>>7684002
>fresh water oceans
hard to imagine how

>>7684002
The oceans are salty cause of dissolved minerals from the earth. If this planet is mostly freshwater it needs to have vastly different composition in its crust.

>>7684010

It's why I'm asking. In my head it's a cool concept, but I'm not sure how feasible it is.

>>7684015

Ah, I see. Thanks anon.

Wouldn't a planet 3x bigger than earth be a lot more difficult to launch a rocket from?

>>7684002
>tfw you'll never achieve Heinlein-tier sci-fi
why even bother

>>7684067
>tfw you're not as smart as Einstein, Faraday, or any other genius. Why bother with science at all, then?

>>7684028
yes, because it has 3x the gravity.

>>7684002
Note that, all else being equal, making a planet 3x the radius of Earth will give it 3x the surface gravity.

An Earthlike atmospheric composition is still plausible, because most of Earth's oxygen comes from plankton anyway. It will be at a higher pressure, however.

Your biggest problem is the freshwater oceans. What is the oceanic life doing for minerals? It can't swim down to the ocean floor.

>>7684306
>making a planet 3x the radius of Earth will give it 3x the surface gravity
Have you even taken a physics course

>>7684331
Spherical objects can be effectively approximated as point masses, making surface acceleration g = Gm/r^2.

Assuming constant density p (roughly correct for most solid bodies), that makes g = GVp/r^2.

Since V is proportional to r^3, that makes g proportional to pr.

Assuming that the planet has a density p basically similar to Earth (fairly likely), which is why I said "all else being equal", that means increasing r by a factor of 3 increases g by a factor of 3.

>>7684350
"all else being equal" made me assume you meant mass being equal not density

>>7684353
To keep mass the same, you'd have to have a planet with the density of gaseous helium at STP.

This seems decidedly unequal to me, considering that OP wants his world to have a solid surface.