A hydrogen planet would be particularly easy, since the light molecules would maximize Isp for a (non-combustion) thermal engine. A nuclear scramjet on a Hycaean world would have some truly impressive performance.
To explain for all of the non engineers:
On earth scramjets work because airflow enters the front of the engine and the shape of the inlet compresses the gas, fuel is added and burnt, then the exhaust gasses go out the back really fast.
With a nuclear scramjet the fission reaction heats up the middle of the scramjet so air comes in, is compressed then heated so it expands and goes out the back really fast.
That would move you very quickly and efficiently through the dense atmosphere, using almost no fuel, and you do not have to carry much reaction mass.
Then once in space you feed compressed hydrogen into the front of the engine heat it up and send it out the back really fast, just like the nuclear rocket motors that nasa is developing right now.
Maybe there is something you could "ratchet" against? Thrust a bit upward and have something prevent you from falling back down. Maybe the denser atmosphere would provide an option. You could deploy large sails as intermediate launch pads in the atmosphere for example.
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 atmospheric drag problem, though; you would presumably need a lot of atmosphere to get far enough from the planet to help with the increased need for horizontal speed with a super massive planet.
Oh hey I found an old screenshot: https://imgur.io/zq8iyV0?r
Last time I looked, there was a mod that made Kerbin like Earth. I suggest you try it.
But I am very far from an expert (not even a Kerbal player) so happy to be corrected if I'm wrong.
https://en.wikipedia.org/wiki/Spacecraft_electric_propulsion
A much more realistic and useful option is to just go air-breathing nuclear, and use the atmosphere for reaction mass.
My first thought is balloons work based on relative densities so they can still reach very low density air on a high gravity world. That doesn’t help much with rockets, but firing a gun or using something like spin launch is much easier if you can start from very low atmospheric pressure.
No idea what actual engineers could come up with.
You dealt the hand you're given.
The first remote factory ships arrive, and not long after the pile collectors go out, the machines start building new rockets.
New starships, constructed from the mineralogical ultra-super-mega-wealth that is this remote asteroid treasure, begin to rise among the golden landscape. These are not Earth-rated rockets, but rather planetary transfer super-structures that can move entire cities worth of materials, slowly and surely, out to somewhere great.
We might find a spot to park some of these cities where the weather is always going to be great. We might find a way to build them into mini Dyson-spheres, parked around a bit of fusion, or so.
I think rockets can take us to great places. Imagine a single-pass 3D printed Starship made out of titanium and other such alloys 16 Psyche might provide ..
Its a pretty big universe. A lot of it is interesting.
But I see what you're saying. Excluding our own solar system, yes, chemical rockets are super limited :)
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...
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."
From the abstract. I love papers with a sense of humor.
This might be used in a secondary process (e.g., ion or plasma generators) or directly (heating atmosphere and/or fuel) to generate thrust.
The advantage is that the power source is on the ground, and need not be lofted, which removes part of the rocket-equation limit. It's still required to source or carry reaction mass, and I'd suggest that at least a fair portion of that be obtained within the atmosphere.
I don't know what a launch trajectory would look like, though I suspect something which went relatively slowly vertical (to minimise low-elevation drag), then began a hybrid lifting-ballistic flight at the highest possible levels of the atmosphere, powered by a planet-ringing set of laser stations, and acquiring reaction mass from the atmosphere itself, might be within the realm of reason?
It also strikes me that a world with sufficient mass would tend to retain hydrogen gas itself (though that would still likely react with oxygen to form water vapour), but at higher elevations there might be a significant differential fraction of H2 to other atmospheric components. Root mean squared velocity of H2 at 27 C (300 K) is about 7,000 kph (~4,300 mph).[1]
That's already less than Earth's escape velocity, so the problem is the molecules which have higher velocity that "boil off" into space.[2] I don't have the chops to compute this.
But a laser-pumped mesospheric hydrogen ramjet rocket might be able to take advantage of highly-energised (heated or ionised) hydrogen to gain escape velocity on even a significantly larger Super-Earth.
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Notes:
1. <https://chem.libretexts.org/Bookshelves/General_Chemistry/Ch...>
2. Earth has lost roughly 25% of its primordial hydrogen (and water) by this mechanism. <https://sciencenordic.com/chemistry-climate-denmark/the-eart...>
It’s a double hit as your lower stages are also losing ~5g’s of acceleration due to gravity. So if you want to add 3g the entire rocket needs to be able to withstand an effective 8g, and you need a rocket engine + fuel to provide 8g’s worth of force. On top of this the time between each stage becomes extremely costly.
However, the density variation of rocky planets is pretty small so as they get larger you will see higher surface gravities.
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?
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.