Here's the wiki page for ways around it. Of course, it's all hypothetical and theoretical: https://en.wikipedia.org/wiki/Non-rocket_spacelaunch
Spin launches have become less theoretical.
Super-Earths in Need for Extremly Big Rockets (2018)
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Re: Super-Earths in Need for Extremly Big Rockets (2018)
#22> We find that chemical rockets still allow for escape velocities on Super-Earths up to 10x Earth mass. Much heavier rocky worlds, if they exist, will require using up most of the planet as chemical fuel for the (one) launch, a rather risky undertaking.
From the abstract. I love papers with a sense of humor.
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#23Earlier quoted context omitted.
Why is it so important to get back? That implies people need to go there, I think? Why? And would it really not be possible to get to Enceladus and back (w/o people)? The gravity there is so much less than the moon. Or is it just the distance to and from Enceladus, and possibly nothing for a slingshot?
I can look at pictures of Machu Picchu on Google Maps but the experience of being there is so much better (from what I hear). That's why we want to send people. Presumably those people want to survive and come back too.
> I can look at pictures of Machu Picchu on Google Maps but the experience of being there is so much better (from what I hear).
Right, but you can't even look at pictures of these other planets because we haven't gone at all.
And if your choice was between spending $4T to go to Macchu Picchu yourself, or look at pictures on Google Maps for free - you would almost certainly not spend $4T "for the experience".
The reality is - Nasa estimates it would cost $4B for another manned moon mission. India just sent a lunar probe to the moon for about 1/100th that price.
Even if we could send someone to Saturn - the price would be more prohibitive than the chemistry.
If it costs 100-1000 times more to send humans than robots - it's probably not worth it.
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#24> It should be noted that, while the subject of this paper is silly, the analysis actually does make sense. This paper, then, is a serious analysis of a ridiculous subject, which is of course the opposite of what is usual in astrophysics
From what I can tell, this was published in August of that year, though with the silliness toned down significantly [0]
[0] https://www.cambridge.org/core/services/aop-cambridge-core/c...
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#25> water (H2O) cannot become radioactive itself
This was interesting. I researched it a little and found this on https://www.quora.com/Why-is-water-the-only-thing-on-Earth-t...
When hit by neutrons "hydrogen, move to another stable state and only become unstable when that particular atom gets hit twice" "Oxygen takes three absorptions to become radioactive" and underwater neutrons "activated mainly the sodium in the sea salt."
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#26Perhaps "slow" ascent would be a option, i.e. not reaching escape velocity but just steadily ascending until you are far enough away that gravity is lower. I know here on earth it is far more inefficient, which is why you always go for "ballistic" trajectories where you gain enough velocity that inertia carries you on. Maybe there is something you could "ratchet" against? Thrust a bit upward and have something preven…
I once had a fun week playing Kerbal Space Program building solar-powered quadcopter launch platforms... Basically a quadcopter which is mostly a big platform with a rocket payload in the middle. The quadcopter slowly ascends to the highest feasible altitude, bypassing all of the worst of the air resistance, and greatly reducing the delta v needed to get into orbit as a result. This was mainly helping with the atmosp…
Not a rocket scientist or even a physicist.. but if i remember right, the bulk of your energy in a rocket is expended on your horizontal speed not the height gain. I came across this when I was looking up if it made sense to launch a rocket from an equatorial mountain like Kilimanjaro (6000m asl)
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#27Bottom line: Chemical rockets are never going to take us any place interesting in the universe.
Chemical rockets are good at escaping a planet's gravity well. We don't currently have a better alternative. Any of the 'low and slow' methods like ion drives are only good for travel between gravity wells.
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#28Perhaps "slow" ascent would be a option, i.e. not reaching escape velocity but just steadily ascending until you are far enough away that gravity is lower. I know here on earth it is far more inefficient, which is why you always go for "ballistic" trajectories where you gain enough velocity that inertia carries you on. Maybe there is something you could "ratchet" against? Thrust a bit upward and have something preven…
My understanding was that (at least for the earth) the strength of gravity is nearly identical at the top of the atmosphere as it is at the surface. So I think that doing this would only benefit you in the sense that launching from the top of the atmosphere means you don't have to push through the atmosphere and it's associated drag, but you are still going to need nearly the same Delta V to make orbit.
But I am very far from an expert (not even a Kerbal player) so happy to be corrected if I'm wrong.
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#29I thought because gravity gets smaller by squared distance, large planets would not have crushing gravity on the surface because you are far away from the center of mass. Is that true? If so, how large would a super earth have to be to have an equivalent earth gravity on its surface?
Re: Super-Earths in Need for Extremly Big Rockets (2018)
#30Perhaps "slow" ascent would be a option, i.e. not reaching escape velocity but just steadily ascending until you are far enough away that gravity is lower. I know here on earth it is far more inefficient, which is why you always go for "ballistic" trajectories where you gain enough velocity that inertia carries you on. Maybe there is something you could "ratchet" against? Thrust a bit upward and have something preven…
As gravity increases, buoyancy also increases. A high-g civilization with access to hydrogen would be able to float to the top of their atmosphere, and then proceed to launch into space.
Not a physicist but I thought the main problem is not getting high, but getting fast in the “horizontal” dimension to balance out high gravity and stay in orbit.