There's a lot of loopholes you could plausibly escape through. For one: you could use hybrid atmosphere-breathing engines to get most of the way to low orbit. (Using ambient atmosphere as a reaction mass circumvents the rocket equation). From low orbit, you can switch to electric thrusters with Isp much higher than the engines considered here: it's no longer necessary to have a thrust/weight ratio greater than unity.…
There's a lot of loopholes you could plausibly escape through. For one: you could use hybrid atmosphere-breathing engines to get most of the way to low orbit. (Using ambient atmosphere as a reaction mass circumvents the rocket equation). From low orbit, you can switch to electric thrusters with Isp much higher than the engines considered here: it's no longer necessary to have a thrust/weight ratio greater than unity.…
A hybrid engine like SABRE might also be viable? https://en.wikipedia.org/wiki/SABRE_(rocket_engine)
I thought because gravity gets smaller by squared distance, large planets would not have crushing gravity on the surface because you are far away from the center of mass. Is that true? If so, how large would a super earth have to be to have an equivalent earth gravity on its surface?
It's because volume increases by cubed distance. For a larger planet to have the same surface gravity as ours, it would have to be less dense.
Read a sci-fi book recently with that being a central plot point. Reasonably advanced species unable to escape the gravity of its home world. There is also a dearth of fissile material in the solar system that prevent a "nuclear option". Book was written as a bit of homage to "The Mote in God's Eye" with wanting to leave to planet being seen as a "Crazy Eddie" idea. https://www.goodreads.com/book/show/59554147-cold-e…
It’s clearly more difficult, but authors are a few individuals briefly thinking about a problem not entire civilization attacking the problem across generations. My first thought is balloons work based on relative densities so they can still reach very low density air on a high gravity world. That doesn’t help much with rockets, but firing a gun or using something like spin launch is much easier if you can start from…
Mostly it's moar stages. Each stage of a kerolox engine can get you about 5 km/s, and LEO is about 8 km/s, so two stages works pretty well. Velocity for LSEO (low super-earth orbit) might be 11 km/s, so you'd need a third stage, and each stage would be 3-5 times the size of whatever it's launching.
I thought because gravity gets smaller by squared distance, large planets would not have crushing gravity on the surface because you are far away from the center of mass. Is that true? If so, how large would a super earth have to be to have an equivalent earth gravity on its surface?
It's because volume increases by cubed distance. For a larger planet to have the same surface gravity as ours, it would have to be less dense.
good points. I think the less dense part is pretty 'easy' though, earth is a bit dense for its size. (probably a result of the collision that created the moon).
A super earth 2x the diameter of Earth but with the density of Mars would have the same surface gravity as Earth (according to my back of the envelope calculations).
Imagine non-super earth's alien civilizations are probably writing up articles about how planets like ours are hard to escape. You dealt the hand you're given.
just think of the countless civilizations of blind space whales living in subsurface oceans for whom merely getting to the surface of their planet is as difficult as it is for us to get to space
Perhaps "slow" ascent would be a option, i.e. not reaching escape velocity but just steadily ascending until you are far enough away that gravity is lower. I know here on earth it is far more inefficient, which is why you always go for "ballistic" trajectories where you gain enough velocity that inertia carries you on. Maybe there is something you could "ratchet" against? Thrust a bit upward and have something preven…
I once had a fun week playing Kerbal Space Program building solar-powered quadcopter launch platforms... Basically a quadcopter which is mostly a big platform with a rocket payload in the middle. The quadcopter slowly ascends to the highest feasible altitude, bypassing all of the worst of the air resistance, and greatly reducing the delta v needed to get into orbit as a result. This was mainly helping with the atmosp…
Keep in mind that KSP happens in "easy mode" where all of the atmospheric drag, gravity pulling, and orbital speed are smaller, but they are smaller by completely non-proportional amounts.
Last time I looked, there was a mod that made Kerbin like Earth. I suggest you try it.