Would a propeller plane be able to fly in Saturn's atmosphere?

[GypsyOfTheSatOfLove]

TL;DR Summary

Would a propeller plane be able to fly in Saturns atmosphere?

I am currently trying to make a game about Saturn and came across the xkcd article about the Interplanetary Cessna. Could their assessment of Saturn's atmosphere be incomplete in this context?

Saturn has a relatively dense atmosphere, even tho its mean molecular mass is just 2.07. At the ammonia cloud level, at 1atm and 150K, the density of the atmosphere at that molecular mass is at 0.2p right? Isnt that the density of air at 15km? Prop planes have reached that alt, havent they? Maybe not a cessna but the Bristol Type 138 did it in 1936 and the Grob Strato 2C got up higher, didnt they?

I know the temp and winds arent ideal, but wouldnt those temps be conducive for superconductors? Would an electric prop engine using a superconductor be viable? And maybe there are calmer winds nearer the poles? Would these be possible?

Many thanks!

 

[Flyboy]

Properly optimized, electric propeller aircraft have flown much higher than 15km on Earth, so I have no doubt that one could fly one on Saturn.

The issues I see are:

1. Getting flying in the first place. All the extreme high altitude airplanes I am aware of are launched from the ground, fully assembled. Such a design would not be suitable for launch to Saturn followed by the atmospheric entry and initial descent. You would need to figure out how to make a Transformer out of it and have it be 100% reliable to unfold into a flight configuration.

2. Power. All the extreme altitude electric planes I know of are solar/battery powered. That’s not going to fly, pun intended, on Saturn. It’s going to take either several RTGs or some sort of compact Brayton-cycle generator to get the requisite power. Either one would be heavy, further complicating matters.

 

[GypsyOfTheSatOfLove]

The issues I see are:
1. Getting flying in the first place.

Can this be solved by having the entire craft protected within a module designed to aerobrake in Saturn's atmo? Then deploy the craft once in thicker atmosphere? It could just glide into cruising speed...

2. Power. All the extreme altitude electric planes I know of are solar/battery powered. That’s not going to fly, pun intended, on Saturn.

Agree this would be a problem. Would changing out the propeller for a hydrogen jet engine with oxygen for fuel be more of an option? But i guess both would have limited lifespans

 

[Flyboy]

Can this be solved by having the entire craft protected within a module designed to aerobrake in Saturn's atmo? Then deploy the craft once in thicker atmosphere? It could just glide into cruising speed...

That’s why I said it would have to fold up, so that it would fit into a suitable aeroshell. You’re going to hit the atmosphere of Saturn at a frankly absurd speed, even if dropped in via a gravity slingshot off of Titan, so having a really good heat shield is required. And the size constraints of current launch vehicles means folding it up is going to have to happen anyway. You can’t fit a fully intact aircraft into a rocket, not if you want useful payload.

Would changing out the propeller for a hydrogen jet engine with oxygen for fuel be more of an option? But i guess both would have limited lifespans

Nope. That’s going to severely limit your endurance. Few hours tops. The RTG or nuclear thermal Brayton (or possibly Stirling, depending on the design) generator would be the best option for endurance.

 

[mfb]

The density of the atmosphere is not an issue, you can freely choose that by choosing your altitude. You have other issues:

Saturn: The picture here is a bit friendlier than on Jupiter. The weaker gravity—close to Earth’s, actually—and slightly denser (but still thin) atmosphere mean that we’d be able to struggle along a bit further before we gave in to either the cold or high winds and descended to the same fate as on Jupiter.

 

[GypsyOfTheSatOfLove]

The density of the atmosphere is not an issue, you can freely choose that by choosing your altitude. You have other issues:

True but doesnt saturn have areas that are less windy? In the higher latitudes i think there are relatively calm areas. Temperature is a concern, but isnt the overall tone of Interplanetary Cessna a bit too pessimistic when considering prop planes on Saturn?

I guess what im asking is, is it not possible to solve these issues with the cold and wind?

 

[Vanadium 50]

I think this question is way too vague to answer. What are the constraints? There seems to be some magic involved - such as getting the plane to Saturn in the first place. Without a clearer idea of what can be assumed as given, you can get any answer.

 

[phinds]

@GypsyOfTheSatOfLove, what is the POINT of your wanting to know this? Even if the answer were an unambiguous yes, then so what? You are NOT going to be able to build a prop plane on Saturn and any species with the technology to get from their home and then put a prop plane into the atmosphere would surely have the technology to do something MUCH better if they wanted to fly around in Saturn's atmosphere, so what is the point of your game?

 

[GypsyOfTheSatOfLove]

I think this question is way to vague to answer. What are the constraints? There seems to be some magic involved - such as getting the plane to Saturn in the first place. Without a clearer idea of what can be assumed as given, you can get any answer.

It was going off of the theoretical postulation from xkcd where he projectes what would happen to a cessna in Saturn's atmosphere.

I think the point of the question is more theoretical in that sense, would it be more or less possible to do it, in contrast to the implication in xkcd's article that it would be harder or even impossible to do it on Saturn then say another gas giant...

In the end its about curiousity i guess :) would there be a way for it to work :)

PS about constraints, hmm i guess if were just going by what we have currently or in the near future tech wise, disregarding the challenges of putting it in Saturn atmo in the first place, would we be able to do it? How would we go about solving operating a propeller at 150K for example with known or highly probable technology?

 

[GypsyOfTheSatOfLove]

@GypsyOfTheSatOfLove, what is the POINT of your wanting to know this? Even if the answer were an unambiguous yes, then so what? You are NOT going to be able to build a prop plane on Saturn and any species with the technology to get from their home and then put a prop plane into the atmosphere would surely have the technology to do something MUCH better if they wanted to fly around in Saturn's atmosphere, so what is the point of your game?

hmmmm regarding the point, it comes from curiosity more so than anything else. Regarding the technology, I think I would respectfully disagree that prop planes would have no place in a future that had more advanced technology. Prop planes have seen their glory days, but you still see them being flown now. Its more of a question of human nature, i guess? To see if it can work might be as valid as to know what solution is most optimal? I mean, we still want to climb everest on foot... if optimization was the only point of human endeavors, why not just take a VTOL or helli?

PS. The setting of the game is Saturn, and ive always loved prop planes, so ive been thinking about using them as vehicles on Saturn; its less hard science fiction than say the Expanse but id still like to examine the idea as thoroughly as i can :)

 

[phinds]

disregarding the challenges of putting it in Saturn atmo in the first place

Uh huh.

 

[GypsyOfTheSatOfLove]

Uh huh.

Hmm just for clarity, i assumed the craft would be assembled in orbit and brought to Saturn, i dont think thats completely unrealistic even by what we can achieve today. Its more a question of cost, which im removing as a constraint since, as you have recognized, anyone attempting this is assumed to have that technology... its fair tho i think to clarify that this is a theoretical based on current or probable technology ... in the end i just think its fun to think about it :) you dont have to agree tho

 

[Flyboy]

The issue isn't getting it into orbit, per se. It's surviving the atmospheric entry at Saturn. It's not as bad as Jupiter, but it's still going to be well into the tens of kilometers per second at atmospheric interface. Inflatable/deployable heatshields are going to struggle with those loads, imo.

 

[GypsyOfTheSatOfLove]

The issue isn't getting it into orbit, per se. It's surviving the atmospheric entry at Saturn. It's not as bad as Jupiter, but it's still going to be well into the tens of kilometers per second at atmospheric interface. Inflatable/deployable heatshields are going to struggle with those loads, imo.

If delta v wasnt a problem, like we had an excess of delta v at re entry, could we manage to slow down a more significant load without having to rely on heat shielding as much?

Or would a concept like a space hook help in these situations?
EDIT: or perhaps two orbital rings, one dipping into the cloud layer while one maintains the orbit. These might be made of super conducting cables, as per Isaac Arthur, and can maybe expedite the process of going in and out of Saturn (tho the cost would be mind bogglingly astronomical)

 

[Hornbein]

Saturnian Atmosphere​

Surface Pressure: >>1000 bars
Temperature at 1 bar: 134 K (-139 C)
Temperature at 0.1 bar: 84 K (-189 C)
Density at 1 bar: 0.19 kg/m3
Wind speeds
Up to 400 m/s (<30 degrees latitude)
Up to 150 m/s (>30 degrees latitude)
Scale height: 59.5 km
Mean molecular weight: 2.07
Atmospheric composition (by volume, uncertainty in parentheses)
Major: Molecular hydrogen (H2) - 96.3% (2.4%); Helium (He) - 3.25% (2.4%)
Minor (ppm): Methane (CH4) - 4500 (2000); Ammonia
(NH3) - 125 (75);
Hydrogen Deuteride (HD) - 110 (58); Ethane
(C2H6) - 7 (1.5)
Aerosols: Ammonia ice, water ice, ammonia hydrosulfide

>>1000 bars! The surface pressure on Earth is 1 bar. It seems to me you can get any atmospheric pressure you like, depending on the altitude.

Superconductivity wouldn't make much difference. Ordinary copper is conductive enough to be efficient. Superconductivity means a marginal gain. They use it in the Supercollider because of the enormous peak loads, which would melt an ordinary electromagnet (or so I believe).

Burning hydrogen releases a lot of energy. Too bad that oxygen is the heavier component, so it isn't nearly as weight efficient of a fuel as canned hydrogen here on Earth with its free oxygen. Liquid oxygen has a boiling point of –297°F (–183°C). Dang.

According to the "hairy ball theorem", there must be at least two spots on Saturn that have no wind. This is true at all altitudes. These spots will move around, but presumably the airplane can keep inside the quiet zone.

All in all it seems doable. Quite an original idea too, a rare thing in SF.

 

[GypsyOfTheSatOfLove]

All in all it seems doable. Quite an original idea too, a rare thing in SF.

Many thanks for the insights and kind words tho i dont think its that original. Floating Worlds by Cecilia Holland came out in 1976 and its got similar ideas and others like Robert L. Forward's Saturn Rukh have expounded on the idea of flight in Saturn (albeit on the alien Rukhs)

 

[Vanadium 50]

Let me make sure I understand. Building space hooks and orbital rings a billion miles out is no problem - but you're worried about a propeller?

 

[GypsyOfTheSatOfLove]

Let me make sure I understand. Building space hooks and orbital rings a billion miles out is no problem - but you're worried about a propeller?

Yep... again, its not about what is optimal, but what makes me happy :) like flying a glider in the age of jets

Also, i did some testing in Kerbal Space Program (the most scientifically accurate program) and you could get a 13 to 20 ton airplane to Jool, a close analog to saturn, and use a sort of orbital braking station/ship. You dock on the orbital brake, it gets you to around earth orbital speed, you uncouple, the brake accelerates back to orbit, and the plane can now survive on its basic heat shielding... no space hooks or rings necessary

Edit: also, arent skyhooks and orbital rings conceptually more realistic than say an engine that can sustain 1G of acceleration for days or a space elevator? theyre relatively low tech but do cost a ton... but what is cost really but a measure of societal prioritization; its not hard to imagine a future where this is the one and only priority

 

[Drakkith]

Also, i did some testing in Kerbal Space Program (the most scientifically accurate program) and you could get a 13 to 20 ton airplane to Jool, a close analog to saturn, and use a sort of orbital braking station/ship. You dock on the orbital brake, it gets you to around earth orbital speed, you uncouple, the brake accelerates back to orbit, and the plane can now survive on its basic heat shielding... no space hooks or rings necessary

If you're just using the stock solar system in KSP, then you cannot trust any of those numbers. Install the Real Scale Solar System mod (and all the other mods to get realistic engines, fuels, etc) and see what you can do then. Note that the Cassini spacecraft that visited Saturn had a launch mass of 5700 kg, or just over 5 metric tons. Getting just double that mass to Saturn would require a MUCH larger launch vehicle and upper stage than the Titan IV-Centaur that launched Cassini.

In any case, I see nothing wrong with wanting a plane on Saturn. It is entirely within the realm of current technology, it's just not going to happen in real life without a really, REALLY good reason to do so. One thing you might want to consider if you care about realism is to scale your vehicle back from a plane to a lightweight UAV or drone. An RTG might be able to power a very small, lightweight drone for many years. The Cassini spacecraft had three RTG's that provided between 650-800 watts with a total weight of about 150 kg just to give you some idea of what you're working with.

But it's your game, so you can do anything you want. If you want a plane on Saturn, just put a plane on Saturn!!

 

[GypsyOfTheSatOfLove]

But it's your game, so you can do anything you want. If you want a plane on Saturn, just put a plane on Saturn!!

Thanks for the insights! Will try the mods for KSP :) In stock KSP, i get around the launch weight limitations usually by assembling the craft in orbit. In trips to Jool, i have a craft that never leaves space, and gets refueled in kerbin orbit. For the orbital brake, ive tried using higher ISP engines to brake, since the height of Joolian atmo allows you some time before you hit the thicker atmo, then use a higher thrust engine to get back to orbit (just to save on fuel)

Defo will put the planes in Saturn hehe. This discussion was ideally more for the fleshing out of the idea, like how to go about it based on real world concepts and tech. Even tho thats all background, it informs my ship design and world building (to an extent, rule of cool probably will trump in the end :p)

 

[Drakkith]

Will try the mods for KSP :)

I HIGHLY recommend downloading CKAN to install any KSP mods. It makes it a breeze.