So a 150lb person will weigh 300lb. Sure that's gonna suck on day one but there's plenty of people who weigh that much who get by. Without all the health complications from high body fat it wouldn't be that bad. You'd probably die young but I don't think that would bother people.

You're not the only thing that weighs twice as much; everything else does too.

I would imagine the atmospheric pressure would be the most noticeable consequence of this.

The article notes that the planet is substantially larger:

> K2-18b is very unlike our home world: It’s more than eight times the mass of Earth, which means it’s either an icy giant like Neptune or a rocky world with a thick, hydrogen-rich atmosphere.

And the Wikipedia article for "Super-Earth" mentions something relevant:

> a planet with 2 Earth-radii and 5 Earth-masses with a mean Earth-like core composition would imply that 1/200 of its mass would be in a H/He envelope, with an atmospheric pressure near to 2.0 GPa or 20,000 bar

For comparison, the atmosphere on Earth (sea level) is approximately 1 bar.

It looks like the apparent atmospheric pressure on such a planet might be similar to being approximately 200 kilometers below the surface of the ocean on Earth. For additional perspective, the Mariana trench is (I believe) the lowest point on the planet, and is only like 11 kilometers deep.

So I guess what I'm saying, is that the apparent doubling of one's weight would be an insignificant concern in the grand scheme of things.

Not sure the two are comparable. 300lb obese person's bone structure weighs the same, their heart and lungs weigh the same. I suspect 2x the weight on every organ is going to be seriously detrimental for sustained periods.

Not to mention you'd go from years and years of near 0G gravity to twice the gravity of earth. You wouldn't even be able to walk.

Compare to the difficulty of getting there in the first place, getting spin gravity to work right isn’t a big problem.

I would assume if we can figure out accelerating to near the speed of light, we'd also be able to make a viable rotating spacecraft to use centripetal force to solve that problem.

If you're making this trip in any reasonable amount of time, you're probably accelerating during the journey at least half a G anyway.

Given the published figures for size and mass, it will be closer to 1.5 - 1.6 g. Still tricksy to walk for unmodified people, but not impossible, especially given how long it will take to reach it. Plenty of time to work out how to change people.