3 ms·

I learned something today :) Gravity on surface of this planet will be 3(times heavier than earth)/(1.55(radius)^2), so 1.25g, however escape velocity also dep

I learned something today :) Gravity on surface of this planet will be 3(times heavier than earth)/(1.55(radius)^2), so 1.25g, however escape velocity also depends on planet radius so we get sqrt(1.55 * 1.25) = 1.4 earths escape velocity (so 15.7km/s). Assuming Isp specific impulse of engine of around 300s, let's compute m0/mf (initial mass of rocket / payload) = exp(vEsc/(Isp*g0)) (g0=9.8m/s^2 (on both planets)): For earth, it's 45. For this planet, it's 208. So, the rocket (using our current chemical engine technology) needs 4.6 times more fuel than on earth. Much more difficult, but maybe possible... edit: formatting

BuyMyBitcoins 3y ago
We also have to consider the thickness of the atmosphere. I presume a planet with 1.5x the radius of Earth and 3x the gravity would have an atmosphere that is far more thick and any rocket would have to contend with a significant amount of drag. Plus, if it would take something like a Saturn V just to put the mass of a potato into low orbit I could easily envision an extraterrestrial civilization thinking it wasn’t worth the cost to try.
- zardo 3y ago
  > I presume a planet with 1.5x the radius of Earth and 3x the gravity would have an atmosphere that is far more thick and any rocket would have to contend with a significant amount of drag. I'm sure that's true holding all else the same, but all else isn't the same. Maybe it's airless due to stronger stellar winds.
- deepsun 3y ago
  Actually, the atmospheric drag is not a big challenge. Yes, it is a consideration of course, hence the payload fairing etc, but much larger problem going to orbit is getting speed. That's why it doesn't really help much to launch rockets from a balloon -- getting there is not a problem.