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Comment by EGreg | Hacker News Reader

Can you elaborate on this? Are you saying with a 10% higher gravity we wouldn't be able to escape Earth's field with any amount of thrust? What?

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With a modest increase in Earth's gravity, none of the rockets we have ever built would have been able to put even a small payload into even low earth orbit. Even a Saturn V wouldn't be able to launch Sputnik. Increase gravity a little more and no chemical rocket we could feasibly construct given known materials and methods would be able to do the job.

It's not about the amount of thrust. It's about being able to carry enough fuel to sustain that thrust long enough, without the weight of the fuel making the rocket too heavy to lift high enough to reach orbit.

Possibly not able to carry enough chemical fuel to lift the fuel into space and return and do a controlled landing without refueling? That seems more plausible.

Fuel is heavy, and most of it is spent on... lifting fuel.

But the way the rocket works is creating a continuous explosion behind it. The propellant explodes, pushing the rocket. It's not just the rocket equation, but the explosion from a central point BEHIND the rocket that pushes it further.

Having a nuclear explosion for example behind the rocket would surely be enough to push it into space... even on Jupiter.

Sure, which is why I said chemical fuel. New propellants change the equation.

"But the way the rocket works is creating a continuous explosion behind it."

Not quite, it's all about mass flow.

Yes, this is what I was referring to. Though there's probably another percentage that makes most rocket fuel also insufficient for anything more than LEO.

You can't escape the rocket equation.

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