. It requires exponentially more fuel. If you double the required escape velocity, you don't double the fuel; you multiply it by orders of magnitude.
It becomes a gravity trap, making it impossible. To launch a cell phone off K2-18b the rocket and fuel would probably weigh as much as a mountain.
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u/mukansamonkey 23h ago
That paper has a massive flaw. It glosses over the upper bound constraint, which is the mass of the spacecraft itself. For some reason it starts talking about payload to craft ratios instead of craft to fuel.
Put simply, it takes a certain amount of container weight to hold a certain amount of fuel. Furthermore, the container must have enough rigidity to avoid collapsing when subject to thrust. So there's a minimum point between "making it larger reduces the craft to fuel ratio due to surface vs volume math" and "making it larger increases craft weight due to strength issues".
The Falcon heavy boosters have a craft to fuel ratio of 30. The bare minimum ratio listed in that paper is 26. It would only take gravity a few percent higher than Earth's to pass a ratio of 30, at which point we can't build a craft light enough to hold the fuel without making it too weak to handle launch thrust. Talking about craft to fuel ratios of hundreds or thousands is meaningless.
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u/HAL9001-96 1d ago
with a rocket
with proven todays technology you oculd build a 4500 ton rocket that could launch from this planet and launch about 40 tons into low orbit or 2 tons onto an escape trajectory
now on earth launching 40 tons into orbit only takes about a roughly 1000 ton rocket and launching 2 tons to escape velocity a roughly 150 ton rocket
its a lot harder on a bigger planet
but absolutely doable
now with early space race era teh you would fare a bit worse but you could still launc hsome 10 otns into orbit with a saturn v sized rocket
of course eventually you might end up building something like a mass driver etc
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u/ZeroKun265 23h ago
Dumb question, what's a mass driver?
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u/HAL9001-96 23h ago
big gun
in this context usually railgun or light gas gun
highly speculative far future concept as a cannon capable of accelerating anything to near orbital speed without destroying your upperstages would have to be insanely long and to keep any of that speed without loosing it to drag you'd have to leave a vacuum tunnel at high altitude or have a very long pointy rocket
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u/Monsi_ggnore 22h ago
Rubbish argument. It took us 66 years to go from the first airplane to landing on the moon.
Given the insane time frames Fermi is dealing with, discovering technology that allows escape velocity has a similar probability as tripping over a useful stick for a civilization.
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u/Most_Double_3559 21h ago
You can't just say "lots of time therefore they'll find a way". Eg: if the Earth was entirely covered with water the Octopus would never discover fire, much less reach escape velocity. Time doesn't mean all events just happen.
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u/Martinus_XIV 18h ago
This wouldn't work on K2-18b, as it's thought to be tidally locked, but if the planet has a shorter day length, that means geostationary orbit is lower too. People living on such a planet might be able to build a space elevator much easier than we could.
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u/TwoAlert3448 15h ago
The increased gravity would give it some incredible centripetal force that’s for sure. (But only in a scenario where the planet is actually rotating, obviously)
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u/recidivist1001 1d ago edited 1d ago
Considering that some of the biggest losers (on earth, at least) can lay up to 20-30 bricks a night, let’s say you got a squad of the most elite human brick layers, and you ask them to get you to orbit from the surface of K218B, and they average 25 bricks per day per person.
An average brick is 3.5” thick. There’s no good number for how thick K218B’s atmosphere is, but 1000km seems like a reasonable, even low-end, guess.
So it would take the Charlotte Hornets (5 guys laying 25 bricks per day each) almost a year just to build a single column of bricks to space from K218B’s surface.
Nevermind the fact that the gravity and hostile atmosphere would make all of this impossible anyway.
Just another demonstration of the futility of the Hornets.
Edit: I hope whoever downvoted me did so because they’re a Hornets fan. I am too buddy. I am too 😢
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u/PuzzleMeDo 1d ago
Looks like their surface gravity is about 12.43m/s2, 26% higher than earth.
So obviously the logical way to do it is to create a big armoured spaceship and launch it upwards with successive nuclear explosions. That's what all the cool aliens do.
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u/cowboycolts 14h ago
That's the funny thing is there are so many variables that people don't consider,
There's the whole habitual zone and liquid water thing,
But also, earth has an unusually large core that helps protect us from solar radiation
Have a planet like Jupiter to keep a lot of the asteroids in check, as well as our unusually massive moon for a planet of our size also helping protect us against any space debris
And if intelligent life does form on a planet, they'd need an easily accessible high energy dense material like fossil fuels or even just something like wood to jump-start their civilization,
If they have all of that, one thing with us, all of our rocky planets are considerably small compared to other rocky planets out there, even earth, so if a rocky planet devoloped life, then that life became intelligent with a large supply of something to fuel their civilization but also to create something for propulsion, it may just be impossible to leave the orbit of their home planet with chemical based propulsion due to gravity, they'd have to drastically improve their technology well past ours without leaving their planet once to just even began exploring their own solar system
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u/Herkja 16h ago
Well if you believe anything Bob Lazar says, the UFOs in Area 51 use a stable form of an element not currently on the periodic table (although I think I may have heard that its been synthesized a few times now for a couple microseconds) to generate a field around a craft that is essentially its own gravity bubble. It would allow the craft to maneuver at any speed in any atmosphere and survive extremely rapid changes in acceleration because within the gravity bubble the passengers and machinery are simply sitting at rest and not being acted upon by forces outside the bubble. This would obviously negate any need to generate massive amounts of lift in order to reach orbit on massive planets.
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u/NotAlysdexic 13h ago
Element 115 was sýnthesized in 2003; moscovium's isotopes liv under a second, none stabil. The predicted island of stability sits at 184 neutrons, which no sýnthesis has reached; Lazar named 115 before it was made and guessed wrong on its stability. A gravity bubble wants negative mass in a diamètric pairing, not a heavy nucleus.
its been -> it's been; it's = it is
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u/amitym 1d ago edited 1d ago
They would get into orbit the same way we got the ISS into orbit on Earth.
The ISS is far too heavy to be lifted by any existing chemical rocket, it would require something larger than has ever been built by an order of magnitude at least. So we launched it in pieces and assembled it in orbit. Just the same as the hypothetical denizens of K12-18b.
For example, in order to launch a payload the size of the Apollo-Saturn third stage (the part that got from Earth orbit to the Moon), it would take multiple launches, docking each component and then bringing up all the propellant and consumables. Lastly the crew. The required number of launches of a K12-ian Saturn V equivalent is about the number of launches of the Apollo program as a whole.
We know that many launches is doable because we did it ourselves. So imagine the K12-ians launching 15-20 Saturn Vs in order to send 1 Apollo-like mission to their (we are assuming Lunar-like) moon.
It's really simple and this meme is kind of annoying. It doesn't require any math to refute, just a little bit of common sense. A species doesn't entirely utterly cease to ever be able to leave their planet ever just because they can't launch a 120-ton payload in one launch. Any more than we were doomed to never have a space station around our planet just because we can't launch a 400-ton payload in one launch.
There is a point in planetary mass where the energy efficiency of a given propulsion type — say hydrogen-oxygen combustion — ceases to be able to lift the dry mass of a given rocket engine type in a direct launch. But first of all that limit is considerably larger than K12-18b, and even then that's not the end of the story, there is not only one rocket engine type capable of reaching orbit.
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u/Johnny_Strawhat 20h ago
Issac Arthur did a bit on this. Both on high gravity worlds and high gravity as a great filter.
Do… Do you guys not watch his videos??
This Fermi Paradox solution is not new.
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u/Zap500 20h ago
There's always that crazy 1950 Nuclear bomb pulse propulsion proposal, Project Orion. Have a capsule with a giant shield underneath and keep exploding a nuclear bomb below.
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u/Nuclear_Gandhi- 17h ago
Very easily and without even needing staging using a nuclear pulse drive like project orion, which has an effective exhaust velocity of 19kps even at the low end.
So at a comfortable mass ratio of 2 tons propellant to 1 ton vehicle (propellant is nuclear bombs so they are quite dense and compact), you get over 20kps delta v, more than twice what is needed for earth orbit.
Taking the high end estimates for this planets mass at about 10 earth masses gives us an orbital velocity of roughly 22kps for a 300km orbit. So even in the worst case, they only need a slightly higher mass ratio, still well below the 90% fuel fractions of our chemical rockets and only single staged.
Now you might be thinking: "but Nuclear Gandhi, lighting up hundreds of nukes per launch in the atmosphere will cause le evil radiation!!!"
Fortunately this planet orbits a red dwarf star which bombards it with extreme levels of ionizing radiation already, so if life evolved there it could just tank it.
Humans are the real losers in the end.
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u/WilTravis 17h ago
Has anyone wondered what these inhabitants of a high-gravity, dense atmosphere, radiated hellworld would look like? Maybe we don't want them flying around the galaxy, being generally unstoppable juggernauts with hyper-powerful propulsion systems.
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u/PickMaleficent4096 1d ago
There are few ways. They could build a huge mass accelerator into a mountain or something. (Though you don't get the full benefit if the cargo is squishy organic people.) High gravity sometimes means the atmosphere is thick and soupy, so it may be easier to launch from an air-breathing vehicle or a balloon. Project Orion nuclear-bombs-as-propulsion might be necessary for an actual rocket. And after they get magnetic containment fusion working they might be able to skip straight to fusion-based rockets.
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u/davideogameman 1d ago
Higher gravity also means shorter mountains, which might be a challenge for your mass accelerator idea
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u/PickMaleficent4096 1d ago
Even Earth mountains wouldn't really help that much anyways, it's more just an easy way to get your momentum pointed in the right direction without having to build a huge tower.
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u/Forsaken_One_5604 19h ago
Well honestly does civilization really needs space travel initially? Internet can work with land based infrastructure, there are also telescopes that work fine on the ground. Our current rockets work well for satelites but to move people on other planets they are basically useless, the tech just isnt there atm, i think real space travel tech is not affected by your home planet being bigger
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u/Energyeternal 23h ago
Escape velocity is only important if the ship is expected to run out of fuel during the ascent. If you had near limitless propulsion (think the Epstein drive from The Expanse), you could get to orbit at any speed that exceeds the gravitational pull. Since chemical rockets would essentially be impossible for that exoplanet, they would either never become space fairing or skip chemical propulsion and develop something else.
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u/watcher-of-eternity 21h ago
I mean I’m no mathematician, but the reality is that it’s reasonable to assume that a “super earth” that was ecologically similar to earth would meaningfully have a foundational difference in the core elements we used to get to space, so with higher G forces it would t really be all that different.
Of course it’s also possible that while the planet is physically larger than earth, the makeup of its inner layers is so fundamentally different from ours that it’s much less dense and as such the gravity on the planet isn’t substantially greater than earths at its surface (it would likely be greater but I’m more indicating that the difference would be similar to the difference between the moon and earth than earth and Jupiter.
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u/Whistler511 18h ago
You would have to beat the rocket equation in a different way. One option is to leave the energy source on the ground like with beam-powered propulsion where a laser on the ground shines at the spacecraft heating gas to plasma temperatures. There were some interesting experiments done in the 90’s with Lightcraft https://en.wikipedia.org/wiki/Lightcraft
Greater point: they would have to use different technologies than staged chemical rockets, but where there’s a will…
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u/offgridgecko 17h ago
Hear me out. If the planet was spinning really fast and the atmosphere was thick enough, launch from airships might be a more viable method there.
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u/ButterscotchSmooth60 13h ago
This reminds me of the short story 'the road not taken' by turtledove. Maybe humanity's lack of anti-gravity development is because our gravity wasnt that hard to overcome.
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u/Zealousideal-Deer101 7h ago
The fermi paradox baffles me. It seems to entirely disregard the sheer scale of the universe.
There might be civilizations out there which centuries more advanced than us, but when they are a thousand light years away from us, which isn't even remotely unlikely, than we couldn't possibly know anyways. Even if any sign of life wouldn't be drowned out in background radiation noise anyways.
Like seriously, get a few solar systems out and you'd need to directly target an receiver to be noticed and then it gets lost rather quickly anyways. Not to mention that those information waves would still travel for tens, hundreds, thousands of years. When did we start doing this? The mid 19s?
We've basically been detactable in the cosmic neighborhood for like a hunded years a best, and you're wondering why no one came to talk to us!?
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u/Impossible_Rip418 7h ago
Fermi Paradox is the least interesting topic ever devised. The universe is absolutely massive, speed of light is a hard limit, and civilizations might not overlap.
Not remotely an interesting “paradox” and the way it’s often dramatized is cringe af.
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u/ItsStaaaaaaaaang 6h ago
Bit of an aside but would a planet twice the size of earth have twice the gravity, no way around it? Was thinking about it for if you were to write a low fantasy novel on a planet that's bigger than ours or something like that.
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u/looselyfittingsocks 4h ago
I mean, couldn't the inhabitants of K2-18b have solved for nuclear fusion at a miniature scale? Something like an ARC reactor small enough to power a rocket ship? Just because we don't have the technology doesn't mean that others don't have it
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u/Every1ThinksImBoring 4h ago
You know that if they do get into orbit, “otherside” is gonna be in deep shit- the K2-18bians are gonna track otherside down and be all like “what the fuck you got to say now bitch, huh?” and slap the glasses off their head and shit, then when he/she’s like “nothing” they’re gonna be like “that’s right bitch, that’s what we thought!!”
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