How much bigger could Earth be before rockets wouldn't work?

The converse of this was kind of an open problem in the early days of rocketry. Given the theoretical rocket concept, was there a propellant combination with sufficient exhaust velocity to make an orbital rocket practical? The answer was not immediately obvious, and there&#x27;s a Goddard paper where he talks about just how big the rocket has to grow as you lower the propellant velocity to get equivalent performance. Eventually you&#x27;re burning entire mountains of gunpowder just to get a few dozen miles up.<p>It was a nice surprise (and a relief) to the early rocket pioneers to realize that we lived on a planet where gravity and chemistry would make orbital rockets possible. The rest was just engineering.

If you have a sufficiently tall* first stage, and use hot staging, then you can make it work on even on an extremely large Earth.**<p>*First stage may need to extend well above the atmosphere.<p>**No, that&#x27;s for-sure not a Randall Munroe book in my hand.

Fascinating. This may weigh down the Drake equation, particularly in reducing the average time civilizations survive on planets with high gravity because their ability to become multiplanetary and survive great filters is limited.

Is there an equivalent to the Drake equation that includes a factor that describes planets small enough to escape?<p>Very depressing to me to think about how vanishingly rare smart, spacefaring life might be. But on the flipside of that, there may be a little corner of the universe where multiple spacefarers contemporaneously live within a few light years of each other. That might be cool from a space opera point of view but it&#x27;d probably end up being dominated by a space fascist enslaving everyone.

On a something like a gas giant with a hydrogen atmosphere surrounding a rocky core, would it be possible for the vessel to be hydrogen breathing until it reaches the edge of space and then ignite a stage to carry it out of the gravity well? Or if a nitrogen or CO2 atmosphere is thick enough, to fly aerodynamically or even float until it reaches a point where the gravity is appreciably lower than at surface level?

Since it&#x27;s barely mentioned in the answers, and was my first thought -- nuclear thermal rockets are something to think about too, at least in theory:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Nuclear_thermal_rocket" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Nuclear_thermal_rocket</a>

In <i>Project Hail Mary</i> one of the exoplanets is 8.45 Earth masses and the residents are able to attain space flight.<p><a href="https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;ProjectHailMary&#x2F;comments&#x2F;s5n7j4&#x2F;eridian_biology_from_project_hail_mary_canon_the&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;ProjectHailMary&#x2F;comments&#x2F;s5n7j4&#x2F;eri...</a>

The post about the 1.55R⊕ planet made me curious and I thought this was an interesting discussion

By the time of the first orbital rocket, we had already discovered nuclear power. If chemical rockets were not capable of reaching orbit, a nuclear rocket was not far behind. Humans would probably already be on other planets if chemical rockets could not launch ICBMs because nuclear rocket technology would have continued to be advanced instead of abandoned.

Interest thoughts, but forgot one very practical calculation, unfortunately not easy to calculate. I say about shock-wave, which is known from practice on Earth, and for Earth limit rocket starting mass about 10k metric tonnes at sea level<i>.<p>What it mean, shockwave from supersonic engine exhaust creates literally powerful pressure on construction, so on mentioned scale, nothing will withstand it long enough.<p>If it is possible to create much stronger materials, as I know at the moment, is unknown and we cannot forecast.<p></i> Sea level is important, because, at the moment I only remember TWO space rockets, which started from much different position, and high altitude (air) launch have very different atmosphere properties, which could be solution to shockwave problem (but have other limitations).<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Northrop_Grumman_Pegasus" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Northrop_Grumman_Pegasus</a> <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;LauncherOne" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;LauncherOne</a>

more depressing is that a space elevator might never see the day, since the material required for it is difficult to make<p>and even if it did exist, I have no idea how that thing would be put in place<p>if I remember, in the mars trilogy, it&#x27;s assembled in high altitude, low gravity, and then put in place?<p>but gravity is lower on mars so rockets work better?<p>anyway, for earth, assembling a space elevator in space, meaning putting tough cable in orbit, would require so many launches and would emit a lot of CO2 in the process.<p>also the cable might be progressively thicker starting maybe at 1&#x2F;3 of the distance, to bear the entire weight of the lower cable that is the most affected by gravity, while the rest of the cable would have a progressively centrifugal force away from earth to compensate, so maybe the cable would not need to be thick everywhere.<p>maybe that question was already asked

What technological advancements would be impossible for a civilization that can&#x27;t go to space?

It’s easier to build a space elevator for a low gravity planet as well. So if some day we find a species living on a heavy earth, even throwing them a rope may be difficult.<p>Though I don’t suppose we’ll be visiting any aliens with chemical rockets regardless. We don’t have that kind of patience.

I wonder if this was part of the inspiration for <i>Outer Wilds</i>, where the system’s planets are so small that they could be explored with wooden spaceships.

Um doesn’t balloon assistance become increasingly effective in that case? Use your plentiful surface energy blow up a balloon and float it up past the upper atmosphere.<p>But they explicitly exclude that from this question:<p>&gt;For our purposes, let&#x27;s not explore alternative or hybrid launch systems or boost systems (such as balloons, planes, laser beams, space elevators etc.). Just stick to chemical propellant rockets.

I assume civilizations on heavier planets just use nuclear propelled rockets. As I understand it, the fuel density is so much higher that you could likely manage to build feasible nuclear rockets for far far higher g than you could chemical ones.

This thread made me curious, what&#x27;s the most amount of stages a rocket has been launched with?

<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Missile_Gap" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Missile_Gap</a> by Charlie Stross features this kind of concept.

By the same token, a space faring civilization based from the Moon or Mars is much more feasible, and a large argument for colonizing either imo, also rarely discussed nowadays.

I wonder if air breathing rockets would change this much.

This was a delightfully weird question! I&#x27;m sure it makes sense to calculate this before landing on another planet, though.

Can&#x27;t you like... put rocket on a rocket to shoot it out on orbit?

Can anyone ELI5 what the issue is; I understand&#x2F;assume larger Earth increases gravity so more for rocket to overcome, but why doesn&#x27;t that also affect jet aeroplanes?<p>Or does it, it&#x27;s just that this is space.SE so naturally they&#x27;re asking about rockets specifically?

Ooh I absolutely did not click on the link yet, but I love this question!

Now try being from a water planet, and getting to escape velocity!

You can escape any gravity with teleportation, but it&#x27;s easier said than done.<p>Or maybe we&#x27;re just a dumb civilization&#x2F;species? Maybe it&#x27;s also dumb to assume our intelligence is &quot;normal&quot;.

If Randall Munroe&#x27;s name is not on the answer, it&#x27;s not the answer.

Unless you are in a black hole you can get off any planet theoraatally

And now let’s break all the numbers by mentioning it’s likely the aliens are not dumb enough to make rockets so inefficient for their task. Nuclear at minimum would be used.