Planets That Could Not Exist

[Spacescifi]

Winged humanoids are popular in scifi, but due to the square cube principle (weight increases faster than strength), it's a nonstarter.

 

I have seen people say... but what if their world is lower gravity with a thick atmosphere?

 

A few challenges there that I am not sure can be overcome.

1. The moon Titan is such a place, yet I have read that the reason it's dense gases do not boil off and evaporate into space is because it is so far away from the sun. So sure, people could fly there... and get frost bite in minutes or less... even if air was breathable there.

2. Moving a Titan-like world closer to the sun to improve the frigid temperatures I have read would make the gases evaporate away into vacuum, since the gravity of Titan is rather low anyway. I do not know if this is true, but I suspect it is, since our moon is larger than Titan and is not holding an atmosphere, likely because it could'nt, unless the gases in question were the heaviest you could find so they would hold more readily to the surface 

 

 

That's one planet type. Anymore you got? Or wanna discuss.

 

[Scotius]

Low gravity + thick atmosphere = non-breathable air. For humanoids at least.

Secondly: humanoid bodies are not built for flight. We're not aerodynamic enough. We have dense, heavy bones without air sacks. Our respiratory systems are unable to provide enough oxygen for active flight. Even our skulls are placed on top of the spine in a way, that makes flying very uncomfortable after a while.

Maybe, maybe one day genetic engineering will make necessary modifications possible - but IMO product of such changes would hardly be a humanoid.

You want humans flying under their own power? Build a huge pressurized dome on the Moon, or another low gravity world

[kerbiloid]

14 minutes ago, Scotius said:

You want humans flying under their own power? Build a huge pressurized dome on the Moon

Like Heinlein described.

[Spacescifi]

18 minutes ago, Scotius said:

Low gravity + thick atmosphere = non-breathable air. For humanoids at least.

Secondly: humanoid bodies are not built for flight. We're not aerodynamic enough. We have dense, heavy bones without air sacks. Our respiratory systems are unable to provide enough oxygen for active flight. Even our skulls are placed on top of the spine in a way, that makes flying very uncomfortable after a while.

Maybe, maybe one day genetic engineering will make necessary modifications possible - but IMO product of such changes would hardly be a humanoid.

You want humans flying under their own power? Build a huge pressurized dome on the Moon, or another low gravity world

 

I don't. I used to think it was cool years ago before I looked into the physics of it,and concluded it was impractical to impossible with regard to conformity to scientific understanding.

 

By the way.. a 3g or 4g Earth creature would be well suiited for being stout... with wheels instead of legs.

Not like anythimg you've ever seen in biology, but desperate times call for desperate measures.

Distance to 4g fall hitting the ground is less, so it's a win-win design.

[Scotius]

You just need to solve engineering problems of having biological wheels as parts of a living organism...

1 billion years of organic evolution wasn't enough on Earth.

Those guys, though...

 

[magnemoe]

4 hours ago, Scotius said:

Low gravity + thick atmosphere = non-breathable air. For humanoids at least.

Secondly: humanoid bodies are not built for flight. We're not aerodynamic enough. We have dense, heavy bones without air sacks. Our respiratory systems are unable to provide enough oxygen for active flight. Even our skulls are placed on top of the spine in a way, that makes flying very uncomfortable after a while.

Maybe, maybe one day genetic engineering will make necessary modifications possible - but IMO product of such changes would hardly be a humanoid.

You want humans flying under their own power? Build a huge pressurized dome on the Moon, or another low gravity world

Are thick atmosphere an problem? 3 bar is the same as you get diving to 30 meters. Yes very thick like 50 bar would be a problem. 
the extra oxygen also make flying easier. 
You could also use an smaller planet reducing gravity to 50-60% its still enough gravity to keep the atmosphere, titan is to small if you raise the temperature to earth level. 

Agree on the body plan. You would want 6 limbs to give you arms and wings and you want lightweight bird style bones, also weaker rear limbs as you don't need the very heavy human legs. 

[Spacescifi]

3 minutes ago, Scotius said:

You just need to solve engineering problems of having biological wheels as parts of a living organism...

1 billion years of organic evolution wasn't enough on Earth.

Those guys, though...

 

 

Actually I don't. My scifi  universe...so my design.

Cosmic accidents are without purpose or design.

A created scifi universe is neither, as it has a clear purpose and design.

I just design what I want and go from there. 

[magnemoe]

18 minutes ago, Scotius said:

You just need to solve engineering problems of having biological wheels as parts of a living organism...

1 billion years of organic evolution wasn't enough on Earth.

Have no idea how to make wheels work with biology, how to pass blood and nerve signals to an continuous rotating join. 
Second problem is that wheels works best if you are large I think, you want the wheel to be large enough for you to keep an good speed. 

[sh1pman]

5 hours ago, Spacescifi said:

2. Moving a Titan-like world closer to the sun to improve the frigid temperatures I have read would make the gases evaporate away into vacuum

All you need to counter this is a strong magnetosphere. But a moon is unlikely to have it, so it must be orbiting close enough to its parent gas giant that has magnetosphere. Preferably not inside a radiation belt, but thick atmosphere can help with that. 

[Spacescifi]

12 minutes ago, magnemoe said:

Have no idea how to make wheels work with biology, how to pass blood and nerve signals to an continuous rotating join. 
Second problem is that wheels works best if you are large I think, you want the wheel to be large enough for you to keep an good speed. 

 

Through the axle.

 

Or we may not even have to use blood? Maybe it's an inflatable bladder like a tire?

Maybe it's about the size of a motorcycle with two wheels?

 

The body plan itself would be Soft ans squishy spheres joined together with necesary arms and manipulative digits.

Since soft squishy sphere bodies can take a 4g fall easier than a 5ft tall upright human ever could.

Edited December 2, 2019 by Spacescifi

[magnemoe]

6 minutes ago, sh1pman said:

All you need to counter this is a strong magnetosphere. But a moon is unlikely to have it, so it must be orbiting close enough to its parent gas giant that has magnetosphere. Preferably not inside a radiation belt, but thick atmosphere can help with that. 

If you have an moon around an heavy planet, the gravity gradient also help holding on to the atmosphere, most of the atmosphere lost would still be in orbit around the planet and can be re-captured, this is true for Titan today. 

Now you could make the gravity gradient as strong as possible
https://steemit.com/space/@busser/the-smoke-ring-habitable-world-without-hard-surface
The problem with this is that an gas giant is mostly hydrogen and helium. You would need something like an super Venus with lots of nitrogen in addition to co2, 

 

[Spacescifi]

12 minutes ago, sh1pman said:

All you need to counter this is a strong magnetosphere. But a moon is unlikely to have it, so it must be orbiting close enough to its parent gas giant that has magnetosphere. Preferably not inside a radiation belt, but thick atmosphere can help with that. 

 

Why could'nt a moon have it's own magnetic field? Does'nt it only need rotation with a molten iron core to generate a magbetic field? Or does mass really make a difference, so that only planets can do that? Unless you got some weird moon made out of neodynium ore (would be fun times trying to land a spacecraft there though).

[Shpaget]

53 minutes ago, magnemoe said:

Are thick atmosphere an problem? 3 bar is the same as you get diving to 30 meters. Yes very thick like 50 bar would be a problem. 
the extra oxygen also make flying easier. 

You have to be careful regarding partial pressure of oxygen. At around 0,5 bar it starts to become toxic.

[farmerben]

7 hours ago, Spacescifi said:

 

Winged humanoids are popular in scifi, but due to the square cube principle (weight increases faster than strength), it's a nonstarter.

 

 

Ok, lets say strength varies by cross sectional area, and mass increases with volume.  The Andean Condor is about 30 lbs, but that is not an unbreakable limit.

We have long legs and strong feet.  The leg muscle system is rated for 3-6 times body weight, and the skeleton is rated for 6-10 times body weight.  Wing skeletons could be rated for 1.5 times body weight since they don't impact the ground.

These guys have ridiculously strong shoulders, chest, and back.  But their forearms, are not as much dis-proportioned to a normal athlete.  Anybody who can do the Iron Cross can do 100 pull-ups with ease.  The thing humans are most lacking compared to birds is dorsal leverage.

 

[wumpus]

2 hours ago, Shpaget said:

You have to be careful regarding partial pressure of oxygen. At around 0,5 bar it starts to become toxic.

Toxic and likely explosive.

Plus, low gravity planets would "quickly" (at least by geological time) lose their atmosphere.  The atmosphere would have to be brought by settlers and not expected to last (I'd assume mass nuclear alchemy creation of oxygen).

7 hours ago, kerbiloid said:

Like Heinlein described.

Pretty much the only way you will get winged humans.  And menances from Earth.

[kerbiloid]

Not exactly a question, but a thinking.

Say, we have a classic O'Neil cylinder. Say, it's ground level is at 200 m from axis, so everything is OK there with rural idyll,  golf fields, and lovely suburban houses.

Say, there is a basejumping tower from the ground to the rotation axis (or a truss across the diameter used for that).

A parachutist (a wingist? a surf-wingist?) climbs to the rotation axis and slowly makes a step from it.

As he is now in zero-near-G, he is probably floating next to the axis of the cylinder.
He can wave with wings and probably travel along the cylinder.

Now he starts flying radially, to the ground.
As he doesn't contact with anything, and the air density is relatively low, he is probably keeping drifting at near-zero total speed.
Shouldn't he face the ground at the rotation linear speed equal to sqrt(9.81 * 200) = 44 m/s = 158 km/h?

Shouldn't any tool, dropped by a worker from there, breach a cottage wall?

***

Now imagine the famous ten-kilometer-sized cylindric colony.
Say, it's ground radius is 1 km.
Then the speed would be about 100 m/s.

***

What if drop a dense rubber ball, bouncing many times from the walls and ground?

***

The safest case. What if pour a liquid.

Edited December 2, 2019 by kerbiloid

[magnemoe]

3 hours ago, Shpaget said:

You have to be careful regarding partial pressure of oxygen. At around 0,5 bar it starts to become toxic.

Oxygen level is not an issue then diving, nitrogen become an problem going deep but 3 bar would not be an issue. 

[Terwin]

3 hours ago, Spacescifi said:

Or we may not even have to use blood? Maybe it's an inflatable bladder like a tire?

How do you keep it connected and inflated?  replace it every time it hits a thorn?  How do you speed up or slow down?

3 hours ago, Spacescifi said:

Maybe it's about the size of a motorcycle with two wheels?

 

The body plan itself would be Soft ans squishy spheres joined together with necesary arms and manipulative digits.

Since soft squishy sphere bodies can take a 4g fall easier than a 5ft tall upright human ever could.

Rolling only works on relatively smooth surfaces.

Even 'flat' grasslands tend to have ruts, holes, rocks and other obstacles unless you have someone removing them.

Modern farms, road ways, trails, etc are artificial constructs where wheels work well, but if not maintained, they quickly be come unusable to wheeled vehicles.

There is a spider that lives in the desert that 'rolls' down the dunes to escape predators: https://en.wikipedia.org/wiki/Wheel_spider

But they do not use this as a primary means of locomotion and only as an escape mechanism.

 

This page has a full discussion of wheels and wheel-like structures in organisms.

https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems

Apparently some bacteria have solved the issue of free-rotation for their flagellum, but it does not look like anything more complex has managed it.

 

[Shpaget]

37 minutes ago, magnemoe said:

Oxygen level is not an issue then diving, nitrogen become an problem going deep but 3 bar would not be an issue. 

It most certainly is.

http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/6310/SPUMS_V26N3_13.pdf?sequence=1

TABLE 1 NOAA OXYGEN LIMITS FOR SINGLE EXPOSURES

PO2 Time

0.6 bar 720 minutes
0.7 bar 570 minutes
0.8 bar 450 minutes
0.9 bar 360 minutes
1.0 bar 300 minutes
1.1 bar 240 minutes
1.2 bar 210 minutes
1.3 bar 180 minutes
1.4 bar 150 minutes
1.5 bar 120 minutes
1.6 bar 45 minutes

Even at the depth of 20 m (3 bar total pressure, 0.6 bar partial oxygen pressure) you are already in the region of toxicity for prolonged exposure.

[Terwin]

33 minutes ago, Shpaget said:

It most certainly is.

http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/6310/SPUMS_V26N3_13.pdf?sequence=1

TABLE 1 NOAA OXYGEN LIMITS FOR SINGLE EXPOSURES

PO2 Time

0.6 bar 720 minutes
0.7 bar 570 minutes
0.8 bar 450 minutes
0.9 bar 360 minutes
1.0 bar 300 minutes

Even at the depth of 20 m (3 bar total pressure, 0.6 bar partial oxygen pressure) you are already in the region of toxicity for prolonged exposure.

Recreational scuba diving does not generally worry about oxygen toxicity unless using an enriched oxygen air source(nitrox).

Spending a full 60 minutes submerged on one 80cuft tank is generally only possible when staying less than ~5m deep, so the feasibility of spending 12 times as long at a depth where you use up your air three times as fast is  highly unlikely(not even counting the time to get down and back up).

The recreational diving limit (112 feet) is at roughly 9.5 bar partial pressure, and it is uncommon to spend even 10-15 min at this depth where the exposure limit is more than 5 hours(and you are using up your air at ~4.5 times the shallow rate).

Nitrogen narcosis(nitrogen under enough pressure makes you act/feel drunk) however can happen around or below 30m, and this is a much more common danger than staying at depth more than 10x as long as most people can make their air last.  Even shallower divers can get hyperbaric injuries(if you hold your breath when while going from 20m to 10m for example, the air expands to 1.5 times it's previous volume and can 'pop' your lungs like an over-filled balloon, going from 10m to 0m expands the air to double it's volume, making such problems even easier to encounter if you are not careful).

These are the sorts of issues compressed-air recreational divers are more likely to encounter, so those are the issues they focus on in the training.

 

 

Edited December 2, 2019 by Terwin

[magnemoe]

1 minute ago, Terwin said:

Recreational scuba diving does not generally worry about oxygen toxicity unless using an enriched oxygen air source(nitrox).

Spending a full 60 minutes submerged on one 80cuft tank is generally only possible when staying less than ~5m deep, so the feasibility of spending 12 times as long at a depth where you use up your air three times as fast is  highly unlikely(not even counting the time to get down and back up).

The recreational diving limit (112 feet) is at roughly 9.5 bar partial pressure, and it is uncommon to spend even 10-15 min at this depth where the exposure limit is more than 5 hours(and you are using up your air at ~4.5 times the shallow rate).

Nitrogen narcosis(nitrogen under enough pressure makes you act/feel drunk) however can happen around or below 30m, and this is a much more common danger than staying at depth more than 10x as long as most people can make their air last.  Even shallower divers can get hyperbaric injuries(if you hold your breath when while going from 20m to 10m for example, the air expands to 1.5 times it's previous volume and can 'pop' your lungs like an over-filled balloon, going from 10m to 0m expands the air to double it's volume, making such problems even easier to encounter if you are not careful).

These are the sorts of issues compressed-air recreational divers are more likely to encounter, so those are the issues they focus on in the training.

 

You are right, i had my experience from scuba training. 
In conclusion you don't want the partial pressure of oxygen too high. 

[wumpus]

1 hour ago, kerbiloid said:

Not exactly a question, but a thinking.

Say, we have a classic O'Neil cylinder. Say, it's ground level is at 200 m from axis, so everything is OK there with rural idyll,  golf fields, and lovely suburban houses.

Say, there is a basejumping tower from the ground to the rotation axis (or a truss across the diameter used for that).

A parachutist (a wingist? a surf-wingist?) climbs to the rotation axis and slowly makes a step from it.

As he is now in zero-near-G, he is probably floating next to the axis of the cylinder.
He can wave with wings and probably travel along the cylinder.

Now he starts flying radially, to the ground.
As he doesn't contact with anything, and the air density is relatively low, he is probably keeping drifting at near-zero total speed.
Shouldn't he face the ground at the rotation linear speed equal to sqrt(9.81 * 200) = 44 m/s = 158 km/h?

Shouldn't any tool, dropped by a worker from there, breach a cottage wall?

***

Now imagine the famous ten-kilometer-sized cylindric colony.
Say, it's ground radius is 1 km.
Then the speed would be about 100 m/s.

***

What if drop a dense rubber ball, bouncing many times from the walls and ground?

***

The safest case. What if pour a liquid.

Same as on Earth, the air would follow the ground, with a certain small amount of "constant wind" counter to rotation.  So anything dropped would be slowly grabbed by the wind as it got closer and closer to "ground".  No idea if anyone has determined how to deal with such airflow in an O'Neil cylinder (they were talking about them long before computer simulations were feasible).  I suspect that width and baffles would be key to such construction.

[kerbiloid]

24 minutes ago, wumpus said:

Same as on Earth, the air would follow the ground, with a certain small amount of "constant wind" counter to rotation.  So anything dropped would be slowly grabbed by the wind as it got closer and closer to "ground".

The thing is that in O'Neil cylinder the difference between the wind and the rotation speed differs faster than on the Earth (there is no 44 m/s per 200 m gradient here, usually).
So, a tool dropped/thrown from the axial truss should hit something at a car speed.

And unlike on the Earth, it can flow in absolutely any direction, not fall right below.

Edited December 2, 2019 by kerbiloid

[magnemoe]

34 minutes ago, kerbiloid said:

The thing is that in O'Neil cylinder the difference between the wind and the rotation speed differs faster than on the Earth (there is no 44 m/s per 200 m gradient here, usually).
So, a tool dropped/thrown from the axial truss should hit something at a car speed.

And unlike on the Earth, it can flow in absolutely any direction, not fall right below.

My guess is that air will rotate with the cylinder so speed will go toward zero at center, air probably moves a bit slower near the center too. 
However if you get off the center the wind will start pushing you in the wind direction and away from the center, now for something like an human who is heavy and has pretty low drag you are likely to hit the ground pretty slow but ground would still moves fast so an stunt there you land with on rollebladers might work. Now keeping you balance at highway speeds on rollerblades wearing an wingsuit might be challenging

Something with high drag to mass ration would fall more natural. 

[Shpaget]

1 hour ago, Terwin said:

Recreational scuba diving...

You're forgetting that we're not talking about recreational scuba diving, or even professional technical diving. We're talking about living in a high pressure oxygen rich atmosphere.